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6de9cd9a | 1 | /* Rename SSA copies. |
9ffa621e | 2 | Copyright (C) 2004, 2006, 2007, 2008, 2009, 2010, 2011 |
cf835838 | 3 | Free Software Foundation, Inc. |
6de9cd9a DN |
4 | Contributed by Andrew MacLeod <amacleod@redhat.com> |
5 | ||
6 | This file is part of GCC. | |
7 | ||
8 | GCC is free software; you can redistribute it and/or modify | |
9 | it under the terms of the GNU General Public License as published by | |
9dcd6f09 | 10 | the Free Software Foundation; either version 3, or (at your option) |
6de9cd9a DN |
11 | any later version. |
12 | ||
13 | GCC is distributed in the hope that it will be useful, | |
14 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | GNU General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
9dcd6f09 NC |
19 | along with GCC; see the file COPYING3. If not see |
20 | <http://www.gnu.org/licenses/>. */ | |
6de9cd9a DN |
21 | |
22 | #include "config.h" | |
23 | #include "system.h" | |
24 | #include "coretypes.h" | |
25 | #include "tm.h" | |
26 | #include "tree.h" | |
726a989a | 27 | #include "gimple.h" |
6de9cd9a DN |
28 | #include "flags.h" |
29 | #include "basic-block.h" | |
30 | #include "function.h" | |
cf835838 | 31 | #include "tree-pretty-print.h" |
6de9cd9a DN |
32 | #include "bitmap.h" |
33 | #include "tree-flow.h" | |
726a989a | 34 | #include "gimple.h" |
6de9cd9a | 35 | #include "tree-inline.h" |
6de9cd9a | 36 | #include "hashtab.h" |
6de9cd9a DN |
37 | #include "tree-ssa-live.h" |
38 | #include "tree-pass.h" | |
bbc630f5 | 39 | #include "langhooks.h" |
6de9cd9a | 40 | |
4da3b811 NF |
41 | static struct |
42 | { | |
43 | /* Number of copies coalesced. */ | |
44 | int coalesced; | |
45 | } stats; | |
46 | ||
6de9cd9a DN |
47 | /* The following routines implement the SSA copy renaming phase. |
48 | ||
49 | This optimization looks for copies between 2 SSA_NAMES, either through a | |
50 | direct copy, or an implicit one via a PHI node result and its arguments. | |
51 | ||
52 | Each copy is examined to determine if it is possible to rename the base | |
53 | variable of one of the operands to the same variable as the other operand. | |
89dbed81 | 54 | i.e. |
6de9cd9a DN |
55 | T.3_5 = <blah> |
56 | a_1 = T.3_5 | |
57 | ||
b8698a0f L |
58 | If this copy couldn't be copy propagated, it could possibly remain in the |
59 | program throughout the optimization phases. After SSA->normal, it would | |
6de9cd9a DN |
60 | become: |
61 | ||
62 | T.3 = <blah> | |
63 | a = T.3 | |
b8698a0f L |
64 | |
65 | Since T.3_5 is distinct from all other SSA versions of T.3, there is no | |
66 | fundamental reason why the base variable needs to be T.3, subject to | |
67 | certain restrictions. This optimization attempts to determine if we can | |
6de9cd9a DN |
68 | change the base variable on copies like this, and result in code such as: |
69 | ||
70 | a_5 = <blah> | |
71 | a_1 = a_5 | |
72 | ||
b8698a0f | 73 | This gives the SSA->normal pass a shot at coalescing a_1 and a_5. If it is |
6de9cd9a DN |
74 | possible, the copy goes away completely. If it isn't possible, a new temp |
75 | will be created for a_5, and you will end up with the exact same code: | |
76 | ||
77 | a.8 = <blah> | |
78 | a = a.8 | |
79 | ||
80 | The other benefit of performing this optimization relates to what variables | |
81 | are chosen in copies. Gimplification of the program uses temporaries for | |
82 | a lot of things. expressions like | |
83 | ||
84 | a_1 = <blah> | |
