aboutsummaryrefslogtreecommitdiff
path: root/gcc/web.c
blob: 4a9bec0c6e223d5ffc35019c1242e93e67cfa990 (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
/* Web construction code for GNU compiler.
   Contributed by Jan Hubicka.
   Copyright (C) 2001-2019 Free Software Foundation, Inc.

This file is part of GCC.

GCC 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 3, or (at your option) any later
version.

GCC 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 GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

/* Simple optimization pass that splits independent uses of each pseudo,
   increasing effectiveness of other optimizations.  The optimization can
   serve as an example of use for the dataflow module.

   TODO
    - We may use profile information and ignore infrequent use for the
      purpose of web unifying, inserting the compensation code later to
      implement full induction variable expansion for loops (currently
      we expand only if the induction variable is dead afterward, which
      is often the case).  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "rtl.h"
#include "df.h"
#include "insn-config.h"
#include "recog.h"

#include "tree-pass.h"


/* Find the root of unionfind tree (the representative of set).  */

web_entry_base *
web_entry_base::unionfind_root ()
{
  web_entry_base *element = this, *element1 = this, *element2;

  while (element->pred ())
    element = element->pred ();
  while (element1->pred ())
    {
      element2 = element1->pred ();
      element1->set_pred (element);
      element1 = element2;
    }
  return element;
}

/* Union sets.
   Return true if FIRST and SECOND points to the same web entry structure and
   nothing is done.  Otherwise, return false.  */

bool
unionfind_union (web_entry_base *first, web_entry_base *second)
{
  first = first->unionfind_root ();
  second = second->unionfind_root ();
  if (first == second)
    return true;
  second->set_pred (first);
  return false;
}

class web_entry : public web_entry_base
{
 private:
  rtx reg_pvt;

 public:
  rtx reg () { return reg_pvt; }
  void set_reg (rtx r) { reg_pvt = r; }
};

/* For INSN, union all defs and uses that are linked by match_dup.
   FUN is the function that does the union.  */

static void
union_match_dups (rtx_insn *insn, web_entry *def_entry, web_entry *use_entry,
		  bool (*fun) (web_entry_base *, web_entry_base *))
{
  struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
  df_ref use_link = DF_INSN_INFO_USES (insn_info);
  df_ref def_link = DF_INSN_INFO_DEFS (insn_info);
  struct web_entry *dup_entry;
  int i;

  extract_insn (insn);

  for (i = 0; i < recog_data.n_dups; i++)
    {
      int op = recog_data.dup_num[i];
      enum op_type type = recog_data.operand_type[op];
      df_ref ref, dupref;
      struct web_entry *entry;

      dup_entry = use_entry;
      for (dupref = use_link; dupref; dupref = DF_REF_NEXT_LOC (dupref))
	if (DF_REF_LOC (dupref) == recog_data.dup_loc[i])
	  break;

      if (dupref == NULL && type == OP_INOUT)
	{
	  dup_entry = def_entry;
	  for (dupref = def_link; dupref; dupref = DF_REF_NEXT_LOC (dupref))
	    if (DF_REF_LOC (dupref) == recog_data.dup_loc[i])
	      break;
	}
      /* ??? *DUPREF can still be zero, because when an operand matches
	 a memory, DF_REF_LOC (use_link[n]) points to the register part
	 of the address, whereas recog_data.dup_loc[m] points to the
	 entire memory ref, thus we fail to find the duplicate entry,
         even though it is there.
         Example: i686-pc-linux-gnu gcc.c-torture/compile/950607-1.c
		  -O3 -fomit-frame-pointer -funroll-loops  */
      if (dupref == NULL
	  || DF_REF_REGNO (dupref) < FIRST_PSEUDO_REGISTER)
	continue;

      ref = type == OP_IN ? use_link : def_link;
      entry = type == OP_IN ? use_entry : def_entry;
      for (; ref; ref = DF_REF_NEXT_LOC (ref))
	{
	  rtx *l = DF_REF_LOC (ref);
	  if (l == recog_data.operand_loc[op])
	    break;
	  if (l && DF_REF_REAL_LOC (ref) == recog_data.operand_loc[op])
	    break;
	}

      if (!ref && type == OP_INOUT)
	{
	  entry = use_entry;
	  for (ref = use_link; ref; ref = DF_REF_NEXT_LOC (ref))
	    {
	      rtx *l = DF_REF_LOC (ref);
	      if (l == recog_data.operand_loc[op])
		break;
	      if (l && DF_REF_REAL_LOC (ref) == recog_data.operand_loc[op])
		break;
	    }
	}

      gcc_assert (ref);
      (*fun) (dup_entry + DF_REF_ID (dupref), entry + DF_REF_ID (ref));
    }
}

/* For each use, all possible defs reaching it must come in the same
   register, union them.
   FUN is the function that does the union.

