1 /* Alias analysis for trees.
2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009
3 Free Software Foundation, Inc.
4 Contributed by Diego Novillo <dnovillo@redhat.com>
6 This file is part of GCC.
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
10 the Free Software Foundation; either version 3, or (at your option)
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.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
24 #include "coretypes.h"
29 #include "hard-reg-set.h"
30 #include "basic-block.h"
34 #include "langhooks.h"
37 #include "diagnostic.h"
38 #include "tree-dump.h"
40 #include "tree-flow.h"
41 #include "tree-inline.h"
42 #include "tree-pass.h"
45 #include "ipa-type-escape.h"
49 #include "pointer-set.h"
50 #include "alloc-pool.h"
51 #include "tree-ssa-alias.h"
53 /* Broad overview of how alias analysis on gimple works:
55 Statements clobbering or using memory are linked through the
56 virtual operand factored use-def chain. The virtual operand
57 is unique per function, its symbol is accessible via gimple_vop (cfun).
58 Virtual operands are used for efficiently walking memory statements
59 in the gimple IL and are useful for things like value-numbering as
60 a generation count for memory references.
62 SSA_NAME pointers may have associated points-to information
63 accessible via the SSA_NAME_PTR_INFO macro. Flow-insensitive
64 points-to information is (re-)computed by the TODO_rebuild_alias
65 pass manager todo. Points-to information is also used for more
66 precise tracking of call-clobbered and call-used variables and
67 related disambiguations.
69 This file contains functions for disambiguating memory references,
70 the so called alias-oracle and tools for walking of the gimple IL.
72 The main alias-oracle entry-points are
74 bool stmt_may_clobber_ref_p (gimple, tree)
76 This function queries if a statement may invalidate (parts of)
77 the memory designated by the reference tree argument.
79 bool ref_maybe_used_by_stmt_p (gimple, tree)
81 This function queries if a statement may need (parts of) the
82 memory designated by the reference tree argument.
84 There are variants of these functions that only handle the call
85 part of a statement, call_may_clobber_ref_p and ref_maybe_used_by_call_p.
86 Note that these do not disambiguate against a possible call lhs.
88 bool refs_may_alias_p (tree, tree)
90 This function tries to disambiguate two reference trees.
92 bool ptr_deref_may_alias_global_p (tree)
94 This function queries if dereferencing a pointer variable may
97 More low-level disambiguators are available and documented in
98 this file. Low-level disambiguators dealing with points-to
99 information are in tree-ssa-structalias.c. */
102 /* Query statistics for the different low-level disambiguators.
103 A high-level query may trigger multiple of them. */
106 unsigned HOST_WIDE_INT refs_may_alias_p_may_alias;
107 unsigned HOST_WIDE_INT refs_may_alias_p_no_alias;
108 unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_may_alias;
109 unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_no_alias;
110 unsigned HOST_WIDE_INT call_may_clobber_ref_p_may_alias;
111 unsigned HOST_WIDE_INT call_may_clobber_ref_p_no_alias;
115 dump_alias_stats (FILE *s)
117 fprintf (s, "\nAlias oracle query stats:\n");
118 fprintf (s, " refs_may_alias_p: "
119 HOST_WIDE_INT_PRINT_DEC" disambiguations, "
120 HOST_WIDE_INT_PRINT_DEC" queries\n",
121 alias_stats.refs_may_alias_p_no_alias,
122 alias_stats.refs_may_alias_p_no_alias
123 + alias_stats.refs_may_alias_p_may_alias);
124 fprintf (s, " ref_maybe_used_by_call_p: "
125 HOST_WIDE_INT_PRINT_DEC" disambiguations, "
126 HOST_WIDE_INT_PRINT_DEC" queries\n",
127 alias_stats.ref_maybe_used_by_call_p_no_alias,
128 alias_stats.refs_may_alias_p_no_alias
129 + alias_stats.ref_maybe_used_by_call_p_may_alias);
130 fprintf (s, " call_may_clobber_ref_p: "
131 HOST_WIDE_INT_PRINT_DEC" disambiguations, "
132 HOST_WIDE_INT_PRINT_DEC" queries\n",