85 | <blah2> = a_1 | |
86 | ||
b8698a0f L |
87 | get turned into |
88 | ||
6de9cd9a DN |
89 | T.3_5 = <blah> |
90 | a_1 = T.3_5 | |
91 | <blah2> = a_1 | |
92 | ||
93 | Copy propagation is done in a forward direction, and if we can propagate | |
94 | through the copy, we end up with: | |
95 | ||
96 | T.3_5 = <blah> | |
97 | <blah2> = T.3_5 | |
98 | ||
99 | The copy is gone, but so is all reference to the user variable 'a'. By | |
100 | performing this optimization, we would see the sequence: | |
101 | ||
102 | a_5 = <blah> | |
103 | a_1 = a_5 | |
104 | <blah2> = a_1 | |
105 | ||
106 | which copy propagation would then turn into: | |
b8698a0f | 107 | |
6de9cd9a DN |
108 | a_5 = <blah> |
109 | <blah2> = a_5 | |
110 | ||
111 | and so we still retain the user variable whenever possible. */ | |
112 | ||
113 | ||
114 | /* Coalesce the partitions in MAP representing VAR1 and VAR2 if it is valid. | |
115 | Choose a representative for the partition, and send debug info to DEBUG. */ | |
116 | ||
facbf948 | 117 | static bool |
6de9cd9a DN |
118 | copy_rename_partition_coalesce (var_map map, tree var1, tree var2, FILE *debug) |
119 | { | |
120 | int p1, p2, p3; | |
121 | tree root1, root2; | |
a78e238e | 122 | tree rep1, rep2; |
a78e238e | 123 | bool ign1, ign2, abnorm; |
6de9cd9a | 124 | |
1e128c5f GB |
125 | gcc_assert (TREE_CODE (var1) == SSA_NAME); |
126 | gcc_assert (TREE_CODE (var2) == SSA_NAME); | |
6de9cd9a | 127 | |
7c6a62dd AM |
128 | register_ssa_partition (map, var1); |
129 | register_ssa_partition (map, var2); | |
6de9cd9a DN |
130 | |
131 | p1 = partition_find (map->var_partition, SSA_NAME_VERSION (var1)); | |
132 | p2 = partition_find (map->var_partition, SSA_NAME_VERSION (var2)); | |
133 | ||
134 | if (debug) | |
135 | { | |
136 | fprintf (debug, "Try : "); | |
137 | print_generic_expr (debug, var1, TDF_SLIM); | |
138 | fprintf (debug, "(P%d) & ", p1); | |
139 | print_generic_expr (debug, var2, TDF_SLIM); | |
140 | fprintf (debug, "(P%d)", p2); | |
141 | } | |
142 | ||
1e128c5f GB |
143 | gcc_assert (p1 != NO_PARTITION); |
144 | gcc_assert (p2 != NO_PARTITION); | |
6de9cd9a | 145 | |
6de9cd9a DN |
146 | if (p1 == p2) |
147 | { | |
148 | if (debug) | |
149 | fprintf (debug, " : Already coalesced.\n"); | |
facbf948 | 150 | return false; |
6de9cd9a DN |
151 | } |
152 | ||
70b5e7dc RG |
153 | rep1 = partition_to_var (map, p1); |
154 | rep2 = partition_to_var (map, p2); | |
155 | root1 = SSA_NAME_VAR (rep1); | |
156 | root2 = SSA_NAME_VAR (rep2); | |
157 | if (!root1 && !root2) | |
158 | return false; | |
159 | ||
49f48e9f AM |
160 | /* Don't coalesce if one of the variables occurs in an abnormal PHI. */ |
161 | abnorm = (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rep1) | |
162 | || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rep2)); | |
163 | if (abnorm) | |
164 | { | |
165 | if (debug) | |
166 | fprintf (debug, " : Abnormal PHI barrier. No coalesce.\n"); | |
facbf948 | 167 | return false; |
49f48e9f AM |
168 | } |
169 | ||
6de9cd9a DN |
170 | /* Partitions already have the same root, simply merge them. */ |
171 | if (root1 == root2) | |
172 | { | |
173 | p1 = partition_union (map->var_partition, p1, p2); | |
174 | if (debug) | |
175 | fprintf (debug, " : Same root, coalesced --> P%d.\n", p1); | |
facbf948 | 176 | return false; |
6de9cd9a DN |
177 | } |
178 | ||
9ffa621e | 179 | /* Never attempt to coalesce 2 different parameters. */ |
70b5e7dc RG |
180 | if ((root1 && TREE_CODE (root1) == PARM_DECL) |
