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@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1996, 1998, 1999, 2000,
2
@c 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
3
 
4
@c This is part of the GCC manual.
5
@c For copying conditions, see the file gcc.texi.
6
 
7
@node C Extensions
8
@chapter Extensions to the C Language Family
9
@cindex extensions, C language
10
@cindex C language extensions
11
 
12
@opindex pedantic
13
GNU C provides several language features not found in ISO standard C@.
14
(The @option{-pedantic} option directs GCC to print a warning message if
15
any of these features is used.)  To test for the availability of these
16
features in conditional compilation, check for a predefined macro
17
@code{__GNUC__}, which is always defined under GCC@.
18
 
19
These extensions are available in C and Objective-C@.  Most of them are
20
also available in C++.  @xref{C++ Extensions,,Extensions to the
21
C++ Language}, for extensions that apply @emph{only} to C++.
22
 
23
Some features that are in ISO C99 but not C89 or C++ are also, as
24
extensions, accepted by GCC in C89 mode and in C++.
25
 
26
@menu
27
* Statement Exprs::     Putting statements and declarations inside expressions.
28
* Local Labels::        Labels local to a block.
29
* Labels as Values::    Getting pointers to labels, and computed gotos.
30
* Nested Functions::    As in Algol and Pascal, lexical scoping of functions.
31
* Constructing Calls::  Dispatching a call to another function.
32
* Typeof::              @code{typeof}: referring to the type of an expression.
33
* Conditionals::        Omitting the middle operand of a @samp{?:} expression.
34
* Long Long::           Double-word integers---@code{long long int}.
35
* Complex::             Data types for complex numbers.
36
* Decimal Float::       Decimal Floating Types.
37
* Hex Floats::          Hexadecimal floating-point constants.
38
* Zero Length::         Zero-length arrays.
39
* Variable Length::     Arrays whose length is computed at run time.
40
* Empty Structures::    Structures with no members.
41
* Variadic Macros::     Macros with a variable number of arguments.
42
* Escaped Newlines::    Slightly looser rules for escaped newlines.
43
* Subscripting::        Any array can be subscripted, even if not an lvalue.
44
* Pointer Arith::       Arithmetic on @code{void}-pointers and function pointers.
45
* Initializers::        Non-constant initializers.
46
* Compound Literals::   Compound literals give structures, unions
47
                         or arrays as values.
48
* Designated Inits::    Labeling elements of initializers.
49
* Cast to Union::       Casting to union type from any member of the union.
50
* Case Ranges::         `case 1 ... 9' and such.
51
* Mixed Declarations::  Mixing declarations and code.
52
* Function Attributes:: Declaring that functions have no side effects,
53
                         or that they can never return.
54
* Attribute Syntax::    Formal syntax for attributes.
55
* Function Prototypes:: Prototype declarations and old-style definitions.
56
* C++ Comments::        C++ comments are recognized.
57
* Dollar Signs::        Dollar sign is allowed in identifiers.
58
* Character Escapes::   @samp{\e} stands for the character @key{ESC}.
59
* Variable Attributes:: Specifying attributes of variables.
60
* Type Attributes::     Specifying attributes of types.
61
* Alignment::           Inquiring about the alignment of a type or variable.
62
* Inline::              Defining inline functions (as fast as macros).
63
* Extended Asm::        Assembler instructions with C expressions as operands.
64
                         (With them you can define ``built-in'' functions.)
65
* Constraints::         Constraints for asm operands
66
* Asm Labels::          Specifying the assembler name to use for a C symbol.
67
* Explicit Reg Vars::   Defining variables residing in specified registers.
68
* Alternate Keywords::  @code{__const__}, @code{__asm__}, etc., for header files.
69
* Incomplete Enums::    @code{enum foo;}, with details to follow.
70
* Function Names::      Printable strings which are the name of the current
71
                         function.
72
* Return Address::      Getting the return or frame address of a function.
73
* Vector Extensions::   Using vector instructions through built-in functions.
74
* Offsetof::            Special syntax for implementing @code{offsetof}.
75
* Atomic Builtins::     Built-in functions for atomic memory access.
76
* Object Size Checking:: Built-in functions for limited buffer overflow
77
                        checking.
78
* Other Builtins::      Other built-in functions.
79
* Target Builtins::     Built-in functions specific to particular targets.
80
* Target Format Checks:: Format checks specific to particular targets.
81
* Pragmas::             Pragmas accepted by GCC.
82
* Unnamed Fields::      Unnamed struct/union fields within structs/unions.
83
* Thread-Local::        Per-thread variables.
84
@end menu
85
 
86
@node Statement Exprs
87
@section Statements and Declarations in Expressions
88
@cindex statements inside expressions
89
@cindex declarations inside expressions
90
@cindex expressions containing statements
91
@cindex macros, statements in expressions
92
 
93
@c the above section title wrapped and causes an underfull hbox.. i
94
@c changed it from "within" to "in". --mew 4feb93
95
A compound statement enclosed in parentheses may appear as an expression
96
in GNU C@.  This allows you to use loops, switches, and local variables
97
within an expression.
98
 
99
Recall that a compound statement is a sequence of statements surrounded
100
by braces; in this construct, parentheses go around the braces.  For
101
example:
102
 
103
@smallexample
104
(@{ int y = foo (); int z;
105
   if (y > 0) z = y;
106
   else z = - y;
107
   z; @})
108
@end smallexample
109
 
110
@noindent
111
is a valid (though slightly more complex than necessary) expression
112
for the absolute value of @code{foo ()}.
113
 
114
The last thing in the compound statement should be an expression
115
followed by a semicolon; the value of this subexpression serves as the
116
value of the entire construct.  (If you use some other kind of statement
117
last within the braces, the construct has type @code{void}, and thus
118
effectively no value.)
119
 
120
This feature is especially useful in making macro definitions ``safe'' (so
121
that they evaluate each operand exactly once).  For example, the
122
``maximum'' function is commonly defined as a macro in standard C as
123
follows:
124
 
125
@smallexample
126
#define max(a,b) ((a) > (b) ? (a) : (b))
127
@end smallexample
128
 
129
@noindent
130
@cindex side effects, macro argument
131
But this definition computes either @var{a} or @var{b} twice, with bad
132
results if the operand has side effects.  In GNU C, if you know the
133
type of the operands (here taken as @code{int}), you can define
134
the macro safely as follows:
135
 
136
@smallexample
137
#define maxint(a,b) \
138
  (@{int _a = (a), _b = (b); _a > _b ? _a : _b; @})
139
@end smallexample
140
 
141
Embedded statements are not allowed in constant expressions, such as
142
the value of an enumeration constant, the width of a bit-field, or
143
the initial value of a static variable.
144
 
145
If you don't know the type of the operand, you can still do this, but you
146
must use @code{typeof} (@pxref{Typeof}).
147
 
148
In G++, the result value of a statement expression undergoes array and
149
function pointer decay, and is returned by value to the enclosing
150
expression.  For instance, if @code{A} is a class, then
151
 
152
@smallexample
153
        A a;
154
 
155
        (@{a;@}).Foo ()
156
@end smallexample
157
 
158
@noindent
159
will construct a temporary @code{A} object to hold the result of the
160
statement expression, and that will be used to invoke @code{Foo}.
161
Therefore the @code{this} pointer observed by @code{Foo} will not be the
162
address of @code{a}.
163
 
164
Any temporaries created within a statement within a statement expression
165
will be destroyed at the statement's end.  This makes statement
166
expressions inside macros slightly different from function calls.  In
167
the latter case temporaries introduced during argument evaluation will
168
be destroyed at the end of the statement that includes the function
169
call.  In the statement expression case they will be destroyed during
170
the statement expression.  For instance,
171
 
172
@smallexample
173
#define macro(a)  (@{__typeof__(a) b = (a); b + 3; @})
174
template<typename T> T function(T a) @{ T b = a; return b + 3; @}
175
 
176
void foo ()
177
@{
178
  macro (X ());
179
  function (X ());
180
@}
181
@end smallexample
182
 
183
@noindent
184
will have different places where temporaries are destroyed.  For the
185
@code{macro} case, the temporary @code{X} will be destroyed just after
186
the initialization of @code{b}.  In the @code{function} case that
187
temporary will be destroyed when the function returns.
188
 
189
These considerations mean that it is probably a bad idea to use
190
statement-expressions of this form in header files that are designed to
191
work with C++.  (Note that some versions of the GNU C Library contained
192
header files using statement-expression that lead to precisely this
193
bug.)
194
 
195
Jumping into a statement expression with @code{goto} or using a
196
@code{switch} statement outside the statement expression with a
197
@code{case} or @code{default} label inside the statement expression is
198
not permitted.  Jumping into a statement expression with a computed
199
@code{goto} (@pxref{Labels as Values}) yields undefined behavior.
200
Jumping out of a statement expression is permitted, but if the
201
statement expression is part of a larger expression then it is
202
unspecified which other subexpressions of that expression have been
203
evaluated except where the language definition requires certain
204
subexpressions to be evaluated before or after the statement
205
expression.  In any case, as with a function call the evaluation of a
206
statement expression is not interleaved with the evaluation of other
207
parts of the containing expression.  For example,
208
 
209
@smallexample
210
  foo (), ((@{ bar1 (); goto a; 0; @}) + bar2 ()), baz();
211
@end smallexample
212
 
213
@noindent
214
will call @code{foo} and @code{bar1} and will not call @code{baz} but
215
may or may not call @code{bar2}.  If @code{bar2} is called, it will be
216
called after @code{foo} and before @code{bar1}
217
 
218
@node Local Labels
219
@section Locally Declared Labels
220
@cindex local labels
221
@cindex macros, local labels
222
 
223
GCC allows you to declare @dfn{local labels} in any nested block
224
scope.  A local label is just like an ordinary label, but you can
225
only reference it (with a @code{goto} statement, or by taking its
226
address) within the block in which it was declared.
227
 
228
A local label declaration looks like this:
229
 
230
@smallexample
231
__label__ @var{label};
232
@end smallexample
233
 
234
@noindent
235
or
236
 
237
@smallexample
238
__label__ @var{label1}, @var{label2}, /* @r{@dots{}} */;
239
@end smallexample
240
 
241
Local label declarations must come at the beginning of the block,
242
before any ordinary declarations or statements.
243
 
244
The label declaration defines the label @emph{name}, but does not define
245
the label itself.  You must do this in the usual way, with
246
@code{@var{label}:}, within the statements of the statement expression.
247
 
248
The local label feature is useful for complex macros.  If a macro
249
contains nested loops, a @code{goto} can be useful for breaking out of
250
them.  However, an ordinary label whose scope is the whole function
251
cannot be used: if the macro can be expanded several times in one
252
function, the label will be multiply defined in that function.  A
253
local label avoids this problem.  For example:
254
 
255
@smallexample
256
#define SEARCH(value, array, target)              \
257
do @{                                              \
258
  __label__ found;                                \
259
  typeof (target) _SEARCH_target = (target);      \
260
  typeof (*(array)) *_SEARCH_array = (array);     \
261
  int i, j;                                       \
262
  int value;                                      \
263
  for (i = 0; i < max; i++)                       \
264
    for (j = 0; j < max; j++)                     \
265
      if (_SEARCH_array[i][j] == _SEARCH_target)  \
266
        @{ (value) = i; goto found; @}              \
267
  (value) = -1;                                   \
268
 found:;                                          \
269
@} while (0)
270
@end smallexample
271
 
272
This could also be written using a statement-expression:
273
 
274
@smallexample
275
#define SEARCH(array, target)                     \
276
(@{                                                \
277
  __label__ found;                                \
278
  typeof (target) _SEARCH_target = (target);      \
279
  typeof (*(array)) *_SEARCH_array = (array);     \
280
  int i, j;                                       \
281
  int value;                                      \
282
  for (i = 0; i < max; i++)                       \
283
    for (j = 0; j < max; j++)                     \
284
      if (_SEARCH_array[i][j] == _SEARCH_target)  \
285
        @{ value = i; goto found; @}                \
286
  value = -1;                                     \
287
 found:                                           \
288
  value;                                          \
289
@})
290
@end smallexample
291
 
292
Local label declarations also make the labels they declare visible to
293
nested functions, if there are any.  @xref{Nested Functions}, for details.
294
 
295
@node Labels as Values
296
@section Labels as Values
297
@cindex labels as values
298
@cindex computed gotos
299
@cindex goto with computed label
300
@cindex address of a label
301
 
302
You can get the address of a label defined in the current function
303
(or a containing function) with the unary operator @samp{&&}.  The
304
value has type @code{void *}.  This value is a constant and can be used
305
wherever a constant of that type is valid.  For example:
306
 
307
@smallexample
308
void *ptr;
309
/* @r{@dots{}} */
310
ptr = &&foo;
311
@end smallexample
312
 
313
To use these values, you need to be able to jump to one.  This is done
314
with the computed goto statement@footnote{The analogous feature in
315
Fortran is called an assigned goto, but that name seems inappropriate in
316
C, where one can do more than simply store label addresses in label
317
variables.}, @code{goto *@var{exp};}.  For example,
318
 
319
@smallexample
320
goto *ptr;
321
@end smallexample
322
 
323
@noindent
324
Any expression of type @code{void *} is allowed.
325
 
326
One way of using these constants is in initializing a static array that
327
will serve as a jump table:
328
 
329
@smallexample
330
static void *array[] = @{ &&foo, &&bar, &&hack @};
331
@end smallexample
332
 
333
Then you can select a label with indexing, like this:
334
 
335
@smallexample
336
goto *array[i];
337
@end smallexample
338
 
339
@noindent
340
Note that this does not check whether the subscript is in bounds---array
341
indexing in C never does that.
342
 
343
Such an array of label values serves a purpose much like that of the
344
@code{switch} statement.  The @code{switch} statement is cleaner, so
345
use that rather than an array unless the problem does not fit a
346
@code{switch} statement very well.
347
 
348
Another use of label values is in an interpreter for threaded code.
349
The labels within the interpreter function can be stored in the
350
threaded code for super-fast dispatching.
351
 
352
You may not use this mechanism to jump to code in a different function.
353
If you do that, totally unpredictable things will happen.  The best way to
354
avoid this is to store the label address only in automatic variables and
355
never pass it as an argument.
356
 
357
An alternate way to write the above example is
358
 
359
@smallexample
360
static const int array[] = @{ &&foo - &&foo, &&bar - &&foo,
361
                             &&hack - &&foo @};
362
goto *(&&foo + array[i]);
363
@end smallexample
364
 
365
@noindent
366
This is more friendly to code living in shared libraries, as it reduces
367
the number of dynamic relocations that are needed, and by consequence,
368
allows the data to be read-only.
369
 
370
@node Nested Functions
371
@section Nested Functions
372
@cindex nested functions
373
@cindex downward funargs
374
@cindex thunks
375
 
376
A @dfn{nested function} is a function defined inside another function.
377
(Nested functions are not supported for GNU C++.)  The nested function's
378
name is local to the block where it is defined.  For example, here we
379
define a nested function named @code{square}, and call it twice:
380
 
381
@smallexample
382
@group
383
foo (double a, double b)
384
@{
385
  double square (double z) @{ return z * z; @}
386
 
387
  return square (a) + square (b);
388
@}
389
@end group
390
@end smallexample
391
 
392
The nested function can access all the variables of the containing
393
function that are visible at the point of its definition.  This is
394
called @dfn{lexical scoping}.  For example, here we show a nested
395
function which uses an inherited variable named @code{offset}:
396
 
397
@smallexample
398
@group
399
bar (int *array, int offset, int size)
400
@{
401
  int access (int *array, int index)
402
    @{ return array[index + offset]; @}
403
  int i;
404
  /* @r{@dots{}} */
405
  for (i = 0; i < size; i++)
406
    /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */
407
@}
408
@end group
409
@end smallexample
410
 
411
Nested function definitions are permitted within functions in the places
412
where variable definitions are allowed; that is, in any block, mixed
413
with the other declarations and statements in the block.
414
 
415
It is possible to call the nested function from outside the scope of its
416
name by storing its address or passing the address to another function:
417
 
418
@smallexample
419
hack (int *array, int size)
420
@{
421
  void store (int index, int value)
422
    @{ array[index] = value; @}
423
 
424
  intermediate (store, size);
425
@}
426
@end smallexample
427
 
428
Here, the function @code{intermediate} receives the address of
429
@code{store} as an argument.  If @code{intermediate} calls @code{store},
430
the arguments given to @code{store} are used to store into @code{array}.
431
But this technique works only so long as the containing function
432
(@code{hack}, in this example) does not exit.
433
 
434
If you try to call the nested function through its address after the
435
containing function has exited, all hell will break loose.  If you try
436
to call it after a containing scope level has exited, and if it refers
437
to some of the variables that are no longer in scope, you may be lucky,
438
but it's not wise to take the risk.  If, however, the nested function
439
does not refer to anything that has gone out of scope, you should be
440
safe.
441
 
442
GCC implements taking the address of a nested function using a technique
443
called @dfn{trampolines}.  A paper describing them is available as
444
 
445
@noindent
446
@uref{http://people.debian.org/~aaronl/Usenix88-lexic.pdf}.
447
 
448
A nested function can jump to a label inherited from a containing
449
function, provided the label was explicitly declared in the containing
450
function (@pxref{Local Labels}).  Such a jump returns instantly to the
451
containing function, exiting the nested function which did the
452
@code{goto} and any intermediate functions as well.  Here is an example:
453
 
454
@smallexample
455
@group
456
bar (int *array, int offset, int size)
457
@{
458
  __label__ failure;
459
  int access (int *array, int index)
460
    @{
461
      if (index > size)
462
        goto failure;
463
      return array[index + offset];
464
    @}
465
  int i;
466
  /* @r{@dots{}} */
467
  for (i = 0; i < size; i++)
468
    /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */
469
  /* @r{@dots{}} */
470
  return 0;
471
 
472
 /* @r{Control comes here from @code{access}
473
    if it detects an error.}  */
474
 failure:
475
  return -1;
476
@}
477
@end group
478
@end smallexample
479
 
480
A nested function always has no linkage.  Declaring one with
481
@code{extern} or @code{static} is erroneous.  If you need to declare the nested function
482
before its definition, use @code{auto} (which is otherwise meaningless
483
for function declarations).
484
 
485
@smallexample
486
bar (int *array, int offset, int size)
487
@{
488
  __label__ failure;
489
  auto int access (int *, int);
490
  /* @r{@dots{}} */
491
  int access (int *array, int index)
492
    @{
493
      if (index > size)
494
        goto failure;
495
      return array[index + offset];
496
    @}
497
  /* @r{@dots{}} */
498
@}
499
@end smallexample
500
 
501
@node Constructing Calls
502
@section Constructing Function Calls
503
@cindex constructing calls
504
@cindex forwarding calls
505
 
506
Using the built-in functions described below, you can record
507
the arguments a function received, and call another function
508
with the same arguments, without knowing the number or types
509
of the arguments.
510
 
511
You can also record the return value of that function call,
512
and later return that value, without knowing what data type
513
the function tried to return (as long as your caller expects
514
that data type).
515
 
516
However, these built-in functions may interact badly with some
517
sophisticated features or other extensions of the language.  It
518
is, therefore, not recommended to use them outside very simple
519
functions acting as mere forwarders for their arguments.
520
 
521
@deftypefn {Built-in Function} {void *} __builtin_apply_args ()
522
This built-in function returns a pointer to data
523
describing how to perform a call with the same arguments as were passed
524
to the current function.
525
 
526
The function saves the arg pointer register, structure value address,
527
and all registers that might be used to pass arguments to a function
528
into a block of memory allocated on the stack.  Then it returns the
529
address of that block.
530
@end deftypefn
531
 
532
@deftypefn {Built-in Function} {void *} __builtin_apply (void (*@var{function})(), void *@var{arguments}, size_t @var{size})
533
This built-in function invokes @var{function}
534
with a copy of the parameters described by @var{arguments}
535
and @var{size}.
536
 
537
The value of @var{arguments} should be the value returned by
538
@code{__builtin_apply_args}.  The argument @var{size} specifies the size
539
of the stack argument data, in bytes.
540
 
541
This function returns a pointer to data describing
542
how to return whatever value was returned by @var{function}.  The data
543
is saved in a block of memory allocated on the stack.
544
 
545
It is not always simple to compute the proper value for @var{size}.  The
546
value is used by @code{__builtin_apply} to compute the amount of data
547
that should be pushed on the stack and copied from the incoming argument
548
area.
549
@end deftypefn
550
 
551
@deftypefn {Built-in Function} {void} __builtin_return (void *@var{result})
552
This built-in function returns the value described by @var{result} from
553
the containing function.  You should specify, for @var{result}, a value
554
returned by @code{__builtin_apply}.
555
@end deftypefn
556
 
557
@node Typeof
558
@section Referring to a Type with @code{typeof}
559
@findex typeof
560
@findex sizeof
561
@cindex macros, types of arguments
562
 
563
Another way to refer to the type of an expression is with @code{typeof}.
564
The syntax of using of this keyword looks like @code{sizeof}, but the
565
construct acts semantically like a type name defined with @code{typedef}.
566
 
567
There are two ways of writing the argument to @code{typeof}: with an
568
expression or with a type.  Here is an example with an expression:
569
 
570
@smallexample
571
typeof (x[0](1))
572
@end smallexample
573
 
574
@noindent
575
This assumes that @code{x} is an array of pointers to functions;
576
the type described is that of the values of the functions.
577
 
578
Here is an example with a typename as the argument:
579
 
580
@smallexample
581
typeof (int *)
582
@end smallexample
583
 
584
@noindent
585
Here the type described is that of pointers to @code{int}.
586
 
587
If you are writing a header file that must work when included in ISO C
588
programs, write @code{__typeof__} instead of @code{typeof}.
589
@xref{Alternate Keywords}.
590
 
591
A @code{typeof}-construct can be used anywhere a typedef name could be
592
used.  For example, you can use it in a declaration, in a cast, or inside
593
of @code{sizeof} or @code{typeof}.
594
 
595
@code{typeof} is often useful in conjunction with the
596
statements-within-expressions feature.  Here is how the two together can
597
be used to define a safe ``maximum'' macro that operates on any
598
arithmetic type and evaluates each of its arguments exactly once:
599
 
600
@smallexample
601
#define max(a,b) \
602
  (@{ typeof (a) _a = (a); \
603
      typeof (b) _b = (b); \
604
    _a > _b ? _a : _b; @})
605
@end smallexample
606
 
607
@cindex underscores in variables in macros
608
@cindex @samp{_} in variables in macros
609
@cindex local variables in macros
610
@cindex variables, local, in macros
611
@cindex macros, local variables in
612
 
613
The reason for using names that start with underscores for the local
614
variables is to avoid conflicts with variable names that occur within the
615
expressions that are substituted for @code{a} and @code{b}.  Eventually we
616
hope to design a new form of declaration syntax that allows you to declare
617
variables whose scopes start only after their initializers; this will be a
618
more reliable way to prevent such conflicts.
619
 
620
@noindent
621
Some more examples of the use of @code{typeof}:
622
 
623
@itemize @bullet
624
@item
625
This declares @code{y} with the type of what @code{x} points to.
626
 
627
@smallexample
628
typeof (*x) y;
629
@end smallexample
630
 
631
@item
632
This declares @code{y} as an array of such values.
633
 
634
@smallexample
635
typeof (*x) y[4];
636
@end smallexample
637
 
638
@item
639
This declares @code{y} as an array of pointers to characters:
640
 
641
@smallexample
642
typeof (typeof (char *)[4]) y;
643
@end smallexample
644
 
645
@noindent
646
It is equivalent to the following traditional C declaration:
647
 
648
@smallexample
649
char *y[4];
650
@end smallexample
651
 
652
To see the meaning of the declaration using @code{typeof}, and why it
653
might be a useful way to write, rewrite it with these macros:
654
 
655
@smallexample
656
#define pointer(T)  typeof(T *)
657
#define array(T, N) typeof(T [N])
658
@end smallexample
659
 
660
@noindent
661
Now the declaration can be rewritten this way:
662
 
663
@smallexample
664
array (pointer (char), 4) y;
665
@end smallexample
666
 
667
@noindent
668
Thus, @code{array (pointer (char), 4)} is the type of arrays of 4
669
pointers to @code{char}.
670
@end itemize
671
 
672
@emph{Compatibility Note:} In addition to @code{typeof}, GCC 2 supported
673
a more limited extension which permitted one to write
674
 
675
@smallexample
676
typedef @var{T} = @var{expr};
677
@end smallexample
678
 
679
@noindent
680
with the effect of declaring @var{T} to have the type of the expression
681
@var{expr}.  This extension does not work with GCC 3 (versions between
682
3.0 and 3.2 will crash; 3.2.1 and later give an error).  Code which
683
relies on it should be rewritten to use @code{typeof}:
684
 
685
@smallexample
686
typedef typeof(@var{expr}) @var{T};
687
@end smallexample
688
 
689
@noindent
690
This will work with all versions of GCC@.
691
 
692
@node Conditionals
693
@section Conditionals with Omitted Operands
694
@cindex conditional expressions, extensions
695
@cindex omitted middle-operands
696
@cindex middle-operands, omitted
697
@cindex extensions, @code{?:}
698
@cindex @code{?:} extensions
699
 
700
The middle operand in a conditional expression may be omitted.  Then
701
if the first operand is nonzero, its value is the value of the conditional
702
expression.
703
 
704
Therefore, the expression
705
 
706
@smallexample
707
x ? : y
708
@end smallexample
709
 
710
@noindent
711
has the value of @code{x} if that is nonzero; otherwise, the value of
712
@code{y}.
713
 
714
This example is perfectly equivalent to
715
 
716
@smallexample
717
x ? x : y
718
@end smallexample
719
 
720
@cindex side effect in ?:
721
@cindex ?: side effect
722
@noindent
723
In this simple case, the ability to omit the middle operand is not
724
especially useful.  When it becomes useful is when the first operand does,
725
or may (if it is a macro argument), contain a side effect.  Then repeating
726
the operand in the middle would perform the side effect twice.  Omitting
727
the middle operand uses the value already computed without the undesirable
728
effects of recomputing it.
729
 
730
@node Long Long
731
@section Double-Word Integers
732
@cindex @code{long long} data types
733
@cindex double-word arithmetic
734
@cindex multiprecision arithmetic
735
@cindex @code{LL} integer suffix
736
@cindex @code{ULL} integer suffix
737
 
738
ISO C99 supports data types for integers that are at least 64 bits wide,
739
and as an extension GCC supports them in C89 mode and in C++.
740
Simply write @code{long long int} for a signed integer, or
741
@code{unsigned long long int} for an unsigned integer.  To make an
742
integer constant of type @code{long long int}, add the suffix @samp{LL}
743
to the integer.  To make an integer constant of type @code{unsigned long
744
long int}, add the suffix @samp{ULL} to the integer.
745
 
746
You can use these types in arithmetic like any other integer types.
747
Addition, subtraction, and bitwise boolean operations on these types
748
are open-coded on all types of machines.  Multiplication is open-coded
749
if the machine supports fullword-to-doubleword a widening multiply
750
instruction.  Division and shifts are open-coded only on machines that
751
provide special support.  The operations that are not open-coded use
752
special library routines that come with GCC@.
753
 
754
There may be pitfalls when you use @code{long long} types for function
755
arguments, unless you declare function prototypes.  If a function
756
expects type @code{int} for its argument, and you pass a value of type
757
@code{long long int}, confusion will result because the caller and the
758
subroutine will disagree about the number of bytes for the argument.
759
Likewise, if the function expects @code{long long int} and you pass
760
@code{int}.  The best way to avoid such problems is to use prototypes.
761
 
762
@node Complex
763
@section Complex Numbers
764
@cindex complex numbers
765
@cindex @code{_Complex} keyword
766
@cindex @code{__complex__} keyword
767
 
768
ISO C99 supports complex floating data types, and as an extension GCC
769
supports them in C89 mode and in C++, and supports complex integer data
770
types which are not part of ISO C99.  You can declare complex types
771
using the keyword @code{_Complex}.  As an extension, the older GNU
772
keyword @code{__complex__} is also supported.
773
 
774
For example, @samp{_Complex double x;} declares @code{x} as a
775
variable whose real part and imaginary part are both of type
776
@code{double}.  @samp{_Complex short int y;} declares @code{y} to
777
have real and imaginary parts of type @code{short int}; this is not
778
likely to be useful, but it shows that the set of complex types is
779
complete.
780
 
781
To write a constant with a complex data type, use the suffix @samp{i} or
782
@samp{j} (either one; they are equivalent).  For example, @code{2.5fi}
783
has type @code{_Complex float} and @code{3i} has type
784
@code{_Complex int}.  Such a constant always has a pure imaginary
785
value, but you can form any complex value you like by adding one to a
786
real constant.  This is a GNU extension; if you have an ISO C99
787
conforming C library (such as GNU libc), and want to construct complex
788
constants of floating type, you should include @code{<complex.h>} and
789
use the macros @code{I} or @code{_Complex_I} instead.
790
 
791
@cindex @code{__real__} keyword
792
@cindex @code{__imag__} keyword
793
To extract the real part of a complex-valued expression @var{exp}, write
794
@code{__real__ @var{exp}}.  Likewise, use @code{__imag__} to
795
extract the imaginary part.  This is a GNU extension; for values of
796
floating type, you should use the ISO C99 functions @code{crealf},
797
@code{creal}, @code{creall}, @code{cimagf}, @code{cimag} and
798
@code{cimagl}, declared in @code{<complex.h>} and also provided as
799
built-in functions by GCC@.
800
 
801
@cindex complex conjugation
802
The operator @samp{~} performs complex conjugation when used on a value
803
with a complex type.  This is a GNU extension; for values of
804
floating type, you should use the ISO C99 functions @code{conjf},
805
@code{conj} and @code{conjl}, declared in @code{<complex.h>} and also
806
provided as built-in functions by GCC@.
807
 
808
GCC can allocate complex automatic variables in a noncontiguous
809
fashion; it's even possible for the real part to be in a register while
810
the imaginary part is on the stack (or vice-versa).  Only the DWARF2
811
debug info format can represent this, so use of DWARF2 is recommended.
812
If you are using the stabs debug info format, GCC describes a noncontiguous
813
complex variable as if it were two separate variables of noncomplex type.
814
If the variable's actual name is @code{foo}, the two fictitious
815
variables are named @code{foo$real} and @code{foo$imag}.  You can
816
examine and set these two fictitious variables with your debugger.
817
 
818
@node Decimal Float
819
@section Decimal Floating Types
820
@cindex decimal floating types
821
@cindex @code{_Decimal32} data type
822
@cindex @code{_Decimal64} data type
823
@cindex @code{_Decimal128} data type
824
@cindex @code{df} integer suffix
825
@cindex @code{dd} integer suffix
826
@cindex @code{dl} integer suffix
827
@cindex @code{DF} integer suffix
828
@cindex @code{DD} integer suffix
829
@cindex @code{DL} integer suffix
830
 
831
As an extension, the GNU C compiler supports decimal floating types as
832
defined in the N1176 draft of ISO/IEC WDTR24732.  Support for decimal
833
floating types in GCC will evolve as the draft technical report changes.
834
Calling conventions for any target might also change.  Not all targets
835
support decimal floating types.
836
 
837
The decimal floating types are @code{_Decimal32}, @code{_Decimal64}, and
838
@code{_Decimal128}.  They use a radix of ten, unlike the floating types
839
@code{float}, @code{double}, and @code{long double} whose radix is not
840
specified by the C standard but is usually two.
841
 
842
Support for decimal floating types includes the arithmetic operators
843
add, subtract, multiply, divide; unary arithmetic operators;
844
relational operators; equality operators; and conversions to and from
845
integer and other floating types.  Use a suffix @samp{df} or
846
@samp{DF} in a literal constant of type @code{_Decimal32}, @samp{dd}
847
or @samp{DD} for @code{_Decimal64}, and @samp{dl} or @samp{DL} for
848
@code{_Decimal128}.
849
 
850
GCC support of decimal float as specified by the draft technical report
851
is incomplete:
852
 
853
@itemize @bullet
854
@item
855
Translation time data type (TTDT) is not supported.
856
 
857
@item
858
Characteristics of decimal floating types are defined in header file
859
@file{decfloat.h} rather than @file{float.h}.
860
 
861
@item
862
When the value of a decimal floating type cannot be represented in the
863
integer type to which it is being converted, the result is undefined
864
rather than the result value specified by the draft technical report.
865
@end itemize
866
 
867
Types @code{_Decimal32}, @code{_Decimal64}, and @code{_Decimal128}
868
are supported by the DWARF2 debug information format.
869
 
870
@node Hex Floats
871
@section Hex Floats
872
@cindex hex floats
873
 
874
ISO C99 supports floating-point numbers written not only in the usual
875
decimal notation, such as @code{1.55e1}, but also numbers such as
876
@code{0x1.fp3} written in hexadecimal format.  As a GNU extension, GCC
877
supports this in C89 mode (except in some cases when strictly
878
conforming) and in C++.  In that format the
879
@samp{0x} hex introducer and the @samp{p} or @samp{P} exponent field are
880
mandatory.  The exponent is a decimal number that indicates the power of
881
2 by which the significant part will be multiplied.  Thus @samp{0x1.f} is
882
@tex
883
$1 {15\over16}$,
884
@end tex
885
@ifnottex
886
1 15/16,
887
@end ifnottex
888
@samp{p3} multiplies it by 8, and the value of @code{0x1.fp3}
889
is the same as @code{1.55e1}.
890
 
891
Unlike for floating-point numbers in the decimal notation the exponent
892
is always required in the hexadecimal notation.  Otherwise the compiler
893
would not be able to resolve the ambiguity of, e.g., @code{0x1.f}.  This
894
could mean @code{1.0f} or @code{1.9375} since @samp{f} is also the
895
extension for floating-point constants of type @code{float}.
896
 
897
@node Zero Length
898
@section Arrays of Length Zero
899
@cindex arrays of length zero
900
@cindex zero-length arrays
901
@cindex length-zero arrays
902
@cindex flexible array members
903
 
904
Zero-length arrays are allowed in GNU C@.  They are very useful as the
905
last element of a structure which is really a header for a variable-length
906
object:
907
 
908
@smallexample
909
struct line @{
910
  int length;
911
  char contents[0];
912
@};
913
 
914
struct line *thisline = (struct line *)
915
  malloc (sizeof (struct line) + this_length);
916
thisline->length = this_length;
917
@end smallexample
918
 
919
In ISO C90, you would have to give @code{contents} a length of 1, which
920
means either you waste space or complicate the argument to @code{malloc}.
921
 
922
In ISO C99, you would use a @dfn{flexible array member}, which is
923
slightly different in syntax and semantics:
924
 
925
@itemize @bullet
926
@item
927
Flexible array members are written as @code{contents[]} without
928
the @code{0}.
929
 
930
@item
931
Flexible array members have incomplete type, and so the @code{sizeof}
932
operator may not be applied.  As a quirk of the original implementation
933
of zero-length arrays, @code{sizeof} evaluates to zero.
934
 
935
@item
936
Flexible array members may only appear as the last member of a
937
@code{struct} that is otherwise non-empty.
938
 
939
@item
940
A structure containing a flexible array member, or a union containing
941
such a structure (possibly recursively), may not be a member of a
942
structure or an element of an array.  (However, these uses are
943
permitted by GCC as extensions.)
944
@end itemize
945
 
946
GCC versions before 3.0 allowed zero-length arrays to be statically
947
initialized, as if they were flexible arrays.  In addition to those
948
cases that were useful, it also allowed initializations in situations
949
that would corrupt later data.  Non-empty initialization of zero-length
950
arrays is now treated like any case where there are more initializer
951
elements than the array holds, in that a suitable warning about "excess
952
elements in array" is given, and the excess elements (all of them, in
953
this case) are ignored.
954
 
955
Instead GCC allows static initialization of flexible array members.
956
This is equivalent to defining a new structure containing the original
957
structure followed by an array of sufficient size to contain the data.
958
I.e.@: in the following, @code{f1} is constructed as if it were declared
959
like @code{f2}.
960
 
961
@smallexample
962
struct f1 @{
963
  int x; int y[];
964
@} f1 = @{ 1, @{ 2, 3, 4 @} @};
965
 
966
struct f2 @{
967
  struct f1 f1; int data[3];
968
@} f2 = @{ @{ 1 @}, @{ 2, 3, 4 @} @};
969
@end smallexample
970
 
971
@noindent
972
The convenience of this extension is that @code{f1} has the desired
973
type, eliminating the need to consistently refer to @code{f2.f1}.
974
 
975
This has symmetry with normal static arrays, in that an array of
976
unknown size is also written with @code{[]}.
977
 
978
Of course, this extension only makes sense if the extra data comes at
979
the end of a top-level object, as otherwise we would be overwriting
980
data at subsequent offsets.  To avoid undue complication and confusion
981
with initialization of deeply nested arrays, we simply disallow any
982
non-empty initialization except when the structure is the top-level
983
object.  For example:
984
 
985
@smallexample
986
struct foo @{ int x; int y[]; @};
987
struct bar @{ struct foo z; @};
988
 
989
struct foo a = @{ 1, @{ 2, 3, 4 @} @};        // @r{Valid.}
990
struct bar b = @{ @{ 1, @{ 2, 3, 4 @} @} @};    // @r{Invalid.}
991
struct bar c = @{ @{ 1, @{ @} @} @};            // @r{Valid.}
992
struct foo d[1] = @{ @{ 1 @{ 2, 3, 4 @} @} @};  // @r{Invalid.}
993
@end smallexample
994
 
995
@node Empty Structures
996
@section Structures With No Members
997
@cindex empty structures
998
@cindex zero-size structures
999
 
1000
GCC permits a C structure to have no members:
1001
 
1002
@smallexample
1003
struct empty @{
1004
@};
1005
@end smallexample
1006
 
1007
The structure will have size zero.  In C++, empty structures are part
1008
of the language.  G++ treats empty structures as if they had a single
1009
member of type @code{char}.
1010
 
1011
@node Variable Length
1012
@section Arrays of Variable Length
1013
@cindex variable-length arrays
1014
@cindex arrays of variable length
1015
@cindex VLAs
1016
 
1017
Variable-length automatic arrays are allowed in ISO C99, and as an
1018
extension GCC accepts them in C89 mode and in C++.  (However, GCC's
1019
implementation of variable-length arrays does not yet conform in detail
1020
to the ISO C99 standard.)  These arrays are
1021
declared like any other automatic arrays, but with a length that is not
1022
a constant expression.  The storage is allocated at the point of
1023
declaration and deallocated when the brace-level is exited.  For
1024
example:
1025
 
1026
@smallexample
1027
FILE *
1028
concat_fopen (char *s1, char *s2, char *mode)
1029
@{
1030
  char str[strlen (s1) + strlen (s2) + 1];
1031
  strcpy (str, s1);
1032
  strcat (str, s2);
1033
  return fopen (str, mode);
1034
@}
1035
@end smallexample
1036
 
1037
@cindex scope of a variable length array
1038
@cindex variable-length array scope
1039
@cindex deallocating variable length arrays
1040
Jumping or breaking out of the scope of the array name deallocates the
1041
storage.  Jumping into the scope is not allowed; you get an error
1042
message for it.
1043
 
1044
@cindex @code{alloca} vs variable-length arrays
1045
You can use the function @code{alloca} to get an effect much like
1046
variable-length arrays.  The function @code{alloca} is available in
1047
many other C implementations (but not in all).  On the other hand,
1048
variable-length arrays are more elegant.
1049
 
1050
There are other differences between these two methods.  Space allocated
1051
with @code{alloca} exists until the containing @emph{function} returns.
1052
The space for a variable-length array is deallocated as soon as the array
1053
name's scope ends.  (If you use both variable-length arrays and
1054
@code{alloca} in the same function, deallocation of a variable-length array
1055
will also deallocate anything more recently allocated with @code{alloca}.)
1056
 
1057
You can also use variable-length arrays as arguments to functions:
1058
 
1059
@smallexample
1060
struct entry
1061
tester (int len, char data[len][len])
1062
@{
1063
  /* @r{@dots{}} */
1064
@}
1065
@end smallexample
1066
 
1067
The length of an array is computed once when the storage is allocated
1068
and is remembered for the scope of the array in case you access it with
1069
@code{sizeof}.
1070
 
1071
If you want to pass the array first and the length afterward, you can
1072
use a forward declaration in the parameter list---another GNU extension.
1073
 
1074
@smallexample
1075
struct entry
1076
tester (int len; char data[len][len], int len)
1077
@{
1078
  /* @r{@dots{}} */
1079
@}
1080
@end smallexample
1081
 
1082
@cindex parameter forward declaration
1083
The @samp{int len} before the semicolon is a @dfn{parameter forward
1084
declaration}, and it serves the purpose of making the name @code{len}
1085
known when the declaration of @code{data} is parsed.
1086
 
1087
You can write any number of such parameter forward declarations in the
1088
parameter list.  They can be separated by commas or semicolons, but the
1089
last one must end with a semicolon, which is followed by the ``real''
1090
parameter declarations.  Each forward declaration must match a ``real''
1091
declaration in parameter name and data type.  ISO C99 does not support
1092
parameter forward declarations.
1093
 
1094
@node Variadic Macros
1095
@section Macros with a Variable Number of Arguments.
1096
@cindex variable number of arguments
1097
@cindex macro with variable arguments
1098
@cindex rest argument (in macro)
1099
@cindex variadic macros
1100
 
1101
In the ISO C standard of 1999, a macro can be declared to accept a
1102
variable number of arguments much as a function can.  The syntax for
1103
defining the macro is similar to that of a function.  Here is an
1104
example:
1105
 
1106
@smallexample
1107
#define debug(format, ...) fprintf (stderr, format, __VA_ARGS__)
1108
@end smallexample
1109
 
1110
Here @samp{@dots{}} is a @dfn{variable argument}.  In the invocation of
1111
such a macro, it represents the zero or more tokens until the closing
1112
parenthesis that ends the invocation, including any commas.  This set of
1113
tokens replaces the identifier @code{__VA_ARGS__} in the macro body
1114
wherever it appears.  See the CPP manual for more information.
1115
 
1116
GCC has long supported variadic macros, and used a different syntax that
1117
allowed you to give a name to the variable arguments just like any other
1118
argument.  Here is an example:
1119
 
1120
@smallexample
1121
#define debug(format, args...) fprintf (stderr, format, args)
1122
@end smallexample
1123
 
1124
This is in all ways equivalent to the ISO C example above, but arguably
1125
more readable and descriptive.
1126
 
1127
GNU CPP has two further variadic macro extensions, and permits them to
1128
be used with either of the above forms of macro definition.
1129
 
1130
In standard C, you are not allowed to leave the variable argument out
1131
entirely; but you are allowed to pass an empty argument.  For example,
1132
this invocation is invalid in ISO C, because there is no comma after
1133
the string:
1134
 
1135
@smallexample
1136
debug ("A message")
1137
@end smallexample
1138
 
1139
GNU CPP permits you to completely omit the variable arguments in this
1140
way.  In the above examples, the compiler would complain, though since
1141
the expansion of the macro still has the extra comma after the format
1142
string.
1143
 
1144
To help solve this problem, CPP behaves specially for variable arguments
1145
used with the token paste operator, @samp{##}.  If instead you write
1146
 
1147
@smallexample
1148
#define debug(format, ...) fprintf (stderr, format, ## __VA_ARGS__)
1149
@end smallexample
1150
 
1151
and if the variable arguments are omitted or empty, the @samp{##}
1152
operator causes the preprocessor to remove the comma before it.  If you
1153
do provide some variable arguments in your macro invocation, GNU CPP
1154
does not complain about the paste operation and instead places the
1155
variable arguments after the comma.  Just like any other pasted macro
1156
argument, these arguments are not macro expanded.
1157
 
1158
@node Escaped Newlines
1159
@section Slightly Looser Rules for Escaped Newlines
1160
@cindex escaped newlines
1161
@cindex newlines (escaped)
1162
 
1163
Recently, the preprocessor has relaxed its treatment of escaped
1164
newlines.  Previously, the newline had to immediately follow a
1165
backslash.  The current implementation allows whitespace in the form
1166
of spaces, horizontal and vertical tabs, and form feeds between the
1167
backslash and the subsequent newline.  The preprocessor issues a
1168
warning, but treats it as a valid escaped newline and combines the two
1169
lines to form a single logical line.  This works within comments and
1170
tokens, as well as between tokens.  Comments are @emph{not} treated as
1171
whitespace for the purposes of this relaxation, since they have not
1172
yet been replaced with spaces.
1173
 
1174
@node Subscripting
1175
@section Non-Lvalue Arrays May Have Subscripts
1176
@cindex subscripting
1177
@cindex arrays, non-lvalue
1178
 
1179
@cindex subscripting and function values
1180
In ISO C99, arrays that are not lvalues still decay to pointers, and
1181
may be subscripted, although they may not be modified or used after
1182
the next sequence point and the unary @samp{&} operator may not be
1183
applied to them.  As an extension, GCC allows such arrays to be
1184
subscripted in C89 mode, though otherwise they do not decay to
1185
pointers outside C99 mode.  For example,
1186
this is valid in GNU C though not valid in C89:
1187
 
1188
@smallexample
1189
@group
1190
struct foo @{int a[4];@};
1191
 
1192
struct foo f();
1193
 
1194
bar (int index)
1195
@{
1196
  return f().a[index];
1197
@}
1198
@end group
1199
@end smallexample
1200
 
1201
@node Pointer Arith
1202
@section Arithmetic on @code{void}- and Function-Pointers
1203
@cindex void pointers, arithmetic
1204
@cindex void, size of pointer to
1205
@cindex function pointers, arithmetic
1206
@cindex function, size of pointer to
1207
 
1208
In GNU C, addition and subtraction operations are supported on pointers to
1209
@code{void} and on pointers to functions.  This is done by treating the
1210
size of a @code{void} or of a function as 1.
1211
 
1212
A consequence of this is that @code{sizeof} is also allowed on @code{void}
1213
and on function types, and returns 1.
1214
 
1215
@opindex Wpointer-arith
1216
The option @option{-Wpointer-arith} requests a warning if these extensions
1217
are used.
1218
 
1219
@node Initializers
1220
@section Non-Constant Initializers
1221
@cindex initializers, non-constant
1222
@cindex non-constant initializers
1223
 
1224
As in standard C++ and ISO C99, the elements of an aggregate initializer for an
1225
automatic variable are not required to be constant expressions in GNU C@.
1226
Here is an example of an initializer with run-time varying elements:
1227
 
1228
@smallexample
1229
foo (float f, float g)
1230
@{
1231
  float beat_freqs[2] = @{ f-g, f+g @};
1232
  /* @r{@dots{}} */
1233
@}
1234
@end smallexample
1235
 
1236
@node Compound Literals
1237
@section Compound Literals
1238
@cindex constructor expressions
1239
@cindex initializations in expressions
1240
@cindex structures, constructor expression
1241
@cindex expressions, constructor
1242
@cindex compound literals
1243
@c The GNU C name for what C99 calls compound literals was "constructor expressions".
1244
 
1245
ISO C99 supports compound literals.  A compound literal looks like
1246
a cast containing an initializer.  Its value is an object of the
1247
type specified in the cast, containing the elements specified in
1248
the initializer; it is an lvalue.  As an extension, GCC supports
1249
compound literals in C89 mode and in C++.
1250
 
1251
Usually, the specified type is a structure.  Assume that
1252
@code{struct foo} and @code{structure} are declared as shown:
1253
 
1254
@smallexample
1255
struct foo @{int a; char b[2];@} structure;
1256
@end smallexample
1257
 
1258
@noindent
1259
Here is an example of constructing a @code{struct foo} with a compound literal:
1260
 
1261
@smallexample
1262
structure = ((struct foo) @{x + y, 'a', 0@});
1263
@end smallexample
1264
 
1265
@noindent
1266
This is equivalent to writing the following:
1267
 
1268
@smallexample
1269
@{
1270
  struct foo temp = @{x + y, 'a', 0@};
1271
  structure = temp;
1272
@}
1273
@end smallexample
1274
 
1275
You can also construct an array.  If all the elements of the compound literal
1276
are (made up of) simple constant expressions, suitable for use in
1277
initializers of objects of static storage duration, then the compound
1278
literal can be coerced to a pointer to its first element and used in
1279
such an initializer, as shown here:
1280
 
1281
@smallexample
1282
char **foo = (char *[]) @{ "x", "y", "z" @};
1283
@end smallexample
1284
 
1285
Compound literals for scalar types and union types are is
1286
also allowed, but then the compound literal is equivalent
1287
to a cast.
1288
 
1289
As a GNU extension, GCC allows initialization of objects with static storage
1290
duration by compound literals (which is not possible in ISO C99, because
1291
the initializer is not a constant).
1292
It is handled as if the object was initialized only with the bracket
1293
enclosed list if the types of the compound literal and the object match.
1294
The initializer list of the compound literal must be constant.
1295
If the object being initialized has array type of unknown size, the size is
1296
determined by compound literal size.
1297
 
1298
@smallexample
1299
static struct foo x = (struct foo) @{1, 'a', 'b'@};
1300
static int y[] = (int []) @{1, 2, 3@};
1301
static int z[] = (int [3]) @{1@};
1302
@end smallexample
1303
 
1304
@noindent
1305
The above lines are equivalent to the following:
1306
@smallexample
1307
static struct foo x = @{1, 'a', 'b'@};
1308
static int y[] = @{1, 2, 3@};
1309
static int z[] = @{1, 0, 0@};
1310
@end smallexample
1311
 
1312
@node Designated Inits
1313
@section Designated Initializers
1314
@cindex initializers with labeled elements
1315
@cindex labeled elements in initializers
1316
@cindex case labels in initializers
1317
@cindex designated initializers
1318
 
1319
Standard C89 requires the elements of an initializer to appear in a fixed
1320
order, the same as the order of the elements in the array or structure
1321
being initialized.
1322
 
1323
In ISO C99 you can give the elements in any order, specifying the array
1324
indices or structure field names they apply to, and GNU C allows this as
1325
an extension in C89 mode as well.  This extension is not
1326
implemented in GNU C++.
1327
 
1328
To specify an array index, write
1329
@samp{[@var{index}] =} before the element value.  For example,
1330
 
1331
@smallexample
1332
int a[6] = @{ [4] = 29, [2] = 15 @};
1333
@end smallexample
1334
 
1335
@noindent
1336
is equivalent to
1337
 
1338
@smallexample
1339
int a[6] = @{ 0, 0, 15, 0, 29, 0 @};
1340
@end smallexample
1341
 
1342
@noindent
1343
The index values must be constant expressions, even if the array being
1344
initialized is automatic.
1345
 
1346
An alternative syntax for this which has been obsolete since GCC 2.5 but
1347
GCC still accepts is to write @samp{[@var{index}]} before the element
1348
value, with no @samp{=}.
1349
 
1350
To initialize a range of elements to the same value, write
1351
@samp{[@var{first} ... @var{last}] = @var{value}}.  This is a GNU
1352
extension.  For example,
1353
 
1354
@smallexample
1355
int widths[] = @{ [0 ... 9] = 1, [10 ... 99] = 2, [100] = 3 @};
1356
@end smallexample
1357
 
1358
@noindent
1359
If the value in it has side-effects, the side-effects will happen only once,
1360
not for each initialized field by the range initializer.
1361
 
1362
@noindent
1363
Note that the length of the array is the highest value specified
1364
plus one.
1365
 
1366
In a structure initializer, specify the name of a field to initialize
1367
with @samp{.@var{fieldname} =} before the element value.  For example,
1368
given the following structure,
1369
 
1370
@smallexample
1371
struct point @{ int x, y; @};
1372
@end smallexample
1373
 
1374
@noindent
1375
the following initialization
1376
 
1377
@smallexample
1378
struct point p = @{ .y = yvalue, .x = xvalue @};
1379
@end smallexample
1380
 
1381
@noindent
1382
is equivalent to
1383
 
1384
@smallexample
1385
struct point p = @{ xvalue, yvalue @};
1386
@end smallexample
1387
 
1388
Another syntax which has the same meaning, obsolete since GCC 2.5, is
1389
@samp{@var{fieldname}:}, as shown here:
1390
 
1391
@smallexample
1392
struct point p = @{ y: yvalue, x: xvalue @};
1393
@end smallexample
1394
 
1395
@cindex designators
1396
The @samp{[@var{index}]} or @samp{.@var{fieldname}} is known as a
1397
@dfn{designator}.  You can also use a designator (or the obsolete colon
1398
syntax) when initializing a union, to specify which element of the union
1399
should be used.  For example,
1400
 
1401
@smallexample
1402
union foo @{ int i; double d; @};
1403
 
1404
union foo f = @{ .d = 4 @};
1405
@end smallexample
1406
 
1407
@noindent
1408
will convert 4 to a @code{double} to store it in the union using
1409
the second element.  By contrast, casting 4 to type @code{union foo}
1410
would store it into the union as the integer @code{i}, since it is
1411
an integer.  (@xref{Cast to Union}.)
1412
 
1413
You can combine this technique of naming elements with ordinary C
1414
initialization of successive elements.  Each initializer element that
1415
does not have a designator applies to the next consecutive element of the
1416
array or structure.  For example,
1417
 
1418
@smallexample
1419
int a[6] = @{ [1] = v1, v2, [4] = v4 @};
1420
@end smallexample
1421
 
1422
@noindent
1423
is equivalent to
1424
 
1425
@smallexample
1426
int a[6] = @{ 0, v1, v2, 0, v4, 0 @};
1427
@end smallexample
1428
 
1429
Labeling the elements of an array initializer is especially useful
1430
when the indices are characters or belong to an @code{enum} type.
1431
For example:
1432
 
1433
@smallexample
1434
int whitespace[256]
1435
  = @{ [' '] = 1, ['\t'] = 1, ['\h'] = 1,
1436
      ['\f'] = 1, ['\n'] = 1, ['\r'] = 1 @};
1437
@end smallexample
1438
 
1439
@cindex designator lists
1440
You can also write a series of @samp{.@var{fieldname}} and
1441
@samp{[@var{index}]} designators before an @samp{=} to specify a
1442
nested subobject to initialize; the list is taken relative to the
1443
subobject corresponding to the closest surrounding brace pair.  For
1444
example, with the @samp{struct point} declaration above:
1445
 
1446
@smallexample
1447
struct point ptarray[10] = @{ [2].y = yv2, [2].x = xv2, [0].x = xv0 @};
1448
@end smallexample
1449
 
1450
@noindent
1451
If the same field is initialized multiple times, it will have value from
1452
the last initialization.  If any such overridden initialization has
1453
side-effect, it is unspecified whether the side-effect happens or not.
1454
Currently, GCC will discard them and issue a warning.
1455
 
1456
@node Case Ranges
1457
@section Case Ranges
1458
@cindex case ranges
1459
@cindex ranges in case statements
1460
 
1461
You can specify a range of consecutive values in a single @code{case} label,
1462
like this:
1463
 
1464
@smallexample
1465
case @var{low} ... @var{high}:
1466
@end smallexample
1467
 
1468
@noindent
1469
This has the same effect as the proper number of individual @code{case}
1470
labels, one for each integer value from @var{low} to @var{high}, inclusive.
1471
 
1472
This feature is especially useful for ranges of ASCII character codes:
1473
 
1474
@smallexample
1475
case 'A' ... 'Z':
1476
@end smallexample
1477
 
1478
@strong{Be careful:} Write spaces around the @code{...}, for otherwise
1479
it may be parsed wrong when you use it with integer values.  For example,
1480
write this:
1481
 
1482
@smallexample
1483
case 1 ... 5:
1484
@end smallexample
1485
 
1486
@noindent
1487
rather than this:
1488
 
1489
@smallexample
1490
case 1...5:
1491
@end smallexample
1492
 
1493
@node Cast to Union
1494
@section Cast to a Union Type
1495
@cindex cast to a union
1496
@cindex union, casting to a
1497
 
1498
A cast to union type is similar to other casts, except that the type
1499
specified is a union type.  You can specify the type either with
1500
@code{union @var{tag}} or with a typedef name.  A cast to union is actually
1501
a constructor though, not a cast, and hence does not yield an lvalue like
1502
normal casts.  (@xref{Compound Literals}.)
1503
 
1504
The types that may be cast to the union type are those of the members
1505
of the union.  Thus, given the following union and variables:
1506
 
1507
@smallexample
1508
union foo @{ int i; double d; @};
1509
int x;
1510
double y;
1511
@end smallexample
1512
 
1513
@noindent
1514
both @code{x} and @code{y} can be cast to type @code{union foo}.
1515
 
1516
Using the cast as the right-hand side of an assignment to a variable of
1517
union type is equivalent to storing in a member of the union:
1518
 
1519
@smallexample
1520
union foo u;
1521
/* @r{@dots{}} */
1522
u = (union foo) x  @equiv{}  u.i = x
1523
u = (union foo) y  @equiv{}  u.d = y
1524
@end smallexample
1525
 
1526
You can also use the union cast as a function argument:
1527
 
1528
@smallexample
1529
void hack (union foo);
1530
/* @r{@dots{}} */
1531
hack ((union foo) x);
1532
@end smallexample
1533
 
1534
@node Mixed Declarations
1535
@section Mixed Declarations and Code
1536
@cindex mixed declarations and code
1537
@cindex declarations, mixed with code
1538
@cindex code, mixed with declarations
1539
 
1540
ISO C99 and ISO C++ allow declarations and code to be freely mixed
1541
within compound statements.  As an extension, GCC also allows this in
1542
C89 mode.  For example, you could do:
1543
 
1544
@smallexample
1545
int i;
1546
/* @r{@dots{}} */
1547
i++;
1548
int j = i + 2;
1549
@end smallexample
1550
 
1551
Each identifier is visible from where it is declared until the end of
1552
the enclosing block.
1553
 
1554
@node Function Attributes
1555
@section Declaring Attributes of Functions
1556
@cindex function attributes
1557
@cindex declaring attributes of functions
1558
@cindex functions that never return
1559
@cindex functions that return more than once
1560
@cindex functions that have no side effects
1561
@cindex functions in arbitrary sections
1562
@cindex functions that behave like malloc
1563
@cindex @code{volatile} applied to function
1564
@cindex @code{const} applied to function
1565
@cindex functions with @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style arguments
1566
@cindex functions with non-null pointer arguments
1567
@cindex functions that are passed arguments in registers on the 386
1568
@cindex functions that pop the argument stack on the 386
1569
@cindex functions that do not pop the argument stack on the 386
1570
 
1571
In GNU C, you declare certain things about functions called in your program
1572
which help the compiler optimize function calls and check your code more
1573
carefully.
1574
 
1575
The keyword @code{__attribute__} allows you to specify special
1576
attributes when making a declaration.  This keyword is followed by an
1577
attribute specification inside double parentheses.  The following
1578
attributes are currently defined for functions on all targets:
1579
@code{noreturn}, @code{returns_twice}, @code{noinline}, @code{always_inline},
1580
@code{flatten}, @code{pure}, @code{const}, @code{nothrow}, @code{sentinel},
1581
@code{format}, @code{format_arg}, @code{no_instrument_function},
1582
@code{section}, @code{constructor}, @code{destructor}, @code{used},
1583
@code{unused}, @code{deprecated}, @code{weak}, @code{malloc},
1584
@code{alias}, @code{warn_unused_result}, @code{nonnull},
1585
@code{gnu_inline} and @code{externally_visible}.  Several other
1586
attributes are defined for functions on particular target systems.  Other
1587
attributes, including @code{section} are supported for variables declarations
1588
(@pxref{Variable Attributes}) and for types (@pxref{Type Attributes}).
1589
 
1590
You may also specify attributes with @samp{__} preceding and following
1591
each keyword.  This allows you to use them in header files without
1592
being concerned about a possible macro of the same name.  For example,
1593
you may use @code{__noreturn__} instead of @code{noreturn}.
1594
 
1595
@xref{Attribute Syntax}, for details of the exact syntax for using
1596
attributes.
1597
 
1598
@table @code
1599
@c Keep this table alphabetized by attribute name.  Treat _ as space.
1600
 
1601
@item alias ("@var{target}")
1602
@cindex @code{alias} attribute
1603
The @code{alias} attribute causes the declaration to be emitted as an
1604
alias for another symbol, which must be specified.  For instance,
1605
 
1606
@smallexample
1607
void __f () @{ /* @r{Do something.} */; @}
1608
void f () __attribute__ ((weak, alias ("__f")));
1609
@end smallexample
1610
 
1611
defines @samp{f} to be a weak alias for @samp{__f}.  In C++, the
1612
mangled name for the target must be used.  It is an error if @samp{__f}
1613
is not defined in the same translation unit.
1614
 
1615
Not all target machines support this attribute.
1616
 
1617
@item always_inline
1618
@cindex @code{always_inline} function attribute
1619
Generally, functions are not inlined unless optimization is specified.
1620
For functions declared inline, this attribute inlines the function even
1621
if no optimization level was specified.
1622
 
1623
@item gnu_inline
1624
@cindex @code{gnu_inline} function attribute
1625
This attribute should be used with a function which is also declared
1626
with the @code{inline} keyword.  It directs GCC to treat the function
1627
as if it were defined in gnu89 mode even when compiling in C99 or
1628
gnu99 mode.
1629
 
1630
If the function is declared @code{extern}, then this definition of the
1631
function is used only for inlining.  In no case is the function
1632
compiled as a standalone function, not even if you take its address
1633
explicitly.  Such an address becomes an external reference, as if you
1634
had only declared the function, and had not defined it.  This has
1635
almost the effect of a macro.  The way to use this is to put a
1636
function definition in a header file with this attribute, and put
1637
another copy of the function, without @code{extern}, in a library
1638
file.  The definition in the header file will cause most calls to the
1639
function to be inlined.  If any uses of the function remain, they will
1640
refer to the single copy in the library.  Note that the two
1641
definitions of the functions need not be precisely the same, although
1642
if they do not have the same effect your program may behave oddly.
1643
 
1644
If the function is neither @code{extern} nor @code{static}, then the
1645
function is compiled as a standalone function, as well as being
1646
inlined where possible.
1647
 
1648
This is how GCC traditionally handled functions declared
1649
@code{inline}.  Since ISO C99 specifies a different semantics for
1650
@code{inline}, this function attribute is provided as a transition
1651
measure and as a useful feature in its own right.  This attribute is
1652
available in GCC 4.1.3 and later.  It is available if either of the
1653
preprocessor macros @code{__GNUC_GNU_INLINE__} or
1654
@code{__GNUC_STDC_INLINE__} are defined.  @xref{Inline,,An Inline
1655
Function is As Fast As a Macro}.
1656
 
1657
Note that since the first version of GCC to support C99 inline semantics
1658
is 4.3, earlier versions of GCC which accept this attribute effectively
1659
assume that it is always present, whether or not it is given explicitly.
1660
In versions prior to 4.3, the only effect of explicitly including it is
1661
to disable warnings about using inline functions in C99 mode.
1662
 
1663
@cindex @code{flatten} function attribute
1664
@item flatten
1665
Generally, inlining into a function is limited.  For a function marked with
1666
this attribute, every call inside this function will be inlined, if possible.
1667
Whether the function itself is considered for inlining depends on its size and
1668
the current inlining parameters.  The @code{flatten} attribute only works
1669
reliably in unit-at-a-time mode.
1670
 
