1 /* Miscellaneous SSA utility functions.
2 Copyright (C) 2001, 2002, 2003, 2004 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 "tree-flow.h"
40 #include "tree-gimple.h"
41 #include "tree-inline.h"
45 #include "tree-dump.h"
46 #include "tree-pass.h"
49 /* Remove edge E and remove the corresponding arguments from the PHI nodes
50 in E's destination block. */
53 ssa_remove_edge (edge e)
57 /* Remove the appropriate PHI arguments in E's destination block. */
58 for (phi = phi_nodes (e->dest); phi; phi = next)
60 next = PHI_CHAIN (phi);
61 remove_phi_arg (phi, e->src);
67 /* Remove the corresponding arguments from the PHI nodes in E's
68 destination block and redirect it to DEST. Return redirected edge.
69 The list of removed arguments is stored in PENDING_STMT (e). */
72 ssa_redirect_edge (edge e, basic_block dest)
75 tree list = NULL, *last = &list;
79 /* Remove the appropriate PHI arguments in E's destination block. */
80 for (phi = phi_nodes (e->dest); phi; phi = next)
82 next = PHI_CHAIN (phi);
84 i = phi_arg_from_edge (phi, e);
88 src = PHI_ARG_DEF (phi, i);
89 dst = PHI_RESULT (phi);
90 node = build_tree_list (dst, src);
92 last = &TREE_CHAIN (node);
94 remove_phi_arg_num (phi, i);
97 e = redirect_edge_succ_nodup (e, dest);
98 PENDING_STMT (e) = list;
103 /* Add PHI arguments queued in PENDINT_STMT list on edge E to edge
107 flush_pending_stmts (edge e)
111 if (!PENDING_STMT (e))
114 for (phi = phi_nodes (e->dest), arg = PENDING_STMT (e);
116 phi = TREE_CHAIN (phi), arg = TREE_CHAIN (arg))
118 tree def = TREE_VALUE (arg);
119 add_phi_arg (&phi, def, e);
122 PENDING_STMT (e) = NULL;
125 /* Return true if SSA_NAME is malformed and mark it visited.
127 IS_VIRTUAL is true if this SSA_NAME was found inside a virtual
131 verify_ssa_name (tree ssa_name, bool is_virtual)
133 TREE_VISITED (ssa_name) = 1;
135 if (TREE_CODE (ssa_name) != SSA_NAME)
137 error ("Expected an SSA_NAME object");
141 if (TREE_TYPE (ssa_name) != TREE_TYPE (SSA_NAME_VAR (ssa_name)))
143 error ("Type mismatch between an SSA_NAME and its symbol.");
147 if (SSA_NAME_IN_FREE_LIST (ssa_name))
149 error ("Found an SSA_NAME that had been released into the free pool");
153 if (is_virtual && is_gimple_reg (ssa_name))
155 error ("Found a virtual definition for a GIMPLE register");
159 if (!is_virtual && !is_gimple_reg (ssa_name))
161 error ("Found a real definition for a non-register");
169 /* Return true if the definition of SSA_NAME at block BB is malformed.
171 STMT is the statement where SSA_NAME is created.
173 DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME
174 version numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set,
175 it means that the block in that array slot contains the
176 definition of SSA_NAME.
178 IS_VIRTUAL is true if SSA_NAME is created by a V_MAY_DEF or a
182 verify_def (basic_block bb, basic_block *definition_block, tree ssa_name,
183 tree stmt, bool is_virtual)
185 if (verify_ssa_name (ssa_name, is_virtual))
188 if (definition_block[SSA_NAME_VERSION (ssa_name)])
190 error ("SSA_NAME created in two different blocks %i and %i",
191 definition_block[SSA_NAME_VERSION (ssa_name)]->index, bb->index);
195 definition_block[SSA_NAME_VERSION (ssa_name)] = bb;
197 if (SSA_NAME_DEF_STMT (ssa_name) != stmt)
199 error ("SSA_NAME_DEF_STMT is wrong");
200 fprintf (stderr, "Expected definition statement:\n");
201 print_generic_stmt (stderr, SSA_NAME_DEF_STMT (ssa_name), TDF_VOPS);
202 fprintf (stderr, "\nActual definition statement:\n");
203 print_generic_stmt (stderr, stmt, TDF_VOPS);
210 fprintf (stderr, "while verifying SSA_NAME ");
211 print_generic_expr (stderr, ssa_name, 0);
212 fprintf (stderr, " in statement\n");
213 print_generic_stmt (stderr, stmt, TDF_VOPS);
