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comparison gcc/tree-ssa-copyrename.c @ 0:a06113de4d67
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author | kent <kent@cr.ie.u-ryukyu.ac.jp> |
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date | Fri, 17 Jul 2009 14:47:48 +0900 |
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children | 77e2b8dfacca |
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1 /* Rename SSA copies. | |
2 Copyright (C) 2004, 2006, 2007, 2008 Free Software Foundation, Inc. | |
3 Contributed by Andrew MacLeod <amacleod@redhat.com> | |
4 | |
5 This file is part of GCC. | |
6 | |
7 GCC is free software; you can redistribute it and/or modify | |
8 it under the terms of the GNU General Public License as published by | |
9 the Free Software Foundation; either version 3, or (at your option) | |
10 any later version. | |
11 | |
12 GCC is distributed in the hope that it will be useful, | |
13 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 GNU General Public License for more details. | |
16 | |
17 You should have received a copy of the GNU General Public License | |
18 along with GCC; see the file COPYING3. If not see | |
19 <http://www.gnu.org/licenses/>. */ | |
20 | |
21 #include "config.h" | |
22 #include "system.h" | |
23 #include "coretypes.h" | |
24 #include "tm.h" | |
25 #include "tree.h" | |
26 #include "gimple.h" | |
27 #include "flags.h" | |
28 #include "basic-block.h" | |
29 #include "function.h" | |
30 #include "diagnostic.h" | |
31 #include "bitmap.h" | |
32 #include "tree-flow.h" | |
33 #include "gimple.h" | |
34 #include "tree-inline.h" | |
35 #include "timevar.h" | |
36 #include "hashtab.h" | |
37 #include "tree-dump.h" | |
38 #include "tree-ssa-live.h" | |
39 #include "tree-pass.h" | |
40 #include "langhooks.h" | |
41 | |
42 /* The following routines implement the SSA copy renaming phase. | |
43 | |
44 This optimization looks for copies between 2 SSA_NAMES, either through a | |
45 direct copy, or an implicit one via a PHI node result and its arguments. | |
46 | |
47 Each copy is examined to determine if it is possible to rename the base | |
48 variable of one of the operands to the same variable as the other operand. | |
49 i.e. | |
50 T.3_5 = <blah> | |
51 a_1 = T.3_5 | |
52 | |
53 If this copy couldn't be copy propagated, it could possibly remain in the | |
54 program throughout the optimization phases. After SSA->normal, it would | |
55 become: | |
56 | |
57 T.3 = <blah> | |
58 a = T.3 | |
59 | |
60 Since T.3_5 is distinct from all other SSA versions of T.3, there is no | |
61 fundamental reason why the base variable needs to be T.3, subject to | |
62 certain restrictions. This optimization attempts to determine if we can | |
63 change the base variable on copies like this, and result in code such as: | |
64 | |
65 a_5 = <blah> | |
66 a_1 = a_5 | |
67 | |
68 This gives the SSA->normal pass a shot at coalescing a_1 and a_5. If it is | |
69 possible, the copy goes away completely. If it isn't possible, a new temp | |
70 will be created for a_5, and you will end up with the exact same code: | |
71 | |
72 a.8 = <blah> | |
73 a = a.8 | |
74 | |
75 The other benefit of performing this optimization relates to what variables | |
76 are chosen in copies. Gimplification of the program uses temporaries for | |
77 a lot of things. expressions like | |
78 | |
79 a_1 = <blah> | |
80 <blah2> = a_1 | |
81 | |
82 get turned into | |
