/* Miscellaneous SSA utility functions. Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "tree.h" #include "flags.h" #include "rtl.h" #include "tm_p.h" #include "ggc.h" #include "langhooks.h" #include "hard-reg-set.h" #include "basic-block.h" #include "output.h" #include "errors.h" #include "expr.h" #include "function.h" #include "diagnostic.h" #include "bitmap.h" #include "tree-flow.h" #include "tree-gimple.h" #include "tree-inline.h" #include "varray.h" #include "timevar.h" #include "hashtab.h" #include "tree-dump.h" #include "tree-pass.h" /* Remove edge E and remove the corresponding arguments from the PHI nodes in E's destination block. */ void ssa_remove_edge (edge e) { tree phi, next; /* Remove the appropriate PHI arguments in E's destination block. */ for (phi = phi_nodes (e->dest); phi; phi = next) { next = PHI_CHAIN (phi); remove_phi_arg (phi, e->src); } remove_edge (e); } /* Remove the corresponding arguments from the PHI nodes in E's destination block and redirect it to DEST. Return redirected edge. The list of removed arguments is stored in PENDING_STMT (e). */ edge ssa_redirect_edge (edge e, basic_block dest) { tree phi, next; tree list = NULL, *last = &list; tree src, dst, node; int i; /* Remove the appropriate PHI arguments in E's destination block. */ for (phi = phi_nodes (e->dest); phi; phi = next) { next = PHI_CHAIN (phi); i = phi_arg_from_edge (phi, e); if (i < 0) continue; src = PHI_ARG_DEF (phi, i); dst = PHI_RESULT (phi); node = build_tree_list (dst, src); *last = node; last = &TREE_CHAIN (node); remove_phi_arg_num (phi, i); } e = redirect_edge_succ_nodup (e, dest); PENDING_STMT (e) = list; return e; } /* Add PHI arguments queued in PENDINT_STMT list on edge E to edge E->dest. */ void flush_pending_stmts (edge e) { tree phi, arg; if (!PENDING_STMT (e)) return; for (phi = phi_nodes (e->dest), arg = PENDING_STMT (e); phi; phi = PHI_CHAIN (phi), arg = TREE_CHAIN (arg)) { tree def = TREE_VALUE (arg); add_phi_arg (&phi, def, e); } PENDING_STMT (e) = NULL; } /* Return true if SSA_NAME is malformed and mark it visited. IS_VIRTUAL is true if this SSA_NAME was found inside a virtual operand. */ static bool verify_ssa_name (tree ssa_name, bool is_virtual) { TREE_VISITED (ssa_name) = 1; if (TREE_CODE (ssa_name) != SSA_NAME) { error ("Expected an SSA_NAME object"); return true; } if (TREE_TYPE (ssa_name) != TREE_TYPE (SSA_NAME_VAR (ssa_name))) { error ("Type mismatch between an SSA_NAME and its symbol."); return true; } if (SSA_NAME_IN_FREE_LIST (ssa_name)) { error ("Found an SSA_NAME that had been released into the free pool"); return true; } if (is_virtual && is_gimple_reg (ssa_name)) { error ("Found a virtual definition for a GIMPLE register"); return true; } if (!is_virtual && !is_gimple_reg (ssa_name)) { error ("Found a real definition for a non-register"); return true; } return false; } /* Return true if the definition of SSA_NAME at block BB is malformed. STMT is the statement where SSA_NAME is created. DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME version numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set, it means that the block in that array slot contains the definition of SSA_NAME. IS_VIRTUAL is true if SSA_NAME is created by a V_MAY_DEF or a V_MUST_DEF. */ static bool verify_def (basic_block bb, basic_block *definition_block, tree ssa_name, tree stmt, bool is_virtual) { if (verify_ssa_name (ssa_name, is_virtual)) goto err; if (definition_block[SSA_NAME_VERSION (ssa_name)]) { error ("SSA_NAME created in two different blocks %i and %i", definition_block[SSA_NAME_VERSION (ssa_name)]->index, bb->index); goto err; } definition_block[SSA_NAME_VERSION (ssa_name)] = bb; if (SSA_NAME_DEF_STMT (ssa_name) != stmt) { error ("SSA_NAME_DEF_STMT is wrong"); fprintf (stderr, "Expected definition statement:\n"); print_generic_stmt (stderr, SSA_NAME_DEF_STMT (ssa_name), TDF_VOPS); fprintf (stderr, "\nActual definition statement:\n"); print_generic_stmt (stderr, stmt, TDF_VOPS); goto err; } return false; err: fprintf (stderr, "while verifying SSA_NAME "); print_generic_expr (stderr, ssa_name, 0); fprintf (stderr, " in statement\n"); print_generic_stmt (stderr, stmt, TDF_VOPS); return true; } /* Return true if the use of SSA_NAME at statement STMT