133 alias_stats.call_may_clobber_ref_p_no_alias,
134 alias_stats.call_may_clobber_ref_p_no_alias
135 + alias_stats.call_may_clobber_ref_p_may_alias);
139 /* Return true, if dereferencing PTR may alias with a global variable. */
142 ptr_deref_may_alias_global_p (tree ptr)
144 struct ptr_info_def *pi;
146 /* If we end up with a pointer constant here that may point
148 if (TREE_CODE (ptr) != SSA_NAME)
151 pi = SSA_NAME_PTR_INFO (ptr);
153 /* If we do not have points-to information for this variable,
158 return pt_solution_includes_global (&pi->pt);
161 /* Return true if dereferencing PTR may alias DECL. */
164 ptr_deref_may_alias_decl_p (tree ptr, tree decl)
166 struct ptr_info_def *pi;
168 /* ??? During SCCVN/PRE we can end up with *&x during valueizing
169 operands. Likewise we can end up with dereferencing constant
170 pointers. Just bail out in these cases for now. */
171 if (TREE_CODE (ptr) == ADDR_EXPR
172 || TREE_CODE (ptr) == INTEGER_CST)
175 gcc_assert (TREE_CODE (ptr) == SSA_NAME
176 && (TREE_CODE (decl) == VAR_DECL
177 || TREE_CODE (decl) == PARM_DECL
178 || TREE_CODE (decl) == RESULT_DECL));
180 /* Non-aliased variables can not be pointed to. */
181 if (!may_be_aliased (decl))
184 /* If we do not have useful points-to information for this pointer
185 we cannot disambiguate anything else. */
186 pi = SSA_NAME_PTR_INFO (ptr);
190 return pt_solution_includes (&pi->pt, decl);
193 /* Return true if dereferenced PTR1 and PTR2 may alias. */
196 ptr_derefs_may_alias_p (tree ptr1, tree ptr2)
198 struct ptr_info_def *pi1, *pi2;
200 /* ??? During SCCVN/PRE we can end up with *&x during valueizing
201 operands. Likewise we can end up with dereferencing constant
202 pointers. Just bail out in these cases for now. */
203 if (TREE_CODE (ptr1) == ADDR_EXPR
204 || TREE_CODE (ptr1) == INTEGER_CST
205 || TREE_CODE (ptr2) == ADDR_EXPR
206 || TREE_CODE (ptr2) == INTEGER_CST)
209 gcc_assert (TREE_CODE (ptr1) == SSA_NAME
210 && TREE_CODE (ptr2) == SSA_NAME);
212 /* We may end up with two empty points-to solutions for two same pointers.
213 In this case we still want to say both pointers alias, so shortcut
218 /* If we do not have useful points-to information for either pointer
219 we cannot disambiguate anything else. */
220 pi1 = SSA_NAME_PTR_INFO (ptr1);
221 pi2 = SSA_NAME_PTR_INFO (ptr2);
225 return pt_solutions_intersect (&pi1->pt, &pi2->pt);
228 /* Return true if STMT is an "escape" site from the current function. Escape
229 sites those statements which might expose the address of a variable
230 outside the current function. STMT is an escape site iff:
232 1- STMT is a function call, or
233 2- STMT is an __asm__ expression, or
234 3- STMT is an assignment to a non-local variable, or
235 4- STMT is a return statement.
237 Return the type of escape site found, if we found one, or NO_ESCAPE
241 is_escape_site (gimple stmt)
243 if (is_gimple_call (stmt))
245 if (gimple_call_flags (stmt) & (ECF_PURE | ECF_CONST))
246 return ESCAPE_TO_PURE_CONST;
248 return ESCAPE_TO_CALL;
250 else if (gimple_code (stmt) == GIMPLE_ASM)
251 return ESCAPE_TO_ASM;
252 else if (is_gimple_assign (stmt))
254 tree lhs = gimple_assign_lhs (stmt);
256 /* Get to the base of _REF nodes. */
257 if (TREE_CODE (lhs) != SSA_NAME)
258 lhs = get_base_address (lhs);
260 /* If we couldn't recognize the LHS of the assignment, assume that it
261 is a non-local store. */
262 if (lhs == NULL_TREE)
263 return ESCAPE_UNKNOWN;
265 if (gimple_assign_cast_p (stmt))
267 tree from = TREE_TYPE (gimple_assign_rhs1 (stmt));
268 tree to = TREE_TYPE (lhs);
270 /* If the RHS is a conversion between a pointer and an integer, the
271 pointer escapes since we can't track the integer. */
272 if (POINTER_TYPE_P (from) && !POINTER_TYPE_P (to))
273 return ESCAPE_BAD_CAST;
276 /* If the LHS is an SSA name, it can't possibly represent a non-local
278 if (TREE_CODE (lhs) == SSA_NAME)
281 /* If the LHS is a non-global decl, it isn't a non-local memory store.
