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 gcc_assert (!need_ssa_update_p ());
651 timevar_push (TV_TREE_SSA_VERIFY);
653 /* Keep track of SSA names present in the IL. */
654 for (i = 1; i < num_ssa_names; i++)
656 tree name = ssa_name (i);
660 TREE_VISITED (name) = 0;
662 stmt = SSA_NAME_DEF_STMT (name);
663 if (!IS_EMPTY_STMT (stmt))
665 basic_block bb = bb_for_stmt (stmt);
666 verify_def (bb, definition_block,
667 name, stmt, !is_gimple_reg (name));
673 calculate_dominance_info (CDI_DOMINATORS);
675 /* Now verify all the uses and make sure they agree with the definitions
676 found in the previous pass. */
682 block_stmt_iterator bsi;
684 /* Make sure that all edges have a clear 'aux' field. */
685 FOR_EACH_EDGE (e, ei, bb->preds)
689 error ("AUX pointer initialized for edge %d->%d\n", e->src->index,
695 /* Verify the arguments for every PHI node in the block. */
696 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
698 if (verify_phi_args (phi, bb, definition_block))
700 bitmap_set_bit (names_defined_in_bb,
701 SSA_NAME_VERSION (PHI_RESULT (phi)));
704 /* Now verify all the uses and vuses in every statement of the block. */
705 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
707 tree stmt = bsi_stmt (bsi);
710 if (check_modified_stmt && stmt_modified_p (stmt))
712 error ("Stmt (0x%x) marked modified after optimization pass : ",
713 (unsigned long)stmt);
714 print_generic_stmt (stderr, stmt, TDF_VOPS);
718 if (TREE_CODE (stmt) == MODIFY_EXPR
719 && TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
721 tree lhs, base_address;
723 lhs = TREE_OPERAND (stmt, 0);
724 base_address = get_base_address (lhs);
727 && SSA_VAR_P (base_address)
728 && NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0
729 && NUM_V_MUST_DEFS (STMT_V_MUST_DEF_OPS (stmt)) == 0)
731 error ("Statement makes a memory store, but has no "
732 "V_MAY_DEFS nor V_MUST_DEFS");
733 print_generic_stmt (stderr, stmt, TDF_VOPS);
739 if (stmt_ann (stmt)->makes_aliased_stores
740 && NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0)
742 error ("Statement makes aliased stores, but has no V_MAY_DEFS");
743 print_generic_stmt (stderr, stmt, TDF_VOPS);
747 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter,
748 SSA_OP_ALL_USES | SSA_OP_ALL_KILLS)
750 op = USE_FROM_PTR (use_p);
751 if (verify_use (bb, definition_block[SSA_NAME_VERSION (op)],
752 use_p, stmt, false, !is_gimple_reg (op),
753 names_defined_in_bb))
757 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_ALL_DEFS)
758 bitmap_set_bit (names_defined_in_bb, SSA_NAME_VERSION (op));
761 bitmap_clear (names_defined_in_bb);
764 /* Finally, verify alias information. */
765 verify_alias_info ();
767 free (definition_block);
769 /* Restore the dominance information to its prior known state, so
770 that we do not perturb the compiler's subsequent behavior. */
771 if (orig_dom_state == DOM_NONE)
772 free_dominance_info (CDI_DOMINATORS);
774 dom_computed[CDI_DOMINATORS] = orig_dom_state;
776 BITMAP_FREE (names_defined_in_bb);
777 timevar_pop (TV_TREE_SSA_VERIFY);
781 internal_error ("verify_ssa failed.");
785 /* Initialize global DFA and SSA structures. */
790 VARRAY_TREE_INIT (referenced_vars, 20, "referenced_vars");
791 call_clobbered_vars = BITMAP_ALLOC (NULL);
792 addressable_vars = BITMAP_ALLOC (NULL);
795 global_var = NULL_TREE;
796 aliases_computed_p = false;
800 /* Deallocate memory associated with SSA data structures for FNDECL. */
803 delete_tree_ssa (void)
807 block_stmt_iterator bsi;
809 /* Remove annotations from every tree in the function. */
811 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
813 tree stmt = bsi_stmt (bsi);
815 ggc_free (stmt->common.ann);
816 stmt->common.ann = NULL;
819 /* Remove annotations from every referenced variable. */
822 for (i = 0; i < num_referenced_vars; i++)
824 tree var = referenced_var (i);
825 ggc_free (var->common.ann);
826 var->common.ann = NULL;
