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6de9cd9a | 1 | /* Rename SSA copies. |
e8b0eabc | 2 | Copyright (C) 2004, 2006, 2007, 2008 Free Software Foundation, Inc. |
6de9cd9a DN |
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 | |
9dcd6f09 | 9 | the Free Software Foundation; either version 3, or (at your option) |
6de9cd9a DN |
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 | |
9dcd6f09 NC |
18 | along with GCC; see the file COPYING3. If not see |
19 | <http://www.gnu.org/licenses/>. */ | |
6de9cd9a DN |
20 | |
21 | #include "config.h" | |
22 | #include "system.h" | |
23 | #include "coretypes.h" | |
24 | #include "tm.h" | |
25 | #include "tree.h" | |
726a989a | 26 | #include "gimple.h" |
6de9cd9a DN |
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" | |
726a989a | 33 | #include "gimple.h" |
6de9cd9a DN |
34 | #include "tree-inline.h" |
35 | #include "timevar.h" | |
6de9cd9a DN |
36 | #include "hashtab.h" |
37 | #include "tree-dump.h" | |
38 | #include "tree-ssa-live.h" | |
39 | #include "tree-pass.h" | |
bbc630f5 | 40 | #include "langhooks.h" |
6de9cd9a | 41 | |
6de9cd9a DN |
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. | |
89dbed81 | 49 | i.e. |
6de9cd9a DN |
50 | T.3_5 = <blah> |
51 | a_1 = T.3_5 | |
52 | ||
b8698a0f L |
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 | |
6de9cd9a DN |
55 | become: |
56 | ||
57 | T.3 = <blah> | |
58 | a = T.3 | |
b8698a0f L |
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 | |
6de9cd9a DN |
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 | ||
b8698a0f | 68 | This gives the SSA->normal pass a shot at coalescing a_1 and a_5. If it is |
6de9cd9a DN |
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 | ||
b8698a0f L |
82 | get turned into |
83 | ||
6de9cd9a DN |
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: | |
b8698a0f | 102 | |
6de9cd9a DN |
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 | ||
facbf948 | 112 | static bool |
6de9cd9a DN |
113 | copy_rename_partition_coalesce (var_map map, tree var1, tree var2, FILE *debug) |
114 | { | |
115 | int p1, p2, p3; | |
116 | tree root1, root2; | |
a78e238e | 117 | tree rep1, rep2; |
a78e238e | 118 | bool ign1, ign2, abnorm; |
6de9cd9a | 119 | |
1e128c5f GB |
120 | gcc_assert (TREE_CODE (var1) == SSA_NAME); |
121 | gcc_assert (TREE_CODE (var2) == SSA_NAME); | |
6de9cd9a | 122 | |
7c6a62dd AM |
123 | register_ssa_partition (map, var1); |
124 | register_ssa_partition (map, var2); | |
6de9cd9a DN |
125 | |
126 | p1 = partition_find (map->var_partition, SSA_NAME_VERSION (var1)); | |
127 | p2 = partition_find (map->var_partition, SSA_NAME_VERSION (var2)); | |
128 | ||
129 | if (debug) | |
130 | { | |
131 | fprintf (debug, "Try : "); | |
132 | print_generic_expr (debug, var1, TDF_SLIM); | |
133 | fprintf (debug, "(P%d) & ", p1); | |
134 | print_generic_expr (debug, var2, TDF_SLIM); | |
135 | fprintf (debug, "(P%d)", p2); | |
136 | } | |
137 | ||
1e128c5f GB |
138 | gcc_assert (p1 != NO_PARTITION); |
139 | gcc_assert (p2 != NO_PARTITION); | |
6de9cd9a | 140 | |
a78e238e AM |
141 | rep1 = partition_to_var (map, p1); |
142 | rep2 = partition_to_var (map, p2); | |
143 | root1 = SSA_NAME_VAR (rep1); | |
144 | root2 = SSA_NAME_VAR (rep2); | |
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 | ||
49f48e9f AM |
153 | /* Don't coalesce if one of the variables occurs in an abnormal PHI. */ |
154 | abnorm = (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rep1) | |
155 | || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rep2)); | |
156 | if (abnorm) | |
157 | { | |
158 | if (debug) | |
159 | fprintf (debug, " : Abnormal PHI barrier. No coalesce.\n"); | |
facbf948 | 160 | return false; |
49f48e9f AM |
161 | } |
162 | ||
6de9cd9a DN |
163 | /* Partitions already have the same root, simply merge them. */ |
164 | if (root1 == root2) | |
165 | { | |