1671
@item cdecl
1672
@cindex functions that do pop the argument stack on the 386
1673
@opindex mrtd
1674
On the Intel 386, the @code{cdecl} attribute causes the compiler to
1675
assume that the calling function will pop off the stack space used to
1676
pass arguments.  This is
1677
useful to override the effects of the @option{-mrtd} switch.
1678
 
1679
@item const
1680
@cindex @code{const} function attribute
1681
Many functions do not examine any values except their arguments, and
1682
have no effects except the return value.  Basically this is just slightly
1683
more strict class than the @code{pure} attribute below, since function is not
1684
allowed to read global memory.
1685
 
1686
@cindex pointer arguments
1687
Note that a function that has pointer arguments and examines the data
1688
pointed to must @emph{not} be declared @code{const}.  Likewise, a
1689
function that calls a non-@code{const} function usually must not be
1690
@code{const}.  It does not make sense for a @code{const} function to
1691
return @code{void}.
1692
 
1693
The attribute @code{const} is not implemented in GCC versions earlier
1694
than 2.5.  An alternative way to declare that a function has no side
1695
effects, which works in the current version and in some older versions,
1696
is as follows:
1697
 
1698
@smallexample
1699
typedef int intfn ();
1700
 
1701
extern const intfn square;
1702
@end smallexample
1703
 
1704
This approach does not work in GNU C++ from 2.6.0 on, since the language
1705
specifies that the @samp{const} must be attached to the return value.
1706
 
1707
@item constructor
1708
@itemx destructor
1709
@cindex @code{constructor} function attribute
1710
@cindex @code{destructor} function attribute
1711
The @code{constructor} attribute causes the function to be called
1712
automatically before execution enters @code{main ()}.  Similarly, the
1713
@code{destructor} attribute causes the function to be called
1714
automatically after @code{main ()} has completed or @code{exit ()} has
1715
been called.  Functions with these attributes are useful for
1716
initializing data that will be used implicitly during the execution of
1717
the program.
1718
 
1719
These attributes are not currently implemented for Objective-C@.
1720
 
1721
@item deprecated
1722
@cindex @code{deprecated} attribute.
1723
The @code{deprecated} attribute results in a warning if the function
1724
is used anywhere in the source file.  This is useful when identifying
1725
functions that are expected to be removed in a future version of a
1726
program.  The warning also includes the location of the declaration
1727
of the deprecated function, to enable users to easily find further
1728
information about why the function is deprecated, or what they should
1729
do instead.  Note that the warnings only occurs for uses:
1730
 
1731
@smallexample
1732
int old_fn () __attribute__ ((deprecated));
1733
int old_fn ();
1734
int (*fn_ptr)() = old_fn;
1735
@end smallexample
1736
 
1737
results in a warning on line 3 but not line 2.
1738
 
1739
The @code{deprecated} attribute can also be used for variables and
1740
types (@pxref{Variable Attributes}, @pxref{Type Attributes}.)
1741
 
1742
@item dllexport
1743
@cindex @code{__declspec(dllexport)}
1744
On Microsoft Windows targets and Symbian OS targets the
1745
@code{dllexport} attribute causes the compiler to provide a global
1746
pointer to a pointer in a DLL, so that it can be referenced with the
1747
@code{dllimport} attribute.  On Microsoft Windows targets, the pointer
1748
name is formed by combining @code{_imp__} and the function or variable
1749
name.
1750
 
1751
You can use @code{__declspec(dllexport)} as a synonym for
1752
@code{__attribute__ ((dllexport))} for compatibility with other
1753
compilers.
1754
 
1755
On systems that support the @code{visibility} attribute, this
1756
attribute also implies ``default'' visibility, unless a
1757
@code{visibility} attribute is explicitly specified.  You should avoid
1758
the use of @code{dllexport} with ``hidden'' or ``internal''
1759
visibility; in the future GCC may issue an error for those cases.
1760
 
1761
Currently, the @code{dllexport} attribute is ignored for inlined
1762
functions, unless the @option{-fkeep-inline-functions} flag has been
1763
used.  The attribute is also ignored for undefined symbols.
1764
 
1765
When applied to C++ classes, the attribute marks defined non-inlined
1766
member functions and static data members as exports.  Static consts
1767
initialized in-class are not marked unless they are also defined
1768
out-of-class.
1769
 
1770
For Microsoft Windows targets there are alternative methods for
1771
including the symbol in the DLL's export table such as using a
1772
@file{.def} file with an @code{EXPORTS} section or, with GNU ld, using
1773
the @option{--export-all} linker flag.
1774
 
1775
@item dllimport
1776
@cindex @code{__declspec(dllimport)}
1777
On Microsoft Windows and Symbian OS targets, the @code{dllimport}
1778
attribute causes the compiler to reference a function or variable via
1779
a global pointer to a pointer that is set up by the DLL exporting the
1780
symbol.  The attribute implies @code{extern} storage.  On Microsoft
1781
Windows targets, the pointer name is formed by combining @code{_imp__}
1782
and the function or variable name.
1783
 
1784
You can use @code{__declspec(dllimport)} as a synonym for
1785
@code{__attribute__ ((dllimport))} for compatibility with other
1786
compilers.
1787
 
1788
Currently, the attribute is ignored for inlined functions.  If the
1789
attribute is applied to a symbol @emph{definition}, an error is reported.
1790
If a symbol previously declared @code{dllimport} is later defined, the
1791
attribute is ignored in subsequent references, and a warning is emitted.
1792
The attribute is also overridden by a subsequent declaration as
1793
@code{dllexport}.
1794
 
1795
When applied to C++ classes, the attribute marks non-inlined
1796
member functions and static data members as imports.  However, the
1797
attribute is ignored for virtual methods to allow creation of vtables
1798
using thunks.
1799
 
1800
On the SH Symbian OS target the @code{dllimport} attribute also has
1801
another affect---it can cause the vtable and run-time type information
1802
for a class to be exported.  This happens when the class has a
1803
dllimport'ed constructor or a non-inline, non-pure virtual function
1804
and, for either of those two conditions, the class also has a inline
1805
constructor or destructor and has a key function that is defined in
1806
the current translation unit.
1807
 
1808
For Microsoft Windows based targets the use of the @code{dllimport}
1809
attribute on functions is not necessary, but provides a small
1810
performance benefit by eliminating a thunk in the DLL@.  The use of the
1811
@code{dllimport} attribute on imported variables was required on older
1812
versions of the GNU linker, but can now be avoided by passing the
1813
@option{--enable-auto-import} switch to the GNU linker.  As with
1814
functions, using the attribute for a variable eliminates a thunk in
1815
the DLL@.
1816
 
1817
One drawback to using this attribute is that a pointer to a function
1818
or variable marked as @code{dllimport} cannot be used as a constant
1819
address.  On Microsoft Windows targets, the attribute can be disabled
1820
for functions by setting the @option{-mnop-fun-dllimport} flag.
1821
 
1822
@item eightbit_data
1823
@cindex eight bit data on the H8/300, H8/300H, and H8S
1824
Use this attribute on the H8/300, H8/300H, and H8S to indicate that the specified
1825
variable should be placed into the eight bit data section.
1826
The compiler will generate more efficient code for certain operations
1827
on data in the eight bit data area.  Note the eight bit data area is limited to
1828
256 bytes of data.
1829
 
1830
You must use GAS and GLD from GNU binutils version 2.7 or later for
1831
this attribute to work correctly.
1832
 
1833
@item exception_handler
1834
@cindex exception handler functions on the Blackfin processor
1835
Use this attribute on the Blackfin to indicate that the specified function
1836
is an exception handler.  The compiler will generate function entry and
1837
exit sequences suitable for use in an exception handler when this
1838
attribute is present.
1839
 
1840
@item far
1841
@cindex functions which handle memory bank switching
1842
On 68HC11 and 68HC12 the @code{far} attribute causes the compiler to
1843
use a calling convention that takes care of switching memory banks when
1844
entering and leaving a function.  This calling convention is also the
1845
default when using the @option{-mlong-calls} option.
1846
 
1847
On 68HC12 the compiler will use the @code{call} and @code{rtc} instructions
1848
to call and return from a function.
1849
 
1850
On 68HC11 the compiler will generate a sequence of instructions
1851
to invoke a board-specific routine to switch the memory bank and call the
1852
real function.  The board-specific routine simulates a @code{call}.
1853
At the end of a function, it will jump to a board-specific routine
1854
instead of using @code{rts}.  The board-specific return routine simulates
1855
the @code{rtc}.
1856
 
1857
@item fastcall
1858
@cindex functions that pop the argument stack on the 386
1859
On the Intel 386, the @code{fastcall} attribute causes the compiler to
1860
pass the first argument (if of integral type) in the register ECX and
1861
the second argument (if of integral type) in the register EDX@.  Subsequent
1862
and other typed arguments are passed on the stack.  The called function will
1863
pop the arguments off the stack.  If the number of arguments is variable all
1864
arguments are pushed on the stack.
1865
 
1866
@item format (@var{archetype}, @var{string-index}, @var{first-to-check})
1867
@cindex @code{format} function attribute
1868
@opindex Wformat
1869
The @code{format} attribute specifies that a function takes @code{printf},
1870
@code{scanf}, @code{strftime} or @code{strfmon} style arguments which
1871
should be type-checked against a format string.  For example, the
1872
declaration:
1873
 
1874
@smallexample
1875
extern int
1876
my_printf (void *my_object, const char *my_format, ...)
1877
      __attribute__ ((format (printf, 2, 3)));
1878
@end smallexample
1879
 
1880
@noindent
1881
causes the compiler to check the arguments in calls to @code{my_printf}
1882
for consistency with the @code{printf} style format string argument
1883
@code{my_format}.
1884
 
1885
The parameter @var{archetype} determines how the format string is
1886
interpreted, and should be @code{printf}, @code{scanf}, @code{strftime}
1887
or @code{strfmon}.  (You can also use @code{__printf__},
1888
@code{__scanf__}, @code{__strftime__} or @code{__strfmon__}.)  The
1889
parameter @var{string-index} specifies which argument is the format
1890
string argument (starting from 1), while @var{first-to-check} is the
1891
number of the first argument to check against the format string.  For
1892
functions where the arguments are not available to be checked (such as
1893
@code{vprintf}), specify the third parameter as zero.  In this case the
1894
compiler only checks the format string for consistency.  For
1895
@code{strftime} formats, the third parameter is required to be zero.
1896
Since non-static C++ methods have an implicit @code{this} argument, the
1897
arguments of such methods should be counted from two, not one, when
1898
giving values for @var{string-index} and @var{first-to-check}.
1899
 
1900
In the example above, the format string (@code{my_format}) is the second
1901
argument of the function @code{my_print}, and the arguments to check
1902
start with the third argument, so the correct parameters for the format
1903
attribute are 2 and 3.
1904
 
1905
@opindex ffreestanding
1906
@opindex fno-builtin
1907
The @code{format} attribute allows you to identify your own functions
1908
which take format strings as arguments, so that GCC can check the
1909
calls to these functions for errors.  The compiler always (unless
1910
@option{-ffreestanding} or @option{-fno-builtin} is used) checks formats
1911
for the standard library functions @code{printf}, @code{fprintf},
1912
@code{sprintf}, @code{scanf}, @code{fscanf}, @code{sscanf}, @code{strftime},
1913
@code{vprintf}, @code{vfprintf} and @code{vsprintf} whenever such
1914
warnings are requested (using @option{-Wformat}), so there is no need to
1915
modify the header file @file{stdio.h}.  In C99 mode, the functions
1916
@code{snprintf}, @code{vsnprintf}, @code{vscanf}, @code{vfscanf} and
1917
@code{vsscanf} are also checked.  Except in strictly conforming C
1918
standard modes, the X/Open function @code{strfmon} is also checked as
1919
are @code{printf_unlocked} and @code{fprintf_unlocked}.
1920
@xref{C Dialect Options,,Options Controlling C Dialect}.
1921
 
1922
The target may provide additional types of format checks.
1923
@xref{Target Format Checks,,Format Checks Specific to Particular
1924
Target Machines}.
1925
 
1926
@item format_arg (@var{string-index})
1927
@cindex @code{format_arg} function attribute
1928
@opindex Wformat-nonliteral
1929
The @code{format_arg} attribute specifies that a function takes a format
1930
string for a @code{printf}, @code{scanf}, @code{strftime} or
1931
@code{strfmon} style function and modifies it (for example, to translate
1932
it into another language), so the result can be passed to a
1933
@code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style
1934
function (with the remaining arguments to the format function the same
1935
as they would have been for the unmodified string).  For example, the
1936
declaration:
1937
 
1938
@smallexample
1939
extern char *
1940
my_dgettext (char *my_domain, const char *my_format)
1941
      __attribute__ ((format_arg (2)));
1942
@end smallexample
1943
 
1944
@noindent
1945
causes the compiler to check the arguments in calls to a @code{printf},
1946
@code{scanf}, @code{strftime} or @code{strfmon} type function, whose
1947
format string argument is a call to the @code{my_dgettext} function, for
1948
consistency with the format string argument @code{my_format}.  If the
1949
@code{format_arg} attribute had not been specified, all the compiler
1950
could tell in such calls to format functions would be that the format
1951
string argument is not constant; this would generate a warning when
1952
@option{-Wformat-nonliteral} is used, but the calls could not be checked
1953
without the attribute.
1954
 
1955
The parameter @var{string-index} specifies which argument is the format
1956
string argument (starting from one).  Since non-static C++ methods have
1957
an implicit @code{this} argument, the arguments of such methods should
1958
be counted from two.
1959
 
1960
The @code{format-arg} attribute allows you to identify your own
1961
functions which modify format strings, so that GCC can check the
1962
calls to @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon}
1963
type function whose operands are a call to one of your own function.
1964
The compiler always treats @code{gettext}, @code{dgettext}, and
1965
@code{dcgettext} in this manner except when strict ISO C support is
1966
requested by @option{-ansi} or an appropriate @option{-std} option, or
1967
@option{-ffreestanding} or @option{-fno-builtin}
1968
is used.  @xref{C Dialect Options,,Options
1969
Controlling C Dialect}.
1970
 
1971
@item function_vector
1972
@cindex calling functions through the function vector on the H8/300 processors
1973
Use this attribute on the H8/300, H8/300H, and H8S to indicate that the specified
1974
function should be called through the function vector.  Calling a
1975
function through the function vector will reduce code size, however;
1976
the function vector has a limited size (maximum 128 entries on the H8/300
1977
and 64 entries on the H8/300H and H8S) and shares space with the interrupt vector.
1978
 
1979
You must use GAS and GLD from GNU binutils version 2.7 or later for
1980
this attribute to work correctly.
1981
 
1982
@item interrupt
1983
@cindex interrupt handler functions
1984
Use this attribute on the ARM, AVR, C4x, CRX, M32C, M32R/D, MS1, and Xstormy16
1985
ports to indicate that the specified function is an interrupt handler.
1986
The compiler will generate function entry and exit sequences suitable
1987
for use in an interrupt handler when this attribute is present.
1988
 
1989
Note, interrupt handlers for the Blackfin, m68k, H8/300, H8/300H, H8S, and
1990
SH processors can be specified via the @code{interrupt_handler} attribute.
1991
 
1992
Note, on the AVR, interrupts will be enabled inside the function.
1993
 
1994
Note, for the ARM, you can specify the kind of interrupt to be handled by
1995
adding an optional parameter to the interrupt attribute like this:
1996
 
1997
@smallexample
1998
void f () __attribute__ ((interrupt ("IRQ")));
1999
@end smallexample
2000
 
2001
Permissible values for this parameter are: IRQ, FIQ, SWI, ABORT and UNDEF@.
2002
 
2003
@item interrupt_handler
2004
@cindex interrupt handler functions on the Blackfin, m68k, H8/300 and SH processors
2005
Use this attribute on the Blackfin, m68k, H8/300, H8/300H, H8S, and SH to
2006
indicate that the specified function is an interrupt handler.  The compiler
2007
will generate function entry and exit sequences suitable for use in an
2008
interrupt handler when this attribute is present.
2009
 
2010
@item kspisusp
2011
@cindex User stack pointer in interrupts on the Blackfin
2012
When used together with @code{interrupt_handler}, @code{exception_handler}
2013
or @code{nmi_handler}, code will be generated to load the stack pointer
2014
from the USP register in the function prologue.
2015
 
2016
@item long_call/short_call
2017
@cindex indirect calls on ARM
2018
This attribute specifies how a particular function is called on
2019
ARM@.  Both attributes override the @option{-mlong-calls} (@pxref{ARM Options})
2020
command line switch and @code{#pragma long_calls} settings.  The
2021
@code{long_call} attribute indicates that the function might be far
2022
away from the call site and require a different (more expensive)
2023
calling sequence.   The @code{short_call} attribute always places
2024
the offset to the function from the call site into the @samp{BL}
2025
instruction directly.
2026
 
2027
@item longcall/shortcall
2028
@cindex functions called via pointer on the RS/6000 and PowerPC
2029
On the Blackfin, RS/6000 and PowerPC, the @code{longcall} attribute
2030
indicates that the function might be far away from the call site and
2031
require a different (more expensive) calling sequence.  The
2032
@code{shortcall} attribute indicates that the function is always close
2033
enough for the shorter calling sequence to be used.  These attributes
2034
override both the @option{-mlongcall} switch and, on the RS/6000 and
2035
PowerPC, the @code{#pragma longcall} setting.
2036
 
2037
@xref{RS/6000 and PowerPC Options}, for more information on whether long
2038
calls are necessary.
2039
 
2040
@item long_call
2041
@cindex indirect calls on MIPS
2042
This attribute specifies how a particular function is called on MIPS@.
2043
The attribute overrides the @option{-mlong-calls} (@pxref{MIPS Options})
2044
command line switch.  This attribute causes the compiler to always call
2045
the function by first loading its address into a register, and then using
2046
the contents of that register.
2047
 
2048
@item malloc
2049
@cindex @code{malloc} attribute
2050
The @code{malloc} attribute is used to tell the compiler that a function
2051
may be treated as if any non-@code{NULL} pointer it returns cannot
2052
alias any other pointer valid when the function returns.
2053
This will often improve optimization.
2054
Standard functions with this property include @code{malloc} and
2055
@code{calloc}.  @code{realloc}-like functions have this property as
2056
long as the old pointer is never referred to (including comparing it
2057
to the new pointer) after the function returns a non-@code{NULL}
2058
value.
2059
 
2060
@item model (@var{model-name})
2061
@cindex function addressability on the M32R/D
2062
@cindex variable addressability on the IA-64
2063
 
2064
On the M32R/D, use this attribute to set the addressability of an
2065
object, and of the code generated for a function.  The identifier
2066
@var{model-name} is one of @code{small}, @code{medium}, or
2067
@code{large}, representing each of the code models.
2068
 
2069
Small model objects live in the lower 16MB of memory (so that their
2070
addresses can be loaded with the @code{ld24} instruction), and are
2071
callable with the @code{bl} instruction.
2072
 
2073
Medium model objects may live anywhere in the 32-bit address space (the
2074
compiler will generate @code{seth/add3} instructions to load their addresses),
2075
and are callable with the @code{bl} instruction.
2076
 
2077
Large model objects may live anywhere in the 32-bit address space (the
2078
compiler will generate @code{seth/add3} instructions to load their addresses),
2079
and may not be reachable with the @code{bl} instruction (the compiler will
2080
generate the much slower @code{seth/add3/jl} instruction sequence).
2081
 
2082
On IA-64, use this attribute to set the addressability of an object.
2083
At present, the only supported identifier for @var{model-name} is
2084
@code{small}, indicating addressability via ``small'' (22-bit)
2085
addresses (so that their addresses can be loaded with the @code{addl}
2086
instruction).  Caveat: such addressing is by definition not position
2087
independent and hence this attribute must not be used for objects
2088
defined by shared libraries.
2089
 
2090
@item naked
2091
@cindex function without a prologue/epilogue code
2092
Use this attribute on the ARM, AVR, C4x and IP2K ports to indicate that the
2093
specified function does not need prologue/epilogue sequences generated by
2094
the compiler.  It is up to the programmer to provide these sequences.
2095
 
2096
@item near
2097
@cindex functions which do not handle memory bank switching on 68HC11/68HC12
2098
On 68HC11 and 68HC12 the @code{near} attribute causes the compiler to
2099
use the normal calling convention based on @code{jsr} and @code{rts}.
2100
This attribute can be used to cancel the effect of the @option{-mlong-calls}
2101
option.
2102
 
2103
@item nesting
2104
@cindex Allow nesting in an interrupt handler on the Blackfin processor.
2105
Use this attribute together with @code{interrupt_handler},
2106
@code{exception_handler} or @code{nmi_handler} to indicate that the function
2107
entry code should enable nested interrupts or exceptions.
2108
 
2109
@item nmi_handler
2110
@cindex NMI handler functions on the Blackfin processor
2111
Use this attribute on the Blackfin to indicate that the specified function
2112
is an NMI handler.  The compiler will generate function entry and
2113
exit sequences suitable for use in an NMI handler when this
2114
attribute is present.
2115
 
2116
@item no_instrument_function
2117
@cindex @code{no_instrument_function} function attribute
2118
@opindex finstrument-functions
2119
If @option{-finstrument-functions} is given, profiling function calls will
2120
be generated at entry and exit of most user-compiled functions.
2121
Functions with this attribute will not be so instrumented.
2122
 
2123
@item noinline
2124
@cindex @code{noinline} function attribute
2125
This function attribute prevents a function from being considered for
2126
inlining.
2127
 
2128
@item nonnull (@var{arg-index}, @dots{})
2129
@cindex @code{nonnull} function attribute
2130
The @code{nonnull} attribute specifies that some function parameters should
2131
be non-null pointers.  For instance, the declaration:
2132
 
2133
@smallexample
2134
extern void *
2135
my_memcpy (void *dest, const void *src, size_t len)
2136
        __attribute__((nonnull (1, 2)));
2137
@end smallexample
2138
 
2139
@noindent
2140
causes the compiler to check that, in calls to @code{my_memcpy},
2141
arguments @var{dest} and @var{src} are non-null.  If the compiler
2142
determines that a null pointer is passed in an argument slot marked
2143
as non-null, and the @option{-Wnonnull} option is enabled, a warning
2144
is issued.  The compiler may also choose to make optimizations based
2145
on the knowledge that certain function arguments will not be null.
2146
 
2147
If no argument index list is given to the @code{nonnull} attribute,
2148
all pointer arguments are marked as non-null.  To illustrate, the
2149
following declaration is equivalent to the previous example:
2150
 
2151
@smallexample
2152
extern void *
2153
my_memcpy (void *dest, const void *src, size_t len)
2154
        __attribute__((nonnull));
2155
@end smallexample
2156
 
2157
@item noreturn
2158
@cindex @code{noreturn} function attribute
2159
A few standard library functions, such as @code{abort} and @code{exit},
2160
cannot return.  GCC knows this automatically.  Some programs define
2161
their own functions that never return.  You can declare them
2162
@code{noreturn} to tell the compiler this fact.  For example,
2163
 
2164
@smallexample
2165
@group
2166
void fatal () __attribute__ ((noreturn));
2167
 
2168
void
2169
fatal (/* @r{@dots{}} */)
2170
@{
2171
  /* @r{@dots{}} */ /* @r{Print error message.} */ /* @r{@dots{}} */
2172
  exit (1);
2173
@}
2174
@end group
2175
@end smallexample
2176
 
2177
The @code{noreturn} keyword tells the compiler to assume that
2178
@code{fatal} cannot return.  It can then optimize without regard to what
2179
would happen if @code{fatal} ever did return.  This makes slightly
2180
better code.  More importantly, it helps avoid spurious warnings of
2181
uninitialized variables.
2182
 
2183
The @code{noreturn} keyword does not affect the exceptional path when that
2184
applies: a @code{noreturn}-marked function may still return to the caller
2185
by throwing an exception or calling @code{longjmp}.
2186
 
2187
Do not assume that registers saved by the calling function are
2188
restored before calling the @code{noreturn} function.
2189
 
2190
It does not make sense for a @code{noreturn} function to have a return
2191
type other than @code{void}.
2192
 
2193
The attribute @code{noreturn} is not implemented in GCC versions
2194
earlier than 2.5.  An alternative way to declare that a function does
2195
not return, which works in the current version and in some older
2196
versions, is as follows:
2197
 
2198
@smallexample
2199
typedef void voidfn ();
2200
 
2201
volatile voidfn fatal;
2202
@end smallexample
2203
 
2204
This approach does not work in GNU C++.
2205
 
2206
@item nothrow
2207
@cindex @code{nothrow} function attribute
2208
The @code{nothrow} attribute is used to inform the compiler that a
2209
function cannot throw an exception.  For example, most functions in
2210
the standard C library can be guaranteed not to throw an exception
2211
with the notable exceptions of @code{qsort} and @code{bsearch} that
2212
take function pointer arguments.  The @code{nothrow} attribute is not
2213
implemented in GCC versions earlier than 3.3.
2214
 
2215
@item pure
2216
@cindex @code{pure} function attribute
2217
Many functions have no effects except the return value and their
2218
return value depends only on the parameters and/or global variables.
2219
Such a function can be subject
2220
to common subexpression elimination and loop optimization just as an
2221
arithmetic operator would be.  These functions should be declared
2222
with the attribute @code{pure}.  For example,
2223
 
2224
@smallexample
2225
int square (int) __attribute__ ((pure));
2226
@end smallexample
2227
 
2228
@noindent
2229
says that the hypothetical function @code{square} is safe to call
2230
fewer times than the program says.
2231
 
2232
Some of common examples of pure functions are @code{strlen} or @code{memcmp}.
2233
Interesting non-pure functions are functions with infinite loops or those
2234
depending on volatile memory or other system resource, that may change between
2235
two consecutive calls (such as @code{feof} in a multithreading environment).
2236
 
2237
The attribute @code{pure} is not implemented in GCC versions earlier
2238
than 2.96.
2239
 
2240
@item regparm (@var{number})
2241
@cindex @code{regparm} attribute
2242
@cindex functions that are passed arguments in registers on the 386
2243
On the Intel 386, the @code{regparm} attribute causes the compiler to
2244
pass arguments number one to @var{number} if they are of integral type
2245
in registers EAX, EDX, and ECX instead of on the stack.  Functions that
2246
take a variable number of arguments will continue to be passed all of their
2247
arguments on the stack.
2248
 
2249
Beware that on some ELF systems this attribute is unsuitable for
2250
global functions in shared libraries with lazy binding (which is the
2251
default).  Lazy binding will send the first call via resolving code in
2252
the loader, which might assume EAX, EDX and ECX can be clobbered, as
2253
per the standard calling conventions.  Solaris 8 is affected by this.
2254
GNU systems with GLIBC 2.1 or higher, and FreeBSD, are believed to be
2255
safe since the loaders there save all registers.  (Lazy binding can be
2256
disabled with the linker or the loader if desired, to avoid the
2257
problem.)
2258
 
2259
@item sseregparm
2260
@cindex @code{sseregparm} attribute
2261
On the Intel 386 with SSE support, the @code{sseregparm} attribute
2262
causes the compiler to pass up to 3 floating point arguments in
2263
SSE registers instead of on the stack.  Functions that take a
2264
variable number of arguments will continue to pass all of their
2265
floating point arguments on the stack.
2266
 
2267
@item force_align_arg_pointer
2268
@cindex @code{force_align_arg_pointer} attribute
2269
On the Intel x86, the @code{force_align_arg_pointer} attribute may be
2270
applied to individual function definitions, generating an alternate
2271
prologue and epilogue that realigns the runtime stack.  This supports
2272
mixing legacy codes that run with a 4-byte aligned stack with modern
2273
codes that keep a 16-byte stack for SSE compatibility.  The alternate
2274
prologue and epilogue are slower and bigger than the regular ones, and
2275
the alternate prologue requires a scratch register; this lowers the
2276
number of registers available if used in conjunction with the
2277
@code{regparm} attribute.  The @code{force_align_arg_pointer}
2278
attribute is incompatible with nested functions; this is considered a
2279
hard error.
2280
 
2281
@item returns_twice
2282
@cindex @code{returns_twice} attribute
2283
The @code{returns_twice} attribute tells the compiler that a function may
2284
return more than one time.  The compiler will ensure that all registers
2285
are dead before calling such a function and will emit a warning about
2286
the variables that may be clobbered after the second return from the
2287
function.  Examples of such functions are @code{setjmp} and @code{vfork}.
2288
The @code{longjmp}-like counterpart of such function, if any, might need
2289
to be marked with the @code{noreturn} attribute.
2290
 
2291
@item saveall
2292
@cindex save all registers on the Blackfin, H8/300, H8/300H, and H8S
2293
Use this attribute on the Blackfin, H8/300, H8/300H, and H8S to indicate that
2294
all registers except the stack pointer should be saved in the prologue
2295
regardless of whether they are used or not.
2296
 
2297
@item section ("@var{section-name}")
2298
@cindex @code{section} function attribute
2299
Normally, the compiler places the code it generates in the @code{text} section.
2300
Sometimes, however, you need additional sections, or you need certain
2301
particular functions to appear in special sections.  The @code{section}
2302
attribute specifies that a function lives in a particular section.
2303
For example, the declaration:
2304
 
2305
@smallexample
2306
extern void foobar (void) __attribute__ ((section ("bar")));
2307
@end smallexample
2308
 
2309
@noindent
2310
puts the function @code{foobar} in the @code{bar} section.
2311
 
2312
Some file formats do not support arbitrary sections so the @code{section}
2313
attribute is not available on all platforms.
2314
If you need to map the entire contents of a module to a particular
2315
section, consider using the facilities of the linker instead.
2316
 
2317
@item sentinel
2318
@cindex @code{sentinel} function attribute
2319
This function attribute ensures that a parameter in a function call is
2320
an explicit @code{NULL}.  The attribute is only valid on variadic
2321
functions.  By default, the sentinel is located at position zero, the
2322
last parameter of the function call.  If an optional integer position
2323
argument P is supplied to the attribute, the sentinel must be located at
2324
position P counting backwards from the end of the argument list.
2325
 
2326
@smallexample
2327
__attribute__ ((sentinel))
2328
is equivalent to
2329
__attribute__ ((sentinel(0)))
2330
@end smallexample
2331
 
2332
The attribute is automatically set with a position of 0 for the built-in
2333
functions @code{execl} and @code{execlp}.  The built-in function
2334
@code{execle} has the attribute set with a position of 1.
2335
 
2336
A valid @code{NULL} in this context is defined as zero with any pointer
2337
type.  If your system defines the @code{NULL} macro with an integer type
2338
then you need to add an explicit cast.  GCC replaces @code{stddef.h}
2339
with a copy that redefines NULL appropriately.
2340
 
2341
The warnings for missing or incorrect sentinels are enabled with
2342
@option{-Wformat}.
2343
 
2344
@item short_call
2345
See long_call/short_call.
2346
 
2347
@item shortcall
2348
See longcall/shortcall.
2349
 
2350
@item signal
2351
@cindex signal handler functions on the AVR processors
2352
Use this attribute on the AVR to indicate that the specified
2353
function is a signal handler.  The compiler will generate function
2354
entry and exit sequences suitable for use in a signal handler when this
2355
attribute is present.  Interrupts will be disabled inside the function.
2356
 
2357
@item sp_switch
2358
Use this attribute on the SH to indicate an @code{interrupt_handler}
2359
function should switch to an alternate stack.  It expects a string
2360
argument that names a global variable holding the address of the
2361
alternate stack.
2362
 
2363
@smallexample
2364
void *alt_stack;
2365
void f () __attribute__ ((interrupt_handler,
2366
                          sp_switch ("alt_stack")));
2367
@end smallexample
2368
 
2369
@item stdcall
2370
@cindex functions that pop the argument stack on the 386
2371
On the Intel 386, the @code{stdcall} attribute causes the compiler to
2372
assume that the called function will pop off the stack space used to
2373
pass arguments, unless it takes a variable number of arguments.
2374
 
2375
@item tiny_data
2376
@cindex tiny data section on the H8/300H and H8S
2377
Use this attribute on the H8/300H and H8S to indicate that the specified
2378
variable should be placed into the tiny data section.
2379
The compiler will generate more efficient code for loads and stores
2380
on data in the tiny data section.  Note the tiny data area is limited to
2381
slightly under 32kbytes of data.
2382
 
2383
@item trap_exit
2384
Use this attribute on the SH for an @code{interrupt_handler} to return using
2385
@code{trapa} instead of @code{rte}.  This attribute expects an integer
2386
argument specifying the trap number to be used.
2387
 
2388
@item unused
2389
@cindex @code{unused} attribute.
2390
This attribute, attached to a function, means that the function is meant
2391
to be possibly unused.  GCC will not produce a warning for this
2392
function.
2393
 
2394
@item used
2395
@cindex @code{used} attribute.
2396
This attribute, attached to a function, means that code must be emitted
2397
for the function even if it appears that the function is not referenced.
2398
This is useful, for example, when the function is referenced only in
2399
inline assembly.
2400
 
2401
@item visibility ("@var{visibility_type}")
2402
@cindex @code{visibility} attribute
2403
This attribute affects the linkage of the declaration to which it is attached.
2404
There are four supported @var{visibility_type} values: default,
2405
hidden, protected or internal visibility.
2406
 
2407
@smallexample
2408
void __attribute__ ((visibility ("protected")))
2409
f () @{ /* @r{Do something.} */; @}
2410
int i __attribute__ ((visibility ("hidden")));
2411
@end smallexample
2412
 
2413
The possible values of @var{visibility_type} correspond to the
2414
visibility settings in the ELF gABI.
2415
 
2416
@table @dfn
2417
@c keep this list of visibilities in alphabetical order.
2418
 
2419
@item default
2420
Default visibility is the normal case for the object file format.
2421
This value is available for the visibility attribute to override other
2422
options that may change the assumed visibility of entities.
2423
 
2424
On ELF, default visibility means that the declaration is visible to other
2425
modules and, in shared libraries, means that the declared entity may be
2426
overridden.
2427
 
2428
On Darwin, default visibility means that the declaration is visible to
2429
other modules.
2430
 
2431
Default visibility corresponds to ``external linkage'' in the language.
2432
 
2433
@item hidden
2434
Hidden visibility indicates that the entity declared will have a new
2435
form of linkage, which we'll call ``hidden linkage''.  Two
2436
declarations of an object with hidden linkage refer to the same object
2437
if they are in the same shared object.
2438
 
2439
@item internal
2440
Internal visibility is like hidden visibility, but with additional
2441
processor specific semantics.  Unless otherwise specified by the
2442
psABI, GCC defines internal visibility to mean that a function is
2443
@emph{never} called from another module.  Compare this with hidden
2444
functions which, while they cannot be referenced directly by other
2445
modules, can be referenced indirectly via function pointers.  By
2446
indicating that a function cannot be called from outside the module,
2447
GCC may for instance omit the load of a PIC register since it is known
2448
that the calling function loaded the correct value.
2449
 
2450
@item protected
2451
Protected visibility is like default visibility except that it
2452
indicates that references within the defining module will bind to the
2453
definition in that module.  That is, the declared entity cannot be
2454
overridden by another module.
2455
 
2456
@end table
2457
 
2458
All visibilities are supported on many, but not all, ELF targets
2459
(supported when the assembler supports the @samp{.visibility}
2460
pseudo-op).  Default visibility is supported everywhere.  Hidden
2461
visibility is supported on Darwin targets.
2462
 
2463
The visibility attribute should be applied only to declarations which
2464
would otherwise have external linkage.  The attribute should be applied
2465
consistently, so that the same entity should not be declared with
2466
different settings of the attribute.
2467
 
2468
In C++, the visibility attribute applies to types as well as functions
2469
and objects, because in C++ types have linkage.  A class must not have
2470
greater visibility than its non-static data member types and bases,
2471
and class members default to the visibility of their class.  Also, a
2472
declaration without explicit visibility is limited to the visibility
2473
of its type.
2474
 
2475
In C++, you can mark member functions and static member variables of a
2476
class with the visibility attribute.  This is useful if if you know a
2477
particular method or static member variable should only be used from
2478
one shared object; then you can mark it hidden while the rest of the
2479
class has default visibility.  Care must be taken to avoid breaking
2480
the One Definition Rule; for example, it is usually not useful to mark
2481
an inline method as hidden without marking the whole class as hidden.
2482
 
2483
A C++ namespace declaration can also have the visibility attribute.
2484
This attribute applies only to the particular namespace body, not to
2485
other definitions of the same namespace; it is equivalent to using
2486
@samp{#pragma GCC visibility} before and after the namespace
2487
definition (@pxref{Visibility Pragmas}).
2488
 
2489
In C++, if a template argument has limited visibility, this
2490
restriction is implicitly propagated to the template instantiation.
2491
Otherwise, template instantiations and specializations default to the
2492
visibility of their template.
2493
 
2494
If both the template and enclosing class have explicit visibility, the
2495
visibility from the template is used.
2496
 
2497
@item warn_unused_result
2498
@cindex @code{warn_unused_result} attribute
2499
The @code{warn_unused_result} attribute causes a warning to be emitted
2500
if a caller of the function with this attribute does not use its
2501
return value.  This is useful for functions where not checking
2502
the result is either a security problem or always a bug, such as
2503
@code{realloc}.
2504
 
2505
@smallexample
2506
int fn () __attribute__ ((warn_unused_result));
2507
int foo ()
2508
@{
2509
  if (fn () < 0) return -1;
2510
  fn ();
2511
  return 0;
2512
@}
2513
@end smallexample
2514
 
2515
results in warning on line 5.
2516
 
2517
@item weak
2518
@cindex @code{weak} attribute
2519
The @code{weak} attribute causes the declaration to be emitted as a weak
2520
symbol rather than a global.  This is primarily useful in defining
2521
library functions which can be overridden in user code, though it can
2522
also be used with non-function declarations.  Weak symbols are supported
2523
for ELF targets, and also for a.out targets when using the GNU assembler
2524
and linker.
2525
 
2526
@item weakref
2527
@itemx weakref ("@var{target}")
2528
@cindex @code{weakref} attribute
2529
The @code{weakref} attribute marks a declaration as a weak reference.
2530
Without arguments, it should be accompanied by an @code{alias} attribute
2531
naming the target symbol.  Optionally, the @var{target} may be given as
2532
an argument to @code{weakref} itself.  In either case, @code{weakref}
2533
implicitly marks the declaration as @code{weak}.  Without a
2534
@var{target}, given as an argument to @code{weakref} or to @code{alias},
2535
@code{weakref} is equivalent to @code{weak}.
2536
 
2537
@smallexample
2538
static int x() __attribute__ ((weakref ("y")));
2539
/* is equivalent to... */
2540
static int x() __attribute__ ((weak, weakref, alias ("y")));
2541
/* and to... */
2542
static int x() __attribute__ ((weakref));
2543
static int x() __attribute__ ((alias ("y")));
2544
@end smallexample
2545
 
2546
A weak reference is an alias that does not by itself require a
2547
definition to be given for the target symbol.  If the target symbol is
2548
only referenced through weak references, then the becomes a @code{weak}
2549
undefined symbol.  If it is directly referenced, however, then such
2550
strong references prevail, and a definition will be required for the
2551
symbol, not necessarily in the same translation unit.
2552
 
2553
The effect is equivalent to moving all references to the alias to a
2554
separate translation unit, renaming the alias to the aliased symbol,
2555
declaring it as weak, compiling the two separate translation units and
2556
performing a reloadable link on them.
2557
 
2558
At present, a declaration to which @code{weakref} is attached can
2559
only be @code{static}.
2560
 
2561
@item externally_visible
2562
@cindex @code{externally_visible} attribute.
2563
This attribute, attached to a global variable or function nullify
2564
effect of @option{-fwhole-program} command line option, so the object
2565
remain visible outside the current compilation unit
2566
 
2567
@end table
2568
 
2569
You can specify multiple attributes in a declaration by separating them
2570
by commas within the double parentheses or by immediately following an
2571
attribute declaration with another attribute declaration.
2572
 
2573
@cindex @code{#pragma}, reason for not using
2574
@cindex pragma, reason for not using
2575
Some people object to the @code{__attribute__} feature, suggesting that
2576
ISO C's @code{#pragma} should be used instead.  At the time
2577
@code{__attribute__} was designed, there were two reasons for not doing
2578
this.
2579
 
2580
@enumerate
2581
@item
2582
It is impossible to generate @code{#pragma} commands from a macro.
2583
 
2584
@item
2585
There is no telling what the same @code{#pragma} might mean in another
2586
compiler.
2587
@end enumerate
2588
 
2589
These two reasons applied to almost any application that might have been
2590
proposed for @code{#pragma}.  It was basically a mistake to use
2591
@code{#pragma} for @emph{anything}.
2592
 
2593
The ISO C99 standard includes @code{_Pragma}, which now allows pragmas
2594
to be generated from macros.  In addition, a @code{#pragma GCC}
2595
namespace is now in use for GCC-specific pragmas.  However, it has been
2596
found convenient to use @code{__attribute__} to achieve a natural
2597
attachment of attributes to their corresponding declarations, whereas
2598
@code{#pragma GCC} is of use for constructs that do not naturally form
2599
part of the grammar.  @xref{Other Directives,,Miscellaneous
2600
Preprocessing Directives, cpp, The GNU C Preprocessor}.
2601
 
2602
@node Attribute Syntax
2603
@section Attribute Syntax
2604
@cindex attribute syntax
2605
 
2606
This section describes the syntax with which @code{__attribute__} may be
2607
used, and the constructs to which attribute specifiers bind, for the C
2608
language.  Some details may vary for C++ and Objective-C@.  Because of
2609
infelicities in the grammar for attributes, some forms described here
2610
may not be successfully parsed in all cases.
2611
 
2612
There are some problems with the semantics of attributes in C++.  For
2613
example, there are no manglings for attributes, although they may affect
2614
code generation, so problems may arise when attributed types are used in
2615
conjunction with templates or overloading.  Similarly, @code{typeid}
2616
does not distinguish between types with different attributes.  Support
2617
for attributes in C++ may be restricted in future to attributes on
2618
declarations only, but not on nested declarators.
2619
 
2620
@xref{Function Attributes}, for details of the semantics of attributes
2621
applying to functions.  @xref{Variable Attributes}, for details of the
2622
semantics of attributes applying to variables.  @xref{Type Attributes},
2623
for details of the semantics of attributes applying to structure, union
2624
and enumerated types.
2625
 
2626
An @dfn{attribute specifier} is of the form
2627
@code{__attribute__ ((@var{attribute-list}))}.  An @dfn{attribute list}
2628
is a possibly empty comma-separated sequence of @dfn{attributes}, where
2629
each attribute is one of the following:
2630
 
2631
@itemize @bullet
2632
@item
2633
Empty.  Empty attributes are ignored.
2634
 
2635
@item
2636
A word (which may be an identifier such as @code{unused}, or a reserved
2637
word such as @code{const}).
2638
 
2639
@item
2640
A word, followed by, in parentheses, parameters for the attribute.
2641
These parameters take one of the following forms:
2642
 
2643
@itemize @bullet
2644
@item
2645
An identifier.  For example, @code{mode} attributes use this form.
2646
 
2647
@item
2648
An identifier followed by a comma and a non-empty comma-separated list
2649
of expressions.  For example, @code{format} attributes use this form.
2650
 
2651
@item
2652
A possibly empty comma-separated list of expressions.  For example,
2653
@code{format_arg} attributes use this form with the list being a single
2654
integer constant expression, and @code{alias} attributes use this form
2655
with the list being a single string constant.
2656
@end itemize
2657
@end itemize
2658
 
2659
An @dfn{attribute specifier list} is a sequence of one or more attribute
2660
specifiers, not separated by any other tokens.
2661
 
2662
In GNU C, an attribute specifier list may appear after the colon following a
2663
label, other than a @code{case} or @code{default} label.  The only
2664
attribute it makes sense to use after a label is @code{unused}.  This
2665
feature is intended for code generated by programs which contains labels
2666
that may be unused but which is compiled with @option{-Wall}.  It would
2667
not normally be appropriate to use in it human-written code, though it
2668
could be useful in cases where the code that jumps to the label is
2669
contained within an @code{#ifdef} conditional.  GNU C++ does not permit
2670
such placement of attribute lists, as it is permissible for a
2671
declaration, which could begin with an attribute list, to be labelled in
2672
C++.  Declarations cannot be labelled in C90 or C99, so the ambiguity
2673
does not arise there.
2674
 
2675
An attribute specifier list may appear as part of a @code{struct},
2676
@code{union} or @code{enum} specifier.  It may go either immediately
2677
after the @code{struct}, @code{union} or @code{enum} keyword, or after
2678
the closing brace.  The former syntax is preferred.
2679
Where attribute specifiers follow the closing brace, they are considered
2680
to relate to the structure, union or enumerated type defined, not to any
2681
enclosing declaration the type specifier appears in, and the type
2682
defined is not complete until after the attribute specifiers.
2683
@c Otherwise, there would be the following problems: a shift/reduce
2684
@c conflict between attributes binding the struct/union/enum and
2685
@c binding to the list of specifiers/qualifiers; and "aligned"
2686
@c attributes could use sizeof for the structure, but the size could be
2687
@c changed later by "packed" attributes.
2688
 
2689
Otherwise, an attribute specifier appears as part of a declaration,
2690
counting declarations of unnamed parameters and type names, and relates
2691
to that declaration (which may be nested in another declaration, for
2692
example in the case of a parameter declaration), or to a particular declarator
2693
within a declaration.  Where an
2694
attribute specifier is applied to a parameter declared as a function or
2695
an array, it should apply to the function or array rather than the
2696
pointer to which the parameter is implicitly converted, but this is not
2697
yet correctly implemented.
2698
 
2699
Any list of specifiers and qualifiers at the start of a declaration may
2700
contain attribute specifiers, whether or not such a list may in that
2701
context contain storage class specifiers.  (Some attributes, however,
2702
are essentially in the nature of storage class specifiers, and only make
2703
sense where storage class specifiers may be used; for example,
2704
@code{section}.)  There is one necessary limitation to this syntax: the
2705
first old-style parameter declaration in a function definition cannot
2706
begin with an attribute specifier, because such an attribute applies to
2707
the function instead by syntax described below (which, however, is not
2708
yet implemented in this case).  In some other cases, attribute
2709
specifiers are permitted by this grammar but not yet supported by the
2710
compiler.  All attribute specifiers in this place relate to the
2711
declaration as a whole.  In the obsolescent usage where a type of
2712
@code{int} is implied by the absence of type specifiers, such a list of
2713
specifiers and qualifiers may be an attribute specifier list with no
2714
other specifiers or qualifiers.
2715
 
2716
At present, the first parameter in a function prototype must have some
2717
type specifier which is not an attribute specifier; this resolves an
2718
ambiguity in the interpretation of @code{void f(int
2719
(__attribute__((foo)) x))}, but is subject to change.  At present, if
2720
the parentheses of a function declarator contain only attributes then
2721
those attributes are ignored, rather than yielding an error or warning
2722
or implying a single parameter of type int, but this is subject to
2723
change.
2724
 
2725
An attribute specifier list may appear immediately before a declarator
2726
(other than the first) in a comma-separated list of declarators in a
2727
declaration of more than one identifier using a single list of
2728
specifiers and qualifiers.  Such attribute specifiers apply
2729
only to the identifier before whose declarator they appear.  For
2730
example, in
2731
 
2732
@smallexample
2733
__attribute__((noreturn)) void d0 (void),
2734
    __attribute__((format(printf, 1, 2))) d1 (const char *, ...),
2735
     d2 (void)
2736
@end smallexample
2737
 
2738
@noindent
2739
the @code{noreturn} attribute applies to all the functions
2740
declared; the @code{format} attribute only applies to @code{d1}.
2741
 
2742
An attribute specifier list may appear immediately before the comma,
2743
@code{=} or semicolon terminating the declaration of an identifier other
2744
than a function definition.  At present, such attribute specifiers apply
2745
to the declared object or function, but in future they may attach to the
2746
outermost adjacent declarator.  In simple cases there is no difference,
2747
but, for example, in
2748
 
2749
@smallexample
2750
void (****f)(void) __attribute__((noreturn));
2751
@end smallexample
2752
 
2753
@noindent
2754
at present the @code{noreturn} attribute applies to @code{f}, which
2755
causes a warning since @code{f} is not a function, but in future it may
2756
apply to the function @code{****f}.  The precise semantics of what
2757
attributes in such cases will apply to are not yet specified.  Where an
2758
assembler name for an object or function is specified (@pxref{Asm
2759
Labels}), at present the attribute must follow the @code{asm}
2760
specification; in future, attributes before the @code{asm} specification
2761
may apply to the adjacent declarator, and those after it to the declared
2762
object or function.
2763
 
2764
An attribute specifier list may, in future, be permitted to appear after
2765
the declarator in a function definition (before any old-style parameter
2766
declarations or the function body).
2767
 
2768
Attribute specifiers may be mixed with type qualifiers appearing inside
2769
the @code{[]} of a parameter array declarator, in the C99 construct by
2770
which such qualifiers are applied to the pointer to which the array is
2771
implicitly converted.  Such attribute specifiers apply to the pointer,
2772
not to the array, but at present this is not implemented and they are
2773
ignored.
2774
 
2775
An attribute specifier list may appear at the start of a nested
2776
declarator.  At present, there are some limitations in this usage: the
2777
attributes correctly apply to the declarator, but for most individual
2778
attributes the semantics this implies are not implemented.
2779
When attribute specifiers follow the @code{*} of a pointer
2780
declarator, they may be mixed with any type qualifiers present.
2781
The following describes the formal semantics of this syntax.  It will make the
2782
most sense if you are familiar with the formal specification of
2783
declarators in the ISO C standard.
2784
 
2785
Consider (as in C99 subclause 6.7.5 paragraph 4) a declaration @code{T
2786
D1}, where @code{T} contains declaration specifiers that specify a type
2787
@var{Type} (such as @code{int}) and @code{D1} is a declarator that
2788
contains an identifier @var{ident}.  The type specified for @var{ident}
2789
for derived declarators whose type does not include an attribute
2790
specifier is as in the ISO C standard.
2791
 
2792
If @code{D1} has the form @code{( @var{attribute-specifier-list} D )},
2793
and the declaration @code{T D} specifies the type
2794
``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then
2795
@code{T D1} specifies the type ``@var{derived-declarator-type-list}
2796
@var{attribute-specifier-list} @var{Type}'' for @var{ident}.
2797
 
2798
If @code{D1} has the form @code{*
2799
@var{type-qualifier-and-attribute-specifier-list} D}, and the
2800
declaration @code{T D} specifies the type
2801
``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then
2802
@code{T D1} specifies the type ``@var{derived-declarator-type-list}
2803
@var{type-qualifier-and-attribute-specifier-list} @var{Type}'' for
2804
@var{ident}.
2805
 
2806
For example,
2807
 
2808
@smallexample
2809
void (__attribute__((noreturn)) ****f) (void);
2810
@end smallexample
2811
 
2812
@noindent
2813
specifies the type ``pointer to pointer to pointer to pointer to
2814
non-returning function returning @code{void}''.  As another example,
2815
 
2816
@smallexample
2817
char *__attribute__((aligned(8))) *f;
2818
@end smallexample
2819
 
2820
@noindent
2821
specifies the type ``pointer to 8-byte-aligned pointer to @code{char}''.
2822
Note again that this does not work with most attributes; for example,
2823
the usage of @samp{aligned} and @samp{noreturn} attributes given above
2824
is not yet supported.
2825
 
2826
For compatibility with existing code written for compiler versions that
2827
did not implement attributes on nested declarators, some laxity is
2828
allowed in the placing of attributes.  If an attribute that only applies
2829
to types is applied to a declaration, it will be treated as applying to
2830
the type of that declaration.  If an attribute that only applies to
2831
declarations is applied to the type of a declaration, it will be treated
2832
as applying to that declaration; and, for compatibility with code
2833
placing the attributes immediately before the identifier declared, such
2834
an attribute applied to a function return type will be treated as
2835
applying to the function type, and such an attribute applied to an array
2836
element type will be treated as applying to the array type.  If an
2837
attribute that only applies to function types is applied to a
2838
pointer-to-function type, it will be treated as applying to the pointer
2839
target type; if such an attribute is applied to a function return type
2840
that is not a pointer-to-function type, it will be treated as applying
2841
to the function type.
2842
 
2843
@node Function Prototypes
2844
@section Prototypes and Old-Style Function Definitions
2845
@cindex function prototype declarations
2846
@cindex old-style function definitions
2847
@cindex promotion of formal parameters
2848
 
2849
GNU C extends ISO C to allow a function prototype to override a later
2850
old-style non-prototype definition.  Consider the following example:
2851
 
2852
@smallexample
2853
/* @r{Use prototypes unless the compiler is old-fashioned.}  */
2854
#ifdef __STDC__
2855
#define P(x) x
2856
#else
2857
#define P(x) ()
2858
#endif
2859
 
2860
/* @r{Prototype function declaration.}  */
2861
int isroot P((uid_t));
2862
 
2863
/* @r{Old-style function definition.}  */
2864
int
2865
isroot (x)   /* @r{??? lossage here ???} */
2866
     uid_t x;
2867
@{
2868
  return x == 0;
2869
@}
2870
@end smallexample
2871
 
2872
Suppose the type @code{uid_t} happens to be @code{short}.  ISO C does
2873
not allow this example, because subword arguments in old-style
2874
non-prototype definitions are promoted.  Therefore in this example the
2875
function definition's argument is really an @code{int}, which does not
2876
match the prototype argument type of @code{short}.
2877
 
2878
This restriction of ISO C makes it hard to write code that is portable
2879
to traditional C compilers, because the programmer does not know
2880
whether the @code{uid_t} type is @code{short}, @code{int}, or
2881
@code{long}.  Therefore, in cases like these GNU C allows a prototype
2882
to override a later old-style definition.  More precisely, in GNU C, a
2883
function prototype argument type overrides the argument type specified
2884
by a later old-style definition if the former type is the same as the
2885
latter type before promotion.  Thus in GNU C the above example is
2886
equivalent to the following:
2887
 
2888
@smallexample
2889
int isroot (uid_t);
2890
 
2891
int
2892
isroot (uid_t x)
2893
@{
2894
  return x == 0;
2895
@}
2896
@end smallexample
2897
 
2898
@noindent
2899
GNU C++ does not support old-style function definitions, so this
2900
extension is irrelevant.
2901
 
2902
@node C++ Comments
2903
@section C++ Style Comments
2904
@cindex //
2905
@cindex C++ comments
2906
@cindex comments, C++ style
2907
 
2908
In GNU C, you may use C++ style comments, which start with @samp{//} and
2909
continue until the end of the line.  Many other C implementations allow
2910
such comments, and they are included in the 1999 C standard.  However,
2911
C++ style comments are not recognized if you specify an @option{-std}
2912
option specifying a version of ISO C before C99, or @option{-ansi}
2913
(equivalent to @option{-std=c89}).
2914
 
2915
@node Dollar Signs
2916
@section Dollar Signs in Identifier Names
2917
@cindex $
2918
@cindex dollar signs in identifier names
2919
@cindex identifier names, dollar signs in
2920
 
2921
In GNU C, you may normally use dollar signs in identifier names.
2922
This is because many traditional C implementations allow such identifiers.
2923
However, dollar signs in identifiers are not supported on a few target
2924
machines, typically because the target assembler does not allow them.
2925
 
2926
@node Character Escapes
2927
@section The Character @key{ESC} in Constants
2928
 
2929
You can use the sequence @samp{\e} in a string or character constant to
2930
stand for the ASCII character @key{ESC}.
2931
 
2932
@node Alignment
2933
@section Inquiring on Alignment of Types or Variables
2934
@cindex alignment
2935
@cindex type alignment
2936
@cindex variable alignment
2937
 
2938
The keyword @code{__alignof__} allows you to inquire about how an object
2939
is aligned, or the minimum alignment usually required by a type.  Its
2940
syntax is just like @code{sizeof}.
2941
 
2942
For example, if the target machine requires a @code{double} value to be
2943
aligned on an 8-byte boundary, then @code{__alignof__ (double)} is 8.
2944
This is true on many RISC machines.  On more traditional machine
2945
designs, @code{__alignof__ (double)} is 4 or even 2.
2946
 
2947
Some machines never actually require alignment; they allow reference to any
2948
data type even at an odd address.  For these machines, @code{__alignof__}
2949
reports the @emph{recommended} alignment of a type.
2950
 
2951
If the operand of @code{__alignof__} is an lvalue rather than a type,
2952
its value is the required alignment for its type, taking into account
2953
any minimum alignment specified with GCC's @code{__attribute__}
2954
extension (@pxref{Variable Attributes}).  For example, after this
2955
declaration:
2956
 
2957
@smallexample
2958
struct foo @{ int x; char y; @} foo1;
2959
@end smallexample
2960
 
2961
@noindent
2962
the value of @code{__alignof__ (foo1.y)} is 1, even though its actual
2963
alignment is probably 2 or 4, the same as @code{__alignof__ (int)}.
2964
 
2965
It is an error to ask for the alignment of an incomplete type.
2966
 
2967
@node Variable Attributes
2968
@section Specifying Attributes of Variables
2969
@cindex attribute of variables
2970
@cindex variable attributes
2971
 
2972
The keyword @code{__attribute__} allows you to specify special
2973
attributes of variables or structure fields.  This keyword is followed
2974
by an attribute specification inside double parentheses.  Some
2975
attributes are currently defined generically for variables.
2976
Other attributes are defined for variables on particular target
2977
systems.  Other attributes are available for functions
2978
(@pxref{Function Attributes}) and for types (@pxref{Type Attributes}).
2979
Other front ends might define more attributes
2980
(@pxref{C++ Extensions,,Extensions to the C++ Language}).
2981
 
2982
You may also specify attributes with @samp{__} preceding and following
2983
each keyword.  This allows you to use them in header files without
2984
being concerned about a possible macro of the same name.  For example,
2985
you may use @code{__aligned__} instead of @code{aligned}.
2986
 
2987
@xref{Attribute Syntax}, for details of the exact syntax for using
2988
attributes.
2989
 
2990
@table @code
2991
@cindex @code{aligned} attribute
2992
@item aligned (@var{alignment})
2993
This attribute specifies a minimum alignment for the variable or
2994
structure field, measured in bytes.  For example, the declaration:
2995
 
2996
@smallexample
2997
int x __attribute__ ((aligned (16))) = 0;
2998
@end smallexample
2999
 
3000
@noindent
3001
causes the compiler to allocate the global variable @code{x} on a
3002
16-byte boundary.  On a 68040, this could be used in conjunction with
3003
an @code{asm} expression to access the @code{move16} instruction which
3004
requires 16-byte aligned operands.
3005
 
3006
You can also specify the alignment of structure fields.  For example, to
3007
create a double-word aligned @code{int} pair, you could write:
3008
 
3009
@smallexample
3010
struct foo @{ int x[2] __attribute__ ((aligned (8))); @};
3011
@end smallexample
3012
 
3013
@noindent
3014
This is an alternative to creating a union with a @code{double} member
3015
that forces the union to be double-word aligned.
3016
 
3017
As in the preceding examples, you can explicitly specify the alignment
3018
(in bytes) that you wish the compiler to use for a given variable or
3019
structure field.  Alternatively, you can leave out the alignment factor
3020
and just ask the compiler to align a variable or field to the maximum
3021
useful alignment for the target machine you are compiling for.  For
3022
example, you could write:
3023
 
3024
@smallexample
3025
short array[3] __attribute__ ((aligned));
3026
@end smallexample
3027
 
3028
Whenever you leave out the alignment factor in an @code{aligned} attribute
3029
specification, the compiler automatically sets the alignment for the declared
3030
variable or field to the largest alignment which is ever used for any data
3031
type on the target machine you are compiling for.  Doing this can often make
3032
copy operations more efficient, because the compiler can use whatever
3033
instructions copy the biggest chunks of memory when performing copies to
3034
or from the variables or fields that you have aligned this way.
3035
 
3036
The @code{aligned} attribute can only increase the alignment; but you
3037
can decrease it by specifying @code{packed} as well.  See below.
3038
 
3039
Note that the effectiveness of @code{aligned} attributes may be limited
3040
by inherent limitations in your linker.  On many systems, the linker is
3041
only able to arrange for variables to be aligned up to a certain maximum
3042
alignment.  (For some linkers, the maximum supported alignment may
3043
be very very small.)  If your linker is only able to align variables
3044
up to a maximum of 8 byte alignment, then specifying @code{aligned(16)}
3045
in an @code{__attribute__} will still only provide you with 8 byte
3046
alignment.  See your linker documentation for further information.
3047
 
3048
@item cleanup (@var{cleanup_function})
3049
@cindex @code{cleanup} attribute
3050
The @code{cleanup} attribute runs a function when the variable goes
3051
out of scope.  This attribute can only be applied to auto function
3052
scope variables; it may not be applied to parameters or variables
3053
with static storage duration.  The function must take one parameter,
3054
a pointer to a type compatible with the variable.  The return value
3055
of the function (if any) is ignored.
3056
 
3057
If @option{-fexceptions} is enabled, then @var{cleanup_function}
3058
will be run during the stack unwinding that happens during the
3059
processing of the exception.  Note that the @code{cleanup} attribute
3060
does not allow the exception to be caught, only to perform an action.
3061
It is undefined what happens if @var{cleanup_function} does not
3062
return normally.
3063
 
3064
@item common
3065
@itemx nocommon
3066
@cindex @code{common} attribute
3067
@cindex @code{nocommon} attribute
3068
@opindex fcommon
3069
@opindex fno-common
3070
The @code{common} attribute requests GCC to place a variable in
3071
``common'' storage.  The @code{nocommon} attribute requests the
3072
opposite---to allocate space for it directly.
3073
 
3074
These attributes override the default chosen by the
3075
@option{-fno-common} and @option{-fcommon} flags respectively.
3076
 
3077
@item deprecated
3078
@cindex @code{deprecated} attribute
3079
The @code{deprecated} attribute results in a warning if the variable
3080
is used anywhere in the source file.  This is useful when identifying
3081
variables that are expected to be removed in a future version of a
3082
program.  The warning also includes the location of the declaration
3083
of the deprecated variable, to enable users to easily find further
3084
information about why the variable is deprecated, or what they should
3085
do instead.  Note that the warning only occurs for uses:
3086
 
3087
@smallexample
3088
extern int old_var __attribute__ ((deprecated));
3089
extern int old_var;
3090
int new_fn () @{ return old_var; @}
3091
@end smallexample
3092
 
3093
results in a warning on line 3 but not line 2.
3094
 
3095
The @code{deprecated} attribute can also be used for functions and
3096
types (@pxref{Function Attributes}, @pxref{Type Attributes}.)
3097
 
3098
@item mode (@var{mode})
3099
@cindex @code{mode} attribute
3100
This attribute specifies the data type for the declaration---whichever
3101
type corresponds to the mode @var{mode}.  This in effect lets you
3102
request an integer or floating point type according to its width.
3103
 
