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 = PHI_CHAIN (phi))
63 if (PHI_ARG_DEF (phi, e->dest_idx) == NULL_TREE)
66 src = PHI_ARG_DEF (phi, e->dest_idx);
67 dst = PHI_RESULT (phi);
68 node = build_tree_list (dst, src);
70 last = &TREE_CHAIN (node);
73 e = redirect_edge_succ_nodup (e, dest);
74 PENDING_STMT (e) = list;
79 /* Add PHI arguments queued in PENDINT_STMT list on edge E to edge
83 flush_pending_stmts (edge e)
87 if (!PENDING_STMT (e))
90 for (phi = phi_nodes (e->dest), arg = PENDING_STMT (e);
92 phi = PHI_CHAIN (phi), arg = TREE_CHAIN (arg))
94 tree def = TREE_VALUE (arg);
95 add_phi_arg (phi, def, e);
98 PENDING_STMT (e) = NULL;
101 /* Return true if SSA_NAME is malformed and mark it visited.
103 IS_VIRTUAL is true if this SSA_NAME was found inside a virtual
107 verify_ssa_name (tree ssa_name, bool is_virtual)
109 if (TREE_CODE (ssa_name) != SSA_NAME)
111 error ("Expected an SSA_NAME object");
115 if (TREE_TYPE (ssa_name) != TREE_TYPE (SSA_NAME_VAR (ssa_name)))
117 error ("Type mismatch between an SSA_NAME and its symbol.");
121 if (SSA_NAME_IN_FREE_LIST (ssa_name))
123 error ("Found an SSA_NAME that had been released into the free pool");
127 if (is_virtual && is_gimple_reg (ssa_name))
129 error ("Found a virtual definition for a GIMPLE register");
133 if (!is_virtual && !is_gimple_reg (ssa_name))
135 error ("Found a real definition for a non-register");
139 if (is_virtual && var_ann (SSA_NAME_VAR (ssa_name))
140 && get_subvars_for_var (SSA_NAME_VAR (ssa_name)) != NULL)
142 error ("Found real variable when subvariables should have appeared");
150 /* Return true if the definition of SSA_NAME at block BB is malformed.
152 STMT is the statement where SSA_NAME is created.
154 DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME
155 version numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set,
156 it means that the block in that array slot contains the
157 definition of SSA_NAME.
159 IS_VIRTUAL is true if SSA_NAME is created by a V_MAY_DEF or a
163 verify_def (basic_block bb, basic_block *definition_block, tree ssa_name,
164 tree stmt, bool is_virtual)
166 if (verify_ssa_name (ssa_name, is_virtual))
169 if (definition_block[SSA_NAME_VERSION (ssa_name)])
171 error ("SSA_NAME created in two different blocks %i and %i",
172 definition_block[SSA_NAME_VERSION (ssa_name)]->index, bb->index);
176 definition_block[SSA_NAME_VERSION (ssa_name)] = bb;
178 if (SSA_NAME_DEF_STMT (ssa_name) != stmt)
180 error ("SSA_NAME_DEF_STMT is wrong");
181 fprintf (stderr, "Expected definition statement:\n");
182 print_generic_stmt (stderr, SSA_NAME_DEF_STMT (ssa_name), TDF_VOPS);
183 fprintf (stderr, "\nActual definition statement:\n");
184 print_generic_stmt (stderr, stmt, TDF_VOPS);
191 fprintf (stderr, "while verifying SSA_NAME ");
192 print_generic_expr (stderr, ssa_name, 0);
193 fprintf (stderr, " in statement\n");
194 print_generic_stmt (stderr, stmt, TDF_VOPS);