282 If the LHS escapes, the RHS escape is dealt with in the PTA solver. */
284 && !is_global_var (lhs))
287 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
288 local variables we cannot be sure if it will escape, because we
289 don't have information about objects not in SSA form. Need to
290 implement something along the lines of
292 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
293 Midkiff, ``Escape analysis for java,'' in Proceedings of the
294 Conference on Object-Oriented Programming Systems, Languages, and
295 Applications (OOPSLA), pp. 1-19, 1999. */
296 return ESCAPE_STORED_IN_GLOBAL;
298 else if (gimple_code (stmt) == GIMPLE_RETURN)
299 return ESCAPE_TO_RETURN;
305 /* Dump alias information on FILE. */
308 dump_alias_info (FILE *file)
312 = lang_hooks.decl_printable_name (current_function_decl, 2);
313 referenced_var_iterator rvi;
316 fprintf (file, "\n\nAlias information for %s\n\n", funcname);
318 fprintf (file, "Aliased symbols\n\n");
320 FOR_EACH_REFERENCED_VAR (var, rvi)
322 if (may_be_aliased (var))
323 dump_variable (file, var);
326 fprintf (file, "\n\nFlow-insensitive points-to information for %s\n\n", funcname);
328 for (i = 1; i < num_ssa_names; i++)
330 tree ptr = ssa_name (i);
331 struct ptr_info_def *pi;
334 || SSA_NAME_IN_FREE_LIST (ptr))
337 pi = SSA_NAME_PTR_INFO (ptr);
339 dump_points_to_info_for (file, ptr);
342 fprintf (file, "\n");
346 /* Dump alias information on stderr. */
349 debug_alias_info (void)
351 dump_alias_info (stderr);
355 /* Return the alias information associated with pointer T. It creates a
356 new instance if none existed. */
358 struct ptr_info_def *
359 get_ptr_info (tree t)
361 struct ptr_info_def *pi;
363 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
365 pi = SSA_NAME_PTR_INFO (t);
368 pi = GGC_CNEW (struct ptr_info_def);
369 pt_solution_reset (&pi->pt);
370 SSA_NAME_PTR_INFO (t) = pi;
376 /* Dump points-to information for SSA_NAME PTR into FILE. */
379 dump_points_to_info_for (FILE *file, tree ptr)
381 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
383 print_generic_expr (file, ptr, dump_flags);
388 fprintf (file, ", points-to anything");
391 fprintf (file, ", points-to non-local");
394 fprintf (file, ", points-to escaped");
397 fprintf (file, ", points-to NULL");
401 fprintf (file, ", points-to vars: ");
402 dump_decl_set (file, pi->pt.vars);
403 if (pi->pt.vars_contains_global)
404 fprintf (file, " (includes global vars)");
408 fprintf (file, "\n");
412 /* Dump points-to information for VAR into stderr. */
415 debug_points_to_info_for (tree var)
417 dump_points_to_info_for (stderr, var);
420 /* Return 1 if TYPE1 and TYPE2 are to be considered equivalent for the
421 purpose of TBAA. Return 0 if they are distinct and -1 if we cannot
425 same_type_for_tbaa (tree type1, tree type2)
427 type1 = TYPE_MAIN_VARIANT (type1);
428 type2 = TYPE_MAIN_VARIANT (type2);
430 /* If we would have to do structural comparison bail out. */
431 if (TYPE_STRUCTURAL_EQUALITY_P (type1)
432 || TYPE_STRUCTURAL_EQUALITY_P (type2))
435 /* Compare the canonical types. */
436 if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2))
439 /* ??? Array types are not properly unified in all cases as we have
440 spurious changes in the index types for example. Removing this
441 causes all sorts of problems with the Fortran frontend. */
442 if (TREE_CODE (type1) == ARRAY_TYPE
443 && TREE_CODE (type2) == ARRAY_TYPE)
446 /* The types are known to be not equal. */
450 /* Determine if the two component references REF1 and REF2 which are
