]>
Commit | Line | Data |
---|---|---|
6de9cd9a DN |
1 | /* Miscellaneous SSA utility functions. |
2 | Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc. | |
3 | ||
4 | This file is part of GCC. | |
5 | ||
6 | GCC is free software; you can redistribute it and/or modify | |
7 | it under the terms of the GNU General Public License as published by | |
8 | the Free Software Foundation; either version 2, or (at your option) | |
9 | any later version. | |
10 | ||
11 | GCC is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | GNU General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
17 | along with GCC; see the file COPYING. If not, write to | |
18 | the Free Software Foundation, 59 Temple Place - Suite 330, | |
19 | Boston, MA 02111-1307, USA. */ | |
20 | ||
21 | #include "config.h" | |
22 | #include "system.h" | |
23 | #include "coretypes.h" | |
24 | #include "tm.h" | |
25 | #include "tree.h" | |
26 | #include "flags.h" | |
27 | #include "rtl.h" | |
28 | #include "tm_p.h" | |
29 | #include "ggc.h" | |
30 | #include "langhooks.h" | |
31 | #include "hard-reg-set.h" | |
32 | #include "basic-block.h" | |
33 | #include "output.h" | |
34 | #include "errors.h" | |
35 | #include "expr.h" | |
36 | #include "function.h" | |
37 | #include "diagnostic.h" | |
38 | #include "bitmap.h" | |
39 | #include "tree-flow.h" | |
40 | #include "tree-simple.h" | |
41 | #include "tree-inline.h" | |
42 | #include "varray.h" | |
43 | #include "timevar.h" | |
44 | #include "tree-alias-common.h" | |
45 | #include "hashtab.h" | |
46 | #include "tree-dump.h" | |
47 | #include "tree-pass.h" | |
48 | ||
49 | ||
50 | /* Remove edge E and remove the corresponding arguments from the PHI nodes | |
51 | in E's destination block. */ | |
52 | ||
53 | void | |
54 | ssa_remove_edge (edge e) | |
55 | { | |
56 | tree phi, next; | |
57 | ||
58 | /* Remove the appropriate PHI arguments in E's destination block. */ | |
59 | for (phi = phi_nodes (e->dest); phi; phi = next) | |
60 | { | |
61 | next = TREE_CHAIN (phi); | |
62 | remove_phi_arg (phi, e->src); | |
63 | } | |
64 | ||
65 | remove_edge (e); | |
66 | } | |
67 | ||
68 | /* Remove remove the corresponding arguments from the PHI nodes | |
69 | in E's destination block and redirect it to DEST. Return redirected edge. | |
70 | The list of removed arguments is stored in PENDING_STMT (e). */ | |
71 | ||
72 | edge | |
73 | ssa_redirect_edge (edge e, basic_block dest) | |
74 | { | |
75 | tree phi, next; | |
76 | tree list = NULL, *last = &list; | |
77 | tree src, dst, node; | |
78 | int i; | |
79 | ||
80 | /* Remove the appropriate PHI arguments in E's destination block. */ | |
81 | for (phi = phi_nodes (e->dest); phi; phi = next) | |
82 | { | |
83 | next = TREE_CHAIN (phi); | |
84 | ||
85 | i = phi_arg_from_edge (phi, e); | |
86 | if (i < 0) | |
87 | continue; | |
88 | ||
89 | src = PHI_ARG_DEF (phi, i); | |
90 | dst = PHI_RESULT (phi); | |
91 | node = build_tree_list (dst, src); | |
92 | *last = node; | |
93 | last = &TREE_CHAIN (node); | |
94 | ||
95 | remove_phi_arg_num (phi, i); | |
96 | } | |
97 | ||
98 | e = redirect_edge_succ_nodup (e, dest); | |
99 | PENDING_STMT (e) = list; | |
100 | ||
101 | return e; | |
102 | } | |
103 | ||
104 | ||
105 | /* Return true if the definition of SSA_NAME at block BB is malformed. | |
106 | ||
107 | STMT is the statement where SSA_NAME is created. | |
108 | ||
109 | DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME version | |
110 | numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set, it means that the | |
111 | block in that array slot contains the definition of SSA_NAME. */ | |
112 | ||
113 | static bool | |
114 | verify_def (basic_block bb, basic_block *definition_block, tree ssa_name, | |
115 | tree stmt) | |
116 | { | |
117 | bool err = false; | |
118 | ||
119 | if (TREE_CODE (ssa_name) != SSA_NAME) | |
120 | { | |
121 | error ("Expected an SSA_NAME object"); | |
122 | debug_generic_stmt (ssa_name); | |
123 | debug_generic_stmt (stmt); | |
124 | } | |
125 | ||
126 | if (definition_block[SSA_NAME_VERSION (ssa_name)]) | |
127 | { | |
128 | error ("SSA_NAME created in two different blocks %i and %i", | |
129 | definition_block[SSA_NAME_VERSION (ssa_name)]->index, bb->index); | |
130 | fprintf (stderr, "SSA_NAME: "); | |
131 | debug_generic_stmt (ssa_name); | |
132 | debug_generic_stmt (stmt); | |
133 | err = true; | |
134 | } | |
135 | ||
136 | definition_block[SSA_NAME_VERSION (ssa_name)] = bb; | |
137 | ||
138 | if (SSA_NAME_DEF_STMT (ssa_name) != stmt) | |
139 | { | |
140 | error ("SSA_NAME_DEF_STMT is wrong"); | |
141 | fprintf (stderr, "SSA_NAME: "); | |