3104
You may also specify a mode of @samp{byte} or @samp{__byte__} to
3105
indicate the mode corresponding to a one-byte integer, @samp{word} or
3106
@samp{__word__} for the mode of a one-word integer, and @samp{pointer}
3107
or @samp{__pointer__} for the mode used to represent pointers.
3108
 
3109
@item packed
3110
@cindex @code{packed} attribute
3111
The @code{packed} attribute specifies that a variable or structure field
3112
should have the smallest possible alignment---one byte for a variable,
3113
and one bit for a field, unless you specify a larger value with the
3114
@code{aligned} attribute.
3115
 
3116
Here is a structure in which the field @code{x} is packed, so that it
3117
immediately follows @code{a}:
3118
 
3119
@smallexample
3120
struct foo
3121
@{
3122
  char a;
3123
  int x[2] __attribute__ ((packed));
3124
@};
3125
@end smallexample
3126
 
3127
@item section ("@var{section-name}")
3128
@cindex @code{section} variable attribute
3129
Normally, the compiler places the objects it generates in sections like
3130
@code{data} and @code{bss}.  Sometimes, however, you need additional sections,
3131
or you need certain particular variables to appear in special sections,
3132
for example to map to special hardware.  The @code{section}
3133
attribute specifies that a variable (or function) lives in a particular
3134
section.  For example, this small program uses several specific section names:
3135
 
3136
@smallexample
3137
struct duart a __attribute__ ((section ("DUART_A"))) = @{ 0 @};
3138
struct duart b __attribute__ ((section ("DUART_B"))) = @{ 0 @};
3139
char stack[10000] __attribute__ ((section ("STACK"))) = @{ 0 @};
3140
int init_data __attribute__ ((section ("INITDATA"))) = 0;
3141
 
3142
main()
3143
@{
3144
  /* @r{Initialize stack pointer} */
3145
  init_sp (stack + sizeof (stack));
3146
 
3147
  /* @r{Initialize initialized data} */
3148
  memcpy (&init_data, &data, &edata - &data);
3149
 
3150
  /* @r{Turn on the serial ports} */
3151
  init_duart (&a);
3152
  init_duart (&b);
3153
@}
3154
@end smallexample
3155
 
3156
@noindent
3157
Use the @code{section} attribute with an @emph{initialized} definition
3158
of a @emph{global} variable, as shown in the example.  GCC issues
3159
a warning and otherwise ignores the @code{section} attribute in
3160
uninitialized variable declarations.
3161
 
3162
You may only use the @code{section} attribute with a fully initialized
3163
global definition because of the way linkers work.  The linker requires
3164
each object be defined once, with the exception that uninitialized
3165
variables tentatively go in the @code{common} (or @code{bss}) section
3166
and can be multiply ``defined''.  You can force a variable to be
3167
initialized with the @option{-fno-common} flag or the @code{nocommon}
3168
attribute.
3169
 
3170
Some file formats do not support arbitrary sections so the @code{section}
3171
attribute is not available on all platforms.
3172
If you need to map the entire contents of a module to a particular
3173
section, consider using the facilities of the linker instead.
3174
 
3175
@item shared
3176
@cindex @code{shared} variable attribute
3177
On Microsoft Windows, in addition to putting variable definitions in a named
3178
section, the section can also be shared among all running copies of an
3179
executable or DLL@.  For example, this small program defines shared data
3180
by putting it in a named section @code{shared} and marking the section
3181
shareable:
3182
 
3183
@smallexample
3184
int foo __attribute__((section ("shared"), shared)) = 0;
3185
 
3186
int
3187
main()
3188
@{
3189
  /* @r{Read and write foo.  All running
3190
     copies see the same value.}  */
3191
  return 0;
3192
@}
3193
@end smallexample
3194
 
3195
@noindent
3196
You may only use the @code{shared} attribute along with @code{section}
3197
attribute with a fully initialized global definition because of the way
3198
linkers work.  See @code{section} attribute for more information.
3199
 
3200
The @code{shared} attribute is only available on Microsoft Windows@.
3201
 
3202
@item tls_model ("@var{tls_model}")
3203
@cindex @code{tls_model} attribute
3204
The @code{tls_model} attribute sets thread-local storage model
3205
(@pxref{Thread-Local}) of a particular @code{__thread} variable,
3206
overriding @option{-ftls-model=} command line switch on a per-variable
3207
basis.
3208
The @var{tls_model} argument should be one of @code{global-dynamic},
3209
@code{local-dynamic}, @code{initial-exec} or @code{local-exec}.
3210
 
3211
Not all targets support this attribute.
3212
 
3213
@item unused
3214
This attribute, attached to a variable, means that the variable is meant
3215
to be possibly unused.  GCC will not produce a warning for this
3216
variable.
3217
 
3218
@item used
3219
This attribute, attached to a variable, means that the variable must be
3220
emitted even if it appears that the variable is not referenced.
3221
 
3222
@item vector_size (@var{bytes})
3223
This attribute specifies the vector size for the variable, measured in
3224
bytes.  For example, the declaration:
3225
 
3226
@smallexample
3227
int foo __attribute__ ((vector_size (16)));
3228
@end smallexample
3229
 
3230
@noindent
3231
causes the compiler to set the mode for @code{foo}, to be 16 bytes,
3232
divided into @code{int} sized units.  Assuming a 32-bit int (a vector of
3233
4 units of 4 bytes), the corresponding mode of @code{foo} will be V4SI@.
3234
 
3235
This attribute is only applicable to integral and float scalars,
3236
although arrays, pointers, and function return values are allowed in
3237
conjunction with this construct.
3238
 
3239
Aggregates with this attribute are invalid, even if they are of the same
3240
size as a corresponding scalar.  For example, the declaration:
3241
 
3242
@smallexample
3243
struct S @{ int a; @};
3244
struct S  __attribute__ ((vector_size (16))) foo;
3245
@end smallexample
3246
 
3247
@noindent
3248
is invalid even if the size of the structure is the same as the size of
3249
the @code{int}.
3250
 
3251
@item selectany
3252
The @code{selectany} attribute causes an initialized global variable to
3253
have link-once semantics.  When multiple definitions of the variable are
3254
encountered by the linker, the first is selected and the remainder are
3255
discarded.  Following usage by the Microsoft compiler, the linker is told
3256
@emph{not} to warn about size or content differences of the multiple
3257
definitions.
3258
 
3259
Although the primary usage of this attribute is for POD types, the
3260
attribute can also be applied to global C++ objects that are initialized
3261
by a constructor.  In this case, the static initialization and destruction
3262
code for the object is emitted in each translation defining the object,
3263
but the calls to the constructor and destructor are protected by a
3264
link-once guard variable.
3265
 
3266
The @code{selectany} attribute is only available on Microsoft Windows
3267
targets.  You can use @code{__declspec (selectany)} as a synonym for
3268
@code{__attribute__ ((selectany))} for compatibility with other
3269
compilers.
3270
 
3271
@item weak
3272
The @code{weak} attribute is described in @xref{Function Attributes}.
3273
 
3274
@item dllimport
3275
The @code{dllimport} attribute is described in @xref{Function Attributes}.
3276
 
3277
@item dllexport
3278
The @code{dllexport} attribute is described in @xref{Function Attributes}.
3279
 
3280
@end table
3281
 
3282
@subsection M32R/D Variable Attributes
3283
 
3284
One attribute is currently defined for the M32R/D@.
3285
 
3286
@table @code
3287
@item model (@var{model-name})
3288
@cindex variable addressability on the M32R/D
3289
Use this attribute on the M32R/D to set the addressability of an object.
3290
The identifier @var{model-name} is one of @code{small}, @code{medium},
3291
or @code{large}, representing each of the code models.
3292
 
3293
Small model objects live in the lower 16MB of memory (so that their
3294
addresses can be loaded with the @code{ld24} instruction).
3295
 
3296
Medium and large model objects may live anywhere in the 32-bit address space
3297
(the compiler will generate @code{seth/add3} instructions to load their
3298
addresses).
3299
@end table
3300
 
3301
@anchor{i386 Variable Attributes}
3302
@subsection i386 Variable Attributes
3303
 
3304
Two attributes are currently defined for i386 configurations:
3305
@code{ms_struct} and @code{gcc_struct}
3306
 
3307
@table @code
3308
@item ms_struct
3309
@itemx gcc_struct
3310
@cindex @code{ms_struct} attribute
3311
@cindex @code{gcc_struct} attribute
3312
 
3313
If @code{packed} is used on a structure, or if bit-fields are used
3314
it may be that the Microsoft ABI packs them differently
3315
than GCC would normally pack them.  Particularly when moving packed
3316
data between functions compiled with GCC and the native Microsoft compiler
3317
(either via function call or as data in a file), it may be necessary to access
3318
either format.
3319
 
3320
Currently @option{-m[no-]ms-bitfields} is provided for the Microsoft Windows X86
3321
compilers to match the native Microsoft compiler.
3322
 
3323
The Microsoft structure layout algorithm is fairly simple with the exception
3324
of the bitfield packing:
3325
 
3326
The padding and alignment of members of structures and whether a bit field
3327
can straddle a storage-unit boundary
3328
 
3329
@enumerate
3330
@item Structure members are stored sequentially in the order in which they are
3331
declared: the first member has the lowest memory address and the last member
3332
the highest.
3333
 
3334
@item Every data object has an alignment-requirement. The alignment-requirement
3335
for all data except structures, unions, and arrays is either the size of the
3336
object or the current packing size (specified with either the aligned attribute
3337
or the pack pragma), whichever is less. For structures,  unions, and arrays,
3338
the alignment-requirement is the largest alignment-requirement of its members.
3339
Every object is allocated an offset so that:
3340
 
3341
offset %  alignment-requirement == 0
3342
 
3343
@item Adjacent bit fields are packed into the same 1-, 2-, or 4-byte allocation
3344
unit if the integral types are the same size and if the next bit field fits
3345
into the current allocation unit without crossing the boundary imposed by the
3346
common alignment requirements of the bit fields.
3347
@end enumerate
3348
 
3349
Handling of zero-length bitfields:
3350
 
3351
MSVC interprets zero-length bitfields in the following ways:
3352
 
3353
@enumerate
3354
@item If a zero-length bitfield is inserted between two bitfields that would
3355
normally be coalesced, the bitfields will not be coalesced.
3356
 
3357
For example:
3358
 
3359
@smallexample
3360
struct
3361
 @{
3362
   unsigned long bf_1 : 12;
3363
   unsigned long : 0;
3364
   unsigned long bf_2 : 12;
3365
 @} t1;
3366
@end smallexample
3367
 
3368
The size of @code{t1} would be 8 bytes with the zero-length bitfield.  If the
3369
zero-length bitfield were removed, @code{t1}'s size would be 4 bytes.
3370
 
3371
@item If a zero-length bitfield is inserted after a bitfield, @code{foo}, and the
3372
alignment of the zero-length bitfield is greater than the member that follows it,
3373
@code{bar}, @code{bar} will be aligned as the type of the zero-length bitfield.
3374
 
3375
For example:
3376
 
3377
@smallexample
3378
struct
3379
 @{
3380
   char foo : 4;
3381
   short : 0;
3382
   char bar;
3383
 @} t2;
3384
 
3385
struct
3386
 @{
3387
   char foo : 4;
3388
   short : 0;
3389
   double bar;
3390
 @} t3;
3391
@end smallexample
3392
 
3393
For @code{t2}, @code{bar} will be placed at offset 2, rather than offset 1.
3394
Accordingly, the size of @code{t2} will be 4.  For @code{t3}, the zero-length
3395
bitfield will not affect the alignment of @code{bar} or, as a result, the size
3396
of the structure.
3397
 
3398
Taking this into account, it is important to note the following:
3399
 
3400
@enumerate
3401
@item If a zero-length bitfield follows a normal bitfield, the type of the
3402
zero-length bitfield may affect the alignment of the structure as whole. For
3403
example, @code{t2} has a size of 4 bytes, since the zero-length bitfield follows a
3404
normal bitfield, and is of type short.
3405
 
3406
@item Even if a zero-length bitfield is not followed by a normal bitfield, it may
3407
still affect the alignment of the structure:
3408
 
3409
@smallexample
3410
struct
3411
 @{
3412
   char foo : 6;
3413
   long : 0;
3414
 @} t4;
3415
@end smallexample
3416
 
3417
Here, @code{t4} will take up 4 bytes.
3418
@end enumerate
3419
 
3420
@item Zero-length bitfields following non-bitfield members are ignored:
3421
 
3422
@smallexample
3423
struct
3424
 @{
3425
   char foo;
3426
   long : 0;
3427
   char bar;
3428
 @} t5;
3429
@end smallexample
3430
 
3431
Here, @code{t5} will take up 2 bytes.
3432
@end enumerate
3433
@end table
3434
 
3435
@subsection PowerPC Variable Attributes
3436
 
3437
Three attributes currently are defined for PowerPC configurations:
3438
@code{altivec}, @code{ms_struct} and @code{gcc_struct}.
3439
 
3440
For full documentation of the struct attributes please see the
3441
documentation in the @xref{i386 Variable Attributes}, section.
3442
 
3443
For documentation of @code{altivec} attribute please see the
3444
documentation in the @xref{PowerPC Type Attributes}, section.
3445
 
3446
@subsection Xstormy16 Variable Attributes
3447
 
3448
One attribute is currently defined for xstormy16 configurations:
3449
@code{below100}
3450
 
3451
@table @code
3452
@item below100
3453
@cindex @code{below100} attribute
3454
 
3455
If a variable has the @code{below100} attribute (@code{BELOW100} is
3456
allowed also), GCC will place the variable in the first 0x100 bytes of
3457
memory and use special opcodes to access it.  Such variables will be
3458
placed in either the @code{.bss_below100} section or the
3459
@code{.data_below100} section.
3460
 
3461
@end table
3462
 
3463
@node Type Attributes
3464
@section Specifying Attributes of Types
3465
@cindex attribute of types
3466
@cindex type attributes
3467
 
3468
The keyword @code{__attribute__} allows you to specify special
3469
attributes of @code{struct} and @code{union} types when you define
3470
such types.  This keyword is followed by an attribute specification
3471
inside double parentheses.  Seven attributes are currently defined for
3472
types: @code{aligned}, @code{packed}, @code{transparent_union},
3473
@code{unused}, @code{deprecated}, @code{visibility}, and
3474
@code{may_alias}.  Other attributes are defined for functions
3475
(@pxref{Function Attributes}) and for variables (@pxref{Variable
3476
Attributes}).
3477
 
3478
You may also specify any one of these attributes with @samp{__}
3479
preceding and following its keyword.  This allows you to use these
3480
attributes in header files without being concerned about a possible
3481
macro of the same name.  For example, you may use @code{__aligned__}
3482
instead of @code{aligned}.
3483
 
3484
You may specify type attributes either in a @code{typedef} declaration
3485
or in an enum, struct or union type declaration or definition.
3486
 
3487
For an enum, struct or union type, you may specify attributes either
3488
between the enum, struct or union tag and the name of the type, or
3489
just past the closing curly brace of the @emph{definition}.  The
3490
former syntax is preferred.
3491
 
3492
@xref{Attribute Syntax}, for details of the exact syntax for using
3493
attributes.
3494
 
3495
@table @code
3496
@cindex @code{aligned} attribute
3497
@item aligned (@var{alignment})
3498
This attribute specifies a minimum alignment (in bytes) for variables
3499
of the specified type.  For example, the declarations:
3500
 
3501
@smallexample
3502
struct S @{ short f[3]; @} __attribute__ ((aligned (8)));
3503
typedef int more_aligned_int __attribute__ ((aligned (8)));
3504
@end smallexample
3505
 
3506
@noindent
3507
force the compiler to insure (as far as it can) that each variable whose
3508
type is @code{struct S} or @code{more_aligned_int} will be allocated and
3509
aligned @emph{at least} on a 8-byte boundary.  On a SPARC, having all
3510
variables of type @code{struct S} aligned to 8-byte boundaries allows
3511
the compiler to use the @code{ldd} and @code{std} (doubleword load and
3512
store) instructions when copying one variable of type @code{struct S} to
3513
another, thus improving run-time efficiency.
3514
 
3515
Note that the alignment of any given @code{struct} or @code{union} type
3516
is required by the ISO C standard to be at least a perfect multiple of
3517
the lowest common multiple of the alignments of all of the members of
3518
the @code{struct} or @code{union} in question.  This means that you @emph{can}
3519
effectively adjust the alignment of a @code{struct} or @code{union}
3520
type by attaching an @code{aligned} attribute to any one of the members
3521
of such a type, but the notation illustrated in the example above is a
3522
more obvious, intuitive, and readable way to request the compiler to
3523
adjust the alignment of an entire @code{struct} or @code{union} type.
3524
 
3525
As in the preceding example, you can explicitly specify the alignment
3526
(in bytes) that you wish the compiler to use for a given @code{struct}
3527
or @code{union} type.  Alternatively, you can leave out the alignment factor
3528
and just ask the compiler to align a type to the maximum
3529
useful alignment for the target machine you are compiling for.  For
3530
example, you could write:
3531
 
3532
@smallexample
3533
struct S @{ short f[3]; @} __attribute__ ((aligned));
3534
@end smallexample
3535
 
3536
Whenever you leave out the alignment factor in an @code{aligned}
3537
attribute specification, the compiler automatically sets the alignment
3538
for the type to the largest alignment which is ever used for any data
3539
type on the target machine you are compiling for.  Doing this can often
3540
make copy operations more efficient, because the compiler can use
3541
whatever instructions copy the biggest chunks of memory when performing
3542
copies to or from the variables which have types that you have aligned
3543
this way.
3544
 
3545
In the example above, if the size of each @code{short} is 2 bytes, then
3546
the size of the entire @code{struct S} type is 6 bytes.  The smallest
3547
power of two which is greater than or equal to that is 8, so the
3548
compiler sets the alignment for the entire @code{struct S} type to 8
3549
bytes.
3550
 
3551
Note that although you can ask the compiler to select a time-efficient
3552
alignment for a given type and then declare only individual stand-alone
3553
objects of that type, the compiler's ability to select a time-efficient
3554
alignment is primarily useful only when you plan to create arrays of
3555
variables having the relevant (efficiently aligned) type.  If you
3556
declare or use arrays of variables of an efficiently-aligned type, then
3557
it is likely that your program will also be doing pointer arithmetic (or
3558
subscripting, which amounts to the same thing) on pointers to the
3559
relevant type, and the code that the compiler generates for these
3560
pointer arithmetic operations will often be more efficient for
3561
efficiently-aligned types than for other types.
3562
 
3563
The @code{aligned} attribute can only increase the alignment; but you
3564
can decrease it by specifying @code{packed} as well.  See below.
3565
 
3566
Note that the effectiveness of @code{aligned} attributes may be limited
3567
by inherent limitations in your linker.  On many systems, the linker is
3568
only able to arrange for variables to be aligned up to a certain maximum
3569
alignment.  (For some linkers, the maximum supported alignment may
3570
be very very small.)  If your linker is only able to align variables
3571
up to a maximum of 8 byte alignment, then specifying @code{aligned(16)}
3572
in an @code{__attribute__} will still only provide you with 8 byte
3573
alignment.  See your linker documentation for further information.
3574
 
3575
@item packed
3576
This attribute, attached to @code{struct} or @code{union} type
3577
definition, specifies that each member (other than zero-width bitfields)
3578
of the structure or union is placed to minimize the memory required.  When
3579
attached to an @code{enum} definition, it indicates that the smallest
3580
integral type should be used.
3581
 
3582
@opindex fshort-enums
3583
Specifying this attribute for @code{struct} and @code{union} types is
3584
equivalent to specifying the @code{packed} attribute on each of the
3585
structure or union members.  Specifying the @option{-fshort-enums}
3586
flag on the line is equivalent to specifying the @code{packed}
3587
attribute on all @code{enum} definitions.
3588
 
3589
In the following example @code{struct my_packed_struct}'s members are
3590
packed closely together, but the internal layout of its @code{s} member
3591
is not packed---to do that, @code{struct my_unpacked_struct} would need to
3592
be packed too.
3593
 
3594
@smallexample
3595
struct my_unpacked_struct
3596
 @{
3597
    char c;
3598
    int i;
3599
 @};
3600
 
3601
struct __attribute__ ((__packed__)) my_packed_struct
3602
  @{
3603
     char c;
3604
     int  i;
3605
     struct my_unpacked_struct s;
3606
  @};
3607
@end smallexample
3608
 
3609
You may only specify this attribute on the definition of a @code{enum},
3610
@code{struct} or @code{union}, not on a @code{typedef} which does not
3611
also define the enumerated type, structure or union.
3612
 
3613
@item transparent_union
3614
This attribute, attached to a @code{union} type definition, indicates
3615
that any function parameter having that union type causes calls to that
3616
function to be treated in a special way.
3617
 
3618
First, the argument corresponding to a transparent union type can be of
3619
any type in the union; no cast is required.  Also, if the union contains
3620
a pointer type, the corresponding argument can be a null pointer
3621
constant or a void pointer expression; and if the union contains a void
3622
pointer type, the corresponding argument can be any pointer expression.
3623
If the union member type is a pointer, qualifiers like @code{const} on
3624
the referenced type must be respected, just as with normal pointer
3625
conversions.
3626
 
3627
Second, the argument is passed to the function using the calling
3628
conventions of the first member of the transparent union, not the calling
3629
conventions of the union itself.  All members of the union must have the
3630
same machine representation; this is necessary for this argument passing
3631
to work properly.
3632
 
3633
Transparent unions are designed for library functions that have multiple
3634
interfaces for compatibility reasons.  For example, suppose the
3635
@code{wait} function must accept either a value of type @code{int *} to
3636
comply with Posix, or a value of type @code{union wait *} to comply with
3637
the 4.1BSD interface.  If @code{wait}'s parameter were @code{void *},
3638
@code{wait} would accept both kinds of arguments, but it would also
3639
accept any other pointer type and this would make argument type checking
3640
less useful.  Instead, @code{<sys/wait.h>} might define the interface
3641
as follows:
3642
 
3643
@smallexample
3644
typedef union
3645
  @{
3646
    int *__ip;
3647
    union wait *__up;
3648
  @} wait_status_ptr_t __attribute__ ((__transparent_union__));
3649
 
3650
pid_t wait (wait_status_ptr_t);
3651
@end smallexample
3652
 
3653
This interface allows either @code{int *} or @code{union wait *}
3654
arguments to be passed, using the @code{int *} calling convention.
3655
The program can call @code{wait} with arguments of either type:
3656
 
3657
@smallexample
3658
int w1 () @{ int w; return wait (&w); @}
3659
int w2 () @{ union wait w; return wait (&w); @}
3660
@end smallexample
3661
 
3662
With this interface, @code{wait}'s implementation might look like this:
3663
 
3664
@smallexample
3665
pid_t wait (wait_status_ptr_t p)
3666
@{
3667
  return waitpid (-1, p.__ip, 0);
3668
@}
3669
@end smallexample
3670
 
3671
@item unused
3672
When attached to a type (including a @code{union} or a @code{struct}),
3673
this attribute means that variables of that type are meant to appear
3674
possibly unused.  GCC will not produce a warning for any variables of
3675
that type, even if the variable appears to do nothing.  This is often
3676
the case with lock or thread classes, which are usually defined and then
3677
not referenced, but contain constructors and destructors that have
3678
nontrivial bookkeeping functions.
3679
 
3680
@item deprecated
3681
The @code{deprecated} attribute results in a warning if the type
3682
is used anywhere in the source file.  This is useful when identifying
3683
types that are expected to be removed in a future version of a program.
3684
If possible, the warning also includes the location of the declaration
3685
of the deprecated type, to enable users to easily find further
3686
information about why the type is deprecated, or what they should do
3687
instead.  Note that the warnings only occur for uses and then only
3688
if the type is being applied to an identifier that itself is not being
3689
declared as deprecated.
3690
 
3691
@smallexample
3692
typedef int T1 __attribute__ ((deprecated));
3693
T1 x;
3694
typedef T1 T2;
3695
T2 y;
3696
typedef T1 T3 __attribute__ ((deprecated));
3697
T3 z __attribute__ ((deprecated));
3698
@end smallexample
3699
 
3700
results in a warning on line 2 and 3 but not lines 4, 5, or 6.  No
3701
warning is issued for line 4 because T2 is not explicitly
3702
deprecated.  Line 5 has no warning because T3 is explicitly
3703
deprecated.  Similarly for line 6.
3704
 
3705
The @code{deprecated} attribute can also be used for functions and
3706
variables (@pxref{Function Attributes}, @pxref{Variable Attributes}.)
3707
 
3708
@item may_alias
3709
Accesses to objects with types with this attribute are not subjected to
3710
type-based alias analysis, but are instead assumed to be able to alias
3711
any other type of objects, just like the @code{char} type.  See
3712
@option{-fstrict-aliasing} for more information on aliasing issues.
3713
 
3714
Example of use:
3715
 
3716
@smallexample
3717
typedef short __attribute__((__may_alias__)) short_a;
3718
 
3719
int
3720
main (void)
3721
@{
3722
  int a = 0x12345678;
3723
  short_a *b = (short_a *) &a;
3724
 
3725
  b[1] = 0;
3726
 
3727
  if (a == 0x12345678)
3728
    abort();
3729
 
3730
  exit(0);
3731
@}
3732
@end smallexample
3733
 
3734
If you replaced @code{short_a} with @code{short} in the variable
3735
declaration, the above program would abort when compiled with
3736
@option{-fstrict-aliasing}, which is on by default at @option{-O2} or
3737
above in recent GCC versions.
3738
 
3739
@item visibility
3740
In C++, attribute visibility (@pxref{Function Attributes}) can also be
3741
applied to class, struct, union and enum types.  Unlike other type
3742
attributes, the attribute must appear between the initial keyword and
3743
the name of the type; it cannot appear after the body of the type.
3744
 
3745
Note that the type visibility is applied to vague linkage entities
3746
associated with the class (vtable, typeinfo node, etc.).  In
3747
particular, if a class is thrown as an exception in one shared object
3748
and caught in another, the class must have default visibility.
3749
Otherwise the two shared objects will be unable to use the same
3750
typeinfo node and exception handling will break.
3751
 
3752
@subsection ARM Type Attributes
3753
 
3754
On those ARM targets that support @code{dllimport} (such as Symbian
3755
OS), you can use the @code{notshared} attribute to indicate that the
3756
virtual table and other similar data for a class should not be
3757
exported from a DLL@.  For example:
3758
 
3759
@smallexample
3760
class __declspec(notshared) C @{
3761
public:
3762
  __declspec(dllimport) C();
3763
  virtual void f();
3764
@}
3765
 
3766
__declspec(dllexport)
3767
C::C() @{@}
3768
@end smallexample
3769
 
3770
In this code, @code{C::C} is exported from the current DLL, but the
3771
virtual table for @code{C} is not exported.  (You can use
3772
@code{__attribute__} instead of @code{__declspec} if you prefer, but
3773
most Symbian OS code uses @code{__declspec}.)
3774
 
3775
@anchor{i386 Type Attributes}
3776
@subsection i386 Type Attributes
3777
 
3778
Two attributes are currently defined for i386 configurations:
3779
@code{ms_struct} and @code{gcc_struct}
3780
 
3781
@item ms_struct
3782
@itemx gcc_struct
3783
@cindex @code{ms_struct}
3784
@cindex @code{gcc_struct}
3785
 
3786
If @code{packed} is used on a structure, or if bit-fields are used
3787
it may be that the Microsoft ABI packs them differently
3788
than GCC would normally pack them.  Particularly when moving packed
3789
data between functions compiled with GCC and the native Microsoft compiler
3790
(either via function call or as data in a file), it may be necessary to access
3791
either format.
3792
 
3793
Currently @option{-m[no-]ms-bitfields} is provided for the Microsoft Windows X86
3794
compilers to match the native Microsoft compiler.
3795
@end table
3796
 
3797
To specify multiple attributes, separate them by commas within the
3798
double parentheses: for example, @samp{__attribute__ ((aligned (16),
3799
packed))}.
3800
 
3801
@anchor{PowerPC Type Attributes}
3802
@subsection PowerPC Type Attributes
3803
 
3804
Three attributes currently are defined for PowerPC configurations:
3805
@code{altivec}, @code{ms_struct} and @code{gcc_struct}.
3806
 
3807
For full documentation of the struct attributes please see the
3808
documentation in the @xref{i386 Type Attributes}, section.
3809
 
3810
The @code{altivec} attribute allows one to declare AltiVec vector data
3811
types supported by the AltiVec Programming Interface Manual.  The
3812
attribute requires an argument to specify one of three vector types:
3813
@code{vector__}, @code{pixel__} (always followed by unsigned short),
3814
and @code{bool__} (always followed by unsigned).
3815
 
3816
@smallexample
3817
__attribute__((altivec(vector__)))
3818
__attribute__((altivec(pixel__))) unsigned short
3819
__attribute__((altivec(bool__))) unsigned
3820
@end smallexample
3821
 
3822
These attributes mainly are intended to support the @code{__vector},
3823
@code{__pixel}, and @code{__bool} AltiVec keywords.
3824
 
3825
@node Inline
3826
@section An Inline Function is As Fast As a Macro
3827
@cindex inline functions
3828
@cindex integrating function code
3829
@cindex open coding
3830
@cindex macros, inline alternative
3831
 
3832
By declaring a function @code{inline}, you can direct GCC to
3833
integrate that function's code into the code for its callers.  This
3834
makes execution faster by eliminating the function-call overhead; in
3835
addition, if any of the actual argument values are constant, their known
3836
values may permit simplifications at compile time so that not all of the
3837
inline function's code needs to be included.  The effect on code size is
3838
less predictable; object code may be larger or smaller with function
3839
inlining, depending on the particular case.  Inlining of functions is an
3840
optimization and it really ``works'' only in optimizing compilation.  If
3841
you don't use @option{-O}, no function is really inline.
3842
 
3843
Inline functions are included in the ISO C99 standard, but there are
3844
currently substantial differences between what GCC implements and what
3845
the ISO C99 standard requires.  GCC will fully support C99 inline
3846
functions in version 4.3.  The traditional GCC handling of inline
3847
functions will still be available with @option{-std=gnu89},
3848
@option{-fgnu89-inline} or when @code{gnu_inline} attribute is present
3849
on all inline declarations.  The preprocessor macros
3850
@code{__GNUC_GNU_INLINE__} and @code{__GNUC_STDC_INLINE__} may be used
3851
to determine the handling of @code{inline} during a particular
3852
compilation (@pxref{Common Predefined Macros,,,cpp,The C
3853
Preprocessor}).
3854
 
3855
To declare a function inline, use the @code{inline} keyword in its
3856
declaration, like this:
3857
 
3858
@smallexample
3859
inline int
3860
inc (int *a)
3861
@{
3862
  (*a)++;
3863
@}
3864
@end smallexample
3865
 
3866
(If you are writing a header file to be included in ISO C programs, write
3867
@code{__inline__} instead of @code{inline}.  @xref{Alternate Keywords}.)
3868
You can also make all ``simple enough'' functions inline with the option
3869
@option{-finline-functions}.
3870
 
3871
@opindex Winline
3872
Note that certain usages in a function definition can make it unsuitable
3873
for inline substitution.  Among these usages are: use of varargs, use of
3874
alloca, use of variable sized data types (@pxref{Variable Length}),
3875
use of computed goto (@pxref{Labels as Values}), use of nonlocal goto,
3876
and nested functions (@pxref{Nested Functions}).  Using @option{-Winline}
3877
will warn when a function marked @code{inline} could not be substituted,
3878
and will give the reason for the failure.
3879
 
3880
Note that in C and Objective-C, unlike C++, the @code{inline} keyword
3881
does not affect the linkage of the function.
3882
 
3883
@cindex automatic @code{inline} for C++ member fns
3884
@cindex @code{inline} automatic for C++ member fns
3885
@cindex member fns, automatically @code{inline}
3886
@cindex C++ member fns, automatically @code{inline}
3887
@opindex fno-default-inline
3888
GCC automatically inlines member functions defined within the class
3889
body of C++ programs even if they are not explicitly declared
3890
@code{inline}.  (You can override this with @option{-fno-default-inline};
3891
@pxref{C++ Dialect Options,,Options Controlling C++ Dialect}.)
3892
 
3893
@cindex inline functions, omission of
3894
@opindex fkeep-inline-functions
3895
When a function is both inline and @code{static}, if all calls to the
3896
function are integrated into the caller, and the function's address is
3897
never used, then the function's own assembler code is never referenced.
3898
In this case, GCC does not actually output assembler code for the
3899
function, unless you specify the option @option{-fkeep-inline-functions}.
3900
Some calls cannot be integrated for various reasons (in particular,
3901
calls that precede the function's definition cannot be integrated, and
3902
neither can recursive calls within the definition).  If there is a
3903
nonintegrated call, then the function is compiled to assembler code as
3904
usual.  The function must also be compiled as usual if the program
3905
refers to its address, because that can't be inlined.
3906
 
3907
@cindex non-static inline function
3908
When an inline function is not @code{static}, then the compiler must assume
3909
that there may be calls from other source files; since a global symbol can
3910
be defined only once in any program, the function must not be defined in
3911
the other source files, so the calls therein cannot be integrated.
3912
Therefore, a non-@code{static} inline function is always compiled on its
3913
own in the usual fashion.
3914
 
3915
If you specify both @code{inline} and @code{extern} in the function
3916
definition, then the definition is used only for inlining.  In no case
3917
is the function compiled on its own, not even if you refer to its
3918
address explicitly.  Such an address becomes an external reference, as
3919
if you had only declared the function, and had not defined it.
3920
 
3921
This combination of @code{inline} and @code{extern} has almost the
3922
effect of a macro.  The way to use it is to put a function definition in
3923
a header file with these keywords, and put another copy of the
3924
definition (lacking @code{inline} and @code{extern}) in a library file.
3925
The definition in the header file will cause most calls to the function
3926
to be inlined.  If any uses of the function remain, they will refer to
3927
the single copy in the library.
3928
 
3929
Since GCC 4.3 will implement ISO C99 semantics for
3930
inline functions, it is simplest to use @code{static inline} only
3931
to guarantee compatibility.  (The
3932
existing semantics will remain available when @option{-std=gnu89} is
3933
specified, but eventually the default will be @option{-std=gnu99};
3934
that will implement the C99 semantics, though it does not do so in
3935
versions of GCC before 4.3.  After the default changes, the existing
3936
semantics will still be available via the @option{-fgnu89-inline}
3937
option or the @code{gnu_inline} function attribute.)
3938
 
3939
GCC does not inline any functions when not optimizing unless you specify
3940
the @samp{always_inline} attribute for the function, like this:
3941
 
3942
@smallexample
3943
/* @r{Prototype.}  */
3944
inline void foo (const char) __attribute__((always_inline));
3945
@end smallexample
3946
 
3947
@node Extended Asm
3948
@section Assembler Instructions with C Expression Operands
3949
@cindex extended @code{asm}
3950
@cindex @code{asm} expressions
3951
@cindex assembler instructions
3952
@cindex registers
3953
 
3954
In an assembler instruction using @code{asm}, you can specify the
3955
operands of the instruction using C expressions.  This means you need not
3956
guess which registers or memory locations will contain the data you want
3957
to use.
3958
 
3959
You must specify an assembler instruction template much like what
3960
appears in a machine description, plus an operand constraint string for
3961
each operand.
3962
 
3963
For example, here is how to use the 68881's @code{fsinx} instruction:
3964
 
3965
@smallexample
3966
asm ("fsinx %1,%0" : "=f" (result) : "f" (angle));
3967
@end smallexample
3968
 
3969
@noindent
3970
Here @code{angle} is the C expression for the input operand while
3971
@code{result} is that of the output operand.  Each has @samp{"f"} as its
3972
operand constraint, saying that a floating point register is required.
3973
The @samp{=} in @samp{=f} indicates that the operand is an output; all
3974
output operands' constraints must use @samp{=}.  The constraints use the
3975
same language used in the machine description (@pxref{Constraints}).
3976
 
3977
Each operand is described by an operand-constraint string followed by
3978
the C expression in parentheses.  A colon separates the assembler
3979
template from the first output operand and another separates the last
3980
output operand from the first input, if any.  Commas separate the
3981
operands within each group.  The total number of operands is currently
3982
limited to 30; this limitation may be lifted in some future version of
3983
GCC@.
3984
 
3985
If there are no output operands but there are input operands, you must
3986
place two consecutive colons surrounding the place where the output
3987
operands would go.
3988
 
3989
As of GCC version 3.1, it is also possible to specify input and output
3990
operands using symbolic names which can be referenced within the
3991
assembler code.  These names are specified inside square brackets
3992
preceding the constraint string, and can be referenced inside the
3993
assembler code using @code{%[@var{name}]} instead of a percentage sign
3994
followed by the operand number.  Using named operands the above example
3995
could look like:
3996
 
3997
@smallexample
3998
asm ("fsinx %[angle],%[output]"
3999
     : [output] "=f" (result)
4000
     : [angle] "f" (angle));
4001
@end smallexample
4002
 
4003
@noindent
4004
Note that the symbolic operand names have no relation whatsoever to
4005
other C identifiers.  You may use any name you like, even those of
4006
existing C symbols, but you must ensure that no two operands within the same
4007
assembler construct use the same symbolic name.
4008
 
4009
Output operand expressions must be lvalues; the compiler can check this.
4010
The input operands need not be lvalues.  The compiler cannot check
4011
whether the operands have data types that are reasonable for the
4012
instruction being executed.  It does not parse the assembler instruction
4013
template and does not know what it means or even whether it is valid
4014
assembler input.  The extended @code{asm} feature is most often used for
4015
machine instructions the compiler itself does not know exist.  If
4016
the output expression cannot be directly addressed (for example, it is a
4017
bit-field), your constraint must allow a register.  In that case, GCC
4018
will use the register as the output of the @code{asm}, and then store
4019
that register into the output.
4020
 
4021
The ordinary output operands must be write-only; GCC will assume that
4022
the values in these operands before the instruction are dead and need
4023
not be generated.  Extended asm supports input-output or read-write
4024
operands.  Use the constraint character @samp{+} to indicate such an
4025
operand and list it with the output operands.  You should only use
4026
read-write operands when the constraints for the operand (or the
4027
operand in which only some of the bits are to be changed) allow a
4028
register.
4029
 
4030
You may, as an alternative, logically split its function into two
4031
separate operands, one input operand and one write-only output
4032
operand.  The connection between them is expressed by constraints
4033
which say they need to be in the same location when the instruction
4034
executes.  You can use the same C expression for both operands, or
4035
different expressions.  For example, here we write the (fictitious)
4036
@samp{combine} instruction with @code{bar} as its read-only source
4037
operand and @code{foo} as its read-write destination:
4038
 
4039
@smallexample
4040
asm ("combine %2,%0" : "=r" (foo) : "0" (foo), "g" (bar));
4041
@end smallexample
4042
 
4043
@noindent
4044
The constraint @samp{"0"} for operand 1 says that it must occupy the
4045
same location as operand 0.  A number in constraint is allowed only in
4046
an input operand and it must refer to an output operand.
4047
 
4048
Only a number in the constraint can guarantee that one operand will be in
4049
the same place as another.  The mere fact that @code{foo} is the value
4050
of both operands is not enough to guarantee that they will be in the
4051
same place in the generated assembler code.  The following would not
4052
work reliably:
4053
 
4054
@smallexample
4055
asm ("combine %2,%0" : "=r" (foo) : "r" (foo), "g" (bar));
4056
@end smallexample
4057
 
4058
Various optimizations or reloading could cause operands 0 and 1 to be in
4059
different registers; GCC knows no reason not to do so.  For example, the
4060
compiler might find a copy of the value of @code{foo} in one register and
4061
use it for operand 1, but generate the output operand 0 in a different
4062
register (copying it afterward to @code{foo}'s own address).  Of course,
4063
since the register for operand 1 is not even mentioned in the assembler
4064
code, the result will not work, but GCC can't tell that.
4065
 
4066
As of GCC version 3.1, one may write @code{[@var{name}]} instead of
4067
the operand number for a matching constraint.  For example:
4068
 
4069
@smallexample
4070
asm ("cmoveq %1,%2,%[result]"
4071
     : [result] "=r"(result)
4072
     : "r" (test), "r"(new), "[result]"(old));
4073
@end smallexample
4074
 
4075
Sometimes you need to make an @code{asm} operand be a specific register,
4076
but there's no matching constraint letter for that register @emph{by
4077
itself}.  To force the operand into that register, use a local variable
4078
for the operand and specify the register in the variable declaration.
4079
@xref{Explicit Reg Vars}.  Then for the @code{asm} operand, use any
4080
register constraint letter that matches the register:
4081
 
4082
@smallexample
4083
register int *p1 asm ("r0") = @dots{};
4084
register int *p2 asm ("r1") = @dots{};
4085
register int *result asm ("r0");
4086
asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2));
4087
@end smallexample
4088
 
4089
@anchor{Example of asm with clobbered asm reg}
4090
In the above example, beware that a register that is call-clobbered by
4091
the target ABI will be overwritten by any function call in the
4092
assignment, including library calls for arithmetic operators.
4093
Assuming it is a call-clobbered register, this may happen to @code{r0}
4094
above by the assignment to @code{p2}.  If you have to use such a
4095
register, use temporary variables for expressions between the register
4096
assignment and use:
4097
 
4098
@smallexample
4099
int t1 = @dots{};
4100
register int *p1 asm ("r0") = @dots{};
4101
register int *p2 asm ("r1") = t1;
4102
register int *result asm ("r0");
4103
asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2));
4104
@end smallexample
4105
 
4106
Some instructions clobber specific hard registers.  To describe this,
4107
write a third colon after the input operands, followed by the names of
4108
the clobbered hard registers (given as strings).  Here is a realistic
4109
example for the VAX:
4110
 
4111
@smallexample
4112
asm volatile ("movc3 %0,%1,%2"
4113
              : /* @r{no outputs} */
4114
              : "g" (from), "g" (to), "g" (count)
4115
              : "r0", "r1", "r2", "r3", "r4", "r5");
4116
@end smallexample
4117
 
4118
You may not write a clobber description in a way that overlaps with an
4119
input or output operand.  For example, you may not have an operand
4120
describing a register class with one member if you mention that register
4121
in the clobber list.  Variables declared to live in specific registers
4122
(@pxref{Explicit Reg Vars}), and used as asm input or output operands must
4123
have no part mentioned in the clobber description.
4124
There is no way for you to specify that an input
4125
operand is modified without also specifying it as an output
4126
operand.  Note that if all the output operands you specify are for this
4127
purpose (and hence unused), you will then also need to specify
4128
@code{volatile} for the @code{asm} construct, as described below, to
4129
prevent GCC from deleting the @code{asm} statement as unused.
4130
 
4131
If you refer to a particular hardware register from the assembler code,
4132
you will probably have to list the register after the third colon to
4133
tell the compiler the register's value is modified.  In some assemblers,
4134
the register names begin with @samp{%}; to produce one @samp{%} in the
4135
assembler code, you must write @samp{%%} in the input.
4136
 
4137
If your assembler instruction can alter the condition code register, add
4138
@samp{cc} to the list of clobbered registers.  GCC on some machines
4139
represents the condition codes as a specific hardware register;
4140
@samp{cc} serves to name this register.  On other machines, the
4141
condition code is handled differently, and specifying @samp{cc} has no
4142
effect.  But it is valid no matter what the machine.
4143
 
4144
If your assembler instructions access memory in an unpredictable
4145
fashion, add @samp{memory} to the list of clobbered registers.  This
4146
will cause GCC to not keep memory values cached in registers across the
4147
assembler instruction and not optimize stores or loads to that memory.
4148
You will also want to add the @code{volatile} keyword if the memory
4149
affected is not listed in the inputs or outputs of the @code{asm}, as
4150
the @samp{memory} clobber does not count as a side-effect of the
4151
@code{asm}.  If you know how large the accessed memory is, you can add
4152
it as input or output but if this is not known, you should add
4153
@samp{memory}.  As an example, if you access ten bytes of a string, you
4154
can use a memory input like:
4155
 
4156
@smallexample
4157
@{"m"( (@{ struct @{ char x[10]; @} *p = (void *)ptr ; *p; @}) )@}.
4158
@end smallexample
4159
 
4160
Note that in the following example the memory input is necessary,
4161
otherwise GCC might optimize the store to @code{x} away:
4162
@smallexample
4163
int foo ()
4164
@{
4165
  int x = 42;
4166
  int *y = &x;
4167
  int result;
4168
  asm ("magic stuff accessing an 'int' pointed to by '%1'"
4169
        "=&d" (r) : "a" (y), "m" (*y));
4170
  return result;
4171
@}
4172
@end smallexample
4173
 
4174
You can put multiple assembler instructions together in a single
4175
@code{asm} template, separated by the characters normally used in assembly
4176
code for the system.  A combination that works in most places is a newline
4177
to break the line, plus a tab character to move to the instruction field
4178
(written as @samp{\n\t}).  Sometimes semicolons can be used, if the
4179
assembler allows semicolons as a line-breaking character.  Note that some
4180
assembler dialects use semicolons to start a comment.
4181
The input operands are guaranteed not to use any of the clobbered
4182
registers, and neither will the output operands' addresses, so you can
4183
read and write the clobbered registers as many times as you like.  Here
4184
is an example of multiple instructions in a template; it assumes the
4185
subroutine @code{_foo} accepts arguments in registers 9 and 10:
4186
 
4187
@smallexample
4188
asm ("movl %0,r9\n\tmovl %1,r10\n\tcall _foo"
4189
     : /* no outputs */
4190
     : "g" (from), "g" (to)
4191
     : "r9", "r10");
4192
@end smallexample
4193
 
4194
Unless an output operand has the @samp{&} constraint modifier, GCC
4195
may allocate it in the same register as an unrelated input operand, on
4196
the assumption the inputs are consumed before the outputs are produced.
4197
This assumption may be false if the assembler code actually consists of
4198
more than one instruction.  In such a case, use @samp{&} for each output
4199
operand that may not overlap an input.  @xref{Modifiers}.
4200
 
4201
If you want to test the condition code produced by an assembler
4202
instruction, you must include a branch and a label in the @code{asm}
4203
construct, as follows:
4204
 
4205
@smallexample
4206
asm ("clr %0\n\tfrob %1\n\tbeq 0f\n\tmov #1,%0\n0:"
4207
     : "g" (result)
4208
     : "g" (input));
4209
@end smallexample
4210
 
4211
@noindent
4212
This assumes your assembler supports local labels, as the GNU assembler
4213
and most Unix assemblers do.
4214
 
4215
Speaking of labels, jumps from one @code{asm} to another are not
4216
supported.  The compiler's optimizers do not know about these jumps, and
4217
therefore they cannot take account of them when deciding how to
4218
optimize.
4219
 
4220
@cindex macros containing @code{asm}
4221
Usually the most convenient way to use these @code{asm} instructions is to
4222
encapsulate them in macros that look like functions.  For example,
4223
 
4224
@smallexample
4225
#define sin(x)       \
4226
(@{ double __value, __arg = (x);   \
4227
   asm ("fsinx %1,%0": "=f" (__value): "f" (__arg));  \
4228
   __value; @})
4229
@end smallexample
4230
 
4231
@noindent
4232
Here the variable @code{__arg} is used to make sure that the instruction
4233
operates on a proper @code{double} value, and to accept only those
4234
arguments @code{x} which can convert automatically to a @code{double}.
4235
 
4236
Another way to make sure the instruction operates on the correct data
4237
type is to use a cast in the @code{asm}.  This is different from using a
4238
variable @code{__arg} in that it converts more different types.  For
4239
example, if the desired type were @code{int}, casting the argument to
4240
@code{int} would accept a pointer with no complaint, while assigning the
4241
argument to an @code{int} variable named @code{__arg} would warn about
4242
using a pointer unless the caller explicitly casts it.
4243
 
4244
If an @code{asm} has output operands, GCC assumes for optimization
4245
purposes the instruction has no side effects except to change the output
4246
operands.  This does not mean instructions with a side effect cannot be
4247
used, but you must be careful, because the compiler may eliminate them
4248
if the output operands aren't used, or move them out of loops, or
4249
replace two with one if they constitute a common subexpression.  Also,
4250
if your instruction does have a side effect on a variable that otherwise
4251
appears not to change, the old value of the variable may be reused later
4252
if it happens to be found in a register.
4253
 
4254
You can prevent an @code{asm} instruction from being deleted
4255
by writing the keyword @code{volatile} after
4256
the @code{asm}.  For example:
4257
 
4258
@smallexample
4259
#define get_and_set_priority(new)              \
4260
(@{ int __old;                                  \
4261
   asm volatile ("get_and_set_priority %0, %1" \
4262
                 : "=g" (__old) : "g" (new));  \
4263
   __old; @})
4264
@end smallexample
4265
 
4266
@noindent
4267
The @code{volatile} keyword indicates that the instruction has
4268
important side-effects.  GCC will not delete a volatile @code{asm} if
4269
it is reachable.  (The instruction can still be deleted if GCC can
4270
prove that control-flow will never reach the location of the
4271
instruction.)  Note that even a volatile @code{asm} instruction
4272
can be moved relative to other code, including across jump
4273
instructions.  For example, on many targets there is a system
4274
register which can be set to control the rounding mode of
4275
floating point operations.  You might try
4276
setting it with a volatile @code{asm}, like this PowerPC example:
4277
 
4278
@smallexample
4279
       asm volatile("mtfsf 255,%0" : : "f" (fpenv));
4280
       sum = x + y;
4281
@end smallexample
4282
 
4283
@noindent
4284
This will not work reliably, as the compiler may move the addition back
4285
before the volatile @code{asm}.  To make it work you need to add an
4286
artificial dependency to the @code{asm} referencing a variable in the code
4287
you don't want moved, for example:
4288
 
4289
@smallexample
4290
    asm volatile ("mtfsf 255,%1" : "=X"(sum): "f"(fpenv));
4291
    sum = x + y;
4292
@end smallexample
4293
 
4294
Similarly, you can't expect a
4295
sequence of volatile @code{asm} instructions to remain perfectly
4296
consecutive.  If you want consecutive output, use a single @code{asm}.
4297
Also, GCC will perform some optimizations across a volatile @code{asm}
4298
instruction; GCC does not ``forget everything'' when it encounters
4299
a volatile @code{asm} instruction the way some other compilers do.
4300
 
4301
An @code{asm} instruction without any output operands will be treated
4302
identically to a volatile @code{asm} instruction.
4303
 
4304
It is a natural idea to look for a way to give access to the condition
4305
code left by the assembler instruction.  However, when we attempted to
4306
implement this, we found no way to make it work reliably.  The problem
4307
is that output operands might need reloading, which would result in
4308
additional following ``store'' instructions.  On most machines, these
4309
instructions would alter the condition code before there was time to
4310
test it.  This problem doesn't arise for ordinary ``test'' and
4311
``compare'' instructions because they don't have any output operands.
4312
 
4313
For reasons similar to those described above, it is not possible to give
4314
an assembler instruction access to the condition code left by previous
4315
instructions.
4316
 
4317
If you are writing a header file that should be includable in ISO C
4318
programs, write @code{__asm__} instead of @code{asm}.  @xref{Alternate
4319
Keywords}.
4320
 
4321
@subsection Size of an @code{asm}
4322
 
4323
Some targets require that GCC track the size of each instruction used in
4324
order to generate correct code.  Because the final length of an
4325
@code{asm} is only known by the assembler, GCC must make an estimate as
4326
to how big it will be.  The estimate is formed by counting the number of
4327
statements in the pattern of the @code{asm} and multiplying that by the
4328
length of the longest instruction on that processor.  Statements in the
4329
@code{asm} are identified by newline characters and whatever statement
4330
separator characters are supported by the assembler; on most processors
4331
this is the `@code{;}' character.
4332
 
4333
Normally, GCC's estimate is perfectly adequate to ensure that correct
4334
code is generated, but it is possible to confuse the compiler if you use
4335
pseudo instructions or assembler macros that expand into multiple real
4336
instructions or if you use assembler directives that expand to more
4337
space in the object file than would be needed for a single instruction.
4338
If this happens then the assembler will produce a diagnostic saying that
4339
a label is unreachable.
4340
 
4341
@subsection i386 floating point asm operands
4342
 
4343
There are several rules on the usage of stack-like regs in
4344
asm_operands insns.  These rules apply only to the operands that are
4345
stack-like regs:
4346
 
4347
@enumerate
4348
@item
4349
Given a set of input regs that die in an asm_operands, it is
4350
necessary to know which are implicitly popped by the asm, and
4351
which must be explicitly popped by gcc.
4352
 
4353
An input reg that is implicitly popped by the asm must be
4354
explicitly clobbered, unless it is constrained to match an
4355
output operand.
4356
 
4357
@item
4358
For any input reg that is implicitly popped by an asm, it is
4359
necessary to know how to adjust the stack to compensate for the pop.
4360
If any non-popped input is closer to the top of the reg-stack than
4361
the implicitly popped reg, it would not be possible to know what the
4362
stack looked like---it's not clear how the rest of the stack ``slides
4363
up''.
4364
 
4365
All implicitly popped input regs must be closer to the top of
4366
the reg-stack than any input that is not implicitly popped.
4367
 
4368
It is possible that if an input dies in an insn, reload might
4369
use the input reg for an output reload.  Consider this example:
4370
 
4371
@smallexample
4372
asm ("foo" : "=t" (a) : "f" (b));
4373
@end smallexample
4374
 
4375
This asm says that input B is not popped by the asm, and that
4376
the asm pushes a result onto the reg-stack, i.e., the stack is one
4377
deeper after the asm than it was before.  But, it is possible that
4378
reload will think that it can use the same reg for both the input and
4379
the output, if input B dies in this insn.
4380
 
4381
If any input operand uses the @code{f} constraint, all output reg
4382
constraints must use the @code{&} earlyclobber.
4383
 
4384
The asm above would be written as
4385
 
4386
@smallexample
4387
asm ("foo" : "=&t" (a) : "f" (b));
4388
@end smallexample
4389
 
4390
@item
4391
Some operands need to be in particular places on the stack.  All
4392
output operands fall in this category---there is no other way to
4393
know which regs the outputs appear in unless the user indicates
4394
this in the constraints.
4395
 
4396
Output operands must specifically indicate which reg an output
4397
appears in after an asm.  @code{=f} is not allowed: the operand
4398
constraints must select a class with a single reg.
4399
 
4400
@item
4401
Output operands may not be ``inserted'' between existing stack regs.
4402
Since no 387 opcode uses a read/write operand, all output operands
4403
are dead before the asm_operands, and are pushed by the asm_operands.
4404
It makes no sense to push anywhere but the top of the reg-stack.
4405
 
4406
Output operands must start at the top of the reg-stack: output
4407
operands may not ``skip'' a reg.
4408
 
4409
@item
4410
Some asm statements may need extra stack space for internal
4411
calculations.  This can be guaranteed by clobbering stack registers
4412
unrelated to the inputs and outputs.
4413
 
4414
@end enumerate
4415
 
4416
Here are a couple of reasonable asms to want to write.  This asm
4417
takes one input, which is internally popped, and produces two outputs.
4418
 
4419
@smallexample
4420
asm ("fsincos" : "=t" (cos), "=u" (sin) : "0" (inp));
4421
@end smallexample
4422
 
4423
This asm takes two inputs, which are popped by the @code{fyl2xp1} opcode,
4424
and replaces them with one output.  The user must code the @code{st(1)}
4425
clobber for reg-stack.c to know that @code{fyl2xp1} pops both inputs.
4426
 
4427
@smallexample
4428
asm ("fyl2xp1" : "=t" (result) : "0" (x), "u" (y) : "st(1)");
4429
@end smallexample
4430
 
4431
@include md.texi
4432
 
4433
@node Asm Labels
4434
@section Controlling Names Used in Assembler Code
4435
@cindex assembler names for identifiers
4436
@cindex names used in assembler code
4437
@cindex identifiers, names in assembler code
4438
 
4439
You can specify the name to be used in the assembler code for a C
4440
function or variable by writing the @code{asm} (or @code{__asm__})
4441
keyword after the declarator as follows:
4442
 
4443
@smallexample
4444
int foo asm ("myfoo") = 2;
4445
@end smallexample
4446
 
4447
@noindent
4448
This specifies that the name to be used for the variable @code{foo} in
4449
the assembler code should be @samp{myfoo} rather than the usual
4450
@samp{_foo}.
4451
 
4452
On systems where an underscore is normally prepended to the name of a C
4453
function or variable, this feature allows you to define names for the
4454
linker that do not start with an underscore.
4455
 
4456
It does not make sense to use this feature with a non-static local
4457
variable since such variables do not have assembler names.  If you are
4458
trying to put the variable in a particular register, see @ref{Explicit
4459
Reg Vars}.  GCC presently accepts such code with a warning, but will
4460
probably be changed to issue an error, rather than a warning, in the
4461
future.
4462
 
4463
You cannot use @code{asm} in this way in a function @emph{definition}; but
4464
you can get the same effect by writing a declaration for the function
4465
before its definition and putting @code{asm} there, like this:
4466
 
4467
@smallexample
4468
extern func () asm ("FUNC");
4469
 
4470
func (x, y)
4471
     int x, y;
4472
/* @r{@dots{}} */
4473
@end smallexample
4474
 
4475
It is up to you to make sure that the assembler names you choose do not
4476
conflict with any other assembler symbols.  Also, you must not use a
4477
register name; that would produce completely invalid assembler code.  GCC
4478
does not as yet have the ability to store static variables in registers.
4479
Perhaps that will be added.
4480
 
4481
@node Explicit Reg Vars
4482
@section Variables in Specified Registers
4483
@cindex explicit register variables
4484
@cindex variables in specified registers
4485
@cindex specified registers
4486
@cindex registers, global allocation
4487
 
4488
GNU C allows you to put a few global variables into specified hardware
4489
registers.  You can also specify the register in which an ordinary
4490
register variable should be allocated.
4491
 
4492
@itemize @bullet
4493
@item
4494
Global register variables reserve registers throughout the program.
4495
This may be useful in programs such as programming language
4496
interpreters which have a couple of global variables that are accessed
4497
very often.
4498
 
4499
@item
4500
Local register variables in specific registers do not reserve the
4501
registers, except at the point where they are used as input or output
4502
operands in an @code{asm} statement and the @code{asm} statement itself is
4503
not deleted.  The compiler's data flow analysis is capable of determining
4504
where the specified registers contain live values, and where they are
4505
available for other uses.  Stores into local register variables may be deleted
4506
when they appear to be dead according to dataflow analysis.  References
4507
to local register variables may be deleted or moved or simplified.
4508
 
4509
These local variables are sometimes convenient for use with the extended
4510
@code{asm} feature (@pxref{Extended Asm}), if you want to write one
4511
output of the assembler instruction directly into a particular register.
4512
(This will work provided the register you specify fits the constraints
4513
specified for that operand in the @code{asm}.)
4514
@end itemize
4515
 
4516
@menu
4517
* Global Reg Vars::
4518
* Local Reg Vars::
4519
@end menu
4520
 
4521
@node Global Reg Vars
4522
@subsection Defining Global Register Variables
4523
@cindex global register variables
4524
@cindex registers, global variables in
4525
 
4526
You can define a global register variable in GNU C like this:
4527
 
4528
@smallexample
4529
register int *foo asm ("a5");
4530
@end smallexample
4531
 
4532
@noindent
4533
Here @code{a5} is the name of the register which should be used.  Choose a
4534
register which is normally saved and restored by function calls on your
4535
machine, so that library routines will not clobber it.
4536
 
4537
Naturally the register name is cpu-dependent, so you would need to
4538
conditionalize your program according to cpu type.  The register
4539
@code{a5} would be a good choice on a 68000 for a variable of pointer
4540
type.  On machines with register windows, be sure to choose a ``global''
4541
register that is not affected magically by the function call mechanism.
4542
 
4543
In addition, operating systems on one type of cpu may differ in how they
4544
name the registers; then you would need additional conditionals.  For
4545
example, some 68000 operating systems call this register @code{%a5}.
4546
 
4547
Eventually there may be a way of asking the compiler to choose a register
4548
automatically, but first we need to figure out how it should choose and
4549
how to enable you to guide the choice.  No solution is evident.
4550
 
4551
Defining a global register variable in a certain register reserves that
4552
register entirely for this use, at least within the current compilation.
4553
The register will not be allocated for any other purpose in the functions
4554
in the current compilation.  The register will not be saved and restored by
4555
these functions.  Stores into this register are never deleted even if they
4556
would appear to be dead, but references may be deleted or moved or
4557
simplified.
4558
 
4559
It is not safe to access the global register variables from signal
4560
handlers, or from more than one thread of control, because the system
4561
library routines may temporarily use the register for other things (unless
4562
you recompile them specially for the task at hand).
4563
 
4564
@cindex @code{qsort}, and global register variables
4565
It is not safe for one function that uses a global register variable to
4566
call another such function @code{foo} by way of a third function
4567
@code{lose} that was compiled without knowledge of this variable (i.e.@: in a
4568
different source file in which the variable wasn't declared).  This is
4569
because @code{lose} might save the register and put some other value there.
4570
For example, you can't expect a global register variable to be available in
4571
the comparison-function that you pass to @code{qsort}, since @code{qsort}
4572
might have put something else in that register.  (If you are prepared to
4573
recompile @code{qsort} with the same global register variable, you can
4574
solve this problem.)
4575
 
4576
If you want to recompile @code{qsort} or other source files which do not
4577
actually use your global register variable, so that they will not use that
4578
register for any other purpose, then it suffices to specify the compiler
4579
option @option{-ffixed-@var{reg}}.  You need not actually add a global
4580
register declaration to their source code.
4581
 
4582
A function which can alter the value of a global register variable cannot
4583
safely be called from a function compiled without this variable, because it
4584
could clobber the value the caller expects to find there on return.
4585
Therefore, the function which is the entry point into the part of the
4586
program that uses the global register variable must explicitly save and
4587
restore the value which belongs to its caller.
4588
 
4589
@cindex register variable after @code{longjmp}
4590
@cindex global register after @code{longjmp}
4591
@cindex value after @code{longjmp}
4592
@findex longjmp
4593
@findex setjmp
4594
On most machines, @code{longjmp} will restore to each global register
4595
variable the value it had at the time of the @code{setjmp}.  On some
4596
machines, however, @code{longjmp} will not change the value of global
4597
register variables.  To be portable, the function that called @code{setjmp}
4598
should make other arrangements to save the values of the global register
4599
variables, and to restore them in a @code{longjmp}.  This way, the same
4600
thing will happen regardless of what @code{longjmp} does.
4601
 
4602
All global register variable declarations must precede all function
4603
definitions.  If such a declaration could appear after function
4604
definitions, the declaration would be too late to prevent the register from
4605
being used for other purposes in the preceding functions.
4606
 
4607
Global register variables may not have initial values, because an
4608
executable file has no means to supply initial contents for a register.
4609
 
4610
On the SPARC, there are reports that g3 @dots{} g7 are suitable
4611
registers, but certain library functions, such as @code{getwd}, as well
4612
as the subroutines for division and remainder, modify g3 and g4.  g1 and
4613
g2 are local temporaries.
4614
 
4615
On the 68000, a2 @dots{} a5 should be suitable, as should d2 @dots{} d7.
4616
Of course, it will not do to use more than a few of those.
4617
 