in block BB is malformed. DEF_BB is the block where SSA_NAME was found to be created. IDOM contains immediate dominator information for the flowgraph. CHECK_ABNORMAL is true if the caller wants to check whether this use is flowing through an abnormal edge (only used when checking PHI arguments). IS_VIRTUAL is true if SSA_NAME is created by a V_MAY_DEF or a V_MUST_DEF. If NAMES_DEFINED_IN_BB is not NULL, it contains a bitmap of ssa names that are defined before STMT in basic block BB. */ static bool verify_use (basic_block bb, basic_block def_bb, tree ssa_name, tree stmt, bool check_abnormal, bool is_virtual, bitmap names_defined_in_bb) { bool err = false; err = verify_ssa_name (ssa_name, is_virtual); if (IS_EMPTY_STMT (SSA_NAME_DEF_STMT (ssa_name)) && var_ann (SSA_NAME_VAR (ssa_name))->default_def == ssa_name) ; /* Default definitions have empty statements. Nothing to do. */ else if (!def_bb) { error ("Missing definition"); err = true; } else if (bb != def_bb && !dominated_by_p (CDI_DOMINATORS, bb, def_bb)) { error ("Definition in block %i does not dominate use in block %i", def_bb->index, bb->index); err = true; } else if (bb == def_bb && names_defined_in_bb != NULL && !bitmap_bit_p (names_defined_in_bb, SSA_NAME_VERSION (ssa_name))) { error ("Definition in block %i follows the use", def_bb->index); err = true; } if (check_abnormal && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (ssa_name)) { error ("SSA_NAME_OCCURS_IN_ABNORMAL_PHI should be set"); err = true; } if (err) { fprintf (stderr, "for SSA_NAME: "); print_generic_expr (stderr, ssa_name, TDF_VOPS); fprintf (stderr, "in statement:\n"); print_generic_stmt (stderr, stmt, TDF_VOPS); } return err; } /* Return true if any of the arguments for PHI node PHI at block BB is malformed. IDOM contains immediate dominator information for the flowgraph. DEFINITION_BLOCK is an array of basic blocks indexed by SSA_NAME version numbers. If DEFINITION_BLOCK[SSA_NAME_VERSION] is set, it means that the block in that array slot contains the definition of SSA_NAME. */ static bool verify_phi_args (tree phi, basic_block bb, basic_block *definition_block) { edge e; bool err = false; int i, phi_num_args = PHI_NUM_ARGS (phi); edge_iterator ei; /* Mark all the incoming edges. */ FOR_EACH_EDGE (e, ei, bb->preds) e->aux = (void *) 1; for (i = 0; i < phi_num_args; i++) { tree op = PHI_ARG_DEF (phi, i); e = PHI_ARG_EDGE (phi, i); if (TREE_CODE (op) == SSA_NAME) err = verify_use (e->src, definition_block[SSA_NAME_VERSION (op)], op, phi, e->flags & EDGE_ABNORMAL, !is_gimple_reg (PHI_RESULT (phi)), NULL); if (e->dest != bb) { error ("Wrong edge %d->%d for PHI argument\n", e->src->index, e->dest->index, bb->index); err = true; } if (e->aux == (void *) 0) { error ("PHI argument flowing through dead edge %d->%d\n", e->src->index, e->dest->index); err = true; } if (e->aux == (void *) 2) { error ("PHI argument duplicated for edge %d->%d\n", e->src->index, e->dest->index); err = true; } if (err) { fprintf (stderr, "PHI argument\n"); print_generic_stmt (stderr, op, TDF_VOPS); goto error; } e->aux = (void *) 2; } FOR_EACH_EDGE (e, ei, bb->preds) { if (e->aux != (void *) 2) { error ("No argument flowing through edge %d->%d\n", e->src->index, e->dest->index); err = true; goto error; } e->aux = (void *) 0; } error: if (err) { fprintf (stderr, "for PHI node\n"); print_generic_stmt (stderr, phi, TDF_VOPS); } return err; } static void verify_flow_insensitive_alias_info (void) { size_t i; tree var; bitmap visited = BITMAP_XMALLOC (); for (i = 0; i < num_referenced_vars; i++) { size_t j; var_ann_t ann; varray_type may_aliases; var = referenced_var (i); ann = var_ann (var); may_aliases = ann->may_aliases; for (j = 0; may_aliases && j < VARRAY_ACTIVE_SIZE (may_aliases); j++) { tree alias = VARRAY_TREE (may_aliases, j); bitmap_set_bit (visited, var_ann (alias)->uid); if (!may_be_aliased (alias)) { error ("Non-addressable variable inside an alias set."); debug_variable (alias); goto err; } } } for (i = 0; i < num_referenced_vars; i++) { var_ann_t ann; var = referenced_var (i); ann = var_ann (var); if (ann->mem_tag_kind == NOT_A_TAG && ann->is_alias_tag && !bitmap_bit_p (visited, ann->uid)) { error ("Addressable variable that is an alias tag but is not in any