142 | debug_generic_stmt (ssa_name); | |
143 | fprintf (stderr, "Expected definition statement:\n"); | |
144 | debug_generic_stmt (SSA_NAME_DEF_STMT (ssa_name)); | |
145 | fprintf (stderr, "\nActual definition statement:\n"); | |
146 | debug_generic_stmt (stmt); | |
147 | err = true; | |
148 | } | |
149 | ||
150 | return err; | |
151 | } | |
152 | ||
153 | ||
154 | /* Return true if the use of SSA_NAME at statement STMT in block BB is | |
155 | malformed. | |
156 | ||
157 | DEF_BB is the block where SSA_NAME was found to be created. | |
158 | ||
159 | IDOM contains immediate dominator information for the flowgraph. | |
160 | ||
161 | CHECK_ABNORMAL is true if the caller wants to check whether this use | |
162 | is flowing through an abnormal edge (only used when checking PHI | |
163 | arguments). */ | |
164 | ||
165 | static bool | |
166 | verify_use (basic_block bb, basic_block def_bb, tree ssa_name, | |
167 | tree stmt, bool check_abnormal) | |
168 | { | |
169 | bool err = false; | |
170 | ||
171 | if (IS_EMPTY_STMT (SSA_NAME_DEF_STMT (ssa_name))) | |
172 | ; /* Nothing to do. */ | |
173 | else if (!def_bb) | |
174 | { | |
175 | error ("Missing definition"); | |
176 | err = true; | |
177 | } | |
178 | else if (bb != def_bb | |
179 | && !dominated_by_p (CDI_DOMINATORS, bb, def_bb)) | |
180 | { | |
181 | error ("Definition in block %i does not dominate use in block %i", | |
182 | def_bb->index, bb->index); | |
183 | err = true; | |
184 | } | |
185 | ||
186 | if (check_abnormal | |
187 | && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (ssa_name)) | |
188 | { | |
189 | error ("SSA_NAME_OCCURS_IN_ABNORMAL_PHI should be set"); | |
190 | err = true; | |
191 | } | |
192 | ||
193 | if (err) | |
194 | { | |
195 | fprintf (stderr, "for SSA_NAME: "); | |
196 | debug_generic_stmt (ssa_name); | |
197 | fprintf (stderr, "in statement:\n"); | |
198 | debug_generic_stmt (stmt); | |
199 | } | |
200 | ||
201 | return err; | |
202 | } | |
203 | ||
204 | ||
205 | /* Return true if any of the arguments for PHI node PHI at block BB is | |
206 | malformed. | |
207 | ||
208 | IDOM contains immediate dominator information for the flowgraph. | |
209 | ||
210 | DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME version | |
211 | numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set, it means that the | |
212 | block in that array slot contains the definition of SSA_NAME. */ | |
213 | ||
214 | static bool | |
215 | verify_phi_args (tree phi, basic_block bb, basic_block *definition_block) | |
216 | { | |
217 | edge e; | |
218 | bool err = false; | |
219 | int i, phi_num_args = PHI_NUM_ARGS (phi); | |
220 | ||
221 | /* Mark all the incoming edges. */ | |
222 | for (e = bb->pred; e; e = e->pred_next) | |
223 | e->aux = (void *) 1; | |
224 | ||
225 | for (i = 0; i < phi_num_args; i++) | |
226 | { | |
227 | tree op = PHI_ARG_DEF (phi, i); | |
228 | ||
229 | e = PHI_ARG_EDGE (phi, i); | |
230 | ||
231 | if (TREE_CODE (op) == SSA_NAME) | |
232 | err |= verify_use (e->src, definition_block[SSA_NAME_VERSION (op)], op, | |
233 | phi, e->flags & EDGE_ABNORMAL); | |
234 | ||
235 | if (e->dest != bb) | |
236 | { | |
237 | error ("Wrong edge %d->%d for PHI argument\n", | |
238 | e->src->index, e->dest->index, bb->index); | |
239 | err = true; | |
240 | } | |
241 | ||
242 | if (e->aux == (void *) 0) | |
243 | { | |
244 | error ("PHI argument flowing through dead edge %d->%d\n", | |
245 | e->src->index, e->dest->index); | |
246 | err = true; | |
247 | } | |
248 | ||
249 | if (e->aux == (void *) 2) | |
250 | { | |
251 | error ("PHI argument duplicated for edge %d->%d\n", e->src->index, | |
252 | e->dest->index); | |
253 | err = true; | |
254 | } | |
255 | ||
256 | if (err) | |
257 | { | |
258 | fprintf (stderr, "PHI argument\n"); | |
259 | debug_generic_stmt (op); | |
260 | } | |
261 | ||
262 | e->aux = (void *) 2; | |
263 | } | |
264 | ||
265 | for (e = bb->pred; e; e = e->pred_next) | |
266 | { | |
267 | if (e->aux != (void *) 2) | |
268 | { | |
269 | error ("No argument flowing through edge %d->%d\n", e->src->index, | |
270 | e->dest->index); | |
271 | err = true; | |
272 | } | |
273 | e->aux = (void *) 0; | |
274 | } | |
275 | ||
276 | if (err) | |
277 | { | |
278 | fprintf (stderr, "for PHI node\n"); | |
279 | debug_generic_stmt (phi); | |
280 | } | |
281 | ||
282 | ||
283 | return err; | |
284 | } | |
285 | ||
286 | ||
287 | /* Verify common invariants in the SSA web. | |
288 | TODO: verify the variable annotations. */ | |
289 | ||
290 | void | |
291 | verify_ssa (void) | |
292 | { | |
293 | bool err = false; | |