4618
@node Local Reg Vars
4619
@subsection Specifying Registers for Local Variables
4620
@cindex local variables, specifying registers
4621
@cindex specifying registers for local variables
4622
@cindex registers for local variables
4623
 
4624
You can define a local register variable with a specified register
4625
like this:
4626
 
4627
@smallexample
4628
register int *foo asm ("a5");
4629
@end smallexample
4630
 
4631
@noindent
4632
Here @code{a5} is the name of the register which should be used.  Note
4633
that this is the same syntax used for defining global register
4634
variables, but for a local variable it would appear within a function.
4635
 
4636
Naturally the register name is cpu-dependent, but this is not a
4637
problem, since specific registers are most often useful with explicit
4638
assembler instructions (@pxref{Extended Asm}).  Both of these things
4639
generally require that you conditionalize your program according to
4640
cpu type.
4641
 
4642
In addition, operating systems on one type of cpu may differ in how they
4643
name the registers; then you would need additional conditionals.  For
4644
example, some 68000 operating systems call this register @code{%a5}.
4645
 
4646
Defining such a register variable does not reserve the register; it
4647
remains available for other uses in places where flow control determines
4648
the variable's value is not live.
4649
 
4650
This option does not guarantee that GCC will generate code that has
4651
this variable in the register you specify at all times.  You may not
4652
code an explicit reference to this register in the @emph{assembler
4653
instruction template} part of an @code{asm} statement and assume it will
4654
always refer to this variable.  However, using the variable as an
4655
@code{asm} @emph{operand} guarantees that the specified register is used
4656
for the operand.
4657
 
4658
Stores into local register variables may be deleted when they appear to be dead
4659
according to dataflow analysis.  References to local register variables may
4660
be deleted or moved or simplified.
4661
 
4662
As for global register variables, it's recommended that you choose a
4663
register which is normally saved and restored by function calls on
4664
your machine, so that library routines will not clobber it.  A common
4665
pitfall is to initialize multiple call-clobbered registers with
4666
arbitrary expressions, where a function call or library call for an
4667
arithmetic operator will overwrite a register value from a previous
4668
assignment, for example @code{r0} below:
4669
@smallexample
4670
register int *p1 asm ("r0") = @dots{};
4671
register int *p2 asm ("r1") = @dots{};
4672
@end smallexample
4673
In those cases, a solution is to use a temporary variable for
4674
each arbitrary expression.   @xref{Example of asm with clobbered asm reg}.
4675
 
4676
@node Alternate Keywords
4677
@section Alternate Keywords
4678
@cindex alternate keywords
4679
@cindex keywords, alternate
4680
 
4681
@option{-ansi} and the various @option{-std} options disable certain
4682
keywords.  This causes trouble when you want to use GNU C extensions, or
4683
a general-purpose header file that should be usable by all programs,
4684
including ISO C programs.  The keywords @code{asm}, @code{typeof} and
4685
@code{inline} are not available in programs compiled with
4686
@option{-ansi} or @option{-std} (although @code{inline} can be used in a
4687
program compiled with @option{-std=c99}).  The ISO C99 keyword
4688
@code{restrict} is only available when @option{-std=gnu99} (which will
4689
eventually be the default) or @option{-std=c99} (or the equivalent
4690
@option{-std=iso9899:1999}) is used.
4691
 
4692
The way to solve these problems is to put @samp{__} at the beginning and
4693
end of each problematical keyword.  For example, use @code{__asm__}
4694
instead of @code{asm}, and @code{__inline__} instead of @code{inline}.
4695
 
4696
Other C compilers won't accept these alternative keywords; if you want to
4697
compile with another compiler, you can define the alternate keywords as
4698
macros to replace them with the customary keywords.  It looks like this:
4699
 
4700
@smallexample
4701
#ifndef __GNUC__
4702
#define __asm__ asm
4703
#endif
4704
@end smallexample
4705
 
4706
@findex __extension__
4707
@opindex pedantic
4708
@option{-pedantic} and other options cause warnings for many GNU C extensions.
4709
You can
4710
prevent such warnings within one expression by writing
4711
@code{__extension__} before the expression.  @code{__extension__} has no
4712
effect aside from this.
4713
 
4714
@node Incomplete Enums
4715
@section Incomplete @code{enum} Types
4716
 
4717
You can define an @code{enum} tag without specifying its possible values.
4718
This results in an incomplete type, much like what you get if you write
4719
@code{struct foo} without describing the elements.  A later declaration
4720
which does specify the possible values completes the type.
4721
 
4722
You can't allocate variables or storage using the type while it is
4723
incomplete.  However, you can work with pointers to that type.
4724
 
4725
This extension may not be very useful, but it makes the handling of
4726
@code{enum} more consistent with the way @code{struct} and @code{union}
4727
are handled.
4728
 
4729
This extension is not supported by GNU C++.
4730
 
4731
@node Function Names
4732
@section Function Names as Strings
4733
@cindex @code{__func__} identifier
4734
@cindex @code{__FUNCTION__} identifier
4735
@cindex @code{__PRETTY_FUNCTION__} identifier
4736
 
4737
GCC provides three magic variables which hold the name of the current
4738
function, as a string.  The first of these is @code{__func__}, which
4739
is part of the C99 standard:
4740
 
4741
@display
4742
The identifier @code{__func__} is implicitly declared by the translator
4743
as if, immediately following the opening brace of each function
4744
definition, the declaration
4745
 
4746
@smallexample
4747
static const char __func__[] = "function-name";
4748
@end smallexample
4749
 
4750
appeared, where function-name is the name of the lexically-enclosing
4751
function.  This name is the unadorned name of the function.
4752
@end display
4753
 
4754
@code{__FUNCTION__} is another name for @code{__func__}.  Older
4755
versions of GCC recognize only this name.  However, it is not
4756
standardized.  For maximum portability, we recommend you use
4757
@code{__func__}, but provide a fallback definition with the
4758
preprocessor:
4759
 
4760
@smallexample
4761
#if __STDC_VERSION__ < 199901L
4762
# if __GNUC__ >= 2
4763
#  define __func__ __FUNCTION__
4764
# else
4765
#  define __func__ "<unknown>"
4766
# endif
4767
#endif
4768
@end smallexample
4769
 
4770
In C, @code{__PRETTY_FUNCTION__} is yet another name for
4771
@code{__func__}.  However, in C++, @code{__PRETTY_FUNCTION__} contains
4772
the type signature of the function as well as its bare name.  For
4773
example, this program:
4774
 
4775
@smallexample
4776
extern "C" @{
4777
extern int printf (char *, ...);
4778
@}
4779
 
4780
class a @{
4781
 public:
4782
  void sub (int i)
4783
    @{
4784
      printf ("__FUNCTION__ = %s\n", __FUNCTION__);
4785
      printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__);
4786
    @}
4787
@};
4788
 
4789
int
4790
main (void)
4791
@{
4792
  a ax;
4793
  ax.sub (0);
4794
  return 0;
4795
@}
4796
@end smallexample
4797
 
4798
@noindent
4799
gives this output:
4800
 
4801
@smallexample
4802
__FUNCTION__ = sub
4803
__PRETTY_FUNCTION__ = void a::sub(int)
4804
@end smallexample
4805
 
4806
These identifiers are not preprocessor macros.  In GCC 3.3 and
4807
earlier, in C only, @code{__FUNCTION__} and @code{__PRETTY_FUNCTION__}
4808
were treated as string literals; they could be used to initialize
4809
@code{char} arrays, and they could be concatenated with other string
4810
literals.  GCC 3.4 and later treat them as variables, like
4811
@code{__func__}.  In C++, @code{__FUNCTION__} and
4812
@code{__PRETTY_FUNCTION__} have always been variables.
4813
 
4814
@node Return Address
4815
@section Getting the Return or Frame Address of a Function
4816
 
4817
These functions may be used to get information about the callers of a
4818
function.
4819
 
4820
@deftypefn {Built-in Function} {void *} __builtin_return_address (unsigned int @var{level})
4821
This function returns the return address of the current function, or of
4822
one of its callers.  The @var{level} argument is number of frames to
4823
scan up the call stack.  A value of @code{0} yields the return address
4824
of the current function, a value of @code{1} yields the return address
4825
of the caller of the current function, and so forth.  When inlining
4826
the expected behavior is that the function will return the address of
4827
the function that will be returned to.  To work around this behavior use
4828
the @code{noinline} function attribute.
4829
 
4830
The @var{level} argument must be a constant integer.
4831
 
4832
On some machines it may be impossible to determine the return address of
4833
any function other than the current one; in such cases, or when the top
4834
of the stack has been reached, this function will return @code{0} or a
4835
random value.  In addition, @code{__builtin_frame_address} may be used
4836
to determine if the top of the stack has been reached.
4837
 
4838
This function should only be used with a nonzero argument for debugging
4839
purposes.
4840
@end deftypefn
4841
 
4842
@deftypefn {Built-in Function} {void *} __builtin_frame_address (unsigned int @var{level})
4843
This function is similar to @code{__builtin_return_address}, but it
4844
returns the address of the function frame rather than the return address
4845
of the function.  Calling @code{__builtin_frame_address} with a value of
4846
@code{0} yields the frame address of the current function, a value of
4847
@code{1} yields the frame address of the caller of the current function,
4848
and so forth.
4849
 
4850
The frame is the area on the stack which holds local variables and saved
4851
registers.  The frame address is normally the address of the first word
4852
pushed on to the stack by the function.  However, the exact definition
4853
depends upon the processor and the calling convention.  If the processor
4854
has a dedicated frame pointer register, and the function has a frame,
4855
then @code{__builtin_frame_address} will return the value of the frame
4856
pointer register.
4857
 
4858
On some machines it may be impossible to determine the frame address of
4859
any function other than the current one; in such cases, or when the top
4860
of the stack has been reached, this function will return @code{0} if
4861
the first frame pointer is properly initialized by the startup code.
4862
 
4863
This function should only be used with a nonzero argument for debugging
4864
purposes.
4865
@end deftypefn
4866
 
4867
@node Vector Extensions
4868
@section Using vector instructions through built-in functions
4869
 
4870
On some targets, the instruction set contains SIMD vector instructions that
4871
operate on multiple values contained in one large register at the same time.
4872
For example, on the i386 the MMX, 3Dnow! and SSE extensions can be used
4873
this way.
4874
 
4875
The first step in using these extensions is to provide the necessary data
4876
types.  This should be done using an appropriate @code{typedef}:
4877
 
4878
@smallexample
4879
typedef int v4si __attribute__ ((vector_size (16)));
4880
@end smallexample
4881
 
4882
The @code{int} type specifies the base type, while the attribute specifies
4883
the vector size for the variable, measured in bytes.  For example, the
4884
declaration above causes the compiler to set the mode for the @code{v4si}
4885
type to be 16 bytes wide and divided into @code{int} sized units.  For
4886
a 32-bit @code{int} this means a vector of 4 units of 4 bytes, and the
4887
corresponding mode of @code{foo} will be @acronym{V4SI}.
4888
 
4889
The @code{vector_size} attribute is only applicable to integral and
4890
float scalars, although arrays, pointers, and function return values
4891
are allowed in conjunction with this construct.
4892
 
4893
All the basic integer types can be used as base types, both as signed
4894
and as unsigned: @code{char}, @code{short}, @code{int}, @code{long},
4895
@code{long long}.  In addition, @code{float} and @code{double} can be
4896
used to build floating-point vector types.
4897
 
4898
Specifying a combination that is not valid for the current architecture
4899
will cause GCC to synthesize the instructions using a narrower mode.
4900
For example, if you specify a variable of type @code{V4SI} and your
4901
architecture does not allow for this specific SIMD type, GCC will
4902
produce code that uses 4 @code{SIs}.
4903
 
4904
The types defined in this manner can be used with a subset of normal C
4905
operations.  Currently, GCC will allow using the following operators
4906
on these types: @code{+, -, *, /, unary minus, ^, |, &, ~}@.
4907
 
4908
The operations behave like C++ @code{valarrays}.  Addition is defined as
4909
the addition of the corresponding elements of the operands.  For
4910
example, in the code below, each of the 4 elements in @var{a} will be
4911
added to the corresponding 4 elements in @var{b} and the resulting
4912
vector will be stored in @var{c}.
4913
 
4914
@smallexample
4915
typedef int v4si __attribute__ ((vector_size (16)));
4916
 
4917
v4si a, b, c;
4918
 
4919
c = a + b;
4920
@end smallexample
4921
 
4922
Subtraction, multiplication, division, and the logical operations
4923
operate in a similar manner.  Likewise, the result of using the unary
4924
minus or complement operators on a vector type is a vector whose
4925
elements are the negative or complemented values of the corresponding
4926
elements in the operand.
4927
 
4928
You can declare variables and use them in function calls and returns, as
4929
well as in assignments and some casts.  You can specify a vector type as
4930
a return type for a function.  Vector types can also be used as function
4931
arguments.  It is possible to cast from one vector type to another,
4932
provided they are of the same size (in fact, you can also cast vectors
4933
to and from other datatypes of the same size).
4934
 
4935
You cannot operate between vectors of different lengths or different
4936
signedness without a cast.
4937
 
4938
A port that supports hardware vector operations, usually provides a set
4939
of built-in functions that can be used to operate on vectors.  For
4940
example, a function to add two vectors and multiply the result by a
4941
third could look like this:
4942
 
4943
@smallexample
4944
v4si f (v4si a, v4si b, v4si c)
4945
@{
4946
  v4si tmp = __builtin_addv4si (a, b);
4947
  return __builtin_mulv4si (tmp, c);
4948
@}
4949
 
4950
@end smallexample
4951
 
4952
@node Offsetof
4953
@section Offsetof
4954
@findex __builtin_offsetof
4955
 
4956
GCC implements for both C and C++ a syntactic extension to implement
4957
the @code{offsetof} macro.
4958
 
4959
@smallexample
4960
primary:
4961
        "__builtin_offsetof" "(" @code{typename} "," offsetof_member_designator ")"
4962
 
4963
offsetof_member_designator:
4964
          @code{identifier}
4965
        | offsetof_member_designator "." @code{identifier}
4966
        | offsetof_member_designator "[" @code{expr} "]"
4967
@end smallexample
4968
 
4969
This extension is sufficient such that
4970
 
4971
@smallexample
4972
#define offsetof(@var{type}, @var{member})  __builtin_offsetof (@var{type}, @var{member})
4973
@end smallexample
4974
 
4975
is a suitable definition of the @code{offsetof} macro.  In C++, @var{type}
4976
may be dependent.  In either case, @var{member} may consist of a single
4977
identifier, or a sequence of member accesses and array references.
4978
 
4979
@node Atomic Builtins
4980
@section Built-in functions for atomic memory access
4981
 
4982
The following builtins are intended to be compatible with those described
4983
in the @cite{Intel Itanium Processor-specific Application Binary Interface},
4984
section 7.4.  As such, they depart from the normal GCC practice of using
4985
the ``__builtin_'' prefix, and further that they are overloaded such that
4986
they work on multiple types.
4987
 
4988
The definition given in the Intel documentation allows only for the use of
4989
the types @code{int}, @code{long}, @code{long long} as well as their unsigned
4990
counterparts.  GCC will allow any integral scalar or pointer type that is
4991
1, 2, 4 or 8 bytes in length.
4992
 
4993
Not all operations are supported by all target processors.  If a particular
4994
operation cannot be implemented on the target processor, a warning will be
4995
generated and a call an external function will be generated.  The external
4996
function will carry the same name as the builtin, with an additional suffix
4997
@samp{_@var{n}} where @var{n} is the size of the data type.
4998
 
4999
@c ??? Should we have a mechanism to suppress this warning?  This is almost
5000
@c useful for implementing the operation under the control of an external
5001
@c mutex.
5002
 
5003
In most cases, these builtins are considered a @dfn{full barrier}.  That is,
5004
no memory operand will be moved across the operation, either forward or
5005
backward.  Further, instructions will be issued as necessary to prevent the
5006
processor from speculating loads across the operation and from queuing stores
5007
after the operation.
5008
 
5009
All of the routines are are described in the Intel documentation to take
5010
``an optional list of variables protected by the memory barrier''.  It's
5011
not clear what is meant by that; it could mean that @emph{only} the
5012
following variables are protected, or it could mean that these variables
5013
should in addition be protected.  At present GCC ignores this list and
5014
protects all variables which are globally accessible.  If in the future
5015
we make some use of this list, an empty list will continue to mean all
5016
globally accessible variables.
5017
 
5018
@table @code
5019
@item @var{type} __sync_fetch_and_add (@var{type} *ptr, @var{type} value, ...)
5020
@itemx @var{type} __sync_fetch_and_sub (@var{type} *ptr, @var{type} value, ...)
5021
@itemx @var{type} __sync_fetch_and_or (@var{type} *ptr, @var{type} value, ...)
5022
@itemx @var{type} __sync_fetch_and_and (@var{type} *ptr, @var{type} value, ...)
5023
@itemx @var{type} __sync_fetch_and_xor (@var{type} *ptr, @var{type} value, ...)
5024
@itemx @var{type} __sync_fetch_and_nand (@var{type} *ptr, @var{type} value, ...)
5025
@findex __sync_fetch_and_add
5026
@findex __sync_fetch_and_sub
5027
@findex __sync_fetch_and_or
5028
@findex __sync_fetch_and_and
5029
@findex __sync_fetch_and_xor
5030
@findex __sync_fetch_and_nand
5031
These builtins perform the operation suggested by the name, and
5032
returns the value that had previously been in memory.  That is,
5033
 
5034
@smallexample
5035
@{ tmp = *ptr; *ptr @var{op}= value; return tmp; @}
5036
@{ tmp = *ptr; *ptr = ~tmp & value; return tmp; @}   // nand
5037
@end smallexample
5038
 
5039
@item @var{type} __sync_add_and_fetch (@var{type} *ptr, @var{type} value, ...)
5040
@itemx @var{type} __sync_sub_and_fetch (@var{type} *ptr, @var{type} value, ...)
5041
@itemx @var{type} __sync_or_and_fetch (@var{type} *ptr, @var{type} value, ...)
5042
@itemx @var{type} __sync_and_and_fetch (@var{type} *ptr, @var{type} value, ...)
5043
@itemx @var{type} __sync_xor_and_fetch (@var{type} *ptr, @var{type} value, ...)
5044
@itemx @var{type} __sync_nand_and_fetch (@var{type} *ptr, @var{type} value, ...)
5045
@findex __sync_add_and_fetch
5046
@findex __sync_sub_and_fetch
5047
@findex __sync_or_and_fetch
5048
@findex __sync_and_and_fetch
5049
@findex __sync_xor_and_fetch
5050
@findex __sync_nand_and_fetch
5051
These builtins perform the operation suggested by the name, and
5052
return the new value.  That is,
5053
 
5054
@smallexample
5055
@{ *ptr @var{op}= value; return *ptr; @}
5056
@{ *ptr = ~*ptr & value; return *ptr; @}   // nand
5057
@end smallexample
5058
 
5059
@item bool __sync_bool_compare_and_swap (@var{type} *ptr, @var{type} oldval @var{type} newval, ...)
5060
@itemx @var{type} __sync_val_compare_and_swap (@var{type} *ptr, @var{type} oldval @var{type} newval, ...)
5061
@findex __sync_bool_compare_and_swap
5062
@findex __sync_val_compare_and_swap
5063
These builtins perform an atomic compare and swap.  That is, if the current
5064
value of @code{*@var{ptr}} is @var{oldval}, then write @var{newval} into
5065
@code{*@var{ptr}}.
5066
 
5067
The ``bool'' version returns true if the comparison is successful and
5068
@var{newval} was written.  The ``val'' version returns the contents
5069
of @code{*@var{ptr}} before the operation.
5070
 
5071
@item __sync_synchronize (...)
5072
@findex __sync_synchronize
5073
This builtin issues a full memory barrier.
5074
 
5075
@item @var{type} __sync_lock_test_and_set (@var{type} *ptr, @var{type} value, ...)
5076
@findex __sync_lock_test_and_set
5077
This builtin, as described by Intel, is not a traditional test-and-set
5078
operation, but rather an atomic exchange operation.  It writes @var{value}
5079
into @code{*@var{ptr}}, and returns the previous contents of
5080
@code{*@var{ptr}}.
5081
 
5082
Many targets have only minimal support for such locks, and do not support
5083
a full exchange operation.  In this case, a target may support reduced
5084
functionality here by which the @emph{only} valid value to store is the
5085
immediate constant 1.  The exact value actually stored in @code{*@var{ptr}}
5086
is implementation defined.
5087
 
5088
This builtin is not a full barrier, but rather an @dfn{acquire barrier}.
5089
This means that references after the builtin cannot move to (or be
5090
speculated to) before the builtin, but previous memory stores may not
5091
be globally visible yet, and previous memory loads may not yet be
5092
satisfied.
5093
 
5094
@item void __sync_lock_release (@var{type} *ptr, ...)
5095
@findex __sync_lock_release
5096
This builtin releases the lock acquired by @code{__sync_lock_test_and_set}.
5097
Normally this means writing the constant 0 to @code{*@var{ptr}}.
5098
 
5099
This builtin is not a full barrier, but rather a @dfn{release barrier}.
5100
This means that all previous memory stores are globally visible, and all
5101
previous memory loads have been satisfied, but following memory reads
5102
are not prevented from being speculated to before the barrier.
5103
@end table
5104
 
5105
@node Object Size Checking
5106
@section Object Size Checking Builtins
5107
@findex __builtin_object_size
5108
@findex __builtin___memcpy_chk
5109
@findex __builtin___mempcpy_chk
5110
@findex __builtin___memmove_chk
5111
@findex __builtin___memset_chk
5112
@findex __builtin___strcpy_chk
5113
@findex __builtin___stpcpy_chk
5114
@findex __builtin___strncpy_chk
5115
@findex __builtin___strcat_chk
5116
@findex __builtin___strncat_chk
5117
@findex __builtin___sprintf_chk
5118
@findex __builtin___snprintf_chk
5119
@findex __builtin___vsprintf_chk
5120
@findex __builtin___vsnprintf_chk
5121
@findex __builtin___printf_chk
5122
@findex __builtin___vprintf_chk
5123
@findex __builtin___fprintf_chk
5124
@findex __builtin___vfprintf_chk
5125
 
5126
GCC implements a limited buffer overflow protection mechanism
5127
that can prevent some buffer overflow attacks.
5128
 
5129
@deftypefn {Built-in Function} {size_t} __builtin_object_size (void * @var{ptr}, int @var{type})
5130
is a built-in construct that returns a constant number of bytes from
5131
@var{ptr} to the end of the object @var{ptr} pointer points to
5132
(if known at compile time).  @code{__builtin_object_size} never evaluates
5133
its arguments for side-effects.  If there are any side-effects in them, it
5134
returns @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0}
5135
for @var{type} 2 or 3.  If there are multiple objects @var{ptr} can
5136
point to and all of them are known at compile time, the returned number
5137
is the maximum of remaining byte counts in those objects if @var{type} & 2 is
5138
 
5139
@var{ptr} points to at compile time, @code{__builtin_object_size} should
5140
return @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0}
5141
for @var{type} 2 or 3.
5142
 
5143
@var{type} is an integer constant from 0 to 3.  If the least significant
5144
bit is clear, objects are whole variables, if it is set, a closest
5145
surrounding subobject is considered the object a pointer points to.
5146
The second bit determines if maximum or minimum of remaining bytes
5147
is computed.
5148
 
5149
@smallexample
5150
struct V @{ char buf1[10]; int b; char buf2[10]; @} var;
5151
char *p = &var.buf1[1], *q = &var.b;
5152
 
5153
/* Here the object p points to is var.  */
5154
assert (__builtin_object_size (p, 0) == sizeof (var) - 1);
5155
/* The subobject p points to is var.buf1.  */
5156
assert (__builtin_object_size (p, 1) == sizeof (var.buf1) - 1);
5157
/* The object q points to is var.  */
5158
assert (__builtin_object_size (q, 0)
5159
        == (char *) (&var + 1) - (char *) &var.b);
5160
/* The subobject q points to is var.b.  */
5161
assert (__builtin_object_size (q, 1) == sizeof (var.b));
5162
@end smallexample
5163
@end deftypefn
5164
 
5165
There are built-in functions added for many common string operation
5166
functions, e.g. for @code{memcpy} @code{__builtin___memcpy_chk}
5167
built-in is provided.  This built-in has an additional last argument,
5168
which is the number of bytes remaining in object the @var{dest}
5169
argument points to or @code{(size_t) -1} if the size is not known.
5170
 
5171
The built-in functions are optimized into the normal string functions
5172
like @code{memcpy} if the last argument is @code{(size_t) -1} or if
5173
it is known at compile time that the destination object will not
5174
be overflown.  If the compiler can determine at compile time the
5175
object will be always overflown, it issues a warning.
5176
 
5177
The intended use can be e.g.
5178
 
5179
@smallexample
5180
#undef memcpy
5181
#define bos0(dest) __builtin_object_size (dest, 0)
5182
#define memcpy(dest, src, n) \
5183
  __builtin___memcpy_chk (dest, src, n, bos0 (dest))
5184
 
5185
char *volatile p;
5186
char buf[10];
5187
/* It is unknown what object p points to, so this is optimized
5188
   into plain memcpy - no checking is possible.  */
5189
memcpy (p, "abcde", n);
5190
/* Destination is known and length too.  It is known at compile
5191
   time there will be no overflow.  */
5192
memcpy (&buf[5], "abcde", 5);
5193
/* Destination is known, but the length is not known at compile time.
5194
   This will result in __memcpy_chk call that can check for overflow
5195
   at runtime.  */
5196
memcpy (&buf[5], "abcde", n);
5197
/* Destination is known and it is known at compile time there will
5198
   be overflow.  There will be a warning and __memcpy_chk call that
5199
   will abort the program at runtime.  */
5200
memcpy (&buf[6], "abcde", 5);
5201
@end smallexample
5202
 
5203
Such built-in functions are provided for @code{memcpy}, @code{mempcpy},
5204
@code{memmove}, @code{memset}, @code{strcpy}, @code{stpcpy}, @code{strncpy},
5205
@code{strcat} and @code{strncat}.
5206
 
5207
There are also checking built-in functions for formatted output functions.
5208
@smallexample
5209
int __builtin___sprintf_chk (char *s, int flag, size_t os, const char *fmt, ...);
5210
int __builtin___snprintf_chk (char *s, size_t maxlen, int flag, size_t os,
5211
                              const char *fmt, ...);
5212
int __builtin___vsprintf_chk (char *s, int flag, size_t os, const char *fmt,
5213
                              va_list ap);
5214
int __builtin___vsnprintf_chk (char *s, size_t maxlen, int flag, size_t os,
5215
                               const char *fmt, va_list ap);
5216
@end smallexample
5217
 
5218
The added @var{flag} argument is passed unchanged to @code{__sprintf_chk}
5219
etc. functions and can contain implementation specific flags on what
5220
additional security measures the checking function might take, such as
5221
handling @code{%n} differently.
5222
 
5223
The @var{os} argument is the object size @var{s} points to, like in the
5224
other built-in functions.  There is a small difference in the behavior
5225
though, if @var{os} is @code{(size_t) -1}, the built-in functions are
5226
optimized into the non-checking functions only if @var{flag} is 0, otherwise
5227
the checking function is called with @var{os} argument set to
5228
@code{(size_t) -1}.
5229
 
5230
In addition to this, there are checking built-in functions
5231
@code{__builtin___printf_chk}, @code{__builtin___vprintf_chk},
5232
@code{__builtin___fprintf_chk} and @code{__builtin___vfprintf_chk}.
5233
These have just one additional argument, @var{flag}, right before
5234
format string @var{fmt}.  If the compiler is able to optimize them to
5235
@code{fputc} etc. functions, it will, otherwise the checking function
5236
should be called and the @var{flag} argument passed to it.
5237
 
5238
@node Other Builtins
5239
@section Other built-in functions provided by GCC
5240
@cindex built-in functions
5241
@findex __builtin_isgreater
5242
@findex __builtin_isgreaterequal
5243
@findex __builtin_isless
5244
@findex __builtin_islessequal
5245
@findex __builtin_islessgreater
5246
@findex __builtin_isunordered
5247
@findex __builtin_powi
5248
@findex __builtin_powif
5249
@findex __builtin_powil
5250
@findex _Exit
5251
@findex _exit
5252
@findex abort
5253
@findex abs
5254
@findex acos
5255
@findex acosf
5256
@findex acosh
5257
@findex acoshf
5258
@findex acoshl
5259
@findex acosl
5260
@findex alloca
5261
@findex asin
5262
@findex asinf
5263
@findex asinh
5264
@findex asinhf
5265
@findex asinhl
5266
@findex asinl
5267
@findex atan
5268
@findex atan2
5269
@findex atan2f
5270
@findex atan2l
5271
@findex atanf
5272
@findex atanh
5273
@findex atanhf
5274
@findex atanhl
5275
@findex atanl
5276
@findex bcmp
5277
@findex bzero
5278
@findex cabs
5279
@findex cabsf
5280
@findex cabsl
5281
@findex cacos
5282
@findex cacosf
5283
@findex cacosh
5284
@findex cacoshf
5285
@findex cacoshl
5286
@findex cacosl
5287
@findex calloc
5288
@findex carg
5289
@findex cargf
5290
@findex cargl
5291
@findex casin
5292
@findex casinf
5293
@findex casinh
5294
@findex casinhf
5295
@findex casinhl
5296
@findex casinl
5297
@findex catan
5298
@findex catanf
5299
@findex catanh
5300
@findex catanhf
5301
@findex catanhl
5302
@findex catanl
5303
@findex cbrt
5304
@findex cbrtf
5305
@findex cbrtl
5306
@findex ccos
5307
@findex ccosf
5308
@findex ccosh
5309
@findex ccoshf
5310
@findex ccoshl
5311
@findex ccosl
5312
@findex ceil
5313
@findex ceilf
5314
@findex ceill
5315
@findex cexp
5316
@findex cexpf
5317
@findex cexpl
5318
@findex cimag
5319
@findex cimagf
5320
@findex cimagl
5321
@findex clog
5322
@findex clogf
5323
@findex clogl
5324
@findex conj
5325
@findex conjf
5326
@findex conjl
5327
@findex copysign
5328
@findex copysignf
5329
@findex copysignl
5330
@findex cos
5331
@findex cosf
5332
@findex cosh
5333
@findex coshf
5334
@findex coshl
5335
@findex cosl
5336
@findex cpow
5337
@findex cpowf
5338
@findex cpowl
5339
@findex cproj
5340
@findex cprojf
5341
@findex cprojl
5342
@findex creal
5343
@findex crealf
5344
@findex creall
5345
@findex csin
5346
@findex csinf
5347
@findex csinh
5348
@findex csinhf
5349
@findex csinhl
5350
@findex csinl
5351
@findex csqrt
5352
@findex csqrtf
5353
@findex csqrtl
5354
@findex ctan
5355
@findex ctanf
5356
@findex ctanh
5357
@findex ctanhf
5358
@findex ctanhl
5359
@findex ctanl
5360
@findex dcgettext
5361
@findex dgettext
5362
@findex drem
5363
@findex dremf
5364
@findex dreml
5365
@findex erf
5366
@findex erfc
5367
@findex erfcf
5368
@findex erfcl
5369
@findex erff
5370
@findex erfl
5371
@findex exit
5372
@findex exp
5373
@findex exp10
5374
@findex exp10f
5375
@findex exp10l
5376
@findex exp2
5377
@findex exp2f
5378
@findex exp2l
5379
@findex expf
5380
@findex expl
5381
@findex expm1
5382
@findex expm1f
5383
@findex expm1l
5384
@findex fabs
5385
@findex fabsf
5386
@findex fabsl
5387
@findex fdim
5388
@findex fdimf
5389
@findex fdiml
5390
@findex ffs
5391
@findex floor
5392
@findex floorf
5393
@findex floorl
5394
@findex fma
5395
@findex fmaf
5396
@findex fmal
5397
@findex fmax
5398
@findex fmaxf
5399
@findex fmaxl
5400
@findex fmin
5401
@findex fminf
5402
@findex fminl
5403
@findex fmod
5404
@findex fmodf
5405
@findex fmodl
5406
@findex fprintf
5407
@findex fprintf_unlocked
5408
@findex fputs
5409
@findex fputs_unlocked
5410
@findex frexp
5411
@findex frexpf
5412
@findex frexpl
5413
@findex fscanf
5414
@findex gamma
5415
@findex gammaf
5416
@findex gammal
5417
@findex gettext
5418
@findex hypot
5419
@findex hypotf
5420
@findex hypotl
5421
@findex ilogb
5422
@findex ilogbf
5423
@findex ilogbl
5424
@findex imaxabs
5425
@findex index
5426
@findex isalnum
5427
@findex isalpha
5428
@findex isascii
5429
@findex isblank
5430
@findex iscntrl
5431
@findex isdigit
5432
@findex isgraph
5433
@findex islower
5434
@findex isprint
5435
@findex ispunct
5436
@findex isspace
5437
@findex isupper
5438
@findex iswalnum
5439
@findex iswalpha
5440
@findex iswblank
5441
@findex iswcntrl
5442
@findex iswdigit
5443
@findex iswgraph
5444
@findex iswlower
5445
@findex iswprint
5446
@findex iswpunct
5447
@findex iswspace
5448
@findex iswupper
5449
@findex iswxdigit
5450
@findex isxdigit
5451
@findex j0
5452
@findex j0f
5453
@findex j0l
5454
@findex j1
5455
@findex j1f
5456
@findex j1l
5457
@findex jn
5458
@findex jnf
5459
@findex jnl
5460
@findex labs
5461
@findex ldexp
5462
@findex ldexpf
5463
@findex ldexpl
5464
@findex lgamma
5465
@findex lgammaf
5466
@findex lgammal
5467
@findex llabs
5468
@findex llrint
5469
@findex llrintf
5470
@findex llrintl
5471
@findex llround
5472
@findex llroundf
5473
@findex llroundl
5474
@findex log
5475
@findex log10
5476
@findex log10f
5477
@findex log10l
5478
@findex log1p
5479
@findex log1pf
5480
@findex log1pl
5481
@findex log2
5482
@findex log2f
5483
@findex log2l
5484
@findex logb
5485
@findex logbf
5486
@findex logbl
5487
@findex logf
5488
@findex logl
5489
@findex lrint
5490
@findex lrintf
5491
@findex lrintl
5492
@findex lround
5493
@findex lroundf
5494
@findex lroundl
5495
@findex malloc
5496
@findex memcmp
5497
@findex memcpy
5498
@findex mempcpy
5499
@findex memset
5500
@findex modf
5501
@findex modff
5502
@findex modfl
5503
@findex nearbyint
5504
@findex nearbyintf
5505
@findex nearbyintl
5506
@findex nextafter
5507
@findex nextafterf
5508
@findex nextafterl
5509
@findex nexttoward
5510
@findex nexttowardf
5511
@findex nexttowardl
5512
@findex pow
5513
@findex pow10
5514
@findex pow10f
5515
@findex pow10l
5516
@findex powf
5517
@findex powl
5518
@findex printf
5519
@findex printf_unlocked
5520
@findex putchar
5521
@findex puts
5522
@findex remainder
5523
@findex remainderf
5524
@findex remainderl
5525
@findex remquo
5526
@findex remquof
5527
@findex remquol
5528
@findex rindex
5529
@findex rint
5530
@findex rintf
5531
@findex rintl
5532
@findex round
5533
@findex roundf
5534
@findex roundl
5535
@findex scalb
5536
@findex scalbf
5537
@findex scalbl
5538
@findex scalbln
5539
@findex scalblnf
5540
@findex scalblnf
5541
@findex scalbn
5542
@findex scalbnf
5543
@findex scanfnl
5544
@findex signbit
5545
@findex signbitf
5546
@findex signbitl
5547
@findex significand
5548
@findex significandf
5549
@findex significandl
5550
@findex sin
5551
@findex sincos
5552
@findex sincosf
5553
@findex sincosl
5554
@findex sinf
5555
@findex sinh
5556
@findex sinhf
5557
@findex sinhl
5558
@findex sinl
5559
@findex snprintf
5560
@findex sprintf
5561
@findex sqrt
5562
@findex sqrtf
5563
@findex sqrtl
5564
@findex sscanf
5565
@findex stpcpy
5566
@findex stpncpy
5567
@findex strcasecmp
5568
@findex strcat
5569
@findex strchr
5570
@findex strcmp
5571
@findex strcpy
5572
@findex strcspn
5573
@findex strdup
5574
@findex strfmon
5575
@findex strftime
5576
@findex strlen
5577
@findex strncasecmp
5578
@findex strncat
5579
@findex strncmp
5580
@findex strncpy
5581
@findex strndup
5582
@findex strpbrk
5583
@findex strrchr
5584
@findex strspn
5585
@findex strstr
5586
@findex tan
5587
@findex tanf
5588
@findex tanh
5589
@findex tanhf
5590
@findex tanhl
5591
@findex tanl
5592
@findex tgamma
5593
@findex tgammaf
5594
@findex tgammal
5595
@findex toascii
5596
@findex tolower
5597
@findex toupper
5598
@findex towlower
5599
@findex towupper
5600
@findex trunc
5601
@findex truncf
5602
@findex truncl
5603
@findex vfprintf
5604
@findex vfscanf
5605
@findex vprintf
5606
@findex vscanf
5607
@findex vsnprintf
5608
@findex vsprintf
5609
@findex vsscanf
5610
@findex y0
5611
@findex y0f
5612
@findex y0l
5613
@findex y1
5614
@findex y1f
5615
@findex y1l
5616
@findex yn
5617
@findex ynf
5618
@findex ynl
5619
 
5620
GCC provides a large number of built-in functions other than the ones
5621
mentioned above.  Some of these are for internal use in the processing
5622
of exceptions or variable-length argument lists and will not be
5623
documented here because they may change from time to time; we do not
5624
recommend general use of these functions.
5625
 
5626
The remaining functions are provided for optimization purposes.
5627
 
5628
@opindex fno-builtin
5629
GCC includes built-in versions of many of the functions in the standard
5630
C library.  The versions prefixed with @code{__builtin_} will always be
5631
treated as having the same meaning as the C library function even if you
5632
specify the @option{-fno-builtin} option.  (@pxref{C Dialect Options})
5633
Many of these functions are only optimized in certain cases; if they are
5634
not optimized in a particular case, a call to the library function will
5635
be emitted.
5636
 
5637
@opindex ansi
5638
@opindex std
5639
Outside strict ISO C mode (@option{-ansi}, @option{-std=c89} or
5640
@option{-std=c99}), the functions
5641
@code{_exit}, @code{alloca}, @code{bcmp}, @code{bzero},
5642
@code{dcgettext}, @code{dgettext}, @code{dremf}, @code{dreml},
5643
@code{drem}, @code{exp10f}, @code{exp10l}, @code{exp10}, @code{ffsll},
5644
@code{ffsl}, @code{ffs}, @code{fprintf_unlocked}, @code{fputs_unlocked},
5645
@code{gammaf}, @code{gammal}, @code{gamma}, @code{gettext},
5646
@code{index}, @code{isascii}, @code{j0f}, @code{j0l}, @code{j0},
5647
@code{j1f}, @code{j1l}, @code{j1}, @code{jnf}, @code{jnl}, @code{jn},
5648
@code{mempcpy}, @code{pow10f}, @code{pow10l}, @code{pow10},
5649
@code{printf_unlocked}, @code{rindex}, @code{scalbf}, @code{scalbl},
5650
@code{scalb}, @code{signbit}, @code{signbitf}, @code{signbitl},
5651
@code{significandf}, @code{significandl}, @code{significand},
5652
@code{sincosf}, @code{sincosl}, @code{sincos}, @code{stpcpy},
5653
@code{stpncpy}, @code{strcasecmp}, @code{strdup}, @code{strfmon},
5654
@code{strncasecmp}, @code{strndup}, @code{toascii}, @code{y0f},
5655
@code{y0l}, @code{y0}, @code{y1f}, @code{y1l}, @code{y1}, @code{ynf},
5656
@code{ynl} and @code{yn}
5657
may be handled as built-in functions.
5658
All these functions have corresponding versions
5659
prefixed with @code{__builtin_}, which may be used even in strict C89
5660
mode.
5661
 
5662
The ISO C99 functions
5663
@code{_Exit}, @code{acoshf}, @code{acoshl}, @code{acosh}, @code{asinhf},
5664
@code{asinhl}, @code{asinh}, @code{atanhf}, @code{atanhl}, @code{atanh},
5665
@code{cabsf}, @code{cabsl}, @code{cabs}, @code{cacosf}, @code{cacoshf},
5666
@code{cacoshl}, @code{cacosh}, @code{cacosl}, @code{cacos},
5667
@code{cargf}, @code{cargl}, @code{carg}, @code{casinf}, @code{casinhf},
5668
@code{casinhl}, @code{casinh}, @code{casinl}, @code{casin},
5669
@code{catanf}, @code{catanhf}, @code{catanhl}, @code{catanh},
5670
@code{catanl}, @code{catan}, @code{cbrtf}, @code{cbrtl}, @code{cbrt},
5671
@code{ccosf}, @code{ccoshf}, @code{ccoshl}, @code{ccosh}, @code{ccosl},
5672
@code{ccos}, @code{cexpf}, @code{cexpl}, @code{cexp}, @code{cimagf},
5673
@code{cimagl}, @code{cimag}, @code{clogf}, @code{clogl}, @code{clog},
5674
@code{conjf}, @code{conjl}, @code{conj}, @code{copysignf}, @code{copysignl},
5675
@code{copysign}, @code{cpowf}, @code{cpowl}, @code{cpow}, @code{cprojf},
5676
@code{cprojl}, @code{cproj}, @code{crealf}, @code{creall}, @code{creal},
5677
@code{csinf}, @code{csinhf}, @code{csinhl}, @code{csinh}, @code{csinl},
5678
@code{csin}, @code{csqrtf}, @code{csqrtl}, @code{csqrt}, @code{ctanf},
5679
@code{ctanhf}, @code{ctanhl}, @code{ctanh}, @code{ctanl}, @code{ctan},
5680
@code{erfcf}, @code{erfcl}, @code{erfc}, @code{erff}, @code{erfl},
5681
@code{erf}, @code{exp2f}, @code{exp2l}, @code{exp2}, @code{expm1f},
5682
@code{expm1l}, @code{expm1}, @code{fdimf}, @code{fdiml}, @code{fdim},
5683
@code{fmaf}, @code{fmal}, @code{fmaxf}, @code{fmaxl}, @code{fmax},
5684
@code{fma}, @code{fminf}, @code{fminl}, @code{fmin}, @code{hypotf},
5685
@code{hypotl}, @code{hypot}, @code{ilogbf}, @code{ilogbl}, @code{ilogb},
5686
@code{imaxabs}, @code{isblank}, @code{iswblank}, @code{lgammaf},
5687
@code{lgammal}, @code{lgamma}, @code{llabs}, @code{llrintf}, @code{llrintl},
5688
@code{llrint}, @code{llroundf}, @code{llroundl}, @code{llround},
5689
@code{log1pf}, @code{log1pl}, @code{log1p}, @code{log2f}, @code{log2l},
5690
@code{log2}, @code{logbf}, @code{logbl}, @code{logb}, @code{lrintf},
5691
@code{lrintl}, @code{lrint}, @code{lroundf}, @code{lroundl},
5692
@code{lround}, @code{nearbyintf}, @code{nearbyintl}, @code{nearbyint},
5693
@code{nextafterf}, @code{nextafterl}, @code{nextafter},
5694
@code{nexttowardf}, @code{nexttowardl}, @code{nexttoward},
5695
@code{remainderf}, @code{remainderl}, @code{remainder}, @code{remquof},
5696
@code{remquol}, @code{remquo}, @code{rintf}, @code{rintl}, @code{rint},
5697
@code{roundf}, @code{roundl}, @code{round}, @code{scalblnf},
5698
@code{scalblnl}, @code{scalbln}, @code{scalbnf}, @code{scalbnl},
5699
@code{scalbn}, @code{snprintf}, @code{tgammaf}, @code{tgammal},
5700
@code{tgamma}, @code{truncf}, @code{truncl}, @code{trunc},
5701
@code{vfscanf}, @code{vscanf}, @code{vsnprintf} and @code{vsscanf}
5702
are handled as built-in functions
5703
except in strict ISO C90 mode (@option{-ansi} or @option{-std=c89}).
5704
 
5705
There are also built-in versions of the ISO C99 functions
5706
@code{acosf}, @code{acosl}, @code{asinf}, @code{asinl}, @code{atan2f},
5707
@code{atan2l}, @code{atanf}, @code{atanl}, @code{ceilf}, @code{ceill},
5708
@code{cosf}, @code{coshf}, @code{coshl}, @code{cosl}, @code{expf},
5709
@code{expl}, @code{fabsf}, @code{fabsl}, @code{floorf}, @code{floorl},
5710
@code{fmodf}, @code{fmodl}, @code{frexpf}, @code{frexpl}, @code{ldexpf},
5711
@code{ldexpl}, @code{log10f}, @code{log10l}, @code{logf}, @code{logl},
5712
@code{modfl}, @code{modf}, @code{powf}, @code{powl}, @code{sinf},
5713
@code{sinhf}, @code{sinhl}, @code{sinl}, @code{sqrtf}, @code{sqrtl},
5714
@code{tanf}, @code{tanhf}, @code{tanhl} and @code{tanl}
5715
that are recognized in any mode since ISO C90 reserves these names for
5716
the purpose to which ISO C99 puts them.  All these functions have
5717
corresponding versions prefixed with @code{__builtin_}.
5718
 
5719
The ISO C94 functions
5720
@code{iswalnum}, @code{iswalpha}, @code{iswcntrl}, @code{iswdigit},
5721
@code{iswgraph}, @code{iswlower}, @code{iswprint}, @code{iswpunct},
5722
@code{iswspace}, @code{iswupper}, @code{iswxdigit}, @code{towlower} and
5723
@code{towupper}
5724
are handled as built-in functions
5725
except in strict ISO C90 mode (@option{-ansi} or @option{-std=c89}).
5726
 
5727
The ISO C90 functions
5728
@code{abort}, @code{abs}, @code{acos}, @code{asin}, @code{atan2},
5729
@code{atan}, @code{calloc}, @code{ceil}, @code{cosh}, @code{cos},
5730
@code{exit}, @code{exp}, @code{fabs}, @code{floor}, @code{fmod},
5731
@code{fprintf}, @code{fputs}, @code{frexp}, @code{fscanf},
5732
@code{isalnum}, @code{isalpha}, @code{iscntrl}, @code{isdigit},
5733
@code{isgraph}, @code{islower}, @code{isprint}, @code{ispunct},
5734
@code{isspace}, @code{isupper}, @code{isxdigit}, @code{tolower},
5735
@code{toupper}, @code{labs}, @code{ldexp}, @code{log10}, @code{log},
5736
@code{malloc}, @code{memcmp}, @code{memcpy}, @code{memset}, @code{modf},
5737
@code{pow}, @code{printf}, @code{putchar}, @code{puts}, @code{scanf},
5738
@code{sinh}, @code{sin}, @code{snprintf}, @code{sprintf}, @code{sqrt},
5739
@code{sscanf}, @code{strcat}, @code{strchr}, @code{strcmp},
5740
@code{strcpy}, @code{strcspn}, @code{strlen}, @code{strncat},
5741
@code{strncmp}, @code{strncpy}, @code{strpbrk}, @code{strrchr},
5742
@code{strspn}, @code{strstr}, @code{tanh}, @code{tan}, @code{vfprintf},
5743
@code{vprintf} and @code{vsprintf}
5744
are all recognized as built-in functions unless
5745
@option{-fno-builtin} is specified (or @option{-fno-builtin-@var{function}}
5746
is specified for an individual function).  All of these functions have
5747
corresponding versions prefixed with @code{__builtin_}.
5748
 
5749
GCC provides built-in versions of the ISO C99 floating point comparison
5750
macros that avoid raising exceptions for unordered operands.  They have
5751
the same names as the standard macros ( @code{isgreater},
5752
@code{isgreaterequal}, @code{isless}, @code{islessequal},
5753
@code{islessgreater}, and @code{isunordered}) , with @code{__builtin_}
5754
prefixed.  We intend for a library implementor to be able to simply
5755
@code{#define} each standard macro to its built-in equivalent.
5756
 
5757
@deftypefn {Built-in Function} int __builtin_types_compatible_p (@var{type1}, @var{type2})
5758
 
5759
You can use the built-in function @code{__builtin_types_compatible_p} to
5760
determine whether two types are the same.
5761
 
5762
This built-in function returns 1 if the unqualified versions of the
5763
types @var{type1} and @var{type2} (which are types, not expressions) are
5764
compatible, 0 otherwise.  The result of this built-in function can be
5765
used in integer constant expressions.
5766
 
5767
This built-in function ignores top level qualifiers (e.g., @code{const},
5768
@code{volatile}).  For example, @code{int} is equivalent to @code{const
5769
int}.
5770
 
5771
The type @code{int[]} and @code{int[5]} are compatible.  On the other
5772
hand, @code{int} and @code{char *} are not compatible, even if the size
5773
of their types, on the particular architecture are the same.  Also, the
5774
amount of pointer indirection is taken into account when determining
5775
similarity.  Consequently, @code{short *} is not similar to
5776
@code{short **}.  Furthermore, two types that are typedefed are
5777
considered compatible if their underlying types are compatible.
5778
 
5779
An @code{enum} type is not considered to be compatible with another
5780
@code{enum} type even if both are compatible with the same integer
5781
type; this is what the C standard specifies.
5782
For example, @code{enum @{foo, bar@}} is not similar to
5783
@code{enum @{hot, dog@}}.
5784
 
5785
You would typically use this function in code whose execution varies
5786
depending on the arguments' types.  For example:
5787
 
5788
@smallexample
5789
#define foo(x)                                                  \
5790
  (@{                                                           \
5791
    typeof (x) tmp = (x);                                       \
5792
    if (__builtin_types_compatible_p (typeof (x), long double)) \
5793
      tmp = foo_long_double (tmp);                              \
5794
    else if (__builtin_types_compatible_p (typeof (x), double)) \
5795
      tmp = foo_double (tmp);                                   \
5796
    else if (__builtin_types_compatible_p (typeof (x), float))  \
5797
      tmp = foo_float (tmp);                                    \
5798
    else                                                        \
5799
      abort ();                                                 \
5800
    tmp;                                                        \
5801
  @})
5802
@end smallexample
5803
 
5804
@emph{Note:} This construct is only available for C@.
5805
 
5806
@end deftypefn
5807
 
5808
@deftypefn {Built-in Function} @var{type} __builtin_choose_expr (@var{const_exp}, @var{exp1}, @var{exp2})
5809
 
5810
You can use the built-in function @code{__builtin_choose_expr} to
5811
evaluate code depending on the value of a constant expression.  This
5812
built-in function returns @var{exp1} if @var{const_exp}, which is a
5813
constant expression that must be able to be determined at compile time,
5814
is nonzero.  Otherwise it returns 0.
5815
 
5816
This built-in function is analogous to the @samp{? :} operator in C,
5817
except that the expression returned has its type unaltered by promotion
5818
rules.  Also, the built-in function does not evaluate the expression
5819
that was not chosen.  For example, if @var{const_exp} evaluates to true,
5820
@var{exp2} is not evaluated even if it has side-effects.
5821
 
5822
This built-in function can return an lvalue if the chosen argument is an
5823
lvalue.
5824
 
5825
If @var{exp1} is returned, the return type is the same as @var{exp1}'s
5826
type.  Similarly, if @var{exp2} is returned, its return type is the same
5827
as @var{exp2}.
5828
 
5829
Example:
5830
 
5831
@smallexample
5832
#define foo(x)                                                    \
5833
  __builtin_choose_expr (                                         \
5834
    __builtin_types_compatible_p (typeof (x), double),            \
5835
    foo_double (x),                                               \
5836
    __builtin_choose_expr (                                       \
5837
      __builtin_types_compatible_p (typeof (x), float),           \
5838
      foo_float (x),                                              \
5839
      /* @r{The void expression results in a compile-time error}  \
5840
         @r{when assigning the result to something.}  */          \
5841
      (void)0))
5842
@end smallexample
5843
 
5844
@emph{Note:} This construct is only available for C@.  Furthermore, the
5845
unused expression (@var{exp1} or @var{exp2} depending on the value of
5846
@var{const_exp}) may still generate syntax errors.  This may change in
5847
future revisions.
5848
 
5849
@end deftypefn
5850
 
5851
@deftypefn {Built-in Function} int __builtin_constant_p (@var{exp})
5852
You can use the built-in function @code{__builtin_constant_p} to
5853
determine if a value is known to be constant at compile-time and hence
5854
that GCC can perform constant-folding on expressions involving that
5855
value.  The argument of the function is the value to test.  The function
5856
returns the integer 1 if the argument is known to be a compile-time
5857
constant and 0 if it is not known to be a compile-time constant.  A
5858
return of 0 does not indicate that the value is @emph{not} a constant,
5859
but merely that GCC cannot prove it is a constant with the specified
5860
value of the @option{-O} option.
5861
 
5862
You would typically use this function in an embedded application where
5863
memory was a critical resource.  If you have some complex calculation,
5864
you may want it to be folded if it involves constants, but need to call
5865
a function if it does not.  For example:
5866
 
5867
@smallexample
5868
#define Scale_Value(X)      \
5869
  (__builtin_constant_p (X) \
5870
  ? ((X) * SCALE + OFFSET) : Scale (X))
5871
@end smallexample
5872
 
5873
You may use this built-in function in either a macro or an inline
5874
function.  However, if you use it in an inlined function and pass an
5875
argument of the function as the argument to the built-in, GCC will
5876
never return 1 when you call the inline function with a string constant
5877
or compound literal (@pxref{Compound Literals}) and will not return 1
5878
when you pass a constant numeric value to the inline function unless you
5879
specify the @option{-O} option.
5880
 
5881
You may also use @code{__builtin_constant_p} in initializers for static
5882
data.  For instance, you can write
5883
 
5884
@smallexample
5885
static const int table[] = @{
5886
   __builtin_constant_p (EXPRESSION) ? (EXPRESSION) : -1,
5887
   /* @r{@dots{}} */
5888
@};
5889
@end smallexample
5890
 
5891
@noindent
5892
This is an acceptable initializer even if @var{EXPRESSION} is not a
5893
constant expression.  GCC must be more conservative about evaluating the
5894
built-in in this case, because it has no opportunity to perform
5895
optimization.
5896
 
5897
Previous versions of GCC did not accept this built-in in data
5898
initializers.  The earliest version where it is completely safe is
5899
3.0.1.
5900
@end deftypefn
5901
 
5902
@deftypefn {Built-in Function} long __builtin_expect (long @var{exp}, long @var{c})
5903
@opindex fprofile-arcs
5904
You may use @code{__builtin_expect} to provide the compiler with
5905
branch prediction information.  In general, you should prefer to
5906
use actual profile feedback for this (@option{-fprofile-arcs}), as
5907
programmers are notoriously bad at predicting how their programs
5908
actually perform.  However, there are applications in which this
5909
data is hard to collect.
5910
 
5911
The return value is the value of @var{exp}, which should be an
5912
integral expression.  The value of @var{c} must be a compile-time
5913
constant.  The semantics of the built-in are that it is expected
5914
that @var{exp} == @var{c}.  For example:
5915
 
5916
@smallexample
5917
if (__builtin_expect (x, 0))
5918
  foo ();
5919
@end smallexample
5920
 
5921
@noindent
5922
would indicate that we do not expect to call @code{foo}, since
5923
we expect @code{x} to be zero.  Since you are limited to integral
5924
expressions for @var{exp}, you should use constructions such as
5925
 
5926
@smallexample
5927
if (__builtin_expect (ptr != NULL, 1))
5928
  error ();
5929
@end smallexample
5930
 
5931
@noindent
5932
when testing pointer or floating-point values.
5933
@end deftypefn
5934
 
5935
@deftypefn {Built-in Function} void __builtin_prefetch (const void *@var{addr}, ...)
5936
This function is used to minimize cache-miss latency by moving data into
5937
a cache before it is accessed.
5938
You can insert calls to @code{__builtin_prefetch} into code for which
5939
you know addresses of data in memory that is likely to be accessed soon.
5940
If the target supports them, data prefetch instructions will be generated.
5941
If the prefetch is done early enough before the access then the data will
5942
be in the cache by the time it is accessed.
5943
 
5944
The value of @var{addr} is the address of the memory to prefetch.
5945
There are two optional arguments, @var{rw} and @var{locality}.
5946
The value of @var{rw} is a compile-time constant one or zero; one
5947
means that the prefetch is preparing for a write to the memory address
5948
and zero, the default, means that the prefetch is preparing for a read.
5949
The value @var{locality} must be a compile-time constant integer between
5950
zero and three.  A value of zero means that the data has no temporal
5951
locality, so it need not be left in the cache after the access.  A value
5952
of three means that the data has a high degree of temporal locality and
5953
should be left in all levels of cache possible.  Values of one and two
5954
mean, respectively, a low or moderate degree of temporal locality.  The
5955
default is three.
5956
 
5957
@smallexample
5958
for (i = 0; i < n; i++)
5959
  @{
5960
    a[i] = a[i] + b[i];
5961
    __builtin_prefetch (&a[i+j], 1, 1);
5962
    __builtin_prefetch (&b[i+j], 0, 1);
5963
    /* @r{@dots{}} */
5964
  @}
5965
@end smallexample
5966
 
5967
Data prefetch does not generate faults if @var{addr} is invalid, but
5968
the address expression itself must be valid.  For example, a prefetch
5969
of @code{p->next} will not fault if @code{p->next} is not a valid
5970
address, but evaluation will fault if @code{p} is not a valid address.
5971
 
5972
If the target does not support data prefetch, the address expression
5973
is evaluated if it includes side effects but no other code is generated
5974
and GCC does not issue a warning.
5975
@end deftypefn
5976
 
5977
@deftypefn {Built-in Function} double __builtin_huge_val (void)
5978
Returns a positive infinity, if supported by the floating-point format,
5979
else @code{DBL_MAX}.  This function is suitable for implementing the
5980
ISO C macro @code{HUGE_VAL}.
5981
@end deftypefn
5982
 
5983
@deftypefn {Built-in Function} float __builtin_huge_valf (void)
5984
Similar to @code{__builtin_huge_val}, except the return type is @code{float}.
5985
@end deftypefn
5986
 
5987
@deftypefn {Built-in Function} {long double} __builtin_huge_vall (void)
5988
Similar to @code{__builtin_huge_val}, except the return
5989
type is @code{long double}.
5990
@end deftypefn
5991
 
5992
@deftypefn {Built-in Function} double __builtin_inf (void)
5993
Similar to @code{__builtin_huge_val}, except a warning is generated
5994
if the target floating-point format does not support infinities.
5995
@end deftypefn
5996
 
5997
@deftypefn {Built-in Function} _Decimal32 __builtin_infd32 (void)
5998
Similar to @code{__builtin_inf}, except the return type is @code{_Decimal32}.
5999
@end deftypefn
6000
 
6001
@deftypefn {Built-in Function} _Decimal64 __builtin_infd64 (void)
6002
Similar to @code{__builtin_inf}, except the return type is @code{_Decimal64}.
6003
@end deftypefn
6004
 
6005
@deftypefn {Built-in Function} _Decimal128 __builtin_infd128 (void)
6006
Similar to @code{__builtin_inf}, except the return type is @code{_Decimal128}.
6007
@end deftypefn
6008
 
6009
@deftypefn {Built-in Function} float __builtin_inff (void)
6010
Similar to @code{__builtin_inf}, except the return type is @code{float}.
6011
This function is suitable for implementing the ISO C99 macro @code{INFINITY}.
6012
@end deftypefn
6013
 
6014
@deftypefn {Built-in Function} {long double} __builtin_infl (void)
6015
Similar to @code{__builtin_inf}, except the return
6016
type is @code{long double}.
6017
@end deftypefn
6018
 
6019
@deftypefn {Built-in Function} double __builtin_nan (const char *str)
6020
This is an implementation of the ISO C99 function @code{nan}.
6021
 
6022
Since ISO C99 defines this function in terms of @code{strtod}, which we
6023
do not implement, a description of the parsing is in order.  The string
6024
is parsed as by @code{strtol}; that is, the base is recognized by
6025
leading @samp{0} or @samp{0x} prefixes.  The number parsed is placed
6026
in the significand such that the least significant bit of the number
6027
is at the least significant bit of the significand.  The number is
6028
truncated to fit the significand field provided.  The significand is
6029
forced to be a quiet NaN@.
6030
 
6031
This function, if given a string literal all of which would have been
6032
consumed by strtol, is evaluated early enough that it is considered a
6033
compile-time constant.
6034
@end deftypefn
6035
 
6036
@deftypefn {Built-in Function} _Decimal32 __builtin_nand32 (const char *str)
6037
Similar to @code{__builtin_nan}, except the return type is @code{_Decimal32}.
6038
@end deftypefn
6039
 
6040
@deftypefn {Built-in Function} _Decimal64 __builtin_nand64 (const char *str)
6041
Similar to @code{__builtin_nan}, except the return type is @code{_Decimal64}.
6042
@end deftypefn
6043
 
6044
@deftypefn {Built-in Function} _Decimal128 __builtin_nand128 (const char *str)
6045
Similar to @code{__builtin_nan}, except the return type is @code{_Decimal128}.
6046
@end deftypefn
6047
 
6048
@deftypefn {Built-in Function} float __builtin_nanf (const char *str)
6049
Similar to @code{__builtin_nan}, except the return type is @code{float}.
6050
@end deftypefn
6051
 
6052
@deftypefn {Built-in Function} {long double} __builtin_nanl (const char *str)
6053
Similar to @code{__builtin_nan}, except the return type is @code{long double}.
6054
@end deftypefn
6055
 
6056
@deftypefn {Built-in Function} double __builtin_nans (const char *str)
6057
Similar to @code{__builtin_nan}, except the significand is forced
6058
to be a signaling NaN@.  The @code{nans} function is proposed by
6059
@uref{http://www.open-std.org/jtc1/sc22/wg14/www/docs/n965.htm,,WG14 N965}.
6060
@end deftypefn
6061
 
6062
@deftypefn {Built-in Function} float __builtin_nansf (const char *str)
6063
Similar to @code{__builtin_nans}, except the return type is @code{float}.
6064
@end deftypefn
6065
 
6066
@deftypefn {Built-in Function} {long double} __builtin_nansl (const char *str)
6067
Similar to @code{__builtin_nans}, except the return type is @code{long double}.
6068
@end deftypefn
6069
 
6070
@deftypefn {Built-in Function} int __builtin_ffs (unsigned int x)
6071
Returns one plus the index of the least significant 1-bit of @var{x}, or
6072
if @var{x} is zero, returns zero.
6073
@end deftypefn
6074
 
6075
@deftypefn {Built-in Function} int __builtin_clz (unsigned int x)
6076
Returns the number of leading 0-bits in @var{x}, starting at the most
6077
significant bit position.  If @var{x} is 0, the result is undefined.
6078
@end deftypefn
6079
 