219 /* Return true if the use of SSA_NAME at statement STMT in block BB is
222 DEF_BB is the block where SSA_NAME was found to be created.
224 IDOM contains immediate dominator information for the flowgraph.
226 CHECK_ABNORMAL is true if the caller wants to check whether this use
227 is flowing through an abnormal edge (only used when checking PHI
230 IS_VIRTUAL is true if SSA_NAME is created by a V_MAY_DEF or a
233 If NAMES_DEFINED_IN_BB is not NULL, it contains a bitmap of ssa names
234 that are defined before STMT in basic block BB. */
237 verify_use (basic_block bb, basic_block def_bb, tree ssa_name,
238 tree stmt, bool check_abnormal, bool is_virtual,
239 bitmap names_defined_in_bb)
243 err = verify_ssa_name (ssa_name, is_virtual);
245 if (IS_EMPTY_STMT (SSA_NAME_DEF_STMT (ssa_name))
246 && var_ann (SSA_NAME_VAR (ssa_name))->default_def == ssa_name)
247 ; /* Default definitions have empty statements. Nothing to do. */
250 error ("Missing definition");
253 else if (bb != def_bb
254 && !dominated_by_p (CDI_DOMINATORS, bb, def_bb))
256 error ("Definition in block %i does not dominate use in block %i",
257 def_bb->index, bb->index);
260 else if (bb == def_bb
261 && names_defined_in_bb != NULL
262 && !bitmap_bit_p (names_defined_in_bb, SSA_NAME_VERSION (ssa_name)))
264 error ("Definition in block %i follows the use", def_bb->index);
269 && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (ssa_name))
271 error ("SSA_NAME_OCCURS_IN_ABNORMAL_PHI should be set");
277 fprintf (stderr, "for SSA_NAME: ");
278 print_generic_expr (stderr, ssa_name, TDF_VOPS);
279 fprintf (stderr, "in statement:\n");
280 print_generic_stmt (stderr, stmt, TDF_VOPS);
287 /* Return true if any of the arguments for PHI node PHI at block BB is
290 IDOM contains immediate dominator information for the flowgraph.
292 DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME version
293 numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set, it means that the
294 block in that array slot contains the definition of SSA_NAME. */
297 verify_phi_args (tree phi, basic_block bb, basic_block *definition_block)
301 int i, phi_num_args = PHI_NUM_ARGS (phi);
304 /* Mark all the incoming edges. */
305 FOR_EACH_EDGE (e, ei, bb->preds)
308 for (i = 0; i < phi_num_args; i++)
310 tree op = PHI_ARG_DEF (phi, i);
312 e = PHI_ARG_EDGE (phi, i);
314 if (TREE_CODE (op) == SSA_NAME)
315 err = verify_use (e->src, definition_block[SSA_NAME_VERSION (op)], op,
316 phi, e->flags & EDGE_ABNORMAL,
317 !is_gimple_reg (PHI_RESULT (phi)),
322 error ("Wrong edge %d->%d for PHI argument\n",
323 e->src->index, e->dest->index, bb->index);
327 if (e->aux == (void *) 0)
329 error ("PHI argument flowing through dead edge %d->%d\n",
330 e->src->index, e->dest->index);
334 if (e->aux == (void *) 2)
336 error ("PHI argument duplicated for edge %d->%d\n", e->src->index,
343 fprintf (stderr, "PHI argument\n");
344 print_generic_stmt (stderr, op, TDF_VOPS);
351 FOR_EACH_EDGE (e, ei, bb->preds)
353 if (e->aux != (void *) 2)
355 error ("No argument flowing through edge %d->%d\n", e->src->index,
366 fprintf (stderr, "for PHI node\n");
367 print_generic_stmt (stderr, phi, TDF_VOPS);
376 verify_flow_insensitive_alias_info (void)
380 bitmap visited = BITMAP_XMALLOC ();
382 for (i = 0; i < num_referenced_vars; i++)
386 varray_type may_aliases;
388 var = referenced_var (i);
390 may_aliases = ann->may_aliases;
392 for (j = 0; may_aliases && j < VARRAY_ACTIVE_SIZE (may_aliases); j++)
394 tree alias = VARRAY_TREE (may_aliases, j);
396 bitmap_set_bit (visited, var_ann (alias)->uid);
398 if (!may_be_aliased (alias))
400 error ("Non-addressable variable inside an alias set.");
401 debug_variable (alias);
407 for (i = 0; i < num_referenced_vars; i++)
411 var = referenced_var (i);
414 if (ann->mem_tag_kind == NOT_A_TAG
416 && !bitmap_bit_p (visited, ann->uid))
418 error ("Addressable variable that is an alias tag but is not in any alias set.");
423 BITMAP_XFREE (visited);
427 debug_variable (var);
428 internal_error ("verify_flow_insensitive_alias_info failed.");
433 verify_flow_sensitive_alias_info (void)
438 for (i = 1; i < num_ssa_names; i++)
441 struct ptr_info_def *pi;
446 ann = var_ann (SSA_NAME_VAR (ptr));
447 pi = SSA_NAME_PTR_INFO (ptr);
449 /* We only care for pointers that are actually referenced in the
451 if (!TREE_VISITED (ptr) || !POINTER_TYPE_P (TREE_TYPE (ptr)))
454 /* RESULT_DECL is special. If it's a GIMPLE register, then it
455 is only written-to only once in the return statement.
