1 /* Miscellaneous SSA utility functions.
2 Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
4 This file is part of GCC.
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)
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.
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. */
23 #include "coretypes.h"
30 #include "langhooks.h"
31 #include "hard-reg-set.h"
32 #include "basic-block.h"
37 #include "diagnostic.h"
39 #include "pointer-set.h"
40 #include "tree-flow.h"
41 #include "tree-gimple.h"
42 #include "tree-inline.h"
46 #include "tree-dump.h"
47 #include "tree-pass.h"
49 /* Remove the corresponding arguments from the PHI nodes in E's
50 destination block and redirect it to DEST. Return redirected edge.
51 The list of removed arguments is stored in PENDING_STMT (e). */
54 ssa_redirect_edge (edge e, basic_block dest)
57 tree list = NULL, *last = &list;
60 /* Remove the appropriate PHI arguments in E's destination block. */
61 for (phi = phi_nodes (e->dest); phi; phi = next)
63 next = PHI_CHAIN (phi);
65 if (PHI_ARG_DEF (phi, e->dest_idx) == NULL_TREE)
68 src = PHI_ARG_DEF (phi, e->dest_idx);
69 dst = PHI_RESULT (phi);
70 node = build_tree_list (dst, src);
72 last = &TREE_CHAIN (node);
75 e = redirect_edge_succ_nodup (e, dest);
76 PENDING_STMT (e) = list;
81 /* Add PHI arguments queued in PENDINT_STMT list on edge E to edge
85 flush_pending_stmts (edge e)
89 if (!PENDING_STMT (e))
92 for (phi = phi_nodes (e->dest), arg = PENDING_STMT (e);
94 phi = PHI_CHAIN (phi), arg = TREE_CHAIN (arg))
96 tree def = TREE_VALUE (arg);
97 add_phi_arg (phi, def, e);
100 PENDING_STMT (e) = NULL;
103 /* Return true if SSA_NAME is malformed and mark it visited.
105 IS_VIRTUAL is true if this SSA_NAME was found inside a virtual
109 verify_ssa_name (tree ssa_name, bool is_virtual)
111 if (TREE_CODE (ssa_name) != SSA_NAME)
113 error ("Expected an SSA_NAME object");
117 if (TREE_TYPE (ssa_name) != TREE_TYPE (SSA_NAME_VAR (ssa_name)))
119 error ("Type mismatch between an SSA_NAME and its symbol.");
123 if (SSA_NAME_IN_FREE_LIST (ssa_name))
125 error ("Found an SSA_NAME that had been released into the free pool");
129 if (is_virtual && is_gimple_reg (ssa_name))
131 error ("Found a virtual definition for a GIMPLE register");
135 if (!is_virtual && !is_gimple_reg (ssa_name))
137 error ("Found a real definition for a non-register");
145 /* Return true if the definition of SSA_NAME at block BB is malformed.
147 STMT is the statement where SSA_NAME is created.
149 DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME
150 version numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set,
151 it means that the block in that array slot contains the
152 definition of SSA_NAME.
154 IS_VIRTUAL is true if SSA_NAME is created by a V_MAY_DEF or a
158 verify_def (basic_block bb, basic_block *definition_block, tree ssa_name,
159 tree stmt, bool is_virtual)
161 if (verify_ssa_name (ssa_name, is_virtual))
164 if (definition_block[SSA_NAME_VERSION (ssa_name)])
166 error ("SSA_NAME created in two different blocks %i and %i",
167 definition_block[SSA_NAME_VERSION (ssa_name)]->index, bb->index);
171 definition_block[SSA_NAME_VERSION (ssa_name)] = bb;
173 if (SSA_NAME_DEF_STMT (ssa_name) != stmt)
175 error ("SSA_NAME_DEF_STMT is wrong");
176 fprintf (stderr, "Expected definition statement:\n");
177 print_generic_stmt (stderr, SSA_NAME_DEF_STMT (ssa_name), TDF_VOPS);
178 fprintf (stderr, "\nActual definition statement:\n");
179 print_generic_stmt (stderr, stmt, TDF_VOPS);
186 fprintf (stderr, "while verifying SSA_NAME ");
187 print_generic_expr (stderr, ssa_name, 0);
188 fprintf (stderr, " in statement\n");
189 print_generic_stmt (stderr, stmt, TDF_VOPS);