6080
@deftypefn {Built-in Function} int __builtin_ctz (unsigned int x)
6081
Returns the number of trailing 0-bits in @var{x}, starting at the least
6082
significant bit position.  If @var{x} is 0, the result is undefined.
6083
@end deftypefn
6084
 
6085
@deftypefn {Built-in Function} int __builtin_popcount (unsigned int x)
6086
Returns the number of 1-bits in @var{x}.
6087
@end deftypefn
6088
 
6089
@deftypefn {Built-in Function} int __builtin_parity (unsigned int x)
6090
Returns the parity of @var{x}, i.e.@: the number of 1-bits in @var{x}
6091
modulo 2.
6092
@end deftypefn
6093
 
6094
@deftypefn {Built-in Function} int __builtin_ffsl (unsigned long)
6095
Similar to @code{__builtin_ffs}, except the argument type is
6096
@code{unsigned long}.
6097
@end deftypefn
6098
 
6099
@deftypefn {Built-in Function} int __builtin_clzl (unsigned long)
6100
Similar to @code{__builtin_clz}, except the argument type is
6101
@code{unsigned long}.
6102
@end deftypefn
6103
 
6104
@deftypefn {Built-in Function} int __builtin_ctzl (unsigned long)
6105
Similar to @code{__builtin_ctz}, except the argument type is
6106
@code{unsigned long}.
6107
@end deftypefn
6108
 
6109
@deftypefn {Built-in Function} int __builtin_popcountl (unsigned long)
6110
Similar to @code{__builtin_popcount}, except the argument type is
6111
@code{unsigned long}.
6112
@end deftypefn
6113
 
6114
@deftypefn {Built-in Function} int __builtin_parityl (unsigned long)
6115
Similar to @code{__builtin_parity}, except the argument type is
6116
@code{unsigned long}.
6117
@end deftypefn
6118
 
6119
@deftypefn {Built-in Function} int __builtin_ffsll (unsigned long long)
6120
Similar to @code{__builtin_ffs}, except the argument type is
6121
@code{unsigned long long}.
6122
@end deftypefn
6123
 
6124
@deftypefn {Built-in Function} int __builtin_clzll (unsigned long long)
6125
Similar to @code{__builtin_clz}, except the argument type is
6126
@code{unsigned long long}.
6127
@end deftypefn
6128
 
6129
@deftypefn {Built-in Function} int __builtin_ctzll (unsigned long long)
6130
Similar to @code{__builtin_ctz}, except the argument type is
6131
@code{unsigned long long}.
6132
@end deftypefn
6133
 
6134
@deftypefn {Built-in Function} int __builtin_popcountll (unsigned long long)
6135
Similar to @code{__builtin_popcount}, except the argument type is
6136
@code{unsigned long long}.
6137
@end deftypefn
6138
 
6139
@deftypefn {Built-in Function} int __builtin_parityll (unsigned long long)
6140
Similar to @code{__builtin_parity}, except the argument type is
6141
@code{unsigned long long}.
6142
@end deftypefn
6143
 
6144
@deftypefn {Built-in Function} double __builtin_powi (double, int)
6145
Returns the first argument raised to the power of the second.  Unlike the
6146
@code{pow} function no guarantees about precision and rounding are made.
6147
@end deftypefn
6148
 
6149
@deftypefn {Built-in Function} float __builtin_powif (float, int)
6150
Similar to @code{__builtin_powi}, except the argument and return types
6151
are @code{float}.
6152
@end deftypefn
6153
 
6154
@deftypefn {Built-in Function} {long double} __builtin_powil (long double, int)
6155
Similar to @code{__builtin_powi}, except the argument and return types
6156
are @code{long double}.
6157
@end deftypefn
6158
 
6159
 
6160
@node Target Builtins
6161
@section Built-in Functions Specific to Particular Target Machines
6162
 
6163
On some target machines, GCC supports many built-in functions specific
6164
to those machines.  Generally these generate calls to specific machine
6165
instructions, but allow the compiler to schedule those calls.
6166
 
6167
@menu
6168
* Alpha Built-in Functions::
6169
* ARM Built-in Functions::
6170
* Blackfin Built-in Functions::
6171
* FR-V Built-in Functions::
6172
* X86 Built-in Functions::
6173
* MIPS DSP Built-in Functions::
6174
* MIPS Paired-Single Support::
6175
* PowerPC AltiVec Built-in Functions::
6176
* SPARC VIS Built-in Functions::
6177
@end menu
6178
 
6179
@node Alpha Built-in Functions
6180
@subsection Alpha Built-in Functions
6181
 
6182
These built-in functions are available for the Alpha family of
6183
processors, depending on the command-line switches used.
6184
 
6185
The following built-in functions are always available.  They
6186
all generate the machine instruction that is part of the name.
6187
 
6188
@smallexample
6189
long __builtin_alpha_implver (void)
6190
long __builtin_alpha_rpcc (void)
6191
long __builtin_alpha_amask (long)
6192
long __builtin_alpha_cmpbge (long, long)
6193
long __builtin_alpha_extbl (long, long)
6194
long __builtin_alpha_extwl (long, long)
6195
long __builtin_alpha_extll (long, long)
6196
long __builtin_alpha_extql (long, long)
6197
long __builtin_alpha_extwh (long, long)
6198
long __builtin_alpha_extlh (long, long)
6199
long __builtin_alpha_extqh (long, long)
6200
long __builtin_alpha_insbl (long, long)
6201
long __builtin_alpha_inswl (long, long)
6202
long __builtin_alpha_insll (long, long)
6203
long __builtin_alpha_insql (long, long)
6204
long __builtin_alpha_inswh (long, long)
6205
long __builtin_alpha_inslh (long, long)
6206
long __builtin_alpha_insqh (long, long)
6207
long __builtin_alpha_mskbl (long, long)
6208
long __builtin_alpha_mskwl (long, long)
6209
long __builtin_alpha_mskll (long, long)
6210
long __builtin_alpha_mskql (long, long)
6211
long __builtin_alpha_mskwh (long, long)
6212
long __builtin_alpha_msklh (long, long)
6213
long __builtin_alpha_mskqh (long, long)
6214
long __builtin_alpha_umulh (long, long)
6215
long __builtin_alpha_zap (long, long)
6216
long __builtin_alpha_zapnot (long, long)
6217
@end smallexample
6218
 
6219
The following built-in functions are always with @option{-mmax}
6220
or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{pca56} or
6221
later.  They all generate the machine instruction that is part
6222
of the name.
6223
 
6224
@smallexample
6225
long __builtin_alpha_pklb (long)
6226
long __builtin_alpha_pkwb (long)
6227
long __builtin_alpha_unpkbl (long)
6228
long __builtin_alpha_unpkbw (long)
6229
long __builtin_alpha_minub8 (long, long)
6230
long __builtin_alpha_minsb8 (long, long)
6231
long __builtin_alpha_minuw4 (long, long)
6232
long __builtin_alpha_minsw4 (long, long)
6233
long __builtin_alpha_maxub8 (long, long)
6234
long __builtin_alpha_maxsb8 (long, long)
6235
long __builtin_alpha_maxuw4 (long, long)
6236
long __builtin_alpha_maxsw4 (long, long)
6237
long __builtin_alpha_perr (long, long)
6238
@end smallexample
6239
 
6240
The following built-in functions are always with @option{-mcix}
6241
or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{ev67} or
6242
later.  They all generate the machine instruction that is part
6243
of the name.
6244
 
6245
@smallexample
6246
long __builtin_alpha_cttz (long)
6247
long __builtin_alpha_ctlz (long)
6248
long __builtin_alpha_ctpop (long)
6249
@end smallexample
6250
 
6251
The following builtins are available on systems that use the OSF/1
6252
PALcode.  Normally they invoke the @code{rduniq} and @code{wruniq}
6253
PAL calls, but when invoked with @option{-mtls-kernel}, they invoke
6254
@code{rdval} and @code{wrval}.
6255
 
6256
@smallexample
6257
void *__builtin_thread_pointer (void)
6258
void __builtin_set_thread_pointer (void *)
6259
@end smallexample
6260
 
6261
@node ARM Built-in Functions
6262
@subsection ARM Built-in Functions
6263
 
6264
These built-in functions are available for the ARM family of
6265
processors, when the @option{-mcpu=iwmmxt} switch is used:
6266
 
6267
@smallexample
6268
typedef int v2si __attribute__ ((vector_size (8)));
6269
typedef short v4hi __attribute__ ((vector_size (8)));
6270
typedef char v8qi __attribute__ ((vector_size (8)));
6271
 
6272
int __builtin_arm_getwcx (int)
6273
void __builtin_arm_setwcx (int, int)
6274
int __builtin_arm_textrmsb (v8qi, int)
6275
int __builtin_arm_textrmsh (v4hi, int)
6276
int __builtin_arm_textrmsw (v2si, int)
6277
int __builtin_arm_textrmub (v8qi, int)
6278
int __builtin_arm_textrmuh (v4hi, int)
6279
int __builtin_arm_textrmuw (v2si, int)
6280
v8qi __builtin_arm_tinsrb (v8qi, int)
6281
v4hi __builtin_arm_tinsrh (v4hi, int)
6282
v2si __builtin_arm_tinsrw (v2si, int)
6283
long long __builtin_arm_tmia (long long, int, int)
6284
long long __builtin_arm_tmiabb (long long, int, int)
6285
long long __builtin_arm_tmiabt (long long, int, int)
6286
long long __builtin_arm_tmiaph (long long, int, int)
6287
long long __builtin_arm_tmiatb (long long, int, int)
6288
long long __builtin_arm_tmiatt (long long, int, int)
6289
int __builtin_arm_tmovmskb (v8qi)
6290
int __builtin_arm_tmovmskh (v4hi)
6291
int __builtin_arm_tmovmskw (v2si)
6292
long long __builtin_arm_waccb (v8qi)
6293
long long __builtin_arm_wacch (v4hi)
6294
long long __builtin_arm_waccw (v2si)
6295
v8qi __builtin_arm_waddb (v8qi, v8qi)
6296
v8qi __builtin_arm_waddbss (v8qi, v8qi)
6297
v8qi __builtin_arm_waddbus (v8qi, v8qi)
6298
v4hi __builtin_arm_waddh (v4hi, v4hi)
6299
v4hi __builtin_arm_waddhss (v4hi, v4hi)
6300
v4hi __builtin_arm_waddhus (v4hi, v4hi)
6301
v2si __builtin_arm_waddw (v2si, v2si)
6302
v2si __builtin_arm_waddwss (v2si, v2si)
6303
v2si __builtin_arm_waddwus (v2si, v2si)
6304
v8qi __builtin_arm_walign (v8qi, v8qi, int)
6305
long long __builtin_arm_wand(long long, long long)
6306
long long __builtin_arm_wandn (long long, long long)
6307
v8qi __builtin_arm_wavg2b (v8qi, v8qi)
6308
v8qi __builtin_arm_wavg2br (v8qi, v8qi)
6309
v4hi __builtin_arm_wavg2h (v4hi, v4hi)
6310
v4hi __builtin_arm_wavg2hr (v4hi, v4hi)
6311
v8qi __builtin_arm_wcmpeqb (v8qi, v8qi)
6312
v4hi __builtin_arm_wcmpeqh (v4hi, v4hi)
6313
v2si __builtin_arm_wcmpeqw (v2si, v2si)
6314
v8qi __builtin_arm_wcmpgtsb (v8qi, v8qi)
6315
v4hi __builtin_arm_wcmpgtsh (v4hi, v4hi)
6316
v2si __builtin_arm_wcmpgtsw (v2si, v2si)
6317
v8qi __builtin_arm_wcmpgtub (v8qi, v8qi)
6318
v4hi __builtin_arm_wcmpgtuh (v4hi, v4hi)
6319
v2si __builtin_arm_wcmpgtuw (v2si, v2si)
6320
long long __builtin_arm_wmacs (long long, v4hi, v4hi)
6321
long long __builtin_arm_wmacsz (v4hi, v4hi)
6322
long long __builtin_arm_wmacu (long long, v4hi, v4hi)
6323
long long __builtin_arm_wmacuz (v4hi, v4hi)
6324
v4hi __builtin_arm_wmadds (v4hi, v4hi)
6325
v4hi __builtin_arm_wmaddu (v4hi, v4hi)
6326
v8qi __builtin_arm_wmaxsb (v8qi, v8qi)
6327
v4hi __builtin_arm_wmaxsh (v4hi, v4hi)
6328
v2si __builtin_arm_wmaxsw (v2si, v2si)
6329
v8qi __builtin_arm_wmaxub (v8qi, v8qi)
6330
v4hi __builtin_arm_wmaxuh (v4hi, v4hi)
6331
v2si __builtin_arm_wmaxuw (v2si, v2si)
6332
v8qi __builtin_arm_wminsb (v8qi, v8qi)
6333
v4hi __builtin_arm_wminsh (v4hi, v4hi)
6334
v2si __builtin_arm_wminsw (v2si, v2si)
6335
v8qi __builtin_arm_wminub (v8qi, v8qi)
6336
v4hi __builtin_arm_wminuh (v4hi, v4hi)
6337
v2si __builtin_arm_wminuw (v2si, v2si)
6338
v4hi __builtin_arm_wmulsm (v4hi, v4hi)
6339
v4hi __builtin_arm_wmulul (v4hi, v4hi)
6340
v4hi __builtin_arm_wmulum (v4hi, v4hi)
6341
long long __builtin_arm_wor (long long, long long)
6342
v2si __builtin_arm_wpackdss (long long, long long)
6343
v2si __builtin_arm_wpackdus (long long, long long)
6344
v8qi __builtin_arm_wpackhss (v4hi, v4hi)
6345
v8qi __builtin_arm_wpackhus (v4hi, v4hi)
6346
v4hi __builtin_arm_wpackwss (v2si, v2si)
6347
v4hi __builtin_arm_wpackwus (v2si, v2si)
6348
long long __builtin_arm_wrord (long long, long long)
6349
long long __builtin_arm_wrordi (long long, int)
6350
v4hi __builtin_arm_wrorh (v4hi, long long)
6351
v4hi __builtin_arm_wrorhi (v4hi, int)
6352
v2si __builtin_arm_wrorw (v2si, long long)
6353
v2si __builtin_arm_wrorwi (v2si, int)
6354
v2si __builtin_arm_wsadb (v8qi, v8qi)
6355
v2si __builtin_arm_wsadbz (v8qi, v8qi)
6356
v2si __builtin_arm_wsadh (v4hi, v4hi)
6357
v2si __builtin_arm_wsadhz (v4hi, v4hi)
6358
v4hi __builtin_arm_wshufh (v4hi, int)
6359
long long __builtin_arm_wslld (long long, long long)
6360
long long __builtin_arm_wslldi (long long, int)
6361
v4hi __builtin_arm_wsllh (v4hi, long long)
6362
v4hi __builtin_arm_wsllhi (v4hi, int)
6363
v2si __builtin_arm_wsllw (v2si, long long)
6364
v2si __builtin_arm_wsllwi (v2si, int)
6365
long long __builtin_arm_wsrad (long long, long long)
6366
long long __builtin_arm_wsradi (long long, int)
6367
v4hi __builtin_arm_wsrah (v4hi, long long)
6368
v4hi __builtin_arm_wsrahi (v4hi, int)
6369
v2si __builtin_arm_wsraw (v2si, long long)
6370
v2si __builtin_arm_wsrawi (v2si, int)
6371
long long __builtin_arm_wsrld (long long, long long)
6372
long long __builtin_arm_wsrldi (long long, int)
6373
v4hi __builtin_arm_wsrlh (v4hi, long long)
6374
v4hi __builtin_arm_wsrlhi (v4hi, int)
6375
v2si __builtin_arm_wsrlw (v2si, long long)
6376
v2si __builtin_arm_wsrlwi (v2si, int)
6377
v8qi __builtin_arm_wsubb (v8qi, v8qi)
6378
v8qi __builtin_arm_wsubbss (v8qi, v8qi)
6379
v8qi __builtin_arm_wsubbus (v8qi, v8qi)
6380
v4hi __builtin_arm_wsubh (v4hi, v4hi)
6381
v4hi __builtin_arm_wsubhss (v4hi, v4hi)
6382
v4hi __builtin_arm_wsubhus (v4hi, v4hi)
6383
v2si __builtin_arm_wsubw (v2si, v2si)
6384
v2si __builtin_arm_wsubwss (v2si, v2si)
6385
v2si __builtin_arm_wsubwus (v2si, v2si)
6386
v4hi __builtin_arm_wunpckehsb (v8qi)
6387
v2si __builtin_arm_wunpckehsh (v4hi)
6388
long long __builtin_arm_wunpckehsw (v2si)
6389
v4hi __builtin_arm_wunpckehub (v8qi)
6390
v2si __builtin_arm_wunpckehuh (v4hi)
6391
long long __builtin_arm_wunpckehuw (v2si)
6392
v4hi __builtin_arm_wunpckelsb (v8qi)
6393
v2si __builtin_arm_wunpckelsh (v4hi)
6394
long long __builtin_arm_wunpckelsw (v2si)
6395
v4hi __builtin_arm_wunpckelub (v8qi)
6396
v2si __builtin_arm_wunpckeluh (v4hi)
6397
long long __builtin_arm_wunpckeluw (v2si)
6398
v8qi __builtin_arm_wunpckihb (v8qi, v8qi)
6399
v4hi __builtin_arm_wunpckihh (v4hi, v4hi)
6400
v2si __builtin_arm_wunpckihw (v2si, v2si)
6401
v8qi __builtin_arm_wunpckilb (v8qi, v8qi)
6402
v4hi __builtin_arm_wunpckilh (v4hi, v4hi)
6403
v2si __builtin_arm_wunpckilw (v2si, v2si)
6404
long long __builtin_arm_wxor (long long, long long)
6405
long long __builtin_arm_wzero ()
6406
@end smallexample
6407
 
6408
@node Blackfin Built-in Functions
6409
@subsection Blackfin Built-in Functions
6410
 
6411
Currently, there are two Blackfin-specific built-in functions.  These are
6412
used for generating @code{CSYNC} and @code{SSYNC} machine insns without
6413
using inline assembly; by using these built-in functions the compiler can
6414
automatically add workarounds for hardware errata involving these
6415
instructions.  These functions are named as follows:
6416
 
6417
@smallexample
6418
void __builtin_bfin_csync (void)
6419
void __builtin_bfin_ssync (void)
6420
@end smallexample
6421
 
6422
@node FR-V Built-in Functions
6423
@subsection FR-V Built-in Functions
6424
 
6425
GCC provides many FR-V-specific built-in functions.  In general,
6426
these functions are intended to be compatible with those described
6427
by @cite{FR-V Family, Softune C/C++ Compiler Manual (V6), Fujitsu
6428
Semiconductor}.  The two exceptions are @code{__MDUNPACKH} and
6429
@code{__MBTOHE}, the gcc forms of which pass 128-bit values by
6430
pointer rather than by value.
6431
 
6432
Most of the functions are named after specific FR-V instructions.
6433
Such functions are said to be ``directly mapped'' and are summarized
6434
here in tabular form.
6435
 
6436
@menu
6437
* Argument Types::
6438
* Directly-mapped Integer Functions::
6439
* Directly-mapped Media Functions::
6440
* Raw read/write Functions::
6441
* Other Built-in Functions::
6442
@end menu
6443
 
6444
@node Argument Types
6445
@subsubsection Argument Types
6446
 
6447
The arguments to the built-in functions can be divided into three groups:
6448
register numbers, compile-time constants and run-time values.  In order
6449
to make this classification clear at a glance, the arguments and return
6450
values are given the following pseudo types:
6451
 
6452
@multitable @columnfractions .20 .30 .15 .35
6453
@item Pseudo type @tab Real C type @tab Constant? @tab Description
6454
@item @code{uh} @tab @code{unsigned short} @tab No @tab an unsigned halfword
6455
@item @code{uw1} @tab @code{unsigned int} @tab No @tab an unsigned word
6456
@item @code{sw1} @tab @code{int} @tab No @tab a signed word
6457
@item @code{uw2} @tab @code{unsigned long long} @tab No
6458
@tab an unsigned doubleword
6459
@item @code{sw2} @tab @code{long long} @tab No @tab a signed doubleword
6460
@item @code{const} @tab @code{int} @tab Yes @tab an integer constant
6461
@item @code{acc} @tab @code{int} @tab Yes @tab an ACC register number
6462
@item @code{iacc} @tab @code{int} @tab Yes @tab an IACC register number
6463
@end multitable
6464
 
6465
These pseudo types are not defined by GCC, they are simply a notational
6466
convenience used in this manual.
6467
 
6468
Arguments of type @code{uh}, @code{uw1}, @code{sw1}, @code{uw2}
6469
and @code{sw2} are evaluated at run time.  They correspond to
6470
register operands in the underlying FR-V instructions.
6471
 
6472
@code{const} arguments represent immediate operands in the underlying
6473
FR-V instructions.  They must be compile-time constants.
6474
 
6475
@code{acc} arguments are evaluated at compile time and specify the number
6476
of an accumulator register.  For example, an @code{acc} argument of 2
6477
will select the ACC2 register.
6478
 
6479
@code{iacc} arguments are similar to @code{acc} arguments but specify the
6480
number of an IACC register.  See @pxref{Other Built-in Functions}
6481
for more details.
6482
 
6483
@node Directly-mapped Integer Functions
6484
@subsubsection Directly-mapped Integer Functions
6485
 
6486
The functions listed below map directly to FR-V I-type instructions.
6487
 
6488
@multitable @columnfractions .45 .32 .23
6489
@item Function prototype @tab Example usage @tab Assembly output
6490
@item @code{sw1 __ADDSS (sw1, sw1)}
6491
@tab @code{@var{c} = __ADDSS (@var{a}, @var{b})}
6492
@tab @code{ADDSS @var{a},@var{b},@var{c}}
6493
@item @code{sw1 __SCAN (sw1, sw1)}
6494
@tab @code{@var{c} = __SCAN (@var{a}, @var{b})}
6495
@tab @code{SCAN @var{a},@var{b},@var{c}}
6496
@item @code{sw1 __SCUTSS (sw1)}
6497
@tab @code{@var{b} = __SCUTSS (@var{a})}
6498
@tab @code{SCUTSS @var{a},@var{b}}
6499
@item @code{sw1 __SLASS (sw1, sw1)}
6500
@tab @code{@var{c} = __SLASS (@var{a}, @var{b})}
6501
@tab @code{SLASS @var{a},@var{b},@var{c}}
6502
@item @code{void __SMASS (sw1, sw1)}
6503
@tab @code{__SMASS (@var{a}, @var{b})}
6504
@tab @code{SMASS @var{a},@var{b}}
6505
@item @code{void __SMSSS (sw1, sw1)}
6506
@tab @code{__SMSSS (@var{a}, @var{b})}
6507
@tab @code{SMSSS @var{a},@var{b}}
6508
@item @code{void __SMU (sw1, sw1)}
6509
@tab @code{__SMU (@var{a}, @var{b})}
6510
@tab @code{SMU @var{a},@var{b}}
6511
@item @code{sw2 __SMUL (sw1, sw1)}
6512
@tab @code{@var{c} = __SMUL (@var{a}, @var{b})}
6513
@tab @code{SMUL @var{a},@var{b},@var{c}}
6514
@item @code{sw1 __SUBSS (sw1, sw1)}
6515
@tab @code{@var{c} = __SUBSS (@var{a}, @var{b})}
6516
@tab @code{SUBSS @var{a},@var{b},@var{c}}
6517
@item @code{uw2 __UMUL (uw1, uw1)}
6518
@tab @code{@var{c} = __UMUL (@var{a}, @var{b})}
6519
@tab @code{UMUL @var{a},@var{b},@var{c}}
6520
@end multitable
6521
 
6522
@node Directly-mapped Media Functions
6523
@subsubsection Directly-mapped Media Functions
6524
 
6525
The functions listed below map directly to FR-V M-type instructions.
6526
 
6527
@multitable @columnfractions .45 .32 .23
6528
@item Function prototype @tab Example usage @tab Assembly output
6529
@item @code{uw1 __MABSHS (sw1)}
6530
@tab @code{@var{b} = __MABSHS (@var{a})}
6531
@tab @code{MABSHS @var{a},@var{b}}
6532
@item @code{void __MADDACCS (acc, acc)}
6533
@tab @code{__MADDACCS (@var{b}, @var{a})}
6534
@tab @code{MADDACCS @var{a},@var{b}}
6535
@item @code{sw1 __MADDHSS (sw1, sw1)}
6536
@tab @code{@var{c} = __MADDHSS (@var{a}, @var{b})}
6537
@tab @code{MADDHSS @var{a},@var{b},@var{c}}
6538
@item @code{uw1 __MADDHUS (uw1, uw1)}
6539
@tab @code{@var{c} = __MADDHUS (@var{a}, @var{b})}
6540
@tab @code{MADDHUS @var{a},@var{b},@var{c}}
6541
@item @code{uw1 __MAND (uw1, uw1)}
6542
@tab @code{@var{c} = __MAND (@var{a}, @var{b})}
6543
@tab @code{MAND @var{a},@var{b},@var{c}}
6544
@item @code{void __MASACCS (acc, acc)}
6545
@tab @code{__MASACCS (@var{b}, @var{a})}
6546
@tab @code{MASACCS @var{a},@var{b}}
6547
@item @code{uw1 __MAVEH (uw1, uw1)}
6548
@tab @code{@var{c} = __MAVEH (@var{a}, @var{b})}
6549
@tab @code{MAVEH @var{a},@var{b},@var{c}}
6550
@item @code{uw2 __MBTOH (uw1)}
6551
@tab @code{@var{b} = __MBTOH (@var{a})}
6552
@tab @code{MBTOH @var{a},@var{b}}
6553
@item @code{void __MBTOHE (uw1 *, uw1)}
6554
@tab @code{__MBTOHE (&@var{b}, @var{a})}
6555
@tab @code{MBTOHE @var{a},@var{b}}
6556
@item @code{void __MCLRACC (acc)}
6557
@tab @code{__MCLRACC (@var{a})}
6558
@tab @code{MCLRACC @var{a}}
6559
@item @code{void __MCLRACCA (void)}
6560
@tab @code{__MCLRACCA ()}
6561
@tab @code{MCLRACCA}
6562
@item @code{uw1 __Mcop1 (uw1, uw1)}
6563
@tab @code{@var{c} = __Mcop1 (@var{a}, @var{b})}
6564
@tab @code{Mcop1 @var{a},@var{b},@var{c}}
6565
@item @code{uw1 __Mcop2 (uw1, uw1)}
6566
@tab @code{@var{c} = __Mcop2 (@var{a}, @var{b})}
6567
@tab @code{Mcop2 @var{a},@var{b},@var{c}}
6568
@item @code{uw1 __MCPLHI (uw2, const)}
6569
@tab @code{@var{c} = __MCPLHI (@var{a}, @var{b})}
6570
@tab @code{MCPLHI @var{a},#@var{b},@var{c}}
6571
@item @code{uw1 __MCPLI (uw2, const)}
6572
@tab @code{@var{c} = __MCPLI (@var{a}, @var{b})}
6573
@tab @code{MCPLI @var{a},#@var{b},@var{c}}
6574
@item @code{void __MCPXIS (acc, sw1, sw1)}
6575
@tab @code{__MCPXIS (@var{c}, @var{a}, @var{b})}
6576
@tab @code{MCPXIS @var{a},@var{b},@var{c}}
6577
@item @code{void __MCPXIU (acc, uw1, uw1)}
6578
@tab @code{__MCPXIU (@var{c}, @var{a}, @var{b})}
6579
@tab @code{MCPXIU @var{a},@var{b},@var{c}}
6580
@item @code{void __MCPXRS (acc, sw1, sw1)}
6581
@tab @code{__MCPXRS (@var{c}, @var{a}, @var{b})}
6582
@tab @code{MCPXRS @var{a},@var{b},@var{c}}
6583
@item @code{void __MCPXRU (acc, uw1, uw1)}
6584
@tab @code{__MCPXRU (@var{c}, @var{a}, @var{b})}
6585
@tab @code{MCPXRU @var{a},@var{b},@var{c}}
6586
@item @code{uw1 __MCUT (acc, uw1)}
6587
@tab @code{@var{c} = __MCUT (@var{a}, @var{b})}
6588
@tab @code{MCUT @var{a},@var{b},@var{c}}
6589
@item @code{uw1 __MCUTSS (acc, sw1)}
6590
@tab @code{@var{c} = __MCUTSS (@var{a}, @var{b})}
6591
@tab @code{MCUTSS @var{a},@var{b},@var{c}}
6592
@item @code{void __MDADDACCS (acc, acc)}
6593
@tab @code{__MDADDACCS (@var{b}, @var{a})}
6594
@tab @code{MDADDACCS @var{a},@var{b}}
6595
@item @code{void __MDASACCS (acc, acc)}
6596
@tab @code{__MDASACCS (@var{b}, @var{a})}
6597
@tab @code{MDASACCS @var{a},@var{b}}
6598
@item @code{uw2 __MDCUTSSI (acc, const)}
6599
@tab @code{@var{c} = __MDCUTSSI (@var{a}, @var{b})}
6600
@tab @code{MDCUTSSI @var{a},#@var{b},@var{c}}
6601
@item @code{uw2 __MDPACKH (uw2, uw2)}
6602
@tab @code{@var{c} = __MDPACKH (@var{a}, @var{b})}
6603
@tab @code{MDPACKH @var{a},@var{b},@var{c}}
6604
@item @code{uw2 __MDROTLI (uw2, const)}
6605
@tab @code{@var{c} = __MDROTLI (@var{a}, @var{b})}
6606
@tab @code{MDROTLI @var{a},#@var{b},@var{c}}
6607
@item @code{void __MDSUBACCS (acc, acc)}
6608
@tab @code{__MDSUBACCS (@var{b}, @var{a})}
6609
@tab @code{MDSUBACCS @var{a},@var{b}}
6610
@item @code{void __MDUNPACKH (uw1 *, uw2)}
6611
@tab @code{__MDUNPACKH (&@var{b}, @var{a})}
6612
@tab @code{MDUNPACKH @var{a},@var{b}}
6613
@item @code{uw2 __MEXPDHD (uw1, const)}
6614
@tab @code{@var{c} = __MEXPDHD (@var{a}, @var{b})}
6615
@tab @code{MEXPDHD @var{a},#@var{b},@var{c}}
6616
@item @code{uw1 __MEXPDHW (uw1, const)}
6617
@tab @code{@var{c} = __MEXPDHW (@var{a}, @var{b})}
6618
@tab @code{MEXPDHW @var{a},#@var{b},@var{c}}
6619
@item @code{uw1 __MHDSETH (uw1, const)}
6620
@tab @code{@var{c} = __MHDSETH (@var{a}, @var{b})}
6621
@tab @code{MHDSETH @var{a},#@var{b},@var{c}}
6622
@item @code{sw1 __MHDSETS (const)}
6623
@tab @code{@var{b} = __MHDSETS (@var{a})}
6624
@tab @code{MHDSETS #@var{a},@var{b}}
6625
@item @code{uw1 __MHSETHIH (uw1, const)}
6626
@tab @code{@var{b} = __MHSETHIH (@var{b}, @var{a})}
6627
@tab @code{MHSETHIH #@var{a},@var{b}}
6628
@item @code{sw1 __MHSETHIS (sw1, const)}
6629
@tab @code{@var{b} = __MHSETHIS (@var{b}, @var{a})}
6630
@tab @code{MHSETHIS #@var{a},@var{b}}
6631
@item @code{uw1 __MHSETLOH (uw1, const)}
6632
@tab @code{@var{b} = __MHSETLOH (@var{b}, @var{a})}
6633
@tab @code{MHSETLOH #@var{a},@var{b}}
6634
@item @code{sw1 __MHSETLOS (sw1, const)}
6635
@tab @code{@var{b} = __MHSETLOS (@var{b}, @var{a})}
6636
@tab @code{MHSETLOS #@var{a},@var{b}}
6637
@item @code{uw1 __MHTOB (uw2)}
6638
@tab @code{@var{b} = __MHTOB (@var{a})}
6639
@tab @code{MHTOB @var{a},@var{b}}
6640
@item @code{void __MMACHS (acc, sw1, sw1)}
6641
@tab @code{__MMACHS (@var{c}, @var{a}, @var{b})}
6642
@tab @code{MMACHS @var{a},@var{b},@var{c}}
6643
@item @code{void __MMACHU (acc, uw1, uw1)}
6644
@tab @code{__MMACHU (@var{c}, @var{a}, @var{b})}
6645
@tab @code{MMACHU @var{a},@var{b},@var{c}}
6646
@item @code{void __MMRDHS (acc, sw1, sw1)}
6647
@tab @code{__MMRDHS (@var{c}, @var{a}, @var{b})}
6648
@tab @code{MMRDHS @var{a},@var{b},@var{c}}
6649
@item @code{void __MMRDHU (acc, uw1, uw1)}
6650
@tab @code{__MMRDHU (@var{c}, @var{a}, @var{b})}
6651
@tab @code{MMRDHU @var{a},@var{b},@var{c}}
6652
@item @code{void __MMULHS (acc, sw1, sw1)}
6653
@tab @code{__MMULHS (@var{c}, @var{a}, @var{b})}
6654
@tab @code{MMULHS @var{a},@var{b},@var{c}}
6655
@item @code{void __MMULHU (acc, uw1, uw1)}
6656
@tab @code{__MMULHU (@var{c}, @var{a}, @var{b})}
6657
@tab @code{MMULHU @var{a},@var{b},@var{c}}
6658
@item @code{void __MMULXHS (acc, sw1, sw1)}
6659
@tab @code{__MMULXHS (@var{c}, @var{a}, @var{b})}
6660
@tab @code{MMULXHS @var{a},@var{b},@var{c}}
6661
@item @code{void __MMULXHU (acc, uw1, uw1)}
6662
@tab @code{__MMULXHU (@var{c}, @var{a}, @var{b})}
6663
@tab @code{MMULXHU @var{a},@var{b},@var{c}}
6664
@item @code{uw1 __MNOT (uw1)}
6665
@tab @code{@var{b} = __MNOT (@var{a})}
6666
@tab @code{MNOT @var{a},@var{b}}
6667
@item @code{uw1 __MOR (uw1, uw1)}
6668
@tab @code{@var{c} = __MOR (@var{a}, @var{b})}
6669
@tab @code{MOR @var{a},@var{b},@var{c}}
6670
@item @code{uw1 __MPACKH (uh, uh)}
6671
@tab @code{@var{c} = __MPACKH (@var{a}, @var{b})}
6672
@tab @code{MPACKH @var{a},@var{b},@var{c}}
6673
@item @code{sw2 __MQADDHSS (sw2, sw2)}
6674
@tab @code{@var{c} = __MQADDHSS (@var{a}, @var{b})}
6675
@tab @code{MQADDHSS @var{a},@var{b},@var{c}}
6676
@item @code{uw2 __MQADDHUS (uw2, uw2)}
6677
@tab @code{@var{c} = __MQADDHUS (@var{a}, @var{b})}
6678
@tab @code{MQADDHUS @var{a},@var{b},@var{c}}
6679
@item @code{void __MQCPXIS (acc, sw2, sw2)}
6680
@tab @code{__MQCPXIS (@var{c}, @var{a}, @var{b})}
6681
@tab @code{MQCPXIS @var{a},@var{b},@var{c}}
6682
@item @code{void __MQCPXIU (acc, uw2, uw2)}
6683
@tab @code{__MQCPXIU (@var{c}, @var{a}, @var{b})}
6684
@tab @code{MQCPXIU @var{a},@var{b},@var{c}}
6685
@item @code{void __MQCPXRS (acc, sw2, sw2)}
6686
@tab @code{__MQCPXRS (@var{c}, @var{a}, @var{b})}
6687
@tab @code{MQCPXRS @var{a},@var{b},@var{c}}
6688
@item @code{void __MQCPXRU (acc, uw2, uw2)}
6689
@tab @code{__MQCPXRU (@var{c}, @var{a}, @var{b})}
6690
@tab @code{MQCPXRU @var{a},@var{b},@var{c}}
6691
@item @code{sw2 __MQLCLRHS (sw2, sw2)}
6692
@tab @code{@var{c} = __MQLCLRHS (@var{a}, @var{b})}
6693
@tab @code{MQLCLRHS @var{a},@var{b},@var{c}}
6694
@item @code{sw2 __MQLMTHS (sw2, sw2)}
6695
@tab @code{@var{c} = __MQLMTHS (@var{a}, @var{b})}
6696
@tab @code{MQLMTHS @var{a},@var{b},@var{c}}
6697
@item @code{void __MQMACHS (acc, sw2, sw2)}
6698
@tab @code{__MQMACHS (@var{c}, @var{a}, @var{b})}
6699
@tab @code{MQMACHS @var{a},@var{b},@var{c}}
6700
@item @code{void __MQMACHU (acc, uw2, uw2)}
6701
@tab @code{__MQMACHU (@var{c}, @var{a}, @var{b})}
6702
@tab @code{MQMACHU @var{a},@var{b},@var{c}}
6703
@item @code{void __MQMACXHS (acc, sw2, sw2)}
6704
@tab @code{__MQMACXHS (@var{c}, @var{a}, @var{b})}
6705
@tab @code{MQMACXHS @var{a},@var{b},@var{c}}
6706
@item @code{void __MQMULHS (acc, sw2, sw2)}
6707
@tab @code{__MQMULHS (@var{c}, @var{a}, @var{b})}
6708
@tab @code{MQMULHS @var{a},@var{b},@var{c}}
6709
@item @code{void __MQMULHU (acc, uw2, uw2)}
6710
@tab @code{__MQMULHU (@var{c}, @var{a}, @var{b})}
6711
@tab @code{MQMULHU @var{a},@var{b},@var{c}}
6712
@item @code{void __MQMULXHS (acc, sw2, sw2)}
6713
@tab @code{__MQMULXHS (@var{c}, @var{a}, @var{b})}
6714
@tab @code{MQMULXHS @var{a},@var{b},@var{c}}
6715
@item @code{void __MQMULXHU (acc, uw2, uw2)}
6716
@tab @code{__MQMULXHU (@var{c}, @var{a}, @var{b})}
6717
@tab @code{MQMULXHU @var{a},@var{b},@var{c}}
6718
@item @code{sw2 __MQSATHS (sw2, sw2)}
6719
@tab @code{@var{c} = __MQSATHS (@var{a}, @var{b})}
6720
@tab @code{MQSATHS @var{a},@var{b},@var{c}}
6721
@item @code{uw2 __MQSLLHI (uw2, int)}
6722
@tab @code{@var{c} = __MQSLLHI (@var{a}, @var{b})}
6723
@tab @code{MQSLLHI @var{a},@var{b},@var{c}}
6724
@item @code{sw2 __MQSRAHI (sw2, int)}
6725
@tab @code{@var{c} = __MQSRAHI (@var{a}, @var{b})}
6726
@tab @code{MQSRAHI @var{a},@var{b},@var{c}}
6727
@item @code{sw2 __MQSUBHSS (sw2, sw2)}
6728
@tab @code{@var{c} = __MQSUBHSS (@var{a}, @var{b})}
6729
@tab @code{MQSUBHSS @var{a},@var{b},@var{c}}
6730
@item @code{uw2 __MQSUBHUS (uw2, uw2)}
6731
@tab @code{@var{c} = __MQSUBHUS (@var{a}, @var{b})}
6732
@tab @code{MQSUBHUS @var{a},@var{b},@var{c}}
6733
@item @code{void __MQXMACHS (acc, sw2, sw2)}
6734
@tab @code{__MQXMACHS (@var{c}, @var{a}, @var{b})}
6735
@tab @code{MQXMACHS @var{a},@var{b},@var{c}}
6736
@item @code{void __MQXMACXHS (acc, sw2, sw2)}
6737
@tab @code{__MQXMACXHS (@var{c}, @var{a}, @var{b})}
6738
@tab @code{MQXMACXHS @var{a},@var{b},@var{c}}
6739
@item @code{uw1 __MRDACC (acc)}
6740
@tab @code{@var{b} = __MRDACC (@var{a})}
6741
@tab @code{MRDACC @var{a},@var{b}}
6742
@item @code{uw1 __MRDACCG (acc)}
6743
@tab @code{@var{b} = __MRDACCG (@var{a})}
6744
@tab @code{MRDACCG @var{a},@var{b}}
6745
@item @code{uw1 __MROTLI (uw1, const)}
6746
@tab @code{@var{c} = __MROTLI (@var{a}, @var{b})}
6747
@tab @code{MROTLI @var{a},#@var{b},@var{c}}
6748
@item @code{uw1 __MROTRI (uw1, const)}
6749
@tab @code{@var{c} = __MROTRI (@var{a}, @var{b})}
6750
@tab @code{MROTRI @var{a},#@var{b},@var{c}}
6751
@item @code{sw1 __MSATHS (sw1, sw1)}
6752
@tab @code{@var{c} = __MSATHS (@var{a}, @var{b})}
6753
@tab @code{MSATHS @var{a},@var{b},@var{c}}
6754
@item @code{uw1 __MSATHU (uw1, uw1)}
6755
@tab @code{@var{c} = __MSATHU (@var{a}, @var{b})}
6756
@tab @code{MSATHU @var{a},@var{b},@var{c}}
6757
@item @code{uw1 __MSLLHI (uw1, const)}
6758
@tab @code{@var{c} = __MSLLHI (@var{a}, @var{b})}
6759
@tab @code{MSLLHI @var{a},#@var{b},@var{c}}
6760
@item @code{sw1 __MSRAHI (sw1, const)}
6761
@tab @code{@var{c} = __MSRAHI (@var{a}, @var{b})}
6762
@tab @code{MSRAHI @var{a},#@var{b},@var{c}}
6763
@item @code{uw1 __MSRLHI (uw1, const)}
6764
@tab @code{@var{c} = __MSRLHI (@var{a}, @var{b})}
6765
@tab @code{MSRLHI @var{a},#@var{b},@var{c}}
6766
@item @code{void __MSUBACCS (acc, acc)}
6767
@tab @code{__MSUBACCS (@var{b}, @var{a})}
6768
@tab @code{MSUBACCS @var{a},@var{b}}
6769
@item @code{sw1 __MSUBHSS (sw1, sw1)}
6770
@tab @code{@var{c} = __MSUBHSS (@var{a}, @var{b})}
6771
@tab @code{MSUBHSS @var{a},@var{b},@var{c}}
6772
@item @code{uw1 __MSUBHUS (uw1, uw1)}
6773
@tab @code{@var{c} = __MSUBHUS (@var{a}, @var{b})}
6774
@tab @code{MSUBHUS @var{a},@var{b},@var{c}}
6775
@item @code{void __MTRAP (void)}
6776
@tab @code{__MTRAP ()}
6777
@tab @code{MTRAP}
6778
@item @code{uw2 __MUNPACKH (uw1)}
6779
@tab @code{@var{b} = __MUNPACKH (@var{a})}
6780
@tab @code{MUNPACKH @var{a},@var{b}}
6781
@item @code{uw1 __MWCUT (uw2, uw1)}
6782
@tab @code{@var{c} = __MWCUT (@var{a}, @var{b})}
6783
@tab @code{MWCUT @var{a},@var{b},@var{c}}
6784
@item @code{void __MWTACC (acc, uw1)}
6785
@tab @code{__MWTACC (@var{b}, @var{a})}
6786
@tab @code{MWTACC @var{a},@var{b}}
6787
@item @code{void __MWTACCG (acc, uw1)}
6788
@tab @code{__MWTACCG (@var{b}, @var{a})}
6789
@tab @code{MWTACCG @var{a},@var{b}}
6790
@item @code{uw1 __MXOR (uw1, uw1)}
6791
@tab @code{@var{c} = __MXOR (@var{a}, @var{b})}
6792
@tab @code{MXOR @var{a},@var{b},@var{c}}
6793
@end multitable
6794
 
6795
@node Raw read/write Functions
6796
@subsubsection Raw read/write Functions
6797
 
6798
This sections describes built-in functions related to read and write
6799
instructions to access memory.  These functions generate
6800
@code{membar} instructions to flush the I/O load and stores where
6801
appropriate, as described in Fujitsu's manual described above.
6802
 
6803
@table @code
6804
 
6805
@item unsigned char __builtin_read8 (void *@var{data})
6806
@item unsigned short __builtin_read16 (void *@var{data})
6807
@item unsigned long __builtin_read32 (void *@var{data})
6808
@item unsigned long long __builtin_read64 (void *@var{data})
6809
 
6810
@item void __builtin_write8 (void *@var{data}, unsigned char @var{datum})
6811
@item void __builtin_write16 (void *@var{data}, unsigned short @var{datum})
6812
@item void __builtin_write32 (void *@var{data}, unsigned long @var{datum})
6813
@item void __builtin_write64 (void *@var{data}, unsigned long long @var{datum})
6814
@end table
6815
 
6816
@node Other Built-in Functions
6817
@subsubsection Other Built-in Functions
6818
 
6819
This section describes built-in functions that are not named after
6820
a specific FR-V instruction.
6821
 
6822
@table @code
6823
@item sw2 __IACCreadll (iacc @var{reg})
6824
Return the full 64-bit value of IACC0@.  The @var{reg} argument is reserved
6825
for future expansion and must be 0.
6826
 
6827
@item sw1 __IACCreadl (iacc @var{reg})
6828
Return the value of IACC0H if @var{reg} is 0 and IACC0L if @var{reg} is 1.
6829
Other values of @var{reg} are rejected as invalid.
6830
 
6831
@item void __IACCsetll (iacc @var{reg}, sw2 @var{x})
6832
Set the full 64-bit value of IACC0 to @var{x}.  The @var{reg} argument
6833
is reserved for future expansion and must be 0.
6834
 
6835
@item void __IACCsetl (iacc @var{reg}, sw1 @var{x})
6836
Set IACC0H to @var{x} if @var{reg} is 0 and IACC0L to @var{x} if @var{reg}
6837
is 1.  Other values of @var{reg} are rejected as invalid.
6838
 
6839
@item void __data_prefetch0 (const void *@var{x})
6840
Use the @code{dcpl} instruction to load the contents of address @var{x}
6841
into the data cache.
6842
 
6843
@item void __data_prefetch (const void *@var{x})
6844
Use the @code{nldub} instruction to load the contents of address @var{x}
6845
into the data cache.  The instruction will be issued in slot I1@.
6846
@end table
6847
 
6848
@node X86 Built-in Functions
6849
@subsection X86 Built-in Functions
6850
 
6851
These built-in functions are available for the i386 and x86-64 family
6852
of computers, depending on the command-line switches used.
6853
 
6854
Note that, if you specify command-line switches such as @option{-msse},
6855
the compiler could use the extended instruction sets even if the built-ins
6856
are not used explicitly in the program.  For this reason, applications
6857
which perform runtime CPU detection must compile separate files for each
6858
supported architecture, using the appropriate flags.  In particular,
6859
the file containing the CPU detection code should be compiled without
6860
these options.
6861
 
6862
The following machine modes are available for use with MMX built-in functions
6863
(@pxref{Vector Extensions}): @code{V2SI} for a vector of two 32-bit integers,
6864
@code{V4HI} for a vector of four 16-bit integers, and @code{V8QI} for a
6865
vector of eight 8-bit integers.  Some of the built-in functions operate on
6866
MMX registers as a whole 64-bit entity, these use @code{DI} as their mode.
6867
 
6868
If 3Dnow extensions are enabled, @code{V2SF} is used as a mode for a vector
6869
of two 32-bit floating point values.
6870
 
6871
If SSE extensions are enabled, @code{V4SF} is used for a vector of four 32-bit
6872
floating point values.  Some instructions use a vector of four 32-bit
6873
integers, these use @code{V4SI}.  Finally, some instructions operate on an
6874
entire vector register, interpreting it as a 128-bit integer, these use mode
6875
@code{TI}.
6876
 
6877
The following built-in functions are made available by @option{-mmmx}.
6878
All of them generate the machine instruction that is part of the name.
6879
 
6880
@smallexample
6881
v8qi __builtin_ia32_paddb (v8qi, v8qi)
6882
v4hi __builtin_ia32_paddw (v4hi, v4hi)
6883
v2si __builtin_ia32_paddd (v2si, v2si)
6884
v8qi __builtin_ia32_psubb (v8qi, v8qi)
6885
v4hi __builtin_ia32_psubw (v4hi, v4hi)
6886
v2si __builtin_ia32_psubd (v2si, v2si)
6887
v8qi __builtin_ia32_paddsb (v8qi, v8qi)
6888
v4hi __builtin_ia32_paddsw (v4hi, v4hi)
6889
v8qi __builtin_ia32_psubsb (v8qi, v8qi)
6890
v4hi __builtin_ia32_psubsw (v4hi, v4hi)
6891
v8qi __builtin_ia32_paddusb (v8qi, v8qi)
6892
v4hi __builtin_ia32_paddusw (v4hi, v4hi)
6893
v8qi __builtin_ia32_psubusb (v8qi, v8qi)
6894
v4hi __builtin_ia32_psubusw (v4hi, v4hi)
6895
v4hi __builtin_ia32_pmullw (v4hi, v4hi)
6896
v4hi __builtin_ia32_pmulhw (v4hi, v4hi)
6897
di __builtin_ia32_pand (di, di)
6898
di __builtin_ia32_pandn (di,di)
6899
di __builtin_ia32_por (di, di)
6900
di __builtin_ia32_pxor (di, di)
6901
v8qi __builtin_ia32_pcmpeqb (v8qi, v8qi)
6902
v4hi __builtin_ia32_pcmpeqw (v4hi, v4hi)
6903
v2si __builtin_ia32_pcmpeqd (v2si, v2si)
6904
v8qi __builtin_ia32_pcmpgtb (v8qi, v8qi)
6905
v4hi __builtin_ia32_pcmpgtw (v4hi, v4hi)
6906
v2si __builtin_ia32_pcmpgtd (v2si, v2si)
6907
v8qi __builtin_ia32_punpckhbw (v8qi, v8qi)
6908
v4hi __builtin_ia32_punpckhwd (v4hi, v4hi)
6909
v2si __builtin_ia32_punpckhdq (v2si, v2si)
6910
v8qi __builtin_ia32_punpcklbw (v8qi, v8qi)
6911
v4hi __builtin_ia32_punpcklwd (v4hi, v4hi)
6912
v2si __builtin_ia32_punpckldq (v2si, v2si)
6913
v8qi __builtin_ia32_packsswb (v4hi, v4hi)
6914
v4hi __builtin_ia32_packssdw (v2si, v2si)
6915
v8qi __builtin_ia32_packuswb (v4hi, v4hi)
6916
@end smallexample
6917
 
6918
The following built-in functions are made available either with
6919
@option{-msse}, or with a combination of @option{-m3dnow} and
6920
@option{-march=athlon}.  All of them generate the machine
6921
instruction that is part of the name.
6922
 
6923
@smallexample
6924
v4hi __builtin_ia32_pmulhuw (v4hi, v4hi)
6925
v8qi __builtin_ia32_pavgb (v8qi, v8qi)
6926
v4hi __builtin_ia32_pavgw (v4hi, v4hi)
6927
v4hi __builtin_ia32_psadbw (v8qi, v8qi)
6928
v8qi __builtin_ia32_pmaxub (v8qi, v8qi)
6929
v4hi __builtin_ia32_pmaxsw (v4hi, v4hi)
6930
v8qi __builtin_ia32_pminub (v8qi, v8qi)
6931
v4hi __builtin_ia32_pminsw (v4hi, v4hi)
6932
int __builtin_ia32_pextrw (v4hi, int)
6933
v4hi __builtin_ia32_pinsrw (v4hi, int, int)
6934
int __builtin_ia32_pmovmskb (v8qi)
6935
void __builtin_ia32_maskmovq (v8qi, v8qi, char *)
6936
void __builtin_ia32_movntq (di *, di)
6937
void __builtin_ia32_sfence (void)
6938
@end smallexample
6939
 
6940
The following built-in functions are available when @option{-msse} is used.
6941
All of them generate the machine instruction that is part of the name.
6942
 
6943
@smallexample
6944
int __builtin_ia32_comieq (v4sf, v4sf)
6945
int __builtin_ia32_comineq (v4sf, v4sf)
6946
int __builtin_ia32_comilt (v4sf, v4sf)
6947
int __builtin_ia32_comile (v4sf, v4sf)
6948
int __builtin_ia32_comigt (v4sf, v4sf)
6949
int __builtin_ia32_comige (v4sf, v4sf)
6950
int __builtin_ia32_ucomieq (v4sf, v4sf)
6951
int __builtin_ia32_ucomineq (v4sf, v4sf)
6952
int __builtin_ia32_ucomilt (v4sf, v4sf)
6953
int __builtin_ia32_ucomile (v4sf, v4sf)
6954
int __builtin_ia32_ucomigt (v4sf, v4sf)
6955
int __builtin_ia32_ucomige (v4sf, v4sf)
6956
v4sf __builtin_ia32_addps (v4sf, v4sf)
6957
v4sf __builtin_ia32_subps (v4sf, v4sf)
6958
v4sf __builtin_ia32_mulps (v4sf, v4sf)
6959
v4sf __builtin_ia32_divps (v4sf, v4sf)
6960
v4sf __builtin_ia32_addss (v4sf, v4sf)
6961
v4sf __builtin_ia32_subss (v4sf, v4sf)
6962
v4sf __builtin_ia32_mulss (v4sf, v4sf)
6963
v4sf __builtin_ia32_divss (v4sf, v4sf)
6964
v4si __builtin_ia32_cmpeqps (v4sf, v4sf)
6965
v4si __builtin_ia32_cmpltps (v4sf, v4sf)
6966
v4si __builtin_ia32_cmpleps (v4sf, v4sf)
6967
v4si __builtin_ia32_cmpgtps (v4sf, v4sf)
6968
v4si __builtin_ia32_cmpgeps (v4sf, v4sf)
6969
v4si __builtin_ia32_cmpunordps (v4sf, v4sf)
6970
v4si __builtin_ia32_cmpneqps (v4sf, v4sf)
6971
v4si __builtin_ia32_cmpnltps (v4sf, v4sf)
6972
v4si __builtin_ia32_cmpnleps (v4sf, v4sf)
6973
v4si __builtin_ia32_cmpngtps (v4sf, v4sf)
6974
v4si __builtin_ia32_cmpngeps (v4sf, v4sf)
6975
v4si __builtin_ia32_cmpordps (v4sf, v4sf)
6976
v4si __builtin_ia32_cmpeqss (v4sf, v4sf)
6977
v4si __builtin_ia32_cmpltss (v4sf, v4sf)
6978
v4si __builtin_ia32_cmpless (v4sf, v4sf)
6979
v4si __builtin_ia32_cmpunordss (v4sf, v4sf)
6980
v4si __builtin_ia32_cmpneqss (v4sf, v4sf)
6981
v4si __builtin_ia32_cmpnlts (v4sf, v4sf)
6982
v4si __builtin_ia32_cmpnless (v4sf, v4sf)
6983
v4si __builtin_ia32_cmpordss (v4sf, v4sf)
6984
v4sf __builtin_ia32_maxps (v4sf, v4sf)
6985
v4sf __builtin_ia32_maxss (v4sf, v4sf)
6986
v4sf __builtin_ia32_minps (v4sf, v4sf)
6987
v4sf __builtin_ia32_minss (v4sf, v4sf)
6988
v4sf __builtin_ia32_andps (v4sf, v4sf)
6989
v4sf __builtin_ia32_andnps (v4sf, v4sf)
6990
v4sf __builtin_ia32_orps (v4sf, v4sf)
6991
v4sf __builtin_ia32_xorps (v4sf, v4sf)
6992
v4sf __builtin_ia32_movss (v4sf, v4sf)
6993
v4sf __builtin_ia32_movhlps (v4sf, v4sf)
6994
v4sf __builtin_ia32_movlhps (v4sf, v4sf)
6995
v4sf __builtin_ia32_unpckhps (v4sf, v4sf)
6996
v4sf __builtin_ia32_unpcklps (v4sf, v4sf)
6997
v4sf __builtin_ia32_cvtpi2ps (v4sf, v2si)
6998
v4sf __builtin_ia32_cvtsi2ss (v4sf, int)
6999
v2si __builtin_ia32_cvtps2pi (v4sf)
7000
int __builtin_ia32_cvtss2si (v4sf)
7001
v2si __builtin_ia32_cvttps2pi (v4sf)
7002
int __builtin_ia32_cvttss2si (v4sf)
7003
v4sf __builtin_ia32_rcpps (v4sf)
7004
v4sf __builtin_ia32_rsqrtps (v4sf)
7005
v4sf __builtin_ia32_sqrtps (v4sf)
7006
v4sf __builtin_ia32_rcpss (v4sf)
7007
v4sf __builtin_ia32_rsqrtss (v4sf)
7008
v4sf __builtin_ia32_sqrtss (v4sf)
7009
v4sf __builtin_ia32_shufps (v4sf, v4sf, int)
7010
void __builtin_ia32_movntps (float *, v4sf)
7011
int __builtin_ia32_movmskps (v4sf)
7012
@end smallexample
7013
 
7014
The following built-in functions are available when @option{-msse} is used.
7015
 
7016
@table @code
7017
@item v4sf __builtin_ia32_loadaps (float *)
7018
Generates the @code{movaps} machine instruction as a load from memory.
7019
@item void __builtin_ia32_storeaps (float *, v4sf)
7020
Generates the @code{movaps} machine instruction as a store to memory.
7021
@item v4sf __builtin_ia32_loadups (float *)
7022
Generates the @code{movups} machine instruction as a load from memory.
7023
@item void __builtin_ia32_storeups (float *, v4sf)
7024
Generates the @code{movups} machine instruction as a store to memory.
7025
@item v4sf __builtin_ia32_loadsss (float *)
7026
Generates the @code{movss} machine instruction as a load from memory.
7027
@item void __builtin_ia32_storess (float *, v4sf)
7028
Generates the @code{movss} machine instruction as a store to memory.
7029
@item v4sf __builtin_ia32_loadhps (v4sf, v2si *)
7030
Generates the @code{movhps} machine instruction as a load from memory.
7031
@item v4sf __builtin_ia32_loadlps (v4sf, v2si *)
7032
Generates the @code{movlps} machine instruction as a load from memory
7033
@item void __builtin_ia32_storehps (v4sf, v2si *)
7034
Generates the @code{movhps} machine instruction as a store to memory.
7035
@item void __builtin_ia32_storelps (v4sf, v2si *)
7036
Generates the @code{movlps} machine instruction as a store to memory.
7037
@end table
7038
 
7039
The following built-in functions are available when @option{-msse2} is used.
7040
All of them generate the machine instruction that is part of the name.
7041
 