294 | basic_block bb; | |
295 | basic_block *definition_block = xcalloc (highest_ssa_version, | |
296 | sizeof (basic_block)); | |
297 | ||
298 | timevar_push (TV_TREE_SSA_VERIFY); | |
299 | ||
300 | calculate_dominance_info (CDI_DOMINATORS); | |
301 | ||
302 | /* Verify and register all the SSA_NAME definitions found in the | |
303 | function. */ | |
304 | FOR_EACH_BB (bb) | |
305 | { | |
306 | tree phi; | |
307 | block_stmt_iterator bsi; | |
308 | ||
309 | for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi)) | |
310 | err |= verify_def (bb, definition_block, PHI_RESULT (phi), phi); | |
311 | ||
312 | for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) | |
313 | { | |
314 | tree stmt; | |
315 | stmt_ann_t ann; | |
316 | unsigned int j; | |
317 | vdef_optype vdefs; | |
318 | def_optype defs; | |
319 | ||
320 | stmt = bsi_stmt (bsi); | |
321 | ann = stmt_ann (stmt); | |
322 | get_stmt_operands (stmt); | |
323 | ||
324 | vdefs = VDEF_OPS (ann); | |
325 | for (j = 0; j < NUM_VDEFS (vdefs); j++) | |
326 | { | |
327 | tree op = VDEF_RESULT (vdefs, j); | |
328 | if (is_gimple_reg (op)) | |
329 | { | |
330 | error ("Found a virtual definition for a GIMPLE register"); | |
331 | debug_generic_stmt (op); | |
332 | debug_generic_stmt (stmt); | |
333 | err = true; | |
334 | } | |
335 | err |= verify_def (bb, definition_block, op, stmt); | |
336 | } | |
337 | ||
338 | defs = DEF_OPS (ann); | |
339 | for (j = 0; j < NUM_DEFS (defs); j++) | |
340 | { | |
341 | tree op = DEF_OP (defs, j); | |
342 | if (TREE_CODE (op) == SSA_NAME && !is_gimple_reg (op)) | |
343 | { | |
344 | error ("Found a real definition for a non-GIMPLE register"); | |
345 | debug_generic_stmt (op); | |
346 | debug_generic_stmt (stmt); | |
347 | err = true; | |
348 | } | |
349 | err |= verify_def (bb, definition_block, op, stmt); | |
350 | } | |
351 | } | |
352 | } | |
353 | ||
354 | ||
355 | /* Now verify all the uses and make sure they agree with the definitions | |
356 | found in the previous pass. */ | |
357 | FOR_EACH_BB (bb) | |
358 | { | |
359 | edge e; | |
360 | tree phi; | |
361 | block_stmt_iterator bsi; | |
362 | ||
363 | /* Make sure that all edges have a clear 'aux' field. */ | |
364 | for (e = bb->pred; e; e = e->pred_next) | |
365 | { | |
366 | if (e->aux) | |
367 | { | |
368 | error ("AUX pointer initialized for edge %d->%d\n", e->src->index, | |
369 | e->dest->index); | |
370 | err = true; | |
371 | } | |
372 | } | |
373 | ||
374 | /* Verify the arguments for every PHI node in the block. */ | |
375 | for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi)) | |
376 | err |= verify_phi_args (phi, bb, definition_block); | |
377 | ||
378 | /* Now verify all the uses and vuses in every statement of the block. | |
379 | ||
380 | Remember, the RHS of a VDEF is a use as well. */ | |
381 | for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) | |
382 | { | |
383 | tree stmt = bsi_stmt (bsi); | |
384 | stmt_ann_t ann = stmt_ann (stmt); | |
385 | unsigned int j; | |
386 | vuse_optype vuses; | |
387 | vdef_optype vdefs; | |
388 | use_optype uses; | |
389 | ||
390 | vuses = VUSE_OPS (ann); | |
391 | for (j = 0; j < NUM_VUSES (vuses); j++) | |
392 | { | |
393 | tree op = VUSE_OP (vuses, j); | |
394 | ||
395 | if (is_gimple_reg (op)) | |
396 | { | |
397 | error ("Found a virtual use for a GIMPLE register"); | |
398 | debug_generic_stmt (op); | |
399 | debug_generic_stmt (stmt); | |
400 | err = true; | |
401 | } | |
402 | err |= verify_use (bb, definition_block[SSA_NAME_VERSION (op)], | |
403 | op, stmt, false); | |
404 | } | |
405 | ||
406 | vdefs = VDEF_OPS (ann); | |
407 | for (j = 0; j < NUM_VDEFS (vdefs); j++) | |
408 | { | |
409 | tree op = VDEF_OP (vdefs, j); | |
410 | ||
411 | if (is_gimple_reg (op)) | |
412 | { | |
413 | error ("Found a virtual use for a GIMPLE register"); | |
414 | debug_generic_stmt (op); | |
415 | debug_generic_stmt (stmt); | |
416 | err = true; | |
417 | } | |
418 | err |= verify_use (bb, definition_block[SSA_NAME_VERSION (op)], | |
419 | op, stmt, false); | |
420 | } | |
421 | ||
422 | uses = USE_OPS (ann); | |
423 | for (j = 0; j < NUM_USES (uses); j++) | |
424 | { | |
425 | tree op = USE_OP (uses, j); | |
426 | ||
427 | if (TREE_CODE (op) == SSA_NAME && !is_gimple_reg (op)) | |
428 | { | |
429 | error ("Found a real use of a non-GIMPLE register"); | |
430 | debug_generic_stmt (op); | |
431 | debug_generic_stmt (stmt); | |
432 | err = true; | |
433 | } | |
434 | err |= verify_use (bb, definition_block[SSA_NAME_VERSION (op)], | |
435 | op, stmt, false); | |
436 | } | |
437 | } | |
438 | } | |
439 | ||