195 /* Return true if the use of SSA_NAME at statement STMT in block BB is
198 DEF_BB is the block where SSA_NAME was found to be created.
200 IDOM contains immediate dominator information for the flowgraph.
202 CHECK_ABNORMAL is true if the caller wants to check whether this use
203 is flowing through an abnormal edge (only used when checking PHI
206 IS_VIRTUAL is true if SSA_NAME is created by a V_MAY_DEF or a
209 If NAMES_DEFINED_IN_BB is not NULL, it contains a bitmap of ssa names
210 that are defined before STMT in basic block BB. */
213 verify_use (basic_block bb, basic_block def_bb, tree ssa_name,
214 tree stmt, bool check_abnormal, bool is_virtual,
215 bitmap names_defined_in_bb)
219 err = verify_ssa_name (ssa_name, is_virtual);
220 TREE_VISITED (ssa_name) = 1;
222 if (IS_EMPTY_STMT (SSA_NAME_DEF_STMT (ssa_name))
223 && var_ann (SSA_NAME_VAR (ssa_name))->default_def == ssa_name)
224 ; /* Default definitions have empty statements. Nothing to do. */
227 error ("Missing definition");
230 else if (bb != def_bb
231 && !dominated_by_p (CDI_DOMINATORS, bb, def_bb))
233 error ("Definition in block %i does not dominate use in block %i",
234 def_bb->index, bb->index);
237 else if (bb == def_bb
238 && names_defined_in_bb != NULL
239 && !bitmap_bit_p (names_defined_in_bb, SSA_NAME_VERSION (ssa_name)))
241 error ("Definition in block %i follows the use", def_bb->index);
246 && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (ssa_name))
248 error ("SSA_NAME_OCCURS_IN_ABNORMAL_PHI should be set");
254 fprintf (stderr, "for SSA_NAME: ");
255 print_generic_expr (stderr, ssa_name, TDF_VOPS);
256 fprintf (stderr, "in statement:\n");
257 print_generic_stmt (stderr, stmt, TDF_VOPS);
264 /* Return true if any of the arguments for PHI node PHI at block BB is
267 DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME version
268 numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set, it means that the
269 block in that array slot contains the definition of SSA_NAME. */
272 verify_phi_args (tree phi, basic_block bb, basic_block *definition_block)
276 unsigned i, phi_num_args = PHI_NUM_ARGS (phi);
278 if (EDGE_COUNT (bb->preds) != phi_num_args)
280 error ("Incoming edge count does not match number of PHI arguments\n");
285 for (i = 0; i < phi_num_args; i++)
287 tree op = PHI_ARG_DEF (phi, i);
289 e = EDGE_PRED (bb, i);
293 error ("PHI argument is missing for edge %d->%d\n",
300 if (TREE_CODE (op) != SSA_NAME && !is_gimple_min_invariant (op))
302 error ("PHI argument is not SSA_NAME, or invariant");
306 if (TREE_CODE (op) == SSA_NAME)
307 err = verify_use (e->src, definition_block[SSA_NAME_VERSION (op)], op,
308 phi, e->flags & EDGE_ABNORMAL,
309 !is_gimple_reg (PHI_RESULT (phi)),
314 error ("Wrong edge %d->%d for PHI argument\n",
315 e->src->index, e->dest->index, bb->index);
321 fprintf (stderr, "PHI argument\n");
322 print_generic_stmt (stderr, op, TDF_VOPS);
330 fprintf (stderr, "for PHI node\n");
331 print_generic_stmt (stderr, phi, TDF_VOPS);
340 verify_flow_insensitive_alias_info (void)
344 bitmap visited = BITMAP_ALLOC (NULL);
346 for (i = 0; i < num_referenced_vars; i++)
350 varray_type may_aliases;
352 var = referenced_var (i);
354 may_aliases = ann->may_aliases;
356 for (j = 0; may_aliases && j < VARRAY_ACTIVE_SIZE (may_aliases); j++)
358 tree alias = VARRAY_TREE (may_aliases, j);
360 bitmap_set_bit (visited, var_ann (alias)->uid);
362 if (!may_be_aliased (alias))
364 error ("Non-addressable variable inside an alias set.");
365 debug_variable (alias);
371 for (i = 0; i < num_referenced_vars; i++)
375 var = referenced_var (i);
378 if (ann->mem_tag_kind == NOT_A_TAG
380 && !bitmap_bit_p (visited, ann->uid))
382 error ("Addressable variable that is an alias tag but is not in any alias set.");
387 BITMAP_FREE (visited);
391 debug_variable (var);
392 internal_error ("verify_flow_insensitive_alias_info failed.");
397 verify_flow_sensitive_alias_info (void)
402 for (i = 1; i < num_ssa_names; i++)
406 struct ptr_info_def *pi;
413 /* We only care for pointers that are actually referenced in the
415 if (!POINTER_TYPE_P (TREE_TYPE (ptr)) || !TREE_VISITED (ptr))
418 /* RESULT_DECL is special. If it's a GIMPLE register, then it
419 is only written-to only once in the return statement.
420 Otherwise, aggregate RESULT_DECLs may be written-to more than
421 once in virtual operands. */
422 var = SSA_NAME_VAR (ptr);
423 if (TREE_CODE (var) == RESULT_DECL
424 && is_gimple_reg (ptr))
427 pi = SSA_NAME_PTR_INFO (ptr);
432 if (pi->is_dereferenced && !pi->name_mem_tag && !ann->type_mem_tag)
434 error ("Dereferenced pointers should have a name or a type tag");
440 && (pi->pt_vars == NULL || bitmap_empty_p (pi->pt_vars)))
442 error ("Pointers with a memory tag, should have points-to sets or point to malloc");
446 if (pi->value_escapes_p
448 && !is_call_clobbered (pi->name_mem_tag))
450 error ("Pointer escapes but its name tag is not call-clobbered.");
458 debug_variable (ptr);
459 internal_error ("verify_flow_sensitive_alias_info failed.");
462 DEF_VEC_MALLOC_P (bitmap);
464 /* Verify that all name tags have different points to sets.