166 | p1 = partition_union (map->var_partition, p1, p2); | |
167 | if (debug) | |
168 | fprintf (debug, " : Same root, coalesced --> P%d.\n", p1); | |
facbf948 | 169 | return false; |
6de9cd9a DN |
170 | } |
171 | ||
172 | /* Never attempt to coalesce 2 difference parameters. */ | |
173 | if (TREE_CODE (root1) == PARM_DECL && TREE_CODE (root2) == PARM_DECL) | |
174 | { | |
175 | if (debug) | |
176 | fprintf (debug, " : 2 different PARM_DECLS. No coalesce.\n"); | |
facbf948 | 177 | return false; |
6de9cd9a DN |
178 | } |
179 | ||
f5a76aea RH |
180 | if ((TREE_CODE (root1) == RESULT_DECL) != (TREE_CODE (root2) == RESULT_DECL)) |
181 | { | |
182 | if (debug) | |
183 | fprintf (debug, " : One root a RESULT_DECL. No coalesce.\n"); | |
facbf948 | 184 | return false; |
f5a76aea RH |
185 | } |
186 | ||
17ad5b5e RH |
187 | ign1 = TREE_CODE (root1) == VAR_DECL && DECL_IGNORED_P (root1); |
188 | ign2 = TREE_CODE (root2) == VAR_DECL && DECL_IGNORED_P (root2); | |
6de9cd9a | 189 | |
b8698a0f | 190 | /* Never attempt to coalesce 2 user variables unless one is an inline |
694dd537 | 191 | variable. */ |
17ad5b5e | 192 | if (!ign1 && !ign2) |
6de9cd9a | 193 | { |
694dd537 AO |
194 | if (DECL_FROM_INLINE (root2)) |
195 | ign2 = true; | |
196 | else if (DECL_FROM_INLINE (root1)) | |
197 | ign1 = true; | |
b8698a0f | 198 | else |
694dd537 AO |
199 | { |
200 | if (debug) | |
201 | fprintf (debug, " : 2 different USER vars. No coalesce.\n"); | |
202 | return false; | |
203 | } | |
6de9cd9a DN |
204 | } |
205 | ||
b8698a0f | 206 | /* If both values have default defs, we can't coalesce. If only one has a |
6de9cd9a | 207 | tag, make sure that variable is the new root partition. */ |
5cd4ec7f | 208 | if (gimple_default_def (cfun, root1)) |
6de9cd9a | 209 | { |
5cd4ec7f | 210 | if (gimple_default_def (cfun, root2)) |
6de9cd9a DN |
211 | { |
212 | if (debug) | |
213 | fprintf (debug, " : 2 default defs. No coalesce.\n"); | |
facbf948 | 214 | return false; |
6de9cd9a DN |
215 | } |
216 | else | |
217 | { | |
17ad5b5e RH |
218 | ign2 = true; |
219 | ign1 = false; | |
6de9cd9a DN |
220 | } |
221 | } | |
5cd4ec7f | 222 | else if (gimple_default_def (cfun, root2)) |
17ad5b5e RH |
223 | { |
224 | ign1 = true; | |
225 | ign2 = false; | |
226 | } | |
6de9cd9a | 227 | |
bbc630f5 | 228 | /* Don't coalesce if the two variables aren't type compatible. */ |
f4088621 | 229 | if (!types_compatible_p (TREE_TYPE (root1), TREE_TYPE (root2))) |
bbc630f5 DN |
230 | { |
231 | if (debug) | |
232 | fprintf (debug, " : Incompatible types. No coalesce.\n"); | |
facbf948 | 233 | return false; |
bbc630f5 DN |
234 | } |
235 | ||
6de9cd9a DN |
236 | /* Merge the two partitions. */ |
237 | p3 = partition_union (map->var_partition, p1, p2); | |
238 | ||
b8698a0f | 239 | /* Set the root variable of the partition to the better choice, if there is |
6de9cd9a | 240 | one. */ |
17ad5b5e | 241 | if (!ign2) |
bbc630f5 | 242 | replace_ssa_name_symbol (partition_to_var (map, p3), root2); |
17ad5b5e RH |
243 | else if (!ign1) |
244 | replace_ssa_name_symbol (partition_to_var (map, p3), root1); | |
6de9cd9a | 245 | |
6de9cd9a DN |
246 | if (debug) |
247 | { | |
248 | fprintf (debug, " --> P%d ", p3); | |
b8698a0f | 249 | print_generic_expr (debug, SSA_NAME_VAR (partition_to_var (map, p3)), |
6de9cd9a DN |
250 | TDF_SLIM); |
251 | fprintf (debug, "\n"); | |
252 | } | |
facbf948 | 253 | return true; |
6de9cd9a DN |
254 | } |
255 | ||
256 | ||
257 | /* This function will make a pass through the IL, and attempt to coalesce any | |
258 | SSA versions which occur in PHI's or copies. Coalescing is accomplished by | |
b8698a0f L |
259 | changing the underlying root variable of all coalesced version. This will |
260 | then cause the SSA->normal pass to attempt to coalesce them all to the same | |
6de9cd9a DN |
261 | variable. */ |
262 | ||
c2924966 | 263 | static unsigned int |
6de9cd9a DN |
