summaryrefslogtreecommitdiffstats
path: root/contrib/gcc/stupid.c
blob: ed1afcf7dbeae19c7c98c1fba7b4e5ca77b064fc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
/* Dummy data flow analysis for GNU compiler in nonoptimizing mode.
   Copyright (C) 1987, 1991, 1994, 1995 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


/* This file performs stupid register allocation, which is used
   when cc1 gets the -noreg switch (which is when cc does not get -O).

   Stupid register allocation goes in place of the the flow_analysis,
   local_alloc and global_alloc passes.  combine_instructions cannot
   be done with stupid allocation because the data flow info that it needs
   is not computed here.

   In stupid allocation, the only user-defined variables that can
   go in registers are those declared "register".  They are assumed
   to have a life span equal to their scope.  Other user variables
   are given stack slots in the rtl-generation pass and are not
   represented as pseudo regs.  A compiler-generated temporary
   is assumed to live from its first mention to its last mention.

   Since each pseudo-reg's life span is just an interval, it can be
   represented as a pair of numbers, each of which identifies an insn by
   its position in the function (number of insns before it).  The first
   thing done for stupid allocation is to compute such a number for each
   insn.  It is called the suid.  Then the life-interval of each
   pseudo reg is computed.  Then the pseudo regs are ordered by priority
   and assigned hard regs in priority order.  */

#include <stdio.h>
#include "config.h"
#include "rtl.h"
#include "hard-reg-set.h"
#include "regs.h"
#include "flags.h"

/* Vector mapping INSN_UIDs to suids.
   The suids are like uids but increase monotonically always.
   We use them to see whether a subroutine call came
   between a variable's birth and its death.  */

static int *uid_suid;

/* Get the suid of an insn.  */

#define INSN_SUID(INSN) (uid_suid[INSN_UID (INSN)])

/* Record the suid of the last CALL_INSN
   so we can tell whether a pseudo reg crosses any calls.  */

static int last_call_suid;

/* Element N is suid of insn where life span of pseudo reg N ends.
   Element is  0 if register N has not been seen yet on backward scan.  */

static int *reg_where_dead;

/* Element N is suid of insn where life span of pseudo reg N begins.  */

static int *reg_where_born;

/* Numbers of pseudo-regs to be allocated, highest priority first.  */

static int *reg_order;

/* Indexed by reg number (hard or pseudo), nonzero if register is live
   at the current point in the instruction stream.  */

static char *regs_live;

/* Indexed by reg number, nonzero if reg was used in a SUBREG that changes
   its size.  */

static char *regs_change_size;

/* Indexed by insn's suid, the set of hard regs live after that insn.  */

static HARD_REG_SET *after_insn_hard_regs;

/* Record that hard reg REGNO is live after insn INSN.  */

#define MARK_LIVE_AFTER(INSN,REGNO)  \
  SET_HARD_REG_BIT (after_insn_hard_regs[INSN_SUID (INSN)], (REGNO))

static int stupid_reg_compare	PROTO((int *, int *));
static int stupid_find_reg	PROTO((int, enum reg_class, enum machine_mode,
				       int, int, int));
static void stupid_mark_refs	PROTO((rtx, rtx));

/* Stupid life analysis is for the case where only variables declared
   `register' go in registers.  For this case, we mark all
   pseudo-registers that belong to register variables as
   dying in the last instruction of the function, and all other
   pseudo registers as dying in the last place they are referenced.
   Hard registers are marked as dying in the last reference before
   the end or before each store into them.  */

void
stupid_life_analysis (f, nregs, file)
     rtx f;
     int nregs;
     FILE *file;
{
  register int i;
  register rtx last, insn;
  int max_uid, max_suid;

  bzero (regs_ever_live, sizeof regs_ever_live);

  regs_live = (char *) alloca (nregs);

  /* First find the last real insn, and count the number of insns,
     and assign insns their suids.  */

  for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
    if (INSN_UID (insn) > i)
      i = INSN_UID (insn);

  max_uid = i + 1;
  uid_suid = (int *) alloca ((i + 1) * sizeof (int));

  /* Compute the mapping from uids to suids.
     Suids are numbers assigned to insns, like uids,
     except that suids increase monotonically through the code.  */

  last = 0;			/* In case of empty function body */
  for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
    {
      if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
	last = insn;

      INSN_SUID (insn) = ++i;
    }

  last_call_suid = i + 1;
  max_suid = i + 1;

  max_regno = nregs;