465 This algorithm takes advantage of the fact that every variable with the
466 same name tag must have the same points-to set.
467 So we check a single variable for each name tag, and verify that its
468 points-to set is different from every other points-to set for other name
471 Additionally, given a pointer P_i with name tag NMT and type tag
472 TMT, this function verified the alias set of TMT is a superset of
473 the alias set of NMT. */
476 verify_name_tags (void)
480 bitmap first, second;
481 VEC (tree) *name_tag_reps = NULL;
482 VEC (bitmap) *pt_vars_for_reps = NULL;
483 bitmap type_aliases = BITMAP_ALLOC (NULL);
485 /* First we compute the name tag representatives and their points-to sets. */
486 for (i = 0; i < num_ssa_names; i++)
488 struct ptr_info_def *pi;
489 tree tmt, ptr = ssa_name (i);
491 if (ptr == NULL_TREE)
494 pi = SSA_NAME_PTR_INFO (ptr);
496 if (!TREE_VISITED (ptr)
497 || !POINTER_TYPE_P (TREE_TYPE (ptr))
500 || TREE_VISITED (pi->name_mem_tag))
503 TREE_VISITED (pi->name_mem_tag) = 1;
505 if (pi->pt_vars == NULL)
508 VEC_safe_push (tree, name_tag_reps, ptr);
509 VEC_safe_push (bitmap, pt_vars_for_reps, pi->pt_vars);
511 /* Verify that alias set of PTR's type tag is a superset of the
512 alias set of PTR's name tag. */
513 tmt = var_ann (SSA_NAME_VAR (ptr))->type_mem_tag;
517 varray_type aliases = var_ann (tmt)->may_aliases;
518 bitmap_clear (type_aliases);
519 for (i = 0; aliases && i < VARRAY_ACTIVE_SIZE (aliases); i++)
521 tree alias = VARRAY_TREE (aliases, i);
522 bitmap_set_bit (type_aliases, var_ann (alias)->uid);
525 /* When grouping, we may have added PTR's type tag into the
526 alias set of PTR's name tag. To prevent a false
527 positive, pretend that TMT is in its own alias set. */
528 bitmap_set_bit (type_aliases, var_ann (tmt)->uid);
530 if (bitmap_equal_p (type_aliases, pi->pt_vars))
533 if (!bitmap_intersect_compl_p (type_aliases, pi->pt_vars))
535 error ("Alias set of a pointer's type tag should be a superset of the corresponding name tag");
536 debug_variable (tmt);
537 debug_variable (pi->name_mem_tag);
543 /* Now compare all the representative bitmaps with all other representative
544 bitmaps, to verify that they are all different. */
545 for (i = 0; VEC_iterate (bitmap, pt_vars_for_reps, i, first); i++)
547 for (j = i + 1; VEC_iterate (bitmap, pt_vars_for_reps, j, second); j++)
549 if (bitmap_equal_p (first, second))
551 error ("Two different pointers with identical points-to sets but different name tags");
552 debug_variable (VEC_index (tree, name_tag_reps, j));
558 /* Lastly, clear out the visited flags. */
559 for (i = 0; i < num_ssa_names; i++)
563 tree ptr = ssa_name (i);
564 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
565 if (!TREE_VISITED (ptr)
566 || !POINTER_TYPE_P (TREE_TYPE (ptr))
568 || !pi->name_mem_tag)
570 TREE_VISITED (pi->name_mem_tag) = 0;
574 VEC_free (bitmap, pt_vars_for_reps);
575 BITMAP_FREE (type_aliases);
579 debug_variable (VEC_index (tree, name_tag_reps, i));
580 internal_error ("verify_name_tags failed");
584 /* Verify the consistency of aliasing information. */
587 verify_alias_info (void)
589 verify_flow_sensitive_alias_info ();
591 verify_flow_insensitive_alias_info ();
595 /* Verify common invariants in the SSA web.