440 | free (definition_block); | |
441 | ||
442 | timevar_pop (TV_TREE_SSA_VERIFY); | |
443 | ||
444 | if (err) | |
445 | internal_error ("verify_ssa failed."); | |
446 | } | |
447 | ||
448 | ||
449 | /* Set the USED bit in the annotation for T. */ | |
450 | ||
451 | void | |
452 | set_is_used (tree t) | |
453 | { | |
454 | while (1) | |
455 | { | |
456 | if (SSA_VAR_P (t)) | |
457 | break; | |
458 | ||
459 | switch (TREE_CODE (t)) | |
460 | { | |
461 | case ARRAY_REF: | |
462 | case COMPONENT_REF: | |
463 | case REALPART_EXPR: | |
464 | case IMAGPART_EXPR: | |
465 | case BIT_FIELD_REF: | |
466 | case INDIRECT_REF: | |
467 | t = TREE_OPERAND (t, 0); | |
468 | break; | |
469 | ||
470 | default: | |
471 | return; | |
472 | } | |
473 | } | |
474 | ||
475 | if (TREE_CODE (t) == SSA_NAME) | |
476 | t = SSA_NAME_VAR (t); | |
477 | ||
478 | var_ann (t)->used = 1; | |
479 | } | |
480 | ||
481 | ||
482 | /* Initialize global DFA and SSA structures. */ | |
483 | ||
484 | void | |
485 | init_tree_ssa (void) | |
486 | { | |
487 | VARRAY_TREE_INIT (referenced_vars, 20, "referenced_vars"); | |
488 | call_clobbered_vars = BITMAP_XMALLOC (); | |
489 | init_ssa_operands (); | |
490 | init_ssanames (); | |
491 | init_phinodes (); | |
492 | global_var = NULL_TREE; | |
493 | aliases_computed_p = false; | |
494 | } | |
495 | ||
496 | ||
497 | /* Deallocate memory associated with SSA data structures for FNDECL. */ | |
498 | ||
499 | void | |
500 | delete_tree_ssa (void) | |
501 | { | |
502 | size_t i; | |
503 | basic_block bb; | |
504 | block_stmt_iterator bsi; | |
505 | ||
506 | /* Remove annotations from every tree in the function. */ | |
507 | FOR_EACH_BB (bb) | |
508 | for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) | |
509 | bsi_stmt (bsi)->common.ann = NULL; | |
510 | ||
511 | /* Remove annotations from every referenced variable. */ | |
512 | if (referenced_vars) | |
513 | { | |
514 | for (i = 0; i < num_referenced_vars; i++) | |
515 | referenced_var (i)->common.ann = NULL; | |
516 | referenced_vars = NULL; | |
517 | } | |
518 | ||
519 | fini_ssanames (); | |
520 | fini_phinodes (); | |
521 | fini_ssa_operands (); | |
522 | ||
523 | global_var = NULL_TREE; | |
6b9bee8e | 524 | BITMAP_XFREE (call_clobbered_vars); |
6de9cd9a DN |
525 | call_clobbered_vars = NULL; |
526 | aliases_computed_p = false; | |
527 | } | |
528 | ||
529 | ||
530 | /* Return true if EXPR is a useless type conversion, otherwise return | |
531 | false. */ | |
532 | ||
533 | bool | |
534 | tree_ssa_useless_type_conversion_1 (tree outer_type, tree inner_type) | |
535 | { | |
536 | /* If the inner and outer types are effectively the same, then | |
537 | strip the type conversion and enter the equivalence into | |
538 | the table. */ | |
539 | if (inner_type == outer_type | |
540 | || (lang_hooks.types_compatible_p (inner_type, outer_type))) | |
541 | return true; | |
542 | ||
543 | /* If both types are pointers and the outer type is a (void *), then | |
544 | the conversion is not necessary. The opposite is not true since | |
545 | that conversion would result in a loss of information if the | |
546 | equivalence was used. Consider an indirect function call where | |
547 | we need to know the exact type of the function to correctly | |
548 | implement the ABI. */ | |
549 | else if (POINTER_TYPE_P (inner_type) | |
550 | && POINTER_TYPE_P (outer_type) | |
551 | && TREE_CODE (TREE_TYPE (outer_type)) == VOID_TYPE) | |
552 | return true; | |
553 | ||
554 | /* Pointers and references are equivalent once we get to GENERIC, | |
555 | so strip conversions that just switch between them. */ | |
556 | else if (POINTER_TYPE_P (inner_type) | |
557 | && POINTER_TYPE_P (outer_type) | |
558 | && lang_hooks.types_compatible_p (inner_type, outer_type)) | |
559 | return true; | |
560 | ||
561 | /* If both the inner and outer types are integral types, then the | |
562 | conversion is not necessary if they have the same mode and | |
563 | signedness and precision. Note that type _Bool can have size of | |
564 | 4 (only happens on powerpc-darwin right now but can happen on any | |
565 | target that defines BOOL_TYPE_SIZE to be INT_TYPE_SIZE) and a | |
566 | precision of 1 while unsigned int is the same expect for a | |
567 | precision of 4 so testing of precision is necessary. */ | |
568 | else if (INTEGRAL_TYPE_P (inner_type) | |
569 | && INTEGRAL_TYPE_P (outer_type) | |
570 | && TYPE_MODE (inner_type) == TYPE_MODE (outer_type) | |
571 | && TYPE_UNSIGNED (inner_type) == TYPE_UNSIGNED (outer_type) | |
572 | && TYPE_PRECISION (inner_type) == TYPE_PRECISION (outer_type)) | |
573 | return true; | |