alias set."); goto err; } } BITMAP_XFREE (visited); return; err: debug_variable (var); internal_error ("verify_flow_insensitive_alias_info failed."); } static void verify_flow_sensitive_alias_info (void) { size_t i; tree ptr; for (i = 1; i < num_ssa_names; i++) { var_ann_t ann; struct ptr_info_def *pi; ptr = ssa_name (i); if (!ptr) continue; ann = var_ann (SSA_NAME_VAR (ptr)); pi = SSA_NAME_PTR_INFO (ptr); /* We only care for pointers that are actually referenced in the program. */ if (!TREE_VISITED (ptr) || !POINTER_TYPE_P (TREE_TYPE (ptr))) continue; /* RESULT_DECL is special. If it's a GIMPLE register, then it is only written-to only once in the return statement. Otherwise, aggregate RESULT_DECLs may be written-to more than once in virtual operands. */ if (TREE_CODE (SSA_NAME_VAR (ptr)) == RESULT_DECL && is_gimple_reg (ptr)) continue; if (pi == NULL) continue; if (pi->is_dereferenced && !pi->name_mem_tag && !ann->type_mem_tag) { error ("Dereferenced pointers should have a name or a type tag"); goto err; } if (pi->name_mem_tag && !pi->pt_malloc && (pi->pt_vars == NULL || bitmap_empty_p (pi->pt_vars))) { error ("Pointers with a memory tag, should have points-to sets or point to malloc"); goto err; } if (pi->value_escapes_p && pi->name_mem_tag && !is_call_clobbered (pi->name_mem_tag)) { error ("Pointer escapes but its name tag is not call-clobbered."); goto err; } } return; err: debug_variable (ptr); internal_error ("verify_flow_sensitive_alias_info failed."); } DEF_VEC_MALLOC_P (bitmap); /* Verify that all name tags have different points to sets. This algorithm takes advantage of the fact that every variable with the same name tag must have the same points-to set. So we check a single variable for each name tag, and verify that its points-to set is different from every other points-to set for other name tags. */ static void verify_name_tags (void) { size_t i; size_t j; bitmap first, second; VEC (tree) *name_tag_reps = NULL; VEC (bitmap) *pt_vars_for_reps = NULL; /* First we compute the name tag representatives and their points-to sets. */ for (i = 0; i < num_ssa_names; i++) { if (ssa_name (i)) { tree ptr = ssa_name (i); struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); if (!TREE_VISITED (ptr) || !POINTER_TYPE_P (TREE_TYPE (ptr)) || !pi || !pi->name_mem_tag || TREE_VISITED (pi->name_mem_tag)) continue; TREE_VISITED (pi->name_mem_tag) = 1; if (pi->pt_vars != NULL) { VEC_safe_push (tree, name_tag_reps, ptr); VEC_safe_push (bitmap, pt_vars_for_reps, pi->pt_vars); } } } /* Now compare all the representative bitmaps with all other representative bitmaps, to verify that they are all different. */ for (i = 0; VEC_iterate (bitmap, pt_vars_for_reps, i, first); i++) { for (j = i + 1; VEC_iterate (bitmap, pt_vars_for_reps, j, second); j++) { if (bitmap_equal_p (first, second)) { error ("Two different pointers with identical points-to sets but different name tags"); debug_variable (VEC_index (tree, name_tag_reps, j)); goto err; } } } /* Lastly, clear out the visited flags. */ for (i = 0; i < num_ssa_names; i++) { if (ssa_name (i)) { tree ptr = ssa_name (i); struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); if (!TREE_VISITED (ptr) || !POINTER_TYPE_P (TREE_TYPE (ptr)) || !pi || !pi->name_mem_tag) continue; TREE_VISITED (pi->name_mem_tag) = 0; } } VEC_free (bitmap, pt_vars_for_reps); return; err: debug_variable (VEC_index (tree, name_tag_reps, i)); internal_error ("verify_name_tags failed"); } /* Verify the consistency of aliasing information. */ static void verify_alias_info (void) { verify_flow_sensitive_alias_info (); verify_name_tags (); verify_flow_insensitive_alias_info (); } /* Verify common invariants in the SSA web. TODO: verify the variable annotations. */ void verify_ssa (void) { size_t i; basic_block bb; basic_block *definition_block = xcalloc (num_ssa_names, sizeof (basic_block)); ssa_op_iter iter; tree op; enum dom_state orig_dom_state = dom_computed[CDI_DOMINATORS]; bitmap names_defined_in_bb = BITMAP_XMALLOC (); timevar_push (TV_TREE_SSA_VERIFY); /* Keep track of SSA names present in the IL. */ for (i = 1; i < num_ssa_names; i++) if (ssa_name (i)) TREE_VISITED (ssa_name (i)) = 0; calculate_dominance_info (CDI_DOMINATORS); /* Verify and register all