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@c Copyright 2002, 2004 Free Software Foundation, Inc.
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@c This is part of the GAS manual.
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@c For copying conditions, see the file as.texinfo.
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@c CRIS description contributed by Axis Communications.
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@ifset GENERIC
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@page
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@node CRIS-Dependent
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@chapter CRIS Dependent Features
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@end ifset
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@ifclear GENERIC
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@node Machine Dependencies
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@chapter CRIS Dependent Features
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@end ifclear
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15
@cindex CRIS support
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@menu
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* CRIS-Opts::              Command-line Options
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* CRIS-Expand::            Instruction expansion
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* CRIS-Symbols::           Symbols
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* CRIS-Syntax::            Syntax
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@end menu
22
 
23
@node CRIS-Opts
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@section Command-line Options
25
 
26
@cindex options, CRIS
27
@cindex CRIS options
28
The CRIS version of @code{@value{AS}} has these
29
machine-dependent command-line options.
30
 
31
@cindex @option{--emulation=criself} command line option, CRIS
32
@cindex @option{--emulation=crisaout} command line option, CRIS
33
@cindex CRIS @option{--emulation=criself} command line option
34
@cindex CRIS @option{--emulation=crisaout} command line option
35
 
36
The format of the generated object files can be either ELF or
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a.out, specified by the command-line options
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@option{--emulation=crisaout} and @option{--emulation=criself}.
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The default is ELF (criself), unless @code{@value{AS}} has been
40
configured specifically for a.out by using the configuration
41
name @code{cris-axis-aout}.
42
 
43
@cindex @option{--underscore} command line option, CRIS
44
@cindex @option{--no-underscore} command line option, CRIS
45
@cindex CRIS @option{--underscore} command line option
46
@cindex CRIS @option{--no-underscore} command line option
47
There are two different link-incompatible ELF object file
48
variants for CRIS, for use in environments where symbols are
49
expected to be prefixed by a leading @samp{_} character and for
50
environments without such a symbol prefix.  The variant used for
51
GNU/Linux port has no symbol prefix.  Which variant to produce
52
is specified by either of the options @option{--underscore} and
53
@option{--no-underscore}.  The default is @option{--underscore}.
54
Since symbols in CRIS a.out objects are expected to have a
55
@samp{_} prefix, specifying @option{--no-underscore} when
56
generating a.out objects is an error.  Besides the object format
57
difference, the effect of this option is to parse register names
58
differently (@pxref{crisnous}).  The @option{--no-underscore}
59
option makes a @samp{$} register prefix mandatory.
60
 
61
@cindex @option{--pic} command line option, CRIS
62
@cindex CRIS @option{--pic} command line option
63
@cindex Position-independent code, CRIS
64
@cindex CRIS position-independent code
65
The option @option{--pic} must be passed to @code{@value{AS}} in
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order to recognize the symbol syntax used for ELF (SVR4 PIC)
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position-independent-code (@pxref{crispic}).  This will also
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affect expansion of instructions.  The expansion with
69
@option{--pic} will use PC-relative rather than (slightly
70
faster) absolute addresses in those expansions.
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72
@cindex @option{--march=@var{architecture}} command line option, CRIS
73
@cindex CRIS @option{--march=@var{architecture}} command line option
74
@cindex Architecture variant option, CRIS
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@cindex CRIS architecture variant option
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The option @option{--march=@var{architecture}}
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@anchor{march-option}specifies the recognized instruction set
78
and recognized register names.  It also controls the
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architecture type of the object file.  Valid values for
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@var{architecture} are:
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@table @code
82
 
83
@item v0_v10
84
All instructions and register names for any architecture variant
85
in the set v0@dots{}v10 are recognized.  This is the
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default if the target is configured as cris-*.
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88
@item v10
89
Only instructions and register names for CRIS v10 (as found in
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ETRAX 100 LX) are recognized.  This is the default if the target
91
is configured as crisv10-*.
92
 
93
@item v32
94
Only instructions and register names for CRIS v32 (code name
95
Guinness) are recognized.  This is the default if the target is
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configured as crisv32-*.  This value implies
97
@option{--no-mul-bug-abort}.  (A subsequent
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@option{--mul-bug-abort} will turn it back on.)
99
 
100
@item common_v10_v32
101
Only instructions with register names and addressing modes with
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opcodes common to the v10 and v32 are recognized.
103
@end table
104
 