574 | ||
575 | /* Recurse for complex types. */ | |
576 | else if (TREE_CODE (inner_type) == COMPLEX_TYPE | |
577 | && TREE_CODE (outer_type) == COMPLEX_TYPE | |
578 | && tree_ssa_useless_type_conversion_1 (TREE_TYPE (outer_type), | |
579 | TREE_TYPE (inner_type))) | |
580 | return true; | |
581 | ||
582 | return false; | |
583 | } | |
584 | ||
585 | /* Return true if EXPR is a useless type conversion, otherwise return | |
586 | false. */ | |
587 | ||
588 | bool | |
589 | tree_ssa_useless_type_conversion (tree expr) | |
590 | { | |
591 | /* If we have an assignment that merely uses a NOP_EXPR to change | |
592 | the top of the RHS to the type of the LHS and the type conversion | |
593 | is "safe", then strip away the type conversion so that we can | |
594 | enter LHS = RHS into the const_and_copies table. */ | |
595 | if (TREE_CODE (expr) == NOP_EXPR || TREE_CODE (expr) == CONVERT_EXPR) | |
596 | return tree_ssa_useless_type_conversion_1 (TREE_TYPE (expr), | |
597 | TREE_TYPE (TREE_OPERAND (expr, | |
598 | 0))); | |
599 | ||
600 | ||
601 | return false; | |
602 | } | |
603 | ||
604 | ||
605 | /* Internal helper for walk_use_def_chains. VAR, FN and DATA are as | |
606 | described in walk_use_def_chains. VISITED is a bitmap used to mark | |
607 | visited SSA_NAMEs to avoid infinite loops. */ | |
608 | ||
609 | static bool | |
610 | walk_use_def_chains_1 (tree var, walk_use_def_chains_fn fn, void *data, | |
611 | bitmap visited) | |
612 | { | |
613 | tree def_stmt; | |
614 | ||
615 | if (bitmap_bit_p (visited, SSA_NAME_VERSION (var))) | |
616 | return false; | |
617 | ||
618 | bitmap_set_bit (visited, SSA_NAME_VERSION (var)); | |
619 | ||
620 | def_stmt = SSA_NAME_DEF_STMT (var); | |
621 | ||
622 | if (TREE_CODE (def_stmt) != PHI_NODE) | |
623 | { | |
624 | /* If we reached the end of the use-def chain, call FN. */ | |
625 | return (*fn) (var, def_stmt, data); | |
626 | } | |
627 | else | |
628 | { | |
629 | int i; | |
630 | ||
631 | /* Otherwise, follow use-def links out of each PHI argument and call | |
632 | FN after visiting each one. */ | |
633 | for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++) | |
634 | { | |
635 | tree arg = PHI_ARG_DEF (def_stmt, i); | |
636 | if (TREE_CODE (arg) == SSA_NAME | |
637 | && walk_use_def_chains_1 (arg, fn, data, visited)) | |
638 | return true; | |
639 | ||
640 | if ((*fn) (arg, def_stmt, data)) | |
641 | return true; | |
642 | } | |
643 | } | |
644 | return false; | |
645 | } | |
646 | ||
647 | ||
648 | ||
649 | /* Walk use-def chains starting at the SSA variable VAR. Call function FN | |
650 | at each reaching definition found. FN takes three arguments: VAR, its | |
651 | defining statement (DEF_STMT) and a generic pointer to whatever state | |
652 | information that FN may want to maintain (DATA). FN is able to stop the | |
653 | walk by returning true, otherwise in order to continue the walk, FN | |
654 | should return false. | |
655 | ||
656 | Note, that if DEF_STMT is a PHI node, the semantics are slightly | |
657 | different. For each argument ARG of the PHI node, this function will: | |
658 | ||
659 | 1- Walk the use-def chains for ARG. | |
660 | 2- Call (*FN) (ARG, PHI, DATA). | |
661 | ||
662 | Note how the first argument to FN is no longer the original variable | |
663 | VAR, but the PHI argument currently being examined. If FN wants to get | |
664 | at VAR, it should call PHI_RESULT (PHI). */ | |
665 | ||
666 | void | |
667 | walk_use_def_chains (tree var, walk_use_def_chains_fn fn, void *data) | |
668 | { | |
669 | tree def_stmt; | |
670 | ||
671 | #if defined ENABLE_CHECKING | |
672 | if (TREE_CODE (var) != SSA_NAME) | |
673 | abort (); | |
674 | #endif | |
675 | ||
676 | def_stmt = SSA_NAME_DEF_STMT (var); | |
677 | ||
678 | /* We only need to recurse if the reaching definition comes from a PHI | |
679 | node. */ | |
680 | if (TREE_CODE (def_stmt) != PHI_NODE) | |
681 | (*fn) (var, def_stmt, data); | |
682 | else | |
683 | { | |
684 | bitmap visited = BITMAP_XMALLOC (); | |
685 | walk_use_def_chains_1 (var, fn, data, visited); | |
686 | BITMAP_XFREE (visited); | |
687 | } | |
688 | } | |
689 | ||
690 | ||
691 | /* Replaces immediate uses of VAR by REPL. */ | |
692 | ||
693 | static void | |
694 | replace_immediate_uses (tree var, tree repl) | |
695 | { | |
696 | use_optype uses; | |
697 | vuse_optype vuses; | |
698 | vdef_optype vdefs; | |
699 | int i, j, n; | |
700 | dataflow_t df; | |
701 | tree stmt; | |
702 | stmt_ann_t ann; | |
703 | ||
704 | df = get_immediate_uses (SSA_NAME_DEF_STMT (var)); | |
705 | n = num_immediate_uses (df); | |
706 | ||