  /* Allocate tables to record info about regs.  */

  reg_where_dead = (int *) alloca (nregs * sizeof (int));
  bzero ((char *) reg_where_dead, nregs * sizeof (int));

  reg_where_born = (int *) alloca (nregs * sizeof (int));
  bzero ((char *) reg_where_born, nregs * sizeof (int));

  reg_order = (int *) alloca (nregs * sizeof (int));
  bzero ((char *) reg_order, nregs * sizeof (int));

  regs_change_size = (char *) alloca (nregs * sizeof (char));
  bzero ((char *) regs_change_size, nregs * sizeof (char));

  reg_renumber = (short *) oballoc (nregs * sizeof (short));
  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    reg_renumber[i] = i;

  for (i = FIRST_VIRTUAL_REGISTER; i < max_regno; i++)
    reg_renumber[i] = -1;

  after_insn_hard_regs
    = (HARD_REG_SET *) alloca (max_suid * sizeof (HARD_REG_SET));

  bzero ((char *) after_insn_hard_regs, max_suid * sizeof (HARD_REG_SET));

  /* Allocate and zero out many data structures
     that will record the data from lifetime analysis.  */

  allocate_for_life_analysis ();

  for (i = 0; i < max_regno; i++)
    reg_n_deaths[i] = 1;

  bzero (regs_live, nregs);

  /* Find where each pseudo register is born and dies,
     by scanning all insns from the end to the start
     and noting all mentions of the registers.

     Also find where each hard register is live
     and record that info in after_insn_hard_regs.
     regs_live[I] is 1 if hard reg I is live
     at the current point in the scan.  */

  for (insn = last; insn; insn = PREV_INSN (insn))
    {
      register HARD_REG_SET *p = after_insn_hard_regs + INSN_SUID (insn);

      /* Copy the info in regs_live into the element of after_insn_hard_regs
	 for the current position in the rtl code.  */

      for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
	if (regs_live[i])
	  SET_HARD_REG_BIT (*p, i);

      /* Update which hard regs are currently live
	 and also the birth and death suids of pseudo regs
	 based on the pattern of this insn.  */

      if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
	stupid_mark_refs (PATTERN (insn), insn);

      /* Mark all call-clobbered regs as live after each call insn
	 so that a pseudo whose life span includes this insn
	 will not go in one of them.
	 Then mark those regs as all dead for the continuing scan
	 of the insns before the call.  */

      if (GET_CODE (insn) == CALL_INSN)
	{
	  last_call_suid = INSN_SUID (insn);
	  IOR_HARD_REG_SET (after_insn_hard_regs[last_call_suid],
			    call_used_reg_set);

	  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
	    if (call_used_regs[i])
	      regs_live[i] = 0;

	  /* It is important that this be done after processing the insn's
	     pattern because we want the function result register to still
	     be live if it's also used to pass arguments.  */
	  stupid_mark_refs (CALL_INSN_FUNCTION_USAGE (insn), insn);
	}
    }

  /* Now decide the order in which to allocate the pseudo registers.  */

  for (i = LAST_VIRTUAL_REGISTER + 1; i < max_regno; i++)
    reg_order[i] = i;

  qsort (&reg_order[LAST_VIRTUAL_REGISTER + 1],
	 max_regno - LAST_VIRTUAL_REGISTER - 1, sizeof (int),
	 stupid_reg_compare);

  /* Now, in that order, try to find hard registers for those pseudo regs.  */

  for (i = LAST_VIRTUAL_REGISTER + 1; i < max_regno; i++)
    {
      register int r = reg_order[i];

      /* Some regnos disappear from the rtl.  Ignore them to avoid crash.  */
      if (regno_reg_rtx[r] == 0)
	continue;

      /* Now find the best hard-register class for this pseudo register */
      if (N_REG_CLASSES > 1)
	reg_renumber[r] = stupid_find_reg (reg_n_calls_crossed[r], 
					   reg_preferred_class (r),
					   PSEUDO_REGNO_MODE (r),
					   reg_where_born[r],
					   reg_where_dead[r],
					   regs_change_size[r]);