the SSA_NAME definitions found in the function. */ FOR_EACH_BB (bb) { tree phi; block_stmt_iterator bsi; for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) { int i; if (verify_def (bb, definition_block, PHI_RESULT (phi), phi, !is_gimple_reg (PHI_RESULT (phi)))) goto err; for (i = 0; i < PHI_NUM_ARGS (phi); i++) { tree def = PHI_ARG_DEF (phi, i); if (TREE_CODE (def) != SSA_NAME && !is_gimple_min_invariant (def)) { error ("PHI argument is not SSA_NAME, or invariant"); print_generic_stmt (stderr, phi, TDF_VOPS); goto err; } } } for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt; stmt = bsi_stmt (bsi); get_stmt_operands (stmt); if (stmt_ann (stmt)->makes_aliased_stores && NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0) { error ("Statement makes aliased stores, but has no V_MAY_DEFS"); print_generic_stmt (stderr, stmt, TDF_VOPS); goto err; } FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS) { if (verify_def (bb, definition_block, op, stmt, true)) goto err; } FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF) { if (verify_def (bb, definition_block, op, stmt, false)) goto err; } } } /* Now verify all the uses and make sure they agree with the definitions found in the previous pass. */ FOR_EACH_BB (bb) { edge e; tree phi; edge_iterator ei; block_stmt_iterator bsi; /* Make sure that all edges have a clear 'aux' field. */ FOR_EACH_EDGE (e, ei, bb->preds) { if (e->aux) { error ("AUX pointer initialized for edge %d->%d\n", e->src->index, e->dest->index); goto err; } } /* Verify the arguments for every PHI node in the block. */ for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) { if (verify_phi_args (phi, bb, definition_block)) goto err; bitmap_set_bit (names_defined_in_bb, SSA_NAME_VERSION (PHI_RESULT (phi))); } /* Now verify all the uses and vuses in every statement of the block. */ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt = bsi_stmt (bsi); FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS) { if (verify_use (bb, definition_block[SSA_NAME_VERSION (op)], op, stmt, false, true, names_defined_in_bb)) goto err; } FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE) { if (verify_use (bb, definition_block[SSA_NAME_VERSION (op)], op, stmt, false, false, names_defined_in_bb)) goto err; } FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_ALL_DEFS) { bitmap_set_bit (names_defined_in_bb, SSA_NAME_VERSION (op)); } } /* Verify the uses in arguments of PHI nodes at the exits from the block. */ FOR_EACH_EDGE (e, ei, bb->succs) { for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi)) { bool virtual = !is_gimple_reg (PHI_RESULT (phi)); op = PHI_ARG_DEF_FROM_EDGE (phi, e); if (TREE_CODE (op) != SSA_NAME) continue; if (verify_use (bb, definition_block[SSA_NAME_VERSION (op)], op, phi, false, virtual, names_defined_in_bb)) goto err; } } bitmap_clear (names_defined_in_bb); } /* Finally, verify alias information. */ verify_alias_info (); free (definition_block); /* Restore the dominance information to its prior known state, so that we do not perturb the compiler's subsequent behavior. */ if (orig_dom_state == DOM_NONE) free_dominance_info (CDI_DOMINATORS); else dom_computed[CDI_DOMINATORS] = orig_dom_state; BITMAP_XFREE (names_defined_in_bb); timevar_pop (TV_TREE_SSA_VERIFY); return; err: internal_error ("verify_ssa failed."); } /* Initialize global DFA and SSA structures. */ void init_tree_ssa (void) { VARRAY_TREE_INIT (referenced_vars, 20, "referenced_vars"); call_clobbered_vars = BITMAP_XMALLOC (); addressable_vars = BITMAP_XMALLOC (); init_ssa_operands (); init_ssanames (); init_phinodes (); global_var = NULL_TREE; } /* Deallocate memory associated with SSA data structures for FNDECL. */ void delete_tree_ssa (void) { size_t i; basic_block bb; block_stmt_iterator bsi; /* Remove annotations from every tree in the function. */ FOR_EACH_BB (bb) for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt = bsi_stmt (bsi); release_defs (stmt); ggc_free (stmt->common.ann); stmt->common.ann = NULL; } /* Remove annotations from every referenced variable. */ if (referenced_vars) { for (i = 0; i < num_referenced_vars; i++) { tree var = referenced_var (i); ggc_free (var->common.ann); var->common.ann = NULL; } referenced_vars = NULL; } fini_ssanames (); fini_phinodes (); fini_ssa_operands (); global_var = NULL_TREE; BITMAP_XFREE (call_clobbered_vars); call_clobbered_vars = NULL; BITMAP_XFREE (addressable_vars); addressable_vars = NULL; } /* Return true if EXPR is a useless type conversion, otherwise return false. */ bool tree_ssa_useless_type_conversion_1 (tree outer_type, tree inner_type) { /* If the inner and outer types are effectively the same, then strip the type conversion and enter the equivalence into the table. */ if (inner_type == outer_type || (lang_hooks.types_compatible_p (inner_type, outer_type))) return true; /* If both types are pointers and the outer type is a (void *), then the conversion is not necessary. The opposite is not true since that conversion would result in a loss of information if the equivalence was used. Consider an indirect function call where we need to know the exact type of the function to correctly implement the ABI. */ else if (POINTER_TYPE_P (inner_type) && POINTER_TYPE_P (outer_type) && TYPE_MODE (inner_type) == TYPE_MODE (outer_type) && TYPE_REF_CAN_ALIAS_ALL (inner_type) == TYPE_REF_CAN_ALIAS_ALL (outer_type) && TREE_CODE (TREE_TYPE (outer_type)) == VOID_TYPE) return true; /* Pointers and references are equivalent once we get to GENERIC, so strip conversions that just switch between them. */ else if (POINTER_TYPE_P (inner_type) && POINTER_TYPE_P (outer_type) && TYPE_MODE (inner_type) == TYPE_MODE (outer_type) && TYPE_REF_CAN_ALIAS_ALL (inner_type) == TYPE_REF_CAN_ALIAS_ALL (outer_type) && lang_hooks.types_compatible_p (TREE_TYPE (inner_type), TREE_TYPE (outer_type))) return true; /* If both the inner and outer types are integral types, then the conversion is not necessary if they have the same mode and signedness and precision, and both or neither are boolean. Some code assumes an invariant that boolean types stay boolean and do not become 1-bit bit-field types. Note that types with precision not using all bits of the mode (such as bit-field types in C) mean that testing of precision is necessary. */ else if (INTEGRAL_TYPE_P (inner_type) && INTEGRAL_TYPE_P (outer_type) && TYPE_MODE (inner_type) == TYPE_MODE (outer_type) && TYPE_UNSIGNED (inner_type) == TYPE_UNSIGNED (outer_type) && TYPE_PRECISION (inner_type) == TYPE_PRECISION (outer_type)) { bool first_boolean = (TREE_CODE (inner_type) == BOOLEAN_TYPE); bool second_boolean = (TREE_CODE (outer_type) == BOOLEAN_TYPE); if (first_boolean == second_boolean) return true; } /* Recurse for complex types. */ else if (TREE_CODE (inner_type) == COMPLEX_TYPE && TREE_CODE (outer_type) == COMPLEX_TYPE && tree_ssa_useless_type_conversion_1 (TREE_TYPE (outer_type), TREE_TYPE (inner_type))) return true; return false; } /* Return true if EXPR is a useless type conversion, otherwise return false. */ bool tree_ssa_useless_type_conversion (tree expr) { /* If we have an assignment that merely uses a NOP_EXPR to change the top of the RHS to the type of the LHS and the type conversion is "safe", then strip away the type conversion so that we can enter LHS = RHS into the const_and_copies table. */ if (TREE_CODE (expr) == NOP_EXPR || TREE_CODE (expr) == CONVERT_EXPR || TREE_CODE (expr) == VIEW_CONVERT_EXPR || TREE_CODE (expr) == NON_LVALUE_EXPR) return tree_ssa_useless_type_conversion_1 (TREE_TYPE (expr), TREE_TYPE (TREE_OPERAND (expr, 0))); return false; } /* Internal helper for walk_use_def_chains. VAR, FN and DATA are as described in walk_use_def_chains. VISITED is a bitmap used to mark visited SSA_NAMEs to avoid infinite loops. IS_DFS is true if the caller wants to perform a depth-first search when visiting PHI nodes. A DFS will visit each PHI argument and call FN after each one. Otherwise, all the arguments are visited first and then FN is called with each of the visited arguments in a separate pass. */ static bool walk_use_def_chains_1 (tree var, walk_use_def_chains_fn fn, void *data, bitmap visited, bool is_dfs) { tree def_stmt; if (bitmap_bit_p (visited, SSA_NAME_VERSION (var))) return false; bitmap_set_bit (visited, SSA_NAME_VERSION (var)); def_stmt = SSA_NAME_DEF_STMT (var); if (TREE_CODE (def_stmt) != PHI_NODE) { /* If we reached the end of the use-def chain, call FN. */ return fn (var, def_stmt, data); } else { int i; /* When doing