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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libiberty/] [alloca.c] - Blame information for rev 737

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1 736 jeremybenn
/* alloca.c -- allocate automatically reclaimed memory
2
   (Mostly) portable public-domain implementation -- D A Gwyn
3
 
4
   This implementation of the PWB library alloca function,
5
   which is used to allocate space off the run-time stack so
6
   that it is automatically reclaimed upon procedure exit,
7
   was inspired by discussions with J. Q. Johnson of Cornell.
8
   J.Otto Tennant <jot@cray.com> contributed the Cray support.
9
 
10
   There are some preprocessor constants that can
11
   be defined when compiling for your specific system, for
12
   improved efficiency; however, the defaults should be okay.
13
 
14
   The general concept of this implementation is to keep
15
   track of all alloca-allocated blocks, and reclaim any
16
   that are found to be deeper in the stack than the current
17
   invocation.  This heuristic does not reclaim storage as
18
   soon as it becomes invalid, but it will do so eventually.
19
 
20
   As a special case, alloca(0) reclaims storage without
21
   allocating any.  It is a good idea to use alloca(0) in
22
   your main control loop, etc. to force garbage collection.  */
23
 
24
/*
25
 
26
@deftypefn Replacement void* alloca (size_t @var{size})
27
 
28
This function allocates memory which will be automatically reclaimed
29
after the procedure exits.  The @libib{} implementation does not free
30
the memory immediately but will do so eventually during subsequent
31
calls to this function.  Memory is allocated using @code{xmalloc} under
32
normal circumstances.
33
 
34
The header file @file{alloca-conf.h} can be used in conjunction with the
35
GNU Autoconf test @code{AC_FUNC_ALLOCA} to test for and properly make
36
available this function.  The @code{AC_FUNC_ALLOCA} test requires that
37
client code use a block of preprocessor code to be safe (see the Autoconf
38
manual for more); this header incorporates that logic and more, including
39
the possibility of a GCC built-in function.
40
 
41
@end deftypefn
42
 
43
*/
44
 
45
#ifdef HAVE_CONFIG_H
46
#include <config.h>
47
#endif
48
 
49
#include <libiberty.h>
50
 
51
#ifdef HAVE_STRING_H
52
#include <string.h>
53
#endif
54
#ifdef HAVE_STDLIB_H
55
#include <stdlib.h>
56
#endif
57
 
58
/* These variables are used by the ASTRDUP implementation that relies
59
   on C_alloca.  */
60
#ifdef __cplusplus
61
extern "C" {
62
#endif /* __cplusplus */
63
const char *libiberty_optr;
64
char *libiberty_nptr;
65
unsigned long libiberty_len;
66
#ifdef __cplusplus
67
}
68
#endif /* __cplusplus */
69
 
70
/* If your stack is a linked list of frames, you have to
71
   provide an "address metric" ADDRESS_FUNCTION macro.  */
72
 
73
#if defined (CRAY) && defined (CRAY_STACKSEG_END)
74
static long i00afunc ();
75
#define ADDRESS_FUNCTION(arg) (char *) i00afunc (&(arg))
76
#else
77
#define ADDRESS_FUNCTION(arg) &(arg)
78
#endif
79
 
80
#ifndef NULL
81
#define NULL    0
82
#endif
83
 
84
/* Define STACK_DIRECTION if you know the direction of stack
85
   growth for your system; otherwise it will be automatically
86
   deduced at run-time.
87
 
88
   STACK_DIRECTION > 0 => grows toward higher addresses
89
   STACK_DIRECTION < 0 => grows toward lower addresses
90
   STACK_DIRECTION = 0 => direction of growth unknown  */
91
 
92
#ifndef STACK_DIRECTION
93
#define STACK_DIRECTION 0        /* Direction unknown.  */
94
#endif
95
 
96
#if STACK_DIRECTION != 0
97
 
98
#define STACK_DIR       STACK_DIRECTION /* Known at compile-time.  */
99
 
100
#else /* STACK_DIRECTION == 0; need run-time code.  */
101
 
102
static int stack_dir;           /* 1 or -1 once known.  */
103
#define STACK_DIR       stack_dir
104
 
105
static void
106
find_stack_direction (void)
107
{
108
  static char *addr = NULL;     /* Address of first `dummy', once known.  */
109
  auto char dummy;              /* To get stack address.  */
110
 