828 referenced_vars = NULL;
834 global_var = NULL_TREE;
835 BITMAP_FREE (call_clobbered_vars);
836 call_clobbered_vars = NULL;
837 BITMAP_FREE (addressable_vars);
838 addressable_vars = NULL;
839 modified_noreturn_calls = NULL;
840 aliases_computed_p = false;
841 gcc_assert (!need_ssa_update_p ());
845 /* Return true if EXPR is a useless type conversion, otherwise return
849 tree_ssa_useless_type_conversion_1 (tree outer_type, tree inner_type)
851 if (inner_type == outer_type)
854 /* Changes in machine mode are never useless conversions. */
855 if (TYPE_MODE (inner_type) != TYPE_MODE (outer_type))
858 /* If the inner and outer types are effectively the same, then
859 strip the type conversion and enter the equivalence into
861 if (lang_hooks.types_compatible_p (inner_type, outer_type))
864 /* If both types are pointers and the outer type is a (void *), then
865 the conversion is not necessary. The opposite is not true since
866 that conversion would result in a loss of information if the
867 equivalence was used. Consider an indirect function call where
868 we need to know the exact type of the function to correctly
869 implement the ABI. */
870 else if (POINTER_TYPE_P (inner_type)
871 && POINTER_TYPE_P (outer_type)
872 && TYPE_REF_CAN_ALIAS_ALL (inner_type)
873 == TYPE_REF_CAN_ALIAS_ALL (outer_type)
874 && TREE_CODE (TREE_TYPE (outer_type)) == VOID_TYPE)
877 /* Pointers and references are equivalent once we get to GENERIC,
878 so strip conversions that just switch between them. */
879 else if (POINTER_TYPE_P (inner_type)
880 && POINTER_TYPE_P (outer_type)
881 && TYPE_REF_CAN_ALIAS_ALL (inner_type)
882 == TYPE_REF_CAN_ALIAS_ALL (outer_type)
883 && lang_hooks.types_compatible_p (TREE_TYPE (inner_type),
884 TREE_TYPE (outer_type)))
887 /* If both the inner and outer types are integral types, then the
888 conversion is not necessary if they have the same mode and
889 signedness and precision, and both or neither are boolean. Some
890 code assumes an invariant that boolean types stay boolean and do
891 not become 1-bit bit-field types. Note that types with precision
892 not using all bits of the mode (such as bit-field types in C)
893 mean that testing of precision is necessary. */
894 else if (INTEGRAL_TYPE_P (inner_type)
895 && INTEGRAL_TYPE_P (outer_type)
896 && TYPE_UNSIGNED (inner_type) == TYPE_UNSIGNED (outer_type)
897 && TYPE_PRECISION (inner_type) == TYPE_PRECISION (outer_type))
899 bool first_boolean = (TREE_CODE (inner_type) == BOOLEAN_TYPE);
900 bool second_boolean = (TREE_CODE (outer_type) == BOOLEAN_TYPE);
901 if (first_boolean == second_boolean)
905 /* Recurse for complex types. */
906 else if (TREE_CODE (inner_type) == COMPLEX_TYPE
907 && TREE_CODE (outer_type) == COMPLEX_TYPE
908 && tree_ssa_useless_type_conversion_1 (TREE_TYPE (outer_type),
909 TREE_TYPE (inner_type)))
915 /* Return true if EXPR is a useless type conversion, otherwise return
919 tree_ssa_useless_type_conversion (tree expr)
921 /* If we have an assignment that merely uses a NOP_EXPR to change
922 the top of the RHS to the type of the LHS and the type conversion
923 is "safe", then strip away the type conversion so that we can
924 enter LHS = RHS into the const_and_copies table. */
925 if (TREE_CODE (expr) == NOP_EXPR || TREE_CODE (expr) == CONVERT_EXPR
926 || TREE_CODE (expr) == VIEW_CONVERT_EXPR
927 || TREE_CODE (expr) == NON_LVALUE_EXPR)
928 return tree_ssa_useless_type_conversion_1 (TREE_TYPE (expr),
929 TREE_TYPE (TREE_OPERAND (expr,
936 /* Returns true if statement STMT may read memory. */
939 stmt_references_memory_p (tree stmt)
941 stmt_ann_t ann = stmt_ann (stmt);
943 if (ann->has_volatile_ops)
946 return (NUM_VUSES (VUSE_OPS (ann)) > 0
947 || NUM_V_MAY_DEFS (V_MAY_DEF_OPS (ann)) > 0
948 || NUM_V_MUST_DEFS (V_MUST_DEF_OPS (ann)) > 0);
951 /* Internal helper for walk_use_def_chains. VAR, FN and DATA are as
952 described in walk_use_def_chains.