181 | && (root2 && TREE_CODE (root2) == PARM_DECL)) | |
6de9cd9a DN |
182 | { |
183 | if (debug) | |
184 | fprintf (debug, " : 2 different PARM_DECLS. No coalesce.\n"); | |
facbf948 | 185 | return false; |
6de9cd9a DN |
186 | } |
187 | ||
70b5e7dc RG |
188 | if ((root1 && TREE_CODE (root1) == RESULT_DECL) |
189 | != (root2 && TREE_CODE (root2) == RESULT_DECL)) | |
f5a76aea RH |
190 | { |
191 | if (debug) | |
192 | fprintf (debug, " : One root a RESULT_DECL. No coalesce.\n"); | |
facbf948 | 193 | return false; |
f5a76aea RH |
194 | } |
195 | ||
70b5e7dc RG |
196 | ign1 = !root1 || (TREE_CODE (root1) == VAR_DECL && DECL_IGNORED_P (root1)); |
197 | ign2 = !root2 || (TREE_CODE (root2) == VAR_DECL && DECL_IGNORED_P (root2)); | |
6de9cd9a | 198 | |
21d01365 | 199 | /* Refrain from coalescing user variables, if requested. */ |
17ad5b5e | 200 | if (!ign1 && !ign2) |
6de9cd9a | 201 | { |
21d01365 AO |
202 | if (flag_ssa_coalesce_vars && DECL_FROM_INLINE (root2)) |
203 | ign2 = true; | |
204 | else if (flag_ssa_coalesce_vars && DECL_FROM_INLINE (root1)) | |
694dd537 | 205 | ign1 = true; |
21d01365 | 206 | else if (flag_ssa_coalesce_vars != 2) |
694dd537 AO |
207 | { |
208 | if (debug) | |
209 | fprintf (debug, " : 2 different USER vars. No coalesce.\n"); | |
210 | return false; | |
211 | } | |
21d01365 AO |
212 | else |
213 | ign2 = true; | |
6de9cd9a DN |
214 | } |
215 | ||
b8698a0f | 216 | /* If both values have default defs, we can't coalesce. If only one has a |
6de9cd9a | 217 | tag, make sure that variable is the new root partition. */ |
70b5e7dc | 218 | if (root1 && ssa_default_def (cfun, root1)) |
6de9cd9a | 219 | { |
70b5e7dc | 220 | if (root2 && ssa_default_def (cfun, root2)) |
6de9cd9a DN |
221 | { |
222 | if (debug) | |
223 | fprintf (debug, " : 2 default defs. No coalesce.\n"); | |
facbf948 | 224 | return false; |
6de9cd9a DN |
225 | } |
226 | else | |
227 | { | |
17ad5b5e RH |
228 | ign2 = true; |
229 | ign1 = false; | |
6de9cd9a DN |
230 | } |
231 | } | |
70b5e7dc | 232 | else if (root2 && ssa_default_def (cfun, root2)) |
17ad5b5e RH |
233 | { |
234 | ign1 = true; | |
235 | ign2 = false; | |
236 | } | |
6de9cd9a | 237 | |
70b5e7dc RG |
238 | /* Do not coalesce if we cannot assign a symbol to the partition. */ |
239 | if (!(!ign2 && root2) | |
240 | && !(!ign1 && root1)) | |
241 | { | |
242 | if (debug) | |
243 | fprintf (debug, " : Choosen variable has no root. No coalesce.\n"); | |
244 | return false; | |
245 | } | |
246 | ||
9ffa621e JJ |
247 | /* Don't coalesce if the new chosen root variable would be read-only. |
248 | If both ign1 && ign2, then the root var of the larger partition | |
249 | wins, so reject in that case if any of the root vars is TREE_READONLY. | |
250 | Otherwise reject only if the root var, on which replace_ssa_name_symbol | |
251 | will be called below, is readonly. */ | |
70b5e7dc RG |
252 | if (((root1 && TREE_READONLY (root1)) && ign2) |
253 | || ((root2 && TREE_READONLY (root2)) && ign1)) | |
9ffa621e JJ |
254 | { |
255 | if (debug) | |
256 | fprintf (debug, " : Readonly variable. No coalesce.\n"); | |
257 | return false; | |
258 | } | |
259 | ||
ddd268f2 | 260 | /* Don't coalesce if the two variables aren't type compatible . */ |
70b5e7dc | 261 | if (!types_compatible_p (TREE_TYPE (var1), TREE_TYPE (var2)) |
ddd268f2 RG |
262 | /* There is a disconnect between the middle-end type-system and |
263 | VRP, avoid coalescing enum types with different bounds. */ | |