707 | for (i = 0; i < n; i++) | |
708 | { | |
709 | stmt = immediate_use (df, i); | |
710 | ann = stmt_ann (stmt); | |
711 | ||
712 | if (TREE_CODE (stmt) == PHI_NODE) | |
713 | { | |
714 | for (j = 0; j < PHI_NUM_ARGS (stmt); j++) | |
715 | if (PHI_ARG_DEF (stmt, j) == var) | |
716 | { | |
717 | PHI_ARG_DEF (stmt, j) = repl; | |
718 | if (TREE_CODE (repl) == SSA_NAME | |
719 | && PHI_ARG_EDGE (stmt, j)->flags & EDGE_ABNORMAL) | |
720 | SSA_NAME_OCCURS_IN_ABNORMAL_PHI (repl) = 1; | |
721 | } | |
722 | ||
723 | continue; | |
724 | } | |
725 | ||
726 | get_stmt_operands (stmt); | |
727 | if (is_gimple_reg (SSA_NAME_VAR (var))) | |
728 | { | |
729 | uses = USE_OPS (ann); | |
730 | for (j = 0; j < (int) NUM_USES (uses); j++) | |
731 | if (USE_OP (uses, j) == var) | |
732 | propagate_value (USE_OP_PTR (uses, j), repl); | |
733 | } | |
734 | else | |
735 | { | |
736 | vuses = VUSE_OPS (ann); | |
737 | for (j = 0; j < (int) NUM_VUSES (vuses); j++) | |
738 | if (VUSE_OP (vuses, j) == var) | |
739 | propagate_value (VUSE_OP_PTR (vuses, j), repl); | |
740 | ||
741 | vdefs = VDEF_OPS (ann); | |
742 | for (j = 0; j < (int) NUM_VDEFS (vdefs); j++) | |
743 | if (VDEF_OP (vdefs, j) == var) | |
744 | propagate_value (VDEF_OP_PTR (vdefs, j), repl); | |
745 | } | |
746 | ||
747 | modify_stmt (stmt); | |
748 | ||
749 | /* If REPL is a pointer, it may have different memory tags associated | |
750 | with it. For instance, VAR may have had a name tag while REPL | |
751 | only had a type tag. In these cases, the virtual operands (if | |
752 | any) in the statement will refer to different symbols which need | |
753 | to be renamed. */ | |
754 | if (POINTER_TYPE_P (TREE_TYPE (repl))) | |
755 | mark_new_vars_to_rename (stmt, vars_to_rename); | |
756 | } | |
757 | } | |
758 | ||
759 | /* Raises value of phi node PHI by joining it with VAL. Processes immediate | |
760 | uses of PHI recursively. */ | |
761 | ||
762 | static void | |
763 | raise_value (tree phi, tree val, tree *eq_to) | |
764 | { | |
765 | int i, n; | |
766 | tree var = PHI_RESULT (phi), stmt; | |
767 | int ver = SSA_NAME_VERSION (var); | |
768 | dataflow_t df; | |
769 | ||
770 | if (eq_to[ver] == var) | |
771 | return; | |
772 | ||
773 | switch (TREE_CODE (val)) | |
774 | { | |
775 | case SSA_NAME: | |
776 | case REAL_CST: | |
777 | case COMPLEX_CST: | |
778 | break; | |
779 | case INTEGER_CST: | |
780 | if (TREE_CODE (TREE_TYPE (var)) != POINTER_TYPE) | |
781 | break; | |
782 | ||
783 | default: | |
784 | /* Do not propagate pointer constants. This might require folding | |
785 | things like *&foo and rewriting the ssa, which is not worth the | |
786 | trouble. */ | |
787 | val = var; | |
788 | } | |
789 | ||
790 | if (eq_to[ver]) | |
791 | { | |
792 | if (operand_equal_p (eq_to[ver], val, 0)) | |
793 | return; | |
794 | ||
795 | eq_to[ver] = var; | |
796 | } | |
797 | else | |
798 | eq_to[ver] = val; | |
799 | ||
800 | df = get_immediate_uses (SSA_NAME_DEF_STMT (var)); | |
801 | n = num_immediate_uses (df); | |
802 | ||
803 | for (i = 0; i < n; i++) | |
804 | { | |
805 | stmt = immediate_use (df, i); | |
806 | ||
807 | if (TREE_CODE (stmt) != PHI_NODE) | |
808 | continue; | |
809 | ||
810 | raise_value (stmt, eq_to[ver], eq_to); | |
811 | } | |
812 | } | |
813 | ||
814 | /* Removes redundant phi nodes. | |
815 | ||
816 | A redundant PHI node is a PHI node where all of its PHI arguments | |
817 | are the same value, excluding any PHI arguments which are the same | |
818 | as the PHI result. | |
819 | ||
820 | A redundant PHI node is effectively a copy, so we forward copy propagate | |
821 | which removes all uses of the destination of the PHI node then | |
822 | finally we delete the redundant PHI node. | |
823 | ||
824 | Note that if we can not copy propagate the PHI node, then the PHI | |
825 | will not be removed. Thus we do not have to worry about dependencies | |
826 | between PHIs and the problems serializing PHIs into copies creates. | |
827 | ||
828 | The most important effect of this pass is to remove degenerate PHI | |
829 | nodes created by removing unreachable code. */ | |
830 | ||
831 | static void | |
832 | kill_redundant_phi_nodes (void) | |
833 | { | |
834 | tree *eq_to, *ssa_names; | |
835 | unsigned i, ver, aver; | |
836 | basic_block bb; | |
837 | tree phi, t, stmt, var; | |
838 | ||
839 | /* The EQ_TO array holds the current value of the ssa name in the | |
840 | lattice: | |
841 | ||
842 | top | |
843 | / | \ | |
844 | const variables | |
845 | \ | / | |
846 | bottom | |
847 | ||
848 | Bottom is represented by NULL and top by the variable itself. | |
849 | ||