111
  if (addr == NULL)
112
    {                           /* Initial entry.  */
113
      addr = ADDRESS_FUNCTION (dummy);
114
 
115
      find_stack_direction ();  /* Recurse once.  */
116
    }
117
  else
118
    {
119
      /* Second entry.  */
120
      if (ADDRESS_FUNCTION (dummy) > addr)
121
        stack_dir = 1;          /* Stack grew upward.  */
122
      else
123
        stack_dir = -1;         /* Stack grew downward.  */
124
    }
125
}
126
 
127
#endif /* STACK_DIRECTION == 0 */
128
 
129
/* An "alloca header" is used to:
130
   (a) chain together all alloca'ed blocks;
131
   (b) keep track of stack depth.
132
 
133
   It is very important that sizeof(header) agree with malloc
134
   alignment chunk size.  The following default should work okay.  */
135
 
136
#ifndef ALIGN_SIZE
137
#define ALIGN_SIZE      sizeof(double)
138
#endif
139
 
140
typedef union hdr
141
{
142
  char align[ALIGN_SIZE];       /* To force sizeof(header).  */
143
  struct
144
    {
145
      union hdr *next;          /* For chaining headers.  */
146
      char *deep;               /* For stack depth measure.  */
147
    } h;
148
} header;
149
 
150
static header *last_alloca_header = NULL;       /* -> last alloca header.  */
151
 
152
/* Return a pointer to at least SIZE bytes of storage,
153
   which will be automatically reclaimed upon exit from
154
   the procedure that called alloca.  Originally, this space
155
   was supposed to be taken from the current stack frame of the
156
   caller, but that method cannot be made to work for some
157
   implementations of C, for example under Gould's UTX/32.  */
158
 
159
/* @undocumented C_alloca */
160
 
161
PTR
162
C_alloca (size_t size)
163
{
164
  auto char probe;              /* Probes stack depth: */
165
  register char *depth = ADDRESS_FUNCTION (probe);
166
 
167
#if STACK_DIRECTION == 0
168
  if (STACK_DIR == 0)            /* Unknown growth direction.  */
169
    find_stack_direction ();
170
#endif
171
 
172
  /* Reclaim garbage, defined as all alloca'd storage that
173
     was allocated from deeper in the stack than currently.  */
174
 
175
  {
176
    register header *hp;        /* Traverses linked list.  */
177
 
178
    for (hp = last_alloca_header; hp != NULL;)
179
      if ((STACK_DIR > 0 && hp->h.deep > depth)
180
          || (STACK_DIR < 0 && hp->h.deep < depth))
181
        {
182
          register header *np = hp->h.next;
183
 
184
          free ((PTR) hp);      /* Collect garbage.  */
185
 
186
          hp = np;              /* -> next header.  */
187
        }
188
      else
189
        break;                  /* Rest are not deeper.  */
190
 
191
    last_alloca_header = hp;    /* -> last valid storage.  */
192
  }
193
 
194
  if (size == 0)
195
    return NULL;                /* No allocation required.  */
196
 
197
  /* Allocate combined header + user data storage.  */
198
 
199
  {
200
    register void *new_storage = XNEWVEC (char, sizeof (header) + size);
201
    /* Address of header.  */
202
 
203
    if (new_storage == 0)
204
      abort();
205
 
206
    ((header *) new_storage)->h.next = last_alloca_header;
207
    ((header *) new_storage)->h.deep = depth;
208
 
209
    last_alloca_header = (header *) new_storage;
210
 
211
    /* User storage begins just after header.  */
212
 
213
    return (PTR) ((char *) new_storage + sizeof (header));
214
  }
215
}
216
 
217
#if defined (CRAY) && defined (CRAY_STACKSEG_END)
218
 
219
#ifdef DEBUG_I00AFUNC
220
#include <stdio.h>
221
#endif
222
 
223
#ifndef CRAY_STACK
224
#define CRAY_STACK
225
#ifndef CRAY2
226
/* Stack structures for CRAY-1, CRAY X-MP, and CRAY Y-MP */
227
struct stack_control_header
228
  {
229
    long shgrow:32;             /* Number of times stack has grown.  */
230
    long shaseg:32;             /* Size of increments to stack.  */
231
    long shhwm:32;              /* High water mark of stack.  */
232
    long shsize:32;             /* Current size of stack (all segments).  */
233
  };
234
 
