150476Speter/* Web construction code for GNU compiler.
22006Swollman   Contributed by Jan Hubicka.
32006Swollman   Copyright (C) 2001, 2002, 2004, 2006, 2007, 2008, 2010
4276486Sngie   Free Software Foundation, Inc.
52006Swollman
62006SwollmanThis file is part of GCC.
72006Swollman
82006SwollmanGCC is free software; you can redistribute it and/or modify it under
9the terms of the GNU General Public License as published by the Free
10Software Foundation; either version 3, or (at your option) any later
11version.
12
13GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14WARRANTY; without even the implied warranty of MERCHANTABILITY or
15FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
16for more details.
17
18You should have received a copy of the GNU General Public License
19along with GCC; see the file COPYING3.  If not see
20<http://www.gnu.org/licenses/>.  */
21
22/* Simple optimization pass that splits independent uses of each pseudo,
23   increasing effectiveness of other optimizations.  The optimization can
24   serve as an example of use for the dataflow module.
25
26   We don't split registers with REG_USERVAR set unless -fmessy-debugging
27   is specified, because debugging information about such split variables
28   is almost unusable.
29
30   TODO
31    - We may use profile information and ignore infrequent use for the
32      purpose of web unifying, inserting the compensation code later to
33      implement full induction variable expansion for loops (currently
34      we expand only if the induction variable is dead afterward, which
35      is often the case).  */
36
37#include "config.h"
38#include "system.h"
39#include "coretypes.h"
40#include "tm.h"
41#include "toplev.h"
42
43#include "rtl.h"
44#include "hard-reg-set.h"
45#include "flags.h"
46#include "obstack.h"
47#include "basic-block.h"
48#include "output.h"
49#include "df.h"
50#include "function.h"
51#include "timevar.h"
52#include "tree-pass.h"
53
54
55/* Find the root of unionfind tree (the representative of set).  */
56
57struct web_entry *
58unionfind_root (struct web_entry *element)
59{
60  struct web_entry *element1 = element, *element2;
61
62  while (element->pred)
63    element = element->pred;
64  while (element1->pred)
65    {
66      element2 = element1->pred;
67      element1->pred = element;
68      element1 = element2;
69    }
70  return element;
71}
72
73/* Union sets.
74   Return true if FIRST and SECOND points to the same web entry structure and
75   nothing is done.  Otherwise, return false.  */
76
77bool
78unionfind_union (struct web_entry *first, struct web_entry *second)
79{
80  first = unionfind_root (first);
81  second = unionfind_root (second);
82  if (first == second)
83    return true;
84  second->pred = first;
85  return false;
86}
87
88/* For each use, all possible defs reaching it must come in the same
89   register, union them.
90   FUN is the function that does the union.
91
92   In USED, we keep the DF_REF_ID of the first uninitialized uses of a
93   register, so that all uninitialized uses of the register can be
94   combined into a single web.  We actually offset it by 2, because
95   the values 0 and 1 are reserved for use by entry_register.  */
96
97void
98union_defs (df_ref use, struct web_entry *def_entry,
99	    unsigned int *used, struct web_entry *use_entry,
100 	    bool (*fun) (struct web_entry *, struct web_entry *))
101{
102  struct df_insn_info *insn_info = DF_REF_INSN_INFO (use);
103  struct df_link *link = DF_REF_CHAIN (use);
104  df_ref *use_link;
105  df_ref *eq_use_link;
106  df_ref *def_link;
107  rtx set;
108
109  if (insn_info)
110    {
111      rtx insn = insn_info->insn;
112      use_link = DF_INSN_INFO_USES (insn_info);
113      eq_use_link = DF_INSN_INFO_EQ_USES (insn_info);
114      def_link = DF_INSN_INFO_DEFS (insn_info);
115      set = single_set (insn);
116    }
117  else
118    {
119      /* An artificial use.  It links up with nothing.  */
120      use_link = NULL;
121      eq_use_link = NULL;
122      def_link = NULL;
123      set = NULL;
124    }
125
126  /* Some instructions may use match_dup for their operands.  In case the
127     operands are dead, we will assign them different pseudos, creating
128     invalid instructions, so union all uses of the same operand for each