      /* If no reg available in that class, try alternate class.  */
      if (reg_renumber[r] == -1 && reg_alternate_class (r) != NO_REGS)
	reg_renumber[r] = stupid_find_reg (reg_n_calls_crossed[r],
					   reg_alternate_class (r),
					   PSEUDO_REGNO_MODE (r),
					   reg_where_born[r],
					   reg_where_dead[r],
					   regs_change_size[r]);
    }

  if (file)
    dump_flow_info (file);
}

/* Comparison function for qsort.
   Returns -1 (1) if register *R1P is higher priority than *R2P.  */

static int
stupid_reg_compare (r1p, r2p)
     int *r1p, *r2p;
{
  register int r1 = *r1p, r2 = *r2p;
  register int len1 = reg_where_dead[r1] - reg_where_born[r1];
  register int len2 = reg_where_dead[r2] - reg_where_born[r2];
  int tem;

  tem = len2 - len1;
  if (tem != 0)
    return tem;

  tem = reg_n_refs[r1] - reg_n_refs[r2];
  if (tem != 0)
    return tem;

  /* If regs are equally good, sort by regno,
     so that the results of qsort leave nothing to chance.  */
  return r1 - r2;
}

/* Find a block of SIZE words of hard registers in reg_class CLASS
   that can hold a value of machine-mode MODE
     (but actually we test only the first of the block for holding MODE)
   currently free from after insn whose suid is BIRTH
   through the insn whose suid is DEATH,
   and return the number of the first of them.
   Return -1 if such a block cannot be found.

   If CALL_PRESERVED is nonzero, insist on registers preserved
   over subroutine calls, and return -1 if cannot find such.

   If CHANGES_SIZE is nonzero, it means this register was used as the
   operand of a SUBREG that changes its size.  */

static int
stupid_find_reg (call_preserved, class, mode,
		 born_insn, dead_insn, changes_size)
     int call_preserved;
     enum reg_class class;
     enum machine_mode mode;
     int born_insn, dead_insn;
     int changes_size;
{
  register int i, ins;
#ifdef HARD_REG_SET
  register		/* Declare them register if they are scalars.  */
#endif
    HARD_REG_SET used, this_reg;
#ifdef ELIMINABLE_REGS
  static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
#endif

  COPY_HARD_REG_SET (used,
		     call_preserved ? call_used_reg_set : fixed_reg_set);

#ifdef ELIMINABLE_REGS
  for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
    SET_HARD_REG_BIT (used, eliminables[i].from);
#if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
  SET_HARD_REG_BIT (used, HARD_FRAME_POINTER_REGNUM);
#endif
#else
  SET_HARD_REG_BIT (used, FRAME_POINTER_REGNUM);
#endif

  for (ins = born_insn; ins < dead_insn; ins++)
    IOR_HARD_REG_SET (used, after_insn_hard_regs[ins]);

  IOR_COMPL_HARD_REG_SET (used, reg_class_contents[(int) class]);

#ifdef CLASS_CANNOT_CHANGE_SIZE
  if (changes_size)
    IOR_HARD_REG_SET (used,
		      reg_class_contents[(int) CLASS_CANNOT_CHANGE_SIZE]);
#endif

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    {
#ifdef REG_ALLOC_ORDER
      int regno = reg_alloc_order[i];
#else
      int regno = i;
#endif

      /* If a register has screwy overlap problems,
	 don't use it at all if not optimizing.
	 Actually this is only for the 387 stack register,
	 and it's because subsequent code won't work.  */
#ifdef OVERLAPPING_REGNO_P
      if (OVERLAPPING_REGNO_P (regno))
	continue;
#endif

      if (! TEST_HARD_REG_BIT (used, regno)
	  && HARD_REGNO_MODE_OK (regno, mode))
	{
	  register int j;
	  register int size1 = HARD_REGNO_NREGS (regno, mode);
	  for (j = 1; j < size1 && ! TEST_HARD_REG_BIT (used, regno + j); j++);
	  if (j == size1)
	    {
	      CLEAR_HARD_REG_SET (this_reg);
	      while (--j >= 0)
		SET_HARD_REG_BIT (this_reg, regno + j);
	      for (ins = born_insn; ins < dead_insn; ins++)
		{
		  IOR_HARD_REG_SET (after_insn_hard_regs[ins], this_reg);
		}
	      return regno;
	    }
#ifndef REG_ALLOC_ORDER
	  i += j;		/* Skip starting points we know will lose */
#endif
	}
    }

  return -1;
}

/* Walk X, noting all assignments and references to registers
   and recording what they imply about life spans.
   INSN is the current insn, supplied so we can find its suid.  */

static void
stupid_mark_refs (x, insn)
     rtx x, insn;
{
  register RTX_CODE code;
  register char *fmt;
  register int regno, i;

  if (x == 0)
    return;

  code = GET_CODE (x);

  if (code == SET || code == CLOBBER)
    {
      if (SET_DEST (x) != 0
	  && (GET_CODE (SET_DEST (x)) == REG
	      || (GET_CODE (SET_DEST (x)) == SUBREG
		  && GET_CODE (SUBREG_REG (SET_DEST (x))) == REG
		  && (REGNO (SUBREG_REG (SET_DEST (x)))
		      >= FIRST_PSEUDO_REGISTER))))
	{
	  /* Register is being assigned.  */
	  /* If setting a SUBREG, we treat the entire reg as being set.  */
	  if (GET_CODE (SET_DEST (x)) == SUBREG)
	    regno = REGNO (SUBREG_REG (SET_DEST (x)));
	  else
	    regno = REGNO (SET_DEST (x));