   In USED, we keep the DF_REF_ID of the first uninitialized uses of a
   register, so that all uninitialized uses of the register can be
   combined into a single web.  We actually offset it by 2, because
   the values 0 and 1 are reserved for use by entry_register.  */

void
union_defs (df_ref use, web_entry *def_entry,
	    unsigned int *used, web_entry *use_entry,
 	    bool (*fun) (web_entry_base *, web_entry_base *))
{
  struct df_insn_info *insn_info = DF_REF_INSN_INFO (use);
  struct df_link *link = DF_REF_CHAIN (use);
  rtx set;

  if (insn_info)
    {
      df_ref eq_use;

      set = single_set (insn_info->insn);
      FOR_EACH_INSN_INFO_EQ_USE (eq_use, insn_info)
	if (use != eq_use
	    && DF_REF_REAL_REG (use) == DF_REF_REAL_REG (eq_use))
	  (*fun) (use_entry + DF_REF_ID (use), use_entry + DF_REF_ID (eq_use));
    }
  else
    set = NULL;

  /* Union all occurrences of the same register in reg notes.  */

  /* Recognize trivial noop moves and attempt to keep them as noop.  */

  if (set
      && SET_SRC (set) == DF_REF_REG (use)
      && SET_SRC (set) == SET_DEST (set))
    {
      df_ref def;

      FOR_EACH_INSN_INFO_DEF (def, insn_info)
	if (DF_REF_REAL_REG (use) == DF_REF_REAL_REG (def))
	  (*fun) (use_entry + DF_REF_ID (use), def_entry + DF_REF_ID (def));
    }

  /* UD chains of uninitialized REGs are empty.  Keeping all uses of
     the same uninitialized REG in a single web is not necessary for
     correctness, since the uses are undefined, but it's wasteful to
     allocate one register or slot for each reference.  Furthermore,
     creating new pseudos for uninitialized references in debug insns
     (see PR 42631) causes -fcompare-debug failures.  We record the
     number of the first uninitialized reference we found, and merge
     with it any other uninitialized references to the same
     register.  */
  if (!link)
    {
      int regno = REGNO (DF_REF_REAL_REG (use));
      if (used[regno])
	(*fun) (use_entry + DF_REF_ID (use), use_entry + used[regno] - 2);
      else
	used[regno] = DF_REF_ID (use) + 2;
    }

  while (link)
    {
      (*fun) (use_entry + DF_REF_ID (use),
	      def_entry + DF_REF_ID (link->ref));
      link = link->next;
    }

  /* A READ_WRITE use requires the corresponding def to be in the same
     register.  Find it and union.  */
  if (DF_REF_FLAGS (use) & DF_REF_READ_WRITE)
    if (insn_info)
      {
	df_ref def;

	FOR_EACH_INSN_INFO_DEF (def, insn_info)
	  if (DF_REF_REAL_REG (use) == DF_REF_REAL_REG (def))
	    (*fun) (use_entry + DF_REF_ID (use), def_entry + DF_REF_ID (def));
      }
}

/* Find the corresponding register for the given entry.  */

static rtx
entry_register (web_entry *entry, df_ref ref, unsigned int *used)
{
  web_entry *root;
  rtx reg, newreg;

  /* Find the corresponding web and see if it has been visited.  */
  root = (web_entry *)entry->unionfind_root ();
  if (root->reg ())
    return root->reg ();

  /* We are seeing this web for the first time, do the assignment.  */
  reg = DF_REF_REAL_REG (ref);

  /* In case the original register is already assigned, generate new
     one.  Since we use USED to merge uninitialized refs into a single
     web, we might found an element to be nonzero without our having
     used it.  Test for 1, because union_defs saves it for our use,
     and there won't be any use for the other values when we get to
     this point.  */
  if (used[REGNO (reg)] != 1)
    newreg = reg, used[REGNO (reg)] = 1;
  else
    {
      newreg = gen_reg_rtx (GET_MODE (reg));
      REG_USERVAR_P (newreg) = REG_USERVAR_P (reg);
      REG_POINTER (newreg) = REG_POINTER (reg);
      REG_ATTRS (newreg) = REG_ATTRS (reg);
      if (dump_file)
	fprintf (dump_file, "Web oldreg=%i newreg=%i\n", REGNO (reg),
		 REGNO (newreg));
    }

  root->set_reg (newreg);
  return newreg;
}

/* Replace the reference by REG.  */

static void
replace_ref (df_ref ref, rtx reg)
{
  rtx oldreg = DF_REF_REAL_REG (ref);
  rtx *loc = DF_REF_REAL_LOC (ref);
  unsigned int uid = DF_REF_INSN_UID (ref);