451 based on access types TYPE1 and TYPE2 and of which at least one is based
452 on an indirect reference may alias. */
455 nonaliasing_component_refs_p (tree ref1, tree type1,
456 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
457 tree ref2, tree type2,
458 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
460 /* If one reference is a component references through pointers try to find a
461 common base and apply offset based disambiguation. This handles
463 struct A { int i; int j; } *q;
464 struct B { struct A a; int k; } *p;
465 disambiguating q->i and p->a.j. */
469 /* Now search for the type1 in the access path of ref2. This
470 would be a common base for doing offset based disambiguation on. */
471 /* Skip the outermost ref - we would have caught that earlier. */
472 refp = &TREE_OPERAND (ref2, 0);
473 while (handled_component_p (*refp)
474 && same_type_for_tbaa (TREE_TYPE (*refp), type1) == 0)
475 refp = &TREE_OPERAND (*refp, 0);
476 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type1);
477 /* If we couldn't compare types we have to bail out. */
480 else if (same_p == 1)
482 HOST_WIDE_INT offadj, sztmp, msztmp;
483 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
485 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
487 /* If we didn't find a common base, try the other way around. */
488 refp = &TREE_OPERAND (ref1, 0);
489 while (handled_component_p (*refp)
490 && same_type_for_tbaa (TREE_TYPE (*refp), type2) == 0)
491 refp = &TREE_OPERAND (*refp, 0);
492 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type2);
493 /* If we couldn't compare types we have to bail out. */
496 else if (same_p == 1)
498 HOST_WIDE_INT offadj, sztmp, msztmp;
499 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
501 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
503 /* If we have two type access paths B1.path1 and B2.path2 they may
504 only alias if either B1 is in B2.path2 or B2 is in B1.path1. */
508 /* Return true if two memory references based on the variables BASE1
509 and BASE2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1[ and
510 [OFFSET2, OFFSET2 + MAX_SIZE2[ may alias. */
513 decl_refs_may_alias_p (tree base1,
514 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
516 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
518 gcc_assert (SSA_VAR_P (base1) && SSA_VAR_P (base2));
520 /* If both references are based on different variables, they cannot alias. */
521 if (!operand_equal_p (base1, base2, 0))
524 /* If both references are based on the same variable, they cannot alias if
525 the accesses do not overlap. */
526 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
529 /* Return true if an indirect reference based on *PTR1 constrained
530 to [OFFSET1, OFFSET1 + MAX_SIZE1[ may alias a variable based on BASE2
531 constrained to [OFFSET2, OFFSET2 + MAX_SIZE2[. *PTR1 and BASE2 have
532 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
533 in which case they are computed on-demand. REF1 and REF2
534 if non-NULL are the complete memory reference trees. */
537 indirect_ref_may_alias_decl_p (tree ref1, tree ptr1,
538 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
539 alias_set_type base1_alias_set,
540 tree ref2, tree base2,
541 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
542 alias_set_type base2_alias_set)
544 /* If only one reference is based on a variable, they cannot alias if
545 the pointer access is beyond the extent of the variable access.