954 VISITED is a pointer set used to mark visited SSA_NAMEs to avoid
955 infinite loops. We used to have a bitmap for this to just mark
956 SSA versions we had visited. But non-sparse bitmaps are way too
957 expensive, while sparse bitmaps may cause quadratic behavior.
959 IS_DFS is true if the caller wants to perform a depth-first search
960 when visiting PHI nodes. A DFS will visit each PHI argument and
961 call FN after each one. Otherwise, all the arguments are
962 visited first and then FN is called with each of the visited
963 arguments in a separate pass. */
966 walk_use_def_chains_1 (tree var, walk_use_def_chains_fn fn, void *data,
967 struct pointer_set_t *visited, bool is_dfs)
971 if (pointer_set_insert (visited, var))
974 def_stmt = SSA_NAME_DEF_STMT (var);
976 if (TREE_CODE (def_stmt) != PHI_NODE)
978 /* If we reached the end of the use-def chain, call FN. */
979 return fn (var, def_stmt, data);
985 /* When doing a breadth-first search, call FN before following the
986 use-def links for each argument. */
988 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
989 if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data))
992 /* Follow use-def links out of each PHI argument. */
993 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
995 tree arg = PHI_ARG_DEF (def_stmt, i);
996 if (TREE_CODE (arg) == SSA_NAME
997 && walk_use_def_chains_1 (arg, fn, data, visited, is_dfs))
1001 /* When doing a depth-first search, call FN after following the
1002 use-def links for each argument. */
1004 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
1005 if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data))
1014 /* Walk use-def chains starting at the SSA variable VAR. Call
1015 function FN at each reaching definition found. FN takes three
1016 arguments: VAR, its defining statement (DEF_STMT) and a generic
1017 pointer to whatever state information that FN may want to maintain
1018 (DATA). FN is able to stop the walk by returning true, otherwise
1019 in order to continue the walk, FN should return false.
1021 Note, that if DEF_STMT is a PHI node, the semantics are slightly
1022 different. The first argument to FN is no longer the original
1023 variable VAR, but the PHI argument currently being examined. If FN
1024 wants to get at VAR, it should call PHI_RESULT (PHI).
1026 If IS_DFS is true, this function will:
1028 1- walk the use-def chains for all the PHI arguments, and,
1029 2- call (*FN) (ARG, PHI, DATA) on all the PHI arguments.
1031 If IS_DFS is false, the two steps above are done in reverse order
1032 (i.e., a breadth-first search). */
1036 walk_use_def_chains (tree var, walk_use_def_chains_fn fn, void *data,
1041 gcc_assert (TREE_CODE (var) == SSA_NAME);
1043 def_stmt = SSA_NAME_DEF_STMT (var);
1045 /* We only need to recurse if the reaching definition comes from a PHI
1047 if (TREE_CODE (def_stmt) != PHI_NODE)
1048 (*fn) (var, def_stmt, data);
1051 struct pointer_set_t *visited = pointer_set_create ();
1052 walk_use_def_chains_1 (var, fn, data, visited, is_dfs);
1053 pointer_set_destroy (visited);
1058 /* Emit warnings for uninitialized variables. This is done in two passes.
1060 The first pass notices real uses of SSA names with default definitions.
1061 Such uses are unconditionally uninitialized, and we can be certain that
1062 such a use is a mistake. This pass is run before most optimizations,
1063 so that we catch as many as we can.