200 /* Return true if the use of SSA_NAME at statement STMT in block BB is
203 DEF_BB is the block where SSA_NAME was found to be created.
205 IDOM contains immediate dominator information for the flowgraph.
207 CHECK_ABNORMAL is true if the caller wants to check whether this use
208 is flowing through an abnormal edge (only used when checking PHI
211 IS_VIRTUAL is true if SSA_NAME is created by a V_MAY_DEF or a
214 If NAMES_DEFINED_IN_BB is not NULL, it contains a bitmap of ssa names
215 that are defined before STMT in basic block BB. */
218 verify_use (basic_block bb, basic_block def_bb, use_operand_p use_p,
219 tree stmt, bool check_abnormal, bool is_virtual,
220 bitmap names_defined_in_bb)
223 tree ssa_name = USE_FROM_PTR (use_p);
225 err = verify_ssa_name (ssa_name, is_virtual);
227 if (!TREE_VISITED (ssa_name))
228 if (verify_imm_links (stderr, ssa_name))
231 TREE_VISITED (ssa_name) = 1;
233 if (IS_EMPTY_STMT (SSA_NAME_DEF_STMT (ssa_name))
234 && var_ann (SSA_NAME_VAR (ssa_name))->default_def == ssa_name)
235 ; /* Default definitions have empty statements. Nothing to do. */
238 error ("Missing definition");
241 else if (bb != def_bb
242 && !dominated_by_p (CDI_DOMINATORS, bb, def_bb))
244 error ("Definition in block %i does not dominate use in block %i",
245 def_bb->index, bb->index);
248 else if (bb == def_bb
249 && names_defined_in_bb != NULL
250 && !bitmap_bit_p (names_defined_in_bb, SSA_NAME_VERSION (ssa_name)))
252 error ("Definition in block %i follows the use", def_bb->index);
257 && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (ssa_name))
259 error ("SSA_NAME_OCCURS_IN_ABNORMAL_PHI should be set");
263 /* Make sure the use is in an appropriate list by checking the previous
264 element to make sure it's the same. */
265 if (use_p->prev == NULL)
267 error ("No immediate_use list");
273 if (use_p->prev->use == NULL)
274 listvar = use_p->prev->stmt;
276 listvar = USE_FROM_PTR (use_p->prev);
277 if (listvar != ssa_name)
279 error ("Wrong immediate use list");
286 fprintf (stderr, "for SSA_NAME: ");
287 print_generic_expr (stderr, ssa_name, TDF_VOPS);
288 fprintf (stderr, " in statement:\n");
289 print_generic_stmt (stderr, stmt, TDF_VOPS);
296 /* Return true if any of the arguments for PHI node PHI at block BB is
299 DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME version
300 numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set, it means that the
301 block in that array slot contains the definition of SSA_NAME. */
304 verify_phi_args (tree phi, basic_block bb, basic_block *definition_block)
308 unsigned i, phi_num_args = PHI_NUM_ARGS (phi);
310 if (EDGE_COUNT (bb->preds) != phi_num_args)
312 error ("Incoming edge count does not match number of PHI arguments\n");
317 for (i = 0; i < phi_num_args; i++)
319 use_operand_p op_p = PHI_ARG_DEF_PTR (phi, i);
320 tree op = USE_FROM_PTR (op_p);
323 e = EDGE_PRED (bb, i);
327 error ("PHI argument is missing for edge %d->%d\n",
334 if (TREE_CODE (op) != SSA_NAME && !is_gimple_min_invariant (op))
336 error ("PHI argument is not SSA_NAME, or invariant");
340 if (TREE_CODE (op) == SSA_NAME)
341 err = verify_use (e->src, definition_block[SSA_NAME_VERSION (op)], op_p,
342 phi, e->flags & EDGE_ABNORMAL,
343 !is_gimple_reg (PHI_RESULT (phi)),
348 error ("Wrong edge %d->%d for PHI argument\n",
349 e->src->index, e->dest->index, bb->index);
355 fprintf (stderr, "PHI argument\n");