546 (the pointer base cannot validly point to an offset less than zero
548 They also cannot alias if the pointer may not point to the decl. */
550 && !ranges_overlap_p (offset1, max_size1, 0, offset2 + max_size2))
552 if (!ptr_deref_may_alias_decl_p (ptr1, base2))
555 /* Disambiguations that rely on strict aliasing rules follow. */
556 if (!flag_strict_aliasing)
559 /* If the alias set for a pointer access is zero all bets are off. */
560 if (base1_alias_set == -1)
561 base1_alias_set = get_deref_alias_set (ptr1);
562 if (base1_alias_set == 0)
564 if (base2_alias_set == -1)
565 base2_alias_set = get_alias_set (base2);
567 /* If both references are through the same type, they do not alias
568 if the accesses do not overlap. This does extra disambiguation
569 for mixed/pointer accesses but requires strict aliasing. */
570 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
571 TREE_TYPE (base2)) == 1)
572 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
574 /* The only way to access a variable is through a pointer dereference
575 of the same alias set or a subset of it. */
576 if (base1_alias_set != base2_alias_set
577 && !alias_set_subset_of (base1_alias_set, base2_alias_set))
580 /* Do access-path based disambiguation. */
582 && handled_component_p (ref1)
583 && handled_component_p (ref2))
584 return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
586 ref2, TREE_TYPE (base2),
592 /* Return true if two indirect references based on *PTR1
593 and *PTR2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1[ and
594 [OFFSET2, OFFSET2 + MAX_SIZE2[ may alias. *PTR1 and *PTR2 have
595 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
596 in which case they are computed on-demand. REF1 and REF2
597 if non-NULL are the complete memory reference trees. */
600 indirect_refs_may_alias_p (tree ref1, tree ptr1,
601 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
602 alias_set_type base1_alias_set,
603 tree ref2, tree ptr2,
604 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
605 alias_set_type base2_alias_set)
607 /* If both bases are based on pointers they cannot alias if they may not
608 point to the same memory object or if they point to the same object
609 and the accesses do not overlap. */
610 if (operand_equal_p (ptr1, ptr2, 0))
611 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
612 if (!ptr_derefs_may_alias_p (ptr1, ptr2))
615 /* Disambiguations that rely on strict aliasing rules follow. */
616 if (!flag_strict_aliasing)
619 /* If the alias set for a pointer access is zero all bets are off. */
620 if (base1_alias_set == -1)
621 base1_alias_set = get_deref_alias_set (ptr1);
622 if (base1_alias_set == 0)
624 if (base2_alias_set == -1)
625 base2_alias_set = get_deref_alias_set (ptr2);
626 if (base2_alias_set == 0)
629 /* If both references are through the same type, they do not alias
630 if the accesses do not overlap. This does extra disambiguation
631 for mixed/pointer accesses but requires strict aliasing. */
632 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
633 TREE_TYPE (TREE_TYPE (ptr2))) == 1)
634 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
636 /* Do type-based disambiguation. */
637 if (base1_alias_set != base2_alias_set
638 && !alias_sets_conflict_p (base1_alias_set, base2_alias_set))
641 /* Do access-path based disambiguation. */
643 && handled_component_p (ref1)
644 && handled_component_p (ref2))
645 return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
647 ref2, TREE_TYPE (TREE_TYPE (ptr2)),
653 /* Return true, if the two memory references REF1 and REF2 may alias. */
656 refs_may_alias_p_1 (tree ref1, tree ref2)
659 HOST_WIDE_INT offset1 = 0, offset2 = 0;
660 HOST_WIDE_INT size1 = -1, size2 = -1;
661 HOST_WIDE_INT max_size1 = -1, max_size2 = -1;
662 bool var1_p, var2_p, ind1_p, ind2_p;
664 gcc_assert ((SSA_VAR_P (ref1)
665 || handled_component_p (ref1)
666 || INDIRECT_REF_P (ref1)
667 || TREE_CODE (ref1) == TARGET_MEM_REF)
669 || handled_component_p (ref2)
670 || INDIRECT_REF_P (ref2)
671 || TREE_CODE (ref2) == TARGET_MEM_REF));
673 /* Defer to TBAA if possible. */
674 if (flag_strict_aliasing
675 && !alias_sets_conflict_p (get_alias_set (ref1), get_alias_set (ref2)))
678 /* If one reference is a TARGET_MEM_REF weird things are allowed. */
679 if (TREE_CODE (ref1) == TARGET_MEM_REF
680 || TREE_CODE (ref2) == TARGET_MEM_REF)
683 /* Decompose the references into their base objects and the access. */
684 base1 = get_ref_base_and_extent (ref1, &offset1, &size1, &max_size1);
685 base2 = get_ref_base_and_extent (ref2, &offset2, &size2, &max_size2);
687 /* We can end up with registers or constants as bases for example from