596 TODO: verify the variable annotations. */
603 basic_block *definition_block = xcalloc (num_ssa_names, sizeof (basic_block));
606 enum dom_state orig_dom_state = dom_computed[CDI_DOMINATORS];
607 bitmap names_defined_in_bb = BITMAP_ALLOC (NULL);
609 timevar_push (TV_TREE_SSA_VERIFY);
611 /* Keep track of SSA names present in the IL. */
612 for (i = 1; i < num_ssa_names; i++)
614 tree name = ssa_name (i);
618 TREE_VISITED (name) = 0;
620 stmt = SSA_NAME_DEF_STMT (name);
621 if (!IS_EMPTY_STMT (stmt))
623 basic_block bb = bb_for_stmt (stmt);
624 verify_def (bb, definition_block,
625 name, stmt, !is_gimple_reg (name));
631 calculate_dominance_info (CDI_DOMINATORS);
633 /* Now verify all the uses and make sure they agree with the definitions
634 found in the previous pass. */
640 block_stmt_iterator bsi;
642 /* Make sure that all edges have a clear 'aux' field. */
643 FOR_EACH_EDGE (e, ei, bb->preds)
647 error ("AUX pointer initialized for edge %d->%d\n", e->src->index,
653 /* Verify the arguments for every PHI node in the block. */
654 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
656 if (verify_phi_args (phi, bb, definition_block))
658 bitmap_set_bit (names_defined_in_bb,
659 SSA_NAME_VERSION (PHI_RESULT (phi)));
662 /* Now verify all the uses and vuses in every statement of the block. */
663 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
665 tree stmt = bsi_stmt (bsi);
667 get_stmt_operands (stmt);
669 if (stmt_ann (stmt)->makes_aliased_stores
670 && NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0)
672 error ("Statement makes aliased stores, but has no V_MAY_DEFS");
673 print_generic_stmt (stderr, stmt, TDF_VOPS);
677 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_ALL_USES | SSA_OP_ALL_KILLS)
679 if (verify_use (bb, definition_block[SSA_NAME_VERSION (op)],
680 op, stmt, false, !is_gimple_reg (op),
681 names_defined_in_bb))
685 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_ALL_DEFS)
687 bitmap_set_bit (names_defined_in_bb, SSA_NAME_VERSION (op));
691 bitmap_clear (names_defined_in_bb);
694 /* Finally, verify alias information. */
695 verify_alias_info ();
697 free (definition_block);
698 /* Restore the dominance information to its prior known state, so
699 that we do not perturb the compiler's subsequent behavior. */
700 if (orig_dom_state == DOM_NONE)
701 free_dominance_info (CDI_DOMINATORS);
703 dom_computed[CDI_DOMINATORS] = orig_dom_state;
705 BITMAP_FREE (names_defined_in_bb);
706 timevar_pop (TV_TREE_SSA_VERIFY);
710 internal_error ("verify_ssa failed.");
714 /* Initialize global DFA and SSA structures. */
719 VARRAY_TREE_INIT (referenced_vars, 20, "referenced_vars");
720 call_clobbered_vars = BITMAP_ALLOC (NULL);
721 addressable_vars = BITMAP_ALLOC (NULL);
722 init_ssa_operands ();
725 global_var = NULL_TREE;
729 /* Deallocate memory associated with SSA data structures for FNDECL. */
732 delete_tree_ssa (void)
736 block_stmt_iterator bsi;
738 /* Remove annotations from every tree in the function. */
740 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
742 tree stmt = bsi_stmt (bsi);
744 ggc_free (stmt->common.ann);
745 stmt->common.ann = NULL;
748 /* Remove annotations from every referenced variable. */
751 for (i = 0; i < num_referenced_vars; i++)
753 tree var = referenced_var (i);
754 ggc_free (var->common.ann);
755 var->common.ann = NULL;
757 referenced_vars = NULL;
762 fini_ssa_operands ();
764 global_var = NULL_TREE;
765 BITMAP_FREE (call_clobbered_vars);
766 call_clobbered_vars = NULL;
767 BITMAP_FREE (addressable_vars);
768 addressable_vars = NULL;
769 modified_noreturn_calls = NULL;
773 /* Return true if EXPR is a useless type conversion, otherwise return
777 tree_ssa_useless_type_conversion_1 (tree outer_type, tree inner_type)
779 /* If the inner and outer types are effectively the same, then
780 strip the type conversion and enter the equivalence into
782 if (inner_type == outer_type
783 || (lang_hooks.types_compatible_p (inner_type, outer_type)))
786 /* If both types are pointers and the outer type is a (void *), then
787 the conversion is not necessary. The opposite is not true since
788 that conversion would result in a loss of information if the
789 equivalence was used. Consider an indirect function call where
790 we need to know the exact type of the function to correctly
791 implement the ABI. */
792 else if (POINTER_TYPE_P (inner_type)
793 && POINTER_TYPE_P (outer_type)
794 && TYPE_MODE (inner_type) == TYPE_MODE (outer_type)
795 && TYPE_REF_CAN_ALIAS_ALL (inner_type)
796 == TYPE_REF_CAN_ALIAS_ALL (outer_type)
797 && TREE_CODE (TREE_TYPE (outer_type)) == VOID_TYPE)
800 /* Pointers and references are equivalent once we get to GENERIC,