456 Otherwise, aggregate RESULT_DECLs may be written-to more than
457 once in virtual operands. */
458 if (TREE_CODE (SSA_NAME_VAR (ptr)) == RESULT_DECL
459 && is_gimple_reg (ptr))
465 if (pi->is_dereferenced && !pi->name_mem_tag && !ann->type_mem_tag)
467 error ("Dereferenced pointers should have a name or a type tag");
473 && (pi->pt_vars == NULL
474 || bitmap_first_set_bit (pi->pt_vars) < 0))
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.");
496 DEF_VEC_MALLOC_P (bitmap);
498 /* Verify that all name tags have different points to sets.
499 This algorithm takes advantage of the fact that every variable with the
500 same name tag must have the same points-to set.
501 So we check a single variable for each name tag, and verify that its
502 points-to set is different from every other points-to set for other name
506 verify_name_tags (void)
510 bitmap first, second;
511 VEC (tree) *name_tag_reps = NULL;
512 VEC (bitmap) *pt_vars_for_reps = NULL;
514 /* First we compute the name tag representatives and their points-to sets. */
515 for (i = 0; i < num_ssa_names; i++)
519 tree ptr = ssa_name (i);
520 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
521 if (!TREE_VISITED (ptr)
522 || !POINTER_TYPE_P (TREE_TYPE (ptr))
525 || TREE_VISITED (pi->name_mem_tag))
527 TREE_VISITED (pi->name_mem_tag) = 1;
528 if (pi->pt_vars != NULL)
530 VEC_safe_push (tree, name_tag_reps, ptr);
531 VEC_safe_push (bitmap, pt_vars_for_reps, pi->pt_vars);
536 /* Now compare all the representative bitmaps with all other representative
537 bitmaps, to verify that they are all different. */
538 for (i = 0; VEC_iterate (bitmap, pt_vars_for_reps, i, first); i++)
540 for (j = i + 1; VEC_iterate (bitmap, pt_vars_for_reps, j, second); j++)
542 if (bitmap_equal_p (first, second))
544 error ("Two different pointers with identical points-to sets but different name tags");
545 debug_variable (VEC_index (tree, name_tag_reps, j));
551 /* Lastly, clear out the visited flags. */
552 for (i = 0; i < num_ssa_names; i++)
556 tree ptr = ssa_name (i);
557 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
558 if (!TREE_VISITED (ptr)
559 || !POINTER_TYPE_P (TREE_TYPE (ptr))
561 || !pi->name_mem_tag)
563 TREE_VISITED (pi->name_mem_tag) = 0;
566 VEC_free (bitmap, pt_vars_for_reps);
570 debug_variable (VEC_index (tree, name_tag_reps, i));
571 internal_error ("verify_name_tags failed");
573 /* Verify the consistency of aliasing information. */
576 verify_alias_info (void)
578 verify_flow_sensitive_alias_info ();
580 verify_flow_insensitive_alias_info ();
584 /* Verify common invariants in the SSA web.