356 print_generic_stmt (stderr, op, TDF_VOPS);
364 fprintf (stderr, "for PHI node\n");
365 print_generic_stmt (stderr, phi, TDF_VOPS);
374 verify_flow_insensitive_alias_info (void)
378 bitmap visited = BITMAP_ALLOC (NULL);
380 for (i = 0; i < num_referenced_vars; i++)
384 varray_type may_aliases;
386 var = referenced_var (i);
388 may_aliases = ann->may_aliases;
390 for (j = 0; may_aliases && j < VARRAY_ACTIVE_SIZE (may_aliases); j++)
392 tree alias = VARRAY_TREE (may_aliases, j);
394 bitmap_set_bit (visited, var_ann (alias)->uid);
396 if (!may_be_aliased (alias))
398 error ("Non-addressable variable inside an alias set.");
399 debug_variable (alias);
405 for (i = 0; i < num_referenced_vars; i++)
409 var = referenced_var (i);
412 if (ann->mem_tag_kind == NOT_A_TAG
414 && !bitmap_bit_p (visited, ann->uid))
416 error ("Addressable variable that is an alias tag but is not in any alias set.");
421 BITMAP_FREE (visited);
425 debug_variable (var);
426 internal_error ("verify_flow_insensitive_alias_info failed.");
431 verify_flow_sensitive_alias_info (void)
436 for (i = 1; i < num_ssa_names; i++)
440 struct ptr_info_def *pi;
447 /* We only care for pointers that are actually referenced in the
449 if (!POINTER_TYPE_P (TREE_TYPE (ptr)) || !TREE_VISITED (ptr))
452 /* RESULT_DECL is special. If it's a GIMPLE register, then it
453 is only written-to only once in the return statement.
454 Otherwise, aggregate RESULT_DECLs may be written-to more than
455 once in virtual operands. */
456 var = SSA_NAME_VAR (ptr);
457 if (TREE_CODE (var) == RESULT_DECL
458 && is_gimple_reg (ptr))
461 pi = SSA_NAME_PTR_INFO (ptr);
466 if (pi->is_dereferenced && !pi->name_mem_tag && !ann->type_mem_tag)
468 error ("Dereferenced pointers should have a name or a type tag");
474 && (pi->pt_vars == NULL || bitmap_empty_p (pi->pt_vars)))
476 error ("Pointers with a memory tag, should have points-to sets or point to malloc");
480 if (pi->value_escapes_p
482 && !is_call_clobbered (pi->name_mem_tag))
484 error ("Pointer escapes but its name tag is not call-clobbered.");
492 debug_variable (ptr);
493 internal_error ("verify_flow_sensitive_alias_info failed.");
497 DEF_VEC_ALLOC_P (bitmap,heap);
499 /* Verify that all name tags have different points to sets.
500 This algorithm takes advantage of the fact that every variable with the
501 same name tag must have the same points-to set.
502 So we check a single variable for each name tag, and verify that its
503 points-to set is different from every other points-to set for other name
506 Additionally, given a pointer P_i with name tag NMT and type tag
507 TMT, this function verified the alias set of TMT is a superset of
508 the alias set of NMT. */
511 verify_name_tags (void)
515 bitmap first, second;
516 VEC(tree,heap) *name_tag_reps = NULL;
517 VEC(bitmap,heap) *pt_vars_for_reps = NULL;
518 bitmap type_aliases = BITMAP_ALLOC (NULL);
520 /* First we compute the name tag representatives and their points-to sets. */
521 for (i = 0; i < num_ssa_names; i++)
523 struct ptr_info_def *pi;
524 tree tmt, ptr = ssa_name (i);
526 if (ptr == NULL_TREE)
529 pi = SSA_NAME_PTR_INFO (ptr);
531 if (!TREE_VISITED (ptr)
532 || !POINTER_TYPE_P (TREE_TYPE (ptr))
535 || TREE_VISITED (pi->name_mem_tag))
538 TREE_VISITED (pi->name_mem_tag) = 1;
540 if (pi->pt_vars == NULL)
543 VEC_safe_push (tree, heap, name_tag_reps, ptr);
544 VEC_safe_push (bitmap, heap, pt_vars_for_reps, pi->pt_vars);