7042
@smallexample
7043
int __builtin_ia32_comisdeq (v2df, v2df)
7044
int __builtin_ia32_comisdlt (v2df, v2df)
7045
int __builtin_ia32_comisdle (v2df, v2df)
7046
int __builtin_ia32_comisdgt (v2df, v2df)
7047
int __builtin_ia32_comisdge (v2df, v2df)
7048
int __builtin_ia32_comisdneq (v2df, v2df)
7049
int __builtin_ia32_ucomisdeq (v2df, v2df)
7050
int __builtin_ia32_ucomisdlt (v2df, v2df)
7051
int __builtin_ia32_ucomisdle (v2df, v2df)
7052
int __builtin_ia32_ucomisdgt (v2df, v2df)
7053
int __builtin_ia32_ucomisdge (v2df, v2df)
7054
int __builtin_ia32_ucomisdneq (v2df, v2df)
7055
v2df __builtin_ia32_cmpeqpd (v2df, v2df)
7056
v2df __builtin_ia32_cmpltpd (v2df, v2df)
7057
v2df __builtin_ia32_cmplepd (v2df, v2df)
7058
v2df __builtin_ia32_cmpgtpd (v2df, v2df)
7059
v2df __builtin_ia32_cmpgepd (v2df, v2df)
7060
v2df __builtin_ia32_cmpunordpd (v2df, v2df)
7061
v2df __builtin_ia32_cmpneqpd (v2df, v2df)
7062
v2df __builtin_ia32_cmpnltpd (v2df, v2df)
7063
v2df __builtin_ia32_cmpnlepd (v2df, v2df)
7064
v2df __builtin_ia32_cmpngtpd (v2df, v2df)
7065
v2df __builtin_ia32_cmpngepd (v2df, v2df)
7066
v2df __builtin_ia32_cmpordpd (v2df, v2df)
7067
v2df __builtin_ia32_cmpeqsd (v2df, v2df)
7068
v2df __builtin_ia32_cmpltsd (v2df, v2df)
7069
v2df __builtin_ia32_cmplesd (v2df, v2df)
7070
v2df __builtin_ia32_cmpunordsd (v2df, v2df)
7071
v2df __builtin_ia32_cmpneqsd (v2df, v2df)
7072
v2df __builtin_ia32_cmpnltsd (v2df, v2df)
7073
v2df __builtin_ia32_cmpnlesd (v2df, v2df)
7074
v2df __builtin_ia32_cmpordsd (v2df, v2df)
7075
v2di __builtin_ia32_paddq (v2di, v2di)
7076
v2di __builtin_ia32_psubq (v2di, v2di)
7077
v2df __builtin_ia32_addpd (v2df, v2df)
7078
v2df __builtin_ia32_subpd (v2df, v2df)
7079
v2df __builtin_ia32_mulpd (v2df, v2df)
7080
v2df __builtin_ia32_divpd (v2df, v2df)
7081
v2df __builtin_ia32_addsd (v2df, v2df)
7082
v2df __builtin_ia32_subsd (v2df, v2df)
7083
v2df __builtin_ia32_mulsd (v2df, v2df)
7084
v2df __builtin_ia32_divsd (v2df, v2df)
7085
v2df __builtin_ia32_minpd (v2df, v2df)
7086
v2df __builtin_ia32_maxpd (v2df, v2df)
7087
v2df __builtin_ia32_minsd (v2df, v2df)
7088
v2df __builtin_ia32_maxsd (v2df, v2df)
7089
v2df __builtin_ia32_andpd (v2df, v2df)
7090
v2df __builtin_ia32_andnpd (v2df, v2df)
7091
v2df __builtin_ia32_orpd (v2df, v2df)
7092
v2df __builtin_ia32_xorpd (v2df, v2df)
7093
v2df __builtin_ia32_movsd (v2df, v2df)
7094
v2df __builtin_ia32_unpckhpd (v2df, v2df)
7095
v2df __builtin_ia32_unpcklpd (v2df, v2df)
7096
v16qi __builtin_ia32_paddb128 (v16qi, v16qi)
7097
v8hi __builtin_ia32_paddw128 (v8hi, v8hi)
7098
v4si __builtin_ia32_paddd128 (v4si, v4si)
7099
v2di __builtin_ia32_paddq128 (v2di, v2di)
7100
v16qi __builtin_ia32_psubb128 (v16qi, v16qi)
7101
v8hi __builtin_ia32_psubw128 (v8hi, v8hi)
7102
v4si __builtin_ia32_psubd128 (v4si, v4si)
7103
v2di __builtin_ia32_psubq128 (v2di, v2di)
7104
v8hi __builtin_ia32_pmullw128 (v8hi, v8hi)
7105
v8hi __builtin_ia32_pmulhw128 (v8hi, v8hi)
7106
v2di __builtin_ia32_pand128 (v2di, v2di)
7107
v2di __builtin_ia32_pandn128 (v2di, v2di)
7108
v2di __builtin_ia32_por128 (v2di, v2di)
7109
v2di __builtin_ia32_pxor128 (v2di, v2di)
7110
v16qi __builtin_ia32_pavgb128 (v16qi, v16qi)
7111
v8hi __builtin_ia32_pavgw128 (v8hi, v8hi)
7112
v16qi __builtin_ia32_pcmpeqb128 (v16qi, v16qi)
7113
v8hi __builtin_ia32_pcmpeqw128 (v8hi, v8hi)
7114
v4si __builtin_ia32_pcmpeqd128 (v4si, v4si)
7115
v16qi __builtin_ia32_pcmpgtb128 (v16qi, v16qi)
7116
v8hi __builtin_ia32_pcmpgtw128 (v8hi, v8hi)
7117
v4si __builtin_ia32_pcmpgtd128 (v4si, v4si)
7118
v16qi __builtin_ia32_pmaxub128 (v16qi, v16qi)
7119
v8hi __builtin_ia32_pmaxsw128 (v8hi, v8hi)
7120
v16qi __builtin_ia32_pminub128 (v16qi, v16qi)
7121
v8hi __builtin_ia32_pminsw128 (v8hi, v8hi)
7122
v16qi __builtin_ia32_punpckhbw128 (v16qi, v16qi)
7123
v8hi __builtin_ia32_punpckhwd128 (v8hi, v8hi)
7124
v4si __builtin_ia32_punpckhdq128 (v4si, v4si)
7125
v2di __builtin_ia32_punpckhqdq128 (v2di, v2di)
7126
v16qi __builtin_ia32_punpcklbw128 (v16qi, v16qi)
7127
v8hi __builtin_ia32_punpcklwd128 (v8hi, v8hi)
7128
v4si __builtin_ia32_punpckldq128 (v4si, v4si)
7129
v2di __builtin_ia32_punpcklqdq128 (v2di, v2di)
7130
v16qi __builtin_ia32_packsswb128 (v16qi, v16qi)
7131
v8hi __builtin_ia32_packssdw128 (v8hi, v8hi)
7132
v16qi __builtin_ia32_packuswb128 (v16qi, v16qi)
7133
v8hi __builtin_ia32_pmulhuw128 (v8hi, v8hi)
7134
void __builtin_ia32_maskmovdqu (v16qi, v16qi)
7135
v2df __builtin_ia32_loadupd (double *)
7136
void __builtin_ia32_storeupd (double *, v2df)
7137
v2df __builtin_ia32_loadhpd (v2df, double *)
7138
v2df __builtin_ia32_loadlpd (v2df, double *)
7139
int __builtin_ia32_movmskpd (v2df)
7140
int __builtin_ia32_pmovmskb128 (v16qi)
7141
void __builtin_ia32_movnti (int *, int)
7142
void __builtin_ia32_movntpd (double *, v2df)
7143
void __builtin_ia32_movntdq (v2df *, v2df)
7144
v4si __builtin_ia32_pshufd (v4si, int)
7145
v8hi __builtin_ia32_pshuflw (v8hi, int)
7146
v8hi __builtin_ia32_pshufhw (v8hi, int)
7147
v2di __builtin_ia32_psadbw128 (v16qi, v16qi)
7148
v2df __builtin_ia32_sqrtpd (v2df)
7149
v2df __builtin_ia32_sqrtsd (v2df)
7150
v2df __builtin_ia32_shufpd (v2df, v2df, int)
7151
v2df __builtin_ia32_cvtdq2pd (v4si)
7152
v4sf __builtin_ia32_cvtdq2ps (v4si)
7153
v4si __builtin_ia32_cvtpd2dq (v2df)
7154
v2si __builtin_ia32_cvtpd2pi (v2df)
7155
v4sf __builtin_ia32_cvtpd2ps (v2df)
7156
v4si __builtin_ia32_cvttpd2dq (v2df)
7157
v2si __builtin_ia32_cvttpd2pi (v2df)
7158
v2df __builtin_ia32_cvtpi2pd (v2si)
7159
int __builtin_ia32_cvtsd2si (v2df)
7160
int __builtin_ia32_cvttsd2si (v2df)
7161
long long __builtin_ia32_cvtsd2si64 (v2df)
7162
long long __builtin_ia32_cvttsd2si64 (v2df)
7163
v4si __builtin_ia32_cvtps2dq (v4sf)
7164
v2df __builtin_ia32_cvtps2pd (v4sf)
7165
v4si __builtin_ia32_cvttps2dq (v4sf)
7166
v2df __builtin_ia32_cvtsi2sd (v2df, int)
7167
v2df __builtin_ia32_cvtsi642sd (v2df, long long)
7168
v4sf __builtin_ia32_cvtsd2ss (v4sf, v2df)
7169
v2df __builtin_ia32_cvtss2sd (v2df, v4sf)
7170
void __builtin_ia32_clflush (const void *)
7171
void __builtin_ia32_lfence (void)
7172
void __builtin_ia32_mfence (void)
7173
v16qi __builtin_ia32_loaddqu (const char *)
7174
void __builtin_ia32_storedqu (char *, v16qi)
7175
unsigned long long __builtin_ia32_pmuludq (v2si, v2si)
7176
v2di __builtin_ia32_pmuludq128 (v4si, v4si)
7177
v8hi __builtin_ia32_psllw128 (v8hi, v2di)
7178
v4si __builtin_ia32_pslld128 (v4si, v2di)
7179
v2di __builtin_ia32_psllq128 (v4si, v2di)
7180
v8hi __builtin_ia32_psrlw128 (v8hi, v2di)
7181
v4si __builtin_ia32_psrld128 (v4si, v2di)
7182
v2di __builtin_ia32_psrlq128 (v2di, v2di)
7183
v8hi __builtin_ia32_psraw128 (v8hi, v2di)
7184
v4si __builtin_ia32_psrad128 (v4si, v2di)
7185
v2di __builtin_ia32_pslldqi128 (v2di, int)
7186
v8hi __builtin_ia32_psllwi128 (v8hi, int)
7187
v4si __builtin_ia32_pslldi128 (v4si, int)
7188
v2di __builtin_ia32_psllqi128 (v2di, int)
7189
v2di __builtin_ia32_psrldqi128 (v2di, int)
7190
v8hi __builtin_ia32_psrlwi128 (v8hi, int)
7191
v4si __builtin_ia32_psrldi128 (v4si, int)
7192
v2di __builtin_ia32_psrlqi128 (v2di, int)
7193
v8hi __builtin_ia32_psrawi128 (v8hi, int)
7194
v4si __builtin_ia32_psradi128 (v4si, int)
7195
v4si __builtin_ia32_pmaddwd128 (v8hi, v8hi)
7196
@end smallexample
7197
 
7198
The following built-in functions are available when @option{-msse3} is used.
7199
All of them generate the machine instruction that is part of the name.
7200
 
7201
@smallexample
7202
v2df __builtin_ia32_addsubpd (v2df, v2df)
7203
v4sf __builtin_ia32_addsubps (v4sf, v4sf)
7204
v2df __builtin_ia32_haddpd (v2df, v2df)
7205
v4sf __builtin_ia32_haddps (v4sf, v4sf)
7206
v2df __builtin_ia32_hsubpd (v2df, v2df)
7207
v4sf __builtin_ia32_hsubps (v4sf, v4sf)
7208
v16qi __builtin_ia32_lddqu (char const *)
7209
void __builtin_ia32_monitor (void *, unsigned int, unsigned int)
7210
v2df __builtin_ia32_movddup (v2df)
7211
v4sf __builtin_ia32_movshdup (v4sf)
7212
v4sf __builtin_ia32_movsldup (v4sf)
7213
void __builtin_ia32_mwait (unsigned int, unsigned int)
7214
@end smallexample
7215
 
7216
The following built-in functions are available when @option{-msse3} is used.
7217
 
7218
@table @code
7219
@item v2df __builtin_ia32_loadddup (double const *)
7220
Generates the @code{movddup} machine instruction as a load from memory.
7221
@end table
7222
 
7223
The following built-in functions are available when @option{-m3dnow} is used.
7224
All of them generate the machine instruction that is part of the name.
7225
 
7226
@smallexample
7227
void __builtin_ia32_femms (void)
7228
v8qi __builtin_ia32_pavgusb (v8qi, v8qi)
7229
v2si __builtin_ia32_pf2id (v2sf)
7230
v2sf __builtin_ia32_pfacc (v2sf, v2sf)
7231
v2sf __builtin_ia32_pfadd (v2sf, v2sf)
7232
v2si __builtin_ia32_pfcmpeq (v2sf, v2sf)
7233
v2si __builtin_ia32_pfcmpge (v2sf, v2sf)
7234
v2si __builtin_ia32_pfcmpgt (v2sf, v2sf)
7235
v2sf __builtin_ia32_pfmax (v2sf, v2sf)
7236
v2sf __builtin_ia32_pfmin (v2sf, v2sf)
7237
v2sf __builtin_ia32_pfmul (v2sf, v2sf)
7238
v2sf __builtin_ia32_pfrcp (v2sf)
7239
v2sf __builtin_ia32_pfrcpit1 (v2sf, v2sf)
7240
v2sf __builtin_ia32_pfrcpit2 (v2sf, v2sf)
7241
v2sf __builtin_ia32_pfrsqrt (v2sf)
7242
v2sf __builtin_ia32_pfrsqrtit1 (v2sf, v2sf)
7243
v2sf __builtin_ia32_pfsub (v2sf, v2sf)
7244
v2sf __builtin_ia32_pfsubr (v2sf, v2sf)
7245
v2sf __builtin_ia32_pi2fd (v2si)
7246
v4hi __builtin_ia32_pmulhrw (v4hi, v4hi)
7247
@end smallexample
7248
 
7249
The following built-in functions are available when both @option{-m3dnow}
7250
and @option{-march=athlon} are used.  All of them generate the machine
7251
instruction that is part of the name.
7252
 
7253
@smallexample
7254
v2si __builtin_ia32_pf2iw (v2sf)
7255
v2sf __builtin_ia32_pfnacc (v2sf, v2sf)
7256
v2sf __builtin_ia32_pfpnacc (v2sf, v2sf)
7257
v2sf __builtin_ia32_pi2fw (v2si)
7258
v2sf __builtin_ia32_pswapdsf (v2sf)
7259
v2si __builtin_ia32_pswapdsi (v2si)
7260
@end smallexample
7261
 
7262
@node MIPS DSP Built-in Functions
7263
@subsection MIPS DSP Built-in Functions
7264
 
7265
The MIPS DSP Application-Specific Extension (ASE) includes new
7266
instructions that are designed to improve the performance of DSP and
7267
media applications.  It provides instructions that operate on packed
7268
8-bit integer data, Q15 fractional data and Q31 fractional data.
7269
 
7270
GCC supports MIPS DSP operations using both the generic
7271
vector extensions (@pxref{Vector Extensions}) and a collection of
7272
MIPS-specific built-in functions.  Both kinds of support are
7273
enabled by the @option{-mdsp} command-line option.
7274
 
7275
At present, GCC only provides support for operations on 32-bit
7276
vectors.  The vector type associated with 8-bit integer data is
7277
usually called @code{v4i8} and the vector type associated with Q15 is
7278
usually called @code{v2q15}.  They can be defined in C as follows:
7279
 
7280
@smallexample
7281
typedef char v4i8 __attribute__ ((vector_size(4)));
7282
typedef short v2q15 __attribute__ ((vector_size(4)));
7283
@end smallexample
7284
 
7285
@code{v4i8} and @code{v2q15} values are initialized in the same way as
7286
aggregates.  For example:
7287
 
7288
@smallexample
7289
v4i8 a = @{1, 2, 3, 4@};
7290
v4i8 b;
7291
b = (v4i8) @{5, 6, 7, 8@};
7292
 
7293
v2q15 c = @{0x0fcb, 0x3a75@};
7294
v2q15 d;
7295
d = (v2q15) @{0.1234 * 0x1.0p15, 0.4567 * 0x1.0p15@};
7296
@end smallexample
7297
 
7298
@emph{Note:} The CPU's endianness determines the order in which values
7299
are packed.  On little-endian targets, the first value is the least
7300
significant and the last value is the most significant.  The opposite
7301
order applies to big-endian targets.  For example, the code above will
7302
set the lowest byte of @code{a} to @code{1} on little-endian targets
7303
and @code{4} on big-endian targets.
7304
 
7305
@emph{Note:} Q15 and Q31 values must be initialized with their integer
7306
representation.  As shown in this example, the integer representation
7307
of a Q15 value can be obtained by multiplying the fractional value by
7308
@code{0x1.0p15}.  The equivalent for Q31 values is to multiply by
7309
@code{0x1.0p31}.
7310
 
7311
The table below lists the @code{v4i8} and @code{v2q15} operations for which
7312
hardware support exists.  @code{a} and @code{b} are @code{v4i8} values,
7313
and @code{c} and @code{d} are @code{v2q15} values.
7314
 
7315
@multitable @columnfractions .50 .50
7316
@item C code @tab MIPS instruction
7317
@item @code{a + b} @tab @code{addu.qb}
7318
@item @code{c + d} @tab @code{addq.ph}
7319
@item @code{a - b} @tab @code{subu.qb}
7320
@item @code{c - d} @tab @code{subq.ph}
7321
@end multitable
7322
 
7323
It is easier to describe the DSP built-in functions if we first define
7324
the following types:
7325
 
7326
@smallexample
7327
typedef int q31;
7328
typedef int i32;
7329
typedef long long a64;
7330
@end smallexample
7331
 
7332
@code{q31} and @code{i32} are actually the same as @code{int}, but we
7333
use @code{q31} to indicate a Q31 fractional value and @code{i32} to
7334
indicate a 32-bit integer value.  Similarly, @code{a64} is the same as
7335
@code{long long}, but we use @code{a64} to indicate values that will
7336
be placed in one of the four DSP accumulators (@code{$ac0},
7337
@code{$ac1}, @code{$ac2} or @code{$ac3}).
7338
 
7339
Also, some built-in functions prefer or require immediate numbers as
7340
parameters, because the corresponding DSP instructions accept both immediate
7341
numbers and register operands, or accept immediate numbers only.  The
7342
immediate parameters are listed as follows.
7343
 
7344
@smallexample
7345
imm0_7: 0 to 7.
7346
imm0_15: 0 to 15.
7347
imm0_31: 0 to 31.
7348
imm0_63: 0 to 63.
7349
imm0_255: 0 to 255.
7350
imm_n32_31: -32 to 31.
7351
imm_n512_511: -512 to 511.
7352
@end smallexample
7353
 
7354
The following built-in functions map directly to a particular MIPS DSP
7355
instruction.  Please refer to the architecture specification
7356
for details on what each instruction does.
7357
 
7358
@smallexample
7359
v2q15 __builtin_mips_addq_ph (v2q15, v2q15)
7360
v2q15 __builtin_mips_addq_s_ph (v2q15, v2q15)
7361
q31 __builtin_mips_addq_s_w (q31, q31)
7362
v4i8 __builtin_mips_addu_qb (v4i8, v4i8)
7363
v4i8 __builtin_mips_addu_s_qb (v4i8, v4i8)
7364
v2q15 __builtin_mips_subq_ph (v2q15, v2q15)
7365
v2q15 __builtin_mips_subq_s_ph (v2q15, v2q15)
7366
q31 __builtin_mips_subq_s_w (q31, q31)
7367
v4i8 __builtin_mips_subu_qb (v4i8, v4i8)
7368
v4i8 __builtin_mips_subu_s_qb (v4i8, v4i8)
7369
i32 __builtin_mips_addsc (i32, i32)
7370
i32 __builtin_mips_addwc (i32, i32)
7371
i32 __builtin_mips_modsub (i32, i32)
7372
i32 __builtin_mips_raddu_w_qb (v4i8)
7373
v2q15 __builtin_mips_absq_s_ph (v2q15)
7374
q31 __builtin_mips_absq_s_w (q31)
7375
v4i8 __builtin_mips_precrq_qb_ph (v2q15, v2q15)
7376
v2q15 __builtin_mips_precrq_ph_w (q31, q31)
7377
v2q15 __builtin_mips_precrq_rs_ph_w (q31, q31)
7378
v4i8 __builtin_mips_precrqu_s_qb_ph (v2q15, v2q15)
7379
q31 __builtin_mips_preceq_w_phl (v2q15)
7380
q31 __builtin_mips_preceq_w_phr (v2q15)
7381
v2q15 __builtin_mips_precequ_ph_qbl (v4i8)
7382
v2q15 __builtin_mips_precequ_ph_qbr (v4i8)
7383
v2q15 __builtin_mips_precequ_ph_qbla (v4i8)
7384
v2q15 __builtin_mips_precequ_ph_qbra (v4i8)
7385
v2q15 __builtin_mips_preceu_ph_qbl (v4i8)
7386
v2q15 __builtin_mips_preceu_ph_qbr (v4i8)
7387
v2q15 __builtin_mips_preceu_ph_qbla (v4i8)
7388
v2q15 __builtin_mips_preceu_ph_qbra (v4i8)
7389
v4i8 __builtin_mips_shll_qb (v4i8, imm0_7)
7390
v4i8 __builtin_mips_shll_qb (v4i8, i32)
7391
v2q15 __builtin_mips_shll_ph (v2q15, imm0_15)
7392
v2q15 __builtin_mips_shll_ph (v2q15, i32)
7393
v2q15 __builtin_mips_shll_s_ph (v2q15, imm0_15)
7394
v2q15 __builtin_mips_shll_s_ph (v2q15, i32)
7395
q31 __builtin_mips_shll_s_w (q31, imm0_31)
7396
q31 __builtin_mips_shll_s_w (q31, i32)
7397
v4i8 __builtin_mips_shrl_qb (v4i8, imm0_7)
7398
v4i8 __builtin_mips_shrl_qb (v4i8, i32)
7399
v2q15 __builtin_mips_shra_ph (v2q15, imm0_15)
7400
v2q15 __builtin_mips_shra_ph (v2q15, i32)
7401
v2q15 __builtin_mips_shra_r_ph (v2q15, imm0_15)
7402
v2q15 __builtin_mips_shra_r_ph (v2q15, i32)
7403
q31 __builtin_mips_shra_r_w (q31, imm0_31)
7404
q31 __builtin_mips_shra_r_w (q31, i32)
7405
v2q15 __builtin_mips_muleu_s_ph_qbl (v4i8, v2q15)
7406
v2q15 __builtin_mips_muleu_s_ph_qbr (v4i8, v2q15)
7407
v2q15 __builtin_mips_mulq_rs_ph (v2q15, v2q15)
7408
q31 __builtin_mips_muleq_s_w_phl (v2q15, v2q15)
7409
q31 __builtin_mips_muleq_s_w_phr (v2q15, v2q15)
7410
a64 __builtin_mips_dpau_h_qbl (a64, v4i8, v4i8)
7411
a64 __builtin_mips_dpau_h_qbr (a64, v4i8, v4i8)
7412
a64 __builtin_mips_dpsu_h_qbl (a64, v4i8, v4i8)
7413
a64 __builtin_mips_dpsu_h_qbr (a64, v4i8, v4i8)
7414
a64 __builtin_mips_dpaq_s_w_ph (a64, v2q15, v2q15)
7415
a64 __builtin_mips_dpaq_sa_l_w (a64, q31, q31)
7416
a64 __builtin_mips_dpsq_s_w_ph (a64, v2q15, v2q15)
7417
a64 __builtin_mips_dpsq_sa_l_w (a64, q31, q31)
7418
a64 __builtin_mips_mulsaq_s_w_ph (a64, v2q15, v2q15)
7419
a64 __builtin_mips_maq_s_w_phl (a64, v2q15, v2q15)
7420
a64 __builtin_mips_maq_s_w_phr (a64, v2q15, v2q15)
7421
a64 __builtin_mips_maq_sa_w_phl (a64, v2q15, v2q15)
7422
a64 __builtin_mips_maq_sa_w_phr (a64, v2q15, v2q15)
7423
i32 __builtin_mips_bitrev (i32)
7424
i32 __builtin_mips_insv (i32, i32)
7425
v4i8 __builtin_mips_repl_qb (imm0_255)
7426
v4i8 __builtin_mips_repl_qb (i32)
7427
v2q15 __builtin_mips_repl_ph (imm_n512_511)
7428
v2q15 __builtin_mips_repl_ph (i32)
7429
void __builtin_mips_cmpu_eq_qb (v4i8, v4i8)
7430
void __builtin_mips_cmpu_lt_qb (v4i8, v4i8)
7431
void __builtin_mips_cmpu_le_qb (v4i8, v4i8)
7432
i32 __builtin_mips_cmpgu_eq_qb (v4i8, v4i8)
7433
i32 __builtin_mips_cmpgu_lt_qb (v4i8, v4i8)
7434
i32 __builtin_mips_cmpgu_le_qb (v4i8, v4i8)
7435
void __builtin_mips_cmp_eq_ph (v2q15, v2q15)
7436
void __builtin_mips_cmp_lt_ph (v2q15, v2q15)
7437
void __builtin_mips_cmp_le_ph (v2q15, v2q15)
7438
v4i8 __builtin_mips_pick_qb (v4i8, v4i8)
7439
v2q15 __builtin_mips_pick_ph (v2q15, v2q15)
7440
v2q15 __builtin_mips_packrl_ph (v2q15, v2q15)
7441
i32 __builtin_mips_extr_w (a64, imm0_31)
7442
i32 __builtin_mips_extr_w (a64, i32)
7443
i32 __builtin_mips_extr_r_w (a64, imm0_31)
7444
i32 __builtin_mips_extr_s_h (a64, i32)
7445
i32 __builtin_mips_extr_rs_w (a64, imm0_31)
7446
i32 __builtin_mips_extr_rs_w (a64, i32)
7447
i32 __builtin_mips_extr_s_h (a64, imm0_31)
7448
i32 __builtin_mips_extr_r_w (a64, i32)
7449
i32 __builtin_mips_extp (a64, imm0_31)
7450
i32 __builtin_mips_extp (a64, i32)
7451
i32 __builtin_mips_extpdp (a64, imm0_31)
7452
i32 __builtin_mips_extpdp (a64, i32)
7453
a64 __builtin_mips_shilo (a64, imm_n32_31)
7454
a64 __builtin_mips_shilo (a64, i32)
7455
a64 __builtin_mips_mthlip (a64, i32)
7456
void __builtin_mips_wrdsp (i32, imm0_63)
7457
i32 __builtin_mips_rddsp (imm0_63)
7458
i32 __builtin_mips_lbux (void *, i32)
7459
i32 __builtin_mips_lhx (void *, i32)
7460
i32 __builtin_mips_lwx (void *, i32)
7461
i32 __builtin_mips_bposge32 (void)
7462
@end smallexample
7463
 
7464
@node MIPS Paired-Single Support
7465
@subsection MIPS Paired-Single Support
7466
 
7467
The MIPS64 architecture includes a number of instructions that
7468
operate on pairs of single-precision floating-point values.
7469
Each pair is packed into a 64-bit floating-point register,
7470
with one element being designated the ``upper half'' and
7471
the other being designated the ``lower half''.
7472
 
7473
GCC supports paired-single operations using both the generic
7474
vector extensions (@pxref{Vector Extensions}) and a collection of
7475
MIPS-specific built-in functions.  Both kinds of support are
7476
enabled by the @option{-mpaired-single} command-line option.
7477
 
7478
The vector type associated with paired-single values is usually
7479
called @code{v2sf}.  It can be defined in C as follows:
7480
 
7481
@smallexample
7482
typedef float v2sf __attribute__ ((vector_size (8)));
7483
@end smallexample
7484
 
7485
@code{v2sf} values are initialized in the same way as aggregates.
7486
For example:
7487
 
7488
@smallexample
7489
v2sf a = @{1.5, 9.1@};
7490
v2sf b;
7491
float e, f;
7492
b = (v2sf) @{e, f@};
7493
@end smallexample
7494
 
7495
@emph{Note:} The CPU's endianness determines which value is stored in
7496
the upper half of a register and which value is stored in the lower half.
7497
On little-endian targets, the first value is the lower one and the second
7498
value is the upper one.  The opposite order applies to big-endian targets.
7499
For example, the code above will set the lower half of @code{a} to
7500
@code{1.5} on little-endian targets and @code{9.1} on big-endian targets.
7501
 
7502
@menu
7503
* Paired-Single Arithmetic::
7504
* Paired-Single Built-in Functions::
7505
* MIPS-3D Built-in Functions::
7506
@end menu
7507
 
7508
@node Paired-Single Arithmetic
7509
@subsubsection Paired-Single Arithmetic
7510
 
7511
The table below lists the @code{v2sf} operations for which hardware
7512
support exists.  @code{a}, @code{b} and @code{c} are @code{v2sf}
7513
values and @code{x} is an integral value.
7514
 
7515
@multitable @columnfractions .50 .50
7516
@item C code @tab MIPS instruction
7517
@item @code{a + b} @tab @code{add.ps}
7518
@item @code{a - b} @tab @code{sub.ps}
7519
@item @code{-a} @tab @code{neg.ps}
7520
@item @code{a * b} @tab @code{mul.ps}
7521
@item @code{a * b + c} @tab @code{madd.ps}
7522
@item @code{a * b - c} @tab @code{msub.ps}
7523
@item @code{-(a * b + c)} @tab @code{nmadd.ps}
7524
@item @code{-(a * b - c)} @tab @code{nmsub.ps}
7525
@item @code{x ? a : b} @tab @code{movn.ps}/@code{movz.ps}
7526
@end multitable
7527
 
7528
Note that the multiply-accumulate instructions can be disabled
7529
using the command-line option @code{-mno-fused-madd}.
7530
 
7531
@node Paired-Single Built-in Functions
7532
@subsubsection Paired-Single Built-in Functions
7533
 
7534
The following paired-single functions map directly to a particular
7535
MIPS instruction.  Please refer to the architecture specification
7536
for details on what each instruction does.
7537
 
7538
@table @code
7539
@item v2sf __builtin_mips_pll_ps (v2sf, v2sf)
7540
Pair lower lower (@code{pll.ps}).
7541
 
7542
@item v2sf __builtin_mips_pul_ps (v2sf, v2sf)
7543
Pair upper lower (@code{pul.ps}).
7544
 
7545
@item v2sf __builtin_mips_plu_ps (v2sf, v2sf)
7546
Pair lower upper (@code{plu.ps}).
7547
 
7548
@item v2sf __builtin_mips_puu_ps (v2sf, v2sf)
7549
Pair upper upper (@code{puu.ps}).
7550
 
7551
@item v2sf __builtin_mips_cvt_ps_s (float, float)
7552
Convert pair to paired single (@code{cvt.ps.s}).
7553
 
7554
@item float __builtin_mips_cvt_s_pl (v2sf)
7555
Convert pair lower to single (@code{cvt.s.pl}).
7556
 
7557
@item float __builtin_mips_cvt_s_pu (v2sf)
7558
Convert pair upper to single (@code{cvt.s.pu}).
7559
 
7560
@item v2sf __builtin_mips_abs_ps (v2sf)
7561
Absolute value (@code{abs.ps}).
7562
 
7563
@item v2sf __builtin_mips_alnv_ps (v2sf, v2sf, int)
7564
Align variable (@code{alnv.ps}).
7565
 
7566
@emph{Note:} The value of the third parameter must be 0 or 4
7567
modulo 8, otherwise the result will be unpredictable.  Please read the
7568
instruction description for details.
7569
@end table
7570
 
7571
The following multi-instruction functions are also available.
7572
In each case, @var{cond} can be any of the 16 floating-point conditions:
7573
@code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult},
7574
@code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq}, @code{ngl},
7575
@code{lt}, @code{nge}, @code{le} or @code{ngt}.
7576
 
7577
@table @code
7578
@item v2sf __builtin_mips_movt_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7579
@itemx v2sf __builtin_mips_movf_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7580
Conditional move based on floating point comparison (@code{c.@var{cond}.ps},
7581
@code{movt.ps}/@code{movf.ps}).
7582
 
7583
The @code{movt} functions return the value @var{x} computed by:
7584
 
7585
@smallexample
7586
c.@var{cond}.ps @var{cc},@var{a},@var{b}
7587
mov.ps @var{x},@var{c}
7588
movt.ps @var{x},@var{d},@var{cc}
7589
@end smallexample
7590
 
7591
The @code{movf} functions are similar but use @code{movf.ps} instead
7592
of @code{movt.ps}.
7593
 
7594
@item int __builtin_mips_upper_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7595
@itemx int __builtin_mips_lower_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7596
Comparison of two paired-single values (@code{c.@var{cond}.ps},
7597
@code{bc1t}/@code{bc1f}).
7598
 
7599
These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps}
7600
and return either the upper or lower half of the result.  For example:
7601
 
7602
@smallexample
7603
v2sf a, b;
7604
if (__builtin_mips_upper_c_eq_ps (a, b))
7605
  upper_halves_are_equal ();
7606
else
7607
  upper_halves_are_unequal ();
7608
 
7609
if (__builtin_mips_lower_c_eq_ps (a, b))
7610
  lower_halves_are_equal ();
7611
else
7612
  lower_halves_are_unequal ();
7613
@end smallexample
7614
@end table
7615
 
7616
@node MIPS-3D Built-in Functions
7617
@subsubsection MIPS-3D Built-in Functions
7618
 
7619
The MIPS-3D Application-Specific Extension (ASE) includes additional
7620
paired-single instructions that are designed to improve the performance
7621
of 3D graphics operations.  Support for these instructions is controlled
7622
by the @option{-mips3d} command-line option.
7623
 
7624
The functions listed below map directly to a particular MIPS-3D
7625
instruction.  Please refer to the architecture specification for
7626
more details on what each instruction does.
7627
 
7628
@table @code
7629
@item v2sf __builtin_mips_addr_ps (v2sf, v2sf)
7630
Reduction add (@code{addr.ps}).
7631
 
7632
@item v2sf __builtin_mips_mulr_ps (v2sf, v2sf)
7633
Reduction multiply (@code{mulr.ps}).
7634
 
7635
@item v2sf __builtin_mips_cvt_pw_ps (v2sf)
7636
Convert paired single to paired word (@code{cvt.pw.ps}).
7637
 
7638
@item v2sf __builtin_mips_cvt_ps_pw (v2sf)
7639
Convert paired word to paired single (@code{cvt.ps.pw}).
7640
 
7641
@item float __builtin_mips_recip1_s (float)
7642
@itemx double __builtin_mips_recip1_d (double)
7643
@itemx v2sf __builtin_mips_recip1_ps (v2sf)
7644
Reduced precision reciprocal (sequence step 1) (@code{recip1.@var{fmt}}).
7645
 
7646
@item float __builtin_mips_recip2_s (float, float)
7647
@itemx double __builtin_mips_recip2_d (double, double)
7648
@itemx v2sf __builtin_mips_recip2_ps (v2sf, v2sf)
7649
Reduced precision reciprocal (sequence step 2) (@code{recip2.@var{fmt}}).
7650
 
7651
@item float __builtin_mips_rsqrt1_s (float)
7652
@itemx double __builtin_mips_rsqrt1_d (double)
7653
@itemx v2sf __builtin_mips_rsqrt1_ps (v2sf)
7654
Reduced precision reciprocal square root (sequence step 1)
7655
(@code{rsqrt1.@var{fmt}}).
7656
 
7657
@item float __builtin_mips_rsqrt2_s (float, float)
7658
@itemx double __builtin_mips_rsqrt2_d (double, double)
7659
@itemx v2sf __builtin_mips_rsqrt2_ps (v2sf, v2sf)
7660
Reduced precision reciprocal square root (sequence step 2)
7661
(@code{rsqrt2.@var{fmt}}).
7662
@end table
7663
 
7664
The following multi-instruction functions are also available.
7665
In each case, @var{cond} can be any of the 16 floating-point conditions:
7666
@code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult},
7667
@code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq},
7668
@code{ngl}, @code{lt}, @code{nge}, @code{le} or @code{ngt}.
7669
 
7670
@table @code
7671
@item int __builtin_mips_cabs_@var{cond}_s (float @var{a}, float @var{b})
7672
@itemx int __builtin_mips_cabs_@var{cond}_d (double @var{a}, double @var{b})
7673
Absolute comparison of two scalar values (@code{cabs.@var{cond}.@var{fmt}},
7674
@code{bc1t}/@code{bc1f}).
7675
 
7676
These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.s}
7677
or @code{cabs.@var{cond}.d} and return the result as a boolean value.
7678
For example:
7679
 
7680
@smallexample
7681
float a, b;
7682
if (__builtin_mips_cabs_eq_s (a, b))
7683
  true ();
7684
else
7685
  false ();
7686
@end smallexample
7687
 
7688
@item int __builtin_mips_upper_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7689
@itemx int __builtin_mips_lower_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7690
Absolute comparison of two paired-single values (@code{cabs.@var{cond}.ps},
7691
@code{bc1t}/@code{bc1f}).
7692
 
7693
These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.ps}
7694
and return either the upper or lower half of the result.  For example:
7695
 
7696
@smallexample
7697
v2sf a, b;
7698
if (__builtin_mips_upper_cabs_eq_ps (a, b))
7699
  upper_halves_are_equal ();
7700
else
7701
  upper_halves_are_unequal ();
7702
 
7703
if (__builtin_mips_lower_cabs_eq_ps (a, b))
7704
  lower_halves_are_equal ();
7705
else
7706
  lower_halves_are_unequal ();
7707
@end smallexample
7708
 
7709
@item v2sf __builtin_mips_movt_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7710
@itemx v2sf __builtin_mips_movf_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7711
Conditional move based on absolute comparison (@code{cabs.@var{cond}.ps},
7712
@code{movt.ps}/@code{movf.ps}).
7713
 
7714
The @code{movt} functions return the value @var{x} computed by:
7715
 
7716
@smallexample
7717
cabs.@var{cond}.ps @var{cc},@var{a},@var{b}
7718
mov.ps @var{x},@var{c}
7719
movt.ps @var{x},@var{d},@var{cc}
7720
@end smallexample
7721
 
7722
The @code{movf} functions are similar but use @code{movf.ps} instead
7723
of @code{movt.ps}.
7724
 
7725
@item int __builtin_mips_any_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7726
@itemx int __builtin_mips_all_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7727
@itemx int __builtin_mips_any_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7728
@itemx int __builtin_mips_all_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
7729
Comparison of two paired-single values
7730
(@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps},
7731
@code{bc1any2t}/@code{bc1any2f}).
7732
 
7733
These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps}
7734
or @code{cabs.@var{cond}.ps}.  The @code{any} forms return true if either
7735
result is true and the @code{all} forms return true if both results are true.
7736
For example:
7737
 
7738
@smallexample
7739
v2sf a, b;
7740
if (__builtin_mips_any_c_eq_ps (a, b))
7741
  one_is_true ();
7742
else
7743
  both_are_false ();
7744
 
7745
if (__builtin_mips_all_c_eq_ps (a, b))
7746
  both_are_true ();
7747
else
7748
  one_is_false ();
7749
@end smallexample
7750
 
7751
@item int __builtin_mips_any_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7752
@itemx int __builtin_mips_all_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7753
@itemx int __builtin_mips_any_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7754
@itemx int __builtin_mips_all_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
7755
Comparison of four paired-single values
7756
(@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps},
7757
@code{bc1any4t}/@code{bc1any4f}).
7758
 
7759
These functions use @code{c.@var{cond}.ps} or @code{cabs.@var{cond}.ps}
7760
to compare @var{a} with @var{b} and to compare @var{c} with @var{d}.
7761
The @code{any} forms return true if any of the four results are true
7762
and the @code{all} forms return true if all four results are true.
7763
For example:
7764
 
7765
@smallexample
7766
v2sf a, b, c, d;
7767
if (__builtin_mips_any_c_eq_4s (a, b, c, d))
7768
  some_are_true ();
7769
else
7770
  all_are_false ();
7771
 
7772
if (__builtin_mips_all_c_eq_4s (a, b, c, d))
7773
  all_are_true ();
7774
else
7775
  some_are_false ();
7776
@end smallexample
7777
@end table
7778
 
7779
@node PowerPC AltiVec Built-in Functions
7780
@subsection PowerPC AltiVec Built-in Functions
7781
 
7782
GCC provides an interface for the PowerPC family of processors to access
7783
the AltiVec operations described in Motorola's AltiVec Programming
7784
Interface Manual.  The interface is made available by including
7785
@code{<altivec.h>} and using @option{-maltivec} and
7786
@option{-mabi=altivec}.  The interface supports the following vector
7787
types.
7788
 
7789
@smallexample
7790
vector unsigned char
7791
vector signed char
7792
vector bool char
7793
 
7794
vector unsigned short
7795
vector signed short
7796
vector bool short
7797
vector pixel
7798
 
7799
vector unsigned int
7800
vector signed int
7801
vector bool int
7802
vector float
7803
@end smallexample
7804
 
7805
GCC's implementation of the high-level language interface available from
7806
C and C++ code differs from Motorola's documentation in several ways.
7807
 
7808
@itemize @bullet
7809
 
7810
@item
7811
A vector constant is a list of constant expressions within curly braces.
7812
 
7813
@item
7814
A vector initializer requires no cast if the vector constant is of the
7815
same type as the variable it is initializing.
7816
 
7817
@item
7818
If @code{signed} or @code{unsigned} is omitted, the signedness of the
7819
vector type is the default signedness of the base type.  The default
7820
varies depending on the operating system, so a portable program should
7821
always specify the signedness.
7822
 
7823
@item
7824
Compiling with @option{-maltivec} adds keywords @code{__vector},
7825
@code{__pixel}, and @code{__bool}.  Macros @option{vector},
7826
@code{pixel}, and @code{bool} are defined in @code{<altivec.h>} and can
7827
be undefined.
7828
 
7829
@item
7830
GCC allows using a @code{typedef} name as the type specifier for a
7831
vector type.
7832
 
7833
@item
7834
For C, overloaded functions are implemented with macros so the following
7835
does not work:
7836
 
7837
@smallexample
7838
  vec_add ((vector signed int)@{1, 2, 3, 4@}, foo);
7839
@end smallexample
7840
 
7841
Since @code{vec_add} is a macro, the vector constant in the example
7842
is treated as four separate arguments.  Wrap the entire argument in
7843
parentheses for this to work.
7844
@end itemize
7845
 
7846
@emph{Note:} Only the @code{<altivec.h>} interface is supported.
7847
Internally, GCC uses built-in functions to achieve the functionality in
7848
the aforementioned header file, but they are not supported and are
7849
subject to change without notice.
7850
 
7851
The following interfaces are supported for the generic and specific
7852
AltiVec operations and the AltiVec predicates.  In cases where there
7853
is a direct mapping between generic and specific operations, only the
7854
generic names are shown here, although the specific operations can also
7855
be used.
7856
 
7857
Arguments that are documented as @code{const int} require literal
7858
integral values within the range required for that operation.
7859
 
7860
@smallexample
7861
vector signed char vec_abs (vector signed char);
7862
vector signed short vec_abs (vector signed short);
7863
vector signed int vec_abs (vector signed int);
7864
vector float vec_abs (vector float);
7865
 
7866
vector signed char vec_abss (vector signed char);
7867
vector signed short vec_abss (vector signed short);
7868
vector signed int vec_abss (vector signed int);
7869
 
7870
vector signed char vec_add (vector bool char, vector signed char);
7871
vector signed char vec_add (vector signed char, vector bool char);
7872
vector signed char vec_add (vector signed char, vector signed char);
7873
vector unsigned char vec_add (vector bool char, vector unsigned char);
7874
vector unsigned char vec_add (vector unsigned char, vector bool char);
7875
vector unsigned char vec_add (vector unsigned char,
7876
                              vector unsigned char);
7877
vector signed short vec_add (vector bool short, vector signed short);
7878
vector signed short vec_add (vector signed short, vector bool short);
7879
vector signed short vec_add (vector signed short, vector signed short);
7880
vector unsigned short vec_add (vector bool short,
7881
                               vector unsigned short);
7882
vector unsigned short vec_add (vector unsigned short,
7883
                               vector bool short);
7884
vector unsigned short vec_add (vector unsigned short,
7885
                               vector unsigned short);
7886
vector signed int vec_add (vector bool int, vector signed int);
7887
vector signed int vec_add (vector signed int, vector bool int);
7888
vector signed int vec_add (vector signed int, vector signed int);
7889
vector unsigned int vec_add (vector bool int, vector unsigned int);
7890
vector unsigned int vec_add (vector unsigned int, vector bool int);
7891
vector unsigned int vec_add (vector unsigned int, vector unsigned int);
7892
vector float vec_add (vector float, vector float);
7893
 
7894
vector float vec_vaddfp (vector float, vector float);
7895
 
7896
vector signed int vec_vadduwm (vector bool int, vector signed int);
7897
vector signed int vec_vadduwm (vector signed int, vector bool int);
7898
vector signed int vec_vadduwm (vector signed int, vector signed int);
7899
vector unsigned int vec_vadduwm (vector bool int, vector unsigned int);
7900
vector unsigned int vec_vadduwm (vector unsigned int, vector bool int);
7901
vector unsigned int vec_vadduwm (vector unsigned int,
7902
                                 vector unsigned int);
7903
 
7904
vector signed short vec_vadduhm (vector bool short,
7905
                                 vector signed short);
7906
vector signed short vec_vadduhm (vector signed short,
7907
                                 vector bool short);
7908
vector signed short vec_vadduhm (vector signed short,
7909
                                 vector signed short);
7910
vector unsigned short vec_vadduhm (vector bool short,
7911
                                   vector unsigned short);
7912
vector unsigned short vec_vadduhm (vector unsigned short,
7913
                                   vector bool short);
7914
vector unsigned short vec_vadduhm (vector unsigned short,
7915
                                   vector unsigned short);
7916
 
7917
vector signed char vec_vaddubm (vector bool char, vector signed char);
7918
vector signed char vec_vaddubm (vector signed char, vector bool char);
7919
vector signed char vec_vaddubm (vector signed char, vector signed char);
7920
vector unsigned char vec_vaddubm (vector bool char,
7921
                                  vector unsigned char);
7922
vector unsigned char vec_vaddubm (vector unsigned char,
7923
                                  vector bool char);
7924
vector unsigned char vec_vaddubm (vector unsigned char,
7925
                                  vector unsigned char);
7926
 
7927
vector unsigned int vec_addc (vector unsigned int, vector unsigned int);
7928
 
7929
vector unsigned char vec_adds (vector bool char, vector unsigned char);
7930
vector unsigned char vec_adds (vector unsigned char, vector bool char);
7931
vector unsigned char vec_adds (vector unsigned char,
7932
                               vector unsigned char);
7933
vector signed char vec_adds (vector bool char, vector signed char);
7934
vector signed char vec_adds (vector signed char, vector bool char);
7935
vector signed char vec_adds (vector signed char, vector signed char);
7936
vector unsigned short vec_adds (vector bool short,
7937
                                vector unsigned short);
7938
vector unsigned short vec_adds (vector unsigned short,
7939
                                vector bool short);
7940
vector unsigned short vec_adds (vector unsigned short,
7941
                                vector unsigned short);
7942
vector signed short vec_adds (vector bool short, vector signed short);
7943
vector signed short vec_adds (vector signed short, vector bool short);
7944
vector signed short vec_adds (vector signed short, vector signed short);
7945
vector unsigned int vec_adds (vector bool int, vector unsigned int);
7946
vector unsigned int vec_adds (vector unsigned int, vector bool int);
7947
vector unsigned int vec_adds (vector unsigned int, vector unsigned int);
7948
vector signed int vec_adds (vector bool int, vector signed int);
7949
vector signed int vec_adds (vector signed int, vector bool int);
7950
vector signed int vec_adds (vector signed int, vector signed int);
7951
 
7952
vector signed int vec_vaddsws (vector bool int, vector signed int);
7953
vector signed int vec_vaddsws (vector signed int, vector bool int);
7954
vector signed int vec_vaddsws (vector signed int, vector signed int);
7955
 
7956
vector unsigned int vec_vadduws (vector bool int, vector unsigned int);
7957
vector unsigned int vec_vadduws (vector unsigned int, vector bool int);
7958
vector unsigned int vec_vadduws (vector unsigned int,
7959
                                 vector unsigned int);
7960
 
7961
vector signed short vec_vaddshs (vector bool short,
7962
                                 vector signed short);
7963
vector signed short vec_vaddshs (vector signed short,
7964
                                 vector bool short);
7965
vector signed short vec_vaddshs (vector signed short,
7966
                                 vector signed short);
7967
 
7968
vector unsigned short vec_vadduhs (vector bool short,
7969
                                   vector unsigned short);
7970
vector unsigned short vec_vadduhs (vector unsigned short,
7971
                                   vector bool short);
7972
vector unsigned short vec_vadduhs (vector unsigned short,
7973
                                   vector unsigned short);
7974
 
7975
vector signed char vec_vaddsbs (vector bool char, vector signed char);
7976
vector signed char vec_vaddsbs (vector signed char, vector bool char);
7977
vector signed char vec_vaddsbs (vector signed char, vector signed char);
7978
 
7979
vector unsigned char vec_vaddubs (vector bool char,
7980
                                  vector unsigned char);
7981
vector unsigned char vec_vaddubs (vector unsigned char,
7982
                                  vector bool char);
7983
vector unsigned char vec_vaddubs (vector unsigned char,
7984
                                  vector unsigned char);
7985
 
7986
vector float vec_and (vector float, vector float);
7987
vector float vec_and (vector float, vector bool int);
7988
vector float vec_and (vector bool int, vector float);
7989
vector bool int vec_and (vector bool int, vector bool int);
7990
vector signed int vec_and (vector bool int, vector signed int);
7991
vector signed int vec_and (vector signed int, vector bool int);
7992
vector signed int vec_and (vector signed int, vector signed int);
7993
vector unsigned int vec_and (vector bool int, vector unsigned int);
7994
vector unsigned int vec_and (vector unsigned int, vector bool int);
7995
vector unsigned int vec_and (vector unsigned int, vector unsigned int);
7996
vector bool short vec_and (vector bool short, vector bool short);
7997
vector signed short vec_and (vector bool short, vector signed short);
7998
vector signed short vec_and (vector signed short, vector bool short);
7999
vector signed short vec_and (vector signed short, vector signed short);
8000
vector unsigned short vec_and (vector bool short,
8001
                               vector unsigned short);
8002
vector unsigned short vec_and (vector unsigned short,
8003
                               vector bool short);
8004
vector unsigned short vec_and (vector unsigned short,
8005
                               vector unsigned short);
8006
vector signed char vec_and (vector bool char, vector signed char);
8007
vector bool char vec_and (vector bool char, vector bool char);
8008
vector signed char vec_and (vector signed char, vector bool char);
8009
vector signed char vec_and (vector signed char, vector signed char);
8010
vector unsigned char vec_and (vector bool char, vector unsigned char);
8011
vector unsigned char vec_and (vector unsigned char, vector bool char);
8012
vector unsigned char vec_and (vector unsigned char,
8013
                              vector unsigned char);
8014
 
8015
vector float vec_andc (vector float, vector float);
8016
vector float vec_andc (vector float, vector bool int);
8017
vector float vec_andc (vector bool int, vector float);
8018
vector bool int vec_andc (vector bool int, vector bool int);
8019
vector signed int vec_andc (vector bool int, vector signed int);
8020
vector signed int vec_andc (vector signed int, vector bool int);
8021
vector signed int vec_andc (vector signed int, vector signed int);
8022
vector unsigned int vec_andc (vector bool int, vector unsigned int);
8023
vector unsigned int vec_andc (vector unsigned int, vector bool int);
8024
vector unsigned int vec_andc (vector unsigned int, vector unsigned int);
8025
vector bool short vec_andc (vector bool short, vector bool short);
8026
vector signed short vec_andc (vector bool short, vector signed short);
8027
vector signed short vec_andc (vector signed short, vector bool short);
8028
vector signed short vec_andc (vector signed short, vector signed short);
8029
vector unsigned short vec_andc (vector bool short,
8030
                                vector unsigned short);
8031
vector unsigned short vec_andc (vector unsigned short,
8032
                                vector bool short);
8033
vector unsigned short vec_andc (vector unsigned short,
8034
                                vector unsigned short);
8035
vector signed char vec_andc (vector bool char, vector signed char);
8036
vector bool char vec_andc (vector bool char, vector bool char);
8037
vector signed char vec_andc (vector signed char, vector bool char);
8038
vector signed char vec_andc (vector signed char, vector signed char);
8039
vector unsigned char vec_andc (vector bool char, vector unsigned char);
8040
vector unsigned char vec_andc (vector unsigned char, vector bool char);
8041
vector unsigned char vec_andc (vector unsigned char,
8042
                               vector unsigned char);
8043
 
8044
vector unsigned char vec_avg (vector unsigned char,
8045
                              vector unsigned char);
8046
vector signed char vec_avg (vector signed char, vector signed char);
8047
vector unsigned short vec_avg (vector unsigned short,
8048
                               vector unsigned short);
8049
vector signed short vec_avg (vector signed short, vector signed short);
8050
vector unsigned int vec_avg (vector unsigned int, vector unsigned int);
8051
vector signed int vec_avg (vector signed int, vector signed int);
8052
 
8053
vector signed int vec_vavgsw (vector signed int, vector signed int);
8054
 
8055
vector unsigned int vec_vavguw (vector unsigned int,
8056
                                vector unsigned int);
8057
 
8058
vector signed short vec_vavgsh (vector signed short,
8059
                                vector signed short);
8060
 
8061
vector unsigned short vec_vavguh (vector unsigned short,
8062
                                  vector unsigned short);
8063
 
8064
vector signed char vec_vavgsb (vector signed char, vector signed char);
8065
 
8066
vector unsigned char vec_vavgub (vector unsigned char,
8067
                                 vector unsigned char);
8068
 
8069
vector float vec_ceil (vector float);
8070
 
8071
vector signed int vec_cmpb (vector float, vector float);
8072
 
8073
vector bool char vec_cmpeq (vector signed char, vector signed char);
8074
vector bool char vec_cmpeq (vector unsigned char, vector unsigned char);
8075
vector bool short vec_cmpeq (vector signed short, vector signed short);
8076
vector bool short vec_cmpeq (vector unsigned short,
8077
                             vector unsigned short);
8078
vector bool int vec_cmpeq (vector signed int, vector signed int);
8079
vector bool int vec_cmpeq (vector unsigned int, vector unsigned int);
8080
vector bool int vec_cmpeq (vector float, vector float);
8081
 
8082
vector bool int vec_vcmpeqfp (vector float, vector float);
8083
 
8084
vector bool int vec_vcmpequw (vector signed int, vector signed int);
8085
vector bool int vec_vcmpequw (vector unsigned int, vector unsigned int);
8086
 
8087
vector bool short vec_vcmpequh (vector signed short,
8088
                                vector signed short);
8089
vector bool short vec_vcmpequh (vector unsigned short,
8090
                                vector unsigned short);
8091
 
8092
vector bool char vec_vcmpequb (vector signed char, vector signed char);
8093
vector bool char vec_vcmpequb (vector unsigned char,
8094
                               vector unsigned char);
8095
 
8096
vector bool int vec_cmpge (vector float, vector float);
8097
 
8098
vector bool char vec_cmpgt (vector unsigned char, vector unsigned char);
8099
vector bool char vec_cmpgt (vector signed char, vector signed char);
8100
vector bool short vec_cmpgt (vector unsigned short,
8101
                             vector unsigned short);
8102
vector bool short vec_cmpgt (vector signed short, vector signed short);
8103
vector bool int vec_cmpgt (vector unsigned int, vector unsigned int);
8104
vector bool int vec_cmpgt (vector signed int, vector signed int);
8105
vector bool int vec_cmpgt (vector float, vector float);
8106
 
8107
vector bool int vec_vcmpgtfp (vector float, vector float);
8108
 
8109
vector bool int vec_vcmpgtsw (vector signed int, vector signed int);
8110
 
8111
vector bool int vec_vcmpgtuw (vector unsigned int, vector unsigned int);
8112
 
8113
vector bool short vec_vcmpgtsh (vector signed short,
8114
                                vector signed short);
8115
 
8116
vector bool short vec_vcmpgtuh (vector unsigned short,
8117
                                vector unsigned short);
8118
 
8119
vector bool char vec_vcmpgtsb (vector signed char, vector signed char);
8120
 
8121
vector bool char vec_vcmpgtub (vector unsigned char,
8122
                               vector unsigned char);
8123
 
8124
vector bool int vec_cmple (vector float, vector float);
8125
 
8126
vector bool char vec_cmplt (vector unsigned char, vector unsigned char);
8127
vector bool char vec_cmplt (vector signed char, vector signed char);
8128
vector bool short vec_cmplt (vector unsigned short,
8129
                             vector unsigned short);
8130
vector bool short vec_cmplt (vector signed short, vector signed short);
8131
vector bool int vec_cmplt (vector unsigned int, vector unsigned int);
8132
vector bool int vec_cmplt (vector signed int, vector signed int);
8133
vector bool int vec_cmplt (vector float, vector float);
8134
 
8135
vector float vec_ctf (vector unsigned int, const int);
8136
vector float vec_ctf (vector signed int, const int);
8137
 
8138
vector float vec_vcfsx (vector signed int, const int);
8139
 
8140
vector float vec_vcfux (vector unsigned int, const int);
8141
 
8142
vector signed int vec_cts (vector float, const int);
8143
 
8144
vector unsigned int vec_ctu (vector float, const int);
8145
 
8146
void vec_dss (const int);
8147
 
8148
void vec_dssall (void);
8149
 
8150
void vec_dst (const vector unsigned char *, int, const int);
8151
void vec_dst (const vector signed char *, int, const int);
8152
void vec_dst (const vector bool char *, int, const int);
8153
void vec_dst (const vector unsigned short *, int, const int);
8154
void vec_dst (const vector signed short *, int, const int);
8155
void vec_dst (const vector bool short *, int, const int);
8156
void vec_dst (const vector pixel *, int, const int);
8157
void vec_dst (const vector unsigned int *, int, const int);
8158
void vec_dst (const vector signed int *, int, const int);
8159
void vec_dst (const vector bool int *, int, const int);
8160
void vec_dst (const vector float *, int, const int);
8161
void vec_dst (const unsigned char *, int, const int);
8162
void vec_dst (const signed char *, int, const int);
8163
void vec_dst (const unsigned short *, int, const int);
8164
void vec_dst (const short *, int, const int);
8165
void vec_dst (const unsigned int *, int, const int);
8166
void vec_dst (const int *, int, const int);
8167
void vec_dst (const unsigned long *, int, const int);
8168
void vec_dst (const long *, int, const int);
8169
void vec_dst (const float *, int, const int);
8170
 
8171
void vec_dstst (const vector unsigned char *, int, const int);
8172
void vec_dstst (const vector signed char *, int, const int);
8173
void vec_dstst (const vector bool char *, int, const int);
8174
void vec_dstst (const vector unsigned short *, int, const int);
8175
void vec_dstst (const vector signed short *, int, const int);
8176
void vec_dstst (const vector bool short *, int, const int);
8177
void vec_dstst (const vector pixel *, int, const int);
8178
void vec_dstst (const vector unsigned int *, int, const int);
8179
void vec_dstst (const vector signed int *, int, const int);
8180
void vec_dstst (const vector bool int *, int, const int);
8181
void vec_dstst (const vector float *, int, const int);
8182
void vec_dstst (const unsigned char *, int, const int);
8183
void vec_dstst (const signed char *, int, const int);
8184
void vec_dstst (const unsigned short *, int, const int);
8185
void vec_dstst (const short *, int, const int);
8186
void vec_dstst (const unsigned int *, int, const int);
8187
void vec_dstst (const int *, int, const int);
8188
void vec_dstst (const unsigned long *, int, const int);
8189
void vec_dstst (const long *, int, const int);
8190
void vec_dstst (const float *, int, const int);
8191
 
8192
void vec_dststt (const vector unsigned char *, int, const int);
8193
void vec_dststt (const vector signed char *, int, const int);
8194
void vec_dststt (const vector bool char *, int, const int);
8195
void vec_dststt (const vector unsigned short *, int, const int);
8196
void vec_dststt (const vector signed short *, int, const int);
8197
void vec_dststt (const vector bool short *, int, const int);
8198
void vec_dststt (const vector pixel *, int, const int);
8199
void vec_dststt (const vector unsigned int *, int, const int);
8200
void vec_dststt (const vector signed int *, int, const int);
8201
void vec_dststt (const vector bool int *, int, const int);
8202
void vec_dststt (const vector float *, int, const int);
8203
void vec_dststt (const unsigned char *, int, const int);
8204
void vec_dststt (const signed char *, int, const int);
8205
void vec_dststt (const unsigned short *, int, const int);
8206
void vec_dststt (const short *, int, const int);
8207
void vec_dststt (const unsigned int *, int, const int);
8208
void vec_dststt (const int *, int, const int);
8209
void vec_dststt (const unsigned long *, int, const int);
8210
void vec_dststt (const long *, int, const int);
8211
void vec_dststt (const float *, int, const int);
8212
 
8213
void vec_dstt (const vector unsigned char *, int, const int);
8214
void vec_dstt (const vector signed char *, int, const int);
8215
void vec_dstt (const vector bool char *, int, const int);
8216
void vec_dstt (const vector unsigned short *, int, const int);
8217
void vec_dstt (const vector signed short *, int, const int);
8218
void vec_dstt (const vector bool short *, int, const int);
8219
void vec_dstt (const vector pixel *, int, const int);
8220
void vec_dstt (const vector unsigned int *, int, const int);
8221
void vec_dstt (const vector signed int *, int, const int);
8222
void vec_dstt (const vector bool int *, int, const int);
8223
void vec_dstt (const vector float *, int, const int);
8224
void vec_dstt (const unsigned char *, int, const int);
8225
void vec_dstt (const signed char *, int, const int);
8226
void vec_dstt (const unsigned short *, int, const int);
8227
void vec_dstt (const short *, int, const int);
8228
void vec_dstt (const unsigned int *, int, const int);
8229
void vec_dstt (const int *, int, const int);
8230
void vec_dstt (const unsigned long *, int, const int);
8231
void vec_dstt (const long *, int, const int);
8232
void vec_dstt (const float *, int, const int);
8233
 
8234
vector float vec_expte (vector float);
8235
 
8236
vector float vec_floor (vector float);
8237
 
8238
vector float vec_ld (int, const vector float *);
8239
vector float vec_ld (int, const float *);
8240
vector bool int vec_ld (int, const vector bool int *);
8241
vector signed int vec_ld (int, const vector signed int *);
8242
vector signed int vec_ld (int, const int *);
8243
vector signed int vec_ld (int, const long *);
8244
vector unsigned int vec_ld (int, const vector unsigned int *);
8245
vector unsigned int vec_ld (int, const unsigned int *);
8246
vector unsigned int vec_ld (int, const unsigned long *);
8247
vector bool short vec_ld (int, const vector bool short *);
8248
vector pixel vec_ld (int, const vector pixel *);
8249
vector signed short vec_ld (int, const vector signed short *);
8250
vector signed short vec_ld (int, const short *);
8251
vector unsigned short vec_ld (int, const vector unsigned short *);
8252
vector unsigned short vec_ld (int, const unsigned short *);
8253
vector bool char vec_ld (int, const vector bool char *);
8254
vector signed char vec_ld (int, const vector signed char *);
8255
vector signed char vec_ld (int, const signed char *);
8256
vector unsigned char vec_ld (int, const vector unsigned char *);
8257
vector unsigned char vec_ld (int, const unsigned char *);
8258
 
8259
vector signed char vec_lde (int, const signed char *);
8260
vector unsigned char vec_lde (int, const unsigned char *);
8261
vector signed short vec_lde (int, const short *);
8262
vector unsigned short vec_lde (int, const unsigned short *);
8263
vector float vec_lde (int, const float *);
8264
vector signed int vec_lde (int, const int *);
8265
vector unsigned int vec_lde (int, const unsigned int *);
8266
vector signed int vec_lde (int, const long *);
8267
vector unsigned int vec_lde (int, const unsigned long *);
8268
 
8269
vector float vec_lvewx (int, float *);
8270
vector signed int vec_lvewx (int, int *);
8271
vector unsigned int vec_lvewx (int, unsigned int *);
8272
vector signed int vec_lvewx (int, long *);
8273
vector unsigned int vec_lvewx (int, unsigned long *);
8274
 
8275
vector signed short vec_lvehx (int, short *);
8276
vector unsigned short vec_lvehx (int, unsigned short *);
8277
 
8278
vector signed char vec_lvebx (int, char *);
8279
vector unsigned char vec_lvebx (int, unsigned char *);
8280
 
8281
vector float vec_ldl (int, const vector float *);
8282
vector float vec_ldl (int, const float *);
8283
vector bool int vec_ldl (int, const vector bool int *);
8284
vector signed int vec_ldl (int, const vector signed int *);
8285
vector signed int vec_ldl (int, const int *);
8286
vector signed int vec_ldl (int, const long *);
8287
vector unsigned int vec_ldl (int, const vector unsigned int *);
8288
vector unsigned int vec_ldl (int, const unsigned int *);
8289
vector unsigned int vec_ldl (int, const unsigned long *);
8290
vector bool short vec_ldl (int, const vector bool short *);
8291
vector pixel vec_ldl (int, const vector pixel *);
8292
vector signed short vec_ldl (int, const vector signed short *);
8293
vector signed short vec_ldl (int, const short *);
8294
vector unsigned short vec_ldl (int, const vector unsigned short *);
8295
vector unsigned short vec_ldl (int, const unsigned short *);
8296
vector bool char vec_ldl (int, const vector bool char *);
8297
vector signed char vec_ldl (int, const vector signed char *);
8298
vector signed char vec_ldl (int, const signed char *);
8299
vector unsigned char vec_ldl (int, const vector unsigned char *);
8300
vector unsigned char vec_ldl (int, const unsigned char *);
8301
 
8302
vector float vec_loge (vector float);
8303
 
8304
vector unsigned char vec_lvsl (int, const volatile unsigned char *);
8305
vector unsigned char vec_lvsl (int, const volatile signed char *);
8306
vector unsigned char vec_lvsl (int, const volatile unsigned short *);
8307
vector unsigned char vec_lvsl (int, const volatile short *);
8308
vector unsigned char vec_lvsl (int, const volatile unsigned int *);
8309
vector unsigned char vec_lvsl (int, const volatile int *);
8310
vector unsigned char vec_lvsl (int, const volatile unsigned long *);
8311
vector unsigned char vec_lvsl (int, const volatile long *);
8312
vector unsigned char vec_lvsl (int, const volatile float *);
8313
 
8314
vector unsigned char vec_lvsr (int, const volatile unsigned char *);
8315
vector unsigned char vec_lvsr (int, const volatile signed char *);
8316
vector unsigned char vec_lvsr (int, const volatile unsigned short *);
8317
vector unsigned char vec_lvsr (int, const volatile short *);
8318
vector unsigned char vec_lvsr (int, const volatile unsigned int *);
8319
vector unsigned char vec_lvsr (int, const volatile int *);
8320
vector unsigned char vec_lvsr (int, const volatile unsigned long *);
8321
vector unsigned char vec_lvsr (int, const volatile long *);
8322
vector unsigned char vec_lvsr (int, const volatile float *);
8323
 