688 *D.1663_44 = VIEW_CONVERT_EXPR<struct DB_LSN>(__tmp$B0F64_59);
689 which is seen as a struct copy. */
690 if (TREE_CODE (base1) == SSA_NAME
691 || TREE_CODE (base2) == SSA_NAME
692 || is_gimple_min_invariant (base1)
693 || is_gimple_min_invariant (base2))
696 var1_p = SSA_VAR_P (base1);
697 var2_p = SSA_VAR_P (base2);
698 ind1_p = INDIRECT_REF_P (base1);
699 ind2_p = INDIRECT_REF_P (base2);
700 if (var1_p && var2_p)
701 return decl_refs_may_alias_p (base1, offset1, max_size1,
702 base2, offset2, max_size2);
703 else if (var1_p && ind2_p)
704 return indirect_ref_may_alias_decl_p (ref2, TREE_OPERAND (base2, 0),
705 offset2, max_size2, -1,
707 offset1, max_size1, -1);
708 else if (ind1_p && var2_p)
709 return indirect_ref_may_alias_decl_p (ref1, TREE_OPERAND (base1, 0),
710 offset1, max_size1, -1,
712 offset2, max_size2, -1);
713 else if (ind1_p && ind2_p)
714 return indirect_refs_may_alias_p (ref1, TREE_OPERAND (base1, 0),
715 offset1, max_size1, -1,
716 ref2, TREE_OPERAND (base2, 0),
717 offset2, max_size2, -1);
723 refs_may_alias_p (tree ref1, tree ref2)
725 bool res = refs_may_alias_p_1 (ref1, ref2);
727 ++alias_stats.refs_may_alias_p_may_alias;
729 ++alias_stats.refs_may_alias_p_no_alias;
734 /* If the call CALL may use the memory reference REF return true,
735 otherwise return false. */
738 ref_maybe_used_by_call_p_1 (gimple call, tree ref)
742 int flags = gimple_call_flags (call);
744 /* Const functions without a static chain do not implicitly use memory. */
745 if (!gimple_call_chain (call)
746 && (flags & (ECF_CONST|ECF_NOVOPS)))
749 /* If the reference is not based on a decl give up.
750 ??? Handle indirect references by intersecting the call-used
751 solution with that of the pointer. */
752 base = get_base_address (ref);
757 /* If the reference is based on a decl that is not aliased the call
758 cannot possibly use it. */
760 && !may_be_aliased (base)
761 /* But local statics can be used through recursion! */
762 && (!is_global_var (base)
763 /* But not via builtins.
764 ??? We just assume that this is true if we are not a
765 builtin function ourself. */
766 || (!DECL_BUILT_IN (cfun->decl)
767 && (fndecl = gimple_call_fndecl (call))
768 && DECL_BUILT_IN (fndecl))))
771 /* Check if base is a global static variable that is not read
773 if (TREE_CODE (base) == VAR_DECL
774 && TREE_STATIC (base)
775 && !TREE_PUBLIC (base))
777 tree callee = gimple_call_fndecl (call);
780 if (callee != NULL_TREE
782 = ipa_reference_get_not_read_global (cgraph_node (callee)))
783 && bitmap_bit_p (not_read, DECL_UID (base)))
787 /* If the base variable is call-used or call-clobbered then
789 if (flags & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
791 if (is_call_used (base))
796 if (is_call_clobbered (base))
800 /* Inspect call arguments for passed-by-value aliases. */
802 for (i = 0; i < gimple_call_num_args (call); ++i)
804 tree op = gimple_call_arg (call, i);
806 if (TREE_CODE (op) == EXC_PTR_EXPR
807 || TREE_CODE (op) == FILTER_EXPR)
810 if (TREE_CODE (op) == WITH_SIZE_EXPR)
811 op = TREE_OPERAND (op, 0);
813 if (TREE_CODE (op) != SSA_NAME
814 && !is_gimple_min_invariant (op)
815 && refs_may_alias_p (op, ref))
823 ref_maybe_used_by_call_p (gimple call, tree ref)
825 bool res = ref_maybe_used_by_call_p_1 (call, ref);
827 ++alias_stats.ref_maybe_used_by_call_p_may_alias;
829 ++alias_stats.ref_maybe_used_by_call_p_no_alias;
834 /* If the statement STMT may use the memory reference REF return
835 true, otherwise return false. */
838 ref_maybe_used_by_stmt_p (gimple stmt, tree ref)
840 if (is_gimple_assign (stmt))
844 /* All memory assign statements are single. */
845 if (!gimple_assign_single_p (stmt))
848 rhs = gimple_assign_rhs1 (stmt);
849 if (is_gimple_reg (rhs)
850 || is_gimple_min_invariant (rhs)
851 || gimple_assign_rhs_code (stmt) == CONSTRUCTOR)
854 return refs_may_alias_p (rhs, ref);
856 else if (is_gimple_call (stmt))
857 return ref_maybe_used_by_call_p (stmt, ref);
862 /* If the call in statement CALL may clobber the memory reference REF
863 return true, otherwise return false. */
866 call_may_clobber_ref_p_1 (gimple call, tree ref)
870 /* If the call is pure or const it cannot clobber anything. */
871 if (gimple_call_flags (call)
872 & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
875 base = get_base_address (ref);
879 if (TREE_CODE (base) == SSA_NAME
880 || CONSTANT_CLASS_P (base))
883 /* If the reference is based on a decl that is not aliased the call
884 cannot possibly clobber it. */
886 && !may_be_aliased (base)
887 /* But local non-readonly statics can be modified through recursion! */
888 && (TREE_READONLY (base)
889 || !is_global_var (base)
890 /* But not via builtins.