83 | |
84 T.3_5 = <blah> | |
85 a_1 = T.3_5 | |
86 <blah2> = a_1 | |
87 | |
88 Copy propagation is done in a forward direction, and if we can propagate | |
89 through the copy, we end up with: | |
90 | |
91 T.3_5 = <blah> | |
92 <blah2> = T.3_5 | |
93 | |
94 The copy is gone, but so is all reference to the user variable 'a'. By | |
95 performing this optimization, we would see the sequence: | |
96 | |
97 a_5 = <blah> | |
98 a_1 = a_5 | |
99 <blah2> = a_1 | |
100 | |
101 which copy propagation would then turn into: | |
102 | |
103 a_5 = <blah> | |
104 <blah2> = a_5 | |
105 | |
106 and so we still retain the user variable whenever possible. */ | |
107 | |
108 | |
109 /* Coalesce the partitions in MAP representing VAR1 and VAR2 if it is valid. | |
110 Choose a representative for the partition, and send debug info to DEBUG. */ | |
111 | |
112 static bool | |
113 copy_rename_partition_coalesce (var_map map, tree var1, tree var2, FILE *debug) | |
114 { | |
115 int p1, p2, p3; | |
116 tree root1, root2; | |
117 tree rep1, rep2; | |
118 var_ann_t ann1, ann2, ann3; | |
119 bool ign1, ign2, abnorm; | |
120 | |
121 gcc_assert (TREE_CODE (var1) == SSA_NAME); | |
122 gcc_assert (TREE_CODE (var2) == SSA_NAME); | |
123 | |
124 register_ssa_partition (map, var1); | |
125 register_ssa_partition (map, var2); | |
126 | |
127 p1 = partition_find (map->var_partition, SSA_NAME_VERSION (var1)); | |
128 p2 = partition_find (map->var_partition, SSA_NAME_VERSION (var2)); | |
129 | |
130 if (debug) | |
131 { | |
132 fprintf (debug, "Try : "); | |
133 print_generic_expr (debug, var1, TDF_SLIM); | |
134 fprintf (debug, "(P%d) & ", p1); | |
135 print_generic_expr (debug, var2, TDF_SLIM); | |
136 fprintf (debug, "(P%d)", p2); | |
137 } | |
138 | |
139 gcc_assert (p1 != NO_PARTITION); | |
140 gcc_assert (p2 != NO_PARTITION); | |
141 | |
142 rep1 = partition_to_var (map, p1); | |
143 rep2 = partition_to_var (map, p2); | |
144 root1 = SSA_NAME_VAR (rep1); | |
145 root2 = SSA_NAME_VAR (rep2); | |
146 | |
147 ann1 = var_ann (root1); | |
148 ann2 = var_ann (root2); | |
149 | |
150 if (p1 == p2) | |
151 { | |
152 if (debug) | |
153 fprintf (debug, " : Already coalesced.\n"); | |
154 return false; | |
155 } | |
156 | |
157 /* Don't coalesce if one of the variables occurs in an abnormal PHI. */ | |
158 abnorm = (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rep1) | |
159 || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rep2)); | |
160 if (abnorm) | |
161 { | |
162 if (debug) | |
163 fprintf (debug, " : Abnormal PHI barrier. No coalesce.\n"); | |
164 return false; | |
165 } | |
166 | |
167 /* Partitions already have the same root, simply merge them. */ | |
168 if (root1 == root2) | |
169 { | |
170 p1 = partition_union (map->var_partition, p1, p2); | |
171 if (debug) | |
172 fprintf (debug, " : Same root, coalesced --> P%d.\n", p1); | |
173 return false; | |
174 } | |
175 | |
176 /* Never attempt to coalesce 2 difference parameters. */ | |
177 if (TREE_CODE (root1) == PARM_DECL && TREE_CODE (root2) == PARM_DECL) | |
178 { | |
179 if (debug) | |
180 fprintf (debug, " : 2 different PARM_DECLS. No coalesce.\n"); | |
181 return false; | |
182 } | |
183 | |
184 if ((TREE_CODE (root1) == RESULT_DECL) != (TREE_CODE (root2) == RESULT_DECL)) | |
185 { | |
186 if (debug) | |
187 fprintf (debug, " : One root a RESULT_DECL. No coalesce.\n"); | |
188 return false; | |
189 } | |
190 | |
191 ign1 = TREE_CODE (root1) == VAR_DECL && DECL_IGNORED_P (root1); | |