70b5e7dc RG |
264 | || ((TREE_CODE (TREE_TYPE (var1)) == ENUMERAL_TYPE |
265 | || TREE_CODE (TREE_TYPE (var2)) == ENUMERAL_TYPE) | |
266 | && TREE_TYPE (var1) != TREE_TYPE (var2))) | |
bbc630f5 DN |
267 | { |
268 | if (debug) | |
ddd268f2 | 269 | fprintf (debug, " : Incompatible types. No coalesce.\n"); |
facbf948 | 270 | return false; |
bbc630f5 DN |
271 | } |
272 | ||
6de9cd9a DN |
273 | /* Merge the two partitions. */ |
274 | p3 = partition_union (map->var_partition, p1, p2); | |
275 | ||
b8698a0f | 276 | /* Set the root variable of the partition to the better choice, if there is |
6de9cd9a | 277 | one. */ |
70b5e7dc | 278 | if (!ign2 && root2) |
bbc630f5 | 279 | replace_ssa_name_symbol (partition_to_var (map, p3), root2); |
70b5e7dc | 280 | else if (!ign1 && root1) |
17ad5b5e | 281 | replace_ssa_name_symbol (partition_to_var (map, p3), root1); |
70b5e7dc RG |
282 | else |
283 | gcc_unreachable (); | |
6de9cd9a | 284 | |
6de9cd9a DN |
285 | if (debug) |
286 | { | |
287 | fprintf (debug, " --> P%d ", p3); | |
b8698a0f | 288 | print_generic_expr (debug, SSA_NAME_VAR (partition_to_var (map, p3)), |
6de9cd9a DN |
289 | TDF_SLIM); |
290 | fprintf (debug, "\n"); | |
291 | } | |
facbf948 | 292 | return true; |
6de9cd9a DN |
293 | } |
294 | ||
295 | ||
296 | /* This function will make a pass through the IL, and attempt to coalesce any | |
297 | SSA versions which occur in PHI's or copies. Coalescing is accomplished by | |
b8698a0f L |
298 | changing the underlying root variable of all coalesced version. This will |
299 | then cause the SSA->normal pass to attempt to coalesce them all to the same | |
6de9cd9a DN |
300 | variable. */ |
301 | ||
c2924966 | 302 | static unsigned int |
6de9cd9a DN |
303 | rename_ssa_copies (void) |
304 | { | |
305 | var_map map; | |
306 | basic_block bb; | |
726a989a RB |
307 | gimple_stmt_iterator gsi; |
308 | tree var, part_var; | |
309 | gimple stmt, phi; | |
6de9cd9a DN |
310 | unsigned x; |
311 | FILE *debug; | |
facbf948 | 312 | bool updated = false; |
6de9cd9a | 313 | |
b7a83ad8 RG |
314 | memset (&stats, 0, sizeof (stats)); |
315 | ||
6de9cd9a DN |
316 | if (dump_file && (dump_flags & TDF_DETAILS)) |
317 | debug = dump_file; | |
318 | else | |
319 | debug = NULL; | |
320 | ||
17c665a9 | 321 | map = init_var_map (num_ssa_names); |
6de9cd9a DN |
322 | |
323 | FOR_EACH_BB (bb) | |
324 | { | |
325 | /* Scan for real copies. */ | |
726a989a | 326 | for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
6de9cd9a | 327 | { |
726a989a RB |
328 | stmt = gsi_stmt (gsi); |
329 | if (gimple_assign_ssa_name_copy_p (stmt)) | |
6de9cd9a | 330 | { |
726a989a RB |
331 | tree lhs = gimple_assign_lhs (stmt); |
332 | tree rhs = gimple_assign_rhs1 (stmt); | |
6de9cd9a | 333 | |
726a989a | 334 | updated |= copy_rename_partition_coalesce (map, lhs, rhs, debug); |
6de9cd9a DN |
335 | } |
336 | } | |
337 | } | |
338 | ||
339 | FOR_EACH_BB (bb) | |
340 | { | |
341 | /* Treat PHI nodes as copies between the result and each argument. */ | |
726a989a | 342 | for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
6de9cd9a | 343 | { |
726a989a RB |
344 | size_t i; |
345 | tree res; | |
346 | ||
347 | phi = gsi_stmt (gsi); | |
348 | res = gimple_phi_result (phi); | |
6de9cd9a | 349 | |
26e79d10 | 350 | /* Do not process virtual SSA_NAMES. */ |
61f7b9ae | 351 | if (virtual_operand_p (res)) |
6de9cd9a DN |
352 | continue; |
353 | ||
61f7b9ae RG |
354 | /* Make sure to only use the same partition for an argument |