546 /* Verify that alias set of PTR's type tag is a superset of the
547 alias set of PTR's name tag. */
548 tmt = var_ann (SSA_NAME_VAR (ptr))->type_mem_tag;
552 varray_type aliases = var_ann (tmt)->may_aliases;
553 bitmap_clear (type_aliases);
554 for (i = 0; aliases && i < VARRAY_ACTIVE_SIZE (aliases); i++)
556 tree alias = VARRAY_TREE (aliases, i);
557 bitmap_set_bit (type_aliases, var_ann (alias)->uid);
560 /* When grouping, we may have added PTR's type tag into the
561 alias set of PTR's name tag. To prevent a false
562 positive, pretend that TMT is in its own alias set. */
563 bitmap_set_bit (type_aliases, var_ann (tmt)->uid);
565 if (bitmap_equal_p (type_aliases, pi->pt_vars))
568 if (!bitmap_intersect_compl_p (type_aliases, pi->pt_vars))
570 error ("Alias set of a pointer's type tag should be a superset of the corresponding name tag");
571 debug_variable (tmt);
572 debug_variable (pi->name_mem_tag);
578 /* Now compare all the representative bitmaps with all other representative
579 bitmaps, to verify that they are all different. */
580 for (i = 0; VEC_iterate (bitmap, pt_vars_for_reps, i, first); i++)
582 for (j = i + 1; VEC_iterate (bitmap, pt_vars_for_reps, j, second); j++)
584 if (bitmap_equal_p (first, second))
586 error ("Two different pointers with identical points-to sets but different name tags");
587 debug_variable (VEC_index (tree, name_tag_reps, j));
593 /* Lastly, clear out the visited flags. */
594 for (i = 0; i < num_ssa_names; i++)
598 tree ptr = ssa_name (i);
599 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
600 if (!TREE_VISITED (ptr)
601 || !POINTER_TYPE_P (TREE_TYPE (ptr))
603 || !pi->name_mem_tag)
605 TREE_VISITED (pi->name_mem_tag) = 0;
609 /* We do not have to free the bitmaps or trees in the vectors, as
610 they are not owned by us. */
611 VEC_free (bitmap, heap, pt_vars_for_reps);
612 VEC_free (tree, heap, name_tag_reps);
613 BITMAP_FREE (type_aliases);
617 debug_variable (VEC_index (tree, name_tag_reps, i));
618 internal_error ("verify_name_tags failed");
622 /* Verify the consistency of aliasing information. */
625 verify_alias_info (void)
627 verify_flow_sensitive_alias_info ();
629 verify_flow_insensitive_alias_info ();
633 /* Verify common invariants in the SSA web.
634 TODO: verify the variable annotations. */
637 verify_ssa (bool check_modified_stmt)
641 basic_block *definition_block = xcalloc (num_ssa_names, sizeof (basic_block));
644 enum dom_state orig_dom_state = dom_computed[CDI_DOMINATORS];
645 bitmap names_defined_in_bb = BITMAP_ALLOC (NULL);
647 timevar_push (TV_TREE_SSA_VERIFY);
649 /* Keep track of SSA names present in the IL. */
650 for (i = 1; i < num_ssa_names; i++)
652 tree name = ssa_name (i);
656 TREE_VISITED (name) = 0;
658 stmt = SSA_NAME_DEF_STMT (name);
659 if (!IS_EMPTY_STMT (stmt))
661 basic_block bb = bb_for_stmt (stmt);
662 verify_def (bb, definition_block,
663 name, stmt, !is_gimple_reg (name));
669 calculate_dominance_info (CDI_DOMINATORS);
671 /* Now verify all the uses and make sure they agree with the definitions
672 found in the previous pass. */
678 block_stmt_iterator bsi;
680 /* Make sure that all edges have a clear 'aux' field. */
681 FOR_EACH_EDGE (e, ei, bb->preds)
685 error ("AUX pointer initialized for edge %d->%d\n", e->src->index,
691 /* Verify the arguments for every PHI node in the block. */
692 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