801 so strip conversions that just switch between them. */
802 else if (POINTER_TYPE_P (inner_type)
803 && POINTER_TYPE_P (outer_type)
804 && TYPE_MODE (inner_type) == TYPE_MODE (outer_type)
805 && TYPE_REF_CAN_ALIAS_ALL (inner_type)
806 == TYPE_REF_CAN_ALIAS_ALL (outer_type)
807 && lang_hooks.types_compatible_p (TREE_TYPE (inner_type),
808 TREE_TYPE (outer_type)))
811 /* If both the inner and outer types are integral types, then the
812 conversion is not necessary if they have the same mode and
813 signedness and precision, and both or neither are boolean. Some
814 code assumes an invariant that boolean types stay boolean and do
815 not become 1-bit bit-field types. Note that types with precision
816 not using all bits of the mode (such as bit-field types in C)
817 mean that testing of precision is necessary. */
818 else if (INTEGRAL_TYPE_P (inner_type)
819 && INTEGRAL_TYPE_P (outer_type)
820 && TYPE_MODE (inner_type) == TYPE_MODE (outer_type)
821 && TYPE_UNSIGNED (inner_type) == TYPE_UNSIGNED (outer_type)
822 && TYPE_PRECISION (inner_type) == TYPE_PRECISION (outer_type))
824 bool first_boolean = (TREE_CODE (inner_type) == BOOLEAN_TYPE);
825 bool second_boolean = (TREE_CODE (outer_type) == BOOLEAN_TYPE);
826 if (first_boolean == second_boolean)
830 /* Recurse for complex types. */
831 else if (TREE_CODE (inner_type) == COMPLEX_TYPE
832 && TREE_CODE (outer_type) == COMPLEX_TYPE
833 && tree_ssa_useless_type_conversion_1 (TREE_TYPE (outer_type),
834 TREE_TYPE (inner_type)))
840 /* Return true if EXPR is a useless type conversion, otherwise return
844 tree_ssa_useless_type_conversion (tree expr)
846 /* If we have an assignment that merely uses a NOP_EXPR to change
847 the top of the RHS to the type of the LHS and the type conversion
848 is "safe", then strip away the type conversion so that we can
849 enter LHS = RHS into the const_and_copies table. */
850 if (TREE_CODE (expr) == NOP_EXPR || TREE_CODE (expr) == CONVERT_EXPR
851 || TREE_CODE (expr) == VIEW_CONVERT_EXPR
852 || TREE_CODE (expr) == NON_LVALUE_EXPR)
853 return tree_ssa_useless_type_conversion_1 (TREE_TYPE (expr),
854 TREE_TYPE (TREE_OPERAND (expr,
861 /* Returns true if statement STMT may read memory. */
864 stmt_references_memory_p (tree stmt)
868 get_stmt_operands (stmt);
869 ann = stmt_ann (stmt);
871 if (ann->has_volatile_ops)
874 return (NUM_VUSES (VUSE_OPS (ann)) > 0
875 || NUM_V_MAY_DEFS (V_MAY_DEF_OPS (ann)) > 0
876 || NUM_V_MUST_DEFS (V_MUST_DEF_OPS (ann)) > 0);
879 /* Internal helper for walk_use_def_chains. VAR, FN and DATA are as
880 described in walk_use_def_chains.
882 VISITED is a pointer set used to mark visited SSA_NAMEs to avoid
883 infinite loops. We used to have a bitmap for this to just mark
884 SSA versions we had visited. But non-sparse bitmaps are way too
885 expensive, while sparse bitmaps may cause quadratic behavior.
887 IS_DFS is true if the caller wants to perform a depth-first search
888 when visiting PHI nodes. A DFS will visit each PHI argument and
889 call FN after each one. Otherwise, all the arguments are
890 visited first and then FN is called with each of the visited
891 arguments in a separate pass. */
894 walk_use_def_chains_1 (tree var, walk_use_def_chains_fn fn, void *data,
895 struct pointer_set_t *visited, bool is_dfs)
899 if (pointer_set_insert (visited, var))
902 def_stmt = SSA_NAME_DEF_STMT (var);
904 if (TREE_CODE (def_stmt) != PHI_NODE)
906 /* If we reached the end of the use-def chain, call FN. */
907 return fn (var, def_stmt, data);
913 /* When doing a breadth-first search, call FN before following the
914 use-def links for each argument. */
916 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
917 if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data))
920 /* Follow use-def links out of each PHI argument. */
921 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
923 tree arg = PHI_ARG_DEF (def_stmt, i);
924 if (TREE_CODE (arg) == SSA_NAME
925 && walk_use_def_chains_1 (arg, fn, data, visited, is_dfs))
929 /* When doing a depth-first search, call FN after following the
930 use-def links for each argument. */
932 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
933 if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data))
942 /* Walk use-def chains starting at the SSA variable VAR. Call
943 function FN at each reaching definition found. FN takes three
944 arguments: VAR, its defining statement (DEF_STMT) and a generic
945 pointer to whatever state information that FN may want to maintain
946 (DATA). FN is able to stop the walk by returning true, otherwise
947 in order to continue the walk, FN should return false.