105
@cindex @option{-N} command line option, CRIS
106
@cindex CRIS @option{-N} command line option
107
When @option{-N} is specified, @code{@value{AS}} will emit a
108
warning when a 16-bit branch instruction is expanded into a
109
32-bit multiple-instruction construct (@pxref{CRIS-Expand}).
110
 
111
@cindex @option{--no-mul-bug-abort} command line option, CRIS
112
@cindex @option{--mul-bug-abort} command line option, CRIS
113
@cindex CRIS @option{--no-mul-bug-abort} command line option
114
@cindex CRIS @option{--mul-bug-abort} command line option
115
 
116
Some versions of the CRIS v10, for example in the Etrax 100 LX,
117
contain a bug that causes destabilizing memory accesses when a
118
multiply instruction is executed with certain values in the
119
first operand just before a cache-miss.  When the
120
@option{--mul-bug-abort} command line option is active (the
121
default value), @code{@value{AS}} will refuse to assemble a file
122
containing a multiply instruction at a dangerous offset, one
123
that could be the last on a cache-line, or is in a section with
124
insufficient alignment.  This placement checking does not catch
125
any case where the multiply instruction is dangerously placed
126
because it is located in a delay-slot.  The
127
@option{--mul-bug-abort} command line option turns off the
128
checking.
129
 
130
@node CRIS-Expand
131
@section Instruction expansion
132
 
133
@cindex instruction expansion, CRIS
134
@cindex CRIS instruction expansion
135
@code{@value{AS}} will silently choose an instruction that fits
136
the operand size for @samp{[register+constant]} operands.  For
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example, the offset @code{127} in @code{move.d [r3+127],r4} fits
138
in an instruction using a signed-byte offset.  Similarly,
139
@code{move.d [r2+32767],r1} will generate an instruction using a
140
16-bit offset.  For symbolic expressions and constants that do
141
not fit in 16 bits including the sign bit, a 32-bit offset is
142
generated.
143
 
144
For branches, @code{@value{AS}} will expand from a 16-bit branch
145
instruction into a sequence of instructions that can reach a
146
full 32-bit address.  Since this does not correspond to a single
147
instruction, such expansions can optionally be warned about.
148
@xref{CRIS-Opts}.
149
 
150
If the operand is found to fit the range, a @code{lapc} mnemonic
151
will translate to a @code{lapcq} instruction.  Use @code{lapc.d}
152
to force the 32-bit @code{lapc} instruction.
153
 
154
Similarly, the @code{addo} mnemonic will translate to the
155
shortest fitting instruction of @code{addoq}, @code{addo.w} and
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@code{addo.d}, when used with a operand that is a constant known
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at assembly time.
158
 
159
@node CRIS-Symbols
160
@section Symbols
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@cindex Symbols, built-in, CRIS
162
@cindex Symbols, CRIS, built-in
163
@cindex CRIS built-in symbols
164
@cindex Built-in symbols, CRIS
165
 
166
Some symbols are defined by the assembler.  They're intended to
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be used in conditional assembly, for example:
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@smallexample
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 .if ..asm.arch.cris.v32
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 @var{code for CRIS v32}
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 .elseif ..asm.arch.cris.common_v10_v32
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 @var{code common to CRIS v32 and CRIS v10}
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 .elseif ..asm.arch.cris.v10 | ..asm.arch.cris.any_v0_v10
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 @var{code for v10}
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 .else
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 .error "Code needs to be added here."
177
 .endif
178
@end smallexample
179
 
180
These symbols are defined in the assembler, reflecting
181
command-line options, either when specified or the default.
182
They are always defined, to 0 or 1.
183
@table @code
184
 
185
@item ..asm.arch.cris.any_v0_v10
186
This symbol is non-zero when @option{--march=v0_v10} is specified
187
or the default.
188
 
189
@item ..asm.arch.cris.common_v10_v32
190
Set according to the option @option{--march=common_v10_v32}.
191
 
192
@item ..asm.arch.cris.v10
193
Reflects the option @option{--march=v10}.
194
 
195
@item ..asm.arch.cris.v32
196
Corresponds to @option{--march=v10}.
197
@end table
198
 
199
Speaking of symbols, when a symbol is used in code, it can have
200
a suffix modifying its value for use in position-independent
201
code. @xref{CRIS-Pic}.
202
 