585 TODO: verify the variable annotations. */
592 basic_block *definition_block = xcalloc (num_ssa_names, sizeof (basic_block));
595 enum dom_state orig_dom_state = dom_computed[CDI_DOMINATORS];
596 bitmap names_defined_in_bb = BITMAP_XMALLOC ();
598 timevar_push (TV_TREE_SSA_VERIFY);
600 /* Keep track of SSA names present in the IL. */
601 for (i = 1; i < num_ssa_names; i++)
603 TREE_VISITED (ssa_name (i)) = 0;
605 calculate_dominance_info (CDI_DOMINATORS);
607 /* Verify and register all the SSA_NAME definitions found in the
612 block_stmt_iterator bsi;
614 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
617 if (verify_def (bb, definition_block, PHI_RESULT (phi), phi,
618 !is_gimple_reg (PHI_RESULT (phi))))
620 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
622 tree def = PHI_ARG_DEF (phi, i);
623 if (TREE_CODE (def) != SSA_NAME && !is_gimple_min_invariant (def))
625 error ("PHI argument is not SSA_NAME, or invariant");
626 print_generic_stmt (stderr, phi, TDF_VOPS);
632 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
636 stmt = bsi_stmt (bsi);
637 get_stmt_operands (stmt);
639 if (stmt_ann (stmt)->makes_aliased_stores
640 && NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0)
642 error ("Statement makes aliased stores, but has no V_MAY_DEFS");
643 print_generic_stmt (stderr, stmt, TDF_VOPS);
647 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS)
649 if (verify_def (bb, definition_block, op, stmt, true))
653 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
655 if (verify_def (bb, definition_block, op, stmt, false))
662 /* Now verify all the uses and make sure they agree with the definitions
663 found in the previous pass. */
669 block_stmt_iterator bsi;
671 /* Make sure that all edges have a clear 'aux' field. */
672 FOR_EACH_EDGE (e, ei, bb->preds)
676 error ("AUX pointer initialized for edge %d->%d\n", e->src->index,
682 /* Verify the arguments for every PHI node in the block. */
683 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
685 if (verify_phi_args (phi, bb, definition_block))
687 bitmap_set_bit (names_defined_in_bb,
688 SSA_NAME_VERSION (PHI_RESULT (phi)));
691 /* Now verify all the uses and vuses in every statement of the block. */
692 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
694 tree stmt = bsi_stmt (bsi);
696 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS)
698 if (verify_use (bb, definition_block[SSA_NAME_VERSION (op)],
699 op, stmt, false, true,
700 names_defined_in_bb))
704 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
706 if (verify_use (bb, definition_block[SSA_NAME_VERSION (op)],
707 op, stmt, false, false,
708 names_defined_in_bb))
712 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_ALL_DEFS)
714 bitmap_set_bit (names_defined_in_bb, SSA_NAME_VERSION (op));
718 /* Verify the uses in arguments of PHI nodes at the exits from the
720 FOR_EACH_EDGE (e, ei, bb->succs)
722 for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
724 bool virtual = !is_gimple_reg (PHI_RESULT (phi));
725 op = PHI_ARG_DEF_FROM_EDGE (phi, e);
726 if (TREE_CODE (op) != SSA_NAME)
729 if (verify_use (bb, definition_block[SSA_NAME_VERSION (op)],
730 op, phi, false, virtual,
731 names_defined_in_bb))
736 bitmap_clear (names_defined_in_bb);
739 /* Finally, verify alias information. */
740 verify_alias_info ();
742 free (definition_block);
743 /* Restore the dominance information to its prior known state, so
744 that we do not perturb the compiler's subsequent behavior. */
745 if (orig_dom_state == DOM_NONE)
746 free_dominance_info (CDI_DOMINATORS);
748 dom_computed[CDI_DOMINATORS] = orig_dom_state;
750 BITMAP_XFREE (names_defined_in_bb);
751 timevar_pop (TV_TREE_SSA_VERIFY);
755 internal_error ("verify_ssa failed.");
759 /* Initialize global DFA and SSA structures. */
764 VARRAY_TREE_INIT (referenced_vars, 20, "referenced_vars");
765 call_clobbered_vars = BITMAP_XMALLOC ();
766 addressable_vars = BITMAP_XMALLOC ();
767 init_ssa_operands ();
770 global_var = NULL_TREE;
774 /* Deallocate memory associated with SSA data structures for FNDECL. */
777 delete_tree_ssa (void)
781 block_stmt_iterator bsi;
783 /* Remove annotations from every tree in the function. */
785 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
787 tree stmt = bsi_stmt (bsi);
789 ggc_free (stmt->common.ann);
790 stmt->common.ann = NULL;
793 /* Remove annotations from every referenced variable. */
796 for (i = 0; i < num_referenced_vars; i++)
798 tree var = referenced_var (i);
799 ggc_free (var->common.ann);
800 var->common.ann = NULL;
802 referenced_vars = NULL;
807 fini_ssa_operands ();
809 global_var = NULL_TREE;
810 BITMAP_XFREE (call_clobbered_vars);
811 call_clobbered_vars = NULL;
812 BITMAP_XFREE (addressable_vars);
813 addressable_vars = NULL;
817 /* Return true if EXPR is a useless type conversion, otherwise return
821 tree_ssa_useless_type_conversion_1 (tree outer_type, tree inner_type)
823 /* If the inner and outer types are effectively the same, then
824 strip the type conversion and enter the equivalence into
826 if (inner_type == outer_type