949 Note, that if DEF_STMT is a PHI node, the semantics are slightly
950 different. The first argument to FN is no longer the original
951 variable VAR, but the PHI argument currently being examined. If FN
952 wants to get at VAR, it should call PHI_RESULT (PHI).
954 If IS_DFS is true, this function will:
956 1- walk the use-def chains for all the PHI arguments, and,
957 2- call (*FN) (ARG, PHI, DATA) on all the PHI arguments.
959 If IS_DFS is false, the two steps above are done in reverse order
960 (i.e., a breadth-first search). */
964 walk_use_def_chains (tree var, walk_use_def_chains_fn fn, void *data,
969 gcc_assert (TREE_CODE (var) == SSA_NAME);
971 def_stmt = SSA_NAME_DEF_STMT (var);
973 /* We only need to recurse if the reaching definition comes from a PHI
975 if (TREE_CODE (def_stmt) != PHI_NODE)
976 (*fn) (var, def_stmt, data);
979 struct pointer_set_t *visited = pointer_set_create ();
980 walk_use_def_chains_1 (var, fn, data, visited, is_dfs);
981 pointer_set_destroy (visited);
986 /* Replaces VAR with REPL in memory reference expression *X in
990 propagate_into_addr (tree stmt, tree var, tree *x, tree repl)
992 tree new_var, ass_stmt, addr_var;
994 block_stmt_iterator bsi;
996 /* There is nothing special to handle in the other cases. */
997 if (TREE_CODE (repl) != ADDR_EXPR)
999 addr_var = TREE_OPERAND (repl, 0);
1001 while (handled_component_p (*x)
1002 || TREE_CODE (*x) == REALPART_EXPR
1003 || TREE_CODE (*x) == IMAGPART_EXPR)
1004 x = &TREE_OPERAND (*x, 0);
1006 if (TREE_CODE (*x) != INDIRECT_REF
1007 || TREE_OPERAND (*x, 0) != var)
1010 if (TREE_TYPE (*x) == TREE_TYPE (addr_var))
1013 mark_new_vars_to_rename (stmt, vars_to_rename);
1018 /* Frontends sometimes produce expressions like *&a instead of a[0].
1019 Create a temporary variable to handle this case. */
1020 ass_stmt = build2 (MODIFY_EXPR, void_type_node, NULL_TREE, repl);
1021 new_var = duplicate_ssa_name (var, ass_stmt);
1022 TREE_OPERAND (*x, 0) = new_var;
1023 TREE_OPERAND (ass_stmt, 0) = new_var;
1025 bb = bb_for_stmt (stmt);
1026 tree_block_label (bb);
1027 bsi = bsi_after_labels (bb);
1028 bsi_insert_after (&bsi, ass_stmt, BSI_NEW_STMT);
1030 mark_new_vars_to_rename (stmt, vars_to_rename);
1033 /* Replaces immediate uses of VAR by REPL. */
1036 replace_immediate_uses (tree var, tree repl)
1043 use_operand_p use_p;
1045 df = get_immediate_uses (SSA_NAME_DEF_STMT (var));
1046 n = num_immediate_uses (df);
1048 for (i = 0; i < n; i++)
1050 stmt = immediate_use (df, i);
1052 if (TREE_CODE (stmt) == PHI_NODE)
1054 for (j = 0; j < PHI_NUM_ARGS (stmt); j++)
1055 if (PHI_ARG_DEF (stmt, j) == var)
1057 SET_PHI_ARG_DEF (stmt, j, repl);
1058 if (TREE_CODE (repl) == SSA_NAME
1059 && PHI_ARG_EDGE (stmt, j)->flags & EDGE_ABNORMAL)
1060 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (repl) = 1;
1066 get_stmt_operands (stmt);
1067 mark_new_vars = false;
1068 if (is_gimple_reg (SSA_NAME_VAR (var)))
1070 if (TREE_CODE (stmt) == MODIFY_EXPR)
1072 propagate_into_addr (stmt, var, &TREE_OPERAND (stmt, 0), repl);
1073 propagate_into_addr (stmt, var, &TREE_OPERAND (stmt, 1), repl);
1076 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
1077 if (USE_FROM_PTR (use_p) == var)
1079 propagate_value (use_p, repl);
1080 mark_new_vars = POINTER_TYPE_P (TREE_TYPE (repl));
1085 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter,
1086 SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS)
1087 if (USE_FROM_PTR (use_p) == var)
1088 propagate_value (use_p, repl);
1091 /* FIXME. If REPL is a constant, we need to fold STMT.
1092 However, fold_stmt wants a pointer to the statement, because
1093 it may happen that it needs to replace the whole statement
1094 with a new expression. Since the current def-use machinery
1095 does not return pointers to statements, we call fold_stmt
1096 with the address of a local temporary, if that call changes
1097 the temporary then we fallback on looking for a proper
1098 pointer to STMT by scanning STMT's basic block.