264 | rename_ssa_copies (void) |
265 | { | |
266 | var_map map; | |
267 | basic_block bb; | |
726a989a RB |
268 | gimple_stmt_iterator gsi; |
269 | tree var, part_var; | |
270 | gimple stmt, phi; | |
6de9cd9a DN |
271 | unsigned x; |
272 | FILE *debug; | |
facbf948 | 273 | bool updated = false; |
6de9cd9a DN |
274 | |
275 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
276 | debug = dump_file; | |
277 | else | |
278 | debug = NULL; | |
279 | ||
17c665a9 | 280 | map = init_var_map (num_ssa_names); |
6de9cd9a DN |
281 | |
282 | FOR_EACH_BB (bb) | |
283 | { | |
284 | /* Scan for real copies. */ | |
726a989a | 285 | for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
6de9cd9a | 286 | { |
726a989a RB |
287 | stmt = gsi_stmt (gsi); |
288 | if (gimple_assign_ssa_name_copy_p (stmt)) | |
6de9cd9a | 289 | { |
726a989a RB |
290 | tree lhs = gimple_assign_lhs (stmt); |
291 | tree rhs = gimple_assign_rhs1 (stmt); | |
6de9cd9a | 292 | |
726a989a | 293 | updated |= copy_rename_partition_coalesce (map, lhs, rhs, debug); |
6de9cd9a DN |
294 | } |
295 | } | |
296 | } | |
297 | ||
298 | FOR_EACH_BB (bb) | |
299 | { | |
300 | /* Treat PHI nodes as copies between the result and each argument. */ | |
726a989a | 301 | for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
6de9cd9a | 302 | { |
726a989a RB |
303 | size_t i; |
304 | tree res; | |
305 | ||
306 | phi = gsi_stmt (gsi); | |
307 | res = gimple_phi_result (phi); | |
6de9cd9a | 308 | |
26e79d10 RH |
309 | /* Do not process virtual SSA_NAMES. */ |
310 | if (!is_gimple_reg (SSA_NAME_VAR (res))) | |
6de9cd9a DN |
311 | continue; |
312 | ||
726a989a | 313 | for (i = 0; i < gimple_phi_num_args (phi); i++) |
6de9cd9a | 314 | { |
726a989a | 315 | tree arg = gimple_phi_arg (phi, i)->def; |
6de9cd9a | 316 | if (TREE_CODE (arg) == SSA_NAME) |
facbf948 | 317 | updated |= copy_rename_partition_coalesce (map, res, arg, debug); |
6de9cd9a DN |
318 | } |
319 | } | |
320 | } | |
321 | ||
322 | if (debug) | |
323 | dump_var_map (debug, map); | |
324 | ||
325 | /* Now one more pass to make all elements of a partition share the same | |
326 | root variable. */ | |
b8698a0f | 327 | |
17c665a9 | 328 | for (x = 1; x < num_ssa_names; x++) |
6de9cd9a DN |
329 | { |
330 | part_var = partition_to_var (map, x); | |
331 | if (!part_var) | |
332 | continue; | |
4e3825db | 333 | var = ssa_name (x); |
6de9cd9a DN |
334 | if (debug) |
335 | { | |
336 | if (SSA_NAME_VAR (var) != SSA_NAME_VAR (part_var)) | |
337 | { | |
338 | fprintf (debug, "Coalesced "); | |
339 | print_generic_expr (debug, var, TDF_SLIM); | |
340 | fprintf (debug, " to "); | |
341 | print_generic_expr (debug, part_var, TDF_SLIM); | |
342 | fprintf (debug, "\n"); | |
343 | } | |
344 | } | |
bbc630f5 | 345 | replace_ssa_name_symbol (var, SSA_NAME_VAR (part_var)); |
6de9cd9a DN |
346 | } |
347 | ||
348 | delete_var_map (map); | |
facbf948 | 349 | return updated ? TODO_remove_unused_locals : 0; |
6de9cd9a DN |
350 | } |
351 | ||
352 | /* Return true if copy rename is to be performed. */ | |
353 | ||
354 | static bool | |
355 | gate_copyrename (void) | |
356 | { | |
357 | return flag_tree_copyrename != 0; | |
358 | } | |
359 | ||
b8698a0f | 360 | struct gimple_opt_pass pass_rename_ssa_copies = |
8ddbbcae JH |
361 | { |
362 | { | |
363 | GIMPLE_PASS, | |
6de9cd9a DN |
364 | "copyrename", /* name */ |
365 | gate_copyrename, /* gate */ | |
366 | rename_ssa_copies, /* execute */ | |
367 | NULL, /* sub */ | |
368 | NULL, /* next */ | |
369 | 0, /* static_pass_number */ | |
370 | TV_TREE_COPY_RENAME, /* tv_id */ | |
7faade0f | 371 | PROP_cfg | PROP_ssa, /* properties_required */ |
6de9cd9a DN |
372 | 0, /* properties_provided */ |
373 | 0, /* properties_destroyed */ | |
b8698a0f | 374 | 0, /* todo_flags_start */ |
8ddbbcae JH |
375 | TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */ |
376 | } | |
b8698a0f | 377 | }; |