  if (oldreg == reg)
    return;
  if (dump_file)
    fprintf (dump_file, "Updating insn %i (%i->%i)\n",
	     uid, REGNO (oldreg), REGNO (reg));
  *loc = reg;
  df_insn_rescan (DF_REF_INSN (ref));
}


namespace {

const pass_data pass_data_web =
{
  RTL_PASS, /* type */
  "web", /* name */
  OPTGROUP_NONE, /* optinfo_flags */
  TV_WEB, /* tv_id */
  0, /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  TODO_df_finish, /* todo_flags_finish */
};

class pass_web : public rtl_opt_pass
{
public:
  pass_web (gcc::context *ctxt)
    : rtl_opt_pass (pass_data_web, ctxt)
  {}

  /* opt_pass methods: */
  virtual bool gate (function *) { return (optimize > 0 && flag_web); }
  virtual unsigned int execute (function *);

}; // class pass_web

unsigned int
pass_web::execute (function *fun)
{
  web_entry *def_entry;
  web_entry *use_entry;
  unsigned int max = max_reg_num ();
  unsigned int *used;
  basic_block bb;
  unsigned int uses_num = 0;
  rtx_insn *insn;

  df_set_flags (DF_NO_HARD_REGS + DF_EQ_NOTES);
  df_set_flags (DF_RD_PRUNE_DEAD_DEFS);
  df_chain_add_problem (DF_UD_CHAIN);
  df_analyze ();
  df_set_flags (DF_DEFER_INSN_RESCAN);

  /* Assign ids to the uses.  */
  FOR_ALL_BB_FN (bb, fun)
    FOR_BB_INSNS (bb, insn)
    {
      if (NONDEBUG_INSN_P (insn))
	{
	  struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
	  df_ref use;
	  FOR_EACH_INSN_INFO_USE (use, insn_info)
	    if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
	      DF_REF_ID (use) = uses_num++;
	  FOR_EACH_INSN_INFO_EQ_USE (use, insn_info)
	    if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
	      DF_REF_ID (use) = uses_num++;
	}
    }

  /* Record the number of uses and defs at the beginning of the optimization.  */
  def_entry = XCNEWVEC (web_entry, DF_DEFS_TABLE_SIZE ());
  used = XCNEWVEC (unsigned, max);
  use_entry = XCNEWVEC (web_entry, uses_num);

  /* Produce the web.  */
  FOR_ALL_BB_FN (bb, fun)
    FOR_BB_INSNS (bb, insn)
      if (NONDEBUG_INSN_P (insn))
	{
	  struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
	  df_ref use;
	  union_match_dups (insn, def_entry, use_entry, unionfind_union);
	  FOR_EACH_INSN_INFO_USE (use, insn_info)
	    if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
	      union_defs (use, def_entry, used, use_entry, unionfind_union);
	  FOR_EACH_INSN_INFO_EQ_USE (use, insn_info)
	    if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
	      union_defs (use, def_entry, used, use_entry, unionfind_union);
	}

  /* Update the instruction stream, allocating new registers for split pseudos
     in progress.  */
  FOR_ALL_BB_FN (bb, fun)
    FOR_BB_INSNS (bb, insn)
      if (NONDEBUG_INSN_P (insn)
	  /* Ignore naked clobber.  For example, reg 134 in the second insn
	     of the following sequence will not be replaced.

	       (insn (clobber (reg:SI 134)))

	       (insn (set (reg:SI 0 r0) (reg:SI 134)))

	     Thus the later passes can optimize them away.  */
	  && GET_CODE (PATTERN (insn)) != CLOBBER)
	{
	  struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
	  df_ref def, use;
	  FOR_EACH_INSN_INFO_USE (use, insn_info)
	    if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
	      replace_ref (use, entry_register (use_entry + DF_REF_ID (use),
						use, used));
	  FOR_EACH_INSN_INFO_EQ_USE (use, insn_info)
	    if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
	      replace_ref (use, entry_register (use_entry + DF_REF_ID (use),
						use, used));
	  FOR_EACH_INSN_INFO_DEF (def, insn_info)
	    if (DF_REF_REGNO (def) >= FIRST_PSEUDO_REGISTER)
	      replace_ref (def, entry_register (def_entry + DF_REF_ID (def),
						def, used));
	}

  free (def_entry);
  free (use_entry);
  free (used);
  return 0;
}

} // anon namespace

rtl_opt_pass *
make_pass_web (gcc::context *ctxt)
{
  return new pass_web (ctxt);
}