1100 Note that all this will become unnecessary soon. This
1101 pass is being replaced with a proper copy propagation pass
1102 for 4.1 (dnovillo, 2004-09-17). */
1103 if (TREE_CODE (repl) != SSA_NAME)
1107 mark_new_vars = true;
1110 block_stmt_iterator si = bsi_for_stmt (stmt);
1111 mark_new_vars_to_rename (tmp, vars_to_rename);
1112 redirect_immediate_uses (stmt, tmp);
1113 bsi_replace (&si, tmp, true);
1114 stmt = bsi_stmt (si);
1118 /* If REPL is a pointer, it may have different memory tags associated
1119 with it. For instance, VAR may have had a name tag while REPL
1120 only had a type tag. In these cases, the virtual operands (if
1121 any) in the statement will refer to different symbols which need
1124 mark_new_vars_to_rename (stmt, vars_to_rename);
1130 /* Gets the value VAR is equivalent to according to EQ_TO. */
1133 get_eq_name (tree *eq_to, tree var)
1138 while (TREE_CODE (val) == SSA_NAME)
1140 ver = SSA_NAME_VERSION (val);
1147 while (TREE_CODE (var) == SSA_NAME)
1149 ver = SSA_NAME_VERSION (var);
1160 /* Checks whether phi node PHI is redundant and if it is, records the ssa name
1161 its result is redundant to to EQ_TO array. */
1164 check_phi_redundancy (tree phi, tree *eq_to)
1166 tree val = NULL_TREE, def, res = PHI_RESULT (phi), stmt;
1167 unsigned i, ver = SSA_NAME_VERSION (res), n;
1170 /* It is unlikely that such large phi node would be redundant. */
1171 if (PHI_NUM_ARGS (phi) > 16)
1174 for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++)
1176 def = PHI_ARG_DEF (phi, i);
1178 if (TREE_CODE (def) == SSA_NAME)
1180 def = get_eq_name (eq_to, def);
1186 && !operand_equal_for_phi_arg_p (val, def))
1192 /* At least one of the arguments should not be equal to the result, or
1193 something strange is happening. */
1196 if (get_eq_name (eq_to, res) == val)
1199 if (!may_propagate_copy (res, val))
1204 df = get_immediate_uses (SSA_NAME_DEF_STMT (res));
1205 n = num_immediate_uses (df);
1207 for (i = 0; i < n; i++)
1209 stmt = immediate_use (df, i);
1211 if (TREE_CODE (stmt) == PHI_NODE)
1212 check_phi_redundancy (stmt, eq_to);
1216 /* Removes redundant phi nodes.
1218 A redundant PHI node is a PHI node where all of its PHI arguments
1219 are the same value, excluding any PHI arguments which are the same
1222 A redundant PHI node is effectively a copy, so we forward copy propagate
1223 which removes all uses of the destination of the PHI node then
1224 finally we delete the redundant PHI node.
1226 Note that if we can not copy propagate the PHI node, then the PHI
1227 will not be removed. Thus we do not have to worry about dependencies
1228 between PHIs and the problems serializing PHIs into copies creates.
1230 The most important effect of this pass is to remove degenerate PHI
1231 nodes created by removing unreachable code. */
1234 kill_redundant_phi_nodes (void)
1237 unsigned i, old_num_ssa_names;
1239 tree phi, var, repl, stmt;
1241 /* The EQ_TO[VER] holds the value by that the ssa name VER should be
1242 replaced. If EQ_TO[VER] is ssa name and it is decided to replace it by
1243 other value, it may be necessary to follow the chain till the final value.
1244 We perform path shortening (replacing the entries of the EQ_TO array with
1245 heads of these chains) whenever we access the field to prevent quadratic
1246 complexity (probably would not occur in practice anyway, but let us play
1248 eq_to = xcalloc (num_ssa_names, sizeof (tree));
1250 /* We have had cases where computing immediate uses takes a
1251 significant amount of compile time. If we run into such
1252 problems here, we may want to only compute immediate uses for
1253 a subset of all the SSA_NAMEs instead of computing it for
1254 all of the SSA_NAMEs. */
1255 compute_immediate_uses (TDFA_USE_OPS | TDFA_USE_VOPS, NULL);
1256 old_num_ssa_names = num_ssa_names;
1260 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1262 var = PHI_RESULT (phi);
1263 check_phi_redundancy (phi, eq_to);
1267 /* Now propagate the values. */
1268 for (i = 0; i < old_num_ssa_names; i++)
1273 repl = get_eq_name (eq_to, ssa_name (i));
1274 if (repl != ssa_name (i))
1275 replace_immediate_uses (ssa_name (i), repl);
1278 /* And remove the dead phis. */
1279 for (i = 0; i < old_num_ssa_names; i++)
1284 repl = get_eq_name (eq_to, ssa_name (i));
1285 if (repl != ssa_name (i))
1287 stmt = SSA_NAME_DEF_STMT (ssa_name (i));
1288 remove_phi_node (stmt, NULL_TREE, bb_for_stmt (stmt));
1296 struct tree_opt_pass pass_redundant_phi =
1298 "redphi", /* name */
1300 kill_redundant_phi_nodes, /* execute */
1303 0, /* static_pass_number */
1304 TV_TREE_REDPHI, /* tv_id */
1305 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1306 0, /* properties_provided */
1307 0, /* properties_destroyed */
1308 0, /* todo_flags_start */
1309 TODO_dump_func | TODO_rename_vars
1310 | TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */
1314 /* Emit warnings for uninitialized variables. This is done in two passes.