694 if (verify_phi_args (phi, bb, definition_block))
696 bitmap_set_bit (names_defined_in_bb,
697 SSA_NAME_VERSION (PHI_RESULT (phi)));
700 /* Now verify all the uses and vuses in every statement of the block. */
701 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
703 tree stmt = bsi_stmt (bsi);
706 if (check_modified_stmt && stmt_modified_p (stmt))
708 error ("Stmt (0x%x) marked modified after optimization pass : ",
709 (unsigned long)stmt);
710 print_generic_stmt (stderr, stmt, TDF_VOPS);
714 if (TREE_CODE (stmt) == MODIFY_EXPR
715 && TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
717 tree lhs, base_address;
719 lhs = TREE_OPERAND (stmt, 0);
720 base_address = get_base_address (lhs);
723 && SSA_VAR_P (base_address)
724 && NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0
725 && NUM_V_MUST_DEFS (STMT_V_MUST_DEF_OPS (stmt)) == 0)
727 error ("Statement makes a memory store, but has no "
728 "V_MAY_DEFS nor V_MUST_DEFS");
729 print_generic_stmt (stderr, stmt, TDF_VOPS);
735 if (stmt_ann (stmt)->makes_aliased_stores
736 && NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0)
738 error ("Statement makes aliased stores, but has no V_MAY_DEFS");
739 print_generic_stmt (stderr, stmt, TDF_VOPS);
743 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter,
744 SSA_OP_ALL_USES | SSA_OP_ALL_KILLS)
746 op = USE_FROM_PTR (use_p);
747 if (verify_use (bb, definition_block[SSA_NAME_VERSION (op)],
748 use_p, stmt, false, !is_gimple_reg (op),
749 names_defined_in_bb))
753 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_ALL_DEFS)
755 bitmap_set_bit (names_defined_in_bb, SSA_NAME_VERSION (op));
759 bitmap_clear (names_defined_in_bb);
762 /* Finally, verify alias information. */
763 verify_alias_info ();
765 free (definition_block);
766 /* Restore the dominance information to its prior known state, so
767 that we do not perturb the compiler's subsequent behavior. */
768 if (orig_dom_state == DOM_NONE)
769 free_dominance_info (CDI_DOMINATORS);
771 dom_computed[CDI_DOMINATORS] = orig_dom_state;
773 BITMAP_FREE (names_defined_in_bb);
774 timevar_pop (TV_TREE_SSA_VERIFY);
778 internal_error ("verify_ssa failed.");
782 /* Initialize global DFA and SSA structures. */
787 VARRAY_TREE_INIT (referenced_vars, 20, "referenced_vars");
788 call_clobbered_vars = BITMAP_ALLOC (NULL);
789 addressable_vars = BITMAP_ALLOC (NULL);
792 global_var = NULL_TREE;
793 aliases_computed_p = false;
797 /* Deallocate memory associated with SSA data structures for FNDECL. */
800 delete_tree_ssa (void)
804 block_stmt_iterator bsi;
806 /* Remove annotations from every tree in the function. */
808 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
810 tree stmt = bsi_stmt (bsi);
812 ggc_free (stmt->common.ann);
813 stmt->common.ann = NULL;
816 /* Remove annotations from every referenced variable. */
819 for (i = 0; i < num_referenced_vars; i++)
821 tree var = referenced_var (i);
822 ggc_free (var->common.ann);
823 var->common.ann = NULL;
825 referenced_vars = NULL;
831 global_var = NULL_TREE;
832 BITMAP_FREE (call_clobbered_vars);
833 call_clobbered_vars = NULL;
834 BITMAP_FREE (addressable_vars);
835 addressable_vars = NULL;
836 modified_noreturn_calls = NULL;
837 aliases_computed_p = false;
841 /* Return true if EXPR is a useless type conversion, otherwise return
845 tree_ssa_useless_type_conversion_1 (tree outer_type, tree inner_type)
847 if (inner_type == outer_type)