8324
vector float vec_madd (vector float, vector float, vector float);
8325
 
8326
vector signed short vec_madds (vector signed short,
8327
                               vector signed short,
8328
                               vector signed short);
8329
 
8330
vector unsigned char vec_max (vector bool char, vector unsigned char);
8331
vector unsigned char vec_max (vector unsigned char, vector bool char);
8332
vector unsigned char vec_max (vector unsigned char,
8333
                              vector unsigned char);
8334
vector signed char vec_max (vector bool char, vector signed char);
8335
vector signed char vec_max (vector signed char, vector bool char);
8336
vector signed char vec_max (vector signed char, vector signed char);
8337
vector unsigned short vec_max (vector bool short,
8338
                               vector unsigned short);
8339
vector unsigned short vec_max (vector unsigned short,
8340
                               vector bool short);
8341
vector unsigned short vec_max (vector unsigned short,
8342
                               vector unsigned short);
8343
vector signed short vec_max (vector bool short, vector signed short);
8344
vector signed short vec_max (vector signed short, vector bool short);
8345
vector signed short vec_max (vector signed short, vector signed short);
8346
vector unsigned int vec_max (vector bool int, vector unsigned int);
8347
vector unsigned int vec_max (vector unsigned int, vector bool int);
8348
vector unsigned int vec_max (vector unsigned int, vector unsigned int);
8349
vector signed int vec_max (vector bool int, vector signed int);
8350
vector signed int vec_max (vector signed int, vector bool int);
8351
vector signed int vec_max (vector signed int, vector signed int);
8352
vector float vec_max (vector float, vector float);
8353
 
8354
vector float vec_vmaxfp (vector float, vector float);
8355
 
8356
vector signed int vec_vmaxsw (vector bool int, vector signed int);
8357
vector signed int vec_vmaxsw (vector signed int, vector bool int);
8358
vector signed int vec_vmaxsw (vector signed int, vector signed int);
8359
 
8360
vector unsigned int vec_vmaxuw (vector bool int, vector unsigned int);
8361
vector unsigned int vec_vmaxuw (vector unsigned int, vector bool int);
8362
vector unsigned int vec_vmaxuw (vector unsigned int,
8363
                                vector unsigned int);
8364
 
8365
vector signed short vec_vmaxsh (vector bool short, vector signed short);
8366
vector signed short vec_vmaxsh (vector signed short, vector bool short);
8367
vector signed short vec_vmaxsh (vector signed short,
8368
                                vector signed short);
8369
 
8370
vector unsigned short vec_vmaxuh (vector bool short,
8371
                                  vector unsigned short);
8372
vector unsigned short vec_vmaxuh (vector unsigned short,
8373
                                  vector bool short);
8374
vector unsigned short vec_vmaxuh (vector unsigned short,
8375
                                  vector unsigned short);
8376
 
8377
vector signed char vec_vmaxsb (vector bool char, vector signed char);
8378
vector signed char vec_vmaxsb (vector signed char, vector bool char);
8379
vector signed char vec_vmaxsb (vector signed char, vector signed char);
8380
 
8381
vector unsigned char vec_vmaxub (vector bool char,
8382
                                 vector unsigned char);
8383
vector unsigned char vec_vmaxub (vector unsigned char,
8384
                                 vector bool char);
8385
vector unsigned char vec_vmaxub (vector unsigned char,
8386
                                 vector unsigned char);
8387
 
8388
vector bool char vec_mergeh (vector bool char, vector bool char);
8389
vector signed char vec_mergeh (vector signed char, vector signed char);
8390
vector unsigned char vec_mergeh (vector unsigned char,
8391
                                 vector unsigned char);
8392
vector bool short vec_mergeh (vector bool short, vector bool short);
8393
vector pixel vec_mergeh (vector pixel, vector pixel);
8394
vector signed short vec_mergeh (vector signed short,
8395
                                vector signed short);
8396
vector unsigned short vec_mergeh (vector unsigned short,
8397
                                  vector unsigned short);
8398
vector float vec_mergeh (vector float, vector float);
8399
vector bool int vec_mergeh (vector bool int, vector bool int);
8400
vector signed int vec_mergeh (vector signed int, vector signed int);
8401
vector unsigned int vec_mergeh (vector unsigned int,
8402
                                vector unsigned int);
8403
 
8404
vector float vec_vmrghw (vector float, vector float);
8405
vector bool int vec_vmrghw (vector bool int, vector bool int);
8406
vector signed int vec_vmrghw (vector signed int, vector signed int);
8407
vector unsigned int vec_vmrghw (vector unsigned int,
8408
                                vector unsigned int);
8409
 
8410
vector bool short vec_vmrghh (vector bool short, vector bool short);
8411
vector signed short vec_vmrghh (vector signed short,
8412
                                vector signed short);
8413
vector unsigned short vec_vmrghh (vector unsigned short,
8414
                                  vector unsigned short);
8415
vector pixel vec_vmrghh (vector pixel, vector pixel);
8416
 
8417
vector bool char vec_vmrghb (vector bool char, vector bool char);
8418
vector signed char vec_vmrghb (vector signed char, vector signed char);
8419
vector unsigned char vec_vmrghb (vector unsigned char,
8420
                                 vector unsigned char);
8421
 
8422
vector bool char vec_mergel (vector bool char, vector bool char);
8423
vector signed char vec_mergel (vector signed char, vector signed char);
8424
vector unsigned char vec_mergel (vector unsigned char,
8425
                                 vector unsigned char);
8426
vector bool short vec_mergel (vector bool short, vector bool short);
8427
vector pixel vec_mergel (vector pixel, vector pixel);
8428
vector signed short vec_mergel (vector signed short,
8429
                                vector signed short);
8430
vector unsigned short vec_mergel (vector unsigned short,
8431
                                  vector unsigned short);
8432
vector float vec_mergel (vector float, vector float);
8433
vector bool int vec_mergel (vector bool int, vector bool int);
8434
vector signed int vec_mergel (vector signed int, vector signed int);
8435
vector unsigned int vec_mergel (vector unsigned int,
8436
                                vector unsigned int);
8437
 
8438
vector float vec_vmrglw (vector float, vector float);
8439
vector signed int vec_vmrglw (vector signed int, vector signed int);
8440
vector unsigned int vec_vmrglw (vector unsigned int,
8441
                                vector unsigned int);
8442
vector bool int vec_vmrglw (vector bool int, vector bool int);
8443
 
8444
vector bool short vec_vmrglh (vector bool short, vector bool short);
8445
vector signed short vec_vmrglh (vector signed short,
8446
                                vector signed short);
8447
vector unsigned short vec_vmrglh (vector unsigned short,
8448
                                  vector unsigned short);
8449
vector pixel vec_vmrglh (vector pixel, vector pixel);
8450
 
8451
vector bool char vec_vmrglb (vector bool char, vector bool char);
8452
vector signed char vec_vmrglb (vector signed char, vector signed char);
8453
vector unsigned char vec_vmrglb (vector unsigned char,
8454
                                 vector unsigned char);
8455
 
8456
vector unsigned short vec_mfvscr (void);
8457
 
8458
vector unsigned char vec_min (vector bool char, vector unsigned char);
8459
vector unsigned char vec_min (vector unsigned char, vector bool char);
8460
vector unsigned char vec_min (vector unsigned char,
8461
                              vector unsigned char);
8462
vector signed char vec_min (vector bool char, vector signed char);
8463
vector signed char vec_min (vector signed char, vector bool char);
8464
vector signed char vec_min (vector signed char, vector signed char);
8465
vector unsigned short vec_min (vector bool short,
8466
                               vector unsigned short);
8467
vector unsigned short vec_min (vector unsigned short,
8468
                               vector bool short);
8469
vector unsigned short vec_min (vector unsigned short,
8470
                               vector unsigned short);
8471
vector signed short vec_min (vector bool short, vector signed short);
8472
vector signed short vec_min (vector signed short, vector bool short);
8473
vector signed short vec_min (vector signed short, vector signed short);
8474
vector unsigned int vec_min (vector bool int, vector unsigned int);
8475
vector unsigned int vec_min (vector unsigned int, vector bool int);
8476
vector unsigned int vec_min (vector unsigned int, vector unsigned int);
8477
vector signed int vec_min (vector bool int, vector signed int);
8478
vector signed int vec_min (vector signed int, vector bool int);
8479
vector signed int vec_min (vector signed int, vector signed int);
8480
vector float vec_min (vector float, vector float);
8481
 
8482
vector float vec_vminfp (vector float, vector float);
8483
 
8484
vector signed int vec_vminsw (vector bool int, vector signed int);
8485
vector signed int vec_vminsw (vector signed int, vector bool int);
8486
vector signed int vec_vminsw (vector signed int, vector signed int);
8487
 
8488
vector unsigned int vec_vminuw (vector bool int, vector unsigned int);
8489
vector unsigned int vec_vminuw (vector unsigned int, vector bool int);
8490
vector unsigned int vec_vminuw (vector unsigned int,
8491
                                vector unsigned int);
8492
 
8493
vector signed short vec_vminsh (vector bool short, vector signed short);
8494
vector signed short vec_vminsh (vector signed short, vector bool short);
8495
vector signed short vec_vminsh (vector signed short,
8496
                                vector signed short);
8497
 
8498
vector unsigned short vec_vminuh (vector bool short,
8499
                                  vector unsigned short);
8500
vector unsigned short vec_vminuh (vector unsigned short,
8501
                                  vector bool short);
8502
vector unsigned short vec_vminuh (vector unsigned short,
8503
                                  vector unsigned short);
8504
 
8505
vector signed char vec_vminsb (vector bool char, vector signed char);
8506
vector signed char vec_vminsb (vector signed char, vector bool char);
8507
vector signed char vec_vminsb (vector signed char, vector signed char);
8508
 
8509
vector unsigned char vec_vminub (vector bool char,
8510
                                 vector unsigned char);
8511
vector unsigned char vec_vminub (vector unsigned char,
8512
                                 vector bool char);
8513
vector unsigned char vec_vminub (vector unsigned char,
8514
                                 vector unsigned char);
8515
 
8516
vector signed short vec_mladd (vector signed short,
8517
                               vector signed short,
8518
                               vector signed short);
8519
vector signed short vec_mladd (vector signed short,
8520
                               vector unsigned short,
8521
                               vector unsigned short);
8522
vector signed short vec_mladd (vector unsigned short,
8523
                               vector signed short,
8524
                               vector signed short);
8525
vector unsigned short vec_mladd (vector unsigned short,
8526
                                 vector unsigned short,
8527
                                 vector unsigned short);
8528
 
8529
vector signed short vec_mradds (vector signed short,
8530
                                vector signed short,
8531
                                vector signed short);
8532
 
8533
vector unsigned int vec_msum (vector unsigned char,
8534
                              vector unsigned char,
8535
                              vector unsigned int);
8536
vector signed int vec_msum (vector signed char,
8537
                            vector unsigned char,
8538
                            vector signed int);
8539
vector unsigned int vec_msum (vector unsigned short,
8540
                              vector unsigned short,
8541
                              vector unsigned int);
8542
vector signed int vec_msum (vector signed short,
8543
                            vector signed short,
8544
                            vector signed int);
8545
 
8546
vector signed int vec_vmsumshm (vector signed short,
8547
                                vector signed short,
8548
                                vector signed int);
8549
 
8550
vector unsigned int vec_vmsumuhm (vector unsigned short,
8551
                                  vector unsigned short,
8552
                                  vector unsigned int);
8553
 
8554
vector signed int vec_vmsummbm (vector signed char,
8555
                                vector unsigned char,
8556
                                vector signed int);
8557
 
8558
vector unsigned int vec_vmsumubm (vector unsigned char,
8559
                                  vector unsigned char,
8560
                                  vector unsigned int);
8561
 
8562
vector unsigned int vec_msums (vector unsigned short,
8563
                               vector unsigned short,
8564
                               vector unsigned int);
8565
vector signed int vec_msums (vector signed short,
8566
                             vector signed short,
8567
                             vector signed int);
8568
 
8569
vector signed int vec_vmsumshs (vector signed short,
8570
                                vector signed short,
8571
                                vector signed int);
8572
 
8573
vector unsigned int vec_vmsumuhs (vector unsigned short,
8574
                                  vector unsigned short,
8575
                                  vector unsigned int);
8576
 
8577
void vec_mtvscr (vector signed int);
8578
void vec_mtvscr (vector unsigned int);
8579
void vec_mtvscr (vector bool int);
8580
void vec_mtvscr (vector signed short);
8581
void vec_mtvscr (vector unsigned short);
8582
void vec_mtvscr (vector bool short);
8583
void vec_mtvscr (vector pixel);
8584
void vec_mtvscr (vector signed char);
8585
void vec_mtvscr (vector unsigned char);
8586
void vec_mtvscr (vector bool char);
8587
 
8588
vector unsigned short vec_mule (vector unsigned char,
8589
                                vector unsigned char);
8590
vector signed short vec_mule (vector signed char,
8591
                              vector signed char);
8592
vector unsigned int vec_mule (vector unsigned short,
8593
                              vector unsigned short);
8594
vector signed int vec_mule (vector signed short, vector signed short);
8595
 
8596
vector signed int vec_vmulesh (vector signed short,
8597
                               vector signed short);
8598
 
8599
vector unsigned int vec_vmuleuh (vector unsigned short,
8600
                                 vector unsigned short);
8601
 
8602
vector signed short vec_vmulesb (vector signed char,
8603
                                 vector signed char);
8604
 
8605
vector unsigned short vec_vmuleub (vector unsigned char,
8606
                                  vector unsigned char);
8607
 
8608
vector unsigned short vec_mulo (vector unsigned char,
8609
                                vector unsigned char);
8610
vector signed short vec_mulo (vector signed char, vector signed char);
8611
vector unsigned int vec_mulo (vector unsigned short,
8612
                              vector unsigned short);
8613
vector signed int vec_mulo (vector signed short, vector signed short);
8614
 
8615
vector signed int vec_vmulosh (vector signed short,
8616
                               vector signed short);
8617
 
8618
vector unsigned int vec_vmulouh (vector unsigned short,
8619
                                 vector unsigned short);
8620
 
8621
vector signed short vec_vmulosb (vector signed char,
8622
                                 vector signed char);
8623
 
8624
vector unsigned short vec_vmuloub (vector unsigned char,
8625
                                   vector unsigned char);
8626
 
8627
vector float vec_nmsub (vector float, vector float, vector float);
8628
 
8629
vector float vec_nor (vector float, vector float);
8630
vector signed int vec_nor (vector signed int, vector signed int);
8631
vector unsigned int vec_nor (vector unsigned int, vector unsigned int);
8632
vector bool int vec_nor (vector bool int, vector bool int);
8633
vector signed short vec_nor (vector signed short, vector signed short);
8634
vector unsigned short vec_nor (vector unsigned short,
8635
                               vector unsigned short);
8636
vector bool short vec_nor (vector bool short, vector bool short);
8637
vector signed char vec_nor (vector signed char, vector signed char);
8638
vector unsigned char vec_nor (vector unsigned char,
8639
                              vector unsigned char);
8640
vector bool char vec_nor (vector bool char, vector bool char);
8641
 
8642
vector float vec_or (vector float, vector float);
8643
vector float vec_or (vector float, vector bool int);
8644
vector float vec_or (vector bool int, vector float);
8645
vector bool int vec_or (vector bool int, vector bool int);
8646
vector signed int vec_or (vector bool int, vector signed int);
8647
vector signed int vec_or (vector signed int, vector bool int);
8648
vector signed int vec_or (vector signed int, vector signed int);
8649
vector unsigned int vec_or (vector bool int, vector unsigned int);
8650
vector unsigned int vec_or (vector unsigned int, vector bool int);
8651
vector unsigned int vec_or (vector unsigned int, vector unsigned int);
8652
vector bool short vec_or (vector bool short, vector bool short);
8653
vector signed short vec_or (vector bool short, vector signed short);
8654
vector signed short vec_or (vector signed short, vector bool short);
8655
vector signed short vec_or (vector signed short, vector signed short);
8656
vector unsigned short vec_or (vector bool short, vector unsigned short);
8657
vector unsigned short vec_or (vector unsigned short, vector bool short);
8658
vector unsigned short vec_or (vector unsigned short,
8659
                              vector unsigned short);
8660
vector signed char vec_or (vector bool char, vector signed char);
8661
vector bool char vec_or (vector bool char, vector bool char);
8662
vector signed char vec_or (vector signed char, vector bool char);
8663
vector signed char vec_or (vector signed char, vector signed char);
8664
vector unsigned char vec_or (vector bool char, vector unsigned char);
8665
vector unsigned char vec_or (vector unsigned char, vector bool char);
8666
vector unsigned char vec_or (vector unsigned char,
8667
                             vector unsigned char);
8668
 
8669
vector signed char vec_pack (vector signed short, vector signed short);
8670
vector unsigned char vec_pack (vector unsigned short,
8671
                               vector unsigned short);
8672
vector bool char vec_pack (vector bool short, vector bool short);
8673
vector signed short vec_pack (vector signed int, vector signed int);
8674
vector unsigned short vec_pack (vector unsigned int,
8675
                                vector unsigned int);
8676
vector bool short vec_pack (vector bool int, vector bool int);
8677
 
8678
vector bool short vec_vpkuwum (vector bool int, vector bool int);
8679
vector signed short vec_vpkuwum (vector signed int, vector signed int);
8680
vector unsigned short vec_vpkuwum (vector unsigned int,
8681
                                   vector unsigned int);
8682
 
8683
vector bool char vec_vpkuhum (vector bool short, vector bool short);
8684
vector signed char vec_vpkuhum (vector signed short,
8685
                                vector signed short);
8686
vector unsigned char vec_vpkuhum (vector unsigned short,
8687
                                  vector unsigned short);
8688
 
8689
vector pixel vec_packpx (vector unsigned int, vector unsigned int);
8690
 
8691
vector unsigned char vec_packs (vector unsigned short,
8692
                                vector unsigned short);
8693
vector signed char vec_packs (vector signed short, vector signed short);
8694
vector unsigned short vec_packs (vector unsigned int,
8695
                                 vector unsigned int);
8696
vector signed short vec_packs (vector signed int, vector signed int);
8697
 
8698
vector signed short vec_vpkswss (vector signed int, vector signed int);
8699
 
8700
vector unsigned short vec_vpkuwus (vector unsigned int,
8701
                                   vector unsigned int);
8702
 
8703
vector signed char vec_vpkshss (vector signed short,
8704
                                vector signed short);
8705
 
8706
vector unsigned char vec_vpkuhus (vector unsigned short,
8707
                                  vector unsigned short);
8708
 
8709
vector unsigned char vec_packsu (vector unsigned short,
8710
                                 vector unsigned short);
8711
vector unsigned char vec_packsu (vector signed short,
8712
                                 vector signed short);
8713
vector unsigned short vec_packsu (vector unsigned int,
8714
                                  vector unsigned int);
8715
vector unsigned short vec_packsu (vector signed int, vector signed int);
8716
 
8717
vector unsigned short vec_vpkswus (vector signed int,
8718
                                   vector signed int);
8719
 
8720
vector unsigned char vec_vpkshus (vector signed short,
8721
                                  vector signed short);
8722
 
8723
vector float vec_perm (vector float,
8724
                       vector float,
8725
                       vector unsigned char);
8726
vector signed int vec_perm (vector signed int,
8727
                            vector signed int,
8728
                            vector unsigned char);
8729
vector unsigned int vec_perm (vector unsigned int,
8730
                              vector unsigned int,
8731
                              vector unsigned char);
8732
vector bool int vec_perm (vector bool int,
8733
                          vector bool int,
8734
                          vector unsigned char);
8735
vector signed short vec_perm (vector signed short,
8736
                              vector signed short,
8737
                              vector unsigned char);
8738
vector unsigned short vec_perm (vector unsigned short,
8739
                                vector unsigned short,
8740
                                vector unsigned char);
8741
vector bool short vec_perm (vector bool short,
8742
                            vector bool short,
8743
                            vector unsigned char);
8744
vector pixel vec_perm (vector pixel,
8745
                       vector pixel,
8746
                       vector unsigned char);
8747
vector signed char vec_perm (vector signed char,
8748
                             vector signed char,
8749
                             vector unsigned char);
8750
vector unsigned char vec_perm (vector unsigned char,
8751
                               vector unsigned char,
8752
                               vector unsigned char);
8753
vector bool char vec_perm (vector bool char,
8754
                           vector bool char,
8755
                           vector unsigned char);
8756
 
8757
vector float vec_re (vector float);
8758
 
8759
vector signed char vec_rl (vector signed char,
8760
                           vector unsigned char);
8761
vector unsigned char vec_rl (vector unsigned char,
8762
                             vector unsigned char);
8763
vector signed short vec_rl (vector signed short, vector unsigned short);
8764
vector unsigned short vec_rl (vector unsigned short,
8765
                              vector unsigned short);
8766
vector signed int vec_rl (vector signed int, vector unsigned int);
8767
vector unsigned int vec_rl (vector unsigned int, vector unsigned int);
8768
 
8769
vector signed int vec_vrlw (vector signed int, vector unsigned int);
8770
vector unsigned int vec_vrlw (vector unsigned int, vector unsigned int);
8771
 
8772
vector signed short vec_vrlh (vector signed short,
8773
                              vector unsigned short);
8774
vector unsigned short vec_vrlh (vector unsigned short,
8775
                                vector unsigned short);
8776
 
8777
vector signed char vec_vrlb (vector signed char, vector unsigned char);
8778
vector unsigned char vec_vrlb (vector unsigned char,
8779
                               vector unsigned char);
8780
 
8781
vector float vec_round (vector float);
8782
 
8783
vector float vec_rsqrte (vector float);
8784
 
8785
vector float vec_sel (vector float, vector float, vector bool int);
8786
vector float vec_sel (vector float, vector float, vector unsigned int);
8787
vector signed int vec_sel (vector signed int,
8788
                           vector signed int,
8789
                           vector bool int);
8790
vector signed int vec_sel (vector signed int,
8791
                           vector signed int,
8792
                           vector unsigned int);
8793
vector unsigned int vec_sel (vector unsigned int,
8794
                             vector unsigned int,
8795
                             vector bool int);
8796
vector unsigned int vec_sel (vector unsigned int,
8797
                             vector unsigned int,
8798
                             vector unsigned int);
8799
vector bool int vec_sel (vector bool int,
8800
                         vector bool int,
8801
                         vector bool int);
8802
vector bool int vec_sel (vector bool int,
8803
                         vector bool int,
8804
                         vector unsigned int);
8805
vector signed short vec_sel (vector signed short,
8806
                             vector signed short,
8807
                             vector bool short);
8808
vector signed short vec_sel (vector signed short,
8809
                             vector signed short,
8810
                             vector unsigned short);
8811
vector unsigned short vec_sel (vector unsigned short,
8812
                               vector unsigned short,
8813
                               vector bool short);
8814
vector unsigned short vec_sel (vector unsigned short,
8815
                               vector unsigned short,
8816
                               vector unsigned short);
8817
vector bool short vec_sel (vector bool short,
8818
                           vector bool short,
8819
                           vector bool short);
8820
vector bool short vec_sel (vector bool short,
8821
                           vector bool short,
8822
                           vector unsigned short);
8823
vector signed char vec_sel (vector signed char,
8824
                            vector signed char,
8825
                            vector bool char);
8826
vector signed char vec_sel (vector signed char,
8827
                            vector signed char,
8828
                            vector unsigned char);
8829
vector unsigned char vec_sel (vector unsigned char,
8830
                              vector unsigned char,
8831
                              vector bool char);
8832
vector unsigned char vec_sel (vector unsigned char,
8833
                              vector unsigned char,
8834
                              vector unsigned char);
8835
vector bool char vec_sel (vector bool char,
8836
                          vector bool char,
8837
                          vector bool char);
8838
vector bool char vec_sel (vector bool char,
8839
                          vector bool char,
8840
                          vector unsigned char);
8841
 
8842
vector signed char vec_sl (vector signed char,
8843
                           vector unsigned char);
8844
vector unsigned char vec_sl (vector unsigned char,
8845
                             vector unsigned char);
8846
vector signed short vec_sl (vector signed short, vector unsigned short);
8847
vector unsigned short vec_sl (vector unsigned short,
8848
                              vector unsigned short);
8849
vector signed int vec_sl (vector signed int, vector unsigned int);
8850
vector unsigned int vec_sl (vector unsigned int, vector unsigned int);
8851
 
8852
vector signed int vec_vslw (vector signed int, vector unsigned int);
8853
vector unsigned int vec_vslw (vector unsigned int, vector unsigned int);
8854
 
8855
vector signed short vec_vslh (vector signed short,
8856
                              vector unsigned short);
8857
vector unsigned short vec_vslh (vector unsigned short,
8858
                                vector unsigned short);
8859
 
8860
vector signed char vec_vslb (vector signed char, vector unsigned char);
8861
vector unsigned char vec_vslb (vector unsigned char,
8862
                               vector unsigned char);
8863
 
8864
vector float vec_sld (vector float, vector float, const int);
8865
vector signed int vec_sld (vector signed int,
8866
                           vector signed int,
8867
                           const int);
8868
vector unsigned int vec_sld (vector unsigned int,
8869
                             vector unsigned int,
8870
                             const int);
8871
vector bool int vec_sld (vector bool int,
8872
                         vector bool int,
8873
                         const int);
8874
vector signed short vec_sld (vector signed short,
8875
                             vector signed short,
8876
                             const int);
8877
vector unsigned short vec_sld (vector unsigned short,
8878
                               vector unsigned short,
8879
                               const int);
8880
vector bool short vec_sld (vector bool short,
8881
                           vector bool short,
8882
                           const int);
8883
vector pixel vec_sld (vector pixel,
8884
                      vector pixel,
8885
                      const int);
8886
vector signed char vec_sld (vector signed char,
8887
                            vector signed char,
8888
                            const int);
8889
vector unsigned char vec_sld (vector unsigned char,
8890
                              vector unsigned char,
8891
                              const int);
8892
vector bool char vec_sld (vector bool char,
8893
                          vector bool char,
8894
                          const int);
8895
 
8896
vector signed int vec_sll (vector signed int,
8897
                           vector unsigned int);
8898
vector signed int vec_sll (vector signed int,
8899
                           vector unsigned short);
8900
vector signed int vec_sll (vector signed int,
8901
                           vector unsigned char);
8902
vector unsigned int vec_sll (vector unsigned int,
8903
                             vector unsigned int);
8904
vector unsigned int vec_sll (vector unsigned int,
8905
                             vector unsigned short);
8906
vector unsigned int vec_sll (vector unsigned int,
8907
                             vector unsigned char);
8908
vector bool int vec_sll (vector bool int,
8909
                         vector unsigned int);
8910
vector bool int vec_sll (vector bool int,
8911
                         vector unsigned short);
8912
vector bool int vec_sll (vector bool int,
8913
                         vector unsigned char);
8914
vector signed short vec_sll (vector signed short,
8915
                             vector unsigned int);
8916
vector signed short vec_sll (vector signed short,
8917
                             vector unsigned short);
8918
vector signed short vec_sll (vector signed short,
8919
                             vector unsigned char);
8920
vector unsigned short vec_sll (vector unsigned short,
8921
                               vector unsigned int);
8922
vector unsigned short vec_sll (vector unsigned short,
8923
                               vector unsigned short);
8924
vector unsigned short vec_sll (vector unsigned short,
8925
                               vector unsigned char);
8926
vector bool short vec_sll (vector bool short, vector unsigned int);
8927
vector bool short vec_sll (vector bool short, vector unsigned short);
8928
vector bool short vec_sll (vector bool short, vector unsigned char);
8929
vector pixel vec_sll (vector pixel, vector unsigned int);
8930
vector pixel vec_sll (vector pixel, vector unsigned short);
8931
vector pixel vec_sll (vector pixel, vector unsigned char);
8932
vector signed char vec_sll (vector signed char, vector unsigned int);
8933
vector signed char vec_sll (vector signed char, vector unsigned short);
8934
vector signed char vec_sll (vector signed char, vector unsigned char);
8935
vector unsigned char vec_sll (vector unsigned char,
8936
                              vector unsigned int);
8937
vector unsigned char vec_sll (vector unsigned char,
8938
                              vector unsigned short);
8939
vector unsigned char vec_sll (vector unsigned char,
8940
                              vector unsigned char);
8941
vector bool char vec_sll (vector bool char, vector unsigned int);
8942
vector bool char vec_sll (vector bool char, vector unsigned short);
8943
vector bool char vec_sll (vector bool char, vector unsigned char);
8944
 
8945
vector float vec_slo (vector float, vector signed char);
8946
vector float vec_slo (vector float, vector unsigned char);
8947
vector signed int vec_slo (vector signed int, vector signed char);
8948
vector signed int vec_slo (vector signed int, vector unsigned char);
8949
vector unsigned int vec_slo (vector unsigned int, vector signed char);
8950
vector unsigned int vec_slo (vector unsigned int, vector unsigned char);
8951
vector signed short vec_slo (vector signed short, vector signed char);
8952
vector signed short vec_slo (vector signed short, vector unsigned char);
8953
vector unsigned short vec_slo (vector unsigned short,
8954
                               vector signed char);
8955
vector unsigned short vec_slo (vector unsigned short,
8956
                               vector unsigned char);
8957
vector pixel vec_slo (vector pixel, vector signed char);
8958
vector pixel vec_slo (vector pixel, vector unsigned char);
8959
vector signed char vec_slo (vector signed char, vector signed char);
8960
vector signed char vec_slo (vector signed char, vector unsigned char);
8961
vector unsigned char vec_slo (vector unsigned char, vector signed char);
8962
vector unsigned char vec_slo (vector unsigned char,
8963
                              vector unsigned char);
8964
 
8965
vector signed char vec_splat (vector signed char, const int);
8966
vector unsigned char vec_splat (vector unsigned char, const int);
8967
vector bool char vec_splat (vector bool char, const int);
8968
vector signed short vec_splat (vector signed short, const int);
8969
vector unsigned short vec_splat (vector unsigned short, const int);
8970
vector bool short vec_splat (vector bool short, const int);
8971
vector pixel vec_splat (vector pixel, const int);
8972
vector float vec_splat (vector float, const int);
8973
vector signed int vec_splat (vector signed int, const int);
8974
vector unsigned int vec_splat (vector unsigned int, const int);
8975
vector bool int vec_splat (vector bool int, const int);
8976
 
8977
vector float vec_vspltw (vector float, const int);
8978
vector signed int vec_vspltw (vector signed int, const int);
8979
vector unsigned int vec_vspltw (vector unsigned int, const int);
8980
vector bool int vec_vspltw (vector bool int, const int);
8981
 
8982
vector bool short vec_vsplth (vector bool short, const int);
8983
vector signed short vec_vsplth (vector signed short, const int);
8984
vector unsigned short vec_vsplth (vector unsigned short, const int);
8985
vector pixel vec_vsplth (vector pixel, const int);
8986
 
8987
vector signed char vec_vspltb (vector signed char, const int);
8988
vector unsigned char vec_vspltb (vector unsigned char, const int);
8989
vector bool char vec_vspltb (vector bool char, const int);
8990
 
8991
vector signed char vec_splat_s8 (const int);
8992
 
8993
vector signed short vec_splat_s16 (const int);
8994
 
8995
vector signed int vec_splat_s32 (const int);
8996
 
8997
vector unsigned char vec_splat_u8 (const int);
8998
 
8999
vector unsigned short vec_splat_u16 (const int);
9000
 
9001
vector unsigned int vec_splat_u32 (const int);
9002
 
9003
vector signed char vec_sr (vector signed char, vector unsigned char);
9004
vector unsigned char vec_sr (vector unsigned char,
9005
                             vector unsigned char);
9006
vector signed short vec_sr (vector signed short,
9007
                            vector unsigned short);
9008
vector unsigned short vec_sr (vector unsigned short,
9009
                              vector unsigned short);
9010
vector signed int vec_sr (vector signed int, vector unsigned int);
9011
vector unsigned int vec_sr (vector unsigned int, vector unsigned int);
9012
 
9013
vector signed int vec_vsrw (vector signed int, vector unsigned int);
9014
vector unsigned int vec_vsrw (vector unsigned int, vector unsigned int);
9015
 
9016
vector signed short vec_vsrh (vector signed short,
9017
                              vector unsigned short);
9018
vector unsigned short vec_vsrh (vector unsigned short,
9019
                                vector unsigned short);
9020
 
9021
vector signed char vec_vsrb (vector signed char, vector unsigned char);
9022
vector unsigned char vec_vsrb (vector unsigned char,
9023
                               vector unsigned char);
9024
 
9025
vector signed char vec_sra (vector signed char, vector unsigned char);
9026
vector unsigned char vec_sra (vector unsigned char,
9027
                              vector unsigned char);
9028
vector signed short vec_sra (vector signed short,
9029
                             vector unsigned short);
9030
vector unsigned short vec_sra (vector unsigned short,
9031
                               vector unsigned short);
9032
vector signed int vec_sra (vector signed int, vector unsigned int);
9033
vector unsigned int vec_sra (vector unsigned int, vector unsigned int);
9034
 
9035
vector signed int vec_vsraw (vector signed int, vector unsigned int);
9036
vector unsigned int vec_vsraw (vector unsigned int,
9037
                               vector unsigned int);
9038
 
9039
vector signed short vec_vsrah (vector signed short,
9040
                               vector unsigned short);
9041
vector unsigned short vec_vsrah (vector unsigned short,
9042
                                 vector unsigned short);
9043
 
9044
vector signed char vec_vsrab (vector signed char, vector unsigned char);
9045
vector unsigned char vec_vsrab (vector unsigned char,
9046
                                vector unsigned char);
9047
 
9048
vector signed int vec_srl (vector signed int, vector unsigned int);
9049
vector signed int vec_srl (vector signed int, vector unsigned short);
9050
vector signed int vec_srl (vector signed int, vector unsigned char);
9051
vector unsigned int vec_srl (vector unsigned int, vector unsigned int);
9052
vector unsigned int vec_srl (vector unsigned int,
9053
                             vector unsigned short);
9054
vector unsigned int vec_srl (vector unsigned int, vector unsigned char);
9055
vector bool int vec_srl (vector bool int, vector unsigned int);
9056
vector bool int vec_srl (vector bool int, vector unsigned short);
9057
vector bool int vec_srl (vector bool int, vector unsigned char);
9058
vector signed short vec_srl (vector signed short, vector unsigned int);
9059
vector signed short vec_srl (vector signed short,
9060
                             vector unsigned short);
9061
vector signed short vec_srl (vector signed short, vector unsigned char);
9062
vector unsigned short vec_srl (vector unsigned short,
9063
                               vector unsigned int);
9064
vector unsigned short vec_srl (vector unsigned short,
9065
                               vector unsigned short);
9066
vector unsigned short vec_srl (vector unsigned short,
9067
                               vector unsigned char);
9068
vector bool short vec_srl (vector bool short, vector unsigned int);
9069
vector bool short vec_srl (vector bool short, vector unsigned short);
9070
vector bool short vec_srl (vector bool short, vector unsigned char);
9071
vector pixel vec_srl (vector pixel, vector unsigned int);
9072
vector pixel vec_srl (vector pixel, vector unsigned short);
9073
vector pixel vec_srl (vector pixel, vector unsigned char);
9074
vector signed char vec_srl (vector signed char, vector unsigned int);
9075
vector signed char vec_srl (vector signed char, vector unsigned short);
9076
vector signed char vec_srl (vector signed char, vector unsigned char);
9077
vector unsigned char vec_srl (vector unsigned char,
9078
                              vector unsigned int);
9079
vector unsigned char vec_srl (vector unsigned char,
9080
                              vector unsigned short);
9081
vector unsigned char vec_srl (vector unsigned char,
9082
                              vector unsigned char);
9083
vector bool char vec_srl (vector bool char, vector unsigned int);
9084
vector bool char vec_srl (vector bool char, vector unsigned short);
9085
vector bool char vec_srl (vector bool char, vector unsigned char);
9086
 
9087
vector float vec_sro (vector float, vector signed char);
9088
vector float vec_sro (vector float, vector unsigned char);
9089
vector signed int vec_sro (vector signed int, vector signed char);
9090
vector signed int vec_sro (vector signed int, vector unsigned char);
9091
vector unsigned int vec_sro (vector unsigned int, vector signed char);
9092
vector unsigned int vec_sro (vector unsigned int, vector unsigned char);
9093
vector signed short vec_sro (vector signed short, vector signed char);
9094
vector signed short vec_sro (vector signed short, vector unsigned char);
9095
vector unsigned short vec_sro (vector unsigned short,
9096
                               vector signed char);
9097
vector unsigned short vec_sro (vector unsigned short,
9098
                               vector unsigned char);
9099
vector pixel vec_sro (vector pixel, vector signed char);
9100
vector pixel vec_sro (vector pixel, vector unsigned char);
9101
vector signed char vec_sro (vector signed char, vector signed char);
9102
vector signed char vec_sro (vector signed char, vector unsigned char);
9103
vector unsigned char vec_sro (vector unsigned char, vector signed char);
9104
vector unsigned char vec_sro (vector unsigned char,
9105
                              vector unsigned char);
9106
 
9107
void vec_st (vector float, int, vector float *);
9108
void vec_st (vector float, int, float *);
9109
void vec_st (vector signed int, int, vector signed int *);
9110
void vec_st (vector signed int, int, int *);
9111
void vec_st (vector unsigned int, int, vector unsigned int *);
9112
void vec_st (vector unsigned int, int, unsigned int *);
9113
void vec_st (vector bool int, int, vector bool int *);
9114
void vec_st (vector bool int, int, unsigned int *);
9115
void vec_st (vector bool int, int, int *);
9116
void vec_st (vector signed short, int, vector signed short *);
9117
void vec_st (vector signed short, int, short *);
9118
void vec_st (vector unsigned short, int, vector unsigned short *);
9119
void vec_st (vector unsigned short, int, unsigned short *);
9120
void vec_st (vector bool short, int, vector bool short *);
9121
void vec_st (vector bool short, int, unsigned short *);
9122
void vec_st (vector pixel, int, vector pixel *);
9123
void vec_st (vector pixel, int, unsigned short *);
9124
void vec_st (vector pixel, int, short *);
9125
void vec_st (vector bool short, int, short *);
9126
void vec_st (vector signed char, int, vector signed char *);
9127
void vec_st (vector signed char, int, signed char *);
9128
void vec_st (vector unsigned char, int, vector unsigned char *);
9129
void vec_st (vector unsigned char, int, unsigned char *);
9130
void vec_st (vector bool char, int, vector bool char *);
9131
void vec_st (vector bool char, int, unsigned char *);
9132
void vec_st (vector bool char, int, signed char *);
9133
 
9134
void vec_ste (vector signed char, int, signed char *);
9135
void vec_ste (vector unsigned char, int, unsigned char *);
9136
void vec_ste (vector bool char, int, signed char *);
9137
void vec_ste (vector bool char, int, unsigned char *);
9138
void vec_ste (vector signed short, int, short *);
9139
void vec_ste (vector unsigned short, int, unsigned short *);
9140
void vec_ste (vector bool short, int, short *);
9141
void vec_ste (vector bool short, int, unsigned short *);
9142
void vec_ste (vector pixel, int, short *);
9143
void vec_ste (vector pixel, int, unsigned short *);
9144
void vec_ste (vector float, int, float *);
9145
void vec_ste (vector signed int, int, int *);
9146
void vec_ste (vector unsigned int, int, unsigned int *);
9147
void vec_ste (vector bool int, int, int *);
9148
void vec_ste (vector bool int, int, unsigned int *);
9149
 
9150
void vec_stvewx (vector float, int, float *);
9151
void vec_stvewx (vector signed int, int, int *);
9152
void vec_stvewx (vector unsigned int, int, unsigned int *);
9153
void vec_stvewx (vector bool int, int, int *);
9154
void vec_stvewx (vector bool int, int, unsigned int *);
9155
 
9156
void vec_stvehx (vector signed short, int, short *);
9157
void vec_stvehx (vector unsigned short, int, unsigned short *);
9158
void vec_stvehx (vector bool short, int, short *);
9159
void vec_stvehx (vector bool short, int, unsigned short *);
9160
void vec_stvehx (vector pixel, int, short *);
9161
void vec_stvehx (vector pixel, int, unsigned short *);
9162
 
9163
void vec_stvebx (vector signed char, int, signed char *);
9164
void vec_stvebx (vector unsigned char, int, unsigned char *);
9165
void vec_stvebx (vector bool char, int, signed char *);
9166
void vec_stvebx (vector bool char, int, unsigned char *);
9167
 
9168
void vec_stl (vector float, int, vector float *);
9169
void vec_stl (vector float, int, float *);
9170
void vec_stl (vector signed int, int, vector signed int *);
9171
void vec_stl (vector signed int, int, int *);
9172
void vec_stl (vector unsigned int, int, vector unsigned int *);
9173
void vec_stl (vector unsigned int, int, unsigned int *);
9174
void vec_stl (vector bool int, int, vector bool int *);
9175
void vec_stl (vector bool int, int, unsigned int *);
9176
void vec_stl (vector bool int, int, int *);
9177
void vec_stl (vector signed short, int, vector signed short *);
9178
void vec_stl (vector signed short, int, short *);
9179
void vec_stl (vector unsigned short, int, vector unsigned short *);
9180
void vec_stl (vector unsigned short, int, unsigned short *);
9181
void vec_stl (vector bool short, int, vector bool short *);
9182
void vec_stl (vector bool short, int, unsigned short *);
9183
void vec_stl (vector bool short, int, short *);
9184
void vec_stl (vector pixel, int, vector pixel *);
9185
void vec_stl (vector pixel, int, unsigned short *);
9186
void vec_stl (vector pixel, int, short *);
9187
void vec_stl (vector signed char, int, vector signed char *);
9188
void vec_stl (vector signed char, int, signed char *);
9189
void vec_stl (vector unsigned char, int, vector unsigned char *);
9190
void vec_stl (vector unsigned char, int, unsigned char *);
9191
void vec_stl (vector bool char, int, vector bool char *);
9192
void vec_stl (vector bool char, int, unsigned char *);
9193
void vec_stl (vector bool char, int, signed char *);
9194
 
9195
vector signed char vec_sub (vector bool char, vector signed char);
9196
vector signed char vec_sub (vector signed char, vector bool char);
9197
vector signed char vec_sub (vector signed char, vector signed char);
9198
vector unsigned char vec_sub (vector bool char, vector unsigned char);
9199
vector unsigned char vec_sub (vector unsigned char, vector bool char);
9200
vector unsigned char vec_sub (vector unsigned char,
9201
                              vector unsigned char);
9202
vector signed short vec_sub (vector bool short, vector signed short);
9203
vector signed short vec_sub (vector signed short, vector bool short);
9204
vector signed short vec_sub (vector signed short, vector signed short);
9205
vector unsigned short vec_sub (vector bool short,
9206
                               vector unsigned short);
9207
vector unsigned short vec_sub (vector unsigned short,
9208
                               vector bool short);
9209
vector unsigned short vec_sub (vector unsigned short,
9210
                               vector unsigned short);
9211
vector signed int vec_sub (vector bool int, vector signed int);
9212
vector signed int vec_sub (vector signed int, vector bool int);
9213
vector signed int vec_sub (vector signed int, vector signed int);
9214
vector unsigned int vec_sub (vector bool int, vector unsigned int);
9215
vector unsigned int vec_sub (vector unsigned int, vector bool int);
9216
vector unsigned int vec_sub (vector unsigned int, vector unsigned int);
9217
vector float vec_sub (vector float, vector float);
9218
 
9219
vector float vec_vsubfp (vector float, vector float);
9220
 
9221
vector signed int vec_vsubuwm (vector bool int, vector signed int);
9222
vector signed int vec_vsubuwm (vector signed int, vector bool int);
9223
vector signed int vec_vsubuwm (vector signed int, vector signed int);
9224
vector unsigned int vec_vsubuwm (vector bool int, vector unsigned int);
9225
vector unsigned int vec_vsubuwm (vector unsigned int, vector bool int);
9226
vector unsigned int vec_vsubuwm (vector unsigned int,
9227
                                 vector unsigned int);
9228
 
9229
vector signed short vec_vsubuhm (vector bool short,
9230
                                 vector signed short);
9231
vector signed short vec_vsubuhm (vector signed short,
9232
                                 vector bool short);
9233
vector signed short vec_vsubuhm (vector signed short,
9234
                                 vector signed short);
9235
vector unsigned short vec_vsubuhm (vector bool short,
9236
                                   vector unsigned short);
9237
vector unsigned short vec_vsubuhm (vector unsigned short,
9238
                                   vector bool short);
9239
vector unsigned short vec_vsubuhm (vector unsigned short,
9240
                                   vector unsigned short);
9241
 
9242
vector signed char vec_vsububm (vector bool char, vector signed char);
9243
vector signed char vec_vsububm (vector signed char, vector bool char);
9244
vector signed char vec_vsububm (vector signed char, vector signed char);
9245
vector unsigned char vec_vsububm (vector bool char,
9246
                                  vector unsigned char);
9247
vector unsigned char vec_vsububm (vector unsigned char,
9248
                                  vector bool char);
9249
vector unsigned char vec_vsububm (vector unsigned char,
9250
                                  vector unsigned char);
9251
 
9252
vector unsigned int vec_subc (vector unsigned int, vector unsigned int);
9253
 
9254
vector unsigned char vec_subs (vector bool char, vector unsigned char);
9255
vector unsigned char vec_subs (vector unsigned char, vector bool char);
9256
vector unsigned char vec_subs (vector unsigned char,
9257
                               vector unsigned char);
9258
vector signed char vec_subs (vector bool char, vector signed char);
9259
vector signed char vec_subs (vector signed char, vector bool char);
9260
vector signed char vec_subs (vector signed char, vector signed char);
9261
vector unsigned short vec_subs (vector bool short,
9262
                                vector unsigned short);
9263
vector unsigned short vec_subs (vector unsigned short,
9264
                                vector bool short);
9265
vector unsigned short vec_subs (vector unsigned short,
9266
                                vector unsigned short);
9267
vector signed short vec_subs (vector bool short, vector signed short);
9268
vector signed short vec_subs (vector signed short, vector bool short);
9269
vector signed short vec_subs (vector signed short, vector signed short);
9270
vector unsigned int vec_subs (vector bool int, vector unsigned int);
9271
vector unsigned int vec_subs (vector unsigned int, vector bool int);
9272
vector unsigned int vec_subs (vector unsigned int, vector unsigned int);
9273
vector signed int vec_subs (vector bool int, vector signed int);
9274
vector signed int vec_subs (vector signed int, vector bool int);
9275
vector signed int vec_subs (vector signed int, vector signed int);
9276
 
9277
vector signed int vec_vsubsws (vector bool int, vector signed int);
9278
vector signed int vec_vsubsws (vector signed int, vector bool int);
9279
vector signed int vec_vsubsws (vector signed int, vector signed int);
9280
 
9281
vector unsigned int vec_vsubuws (vector bool int, vector unsigned int);
9282
vector unsigned int vec_vsubuws (vector unsigned int, vector bool int);
9283
vector unsigned int vec_vsubuws (vector unsigned int,
9284
                                 vector unsigned int);
9285
 
9286
vector signed short vec_vsubshs (vector bool short,
9287
                                 vector signed short);
9288
vector signed short vec_vsubshs (vector signed short,
9289
                                 vector bool short);
9290
vector signed short vec_vsubshs (vector signed short,
9291
                                 vector signed short);
9292
 
9293
vector unsigned short vec_vsubuhs (vector bool short,
9294
                                   vector unsigned short);
9295
vector unsigned short vec_vsubuhs (vector unsigned short,
9296
                                   vector bool short);
9297
vector unsigned short vec_vsubuhs (vector unsigned short,
9298
                                   vector unsigned short);
9299
 
9300
vector signed char vec_vsubsbs (vector bool char, vector signed char);
9301
vector signed char vec_vsubsbs (vector signed char, vector bool char);
9302
vector signed char vec_vsubsbs (vector signed char, vector signed char);
9303
 
9304
vector unsigned char vec_vsububs (vector bool char,
9305
                                  vector unsigned char);
9306
vector unsigned char vec_vsububs (vector unsigned char,
9307
                                  vector bool char);
9308
vector unsigned char vec_vsububs (vector unsigned char,
9309
                                  vector unsigned char);
9310
 
9311
vector unsigned int vec_sum4s (vector unsigned char,
9312
                               vector unsigned int);
9313
vector signed int vec_sum4s (vector signed char, vector signed int);
9314
vector signed int vec_sum4s (vector signed short, vector signed int);
9315
 
9316
vector signed int vec_vsum4shs (vector signed short, vector signed int);
9317
 
9318
vector signed int vec_vsum4sbs (vector signed char, vector signed int);
9319
 
9320
vector unsigned int vec_vsum4ubs (vector unsigned char,
9321
                                  vector unsigned int);
9322
 
9323
vector signed int vec_sum2s (vector signed int, vector signed int);
9324
 
9325
vector signed int vec_sums (vector signed int, vector signed int);
9326
 
9327
vector float vec_trunc (vector float);
9328
 
9329
vector signed short vec_unpackh (vector signed char);
9330
vector bool short vec_unpackh (vector bool char);
9331
vector signed int vec_unpackh (vector signed short);
9332
vector bool int vec_unpackh (vector bool short);
9333
vector unsigned int vec_unpackh (vector pixel);
9334
 
9335
vector bool int vec_vupkhsh (vector bool short);
9336
vector signed int vec_vupkhsh (vector signed short);
9337
 
9338
vector unsigned int vec_vupkhpx (vector pixel);
9339
 
9340
vector bool short vec_vupkhsb (vector bool char);
9341
vector signed short vec_vupkhsb (vector signed char);
9342
 
9343
vector signed short vec_unpackl (vector signed char);
9344
vector bool short vec_unpackl (vector bool char);
9345
vector unsigned int vec_unpackl (vector pixel);
9346
vector signed int vec_unpackl (vector signed short);
9347
vector bool int vec_unpackl (vector bool short);
9348
 
9349
vector unsigned int vec_vupklpx (vector pixel);
9350
 
9351
vector bool int vec_vupklsh (vector bool short);
9352
vector signed int vec_vupklsh (vector signed short);
9353
 
9354
vector bool short vec_vupklsb (vector bool char);
9355
vector signed short vec_vupklsb (vector signed char);
9356
 
9357
vector float vec_xor (vector float, vector float);
9358
vector float vec_xor (vector float, vector bool int);
9359
vector float vec_xor (vector bool int, vector float);
9360
vector bool int vec_xor (vector bool int, vector bool int);
9361
vector signed int vec_xor (vector bool int, vector signed int);
9362
vector signed int vec_xor (vector signed int, vector bool int);
9363
vector signed int vec_xor (vector signed int, vector signed int);
9364
vector unsigned int vec_xor (vector bool int, vector unsigned int);
9365
vector unsigned int vec_xor (vector unsigned int, vector bool int);
9366
vector unsigned int vec_xor (vector unsigned int, vector unsigned int);
9367
vector bool short vec_xor (vector bool short, vector bool short);
9368
vector signed short vec_xor (vector bool short, vector signed short);
9369
vector signed short vec_xor (vector signed short, vector bool short);
9370
vector signed short vec_xor (vector signed short, vector signed short);
9371
vector unsigned short vec_xor (vector bool short,
9372
                               vector unsigned short);
9373
vector unsigned short vec_xor (vector unsigned short,
9374
                               vector bool short);
9375
vector unsigned short vec_xor (vector unsigned short,
9376
                               vector unsigned short);
9377
vector signed char vec_xor (vector bool char, vector signed char);
9378
vector bool char vec_xor (vector bool char, vector bool char);
9379
vector signed char vec_xor (vector signed char, vector bool char);
9380
vector signed char vec_xor (vector signed char, vector signed char);
9381
vector unsigned char vec_xor (vector bool char, vector unsigned char);
9382
vector unsigned char vec_xor (vector unsigned char, vector bool char);
9383
vector unsigned char vec_xor (vector unsigned char,
9384
                              vector unsigned char);
9385
 
9386
int vec_all_eq (vector signed char, vector bool char);
9387
int vec_all_eq (vector signed char, vector signed char);
9388
int vec_all_eq (vector unsigned char, vector bool char);
9389
int vec_all_eq (vector unsigned char, vector unsigned char);
9390
int vec_all_eq (vector bool char, vector bool char);
9391
int vec_all_eq (vector bool char, vector unsigned char);
9392
int vec_all_eq (vector bool char, vector signed char);
9393
int vec_all_eq (vector signed short, vector bool short);
9394
int vec_all_eq (vector signed short, vector signed short);
9395
int vec_all_eq (vector unsigned short, vector bool short);
9396
int vec_all_eq (vector unsigned short, vector unsigned short);
9397
int vec_all_eq (vector bool short, vector bool short);
9398
int vec_all_eq (vector bool short, vector unsigned short);
9399
int vec_all_eq (vector bool short, vector signed short);
9400
int vec_all_eq (vector pixel, vector pixel);
9401
int vec_all_eq (vector signed int, vector bool int);
9402
int vec_all_eq (vector signed int, vector signed int);
9403
int vec_all_eq (vector unsigned int, vector bool int);
9404
int vec_all_eq (vector unsigned int, vector unsigned int);
9405
int vec_all_eq (vector bool int, vector bool int);
9406
int vec_all_eq (vector bool int, vector unsigned int);
9407
int vec_all_eq (vector bool int, vector signed int);
9408
int vec_all_eq (vector float, vector float);
9409
 
9410
int vec_all_ge (vector bool char, vector unsigned char);
9411
int vec_all_ge (vector unsigned char, vector bool char);
9412
int vec_all_ge (vector unsigned char, vector unsigned char);
9413
int vec_all_ge (vector bool char, vector signed char);
9414
int vec_all_ge (vector signed char, vector bool char);
9415
int vec_all_ge (vector signed char, vector signed char);
9416
int vec_all_ge (vector bool short, vector unsigned short);
9417
int vec_all_ge (vector unsigned short, vector bool short);
9418
int vec_all_ge (vector unsigned short, vector unsigned short);
9419
int vec_all_ge (vector signed short, vector signed short);
9420
int vec_all_ge (vector bool short, vector signed short);
9421
int vec_all_ge (vector signed short, vector bool short);
9422
int vec_all_ge (vector bool int, vector unsigned int);
9423
int vec_all_ge (vector unsigned int, vector bool int);
9424
int vec_all_ge (vector unsigned int, vector unsigned int);
9425
int vec_all_ge (vector bool int, vector signed int);
9426
int vec_all_ge (vector signed int, vector bool int);
9427
int vec_all_ge (vector signed int, vector signed int);
9428
int vec_all_ge (vector float, vector float);
9429
 
9430
int vec_all_gt (vector bool char, vector unsigned char);
9431
int vec_all_gt (vector unsigned char, vector bool char);
9432
int vec_all_gt (vector unsigned char, vector unsigned char);
9433
int vec_all_gt (vector bool char, vector signed char);
9434
int vec_all_gt (vector signed char, vector bool char);
9435
int vec_all_gt (vector signed char, vector signed char);
9436
int vec_all_gt (vector bool short, vector unsigned short);
9437
int vec_all_gt (vector unsigned short, vector bool short);
9438
int vec_all_gt (vector unsigned short, vector unsigned short);
9439
int vec_all_gt (vector bool short, vector signed short);
9440
int vec_all_gt (vector signed short, vector bool short);
9441
int vec_all_gt (vector signed short, vector signed short);
9442
int vec_all_gt (vector bool int, vector unsigned int);
9443
int vec_all_gt (vector unsigned int, vector bool int);
9444
int vec_all_gt (vector unsigned int, vector unsigned int);
9445
int vec_all_gt (vector bool int, vector signed int);
9446
int vec_all_gt (vector signed int, vector bool int);
9447
int vec_all_gt (vector signed int, vector signed int);
9448
int vec_all_gt (vector float, vector float);
9449
 
9450
int vec_all_in (vector float, vector float);
9451
 
9452
int vec_all_le (vector bool char, vector unsigned char);
9453
int vec_all_le (vector unsigned char, vector bool char);
9454
int vec_all_le (vector unsigned char, vector unsigned char);
9455
int vec_all_le (vector bool char, vector signed char);
9456
int vec_all_le (vector signed char, vector bool char);
9457
int vec_all_le (vector signed char, vector signed char);
9458
int vec_all_le (vector bool short, vector unsigned short);
9459
int vec_all_le (vector unsigned short, vector bool short);
9460
int vec_all_le (vector unsigned short, vector unsigned short);
9461
int vec_all_le (vector bool short, vector signed short);
9462
int vec_all_le (vector signed short, vector bool short);
9463
int vec_all_le (vector signed short, vector signed short);
9464
int vec_all_le (vector bool int, vector unsigned int);
9465
int vec_all_le (vector unsigned int, vector bool int);
9466
int vec_all_le (vector unsigned int, vector unsigned int);
9467
int vec_all_le (vector bool int, vector signed int);
9468
int vec_all_le (vector signed int, vector bool int);
9469
int vec_all_le (vector signed int, vector signed int);
9470
int vec_all_le (vector float, vector float);
9471
 
9472
int vec_all_lt (vector bool char, vector unsigned char);
9473
int vec_all_lt (vector unsigned char, vector bool char);
9474
int vec_all_lt (vector unsigned char, vector unsigned char);
9475
int vec_all_lt (vector bool char, vector signed char);
9476
int vec_all_lt (vector signed char, vector bool char);
9477
int vec_all_lt (vector signed char, vector signed char);
9478
int vec_all_lt (vector bool short, vector unsigned short);
9479
int vec_all_lt (vector unsigned short, vector bool short);
9480
int vec_all_lt (vector unsigned short, vector unsigned short);
9481
int vec_all_lt (vector bool short, vector signed short);
9482
int vec_all_lt (vector signed short, vector bool short);
9483
int vec_all_lt (vector signed short, vector signed short);
9484
int vec_all_lt (vector bool int, vector unsigned int);
9485
int vec_all_lt (vector unsigned int, vector bool int);
9486
int vec_all_lt (vector unsigned int, vector unsigned int);
9487
int vec_all_lt (vector bool int, vector signed int);
9488
int vec_all_lt (vector signed int, vector bool int);
9489
int vec_all_lt (vector signed int, vector signed int);
9490
int vec_all_lt (vector float, vector float);
9491
 
9492
int vec_all_nan (vector float);
9493
 
9494
int vec_all_ne (vector signed char, vector bool char);
9495
int vec_all_ne (vector signed char, vector signed char);
9496
int vec_all_ne (vector unsigned char, vector bool char);
9497
int vec_all_ne (vector unsigned char, vector unsigned char);
9498
int vec_all_ne (vector bool char, vector bool char);
9499
int vec_all_ne (vector bool char, vector unsigned char);
9500
int vec_all_ne (vector bool char, vector signed char);
9501
int vec_all_ne (vector signed short, vector bool short);
9502
int vec_all_ne (vector signed short, vector signed short);
9503
int vec_all_ne (vector unsigned short, vector bool short);
9504
int vec_all_ne (vector unsigned short, vector unsigned short);
9505
int vec_all_ne (vector bool short, vector bool short);
9506
int vec_all_ne (vector bool short, vector unsigned short);
9507
int vec_all_ne (vector bool short, vector signed short);
9508
int vec_all_ne (vector pixel, vector pixel);
9509
int vec_all_ne (vector signed int, vector bool int);
9510
int vec_all_ne (vector signed int, vector signed int);
9511
int vec_all_ne (vector unsigned int, vector bool int);
9512
int vec_all_ne (vector unsigned int, vector unsigned int);
9513
int vec_all_ne (vector bool int, vector bool int);
9514
int vec_all_ne (vector bool int, vector unsigned int);
9515
int vec_all_ne (vector bool int, vector signed int);
9516
int vec_all_ne (vector float, vector float);
9517
 
9518
int vec_all_nge (vector float, vector float);
9519
 
9520
int vec_all_ngt (vector float, vector float);
9521
 
9522
int vec_all_nle (vector float, vector float);
9523
 
9524
int vec_all_nlt (vector float, vector float);
9525
 
9526
int vec_all_numeric (vector float);
9527
 
9528
int vec_any_eq (vector signed char, vector bool char);
9529
int vec_any_eq (vector signed char, vector signed char);
9530
int vec_any_eq (vector unsigned char, vector bool char);
9531
int vec_any_eq (vector unsigned char, vector unsigned char);
9532
int vec_any_eq (vector bool char, vector bool char);
9533
int vec_any_eq (vector bool char, vector unsigned char);
9534
int vec_any_eq (vector bool char, vector signed char);
9535
int vec_any_eq (vector signed short, vector bool short);
9536
int vec_any_eq (vector signed short, vector signed short);
9537
int vec_any_eq (vector unsigned short, vector bool short);
9538
int vec_any_eq (vector unsigned short, vector unsigned short);
9539
int vec_any_eq (vector bool short, vector bool short);
9540
int vec_any_eq (vector bool short, vector unsigned short);
9541
int vec_any_eq (vector bool short, vector signed short);
9542
int vec_any_eq (vector pixel, vector pixel);
9543
int vec_any_eq (vector signed int, vector bool int);
9544
int vec_any_eq (vector signed int, vector signed int);
9545
int vec_any_eq (vector unsigned int, vector bool int);
9546
int vec_any_eq (vector unsigned int, vector unsigned int);
9547
int vec_any_eq (vector bool int, vector bool int);
9548
int vec_any_eq (vector bool int, vector unsigned int);
9549
int vec_any_eq (vector bool int, vector signed int);
9550
int vec_any_eq (vector float, vector float);
9551
 
9552
int vec_any_ge (vector signed char, vector bool char);
9553
int vec_any_ge (vector unsigned char, vector bool char);
9554
int vec_any_ge (vector unsigned char, vector unsigned char);
9555
int vec_any_ge (vector signed char, vector signed char);
9556
int vec_any_ge (vector bool char, vector unsigned char);
9557
int vec_any_ge (vector bool char, vector signed char);
9558
int vec_any_ge (vector unsigned short, vector bool short);
9559
int vec_any_ge (vector unsigned short, vector unsigned short);
9560
int vec_any_ge (vector signed short, vector signed short);
9561
int vec_any_ge (vector signed short, vector bool short);
9562
int vec_any_ge (vector bool short, vector unsigned short);
9563
int vec_any_ge (vector bool short, vector signed short);
9564
int vec_any_ge (vector signed int, vector bool int);
9565
int vec_any_ge (vector unsigned int, vector bool int);
9566
int vec_any_ge (vector unsigned int, vector unsigned int);
9567
int vec_any_ge (vector signed int, vector signed int);
9568
int vec_any_ge (vector bool int, vector unsigned int);
9569
int vec_any_ge (vector bool int, vector signed int);
9570
int vec_any_ge (vector float, vector float);
9571
 