891 ??? We just assume that this is true if we are not a
892 builtin function ourself. */
893 || (!DECL_BUILT_IN (cfun->decl)
894 && (fndecl = gimple_call_fndecl (call))
895 && DECL_BUILT_IN (fndecl))))
898 /* Check if base is a global static variable that is not written
900 if (TREE_CODE (base) == VAR_DECL
901 && TREE_STATIC (base)
902 && !TREE_PUBLIC (base))
904 tree callee = gimple_call_fndecl (call);
907 if (callee != NULL_TREE
909 = ipa_reference_get_not_written_global (cgraph_node (callee)))
910 && bitmap_bit_p (not_written, DECL_UID (base)))
915 return is_call_clobbered (base);
921 call_may_clobber_ref_p (gimple call, tree ref)
923 bool res = call_may_clobber_ref_p_1 (call, ref);
925 ++alias_stats.call_may_clobber_ref_p_may_alias;
927 ++alias_stats.call_may_clobber_ref_p_no_alias;
932 /* If the statement STMT may clobber the memory reference REF return true,
933 otherwise return false. */
936 stmt_may_clobber_ref_p (gimple stmt, tree ref)
938 if (is_gimple_call (stmt))
940 tree lhs = gimple_call_lhs (stmt);
942 && !is_gimple_reg (lhs)
943 && refs_may_alias_p (ref, lhs))
946 return call_may_clobber_ref_p (stmt, ref);
948 else if (is_gimple_assign (stmt))
949 return refs_may_alias_p (ref, gimple_assign_lhs (stmt));
950 else if (gimple_code (stmt) == GIMPLE_ASM)
956 static tree get_continuation_for_phi (gimple, tree, bitmap *);
958 /* Walk the virtual use-def chain of VUSE until hitting the virtual operand
959 TARGET or a statement clobbering the memory reference REF in which
960 case false is returned. The walk starts with VUSE, one argument of PHI. */
963 maybe_skip_until (gimple phi, tree target, tree ref, tree vuse, bitmap *visited)
966 *visited = BITMAP_ALLOC (NULL);
968 bitmap_set_bit (*visited, SSA_NAME_VERSION (PHI_RESULT (phi)));
970 /* Walk until we hit the target. */
971 while (vuse != target)
973 gimple def_stmt = SSA_NAME_DEF_STMT (vuse);
974 /* Recurse for PHI nodes. */
975 if (gimple_code (def_stmt) == GIMPLE_PHI)
977 /* An already visited PHI node ends the walk successfully. */
978 if (bitmap_bit_p (*visited, SSA_NAME_VERSION (PHI_RESULT (def_stmt))))
980 vuse = get_continuation_for_phi (def_stmt, ref, visited);
985 /* A clobbering statement or the end of the IL ends it failing. */
986 else if (gimple_nop_p (def_stmt)
987 || stmt_may_clobber_ref_p (def_stmt, ref))
989 vuse = gimple_vuse (def_stmt);
994 /* Starting from a PHI node for the virtual operand of the memory reference
995 REF find a continuation virtual operand that allows to continue walking
996 statements dominating PHI skipping only statements that cannot possibly
997 clobber REF. Returns NULL_TREE if no suitable virtual operand can
1001 get_continuation_for_phi (gimple phi, tree ref, bitmap *visited)
1003 unsigned nargs = gimple_phi_num_args (phi);
1005 /* Through a single-argument PHI we can simply look through. */
1007 return PHI_ARG_DEF (phi, 0);
1009 /* For two arguments try to skip non-aliasing code until we hit
1010 the phi argument definition that dominates the other one. */
1013 tree arg0 = PHI_ARG_DEF (phi, 0);
1014 tree arg1 = PHI_ARG_DEF (phi, 1);
1015 gimple def0 = SSA_NAME_DEF_STMT (arg0);
1016 gimple def1 = SSA_NAME_DEF_STMT (arg1);
1020 else if (gimple_nop_p (def0)
1021 || (!gimple_nop_p (def1)
1022 && dominated_by_p (CDI_DOMINATORS,
1023 gimple_bb (def1), gimple_bb (def0))))
1025 if (maybe_skip_until (phi, arg0, ref, arg1, visited))
1028 else if (gimple_nop_p (def1)
1029 || dominated_by_p (CDI_DOMINATORS,
1030 gimple_bb (def0), gimple_bb (def1)))
1032 if (maybe_skip_until (phi, arg1, ref, arg0, visited))
1040 /* Based on the memory reference REF and its virtual use VUSE call
1041 WALKER for each virtual use that is equivalent to VUSE, including VUSE
1042 itself. That is, for each virtual use for which its defining statement
1043 does not clobber REF.