1316 The first pass notices real uses of SSA names with default definitions.
1317 Such uses are unconditionally uninitialized, and we can be certain that
1318 such a use is a mistake. This pass is run before most optimizations,
1319 so that we catch as many as we can.
1321 The second pass follows PHI nodes to find uses that are potentially
1322 uninitialized. In this case we can't necessarily prove that the use
1323 is really uninitialized. This pass is run after most optimizations,
1324 so that we thread as many jumps and possible, and delete as much dead
1325 code as possible, in order to reduce false positives. We also look
1326 again for plain uninitialized variables, since optimization may have
1327 changed conditionally uninitialized to unconditionally uninitialized. */
1329 /* Emit a warning for T, an SSA_NAME, being uninitialized. The exact
1330 warning text is in MSGID and LOCUS may contain a location or be null. */
1333 warn_uninit (tree t, const char *msgid, location_t *locus)
1335 tree var = SSA_NAME_VAR (t);
1336 tree def = SSA_NAME_DEF_STMT (t);
1338 /* Default uses (indicated by an empty definition statement),
1339 are uninitialized. */
1340 if (!IS_EMPTY_STMT (def))
1343 /* Except for PARMs of course, which are always initialized. */
1344 if (TREE_CODE (var) == PARM_DECL)
1347 /* Hard register variables get their initial value from the ether. */
1348 if (TREE_CODE (var) == VAR_DECL && DECL_HARD_REGISTER (var))
1351 /* TREE_NO_WARNING either means we already warned, or the front end
1352 wishes to suppress the warning. */
1353 if (TREE_NO_WARNING (var))
1357 locus = &DECL_SOURCE_LOCATION (var);
1358 warning (msgid, locus, var);
1359 TREE_NO_WARNING (var) = 1;
1362 /* Called via walk_tree, look for SSA_NAMEs that have empty definitions
1363 and warn about them. */
1366 warn_uninitialized_var (tree *tp, int *walk_subtrees, void *data)
1368 location_t *locus = data;
1371 /* We only do data flow with SSA_NAMEs, so that's all we can warn about. */
1372 if (TREE_CODE (t) == SSA_NAME)
1374 warn_uninit (t, "%H%qD is used uninitialized in this function", locus);
1377 else if (IS_TYPE_OR_DECL_P (t))
1383 /* Look for inputs to PHI that are SSA_NAMEs that have empty definitions
1384 and warn about them. */
1387 warn_uninitialized_phi (tree phi)
1389 int i, n = PHI_NUM_ARGS (phi);
1391 /* Don't look at memory tags. */
1392 if (!is_gimple_reg (PHI_RESULT (phi)))
1395 for (i = 0; i < n; ++i)
1397 tree op = PHI_ARG_DEF (phi, i);
1398 if (TREE_CODE (op) == SSA_NAME)
1399 warn_uninit (op, "%H%qD may be used uninitialized in this function",
1405 execute_early_warn_uninitialized (void)
1407 block_stmt_iterator bsi;
1411 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
1412 walk_tree (bsi_stmt_ptr (bsi), warn_uninitialized_var,
1413 EXPR_LOCUS (bsi_stmt (bsi)), NULL);
1417 execute_late_warn_uninitialized (void)
1422 /* Re-do the plain uninitialized variable check, as optimization may have
1423 straightened control flow. Do this first so that we don't accidentally
1424 get a "may be" warning when we'd have seen an "is" warning later. */
1425 execute_early_warn_uninitialized ();
1428 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1429 warn_uninitialized_phi (phi);
1433 gate_warn_uninitialized (void)
1435 return warn_uninitialized != 0;
1438 struct tree_opt_pass pass_early_warn_uninitialized =
1441 gate_warn_uninitialized, /* gate */
1442 execute_early_warn_uninitialized, /* execute */
1445 0, /* static_pass_number */
1447 PROP_ssa, /* properties_required */
1448 0, /* properties_provided */
1449 0, /* properties_destroyed */
1450 0, /* todo_flags_start */
1451 0, /* todo_flags_finish */
1455 struct tree_opt_pass pass_late_warn_uninitialized =
1458 gate_warn_uninitialized, /* gate */
1459 execute_late_warn_uninitialized, /* execute */
1462 0, /* static_pass_number */
1464 PROP_ssa, /* properties_required */
1465 0, /* properties_provided */
1466 0, /* properties_destroyed */
1467 0, /* todo_flags_start */
1468 0, /* todo_flags_finish */