827 || (lang_hooks.types_compatible_p (inner_type, outer_type)))
830 /* If both types are pointers and the outer type is a (void *), then
831 the conversion is not necessary. The opposite is not true since
832 that conversion would result in a loss of information if the
833 equivalence was used. Consider an indirect function call where
834 we need to know the exact type of the function to correctly
835 implement the ABI. */
836 else if (POINTER_TYPE_P (inner_type)
837 && POINTER_TYPE_P (outer_type)
838 && TREE_CODE (TREE_TYPE (outer_type)) == VOID_TYPE)
841 /* Pointers and references are equivalent once we get to GENERIC,
842 so strip conversions that just switch between them. */
843 else if (POINTER_TYPE_P (inner_type)
844 && POINTER_TYPE_P (outer_type)
845 && lang_hooks.types_compatible_p (TREE_TYPE (inner_type),
846 TREE_TYPE (outer_type)))
849 /* If both the inner and outer types are integral types, then the
850 conversion is not necessary if they have the same mode and
851 signedness and precision, and both or neither are boolean. Some
852 code assumes an invariant that boolean types stay boolean and do
853 not become 1-bit bit-field types. Note that types with precision
854 not using all bits of the mode (such as bit-field types in C)
855 mean that testing of precision is necessary. */
856 else if (INTEGRAL_TYPE_P (inner_type)
857 && INTEGRAL_TYPE_P (outer_type)
858 && TYPE_MODE (inner_type) == TYPE_MODE (outer_type)
859 && TYPE_UNSIGNED (inner_type) == TYPE_UNSIGNED (outer_type)
860 && TYPE_PRECISION (inner_type) == TYPE_PRECISION (outer_type))
862 bool first_boolean = (TREE_CODE (inner_type) == BOOLEAN_TYPE);
863 bool second_boolean = (TREE_CODE (outer_type) == BOOLEAN_TYPE);
864 if (first_boolean == second_boolean)
868 /* Recurse for complex types. */
869 else if (TREE_CODE (inner_type) == COMPLEX_TYPE
870 && TREE_CODE (outer_type) == COMPLEX_TYPE
871 && tree_ssa_useless_type_conversion_1 (TREE_TYPE (outer_type),
872 TREE_TYPE (inner_type)))
878 /* Return true if EXPR is a useless type conversion, otherwise return
882 tree_ssa_useless_type_conversion (tree expr)
884 /* If we have an assignment that merely uses a NOP_EXPR to change
885 the top of the RHS to the type of the LHS and the type conversion
886 is "safe", then strip away the type conversion so that we can
887 enter LHS = RHS into the const_and_copies table. */
888 if (TREE_CODE (expr) == NOP_EXPR || TREE_CODE (expr) == CONVERT_EXPR
889 || TREE_CODE (expr) == VIEW_CONVERT_EXPR
890 || TREE_CODE (expr) == NON_LVALUE_EXPR)
891 return tree_ssa_useless_type_conversion_1 (TREE_TYPE (expr),
892 TREE_TYPE (TREE_OPERAND (expr,
900 /* Internal helper for walk_use_def_chains. VAR, FN and DATA are as
901 described in walk_use_def_chains.
903 VISITED is a bitmap used to mark visited SSA_NAMEs to avoid
906 IS_DFS is true if the caller wants to perform a depth-first search
907 when visiting PHI nodes. A DFS will visit each PHI argument and
908 call FN after each one. Otherwise, all the arguments are
909 visited first and then FN is called with each of the visited
910 arguments in a separate pass. */
913 walk_use_def_chains_1 (tree var, walk_use_def_chains_fn fn, void *data,
914 bitmap visited, bool is_dfs)
918 if (bitmap_bit_p (visited, SSA_NAME_VERSION (var)))
921 bitmap_set_bit (visited, SSA_NAME_VERSION (var));
923 def_stmt = SSA_NAME_DEF_STMT (var);
925 if (TREE_CODE (def_stmt) != PHI_NODE)
927 /* If we reached the end of the use-def chain, call FN. */
928 return fn (var, def_stmt, data);
934 /* When doing a breadth-first search, call FN before following the
935 use-def links for each argument. */
937 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
938 if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data))
941 /* Follow use-def links out of each PHI argument. */
942 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
944 tree arg = PHI_ARG_DEF (def_stmt, i);
945 if (TREE_CODE (arg) == SSA_NAME
946 && walk_use_def_chains_1 (arg, fn, data, visited, is_dfs))
950 /* When doing a depth-first search, call FN after following the
951 use-def links for each argument. */
953 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
954 if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data))
963 /* Walk use-def chains starting at the SSA variable VAR. Call
964 function FN at each reaching definition found. FN takes three
965 arguments: VAR, its defining statement (DEF_STMT) and a generic
966 pointer to whatever state information that FN may want to maintain
967 (DATA). FN is able to stop the walk by returning true, otherwise
968 in order to continue the walk, FN should return false.
970 Note, that if DEF_STMT is a PHI node, the semantics are slightly
971 different. The first argument to FN is no longer the original
972 variable VAR, but the PHI argument currently being examined. If FN
973 wants to get at VAR, it should call PHI_RESULT (PHI).
975 If IS_DFS is true, this function will:
977 1- walk the use-def chains for all the PHI arguments, and,
978 2- call (*FN) (ARG, PHI, DATA) on all the PHI arguments.