129     insn.  */
130
131  if (use_link)
132    while (*use_link)
133      {
134	if (use != *use_link
135	    && DF_REF_REAL_REG (use) == DF_REF_REAL_REG (*use_link))
136	  (*fun) (use_entry + DF_REF_ID (use),
137		  use_entry + DF_REF_ID (*use_link));
138	use_link++;
139      }
140
141  if (eq_use_link)
142    while (*eq_use_link)
143      {
144	if (use != *eq_use_link
145	    && DF_REF_REAL_REG (use) == DF_REF_REAL_REG (*eq_use_link))
146	  (*fun) (use_entry + DF_REF_ID (use),
147		  use_entry + DF_REF_ID (*eq_use_link));
148	eq_use_link++;
149    }
150
151  /* Recognize trivial noop moves and attempt to keep them as noop.  */
152
153  if (set
154      && SET_SRC (set) == DF_REF_REG (use)
155      && SET_SRC (set) == SET_DEST (set))
156    {
157      if (def_link)
158	while (*def_link)
159	  {
160	    if (DF_REF_REAL_REG (use) == DF_REF_REAL_REG (*def_link))
161	      (*fun) (use_entry + DF_REF_ID (use),
162		      def_entry + DF_REF_ID (*def_link));
163	    def_link++;
164	  }
165    }
166
167  /* UD chains of uninitialized REGs are empty.  Keeping all uses of
168     the same uninitialized REG in a single web is not necessary for
169     correctness, since the uses are undefined, but it's wasteful to
170     allocate one register or slot for each reference.  Furthermore,
171     creating new pseudos for uninitialized references in debug insns
172     (see PR 42631) causes -fcompare-debug failures.  We record the
173     number of the first uninitialized reference we found, and merge
174     with it any other uninitialized references to the same
175     register.  */
176  if (!link)
177    {
178      int regno = REGNO (DF_REF_REAL_REG (use));
179      if (used[regno])
180	(*fun) (use_entry + DF_REF_ID (use), use_entry + used[regno] - 2);
181      else
182	used[regno] = DF_REF_ID (use) + 2;
183    }
184
185  while (link)
186    {
187      (*fun) (use_entry + DF_REF_ID (use),
188	      def_entry + DF_REF_ID (link->ref));
189      link = link->next;
190    }
191
192  /* A READ_WRITE use requires the corresponding def to be in the same
193     register.  Find it and union.  */
194  if (DF_REF_FLAGS (use) & DF_REF_READ_WRITE)
195    {
196      df_ref *link;
197
198      if (insn_info)
199	link = DF_INSN_INFO_DEFS (insn_info);
200      else
201	link = NULL;
202
203      if (link)
204	while (*link)
205	  {
206	    if (DF_REF_REAL_REG (*link) == DF_REF_REAL_REG (use))
207	      (*fun) (use_entry + DF_REF_ID (use),
208		      def_entry + DF_REF_ID (*link));
209	    link++;
210	  }
211    }
212}
213
214/* Find the corresponding register for the given entry.  */
215
216static rtx
217entry_register (struct web_entry *entry, df_ref ref, unsigned int *used)
218{
219  struct web_entry *root;
220  rtx reg, newreg;
221
222  /* Find the corresponding web and see if it has been visited.  */
223  root = unionfind_root (entry);
224  if (root->reg)
225    return root->reg;
226
227  /* We are seeing this web for the first time, do the assignment.  */
228  reg = DF_REF_REAL_REG (ref);
229
230  /* In case the original register is already assigned, generate new
231     one.  Since we use USED to merge uninitialized refs into a single
232     web, we might found an element to be nonzero without our having
233     used it.  Test for 1, because union_defs saves it for our use,
234     and there won't be any use for the other values when we get to
235     this point.  */
236  if (used[REGNO (reg)] != 1)
237    newreg = reg, used[REGNO (reg)] = 1;
238  else
239    {
240      newreg = gen_reg_rtx (GET_MODE (reg));
241      REG_USERVAR_P (newreg) = REG_USERVAR_P (reg);
242      REG_POINTER (newreg) = REG_POINTER (reg);
243      REG_ATTRS (newreg) = REG_ATTRS (reg);
244      if (dump_file)
245	fprintf (dump_file, "Web oldreg=%i newreg=%i\n", REGNO (reg),
246		 REGNO (newreg));
247    }
248
249  root->reg = newreg;
250  return newreg;
251}
252
253/* Replace the reference by REG.  */
254
255static void
256replace_ref (df_ref ref, rtx reg)
257{
258  rtx oldreg = DF_REF_REAL_REG (ref);
259  rtx *loc = DF_REF_REAL_LOC (ref);
260  unsigned int uid = DF_REF_INSN_UID (ref);
261
262  if (oldreg == reg)
263    return;
264  if (dump_file)
265    fprintf (dump_file, "Updating insn %i (%i->%i)\n",
266	     uid, REGNO (oldreg), REGNO (reg));
267  *loc = reg;