850 /* Changes in machine mode are never useless conversions. */
851 if (TYPE_MODE (inner_type) != TYPE_MODE (outer_type))
854 /* If the inner and outer types are effectively the same, then
855 strip the type conversion and enter the equivalence into
857 if (lang_hooks.types_compatible_p (inner_type, outer_type))
860 /* If both types are pointers and the outer type is a (void *), then
861 the conversion is not necessary. The opposite is not true since
862 that conversion would result in a loss of information if the
863 equivalence was used. Consider an indirect function call where
864 we need to know the exact type of the function to correctly
865 implement the ABI. */
866 else if (POINTER_TYPE_P (inner_type)
867 && POINTER_TYPE_P (outer_type)
868 && TYPE_REF_CAN_ALIAS_ALL (inner_type)
869 == TYPE_REF_CAN_ALIAS_ALL (outer_type)
870 && TREE_CODE (TREE_TYPE (outer_type)) == VOID_TYPE)
873 /* Pointers and references are equivalent once we get to GENERIC,
874 so strip conversions that just switch between them. */
875 else if (POINTER_TYPE_P (inner_type)
876 && POINTER_TYPE_P (outer_type)
877 && TYPE_REF_CAN_ALIAS_ALL (inner_type)
878 == TYPE_REF_CAN_ALIAS_ALL (outer_type)
879 && lang_hooks.types_compatible_p (TREE_TYPE (inner_type),
880 TREE_TYPE (outer_type)))
883 /* If both the inner and outer types are integral types, then the
884 conversion is not necessary if they have the same mode and
885 signedness and precision, and both or neither are boolean. Some
886 code assumes an invariant that boolean types stay boolean and do
887 not become 1-bit bit-field types. Note that types with precision
888 not using all bits of the mode (such as bit-field types in C)
889 mean that testing of precision is necessary. */
890 else if (INTEGRAL_TYPE_P (inner_type)
891 && INTEGRAL_TYPE_P (outer_type)
892 && TYPE_UNSIGNED (inner_type) == TYPE_UNSIGNED (outer_type)
893 && TYPE_PRECISION (inner_type) == TYPE_PRECISION (outer_type))
895 bool first_boolean = (TREE_CODE (inner_type) == BOOLEAN_TYPE);
896 bool second_boolean = (TREE_CODE (outer_type) == BOOLEAN_TYPE);
897 if (first_boolean == second_boolean)
901 /* Recurse for complex types. */
902 else if (TREE_CODE (inner_type) == COMPLEX_TYPE
903 && TREE_CODE (outer_type) == COMPLEX_TYPE
904 && tree_ssa_useless_type_conversion_1 (TREE_TYPE (outer_type),
905 TREE_TYPE (inner_type)))
911 /* Return true if EXPR is a useless type conversion, otherwise return
915 tree_ssa_useless_type_conversion (tree expr)
917 /* If we have an assignment that merely uses a NOP_EXPR to change
918 the top of the RHS to the type of the LHS and the type conversion
919 is "safe", then strip away the type conversion so that we can
920 enter LHS = RHS into the const_and_copies table. */
921 if (TREE_CODE (expr) == NOP_EXPR || TREE_CODE (expr) == CONVERT_EXPR
922 || TREE_CODE (expr) == VIEW_CONVERT_EXPR
923 || TREE_CODE (expr) == NON_LVALUE_EXPR)
924 return tree_ssa_useless_type_conversion_1 (TREE_TYPE (expr),
925 TREE_TYPE (TREE_OPERAND (expr,
932 /* Returns true if statement STMT may read memory. */
935 stmt_references_memory_p (tree stmt)
937 stmt_ann_t ann = stmt_ann (stmt);
939 if (ann->has_volatile_ops)
942 return (NUM_VUSES (VUSE_OPS (ann)) > 0
943 || NUM_V_MAY_DEFS (V_MAY_DEF_OPS (ann)) > 0
944 || NUM_V_MUST_DEFS (V_MUST_DEF_OPS (ann)) > 0);
947 /* Internal helper for walk_use_def_chains. VAR, FN and DATA are as
948 described in walk_use_def_chains.