235
/* The stack segment linkage control information occurs at
236
   the high-address end of a stack segment.  (The stack
237
   grows from low addresses to high addresses.)  The initial
238
   part of the stack segment linkage control information is
239
   0200 (octal) words.  This provides for register storage
240
   for the routine which overflows the stack.  */
241
 
242
struct stack_segment_linkage
243
  {
244
    long ss[0200];              /* 0200 overflow words.  */
245
    long sssize:32;             /* Number of words in this segment.  */
246
    long ssbase:32;             /* Offset to stack base.  */
247
    long:32;
248
    long sspseg:32;             /* Offset to linkage control of previous
249
                                   segment of stack.  */
250
    long:32;
251
    long sstcpt:32;             /* Pointer to task common address block.  */
252
    long sscsnm;                /* Private control structure number for
253
                                   microtasking.  */
254
    long ssusr1;                /* Reserved for user.  */
255
    long ssusr2;                /* Reserved for user.  */
256
    long sstpid;                /* Process ID for pid based multi-tasking.  */
257
    long ssgvup;                /* Pointer to multitasking thread giveup.  */
258
    long sscray[7];             /* Reserved for Cray Research.  */
259
    long ssa0;
260
    long ssa1;
261
    long ssa2;
262
    long ssa3;
263
    long ssa4;
264
    long ssa5;
265
    long ssa6;
266
    long ssa7;
267
    long sss0;
268
    long sss1;
269
    long sss2;
270
    long sss3;
271
    long sss4;
272
    long sss5;
273
    long sss6;
274
    long sss7;
275
  };
276
 
277
#else /* CRAY2 */
278
/* The following structure defines the vector of words
279
   returned by the STKSTAT library routine.  */
280
struct stk_stat
281
  {
282
    long now;                   /* Current total stack size.  */
283
    long maxc;                  /* Amount of contiguous space which would
284
                                   be required to satisfy the maximum
285
                                   stack demand to date.  */
286
    long high_water;            /* Stack high-water mark.  */
287
    long overflows;             /* Number of stack overflow ($STKOFEN) calls.  */
288
    long hits;                  /* Number of internal buffer hits.  */
289
    long extends;               /* Number of block extensions.  */
290
    long stko_mallocs;          /* Block allocations by $STKOFEN.  */
291
    long underflows;            /* Number of stack underflow calls ($STKRETN).  */
292
    long stko_free;             /* Number of deallocations by $STKRETN.  */
293
    long stkm_free;             /* Number of deallocations by $STKMRET.  */
294
    long segments;              /* Current number of stack segments.  */
295
    long maxs;                  /* Maximum number of stack segments so far.  */
296
    long pad_size;              /* Stack pad size.  */
297
    long current_address;       /* Current stack segment address.  */
298
    long current_size;          /* Current stack segment size.  This
299
                                   number is actually corrupted by STKSTAT to
300
                                   include the fifteen word trailer area.  */
301
    long initial_address;       /* Address of initial segment.  */
302
    long initial_size;          /* Size of initial segment.  */
303
  };
304
 
305
/* The following structure describes the data structure which trails
306
   any stack segment.  I think that the description in 'asdef' is
307
   out of date.  I only describe the parts that I am sure about.  */
308
 
309
struct stk_trailer
310
  {
311
    long this_address;          /* Address of this block.  */
312
    long this_size;             /* Size of this block (does not include
313
                                   this trailer).  */
314
    long unknown2;
315
    long unknown3;
316
    long link;                  /* Address of trailer block of previous
317
                                   segment.  */
318
    long unknown5;
319
    long unknown6;
320
    long unknown7;
321
    long unknown8;
322
    long unknown9;
323
    long unknown10;
324
    long unknown11;
325
    long unknown12;
326
    long unknown13;
327
    long unknown14;
328
  };
329
 
330
#endif /* CRAY2 */
331
#endif /* not CRAY_STACK */
332
 
333
#ifdef CRAY2
334
/* Determine a "stack measure" for an arbitrary ADDRESS.
335
   I doubt that "lint" will like this much.  */
336
 
337
static long
338
i00afunc (long *address)
339
{
340
  struct stk_stat status;
341
  struct stk_trailer *trailer;
342
  long *block, size;
343
  long result = 0;
344
 
345
  /* We want to iterate through all of the segments.  The first
346
     step is to get the stack status structure.  We could do this
347
     more quickly and more directly, perhaps, by referencing the
348
     $LM00 common block, but I know that this works.  */
349
 