a breadth-first search, call FN before following the use-def links for each argument. */ if (!is_dfs) for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++) if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data)) return true; /* Follow use-def links out of each PHI argument. */ for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++) { tree arg = PHI_ARG_DEF (def_stmt, i); if (TREE_CODE (arg) == SSA_NAME && walk_use_def_chains_1 (arg, fn, data, visited, is_dfs)) return true; } /* When doing a depth-first search, call FN after following the use-def links for each argument. */ if (is_dfs) for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++) if (fn (PHI_ARG_DEF (def_stmt, i), def_stmt, data)) return true; } return false; } /* Walk use-def chains starting at the SSA variable VAR. Call function FN at each reaching definition found. FN takes three arguments: VAR, its defining statement (DEF_STMT) and a generic pointer to whatever state information that FN may want to maintain (DATA). FN is able to stop the walk by returning true, otherwise in order to continue the walk, FN should return false. Note, that if DEF_STMT is a PHI node, the semantics are slightly different. The first argument to FN is no longer the original variable VAR, but the PHI argument currently being examined. If FN wants to get at VAR, it should call PHI_RESULT (PHI). If IS_DFS is true, this function will: 1- walk the use-def chains for all the PHI arguments, and, 2- call (*FN) (ARG, PHI, DATA) on all the PHI arguments. If IS_DFS is false, the two steps above are done in reverse order (i.e., a breadth-first search). */ void walk_use_def_chains (tree var, walk_use_def_chains_fn fn, void *data, bool is_dfs) { tree def_stmt; gcc_assert (TREE_CODE (var) == SSA_NAME); def_stmt = SSA_NAME_DEF_STMT (var); /* We only need to recurse if the reaching definition comes from a PHI node. */ if (TREE_CODE (def_stmt) != PHI_NODE) (*fn) (var, def_stmt, data); else { bitmap visited = BITMAP_XMALLOC (); walk_use_def_chains_1 (var, fn, data, visited, is_dfs); BITMAP_XFREE (visited); } } /* Replaces VAR with REPL in memory reference expression *X in statement STMT. */ static void propagate_into_addr (tree stmt, tree var, tree *x, tree repl) { tree new_var, ass_stmt, addr_var; basic_block bb; block_stmt_iterator bsi; /* There is nothing special to handle in the other cases. */ if (TREE_CODE (repl) != ADDR_EXPR) return; addr_var = TREE_OPERAND (repl, 0); while (handled_component_p (*x) || TREE_CODE (*x) == REALPART_EXPR || TREE_CODE (*x) == IMAGPART_EXPR) x = &TREE_OPERAND (*x, 0); if (TREE_CODE (*x) != INDIRECT_REF || TREE_OPERAND (*x, 0) != var) return; if (TREE_TYPE (*x) == TREE_TYPE (addr_var)) { *x = addr_var; mark_new_vars_to_rename (stmt, vars_to_rename); return; } /* Frontends sometimes produce expressions like *&a instead of a[0]. Create a temporary variable to handle this case. */ ass_stmt = build2 (MODIFY_EXPR, void_type_node, NULL_TREE, repl); new_var = duplicate_ssa_name (var, ass_stmt); TREE_OPERAND (*x, 0) = new_var; TREE_OPERAND (ass_stmt, 0) = new_var; bb = bb_for_stmt (stmt); tree_block_label (bb); bsi = bsi_after_labels (bb); bsi_insert_after (&bsi, ass_stmt, BSI_NEW_STMT); mark_new_vars_to_rename (stmt, vars_to_rename); } /* Replaces immediate uses of VAR by REPL. */ static void replace_immediate_uses (tree var, tree repl) { int i, j, n; dataflow_t df; tree stmt; bool mark_new_vars; ssa_op_iter iter; use_operand_p use_p; df = get_immediate_uses (SSA_NAME_DEF_STMT (var)); n = num_immediate_uses (df); for (i = 0; i < n; i++) { stmt = immediate_use (df, i); if (TREE_CODE (stmt) == PHI_NODE) { for (j = 0; j < PHI_NUM_ARGS (stmt); j++) if (PHI_ARG_DEF (stmt, j) == var) { SET_PHI_ARG_DEF (stmt, j, repl); if (TREE_CODE (repl) == SSA_NAME && PHI_ARG_EDGE (stmt, j)->flags & EDGE_ABNORMAL) SSA_NAME_OCCURS_IN_ABNORMAL_PHI (repl) = 1; } continue; } get_stmt_operands (stmt); mark_new_vars = false; if (is_gimple_reg (SSA_NAME_VAR (var))) { if (TREE_CODE (stmt) == MODIFY_EXPR) { propagate_into_addr (stmt, var, &TREE_OPERAND (stmt, 0), repl); propagate_into_addr (stmt, var, &TREE_OPERAND (stmt, 1), repl); } FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE) if (USE_FROM_PTR (use_p) == var) { propagate_value (use_p, repl); mark_new_vars = POINTER_TYPE_P (TREE_TYPE (repl)); } } else { FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS) if (USE_FROM_PTR (use_p) == var) propagate_value (use_p, repl); } /* FIXME. If REPL is a constant, we need to fold STMT. However, fold_stmt wants a pointer to the statement, because it may happen that it needs to replace the whole statement with a new expression. Since the current def-use machinery does not return pointers to statements, we call fold_stmt with the address of a local temporary, if that call changes the temporary then we fallback on looking for a proper pointer to STMT by scanning STMT's basic block. Note that all this will become unnecessary soon. This pass is being replaced with a proper copy propagation pass for 4.1 (dnovillo, 2004-09-17). */ if (TREE_CODE (repl) != SSA_NAME) { tree tmp = stmt; fold_stmt (&tmp); mark_new_vars = true; if (tmp != stmt) { block_stmt_iterator si = bsi_for_stmt (stmt); bsi_replace (&si, tmp, true); stmt = bsi_stmt (si); } } /* If REPL is a pointer, it may have different memory tags associated with it. For instance, VAR may have had a name tag while REPL only had a type tag. In these cases, the virtual operands (if any) in the statement will refer to different symbols which need to be renamed. */ if (mark_new_vars) mark_new_vars_to_rename (stmt, vars_to_rename); else modify_stmt (stmt); } } /* Gets the value VAR is equivalent to according to EQ_TO. */ static tree get_eq_name (tree *eq_to, tree var) { unsigned ver; tree val = var; while (TREE_CODE (val) == SSA_NAME) { ver = SSA_NAME_VERSION (val); if (!eq_to[ver]) break; val = eq_to[ver]; } while (TREE_CODE (var) == SSA_NAME) { ver = SSA_NAME_VERSION (var); if (!eq_to[ver]) break; var = eq_to[ver]; eq_to[ver] = val; } return val; } /* Checks whether phi node PHI is redundant and if it is, records the ssa name its result is redundant to to EQ_TO array. */ static void check_phi_redundancy (tree phi, tree *eq_to) { tree val = NULL_TREE, def, res = PHI_RESULT (phi), stmt; unsigned i, ver = SSA_NAME_VERSION (res), n; dataflow_t df; /* It is unlikely that such large phi node would be redundant. */ if (PHI_NUM_ARGS (phi) > 16) return; for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++) { def = PHI_ARG_DEF (phi, i); if (TREE_CODE (def) == SSA_NAME) { def = get_eq_name (eq_to, def); if (def == res) continue; } if (val && !operand_equal_p (val, def, 0)) return; val = def; } /* At least one of the arguments should not be equal to the result, or something strange is happening. */ gcc_assert (val); if (get_eq_name (eq_to, res) == val) return; if (!may_propagate_copy (res, val)) return; eq_to[ver] = val; df = get_immediate_uses (SSA_NAME_DEF_STMT (res)); n = num_immediate_uses (df); for (i = 0; i < n; i++) { stmt = immediate_use (df, i); if (TREE_CODE (stmt) == PHI_NODE) check_phi_redundancy (stmt, eq_to); } } /* Removes redundant phi nodes. A redundant PHI node is a PHI node where all of its PHI arguments are the same value, excluding any PHI arguments which are the same as the PHI result. A redundant PHI node is effectively a copy, so we forward copy propagate which removes all uses of the destination of the PHI node then finally we delete the redundant PHI node. Note that if we can not copy propagate the PHI node, then the PHI will not be removed. Thus we do not have to worry about dependencies between PHIs and the problems serializing PHIs into copies creates. The most important effect of this pass is to remove degenerate PHI nodes created by removing unreachable code. */ void kill_redundant_phi_nodes (void) { tree *eq_to; unsigned i, old_num_ssa_names; basic_block bb; tree phi, var, repl, stmt; /* The EQ_TO[VER] holds the value by that the ssa name VER should be replaced. If EQ_TO[VER] is ssa name and it is decided to replace it by other value, it may be necessary to follow the chain till the final value. We perform path shortening (replacing the entries of the EQ_TO array with heads of these chains) whenever we access the field to prevent quadratic complexity (probably would not occur in practice anyway, but let us play it safe). */ eq_to = xcalloc (num_ssa_names, sizeof (tree)); /* We have had cases where computing immediate uses takes