1065 The second pass follows PHI nodes to find uses that are potentially
1066 uninitialized. In this case we can't necessarily prove that the use
1067 is really uninitialized. This pass is run after most optimizations,
1068 so that we thread as many jumps and possible, and delete as much dead
1069 code as possible, in order to reduce false positives. We also look
1070 again for plain uninitialized variables, since optimization may have
1071 changed conditionally uninitialized to unconditionally uninitialized. */
1073 /* Emit a warning for T, an SSA_NAME, being uninitialized. The exact
1074 warning text is in MSGID and LOCUS may contain a location or be null. */
1077 warn_uninit (tree t, const char *msgid, void *data)
1079 tree var = SSA_NAME_VAR (t);
1080 tree def = SSA_NAME_DEF_STMT (t);
1081 tree context = (tree) data;
1084 /* Default uses (indicated by an empty definition statement),
1085 are uninitialized. */
1086 if (!IS_EMPTY_STMT (def))
1089 /* Except for PARMs of course, which are always initialized. */
1090 if (TREE_CODE (var) == PARM_DECL)
1093 /* Hard register variables get their initial value from the ether. */
1094 if (TREE_CODE (var) == VAR_DECL && DECL_HARD_REGISTER (var))
1097 /* TREE_NO_WARNING either means we already warned, or the front end
1098 wishes to suppress the warning. */
1099 if (TREE_NO_WARNING (var))
1102 locus = (context != NULL && EXPR_HAS_LOCATION (context)
1103 ? EXPR_LOCUS (context)
1104 : &DECL_SOURCE_LOCATION (var));
1105 warning (0, msgid, locus, var);
1106 TREE_NO_WARNING (var) = 1;
1109 /* Called via walk_tree, look for SSA_NAMEs that have empty definitions
1110 and warn about them. */
1113 warn_uninitialized_var (tree *tp, int *walk_subtrees, void *data)
1117 /* We only do data flow with SSA_NAMEs, so that's all we can warn about. */
1118 if (TREE_CODE (t) == SSA_NAME)
1120 warn_uninit (t, "%H%qD is used uninitialized in this function", data);
1123 else if (IS_TYPE_OR_DECL_P (t))
1129 /* Look for inputs to PHI that are SSA_NAMEs that have empty definitions
1130 and warn about them. */
1133 warn_uninitialized_phi (tree phi)
1135 int i, n = PHI_NUM_ARGS (phi);
1137 /* Don't look at memory tags. */
1138 if (!is_gimple_reg (PHI_RESULT (phi)))
1141 for (i = 0; i < n; ++i)
1143 tree op = PHI_ARG_DEF (phi, i);
1144 if (TREE_CODE (op) == SSA_NAME)
1145 warn_uninit (op, "%H%qD may be used uninitialized in this function",
1151 execute_early_warn_uninitialized (void)
1153 block_stmt_iterator bsi;
1157 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
1159 tree context = bsi_stmt (bsi);
1160 walk_tree (bsi_stmt_ptr (bsi), warn_uninitialized_var,
1166 execute_late_warn_uninitialized (void)
1171 /* Re-do the plain uninitialized variable check, as optimization may have
1172 straightened control flow. Do this first so that we don't accidentally
1173 get a "may be" warning when we'd have seen an "is" warning later. */
1174 execute_early_warn_uninitialized ();
1177 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1178 warn_uninitialized_phi (phi);
1182 gate_warn_uninitialized (void)
1184 return warn_uninitialized != 0;
1187 struct tree_opt_pass pass_early_warn_uninitialized =
1190 gate_warn_uninitialized, /* gate */
1191 execute_early_warn_uninitialized, /* execute */
1194 0, /* static_pass_number */
1196 PROP_ssa, /* properties_required */
1197 0, /* properties_provided */
1198 0, /* properties_destroyed */
1199 0, /* todo_flags_start */
1200 0, /* todo_flags_finish */
1204 struct tree_opt_pass pass_late_warn_uninitialized =
1207 gate_warn_uninitialized, /* gate */
1208 execute_late_warn_uninitialized, /* execute */
1211 0, /* static_pass_number */
1213 PROP_ssa, /* properties_required */
1214 0, /* properties_provided */
1215 0, /* properties_destroyed */
1216 0, /* todo_flags_start */
1217 0, /* todo_flags_finish */