192 ign2 = TREE_CODE (root2) == VAR_DECL && DECL_IGNORED_P (root2); | |
193 | |
194 /* Never attempt to coalesce 2 user variables unless one is an inline | |
195 variable. */ | |
196 if (!ign1 && !ign2) | |
197 { | |
198 if (DECL_FROM_INLINE (root2)) | |
199 ign2 = true; | |
200 else if (DECL_FROM_INLINE (root1)) | |
201 ign1 = true; | |
202 else | |
203 { | |
204 if (debug) | |
205 fprintf (debug, " : 2 different USER vars. No coalesce.\n"); | |
206 return false; | |
207 } | |
208 } | |
209 | |
210 /* Don't coalesce if there are two different memory tags. */ | |
211 if (ann1->symbol_mem_tag | |
212 && ann2->symbol_mem_tag | |
213 && ann1->symbol_mem_tag != ann2->symbol_mem_tag) | |
214 { | |
215 if (debug) | |
216 fprintf (debug, " : 2 memory tags. No coalesce.\n"); | |
217 return false; | |
218 } | |
219 | |
220 /* If both values have default defs, we can't coalesce. If only one has a | |
221 tag, make sure that variable is the new root partition. */ | |
222 if (gimple_default_def (cfun, root1)) | |
223 { | |
224 if (gimple_default_def (cfun, root2)) | |
225 { | |
226 if (debug) | |
227 fprintf (debug, " : 2 default defs. No coalesce.\n"); | |
228 return false; | |
229 } | |
230 else | |
231 { | |
232 ign2 = true; | |
233 ign1 = false; | |
234 } | |
235 } | |
236 else if (gimple_default_def (cfun, root2)) | |
237 { | |
238 ign1 = true; | |
239 ign2 = false; | |
240 } | |
241 | |
242 /* Don't coalesce if the two variables aren't type compatible. */ | |
243 if (!types_compatible_p (TREE_TYPE (root1), TREE_TYPE (root2))) | |
244 { | |
245 if (debug) | |
246 fprintf (debug, " : Incompatible types. No coalesce.\n"); | |
247 return false; | |
248 } | |
249 | |
250 /* Don't coalesce if the aliasing sets of the types are different. */ | |
251 if (POINTER_TYPE_P (TREE_TYPE (root1)) | |
252 && POINTER_TYPE_P (TREE_TYPE (root2)) | |
253 && ((get_alias_set (TREE_TYPE (TREE_TYPE (root1))) | |
254 != get_alias_set (TREE_TYPE (TREE_TYPE (root2)))) | |
255 || ((DECL_P (root1) && !MTAG_P (root1)) | |
256 && (DECL_P (root2) && !MTAG_P (root2)) | |
257 && DECL_NO_TBAA_P (root1) != DECL_NO_TBAA_P (root2)))) | |
258 { | |
259 if (debug) | |
260 fprintf (debug, " : 2 different aliasing sets. No coalesce.\n"); | |
261 return false; | |
262 } | |
263 | |
264 | |
265 /* Merge the two partitions. */ | |
266 p3 = partition_union (map->var_partition, p1, p2); | |
267 | |
268 /* Set the root variable of the partition to the better choice, if there is | |
269 one. */ | |
270 if (!ign2) | |
271 replace_ssa_name_symbol (partition_to_var (map, p3), root2); | |
272 else if (!ign1) | |
273 replace_ssa_name_symbol (partition_to_var (map, p3), root1); | |
274 | |
275 /* Update the various flag widgitry of the current base representative. */ | |
276 ann3 = var_ann (SSA_NAME_VAR (partition_to_var (map, p3))); | |
277 if (ann1->symbol_mem_tag) | |
278 ann3->symbol_mem_tag = ann1->symbol_mem_tag; | |
279 else | |
280 ann3->symbol_mem_tag = ann2->symbol_mem_tag; | |
281 | |
282 if (debug) | |
283 { | |
284 fprintf (debug, " --> P%d ", p3); | |
285 print_generic_expr (debug, SSA_NAME_VAR (partition_to_var (map, p3)), | |
286 TDF_SLIM); | |
287 fprintf (debug, "\n"); | |
288 } | |
289 return true; | |
290 } | |
291 | |
292 | |
293 /* This function will make a pass through the IL, and attempt to coalesce any | |
294 SSA versions which occur in PHI's or copies. Coalescing is accomplished by | |