980 If IS_DFS is false, the two steps above are done in reverse order
981 (i.e., a breadth-first search). */
985 walk_use_def_chains (tree var, walk_use_def_chains_fn fn, void *data,
990 gcc_assert (TREE_CODE (var) == SSA_NAME);
992 def_stmt = SSA_NAME_DEF_STMT (var);
994 /* We only need to recurse if the reaching definition comes from a PHI
996 if (TREE_CODE (def_stmt) != PHI_NODE)
997 (*fn) (var, def_stmt, data);
1000 bitmap visited = BITMAP_XMALLOC ();
1001 walk_use_def_chains_1 (var, fn, data, visited, is_dfs);
1002 BITMAP_XFREE (visited);
1007 /* Replaces VAR with REPL in memory reference expression *X in
1011 propagate_into_addr (tree stmt, tree var, tree *x, tree repl)
1013 tree new_var, ass_stmt, addr_var;
1015 block_stmt_iterator bsi;
1017 /* There is nothing special to handle in the other cases. */
1018 if (TREE_CODE (repl) != ADDR_EXPR)
1020 addr_var = TREE_OPERAND (repl, 0);
1022 while (handled_component_p (*x)
1023 || TREE_CODE (*x) == REALPART_EXPR
1024 || TREE_CODE (*x) == IMAGPART_EXPR)
1025 x = &TREE_OPERAND (*x, 0);
1027 if (TREE_CODE (*x) != INDIRECT_REF
1028 || TREE_OPERAND (*x, 0) != var)
1031 if (TREE_TYPE (*x) == TREE_TYPE (addr_var))
1034 mark_new_vars_to_rename (stmt, vars_to_rename);
1039 /* Frontends sometimes produce expressions like *&a instead of a[0].
1040 Create a temporary variable to handle this case. */
1041 ass_stmt = build2 (MODIFY_EXPR, void_type_node, NULL_TREE, repl);
1042 new_var = duplicate_ssa_name (var, ass_stmt);
1043 TREE_OPERAND (*x, 0) = new_var;
1044 TREE_OPERAND (ass_stmt, 0) = new_var;
1046 bb = bb_for_stmt (stmt);
1047 tree_block_label (bb);
1048 bsi = bsi_after_labels (bb);
1049 bsi_insert_after (&bsi, ass_stmt, BSI_NEW_STMT);
1051 mark_new_vars_to_rename (stmt, vars_to_rename);
1054 /* Replaces immediate uses of VAR by REPL. */
1057 replace_immediate_uses (tree var, tree repl)
1064 use_operand_p use_p;
1066 df = get_immediate_uses (SSA_NAME_DEF_STMT (var));
1067 n = num_immediate_uses (df);
1069 for (i = 0; i < n; i++)
1071 stmt = immediate_use (df, i);
1073 if (TREE_CODE (stmt) == PHI_NODE)
1075 for (j = 0; j < PHI_NUM_ARGS (stmt); j++)
1076 if (PHI_ARG_DEF (stmt, j) == var)
1078 SET_PHI_ARG_DEF (stmt, j, repl);
1079 if (TREE_CODE (repl) == SSA_NAME
1080 && PHI_ARG_EDGE (stmt, j)->flags & EDGE_ABNORMAL)
1081 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (repl) = 1;
1087 get_stmt_operands (stmt);
1088 mark_new_vars = false;
1089 if (is_gimple_reg (SSA_NAME_VAR (var)))
1091 if (TREE_CODE (stmt) == MODIFY_EXPR)
1093 propagate_into_addr (stmt, var, &TREE_OPERAND (stmt, 0), repl);
1094 propagate_into_addr (stmt, var, &TREE_OPERAND (stmt, 1), repl);
1097 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
1098 if (USE_FROM_PTR (use_p) == var)
1100 propagate_value (use_p, repl);
1101 mark_new_vars = POINTER_TYPE_P (TREE_TYPE (repl));
1106 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter,
1107 SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS)
1108 if (USE_FROM_PTR (use_p) == var)
1109 propagate_value (use_p, repl);
1112 /* FIXME. If REPL is a constant, we need to fold STMT.
1113 However, fold_stmt wants a pointer to the statement, because
1114 it may happen that it needs to replace the whole statement
1115 with a new expression. Since the current def-use machinery
1116 does not return pointers to statements, we call fold_stmt
1117 with the address of a local temporary, if that call changes
1118 the temporary then we fallback on looking for a proper
1119 pointer to STMT by scanning STMT's basic block.