350
  STKSTAT (&status);
351
 
352
  /* Set up the iteration.  */
353
 
354
  trailer = (struct stk_trailer *) (status.current_address
355
                                    + status.current_size
356
                                    - 15);
357
 
358
  /* There must be at least one stack segment.  Therefore it is
359
     a fatal error if "trailer" is null.  */
360
 
361
  if (trailer == 0)
362
    abort ();
363
 
364
  /* Discard segments that do not contain our argument address.  */
365
 
366
  while (trailer != 0)
367
    {
368
      block = (long *) trailer->this_address;
369
      size = trailer->this_size;
370
      if (block == 0 || size == 0)
371
        abort ();
372
      trailer = (struct stk_trailer *) trailer->link;
373
      if ((block <= address) && (address < (block + size)))
374
        break;
375
    }
376
 
377
  /* Set the result to the offset in this segment and add the sizes
378
     of all predecessor segments.  */
379
 
380
  result = address - block;
381
 
382
  if (trailer == 0)
383
    {
384
      return result;
385
    }
386
 
387
  do
388
    {
389
      if (trailer->this_size <= 0)
390
        abort ();
391
      result += trailer->this_size;
392
      trailer = (struct stk_trailer *) trailer->link;
393
    }
394
  while (trailer != 0);
395
 
396
  /* We are done.  Note that if you present a bogus address (one
397
     not in any segment), you will get a different number back, formed
398
     from subtracting the address of the first block.  This is probably
399
     not what you want.  */
400
 
401
  return (result);
402
}
403
 
404
#else /* not CRAY2 */
405
/* Stack address function for a CRAY-1, CRAY X-MP, or CRAY Y-MP.
406
   Determine the number of the cell within the stack,
407
   given the address of the cell.  The purpose of this
408
   routine is to linearize, in some sense, stack addresses
409
   for alloca.  */
410
 
411
static long
412
i00afunc (long address)
413
{
414
  long stkl = 0;
415
 
416
  long size, pseg, this_segment, stack;
417
  long result = 0;
418
 
419
  struct stack_segment_linkage *ssptr;
420
 
421
  /* Register B67 contains the address of the end of the
422
     current stack segment.  If you (as a subprogram) store
423
     your registers on the stack and find that you are past
424
     the contents of B67, you have overflowed the segment.
425
 
426
     B67 also points to the stack segment linkage control
427
     area, which is what we are really interested in.  */
428
 
429
  stkl = CRAY_STACKSEG_END ();
430
  ssptr = (struct stack_segment_linkage *) stkl;
431
 
432
  /* If one subtracts 'size' from the end of the segment,
433
     one has the address of the first word of the segment.
434
 
435
     If this is not the first segment, 'pseg' will be
436
     nonzero.  */
437
 
438
  pseg = ssptr->sspseg;
439
  size = ssptr->sssize;
440
 
441
  this_segment = stkl - size;
442
 
443
  /* It is possible that calling this routine itself caused
444
     a stack overflow.  Discard stack segments which do not
445
     contain the target address.  */
446
 
447
  while (!(this_segment <= address && address <= stkl))
448
    {
449
#ifdef DEBUG_I00AFUNC
450
      fprintf (stderr, "%011o %011o %011o\n", this_segment, address, stkl);
451
#endif
452
      if (pseg == 0)
453
        break;
454
      stkl = stkl - pseg;
455
      ssptr = (struct stack_segment_linkage *) stkl;
456
      size = ssptr->sssize;
457
      pseg = ssptr->sspseg;
458
      this_segment = stkl - size;
459
    }
460
 
461
  result = address - this_segment;
462
 
463
  /* If you subtract pseg from the current end of the stack,
464
     you get the address of the previous stack segment's end.
465
     This seems a little convoluted to me, but I'll bet you save
466
     a cycle somewhere.  */
467
 
468
  while (pseg != 0)
469
    {
470
#ifdef DEBUG_I00AFUNC
471
      fprintf (stderr, "%011o %011o\n", pseg, size);
472
#endif
473
      stkl = stkl - pseg;
474
      ssptr = (struct stack_segment_linkage *) stkl;
475
      size = ssptr->sssize;
476
      pseg = ssptr->sspseg;
477
      result += size;
478
    }
479
  return (result);
480
}
481
 
482
#endif /* not CRAY2 */
483
#endif /* CRAY */

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