850 | Once the dataflow stabilizes, we know that the phi nodes we need to keep | |
851 | are exactly those with top as their result. | |
852 | ||
853 | The remaining phi nodes have their uses replaced with their value | |
854 | in the lattice and the phi node itself is removed. */ | |
855 | eq_to = xcalloc (highest_ssa_version, sizeof (tree)); | |
856 | ||
857 | /* The SSA_NAMES array holds each SSA_NAME node we encounter | |
858 | in a PHI node (indexed by ssa version number). | |
859 | ||
860 | One could argue that the SSA_NAME manager ought to provide a | |
861 | generic interface to get at the SSA_NAME node for a given | |
862 | ssa version number. */ | |
863 | ssa_names = xcalloc (highest_ssa_version, sizeof (tree)); | |
864 | ||
865 | /* We have had cases where computing immediate uses takes a | |
866 | significant amount of compile time. If we run into such | |
867 | problems here, we may want to only compute immediate uses for | |
868 | a subset of all the SSA_NAMEs instead of computing it for | |
869 | all of the SSA_NAMEs. */ | |
870 | compute_immediate_uses (TDFA_USE_OPS | TDFA_USE_VOPS, NULL); | |
871 | ||
872 | FOR_EACH_BB (bb) | |
873 | { | |
874 | for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi)) | |
875 | { | |
876 | var = PHI_RESULT (phi); | |
877 | ver = SSA_NAME_VERSION (var); | |
878 | ssa_names[ver] = var; | |
879 | ||
880 | for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++) | |
881 | { | |
882 | t = PHI_ARG_DEF (phi, i); | |
883 | ||
884 | if (TREE_CODE (t) != SSA_NAME) | |
885 | { | |
886 | raise_value (phi, t, eq_to); | |
887 | continue; | |
888 | } | |
889 | ||
890 | stmt = SSA_NAME_DEF_STMT (t); | |
891 | aver = SSA_NAME_VERSION (t); | |
892 | ssa_names[aver] = t; | |
893 | ||
894 | /* If the defining statement for this argument is not a | |
895 | phi node or the argument is associated with an abnormal | |
896 | edge, then we need to recursively start the forward | |
897 | dataflow starting with PHI. */ | |
898 | if (TREE_CODE (stmt) != PHI_NODE | |
899 | || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (t)) | |
900 | { | |
901 | eq_to[aver] = t; | |
902 | raise_value (phi, t, eq_to); | |
903 | } | |
904 | } | |
905 | } | |
906 | } | |
907 | ||
908 | /* Now propagate the values. */ | |
909 | for (i = 0; i < highest_ssa_version; i++) | |
910 | if (eq_to[i] | |
911 | && eq_to[i] != ssa_names[i]) | |
912 | replace_immediate_uses (ssa_names[i], eq_to[i]); | |
913 | ||
914 | /* And remove the dead phis. */ | |
915 | for (i = 0; i < highest_ssa_version; i++) | |
916 | if (eq_to[i] | |
917 | && eq_to[i] != ssa_names[i]) | |
918 | { | |
919 | stmt = SSA_NAME_DEF_STMT (ssa_names[i]); | |
920 | remove_phi_node (stmt, 0, bb_for_stmt (stmt)); | |
921 | } | |
922 | ||
923 | free_df (); | |
924 | free (eq_to); | |
925 | free (ssa_names); | |
926 | } | |
927 | ||
928 | struct tree_opt_pass pass_redundant_phi = | |
929 | { | |
930 | "redphi", /* name */ | |
931 | NULL, /* gate */ | |
932 | kill_redundant_phi_nodes, /* execute */ | |
933 | NULL, /* sub */ | |
934 | NULL, /* next */ | |
935 | 0, /* static_pass_number */ | |
936 | 0, /* tv_id */ | |
937 | PROP_cfg | PROP_ssa, /* properties_required */ | |
938 | 0, /* properties_provided */ | |
939 | 0, /* properties_destroyed */ | |
940 | 0, /* todo_flags_start */ | |
941 | TODO_dump_func | TODO_rename_vars | |
942 | | TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */ | |
943 | }; | |
944 | \f | |
945 | /* Emit warnings for uninitialized variables. This is done in two passes. | |
946 | ||
947 | The first pass notices real uses of SSA names with default definitions. | |
948 | Such uses are unconditionally uninitialized, and we can be certain that | |
949 | such a use is a mistake. This pass is run before most optimizations, | |
950 | so that we catch as many as we can. | |
951 | ||
952 | The second pass follows PHI nodes to find uses that are potentially | |
953 | uninitialized. In this case we can't necessarily prove that the use | |
954 | is really uninitialized. This pass is run after most optimizations, | |
955 | so that we thread as many jumps and possible, and delete as much dead | |
956 | code as possible, in order to reduce false positives. We also look | |
957 | again for plain uninitialized variables, since optimization may have | |
958 | changed conditionally uninitialized to unconditionally uninitialized. */ | |
959 | ||
960 | /* Emit a warning for T, an SSA_NAME, being uninitialized. The exact | |
961 | warning text is in MSGID and LOCUS may contain a location or be null. */ | |
962 | ||
963 | static void | |