355 | as the result but never the other way around. */ | |
356 | if (SSA_NAME_VAR (res) | |
357 | && !DECL_IGNORED_P (SSA_NAME_VAR (res))) | |
358 | for (i = 0; i < gimple_phi_num_args (phi); i++) | |
359 | { | |
360 | tree arg = PHI_ARG_DEF (phi, i); | |
361 | if (TREE_CODE (arg) == SSA_NAME) | |
362 | updated |= copy_rename_partition_coalesce (map, res, arg, | |
363 | debug); | |
364 | } | |
365 | /* Else if all arguments are in the same partition try to merge | |
366 | it with the result. */ | |
367 | else | |
368 | { | |
369 | int all_p_same = -1; | |
370 | int p = -1; | |
371 | for (i = 0; i < gimple_phi_num_args (phi); i++) | |
372 | { | |
373 | tree arg = PHI_ARG_DEF (phi, i); | |
374 | if (TREE_CODE (arg) != SSA_NAME) | |
375 | { | |
376 | all_p_same = 0; | |
377 | break; | |
378 | } | |
379 | else if (all_p_same == -1) | |
380 | { | |
381 | p = partition_find (map->var_partition, | |
382 | SSA_NAME_VERSION (arg)); | |
383 | all_p_same = 1; | |
384 | } | |
385 | else if (all_p_same == 1 | |
386 | && p != partition_find (map->var_partition, | |
387 | SSA_NAME_VERSION (arg))) | |
388 | { | |
389 | all_p_same = 0; | |
390 | break; | |
391 | } | |
392 | } | |
393 | if (all_p_same == 1) | |
394 | updated |= copy_rename_partition_coalesce (map, res, | |
395 | PHI_ARG_DEF (phi, 0), | |
396 | debug); | |
397 | } | |
6de9cd9a DN |
398 | } |
399 | } | |
400 | ||
401 | if (debug) | |
402 | dump_var_map (debug, map); | |
403 | ||
404 | /* Now one more pass to make all elements of a partition share the same | |
405 | root variable. */ | |
b8698a0f | 406 | |
17c665a9 | 407 | for (x = 1; x < num_ssa_names; x++) |
6de9cd9a DN |
408 | { |
409 | part_var = partition_to_var (map, x); | |
410 | if (!part_var) | |
411 | continue; | |
4e3825db | 412 | var = ssa_name (x); |
b7a83ad8 RG |
413 | if (SSA_NAME_VAR (var) == SSA_NAME_VAR (part_var)) |
414 | continue; | |
6de9cd9a DN |
415 | if (debug) |
416 | { | |
b7a83ad8 RG |
417 | fprintf (debug, "Coalesced "); |
418 | print_generic_expr (debug, var, TDF_SLIM); | |
419 | fprintf (debug, " to "); | |
420 | print_generic_expr (debug, part_var, TDF_SLIM); | |
421 | fprintf (debug, "\n"); | |
6de9cd9a | 422 | } |
4da3b811 | 423 | stats.coalesced++; |
bbc630f5 | 424 | replace_ssa_name_symbol (var, SSA_NAME_VAR (part_var)); |
6de9cd9a DN |
425 | } |
426 | ||
4da3b811 NF |
427 | statistics_counter_event (cfun, "copies coalesced", |
428 | stats.coalesced); | |
6de9cd9a | 429 | delete_var_map (map); |
facbf948 | 430 | return updated ? TODO_remove_unused_locals : 0; |
6de9cd9a DN |
431 | } |
432 | ||
433 | /* Return true if copy rename is to be performed. */ | |
434 | ||
435 | static bool | |
436 | gate_copyrename (void) | |
437 | { | |
438 | return flag_tree_copyrename != 0; | |
439 | } | |
440 | ||
b8698a0f | 441 | struct gimple_opt_pass pass_rename_ssa_copies = |
8ddbbcae JH |
442 | { |
443 | { | |
444 | GIMPLE_PASS, | |
6de9cd9a DN |
445 | "copyrename", /* name */ |
446 | gate_copyrename, /* gate */ | |
447 | rename_ssa_copies, /* execute */ | |
448 | NULL, /* sub */ | |
449 | NULL, /* next */ | |
450 | 0, /* static_pass_number */ | |
451 | TV_TREE_COPY_RENAME, /* tv_id */ | |
7faade0f | 452 | PROP_cfg | PROP_ssa, /* properties_required */ |
6de9cd9a DN |
453 | 0, /* properties_provided */ |
454 | 0, /* properties_destroyed */ | |
b8698a0f | 455 | 0, /* todo_flags_start */ |
22c5fa5f | 456 | TODO_verify_ssa /* todo_flags_finish */ |
8ddbbcae | 457 | } |
b8698a0f | 458 | }; |