	  /* For hard regs, update the where-live info.  */
	  if (regno < FIRST_PSEUDO_REGISTER)
	    {
	      register int j
		= HARD_REGNO_NREGS (regno, GET_MODE (SET_DEST (x)));

	      while (--j >= 0)
		{
		  regs_ever_live[regno+j] = 1;
		  regs_live[regno+j] = 0;

		  /* The following line is for unused outputs;
		     they do get stored even though never used again.  */
		  MARK_LIVE_AFTER (insn, regno);

		  /* When a hard reg is clobbered, mark it in use
		     just before this insn, so it is live all through.  */
		  if (code == CLOBBER && INSN_SUID (insn) > 0)
		    SET_HARD_REG_BIT (after_insn_hard_regs[INSN_SUID (insn) - 1],
				      regno);
		}
	    }
	  /* For pseudo regs, record where born, where dead, number of
	     times used, and whether live across a call.  */
	  else
	    {
	      /* Update the life-interval bounds of this pseudo reg.  */

	      /* When a pseudo-reg is CLOBBERed, it is born just before
		 the clobbering insn.  When setting, just after.  */
	      int where_born = INSN_SUID (insn) - (code == CLOBBER);

	      reg_where_born[regno] = where_born;

	      /* The reg must live at least one insn even
		 in it is never again used--because it has to go
		 in SOME hard reg.  Mark it as dying after the current
		 insn so that it will conflict with any other outputs of
		 this insn.  */
	      if (reg_where_dead[regno] < where_born + 2)
		{
		  reg_where_dead[regno] = where_born + 2;
		  regs_live[regno] = 1;
		}

	      /* Count the refs of this reg.  */
	      reg_n_refs[regno]++;

	      if (last_call_suid < reg_where_dead[regno])
		reg_n_calls_crossed[regno] += 1;
	    }
	}

      /* Record references from the value being set,
	 or from addresses in the place being set if that's not a reg.
	 If setting a SUBREG, we treat the entire reg as *used*.  */
      if (code == SET)
	{
	  stupid_mark_refs (SET_SRC (x), insn);
	  if (GET_CODE (SET_DEST (x)) != REG)
	    stupid_mark_refs (SET_DEST (x), insn);
	}
      return;
    }

  else if (code == SUBREG
	   && GET_CODE (SUBREG_REG (x)) == REG
	   && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER
	   && (GET_MODE_SIZE (GET_MODE (x))
	       != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
	   && (INTEGRAL_MODE_P (GET_MODE (x))
	       || INTEGRAL_MODE_P (GET_MODE (SUBREG_REG (x)))))
    regs_change_size[REGNO (SUBREG_REG (x))] = 1;

  /* Register value being used, not set.  */

  else if (code == REG)
    {
      regno = REGNO (x);
      if (regno < FIRST_PSEUDO_REGISTER)
	{
	  /* Hard reg: mark it live for continuing scan of previous insns.  */
	  register int j = HARD_REGNO_NREGS (regno, GET_MODE (x));
	  while (--j >= 0)
	    {
	      regs_ever_live[regno+j] = 1;
	      regs_live[regno+j] = 1;
	    }
	}
      else
	{
	  /* Pseudo reg: record first use, last use and number of uses.  */

	  reg_where_born[regno] = INSN_SUID (insn);
	  reg_n_refs[regno]++;
	  if (regs_live[regno] == 0)
	    {
	      regs_live[regno] = 1;
	      reg_where_dead[regno] = INSN_SUID (insn);
	    }
	}
      return;
    }

  /* Recursive scan of all other rtx's.  */

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
	stupid_mark_refs (XEXP (x, i), insn);
      if (fmt[i] == 'E')
	{
	  register int j;
	  for (j = XVECLEN (x, i) - 1; j >= 0; j--)
	    stupid_mark_refs (XVECEXP (x, i, j), insn);
	}
    }
}
OpenPOWER on IntegriCloud