1121 Note that all this will become unnecessary soon. This
1122 pass is being replaced with a proper copy propagation pass
1123 for 4.1 (dnovillo, 2004-09-17). */
1124 if (TREE_CODE (repl) != SSA_NAME)
1130 block_stmt_iterator si = bsi_for_stmt (stmt);
1131 bsi_replace (&si, tmp, true);
1132 stmt = bsi_stmt (si);
1136 /* If REPL is a pointer, it may have different memory tags associated
1137 with it. For instance, VAR may have had a name tag while REPL
1138 only had a type tag. In these cases, the virtual operands (if
1139 any) in the statement will refer to different symbols which need
1142 mark_new_vars_to_rename (stmt, vars_to_rename);
1148 /* Gets the value VAR is equivalent to according to EQ_TO. */
1151 get_eq_name (tree *eq_to, tree var)
1156 while (TREE_CODE (val) == SSA_NAME)
1158 ver = SSA_NAME_VERSION (val);
1165 while (TREE_CODE (var) == SSA_NAME)
1167 ver = SSA_NAME_VERSION (var);
1178 /* Checks whether phi node PHI is redundant and if it is, records the ssa name
1179 its result is redundant to to EQ_TO array. */
1182 check_phi_redundancy (tree phi, tree *eq_to)
1184 tree val = NULL_TREE, def, res = PHI_RESULT (phi), stmt;
1185 unsigned i, ver = SSA_NAME_VERSION (res), n;
1188 /* It is unlikely that such large phi node would be redundant. */
1189 if (PHI_NUM_ARGS (phi) > 16)
1192 for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++)
1194 def = PHI_ARG_DEF (phi, i);
1196 if (TREE_CODE (def) == SSA_NAME)
1198 def = get_eq_name (eq_to, def);
1204 && !operand_equal_p (val, def, 0))
1210 /* At least one of the arguments should not be equal to the result, or
1211 something strange is happening. */
1214 if (get_eq_name (eq_to, res) == val)
1217 if (!may_propagate_copy (res, val))
1222 df = get_immediate_uses (SSA_NAME_DEF_STMT (res));
1223 n = num_immediate_uses (df);
1225 for (i = 0; i < n; i++)
1227 stmt = immediate_use (df, i);
1229 if (TREE_CODE (stmt) == PHI_NODE)
1230 check_phi_redundancy (stmt, eq_to);
1234 /* Removes redundant phi nodes.
1236 A redundant PHI node is a PHI node where all of its PHI arguments
1237 are the same value, excluding any PHI arguments which are the same
1240 A redundant PHI node is effectively a copy, so we forward copy propagate
1241 which removes all uses of the destination of the PHI node then
1242 finally we delete the redundant PHI node.
1244 Note that if we can not copy propagate the PHI node, then the PHI
1245 will not be removed. Thus we do not have to worry about dependencies
1246 between PHIs and the problems serializing PHIs into copies creates.
1248 The most important effect of this pass is to remove degenerate PHI
1249 nodes created by removing unreachable code. */
1252 kill_redundant_phi_nodes (void)
1255 unsigned i, old_num_ssa_names;
1257 tree phi, var, repl, stmt;
1259 /* The EQ_TO[VER] holds the value by that the ssa name VER should be
1260 replaced. If EQ_TO[VER] is ssa name and it is decided to replace it by
1261 other value, it may be necessary to follow the chain till the final value.
1262 We perform path shortening (replacing the entries of the EQ_TO array with
1263 heads of these chains) whenever we access the field to prevent quadratic
1264 complexity (probably would not occur in practice anyway, but let us play
1266 eq_to = xcalloc (num_ssa_names, sizeof (tree));
1268 /* We have had cases where computing immediate uses takes a
1269 significant amount of compile time. If we run into such
1270 problems here, we may want to only compute immediate uses for
1271 a subset of all the SSA_NAMEs instead of computing it for
1272 all of the SSA_NAMEs. */
1273 compute_immediate_uses (TDFA_USE_OPS | TDFA_USE_VOPS, NULL);
1274 old_num_ssa_names = num_ssa_names;
1278 for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi))
1280 var = PHI_RESULT (phi);
1281 check_phi_redundancy (phi, eq_to);
1285 /* Now propagate the values. */
1286 for (i = 0; i < old_num_ssa_names; i++)
1291 repl = get_eq_name (eq_to, ssa_name (i));
1292 if (repl != ssa_name (i))
1293 replace_immediate_uses (ssa_name (i), repl);
1296 /* And remove the dead phis. */
1297 for (i = 0; i < old_num_ssa_names; i++)
1302 repl = get_eq_name (eq_to, ssa_name (i));
1303 if (repl != ssa_name (i))
1305 stmt = SSA_NAME_DEF_STMT (ssa_name (i));
1306 remove_phi_node (stmt, NULL_TREE, bb_for_stmt (stmt));
1314 struct tree_opt_pass pass_redundant_phi =
1316 "redphi", /* name */
1318 kill_redundant_phi_nodes, /* execute */
1321 0, /* static_pass_number */
1323 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1324 0, /* properties_provided */
1325 0, /* properties_destroyed */
1326 0, /* todo_flags_start */
1327 TODO_dump_func | TODO_rename_vars
1328 | TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */
1332 /* Emit warnings for uninitialized variables. This is done in two passes.