268  df_insn_rescan (DF_REF_INSN (ref));
269}
270
271
272static bool
273gate_handle_web (void)
274{
275  return (optimize > 0 && flag_web);
276}
277
278/* Main entry point.  */
279
280static unsigned int
281web_main (void)
282{
283  struct web_entry *def_entry;
284  struct web_entry *use_entry;
285  unsigned int max = max_reg_num ();
286  unsigned int *used;
287  basic_block bb;
288  unsigned int uses_num = 0;
289  rtx insn;
290
291  df_set_flags (DF_NO_HARD_REGS + DF_EQ_NOTES);
292  df_chain_add_problem (DF_UD_CHAIN);
293  df_analyze ();
294  df_set_flags (DF_DEFER_INSN_RESCAN);
295
296  /* Assign ids to the uses.  */
297  FOR_ALL_BB (bb)
298    FOR_BB_INSNS (bb, insn)
299    {
300      unsigned int uid = INSN_UID (insn);
301      if (NONDEBUG_INSN_P (insn))
302	{
303	  df_ref *use_rec;
304	  for (use_rec = DF_INSN_UID_USES (uid); *use_rec; use_rec++)
305	    {
306	      df_ref use = *use_rec;
307	      if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
308		DF_REF_ID (use) = uses_num++;
309	    }
310	  for (use_rec = DF_INSN_UID_EQ_USES (uid); *use_rec; use_rec++)
311	    {
312	      df_ref use = *use_rec;
313	      if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
314		DF_REF_ID (use) = uses_num++;
315	    }
316	}
317    }
318
319  /* Record the number of uses and defs at the beginning of the optimization.  */
320  def_entry = XCNEWVEC (struct web_entry, DF_DEFS_TABLE_SIZE());
321  used = XCNEWVEC (unsigned, max);
322  use_entry = XCNEWVEC (struct web_entry, uses_num);
323
324  /* Produce the web.  */
325  FOR_ALL_BB (bb)
326    FOR_BB_INSNS (bb, insn)
327    {
328      unsigned int uid = INSN_UID (insn);
329      if (NONDEBUG_INSN_P (insn))
330	{
331	  df_ref *use_rec;
332	  for (use_rec = DF_INSN_UID_USES (uid); *use_rec; use_rec++)
333	    {
334	      df_ref use = *use_rec;
335	      if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
336		union_defs (use, def_entry, used, use_entry, unionfind_union);
337	    }
338	  for (use_rec = DF_INSN_UID_EQ_USES (uid); *use_rec; use_rec++)
339	    {
340	      df_ref use = *use_rec;
341	      if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
342		union_defs (use, def_entry, used, use_entry, unionfind_union);
343	    }
344	}
345    }
346
347  /* Update the instruction stream, allocating new registers for split pseudos
348     in progress.  */
349  FOR_ALL_BB (bb)
350    FOR_BB_INSNS (bb, insn)
351    {
352      unsigned int uid = INSN_UID (insn);
353      if (NONDEBUG_INSN_P (insn))
354	{
355	  df_ref *use_rec;
356	  df_ref *def_rec;
357	  for (use_rec = DF_INSN_UID_USES (uid); *use_rec; use_rec++)
358	    {
359	      df_ref use = *use_rec;
360	      if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
361		replace_ref (use, entry_register (use_entry + DF_REF_ID (use), use, used));
362	    }
363	  for (use_rec = DF_INSN_UID_EQ_USES (uid); *use_rec; use_rec++)
364	    {
365	      df_ref use = *use_rec;
366	      if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
367		replace_ref (use, entry_register (use_entry + DF_REF_ID (use), use, used));
368	    }
369	  for (def_rec = DF_INSN_UID_DEFS (uid); *def_rec; def_rec++)
370	    {
371	      df_ref def = *def_rec;
372	      if (DF_REF_REGNO (def) >= FIRST_PSEUDO_REGISTER)
373		replace_ref (def, entry_register (def_entry + DF_REF_ID (def), def, used));
374	    }
375	}
376    }
377
378  free (def_entry);
379  free (use_entry);
380  free (used);
381  return 0;
382}
383
384struct rtl_opt_pass pass_web =
385{
386 {
387  RTL_PASS,
388  "web",                                /* name */
389  gate_handle_web,                      /* gate */
390  web_main,		                /* execute */
391  NULL,                                 /* sub */
392  NULL,                                 /* next */
393  0,                                    /* static_pass_number */
394  TV_WEB,                               /* tv_id */
395  0,                                    /* properties_required */
396  0,                                    /* properties_provided */
397  0,                                    /* properties_destroyed */
398  0,                                    /* todo_flags_start */
399  TODO_df_finish | TODO_verify_rtl_sharing |
400  TODO_dump_func                        /* todo_flags_finish */
401 }
402};
403
404