295 changing the underlying root variable of all coalesced version. This will | |
296 then cause the SSA->normal pass to attempt to coalesce them all to the same | |
297 variable. */ | |
298 | |
299 static unsigned int | |
300 rename_ssa_copies (void) | |
301 { | |
302 var_map map; | |
303 basic_block bb; | |
304 gimple_stmt_iterator gsi; | |
305 tree var, part_var; | |
306 gimple stmt, phi; | |
307 unsigned x; | |
308 FILE *debug; | |
309 bool updated = false; | |
310 | |
311 if (dump_file && (dump_flags & TDF_DETAILS)) | |
312 debug = dump_file; | |
313 else | |
314 debug = NULL; | |
315 | |
316 map = init_var_map (num_ssa_names + 1); | |
317 | |
318 FOR_EACH_BB (bb) | |
319 { | |
320 /* Scan for real copies. */ | |
321 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) | |
322 { | |
323 stmt = gsi_stmt (gsi); | |
324 if (gimple_assign_ssa_name_copy_p (stmt)) | |
325 { | |
326 tree lhs = gimple_assign_lhs (stmt); | |
327 tree rhs = gimple_assign_rhs1 (stmt); | |
328 | |
329 updated |= copy_rename_partition_coalesce (map, lhs, rhs, debug); | |
330 } | |
331 } | |
332 } | |
333 | |
334 FOR_EACH_BB (bb) | |
335 { | |
336 /* Treat PHI nodes as copies between the result and each argument. */ | |
337 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) | |
338 { | |
339 size_t i; | |
340 tree res; | |
341 | |
342 phi = gsi_stmt (gsi); | |
343 res = gimple_phi_result (phi); | |
344 | |
345 /* Do not process virtual SSA_NAMES. */ | |
346 if (!is_gimple_reg (SSA_NAME_VAR (res))) | |
347 continue; | |
348 | |
349 for (i = 0; i < gimple_phi_num_args (phi); i++) | |
350 { | |
351 tree arg = gimple_phi_arg (phi, i)->def; | |
352 if (TREE_CODE (arg) == SSA_NAME) | |
353 updated |= copy_rename_partition_coalesce (map, res, arg, debug); | |
354 } | |
355 } | |
356 } | |
357 | |
358 if (debug) | |
359 dump_var_map (debug, map); | |
360 | |
361 /* Now one more pass to make all elements of a partition share the same | |
362 root variable. */ | |
363 | |
364 for (x = 1; x <= num_ssa_names; x++) | |
365 { | |
366 part_var = partition_to_var (map, x); | |
367 if (!part_var) | |
368 continue; | |
369 var = map->partition_to_var[x]; | |
370 if (debug) | |
371 { | |
372 if (SSA_NAME_VAR (var) != SSA_NAME_VAR (part_var)) | |
373 { | |
374 fprintf (debug, "Coalesced "); | |
375 print_generic_expr (debug, var, TDF_SLIM); | |
376 fprintf (debug, " to "); | |
377 print_generic_expr (debug, part_var, TDF_SLIM); | |
378 fprintf (debug, "\n"); | |
379 } | |
380 } | |
381 replace_ssa_name_symbol (var, SSA_NAME_VAR (part_var)); | |
382 } | |
383 | |
384 delete_var_map (map); | |
385 return updated ? TODO_remove_unused_locals : 0; | |
386 } | |
387 | |
388 /* Return true if copy rename is to be performed. */ | |
389 | |
390 static bool | |
391 gate_copyrename (void) | |
392 { | |
393 return flag_tree_copyrename != 0; | |
394 } | |
395 | |
396 struct gimple_opt_pass pass_rename_ssa_copies = | |
397 { | |
398 { | |
399 GIMPLE_PASS, | |
400 "copyrename", /* name */ | |
401 gate_copyrename, /* gate */ | |
402 rename_ssa_copies, /* execute */ | |
403 NULL, /* sub */ | |
404 NULL, /* next */ | |
405 0, /* static_pass_number */ | |
406 TV_TREE_COPY_RENAME, /* tv_id */ | |
407 PROP_cfg | PROP_ssa, /* properties_required */ | |
408 0, /* properties_provided */ | |
409 0, /* properties_destroyed */ | |
410 0, /* todo_flags_start */ | |
411 TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */ | |
412 } | |
413 }; |