1334 The first pass notices real uses of SSA names with default definitions.
1335 Such uses are unconditionally uninitialized, and we can be certain that
1336 such a use is a mistake. This pass is run before most optimizations,
1337 so that we catch as many as we can.
1339 The second pass follows PHI nodes to find uses that are potentially
1340 uninitialized. In this case we can't necessarily prove that the use
1341 is really uninitialized. This pass is run after most optimizations,
1342 so that we thread as many jumps and possible, and delete as much dead
1343 code as possible, in order to reduce false positives. We also look
1344 again for plain uninitialized variables, since optimization may have
1345 changed conditionally uninitialized to unconditionally uninitialized. */
1347 /* Emit a warning for T, an SSA_NAME, being uninitialized. The exact
1348 warning text is in MSGID and LOCUS may contain a location or be null. */
1351 warn_uninit (tree t, const char *msgid, location_t *locus)
1353 tree var = SSA_NAME_VAR (t);
1354 tree def = SSA_NAME_DEF_STMT (t);
1356 /* Default uses (indicated by an empty definition statement),
1357 are uninitialized. */
1358 if (!IS_EMPTY_STMT (def))
1361 /* Except for PARMs of course, which are always initialized. */
1362 if (TREE_CODE (var) == PARM_DECL)
1365 /* Hard register variables get their initial value from the ether. */
1366 if (TREE_CODE (var) == VAR_DECL && DECL_HARD_REGISTER (var))
1369 /* TREE_NO_WARNING either means we already warned, or the front end
1370 wishes to suppress the warning. */
1371 if (TREE_NO_WARNING (var))
1375 locus = &DECL_SOURCE_LOCATION (var);
1376 warning (msgid, locus, var);
1377 TREE_NO_WARNING (var) = 1;
1380 /* Called via walk_tree, look for SSA_NAMEs that have empty definitions
1381 and warn about them. */
1384 warn_uninitialized_var (tree *tp, int *walk_subtrees, void *data)
1386 location_t *locus = data;
1389 /* We only do data flow with SSA_NAMEs, so that's all we can warn about. */
1390 if (TREE_CODE (t) == SSA_NAME)
1392 warn_uninit (t, "%H'%D' is used uninitialized in this function", locus);
1395 else if (IS_TYPE_OR_DECL_P (t))
1401 /* Look for inputs to PHI that are SSA_NAMEs that have empty definitions
1402 and warn about them. */
1405 warn_uninitialized_phi (tree phi)
1407 int i, n = PHI_NUM_ARGS (phi);
1409 /* Don't look at memory tags. */
1410 if (!is_gimple_reg (PHI_RESULT (phi)))
1413 for (i = 0; i < n; ++i)
1415 tree op = PHI_ARG_DEF (phi, i);
1416 if (TREE_CODE (op) == SSA_NAME)
1417 warn_uninit (op, "%H'%D' may be used uninitialized in this function",
1423 execute_early_warn_uninitialized (void)
1425 block_stmt_iterator bsi;
1429 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
1430 walk_tree (bsi_stmt_ptr (bsi), warn_uninitialized_var,
1431 EXPR_LOCUS (bsi_stmt (bsi)), NULL);
1435 execute_late_warn_uninitialized (void)
1440 /* Re-do the plain uninitialized variable check, as optimization may have
1441 straightened control flow. Do this first so that we don't accidentally
1442 get a "may be" warning when we'd have seen an "is" warning later. */
1443 execute_early_warn_uninitialized ();
1446 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1447 warn_uninitialized_phi (phi);
1451 gate_warn_uninitialized (void)
1453 return warn_uninitialized != 0;
1456 struct tree_opt_pass pass_early_warn_uninitialized =
1459 gate_warn_uninitialized, /* gate */
1460 execute_early_warn_uninitialized, /* execute */
1463 0, /* static_pass_number */
1465 PROP_ssa, /* properties_required */
1466 0, /* properties_provided */
1467 0, /* properties_destroyed */
1468 0, /* todo_flags_start */
1469 0, /* todo_flags_finish */
1473 struct tree_opt_pass pass_late_warn_uninitialized =
1476 gate_warn_uninitialized, /* gate */
1477 execute_late_warn_uninitialized, /* execute */
1480 0, /* static_pass_number */
1482 PROP_ssa, /* properties_required */
1483 0, /* properties_provided */
1484 0, /* properties_destroyed */
1485 0, /* todo_flags_start */
1486 0, /* todo_flags_finish */