203
@node CRIS-Syntax
204
@section Syntax
205
 
206
There are different aspects of the CRIS assembly syntax.
207
 
208
@menu
209
* CRIS-Chars::                  Special Characters
210
* CRIS-Pic::                    Position-Independent Code Symbols
211
* CRIS-Regs::                   Register Names
212
* CRIS-Pseudos::                Assembler Directives
213
@end menu
214
 
215
@node CRIS-Chars
216
@subsection Special Characters
217
@cindex line comment characters, CRIS
218
@cindex CRIS line comment characters
219
 
220
The character @samp{#} is a line comment character.  It starts a
221
comment if and only if it is placed at the beginning of a line.
222
 
223
A @samp{;} character starts a comment anywhere on the line,
224
causing all characters up to the end of the line to be ignored.
225
 
226
A @samp{@@} character is handled as a line separator equivalent
227
to a logical new-line character (except in a comment), so
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separate instructions can be specified on a single line.
229
 
230
@node CRIS-Pic
231
@subsection Symbols in position-independent code
232
@cindex Symbols in position-independent code, CRIS
233
@cindex CRIS symbols in position-independent code
234
@cindex Position-independent code, symbols in, CRIS
235
 
236
When generating @anchor{crispic}position-independent code (SVR4
237
PIC) for use in cris-axis-linux-gnu or crisv32-axis-linux-gnu
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shared libraries, symbol
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suffixes are used to specify what kind of run-time symbol lookup
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will be used, expressed in the object as different
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@emph{relocation types}.  Usually, all absolute symbol values
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must be located in a table, the @emph{global offset table},
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leaving the code position-independent; independent of values of
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global symbols and independent of the address of the code.  The
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suffix modifies the value of the symbol, into for example an
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index into the global offset table where the real symbol value
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is entered, or a PC-relative value, or a value relative to the
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start of the global offset table.  All symbol suffixes start
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with the character @samp{:} (omitted in the list below).  Every
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symbol use in code or a read-only section must therefore have a
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PIC suffix to enable a useful shared library to be created.
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Usually, these constructs must not be used with an additive
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constant offset as is usually allowed, i.e.@: no 4 as in
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@code{symbol + 4} is allowed.  This restriction is checked at
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link-time, not at assembly-time.
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257
@table @code
258
@item GOT
259
 
260
Attaching this suffix to a symbol in an instruction causes the
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symbol to be entered into the global offset table.  The value is
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a 32-bit index for that symbol into the global offset table.
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The name of the corresponding relocation is
264
@samp{R_CRIS_32_GOT}.  Example: @code{move.d
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[$r0+extsym:GOT],$r9}
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267
@item GOT16
268
 
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Same as for @samp{GOT}, but the value is a 16-bit index into the
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global offset table.  The corresponding relocation is
271
@samp{R_CRIS_16_GOT}.  Example: @code{move.d
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[$r0+asymbol:GOT16],$r10}
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274
@item PLT
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This suffix is used for function symbols.  It causes a
277
@emph{procedure linkage table}, an array of code stubs, to be
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created at the time the shared object is created or linked
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against, together with a global offset table entry.  The value
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is a pc-relative offset to the corresponding stub code in the
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procedure linkage table.  This arrangement causes the run-time
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symbol resolver to be called to look up and set the value of the
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symbol the first time the function is called (at latest;
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depending environment variables).  It is only safe to leave the
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symbol unresolved this way if all references are function calls.
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The name of the relocation is @samp{R_CRIS_32_PLT_PCREL}.
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Example: @code{add.d fnname:PLT,$pc}
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289
@item PLTG
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Like PLT, but the value is relative to the beginning of the
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global offset table.  The relocation is
293
@samp{R_CRIS_32_PLT_GOTREL}.  Example: @code{move.d
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fnname:PLTG,$r3}
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296
@item GOTPLT
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298
Similar to @samp{PLT}, but the value of the symbol is a 32-bit
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index into the global offset table.  This is somewhat of a mix
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between the effect of the @samp{GOT} and the @samp{PLT} suffix;
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the difference to @samp{GOT} is that there will be a procedure
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linkage table entry created, and that the symbol is assumed to
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be a function entry and will be resolved by the run-time
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resolver as with @samp{PLT}.  The relocation is
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@samp{R_CRIS_32_GOTPLT}.  Example: @code{jsr
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[$r0+fnname:GOTPLT]}
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308
@item GOTPLT16
309
 