950 VISITED is a pointer set used to mark visited SSA_NAMEs to avoid
951 infinite loops. We used to have a bitmap for this to just mark
952 SSA versions we had visited. But non-sparse bitmaps are way too
953 expensive, while sparse bitmaps may cause quadratic behavior.
955 IS_DFS is true if the caller wants to perform a depth-first search
956 when visiting PHI nodes. A DFS will visit each PHI argument and
957 call FN after each one. Otherwise, all the arguments are
958 visited first and then FN is called with each of the visited
959 arguments in a separate pass. */
962 walk_use_def_chains_1 (tree var, walk_use_def_chains_fn fn, void *data,
963 struct pointer_set_t *visited, bool is_dfs)
967 if (pointer_set_insert (visited, var))
970 def_stmt = SSA_NAME_DEF_STMT (var);
972 if (TREE_CODE (def_stmt) != PHI_NODE)
974 /* If we reached the end of the use-def chain, call FN. */
975 return fn (var, def_stmt, data);
981 /* When doing a breadth-first search, call FN before following the
982 use-def links for each argument. */
984 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
985 if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data))
988 /* Follow use-def links out of each PHI argument. */
989 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
991 tree arg = PHI_ARG_DEF (def_stmt, i);
992 if (TREE_CODE (arg) == SSA_NAME
993 && walk_use_def_chains_1 (arg, fn, data, visited, is_dfs))
997 /* When doing a depth-first search, call FN after following the
998 use-def links for each argument. */
1000 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
1001 if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data))
1010 /* Walk use-def chains starting at the SSA variable VAR. Call
1011 function FN at each reaching definition found. FN takes three
1012 arguments: VAR, its defining statement (DEF_STMT) and a generic
1013 pointer to whatever state information that FN may want to maintain
1014 (DATA). FN is able to stop the walk by returning true, otherwise
1015 in order to continue the walk, FN should return false.
1017 Note, that if DEF_STMT is a PHI node, the semantics are slightly
1018 different. The first argument to FN is no longer the original
1019 variable VAR, but the PHI argument currently being examined. If FN
1020 wants to get at VAR, it should call PHI_RESULT (PHI).
1022 If IS_DFS is true, this function will:
1024 1- walk the use-def chains for all the PHI arguments, and,
1025 2- call (*FN) (ARG, PHI, DATA) on all the PHI arguments.
1027 If IS_DFS is false, the two steps above are done in reverse order
1028 (i.e., a breadth-first search). */
1032 walk_use_def_chains (tree var, walk_use_def_chains_fn fn, void *data,
1037 gcc_assert (TREE_CODE (var) == SSA_NAME);
1039 def_stmt = SSA_NAME_DEF_STMT (var);
1041 /* We only need to recurse if the reaching definition comes from a PHI
1043 if (TREE_CODE (def_stmt) != PHI_NODE)
1044 (*fn) (var, def_stmt, data);
1047 struct pointer_set_t *visited = pointer_set_create ();
1048 walk_use_def_chains_1 (var, fn, data, visited, is_dfs);
1049 pointer_set_destroy (visited);
1054 /* Emit warnings for uninitialized variables. This is done in two passes.
1056 The first pass notices real uses of SSA names with default definitions.
1057 Such uses are unconditionally uninitialized, and we can be certain that
1058 such a use is a mistake. This pass is run before most optimizations,
1059 so that we catch as many as we can.