1045 WALKER is called with REF, the current virtual use and DATA. If
1046 WALKER returns non-NULL the walk stops and its result is returned.
1047 At the end of a non-successful walk NULL is returned.
1049 TODO: Cache the vector of equivalent vuses per ref, vuse pair. */
1052 walk_non_aliased_vuses (tree ref, tree vuse,
1053 void *(*walker)(tree, tree, void *), void *data)
1055 bitmap visited = NULL;
1058 timevar_push (TV_ALIAS_STMT_WALK);
1064 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
1065 res = (*walker) (ref, vuse, data);
1069 def_stmt = SSA_NAME_DEF_STMT (vuse);
1070 if (gimple_nop_p (def_stmt))
1072 else if (gimple_code (def_stmt) == GIMPLE_PHI)
1073 vuse = get_continuation_for_phi (def_stmt, ref, &visited);
1076 if (stmt_may_clobber_ref_p (def_stmt, ref))
1078 vuse = gimple_vuse (def_stmt);
1084 BITMAP_FREE (visited);
1086 timevar_pop (TV_ALIAS_STMT_WALK);
1092 /* Based on the memory reference REF call WALKER for each vdef which
1093 defining statement may clobber REF, starting with VDEF. If REF
1094 is NULL_TREE, each defining statement is visited.
1096 WALKER is called with REF, the current vdef and DATA. If WALKER
1097 returns true the walk is stopped, otherwise it continues.
1099 At PHI nodes walk_aliased_vdefs forks into one walk for reach
1100 PHI argument (but only one walk continues on merge points), the
1101 return value is true if any of the walks was successful.
1103 The function returns the number of statements walked. */
1106 walk_aliased_vdefs_1 (tree ref, tree vdef,
1107 bool (*walker)(tree, tree, void *), void *data,
1108 bitmap *visited, unsigned int cnt)
1112 gimple def_stmt = SSA_NAME_DEF_STMT (vdef);
1115 && !bitmap_set_bit (*visited, SSA_NAME_VERSION (vdef)))
1118 if (gimple_nop_p (def_stmt))
1120 else if (gimple_code (def_stmt) == GIMPLE_PHI)
1124 *visited = BITMAP_ALLOC (NULL);
1125 for (i = 0; i < gimple_phi_num_args (def_stmt); ++i)
1126 cnt += walk_aliased_vdefs_1 (ref, gimple_phi_arg_def (def_stmt, i),
1127 walker, data, visited, 0);
1131 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
1134 || stmt_may_clobber_ref_p (def_stmt, ref))
1135 && (*walker) (ref, vdef, data))
1138 vdef = gimple_vuse (def_stmt);
1144 walk_aliased_vdefs (tree ref, tree vdef,
1145 bool (*walker)(tree, tree, void *), void *data,
1148 bitmap local_visited = NULL;
1151 timevar_push (TV_ALIAS_STMT_WALK);
1153 ret = walk_aliased_vdefs_1 (ref, vdef, walker, data,
1154 visited ? visited : &local_visited, 0);
1156 BITMAP_FREE (local_visited);
1158 timevar_pop (TV_ALIAS_STMT_WALK);