310
A variant of @samp{GOTPLT} giving a 16-bit value.  Its
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relocation name is @samp{R_CRIS_16_GOTPLT}.  Example: @code{jsr
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[$r0+fnname:GOTPLT16]}
313
 
314
@item GOTOFF
315
 
316
This suffix must only be attached to a local symbol, but may be
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used in an expression adding an offset.  The value is the
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address of the symbol relative to the start of the global offset
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table.  The relocation name is @samp{R_CRIS_32_GOTREL}.
320
Example: @code{move.d [$r0+localsym:GOTOFF],r3}
321
@end table
322
 
323
@node CRIS-Regs
324
@subsection Register names
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@cindex register names, CRIS
326
@cindex CRIS register names
327
 
328
A @samp{$} character may always prefix a general or special
329
register name in an instruction operand but is mandatory when
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the option @option{--no-underscore} is specified or when the
331
@code{.syntax register_prefix} directive is in effect
332
(@pxref{crisnous}).  Register names are case-insensitive.
333
 
334
@node CRIS-Pseudos
335
@subsection Assembler Directives
336
@cindex assembler directives, CRIS
337
@cindex pseudo-ops, CRIS
338
@cindex CRIS assembler directives
339
@cindex CRIS pseudo-ops
340
 
341
There are a few CRIS-specific pseudo-directives in addition to
342
the generic ones.  @xref{Pseudo Ops}.  Constants emitted by
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pseudo-directives are in little-endian order for CRIS.  There is
344
no support for floating-point-specific directives for CRIS.
345
 
346
@table @code
347
@item .dword EXPRESSIONS
348
@cindex assembler directive .dword, CRIS
349
@cindex pseudo-op .dword, CRIS
350
@cindex CRIS assembler directive .dword
351
@cindex CRIS pseudo-op .dword
352
 
353
The @code{.dword} directive is a synonym for @code{.int},
354
expecting zero or more EXPRESSIONS, separated by commas.  For
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each expression, a 32-bit little-endian constant is emitted.
356
 
357
@item .syntax ARGUMENT
358
@cindex assembler directive .syntax, CRIS
359
@cindex pseudo-op .syntax, CRIS
360
@cindex CRIS assembler directive .syntax
361
@cindex CRIS pseudo-op .syntax
362
The @code{.syntax} directive takes as @var{ARGUMENT} one of the
363
following case-sensitive choices.
364
 
365
@table @code
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@item no_register_prefix
367
 
368
The @code{.syntax no_register_prefix} @anchor{crisnous}directive
369
makes a @samp{$} character prefix on all registers optional.  It
370
overrides a previous setting, including the corresponding effect
371
of the option @option{--no-underscore}.  If this directive is
372
used when ordinary symbols do not have a @samp{_} character
373
prefix, care must be taken to avoid ambiguities whether an
374
operand is a register or a symbol; using symbols with names the
375
same as general or special registers then invoke undefined
376
behavior.
377
 
378
@item register_prefix
379
 
380
This directive makes a @samp{$} character prefix on all
381
registers mandatory.  It overrides a previous setting, including
382
the corresponding effect of the option @option{--underscore}.
383
 
384
@item leading_underscore
385
 
386
This is an assertion directive, emitting an error if the
387
@option{--no-underscore} option is in effect.
388
 
389
@item no_leading_underscore
390
 
391
This is the opposite of the @code{.syntax leading_underscore}
392
directive and emits an error if the option @option{--underscore}
393
is in effect.
394
@end table
395
 
396
@item .arch ARGUMENT
397
@cindex assembler directive .arch, CRIS
398
@cindex pseudo-op .arch, CRIS
399
@cindex CRIS assembler directive .arch
400
@cindex CRIS pseudo-op .arch
401
This is an assertion directive, giving an error if the specified
402
@var{ARGUMENT} is not the same as the specified or default value
403
for the @option{--march=@var{architecture}} option
404
(@pxref{march-option}).
405
 
406
@c If you compare with md_pseudo_table, you see that we don't
407
@c document ".file" and ".loc" here.  This is because we're just
408
@c wrapping the corresponding ELF function and emitting an error for
409
@c a.out.
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@end table

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