1061 The second pass follows PHI nodes to find uses that are potentially
1062 uninitialized. In this case we can't necessarily prove that the use
1063 is really uninitialized. This pass is run after most optimizations,
1064 so that we thread as many jumps and possible, and delete as much dead
1065 code as possible, in order to reduce false positives. We also look
1066 again for plain uninitialized variables, since optimization may have
1067 changed conditionally uninitialized to unconditionally uninitialized. */
1069 /* Emit a warning for T, an SSA_NAME, being uninitialized. The exact
1070 warning text is in MSGID and LOCUS may contain a location or be null. */
1073 warn_uninit (tree t, const char *msgid, void *data)
1075 tree var = SSA_NAME_VAR (t);
1076 tree def = SSA_NAME_DEF_STMT (t);
1077 tree context = (tree) data;
1080 /* Default uses (indicated by an empty definition statement),
1081 are uninitialized. */
1082 if (!IS_EMPTY_STMT (def))
1085 /* Except for PARMs of course, which are always initialized. */
1086 if (TREE_CODE (var) == PARM_DECL)
1089 /* Hard register variables get their initial value from the ether. */
1090 if (TREE_CODE (var) == VAR_DECL && DECL_HARD_REGISTER (var))
1093 /* TREE_NO_WARNING either means we already warned, or the front end
1094 wishes to suppress the warning. */
1095 if (TREE_NO_WARNING (var))
1098 locus = (context != NULL && EXPR_HAS_LOCATION (context)
1099 ? EXPR_LOCUS (context)
1100 : &DECL_SOURCE_LOCATION (var));
1101 warning (msgid, locus, var);
1102 TREE_NO_WARNING (var) = 1;
1105 /* Called via walk_tree, look for SSA_NAMEs that have empty definitions
1106 and warn about them. */
1109 warn_uninitialized_var (tree *tp, int *walk_subtrees, void *data)
1113 /* We only do data flow with SSA_NAMEs, so that's all we can warn about. */
1114 if (TREE_CODE (t) == SSA_NAME)
1116 warn_uninit (t, "%H%qD is used uninitialized in this function", data);
1119 else if (IS_TYPE_OR_DECL_P (t))
1125 /* Look for inputs to PHI that are SSA_NAMEs that have empty definitions
1126 and warn about them. */
1129 warn_uninitialized_phi (tree phi)
1131 int i, n = PHI_NUM_ARGS (phi);
1133 /* Don't look at memory tags. */
1134 if (!is_gimple_reg (PHI_RESULT (phi)))
1137 for (i = 0; i < n; ++i)
1139 tree op = PHI_ARG_DEF (phi, i);
1140 if (TREE_CODE (op) == SSA_NAME)
1141 warn_uninit (op, "%H%qD may be used uninitialized in this function",
1147 execute_early_warn_uninitialized (void)
1149 block_stmt_iterator bsi;
1153 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
1155 tree context = bsi_stmt (bsi);
1156 walk_tree (bsi_stmt_ptr (bsi), warn_uninitialized_var,
1162 execute_late_warn_uninitialized (void)
1167 /* Re-do the plain uninitialized variable check, as optimization may have
1168 straightened control flow. Do this first so that we don't accidentally
1169 get a "may be" warning when we'd have seen an "is" warning later. */
1170 execute_early_warn_uninitialized ();
1173 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1174 warn_uninitialized_phi (phi);
1178 gate_warn_uninitialized (void)
1180 return warn_uninitialized != 0;
1183 struct tree_opt_pass pass_early_warn_uninitialized =
1186 gate_warn_uninitialized, /* gate */
1187 execute_early_warn_uninitialized, /* execute */
1190 0, /* static_pass_number */
1192 PROP_ssa, /* properties_required */
1193 0, /* properties_provided */
1194 0, /* properties_destroyed */
1195 0, /* todo_flags_start */
1196 0, /* todo_flags_finish */
1200 struct tree_opt_pass pass_late_warn_uninitialized =
1203 gate_warn_uninitialized, /* gate */
1204 execute_late_warn_uninitialized, /* execute */
1207 0, /* static_pass_number */
1209 PROP_ssa, /* properties_required */
1210 0, /* properties_provided */
1211 0, /* properties_destroyed */
1212 0, /* todo_flags_start */
1213 0, /* todo_flags_finish */