964 | warn_uninit (tree t, const char *msgid, location_t *locus) | |
965 | { | |
966 | tree var = SSA_NAME_VAR (t); | |
967 | tree def = SSA_NAME_DEF_STMT (t); | |
968 | ||
969 | /* Default uses (indicated by an empty definition statement), | |
970 | are uninitialized. */ | |
971 | if (!IS_EMPTY_STMT (def)) | |
972 | return; | |
973 | ||
974 | /* Except for PARMs of course, which are always initialized. */ | |
975 | if (TREE_CODE (var) == PARM_DECL) | |
976 | return; | |
977 | ||
978 | /* Hard register variables get their initial value from the ether. */ | |
979 | if (DECL_HARD_REGISTER (var)) | |
980 | return; | |
981 | ||
982 | /* TREE_NO_WARNING either means we already warned, or the front end | |
983 | wishes to suppress the warning. */ | |
984 | if (TREE_NO_WARNING (var)) | |
985 | return; | |
986 | ||
987 | if (!locus) | |
988 | locus = &DECL_SOURCE_LOCATION (var); | |
989 | warning (msgid, locus, var); | |
990 | TREE_NO_WARNING (var) = 1; | |
991 | } | |
992 | ||
993 | /* Called via walk_tree, look for SSA_NAMEs that have empty definitions | |
994 | and warn about them. */ | |
995 | ||
996 | static tree | |
997 | warn_uninitialized_var (tree *tp, int *walk_subtrees, void *data) | |
998 | { | |
999 | location_t *locus = data; | |
1000 | tree t = *tp; | |
1001 | ||
1002 | /* We only do data flow with SSA_NAMEs, so that's all we can warn about. */ | |
1003 | if (TREE_CODE (t) == SSA_NAME) | |
1004 | { | |
1005 | warn_uninit (t, "%H'%D' is used uninitialized in this function", locus); | |
1006 | *walk_subtrees = 0; | |
1007 | } | |
1008 | else if (DECL_P (t) || TYPE_P (t)) | |
1009 | *walk_subtrees = 0; | |
1010 | ||
1011 | return NULL_TREE; | |
1012 | } | |
1013 | ||
1014 | /* Look for inputs to PHI that are SSA_NAMEs that have empty definitions | |
1015 | and warn about them. */ | |
1016 | ||
1017 | static void | |
1018 | warn_uninitialized_phi (tree phi) | |
1019 | { | |
1020 | int i, n = PHI_NUM_ARGS (phi); | |
1021 | ||
1022 | /* Don't look at memory tags. */ | |
1023 | if (!is_gimple_reg (PHI_RESULT (phi))) | |
1024 | return; | |
1025 | ||
1026 | for (i = 0; i < n; ++i) | |
1027 | { | |
1028 | tree op = PHI_ARG_DEF (phi, i); | |
1029 | if (TREE_CODE (op) == SSA_NAME) | |
1030 | warn_uninit (op, "%H'%D' may be used uninitialized in this function", | |
1031 | NULL); | |
1032 | } | |
1033 | } | |
1034 | ||
1035 | static void | |
1036 | execute_early_warn_uninitialized (void) | |
1037 | { | |
1038 | block_stmt_iterator bsi; | |
1039 | basic_block bb; | |
1040 | ||
1041 | FOR_EACH_BB (bb) | |
1042 | for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) | |
1043 | walk_tree (bsi_stmt_ptr (bsi), warn_uninitialized_var, | |
1044 | EXPR_LOCUS (bsi_stmt (bsi)), NULL); | |
1045 | } | |
1046 | ||
1047 | static void | |
1048 | execute_late_warn_uninitialized (void) | |
1049 | { | |
1050 | basic_block bb; | |
1051 | tree phi; | |
1052 | ||
1053 | /* Re-do the plain uninitialized variable check, as optimization may have | |
1054 | straightened control flow. Do this first so that we don't accidentally | |
1055 | get a "may be" warning when we'd have seen an "is" warning later. */ | |
1056 | execute_early_warn_uninitialized (); | |
1057 | ||
1058 | FOR_EACH_BB (bb) | |
1059 | for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi)) | |
1060 | warn_uninitialized_phi (phi); | |
1061 | } | |
1062 | ||
1063 | static bool | |
1064 | gate_warn_uninitialized (void) | |
1065 | { | |
1066 | return warn_uninitialized != 0; | |
1067 | } | |
1068 | ||
1069 | struct tree_opt_pass pass_early_warn_uninitialized = | |
1070 | { | |
1071 | NULL, /* name */ | |
1072 | gate_warn_uninitialized, /* gate */ | |
1073 | execute_early_warn_uninitialized, /* execute */ | |
1074 | NULL, /* sub */ | |
1075 | NULL, /* next */ | |
1076 | 0, /* static_pass_number */ | |
1077 | 0, /* tv_id */ | |
1078 | PROP_ssa, /* properties_required */ | |
1079 | 0, /* properties_provided */ | |
1080 | 0, /* properties_destroyed */ | |
1081 | 0, /* todo_flags_start */ | |
1082 | 0 /* todo_flags_finish */ | |
1083 | }; | |
1084 | ||
1085 | struct tree_opt_pass pass_late_warn_uninitialized = | |
1086 | { | |
1087 | NULL, /* name */ | |
1088 | gate_warn_uninitialized, /* gate */ | |
1089 | execute_late_warn_uninitialized, /* execute */ | |
1090 | NULL, /* sub */ | |
1091 | NULL, /* next */ | |
1092 | 0, /* static_pass_number */ | |
1093 | 0, /* tv_id */ | |
1094 | PROP_ssa, /* properties_required */ | |
1095 | 0, /* properties_provided */ | |
1096 | 0, /* properties_destroyed */ | |
1097 | 0, /* todo_flags_start */ | |
1098 | 0 /* todo_flags_finish */ | |
1099 | }; |