9572
int vec_any_gt (vector bool char, vector unsigned char);
9573
int vec_any_gt (vector unsigned char, vector bool char);
9574
int vec_any_gt (vector unsigned char, vector unsigned char);
9575
int vec_any_gt (vector bool char, vector signed char);
9576
int vec_any_gt (vector signed char, vector bool char);
9577
int vec_any_gt (vector signed char, vector signed char);
9578
int vec_any_gt (vector bool short, vector unsigned short);
9579
int vec_any_gt (vector unsigned short, vector bool short);
9580
int vec_any_gt (vector unsigned short, vector unsigned short);
9581
int vec_any_gt (vector bool short, vector signed short);
9582
int vec_any_gt (vector signed short, vector bool short);
9583
int vec_any_gt (vector signed short, vector signed short);
9584
int vec_any_gt (vector bool int, vector unsigned int);
9585
int vec_any_gt (vector unsigned int, vector bool int);
9586
int vec_any_gt (vector unsigned int, vector unsigned int);
9587
int vec_any_gt (vector bool int, vector signed int);
9588
int vec_any_gt (vector signed int, vector bool int);
9589
int vec_any_gt (vector signed int, vector signed int);
9590
int vec_any_gt (vector float, vector float);
9591
 
9592
int vec_any_le (vector bool char, vector unsigned char);
9593
int vec_any_le (vector unsigned char, vector bool char);
9594
int vec_any_le (vector unsigned char, vector unsigned char);
9595
int vec_any_le (vector bool char, vector signed char);
9596
int vec_any_le (vector signed char, vector bool char);
9597
int vec_any_le (vector signed char, vector signed char);
9598
int vec_any_le (vector bool short, vector unsigned short);
9599
int vec_any_le (vector unsigned short, vector bool short);
9600
int vec_any_le (vector unsigned short, vector unsigned short);
9601
int vec_any_le (vector bool short, vector signed short);
9602
int vec_any_le (vector signed short, vector bool short);
9603
int vec_any_le (vector signed short, vector signed short);
9604
int vec_any_le (vector bool int, vector unsigned int);
9605
int vec_any_le (vector unsigned int, vector bool int);
9606
int vec_any_le (vector unsigned int, vector unsigned int);
9607
int vec_any_le (vector bool int, vector signed int);
9608
int vec_any_le (vector signed int, vector bool int);
9609
int vec_any_le (vector signed int, vector signed int);
9610
int vec_any_le (vector float, vector float);
9611
 
9612
int vec_any_lt (vector bool char, vector unsigned char);
9613
int vec_any_lt (vector unsigned char, vector bool char);
9614
int vec_any_lt (vector unsigned char, vector unsigned char);
9615
int vec_any_lt (vector bool char, vector signed char);
9616
int vec_any_lt (vector signed char, vector bool char);
9617
int vec_any_lt (vector signed char, vector signed char);
9618
int vec_any_lt (vector bool short, vector unsigned short);
9619
int vec_any_lt (vector unsigned short, vector bool short);
9620
int vec_any_lt (vector unsigned short, vector unsigned short);
9621
int vec_any_lt (vector bool short, vector signed short);
9622
int vec_any_lt (vector signed short, vector bool short);
9623
int vec_any_lt (vector signed short, vector signed short);
9624
int vec_any_lt (vector bool int, vector unsigned int);
9625
int vec_any_lt (vector unsigned int, vector bool int);
9626
int vec_any_lt (vector unsigned int, vector unsigned int);
9627
int vec_any_lt (vector bool int, vector signed int);
9628
int vec_any_lt (vector signed int, vector bool int);
9629
int vec_any_lt (vector signed int, vector signed int);
9630
int vec_any_lt (vector float, vector float);
9631
 
9632
int vec_any_nan (vector float);
9633
 
9634
int vec_any_ne (vector signed char, vector bool char);
9635
int vec_any_ne (vector signed char, vector signed char);
9636
int vec_any_ne (vector unsigned char, vector bool char);
9637
int vec_any_ne (vector unsigned char, vector unsigned char);
9638
int vec_any_ne (vector bool char, vector bool char);
9639
int vec_any_ne (vector bool char, vector unsigned char);
9640
int vec_any_ne (vector bool char, vector signed char);
9641
int vec_any_ne (vector signed short, vector bool short);
9642
int vec_any_ne (vector signed short, vector signed short);
9643
int vec_any_ne (vector unsigned short, vector bool short);
9644
int vec_any_ne (vector unsigned short, vector unsigned short);
9645
int vec_any_ne (vector bool short, vector bool short);
9646
int vec_any_ne (vector bool short, vector unsigned short);
9647
int vec_any_ne (vector bool short, vector signed short);
9648
int vec_any_ne (vector pixel, vector pixel);
9649
int vec_any_ne (vector signed int, vector bool int);
9650
int vec_any_ne (vector signed int, vector signed int);
9651
int vec_any_ne (vector unsigned int, vector bool int);
9652
int vec_any_ne (vector unsigned int, vector unsigned int);
9653
int vec_any_ne (vector bool int, vector bool int);
9654
int vec_any_ne (vector bool int, vector unsigned int);
9655
int vec_any_ne (vector bool int, vector signed int);
9656
int vec_any_ne (vector float, vector float);
9657
 
9658
int vec_any_nge (vector float, vector float);
9659
 
9660
int vec_any_ngt (vector float, vector float);
9661
 
9662
int vec_any_nle (vector float, vector float);
9663
 
9664
int vec_any_nlt (vector float, vector float);
9665
 
9666
int vec_any_numeric (vector float);
9667
 
9668
int vec_any_out (vector float, vector float);
9669
@end smallexample
9670
 
9671
@node SPARC VIS Built-in Functions
9672
@subsection SPARC VIS Built-in Functions
9673
 
9674
GCC supports SIMD operations on the SPARC using both the generic vector
9675
extensions (@pxref{Vector Extensions}) as well as built-in functions for
9676
the SPARC Visual Instruction Set (VIS).  When you use the @option{-mvis}
9677
switch, the VIS extension is exposed as the following built-in functions:
9678
 
9679
@smallexample
9680
typedef int v2si __attribute__ ((vector_size (8)));
9681
typedef short v4hi __attribute__ ((vector_size (8)));
9682
typedef short v2hi __attribute__ ((vector_size (4)));
9683
typedef char v8qi __attribute__ ((vector_size (8)));
9684
typedef char v4qi __attribute__ ((vector_size (4)));
9685
 
9686
void * __builtin_vis_alignaddr (void *, long);
9687
int64_t __builtin_vis_faligndatadi (int64_t, int64_t);
9688
v2si __builtin_vis_faligndatav2si (v2si, v2si);
9689
v4hi __builtin_vis_faligndatav4hi (v4si, v4si);
9690
v8qi __builtin_vis_faligndatav8qi (v8qi, v8qi);
9691
 
9692
v4hi __builtin_vis_fexpand (v4qi);
9693
 
9694
v4hi __builtin_vis_fmul8x16 (v4qi, v4hi);
9695
v4hi __builtin_vis_fmul8x16au (v4qi, v4hi);
9696
v4hi __builtin_vis_fmul8x16al (v4qi, v4hi);
9697
v4hi __builtin_vis_fmul8sux16 (v8qi, v4hi);
9698
v4hi __builtin_vis_fmul8ulx16 (v8qi, v4hi);
9699
v2si __builtin_vis_fmuld8sux16 (v4qi, v2hi);
9700
v2si __builtin_vis_fmuld8ulx16 (v4qi, v2hi);
9701
 
9702
v4qi __builtin_vis_fpack16 (v4hi);
9703
v8qi __builtin_vis_fpack32 (v2si, v2si);
9704
v2hi __builtin_vis_fpackfix (v2si);
9705
v8qi __builtin_vis_fpmerge (v4qi, v4qi);
9706
 
9707
int64_t __builtin_vis_pdist (v8qi, v8qi, int64_t);
9708
@end smallexample
9709
 
9710
@node Target Format Checks
9711
@section Format Checks Specific to Particular Target Machines
9712
 
9713
For some target machines, GCC supports additional options to the
9714
format attribute
9715
(@pxref{Function Attributes,,Declaring Attributes of Functions}).
9716
 
9717
@menu
9718
* Solaris Format Checks::
9719
@end menu
9720
 
9721
@node Solaris Format Checks
9722
@subsection Solaris Format Checks
9723
 
9724
Solaris targets support the @code{cmn_err} (or @code{__cmn_err__}) format
9725
check.  @code{cmn_err} accepts a subset of the standard @code{printf}
9726
conversions, and the two-argument @code{%b} conversion for displaying
9727
bit-fields.  See the Solaris man page for @code{cmn_err} for more information.
9728
 
9729
@node Pragmas
9730
@section Pragmas Accepted by GCC
9731
@cindex pragmas
9732
@cindex #pragma
9733
 
9734
GCC supports several types of pragmas, primarily in order to compile
9735
code originally written for other compilers.  Note that in general
9736
we do not recommend the use of pragmas; @xref{Function Attributes},
9737
for further explanation.
9738
 
9739
@menu
9740
* ARM Pragmas::
9741
* M32C Pragmas::
9742
* RS/6000 and PowerPC Pragmas::
9743
* Darwin Pragmas::
9744
* Solaris Pragmas::
9745
* Symbol-Renaming Pragmas::
9746
* Structure-Packing Pragmas::
9747
* Weak Pragmas::
9748
* Diagnostic Pragmas::
9749
* Visibility Pragmas::
9750
@end menu
9751
 
9752
@node ARM Pragmas
9753
@subsection ARM Pragmas
9754
 
9755
The ARM target defines pragmas for controlling the default addition of
9756
@code{long_call} and @code{short_call} attributes to functions.
9757
@xref{Function Attributes}, for information about the effects of these
9758
attributes.
9759
 
9760
@table @code
9761
@item long_calls
9762
@cindex pragma, long_calls
9763
Set all subsequent functions to have the @code{long_call} attribute.
9764
 
9765
@item no_long_calls
9766
@cindex pragma, no_long_calls
9767
Set all subsequent functions to have the @code{short_call} attribute.
9768
 
9769
@item long_calls_off
9770
@cindex pragma, long_calls_off
9771
Do not affect the @code{long_call} or @code{short_call} attributes of
9772
subsequent functions.
9773
@end table
9774
 
9775
@node M32C Pragmas
9776
@subsection M32C Pragmas
9777
 
9778
@table @code
9779
@item memregs @var{number}
9780
@cindex pragma, memregs
9781
Overrides the command line option @code{-memregs=} for the current
9782
file.  Use with care!  This pragma must be before any function in the
9783
file, and mixing different memregs values in different objects may
9784
make them incompatible.  This pragma is useful when a
9785
performance-critical function uses a memreg for temporary values,
9786
as it may allow you to reduce the number of memregs used.
9787
 
9788
@end table
9789
 
9790
@node RS/6000 and PowerPC Pragmas
9791
@subsection RS/6000 and PowerPC Pragmas
9792
 
9793
The RS/6000 and PowerPC targets define one pragma for controlling
9794
whether or not the @code{longcall} attribute is added to function
9795
declarations by default.  This pragma overrides the @option{-mlongcall}
9796
option, but not the @code{longcall} and @code{shortcall} attributes.
9797
@xref{RS/6000 and PowerPC Options}, for more information about when long
9798
calls are and are not necessary.
9799
 
9800
@table @code
9801
@item longcall (1)
9802
@cindex pragma, longcall
9803
Apply the @code{longcall} attribute to all subsequent function
9804
declarations.
9805
 
9806
@item longcall (0)
9807
Do not apply the @code{longcall} attribute to subsequent function
9808
declarations.
9809
@end table
9810
 
9811
@c Describe c4x pragmas here.
9812
@c Describe h8300 pragmas here.
9813
@c Describe sh pragmas here.
9814
@c Describe v850 pragmas here.
9815
 
9816
@node Darwin Pragmas
9817
@subsection Darwin Pragmas
9818
 
9819
The following pragmas are available for all architectures running the
9820
Darwin operating system.  These are useful for compatibility with other
9821
Mac OS compilers.
9822
 
9823
@table @code
9824
@item mark @var{tokens}@dots{}
9825
@cindex pragma, mark
9826
This pragma is accepted, but has no effect.
9827
 
9828
@item options align=@var{alignment}
9829
@cindex pragma, options align
9830
This pragma sets the alignment of fields in structures.  The values of
9831
@var{alignment} may be @code{mac68k}, to emulate m68k alignment, or
9832
@code{power}, to emulate PowerPC alignment.  Uses of this pragma nest
9833
properly; to restore the previous setting, use @code{reset} for the
9834
@var{alignment}.
9835
 
9836
@item segment @var{tokens}@dots{}
9837
@cindex pragma, segment
9838
This pragma is accepted, but has no effect.
9839
 
9840
@item unused (@var{var} [, @var{var}]@dots{})
9841
@cindex pragma, unused
9842
This pragma declares variables to be possibly unused.  GCC will not
9843
produce warnings for the listed variables.  The effect is similar to
9844
that of the @code{unused} attribute, except that this pragma may appear
9845
anywhere within the variables' scopes.
9846
@end table
9847
 
9848
@node Solaris Pragmas
9849
@subsection Solaris Pragmas
9850
 
9851
The Solaris target supports @code{#pragma redefine_extname}
9852
(@pxref{Symbol-Renaming Pragmas}).  It also supports additional
9853
@code{#pragma} directives for compatibility with the system compiler.
9854
 
9855
@table @code
9856
@item align @var{alignment} (@var{variable} [, @var{variable}]...)
9857
@cindex pragma, align
9858
 
9859
Increase the minimum alignment of each @var{variable} to @var{alignment}.
9860
This is the same as GCC's @code{aligned} attribute @pxref{Variable
9861
Attributes}).  Macro expansion occurs on the arguments to this pragma
9862
when compiling C and Objective-C.  It does not currently occur when
9863
compiling C++, but this is a bug which may be fixed in a future
9864
release.
9865
 
9866
@item fini (@var{function} [, @var{function}]...)
9867
@cindex pragma, fini
9868
 
9869
This pragma causes each listed @var{function} to be called after
9870
main, or during shared module unloading, by adding a call to the
9871
@code{.fini} section.
9872
 
9873
@item init (@var{function} [, @var{function}]...)
9874
@cindex pragma, init
9875
 
9876
This pragma causes each listed @var{function} to be called during
9877
initialization (before @code{main}) or during shared module loading, by
9878
adding a call to the @code{.init} section.
9879
 
9880
@end table
9881
 
9882
@node Symbol-Renaming Pragmas
9883
@subsection Symbol-Renaming Pragmas
9884
 
9885
For compatibility with the Solaris and Tru64 UNIX system headers, GCC
9886
supports two @code{#pragma} directives which change the name used in
9887
assembly for a given declaration.  These pragmas are only available on
9888
platforms whose system headers need them.  To get this effect on all
9889
platforms supported by GCC, use the asm labels extension (@pxref{Asm
9890
Labels}).
9891
 
9892
@table @code
9893
@item redefine_extname @var{oldname} @var{newname}
9894
@cindex pragma, redefine_extname
9895
 
9896
This pragma gives the C function @var{oldname} the assembly symbol
9897
@var{newname}.  The preprocessor macro @code{__PRAGMA_REDEFINE_EXTNAME}
9898
will be defined if this pragma is available (currently only on
9899
Solaris).
9900
 
9901
@item extern_prefix @var{string}
9902
@cindex pragma, extern_prefix
9903
 
9904
This pragma causes all subsequent external function and variable
9905
declarations to have @var{string} prepended to their assembly symbols.
9906
This effect may be terminated with another @code{extern_prefix} pragma
9907
whose argument is an empty string.  The preprocessor macro
9908
@code{__PRAGMA_EXTERN_PREFIX} will be defined if this pragma is
9909
available (currently only on Tru64 UNIX)@.
9910
@end table
9911
 
9912
These pragmas and the asm labels extension interact in a complicated
9913
manner.  Here are some corner cases you may want to be aware of.
9914
 
9915
@enumerate
9916
@item Both pragmas silently apply only to declarations with external
9917
linkage.  Asm labels do not have this restriction.
9918
 
9919
@item In C++, both pragmas silently apply only to declarations with
9920
``C'' linkage.  Again, asm labels do not have this restriction.
9921
 
9922
@item If any of the three ways of changing the assembly name of a
9923
declaration is applied to a declaration whose assembly name has
9924
already been determined (either by a previous use of one of these
9925
features, or because the compiler needed the assembly name in order to
9926
generate code), and the new name is different, a warning issues and
9927
the name does not change.
9928
 
9929
@item The @var{oldname} used by @code{#pragma redefine_extname} is
9930
always the C-language name.
9931
 
9932
@item If @code{#pragma extern_prefix} is in effect, and a declaration
9933
occurs with an asm label attached, the prefix is silently ignored for
9934
that declaration.
9935
 
9936
@item If @code{#pragma extern_prefix} and @code{#pragma redefine_extname}
9937
apply to the same declaration, whichever triggered first wins, and a
9938
warning issues if they contradict each other.  (We would like to have
9939
@code{#pragma redefine_extname} always win, for consistency with asm
9940
labels, but if @code{#pragma extern_prefix} triggers first we have no
9941
way of knowing that that happened.)
9942
@end enumerate
9943
 
9944
@node Structure-Packing Pragmas
9945
@subsection Structure-Packing Pragmas
9946
 
9947
For compatibility with Win32, GCC supports a set of @code{#pragma}
9948
directives which change the maximum alignment of members of structures
9949
(other than zero-width bitfields), unions, and classes subsequently
9950
defined.  The @var{n} value below always is required to be a small power
9951
of two and specifies the new alignment in bytes.
9952
 
9953
@enumerate
9954
@item @code{#pragma pack(@var{n})} simply sets the new alignment.
9955
@item @code{#pragma pack()} sets the alignment to the one that was in
9956
effect when compilation started (see also command line option
9957
@option{-fpack-struct[=<n>]} @pxref{Code Gen Options}).
9958
@item @code{#pragma pack(push[,@var{n}])} pushes the current alignment
9959
setting on an internal stack and then optionally sets the new alignment.
9960
@item @code{#pragma pack(pop)} restores the alignment setting to the one
9961
saved at the top of the internal stack (and removes that stack entry).
9962
Note that @code{#pragma pack([@var{n}])} does not influence this internal
9963
stack; thus it is possible to have @code{#pragma pack(push)} followed by
9964
multiple @code{#pragma pack(@var{n})} instances and finalized by a single
9965
@code{#pragma pack(pop)}.
9966
@end enumerate
9967
 
9968
Some targets, e.g. i386 and powerpc, support the @code{ms_struct}
9969
@code{#pragma} which lays out a structure as the documented
9970
@code{__attribute__ ((ms_struct))}.
9971
@enumerate
9972
@item @code{#pragma ms_struct on} turns on the layout for structures
9973
declared.
9974
@item @code{#pragma ms_struct off} turns off the layout for structures
9975
declared.
9976
@item @code{#pragma ms_struct reset} goes back to the default layout.
9977
@end enumerate
9978
 
9979
@node Weak Pragmas
9980
@subsection Weak Pragmas
9981
 
9982
For compatibility with SVR4, GCC supports a set of @code{#pragma}
9983
directives for declaring symbols to be weak, and defining weak
9984
aliases.
9985
 
9986
@table @code
9987
@item #pragma weak @var{symbol}
9988
@cindex pragma, weak
9989
This pragma declares @var{symbol} to be weak, as if the declaration
9990
had the attribute of the same name.  The pragma may appear before
9991
or after the declaration of @var{symbol}, but must appear before
9992
either its first use or its definition.  It is not an error for
9993
@var{symbol} to never be defined at all.
9994
 
9995
@item #pragma weak @var{symbol1} = @var{symbol2}
9996
This pragma declares @var{symbol1} to be a weak alias of @var{symbol2}.
9997
It is an error if @var{symbol2} is not defined in the current
9998
translation unit.
9999
@end table
10000
 
10001
@node Diagnostic Pragmas
10002
@subsection Diagnostic Pragmas
10003
 
10004
GCC allows the user to selectively enable or disable certain types of
10005
diagnostics, and change the kind of the diagnostic.  For example, a
10006
project's policy might require that all sources compile with
10007
@option{-Werror} but certain files might have exceptions allowing
10008
specific types of warnings.  Or, a project might selectively enable
10009
diagnostics and treat them as errors depending on which preprocessor
10010
macros are defined.
10011
 
10012
@table @code
10013
@item #pragma GCC diagnostic @var{kind} @var{option}
10014
@cindex pragma, diagnostic
10015
 
10016
Modifies the disposition of a diagnostic.  Note that not all
10017
diagnostics are modifiable; at the moment only warnings (normally
10018
controlled by @samp{-W...}) can be controlled, and not all of them.
10019
Use @option{-fdiagnostics-show-option} to determine which diagnostics
10020
are controllable and which option controls them.
10021
 
10022
@var{kind} is @samp{error} to treat this diagnostic as an error,
10023
@samp{warning} to treat it like a warning (even if @option{-Werror} is
10024
in effect), or @samp{ignored} if the diagnostic is to be ignored.
10025
@var{option} is a double quoted string which matches the command line
10026
option.
10027
 
10028
@example
10029
#pragma GCC diagnostic warning "-Wformat"
10030
#pragma GCC diagnostic error "-Wformat"
10031
#pragma GCC diagnostic ignored "-Wformat"
10032
@end example
10033
 
10034
Note that these pragmas override any command line options.  Also,
10035
while it is syntactically valid to put these pragmas anywhere in your
10036
sources, the only supported location for them is before any data or
10037
functions are defined.  Doing otherwise may result in unpredictable
10038
results depending on how the optimizer manages your sources.  If the
10039
same option is listed multiple times, the last one specified is the
10040
one that is in effect.  This pragma is not intended to be a general
10041
purpose replacement for command line options, but for implementing
10042
strict control over project policies.
10043
 
10044
@end table
10045
 
10046
@node Visibility Pragmas
10047
@subsection Visibility Pragmas
10048
 
10049
@table @code
10050
@item #pragma GCC visibility push(@var{visibility})
10051
@itemx #pragma GCC visibility pop
10052
@cindex pragma, visibility
10053
 
10054
This pragma allows the user to set the visibility for multiple
10055
declarations without having to give each a visibility attribute
10056
@xref{Function Attributes}, for more information about visibility and
10057
the attribute syntax.
10058
 
10059
In C++, @samp{#pragma GCC visibility} affects only namespace-scope
10060
declarations.  Class members and template specializations are not
10061
affected; if you want to override the visibility for a particular
10062
member or instantiation, you must use an attribute.
10063
 
10064
@end table
10065
 
10066
@node Unnamed Fields
10067
@section Unnamed struct/union fields within structs/unions
10068
@cindex struct
10069
@cindex union
10070
 
10071
For compatibility with other compilers, GCC allows you to define
10072
a structure or union that contains, as fields, structures and unions
10073
without names.  For example:
10074
 
10075
@smallexample
10076
struct @{
10077
  int a;
10078
  union @{
10079
    int b;
10080
    float c;
10081
  @};
10082
  int d;
10083
@} foo;
10084
@end smallexample
10085
 
10086
In this example, the user would be able to access members of the unnamed
10087
union with code like @samp{foo.b}.  Note that only unnamed structs and
10088
unions are allowed, you may not have, for example, an unnamed
10089
@code{int}.
10090
 
10091
You must never create such structures that cause ambiguous field definitions.
10092
For example, this structure:
10093
 
10094
@smallexample
10095
struct @{
10096
  int a;
10097
  struct @{
10098
    int a;
10099
  @};
10100
@} foo;
10101
@end smallexample
10102
 
10103
It is ambiguous which @code{a} is being referred to with @samp{foo.a}.
10104
Such constructs are not supported and must be avoided.  In the future,
10105
such constructs may be detected and treated as compilation errors.
10106
 
10107
@opindex fms-extensions
10108
Unless @option{-fms-extensions} is used, the unnamed field must be a
10109
structure or union definition without a tag (for example, @samp{struct
10110
@{ int a; @};}).  If @option{-fms-extensions} is used, the field may
10111
also be a definition with a tag such as @samp{struct foo @{ int a;
10112
@};}, a reference to a previously defined structure or union such as
10113
@samp{struct foo;}, or a reference to a @code{typedef} name for a
10114
previously defined structure or union type.
10115
 
10116
@node Thread-Local
10117
@section Thread-Local Storage
10118
@cindex Thread-Local Storage
10119
@cindex @acronym{TLS}
10120
@cindex __thread
10121
 
10122
Thread-local storage (@acronym{TLS}) is a mechanism by which variables
10123
are allocated such that there is one instance of the variable per extant
10124
thread.  The run-time model GCC uses to implement this originates
10125
in the IA-64 processor-specific ABI, but has since been migrated
10126
to other processors as well.  It requires significant support from
10127
the linker (@command{ld}), dynamic linker (@command{ld.so}), and
10128
system libraries (@file{libc.so} and @file{libpthread.so}), so it
10129
is not available everywhere.
10130
 
10131
At the user level, the extension is visible with a new storage
10132
class keyword: @code{__thread}.  For example:
10133
 
10134
@smallexample
10135
__thread int i;
10136
extern __thread struct state s;
10137
static __thread char *p;
10138
@end smallexample
10139
 
10140
The @code{__thread} specifier may be used alone, with the @code{extern}
10141
or @code{static} specifiers, but with no other storage class specifier.
10142
When used with @code{extern} or @code{static}, @code{__thread} must appear
10143
immediately after the other storage class specifier.
10144
 
10145
The @code{__thread} specifier may be applied to any global, file-scoped
10146
static, function-scoped static, or static data member of a class.  It may
10147
not be applied to block-scoped automatic or non-static data member.
10148
 
10149
When the address-of operator is applied to a thread-local variable, it is
10150
evaluated at run-time and returns the address of the current thread's
10151
instance of that variable.  An address so obtained may be used by any
10152
thread.  When a thread terminates, any pointers to thread-local variables
10153
in that thread become invalid.
10154
 
10155
No static initialization may refer to the address of a thread-local variable.
10156
 
10157
In C++, if an initializer is present for a thread-local variable, it must
10158
be a @var{constant-expression}, as defined in 5.19.2 of the ANSI/ISO C++
10159
standard.
10160
 
10161
See @uref{http://people.redhat.com/drepper/tls.pdf,
10162
ELF Handling For Thread-Local Storage} for a detailed explanation of
10163
the four thread-local storage addressing models, and how the run-time
10164
is expected to function.
10165
 
10166
@menu
10167
* C99 Thread-Local Edits::
10168
* C++98 Thread-Local Edits::
10169
@end menu
10170
 
10171
@node C99 Thread-Local Edits
10172
@subsection ISO/IEC 9899:1999 Edits for Thread-Local Storage
10173
 
10174
The following are a set of changes to ISO/IEC 9899:1999 (aka C99)
10175
that document the exact semantics of the language extension.
10176
 
10177
@itemize @bullet
10178
@item
10179
@cite{5.1.2  Execution environments}
10180
 
10181
Add new text after paragraph 1
10182
 
10183
@quotation
10184
Within either execution environment, a @dfn{thread} is a flow of
10185
control within a program.  It is implementation defined whether
10186
or not there may be more than one thread associated with a program.
10187
It is implementation defined how threads beyond the first are
10188
created, the name and type of the function called at thread
10189
startup, and how threads may be terminated.  However, objects
10190
with thread storage duration shall be initialized before thread
10191
startup.
10192
@end quotation
10193
 
10194
@item
10195
@cite{6.2.4  Storage durations of objects}
10196
 
10197
Add new text before paragraph 3
10198
 
10199
@quotation
10200
An object whose identifier is declared with the storage-class
10201
specifier @w{@code{__thread}} has @dfn{thread storage duration}.
10202
Its lifetime is the entire execution of the thread, and its
10203
stored value is initialized only once, prior to thread startup.
10204
@end quotation
10205
 
10206
@item
10207
@cite{6.4.1  Keywords}
10208
 
10209
Add @code{__thread}.
10210
 
10211
@item
10212
@cite{6.7.1  Storage-class specifiers}
10213
 
10214
Add @code{__thread} to the list of storage class specifiers in
10215
paragraph 1.
10216
 
10217
Change paragraph 2 to
10218
 
10219
@quotation
10220
With the exception of @code{__thread}, at most one storage-class
10221
specifier may be given [@dots{}].  The @code{__thread} specifier may
10222
be used alone, or immediately following @code{extern} or
10223
@code{static}.
10224
@end quotation
10225
 
10226
Add new text after paragraph 6
10227
 
10228
@quotation
10229
The declaration of an identifier for a variable that has
10230
block scope that specifies @code{__thread} shall also
10231
specify either @code{extern} or @code{static}.
10232
 
10233
The @code{__thread} specifier shall be used only with
10234
variables.
10235
@end quotation
10236
@end itemize
10237
 
10238
@node C++98 Thread-Local Edits
10239
@subsection ISO/IEC 14882:1998 Edits for Thread-Local Storage
10240
 
10241
The following are a set of changes to ISO/IEC 14882:1998 (aka C++98)
10242
that document the exact semantics of the language extension.
10243
 
10244
@itemize @bullet
10245
@item
10246
@b{[intro.execution]}
10247
 
10248
New text after paragraph 4
10249
 
10250
@quotation
10251
A @dfn{thread} is a flow of control within the abstract machine.
10252
It is implementation defined whether or not there may be more than
10253
one thread.
10254
@end quotation
10255
 
10256
New text after paragraph 7
10257
 
10258
@quotation
10259
It is unspecified whether additional action must be taken to
10260
ensure when and whether side effects are visible to other threads.
10261
@end quotation
10262
 
10263
@item
10264
@b{[lex.key]}
10265
 
10266
Add @code{__thread}.
10267
 
10268
@item
10269
@b{[basic.start.main]}
10270
 
10271
Add after paragraph 5
10272
 
10273
@quotation
10274
The thread that begins execution at the @code{main} function is called
10275
the @dfn{main thread}.  It is implementation defined how functions
10276
beginning threads other than the main thread are designated or typed.
10277
A function so designated, as well as the @code{main} function, is called
10278
a @dfn{thread startup function}.  It is implementation defined what
10279
happens if a thread startup function returns.  It is implementation
10280
defined what happens to other threads when any thread calls @code{exit}.
10281
@end quotation
10282
 
10283
@item
10284
@b{[basic.start.init]}
10285
 
10286
Add after paragraph 4
10287
 
10288
@quotation
10289
The storage for an object of thread storage duration shall be
10290
statically initialized before the first statement of the thread startup
10291
function.  An object of thread storage duration shall not require
10292
dynamic initialization.
10293
@end quotation
10294
 
10295
@item
10296
@b{[basic.start.term]}
10297
 
10298
Add after paragraph 3
10299
 
10300
@quotation
10301
The type of an object with thread storage duration shall not have a
10302
non-trivial destructor, nor shall it be an array type whose elements
10303
(directly or indirectly) have non-trivial destructors.
10304
@end quotation
10305
 
10306
@item
10307
@b{[basic.stc]}
10308
 
10309
Add ``thread storage duration'' to the list in paragraph 1.
10310
 
10311
Change paragraph 2
10312
 
10313
@quotation
10314
Thread, static, and automatic storage durations are associated with
10315
objects introduced by declarations [@dots{}].
10316
@end quotation
10317
 
10318
Add @code{__thread} to the list of specifiers in paragraph 3.
10319
 
10320
@item
10321
@b{[basic.stc.thread]}
10322
 
10323
New section before @b{[basic.stc.static]}
10324
 
10325
@quotation
10326
The keyword @code{__thread} applied to a non-local object gives the
10327
object thread storage duration.
10328
 
10329
A local variable or class data member declared both @code{static}
10330
and @code{__thread} gives the variable or member thread storage
10331
duration.
10332
@end quotation
10333
 
10334
@item
10335
@b{[basic.stc.static]}
10336
 
10337
Change paragraph 1
10338
 
10339
@quotation
10340
All objects which have neither thread storage duration, dynamic
10341
storage duration nor are local [@dots{}].
10342
@end quotation
10343
 
10344
@item
10345
@b{[dcl.stc]}
10346
 
10347
Add @code{__thread} to the list in paragraph 1.
10348
 
10349
Change paragraph 1
10350
 
10351
@quotation
10352
With the exception of @code{__thread}, at most one
10353
@var{storage-class-specifier} shall appear in a given
10354
@var{decl-specifier-seq}.  The @code{__thread} specifier may
10355
be used alone, or immediately following the @code{extern} or
10356
@code{static} specifiers.  [@dots{}]
10357
@end quotation
10358
 
10359
Add after paragraph 5
10360
 
10361
@quotation
10362
The @code{__thread} specifier can be applied only to the names of objects
10363
and to anonymous unions.
10364
@end quotation
10365
 
10366
@item
10367
@b{[class.mem]}
10368
 
10369
Add after paragraph 6
10370
 
10371
@quotation
10372
Non-@code{static} members shall not be @code{__thread}.
10373
@end quotation
10374
@end itemize
10375
 
10376
@node C++ Extensions
10377
@chapter Extensions to the C++ Language
10378
@cindex extensions, C++ language
10379
@cindex C++ language extensions
10380
 
10381
The GNU compiler provides these extensions to the C++ language (and you
10382
can also use most of the C language extensions in your C++ programs).  If you
10383
want to write code that checks whether these features are available, you can
10384
test for the GNU compiler the same way as for C programs: check for a
10385
predefined macro @code{__GNUC__}.  You can also use @code{__GNUG__} to
10386
test specifically for GNU C++ (@pxref{Common Predefined Macros,,
10387
Predefined Macros,cpp,The GNU C Preprocessor}).
10388
 
10389
@menu
10390
* Volatiles::           What constitutes an access to a volatile object.
10391
* Restricted Pointers:: C99 restricted pointers and references.
10392
* Vague Linkage::       Where G++ puts inlines, vtables and such.
10393
* C++ Interface::       You can use a single C++ header file for both
10394
                        declarations and definitions.
10395
* Template Instantiation:: Methods for ensuring that exactly one copy of
10396
                        each needed template instantiation is emitted.
10397
* Bound member functions:: You can extract a function pointer to the
10398
                        method denoted by a @samp{->*} or @samp{.*} expression.
10399
* C++ Attributes::      Variable, function, and type attributes for C++ only.
10400
* Namespace Association:: Strong using-directives for namespace association.
10401
* Java Exceptions::     Tweaking exception handling to work with Java.
10402
* Deprecated Features:: Things will disappear from g++.
10403
* Backwards Compatibility:: Compatibilities with earlier definitions of C++.
10404
@end menu
10405
 
10406
@node Volatiles
10407
@section When is a Volatile Object Accessed?
10408
@cindex accessing volatiles
10409
@cindex volatile read
10410
@cindex volatile write
10411
@cindex volatile access
10412
 
10413
Both the C and C++ standard have the concept of volatile objects.  These
10414
are normally accessed by pointers and used for accessing hardware.  The
10415
standards encourage compilers to refrain from optimizations concerning
10416
accesses to volatile objects.  The C standard leaves it implementation
10417
defined  as to what constitutes a volatile access.  The C++ standard omits
10418
to specify this, except to say that C++ should behave in a similar manner
10419
to C with respect to volatiles, where possible.  The minimum either
10420
standard specifies is that at a sequence point all previous accesses to
10421
volatile objects have stabilized and no subsequent accesses have
10422
occurred.  Thus an implementation is free to reorder and combine
10423
volatile accesses which occur between sequence points, but cannot do so
10424
for accesses across a sequence point.  The use of volatiles does not
10425
allow you to violate the restriction on updating objects multiple times
10426
within a sequence point.
10427
 
10428
@xref{Qualifiers implementation, , Volatile qualifier and the C compiler}.
10429
 
10430
The behavior differs slightly between C and C++ in the non-obvious cases:
10431
 
10432
@smallexample
10433
volatile int *src = @var{somevalue};
10434
*src;
10435
@end smallexample
10436
 
10437
With C, such expressions are rvalues, and GCC interprets this either as a
10438
read of the volatile object being pointed to or only as request to evaluate
10439
the side-effects.  The C++ standard specifies that such expressions do not
10440
undergo lvalue to rvalue conversion, and that the type of the dereferenced
10441
object may be incomplete.  The C++ standard does not specify explicitly
10442
that it is this lvalue to rvalue conversion which may be responsible for
10443
causing an access.  However, there is reason to believe that it is,
10444
because otherwise certain simple expressions become undefined.  However,
10445
because it would surprise most programmers, G++ treats dereferencing a
10446
pointer to volatile object of complete type when the value is unused as
10447
GCC would do for an equivalent type in C.  When the object has incomplete
10448
type, G++ issues a warning; if you wish to force an error, you must
10449
force a conversion to rvalue with, for instance, a static cast.
10450
 
10451
When using a reference to volatile, G++ does not treat equivalent
10452
expressions as accesses to volatiles, but instead issues a warning that
10453
no volatile is accessed.  The rationale for this is that otherwise it
10454
becomes difficult to determine where volatile access occur, and not
10455
possible to ignore the return value from functions returning volatile
10456
references.  Again, if you wish to force a read, cast the reference to
10457
an rvalue.
10458
 
10459
@node Restricted Pointers
10460
@section Restricting Pointer Aliasing
10461
@cindex restricted pointers
10462
@cindex restricted references
10463
@cindex restricted this pointer
10464
 
10465
As with the C front end, G++ understands the C99 feature of restricted pointers,
10466
specified with the @code{__restrict__}, or @code{__restrict} type
10467
qualifier.  Because you cannot compile C++ by specifying the @option{-std=c99}
10468
language flag, @code{restrict} is not a keyword in C++.
10469
 
10470
In addition to allowing restricted pointers, you can specify restricted
10471
references, which indicate that the reference is not aliased in the local
10472
context.
10473
 
10474
@smallexample
10475
void fn (int *__restrict__ rptr, int &__restrict__ rref)
10476
@{
10477
  /* @r{@dots{}} */
10478
@}
10479
@end smallexample
10480
 
10481
@noindent
10482
In the body of @code{fn}, @var{rptr} points to an unaliased integer and
10483
@var{rref} refers to a (different) unaliased integer.
10484
 
10485
You may also specify whether a member function's @var{this} pointer is
10486
unaliased by using @code{__restrict__} as a member function qualifier.
10487
 
10488
@smallexample
10489
void T::fn () __restrict__
10490
@{
10491
  /* @r{@dots{}} */
10492
@}
10493
@end smallexample
10494
 
10495
@noindent
10496
Within the body of @code{T::fn}, @var{this} will have the effective
10497
definition @code{T *__restrict__ const this}.  Notice that the
10498
interpretation of a @code{__restrict__} member function qualifier is
10499
different to that of @code{const} or @code{volatile} qualifier, in that it
10500
is applied to the pointer rather than the object.  This is consistent with
10501
other compilers which implement restricted pointers.
10502
 
10503
As with all outermost parameter qualifiers, @code{__restrict__} is
10504
ignored in function definition matching.  This means you only need to
10505
specify @code{__restrict__} in a function definition, rather than
10506
in a function prototype as well.
10507
 
10508
@node Vague Linkage
10509
@section Vague Linkage
10510
@cindex vague linkage
10511
 
10512
There are several constructs in C++ which require space in the object
10513
file but are not clearly tied to a single translation unit.  We say that
10514
these constructs have ``vague linkage''.  Typically such constructs are
10515
emitted wherever they are needed, though sometimes we can be more
10516
clever.
10517
 
10518
@table @asis
10519
@item Inline Functions
10520
Inline functions are typically defined in a header file which can be
10521
included in many different compilations.  Hopefully they can usually be
10522
inlined, but sometimes an out-of-line copy is necessary, if the address
10523
of the function is taken or if inlining fails.  In general, we emit an
10524
out-of-line copy in all translation units where one is needed.  As an
10525
exception, we only emit inline virtual functions with the vtable, since
10526
it will always require a copy.
10527
 
10528
Local static variables and string constants used in an inline function
10529
are also considered to have vague linkage, since they must be shared
10530
between all inlined and out-of-line instances of the function.
10531
 
10532
@item VTables
10533
@cindex vtable
10534
C++ virtual functions are implemented in most compilers using a lookup
10535
table, known as a vtable.  The vtable contains pointers to the virtual
10536
functions provided by a class, and each object of the class contains a
10537
pointer to its vtable (or vtables, in some multiple-inheritance
10538
situations).  If the class declares any non-inline, non-pure virtual
10539
functions, the first one is chosen as the ``key method'' for the class,
10540
and the vtable is only emitted in the translation unit where the key
10541
method is defined.
10542
 
10543
@emph{Note:} If the chosen key method is later defined as inline, the
10544
vtable will still be emitted in every translation unit which defines it.
10545
Make sure that any inline virtuals are declared inline in the class
10546
body, even if they are not defined there.
10547
 
10548
@item type_info objects
10549
@cindex type_info
10550
@cindex RTTI
10551
C++ requires information about types to be written out in order to
10552
implement @samp{dynamic_cast}, @samp{typeid} and exception handling.
10553
For polymorphic classes (classes with virtual functions), the type_info
10554
object is written out along with the vtable so that @samp{dynamic_cast}
10555
can determine the dynamic type of a class object at runtime.  For all
10556
other types, we write out the type_info object when it is used: when
10557
applying @samp{typeid} to an expression, throwing an object, or
10558
referring to a type in a catch clause or exception specification.
10559
 
10560
@item Template Instantiations
10561
Most everything in this section also applies to template instantiations,
10562
but there are other options as well.
10563
@xref{Template Instantiation,,Where's the Template?}.
10564
 
10565
@end table
10566
 
10567
When used with GNU ld version 2.8 or later on an ELF system such as
10568
GNU/Linux or Solaris 2, or on Microsoft Windows, duplicate copies of
10569
these constructs will be discarded at link time.  This is known as
10570
COMDAT support.
10571
 
10572
On targets that don't support COMDAT, but do support weak symbols, GCC
10573
will use them.  This way one copy will override all the others, but
10574
the unused copies will still take up space in the executable.
10575
 
10576
For targets which do not support either COMDAT or weak symbols,
10577
most entities with vague linkage will be emitted as local symbols to
10578
avoid duplicate definition errors from the linker.  This will not happen
10579
for local statics in inlines, however, as having multiple copies will
10580
almost certainly break things.
10581
 
10582
@xref{C++ Interface,,Declarations and Definitions in One Header}, for
10583
another way to control placement of these constructs.
10584
 
10585
@node C++ Interface
10586
@section #pragma interface and implementation
10587
 
10588
@cindex interface and implementation headers, C++
10589
@cindex C++ interface and implementation headers
10590
@cindex pragmas, interface and implementation
10591
 
10592
@code{#pragma interface} and @code{#pragma implementation} provide the
10593
user with a way of explicitly directing the compiler to emit entities
10594
with vague linkage (and debugging information) in a particular
10595
translation unit.
10596
 
10597
@emph{Note:} As of GCC 2.7.2, these @code{#pragma}s are not useful in
10598
most cases, because of COMDAT support and the ``key method'' heuristic
10599
mentioned in @ref{Vague Linkage}.  Using them can actually cause your
10600
program to grow due to unnecessary out-of-line copies of inline
10601
functions.  Currently (3.4) the only benefit of these
10602
@code{#pragma}s is reduced duplication of debugging information, and
10603
that should be addressed soon on DWARF 2 targets with the use of
10604
COMDAT groups.
10605
 
10606
@table @code
10607
@item #pragma interface
10608
@itemx #pragma interface "@var{subdir}/@var{objects}.h"
10609
@kindex #pragma interface
10610
Use this directive in @emph{header files} that define object classes, to save
10611
space in most of the object files that use those classes.  Normally,
10612
local copies of certain information (backup copies of inline member
10613
functions, debugging information, and the internal tables that implement
10614
virtual functions) must be kept in each object file that includes class
10615
definitions.  You can use this pragma to avoid such duplication.  When a
10616
header file containing @samp{#pragma interface} is included in a
10617
compilation, this auxiliary information will not be generated (unless
10618
the main input source file itself uses @samp{#pragma implementation}).
10619
Instead, the object files will contain references to be resolved at link
10620
time.
10621
 
10622
The second form of this directive is useful for the case where you have
10623
multiple headers with the same name in different directories.  If you
10624
use this form, you must specify the same string to @samp{#pragma
10625
implementation}.
10626
 
10627
@item #pragma implementation
10628
@itemx #pragma implementation "@var{objects}.h"
10629
@kindex #pragma implementation
10630
Use this pragma in a @emph{main input file}, when you want full output from
10631
included header files to be generated (and made globally visible).  The
10632
included header file, in turn, should use @samp{#pragma interface}.
10633
Backup copies of inline member functions, debugging information, and the
10634
internal tables used to implement virtual functions are all generated in
10635
implementation files.
10636
 
10637
@cindex implied @code{#pragma implementation}
10638
@cindex @code{#pragma implementation}, implied
10639
@cindex naming convention, implementation headers
10640
If you use @samp{#pragma implementation} with no argument, it applies to
10641
an include file with the same basename@footnote{A file's @dfn{basename}
10642
was the name stripped of all leading path information and of trailing
10643
suffixes, such as @samp{.h} or @samp{.C} or @samp{.cc}.} as your source
10644
file.  For example, in @file{allclass.cc}, giving just
10645
@samp{#pragma implementation}
10646
by itself is equivalent to @samp{#pragma implementation "allclass.h"}.
10647
 
10648
In versions of GNU C++ prior to 2.6.0 @file{allclass.h} was treated as
10649
an implementation file whenever you would include it from
10650
@file{allclass.cc} even if you never specified @samp{#pragma
10651
implementation}.  This was deemed to be more trouble than it was worth,
10652
however, and disabled.
10653
 
10654
Use the string argument if you want a single implementation file to
10655
include code from multiple header files.  (You must also use
10656
@samp{#include} to include the header file; @samp{#pragma
10657
implementation} only specifies how to use the file---it doesn't actually
10658
include it.)
10659
 
10660
There is no way to split up the contents of a single header file into
10661
multiple implementation files.
10662
@end table
10663
 
10664
@cindex inlining and C++ pragmas
10665
@cindex C++ pragmas, effect on inlining
10666
@cindex pragmas in C++, effect on inlining
10667
@samp{#pragma implementation} and @samp{#pragma interface} also have an
10668
effect on function inlining.
10669
 
10670
If you define a class in a header file marked with @samp{#pragma
10671
interface}, the effect on an inline function defined in that class is
10672
similar to an explicit @code{extern} declaration---the compiler emits
10673
no code at all to define an independent version of the function.  Its
10674
definition is used only for inlining with its callers.
10675
 
10676
@opindex fno-implement-inlines
10677
Conversely, when you include the same header file in a main source file
10678
that declares it as @samp{#pragma implementation}, the compiler emits
10679
code for the function itself; this defines a version of the function
10680
that can be found via pointers (or by callers compiled without
10681
inlining).  If all calls to the function can be inlined, you can avoid
10682
emitting the function by compiling with @option{-fno-implement-inlines}.
10683
If any calls were not inlined, you will get linker errors.
10684
 
10685
@node Template Instantiation
10686
@section Where's the Template?
10687
@cindex template instantiation
10688
 
10689
C++ templates are the first language feature to require more
10690
intelligence from the environment than one usually finds on a UNIX
10691
system.  Somehow the compiler and linker have to make sure that each
10692
template instance occurs exactly once in the executable if it is needed,
10693
and not at all otherwise.  There are two basic approaches to this
10694
problem, which are referred to as the Borland model and the Cfront model.
10695
 
10696
@table @asis
10697
@item Borland model
10698
Borland C++ solved the template instantiation problem by adding the code
10699
equivalent of common blocks to their linker; the compiler emits template
10700
instances in each translation unit that uses them, and the linker
10701
collapses them together.  The advantage of this model is that the linker
10702
only has to consider the object files themselves; there is no external
10703
complexity to worry about.  This disadvantage is that compilation time
10704
is increased because the template code is being compiled repeatedly.
10705
Code written for this model tends to include definitions of all
10706
templates in the header file, since they must be seen to be
10707
instantiated.
10708
 
10709
@item Cfront model
10710
The AT&T C++ translator, Cfront, solved the template instantiation
10711
problem by creating the notion of a template repository, an
10712
automatically maintained place where template instances are stored.  A
10713
more modern version of the repository works as follows: As individual
10714
object files are built, the compiler places any template definitions and
10715
instantiations encountered in the repository.  At link time, the link
10716
wrapper adds in the objects in the repository and compiles any needed
10717
instances that were not previously emitted.  The advantages of this
10718
model are more optimal compilation speed and the ability to use the
10719
system linker; to implement the Borland model a compiler vendor also
10720
needs to replace the linker.  The disadvantages are vastly increased
10721
complexity, and thus potential for error; for some code this can be
10722
just as transparent, but in practice it can been very difficult to build
10723
multiple programs in one directory and one program in multiple
10724
directories.  Code written for this model tends to separate definitions
10725
of non-inline member templates into a separate file, which should be
10726
compiled separately.
10727
@end table
10728
 
10729
When used with GNU ld version 2.8 or later on an ELF system such as
10730
GNU/Linux or Solaris 2, or on Microsoft Windows, G++ supports the
10731
Borland model.  On other systems, G++ implements neither automatic
10732
model.
10733
 
10734
A future version of G++ will support a hybrid model whereby the compiler
10735
will emit any instantiations for which the template definition is
10736
included in the compile, and store template definitions and
10737
instantiation context information into the object file for the rest.
10738
The link wrapper will extract that information as necessary and invoke
10739
the compiler to produce the remaining instantiations.  The linker will
10740
then combine duplicate instantiations.
10741
 
10742
In the mean time, you have the following options for dealing with
10743
template instantiations:
10744
 
10745
@enumerate
10746
@item
10747
@opindex frepo
10748
Compile your template-using code with @option{-frepo}.  The compiler will
10749
generate files with the extension @samp{.rpo} listing all of the
10750
template instantiations used in the corresponding object files which
10751
could be instantiated there; the link wrapper, @samp{collect2}, will
10752
then update the @samp{.rpo} files to tell the compiler where to place
10753
those instantiations and rebuild any affected object files.  The
10754
link-time overhead is negligible after the first pass, as the compiler
10755
will continue to place the instantiations in the same files.
10756
 
10757
This is your best option for application code written for the Borland
10758
model, as it will just work.  Code written for the Cfront model will
10759
need to be modified so that the template definitions are available at
10760
one or more points of instantiation; usually this is as simple as adding
10761
@code{#include <tmethods.cc>} to the end of each template header.
10762
 
10763
For library code, if you want the library to provide all of the template
10764
instantiations it needs, just try to link all of its object files
10765
together; the link will fail, but cause the instantiations to be
10766
generated as a side effect.  Be warned, however, that this may cause
10767
conflicts if multiple libraries try to provide the same instantiations.
10768
For greater control, use explicit instantiation as described in the next
10769
option.
10770
 
10771
@item
10772
@opindex fno-implicit-templates
10773
Compile your code with @option{-fno-implicit-templates} to disable the
10774
implicit generation of template instances, and explicitly instantiate
10775
all the ones you use.  This approach requires more knowledge of exactly
10776
which instances you need than do the others, but it's less
10777
mysterious and allows greater control.  You can scatter the explicit
10778
instantiations throughout your program, perhaps putting them in the
10779
translation units where the instances are used or the translation units
10780
that define the templates themselves; you can put all of the explicit
10781
instantiations you need into one big file; or you can create small files
10782
like
10783
 
10784
@smallexample
10785
#include "Foo.h"
10786
#include "Foo.cc"
10787
 
10788
template class Foo<int>;
10789
template ostream& operator <<
10790
                (ostream&, const Foo<int>&);
10791
@end smallexample
10792
 
10793
for each of the instances you need, and create a template instantiation
10794
library from those.
10795
 
10796
If you are using Cfront-model code, you can probably get away with not
10797
using @option{-fno-implicit-templates} when compiling files that don't
10798
@samp{#include} the member template definitions.
10799
 
10800
If you use one big file to do the instantiations, you may want to
10801
compile it without @option{-fno-implicit-templates} so you get all of the
10802
instances required by your explicit instantiations (but not by any
10803
other files) without having to specify them as well.
10804
 
10805
G++ has extended the template instantiation syntax given in the ISO
10806
standard to allow forward declaration of explicit instantiations
10807
(with @code{extern}), instantiation of the compiler support data for a
10808
template class (i.e.@: the vtable) without instantiating any of its
10809
members (with @code{inline}), and instantiation of only the static data
10810
members of a template class, without the support data or member
10811
functions (with (@code{static}):
10812
 
10813
@smallexample
10814
extern template int max (int, int);
10815
inline template class Foo<int>;
10816
static template class Foo<int>;
10817
@end smallexample
10818
 
10819
@item
10820
Do nothing.  Pretend G++ does implement automatic instantiation
10821
management.  Code written for the Borland model will work fine, but
10822
each translation unit will contain instances of each of the templates it
10823
uses.  In a large program, this can lead to an unacceptable amount of code
10824
duplication.
10825
@end enumerate
10826
 
10827
@node Bound member functions
10828
@section Extracting the function pointer from a bound pointer to member function
10829
@cindex pmf
10830
@cindex pointer to member function
10831
@cindex bound pointer to member function
10832
 
10833
In C++, pointer to member functions (PMFs) are implemented using a wide
10834
pointer of sorts to handle all the possible call mechanisms; the PMF
10835
needs to store information about how to adjust the @samp{this} pointer,
10836
and if the function pointed to is virtual, where to find the vtable, and
10837
where in the vtable to look for the member function.  If you are using
10838
PMFs in an inner loop, you should really reconsider that decision.  If
10839
that is not an option, you can extract the pointer to the function that
10840
would be called for a given object/PMF pair and call it directly inside
10841
the inner loop, to save a bit of time.
10842
 
10843
Note that you will still be paying the penalty for the call through a
10844
function pointer; on most modern architectures, such a call defeats the
10845
branch prediction features of the CPU@.  This is also true of normal
10846
virtual function calls.
10847
 
10848
The syntax for this extension is
10849
 
10850
@smallexample
10851
extern A a;
10852
extern int (A::*fp)();
10853
typedef int (*fptr)(A *);
10854
 
10855
fptr p = (fptr)(a.*fp);
10856
@end smallexample
10857
 
10858
For PMF constants (i.e.@: expressions of the form @samp{&Klasse::Member}),
10859
no object is needed to obtain the address of the function.  They can be
10860
converted to function pointers directly:
10861
 
10862
@smallexample
10863
fptr p1 = (fptr)(&A::foo);
10864
@end smallexample
10865
 
10866
@opindex Wno-pmf-conversions
10867
You must specify @option{-Wno-pmf-conversions} to use this extension.
10868
 
10869
@node C++ Attributes
10870
@section C++-Specific Variable, Function, and Type Attributes
10871
 
10872
Some attributes only make sense for C++ programs.
10873
 
10874
@table @code
10875
@item init_priority (@var{priority})
10876
@cindex init_priority attribute
10877
 
10878
 
10879
In Standard C++, objects defined at namespace scope are guaranteed to be
10880
initialized in an order in strict accordance with that of their definitions
10881
@emph{in a given translation unit}.  No guarantee is made for initializations
10882
across translation units.  However, GNU C++ allows users to control the
10883
order of initialization of objects defined at namespace scope with the
10884
@code{init_priority} attribute by specifying a relative @var{priority},
10885
a constant integral expression currently bounded between 101 and 65535
10886
inclusive.  Lower numbers indicate a higher priority.
10887
 
10888
In the following example, @code{A} would normally be created before
10889
@code{B}, but the @code{init_priority} attribute has reversed that order:
10890
 
10891
@smallexample
10892
Some_Class  A  __attribute__ ((init_priority (2000)));
10893
Some_Class  B  __attribute__ ((init_priority (543)));
10894
@end smallexample
10895
 
10896
@noindent
10897
Note that the particular values of @var{priority} do not matter; only their
10898
relative ordering.
10899
 
10900
@item java_interface
10901
@cindex java_interface attribute
10902
 
10903
This type attribute informs C++ that the class is a Java interface.  It may
10904
only be applied to classes declared within an @code{extern "Java"} block.
10905
Calls to methods declared in this interface will be dispatched using GCJ's
10906
interface table mechanism, instead of regular virtual table dispatch.
10907
 
10908
@end table
10909
 
10910
See also @xref{Namespace Association}.
10911
 
10912
@node Namespace Association
10913
@section Namespace Association
10914
 
10915
@strong{Caution:} The semantics of this extension are not fully
10916
defined.  Users should refrain from using this extension as its
10917
semantics may change subtly over time.  It is possible that this
10918
extension will be removed in future versions of G++.
10919
 
10920
A using-directive with @code{__attribute ((strong))} is stronger
10921
than a normal using-directive in two ways:
10922
 
10923
@itemize @bullet
10924
@item
10925
Templates from the used namespace can be specialized and explicitly
10926
instantiated as though they were members of the using namespace.
10927
 
10928
@item
10929
The using namespace is considered an associated namespace of all
10930
templates in the used namespace for purposes of argument-dependent
10931
name lookup.
10932
@end itemize
10933
 
10934
The used namespace must be nested within the using namespace so that
10935
normal unqualified lookup works properly.
10936
 
10937
This is useful for composing a namespace transparently from
10938
implementation namespaces.  For example:
10939
 
10940
@smallexample
10941
namespace std @{
10942
  namespace debug @{
10943
    template <class T> struct A @{ @};
10944
  @}
10945
  using namespace debug __attribute ((__strong__));
10946
  template <> struct A<int> @{ @};   // @r{ok to specialize}
10947
 
10948
  template <class T> void f (A<T>);
10949
@}
10950
 
10951
int main()
10952
@{
10953
  f (std::A<float>());             // @r{lookup finds} std::f
10954
  f (std::A<int>());
10955
@}
10956
@end smallexample
10957
 
10958
@node Java Exceptions
10959
@section Java Exceptions
10960
 
10961
The Java language uses a slightly different exception handling model
10962
from C++.  Normally, GNU C++ will automatically detect when you are
10963
writing C++ code that uses Java exceptions, and handle them
10964
appropriately.  However, if C++ code only needs to execute destructors
10965
when Java exceptions are thrown through it, GCC will guess incorrectly.
10966
Sample problematic code is:
10967
 
10968
@smallexample
10969
  struct S @{ ~S(); @};
10970
  extern void bar();    // @r{is written in Java, and may throw exceptions}
10971
  void foo()
10972
  @{
10973
    S s;
10974
    bar();
10975
  @}
10976
@end smallexample
10977
 
10978
@noindent
10979
The usual effect of an incorrect guess is a link failure, complaining of
10980
a missing routine called @samp{__gxx_personality_v0}.
10981
 
10982
You can inform the compiler that Java exceptions are to be used in a
10983
translation unit, irrespective of what it might think, by writing
10984
@samp{@w{#pragma GCC java_exceptions}} at the head of the file.  This
10985
@samp{#pragma} must appear before any functions that throw or catch
10986
exceptions, or run destructors when exceptions are thrown through them.
10987
 
10988
You cannot mix Java and C++ exceptions in the same translation unit.  It
10989
is believed to be safe to throw a C++ exception from one file through
10990
another file compiled for the Java exception model, or vice versa, but
10991
there may be bugs in this area.
10992
 
10993
@node Deprecated Features
10994
@section Deprecated Features
10995
 
10996
In the past, the GNU C++ compiler was extended to experiment with new
10997
features, at a time when the C++ language was still evolving.  Now that
10998
the C++ standard is complete, some of those features are superseded by
10999
superior alternatives.  Using the old features might cause a warning in
11000
some cases that the feature will be dropped in the future.  In other
11001
cases, the feature might be gone already.
11002
 
11003
While the list below is not exhaustive, it documents some of the options
11004
that are now deprecated:
11005
 
11006
@table @code
11007
@item -fexternal-templates
11008
@itemx -falt-external-templates
11009
These are two of the many ways for G++ to implement template
11010
instantiation.  @xref{Template Instantiation}.  The C++ standard clearly
11011
defines how template definitions have to be organized across
11012
implementation units.  G++ has an implicit instantiation mechanism that
11013
should work just fine for standard-conforming code.
11014
 
11015
@item -fstrict-prototype
11016
@itemx -fno-strict-prototype
11017
Previously it was possible to use an empty prototype parameter list to
11018
indicate an unspecified number of parameters (like C), rather than no
11019
parameters, as C++ demands.  This feature has been removed, except where
11020
it is required for backwards compatibility @xref{Backwards Compatibility}.
11021
@end table
11022
 
11023
G++ allows a virtual function returning @samp{void *} to be overridden
11024
by one returning a different pointer type.  This extension to the
11025
covariant return type rules is now deprecated and will be removed from a
11026
future version.
11027
 
11028
The G++ minimum and maximum operators (@samp{<?} and @samp{>?}) and
11029
their compound forms (@samp{<?=}) and @samp{>?=}) have been deprecated
11030
and will be removed in a future version.  Code using these operators
11031
should be modified to use @code{std::min} and @code{std::max} instead.
11032
 
11033
The named return value extension has been deprecated, and is now
11034
removed from G++.
11035
 
11036
The use of initializer lists with new expressions has been deprecated,
11037
and is now removed from G++.
11038
 
11039
Floating and complex non-type template parameters have been deprecated,
11040
and are now removed from G++.
11041
 
11042
The implicit typename extension has been deprecated and is now
11043
removed from G++.
11044
 
11045
The use of default arguments in function pointers, function typedefs
11046
and other places where they are not permitted by the standard is
11047
deprecated and will be removed from a future version of G++.
11048
 
11049
G++ allows floating-point literals to appear in integral constant expressions,
11050
e.g. @samp{ enum E @{ e = int(2.2 * 3.7) @} }
11051
This extension is deprecated and will be removed from a future version.
11052
 
11053
G++ allows static data members of const floating-point type to be declared
11054
with an initializer in a class definition. The standard only allows
11055
initializers for static members of const integral types and const
11056
enumeration types so this extension has been deprecated and will be removed
11057
from a future version.
11058
 
11059
@node Backwards Compatibility
11060
@section Backwards Compatibility
11061
@cindex Backwards Compatibility
11062
@cindex ARM [Annotated C++ Reference Manual]
11063
 
11064
Now that there is a definitive ISO standard C++, G++ has a specification
11065
to adhere to.  The C++ language evolved over time, and features that
11066
used to be acceptable in previous drafts of the standard, such as the ARM
11067
[Annotated C++ Reference Manual], are no longer accepted.  In order to allow
11068
compilation of C++ written to such drafts, G++ contains some backwards
11069
compatibilities.  @emph{All such backwards compatibility features are
11070
liable to disappear in future versions of G++.} They should be considered
11071
deprecated @xref{Deprecated Features}.
11072
 
11073
@table @code
11074
@item For scope
11075
If a variable is declared at for scope, it used to remain in scope until
11076
the end of the scope which contained the for statement (rather than just
11077
within the for scope).  G++ retains this, but issues a warning, if such a
11078
variable is accessed outside the for scope.
11079
 
11080
@item Implicit C language
11081
Old C system header files did not contain an @code{extern "C" @{@dots{}@}}
11082
scope to set the language.  On such systems, all header files are
11083
implicitly scoped inside a C language scope.  Also, an empty prototype
11084
@code{()} will be treated as an unspecified number of arguments, rather
11085
than no arguments, as C++ demands.
11086
@end table

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