a significant amount of compile time. If we run into such problems here, we may want to only compute immediate uses for a subset of all the SSA_NAMEs instead of computing it for all of the SSA_NAMEs. */ compute_immediate_uses (TDFA_USE_OPS | TDFA_USE_VOPS, NULL); old_num_ssa_names = num_ssa_names; FOR_EACH_BB (bb) { for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) { var = PHI_RESULT (phi); check_phi_redundancy (phi, eq_to); } } /* Now propagate the values. */ for (i = 0; i < old_num_ssa_names; i++) { if (!ssa_name (i)) continue; repl = get_eq_name (eq_to, ssa_name (i)); if (repl != ssa_name (i)) replace_immediate_uses (ssa_name (i), repl); } /* And remove the dead phis. */ for (i = 0; i < old_num_ssa_names; i++) { if (!ssa_name (i)) continue; repl = get_eq_name (eq_to, ssa_name (i)); if (repl != ssa_name (i)) { stmt = SSA_NAME_DEF_STMT (ssa_name (i)); remove_phi_node (stmt, NULL_TREE, bb_for_stmt (stmt)); } } free_df (); free (eq_to); } struct tree_opt_pass pass_redundant_phi = { "redphi", /* name */ NULL, /* gate */ kill_redundant_phi_nodes, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ 0, /* tv_id */ PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_dump_func | TODO_rename_vars | TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */ 0 /* letter */ }; /* Emit warnings for uninitialized variables. This is done in two passes. The first pass notices real uses of SSA names with default definitions. Such uses are unconditionally uninitialized, and we can be certain that such a use is a mistake. This pass is run before most optimizations, so that we catch as many as we can. The second pass follows PHI nodes to find uses that are potentially uninitialized. In this case we can't necessarily prove that the use is really uninitialized. This pass is run after most optimizations, so that we thread as many jumps and possible, and delete as much dead code as possible, in order to reduce false positives. We also look again for plain uninitialized variables, since optimization may have changed conditionally uninitialized to unconditionally uninitialized. */ /* Emit a warning for T, an SSA_NAME, being uninitialized. The exact warning text is in MSGID and LOCUS may contain a location or be null. */ static void warn_uninit (tree t, const char *msgid, location_t *locus) { tree var = SSA_NAME_VAR (t); tree def = SSA_NAME_DEF_STMT (t); /* Default uses (indicated by an empty definition statement), are uninitialized. */ if (!IS_EMPTY_STMT (def)) return; /* Except for PARMs of course, which are always initialized. */ if (TREE_CODE (var) == PARM_DECL) return; /* Hard register variables get their initial value from the ether. */ if (TREE_CODE (var) == VAR_DECL && DECL_HARD_REGISTER (var)) return; /* TREE_NO_WARNING either means we already warned, or the front end wishes to suppress the warning. */ if (TREE_NO_WARNING (var)) return; if (!locus) locus = &DECL_SOURCE_LOCATION (var); warning (msgid, locus, var); TREE_NO_WARNING (var) = 1; } /* Called via walk_tree, look for SSA_NAMEs that have empty definitions and warn about them. */ static tree warn_uninitialized_var (tree *tp, int *walk_subtrees, void *data) { location_t *locus = data; tree t = *tp; /* We only do data flow with SSA_NAMEs, so that's all we can warn about. */ if (TREE_CODE (t) == SSA_NAME) { warn_uninit (t, "%H%qD is used uninitialized in this function", locus); *walk_subtrees = 0; } else if (IS_TYPE_OR_DECL_P (t)) *walk_subtrees = 0; return NULL_TREE; } /* Look for inputs to PHI that are SSA_NAMEs that have empty definitions and warn about them. */ static void warn_uninitialized_phi (tree phi) { int i, n = PHI_NUM_ARGS (phi); /* Don't look at memory tags. */ if (!is_gimple_reg (PHI_RESULT (phi))) return; for (i = 0; i < n; ++i) { tree op = PHI_ARG_DEF (phi, i); if (TREE_CODE (op) == SSA_NAME) warn_uninit (op, "%H%qD may be used uninitialized in this function", NULL); } } static void execute_early_warn_uninitialized (void) { block_stmt_iterator bsi; basic_block bb; FOR_EACH_BB (bb) for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) walk_tree (bsi_stmt_ptr (bsi), warn_uninitialized_var, EXPR_LOCUS (bsi_stmt (bsi)), NULL); } static void execute_late_warn_uninitialized (void) { basic_block bb; tree phi; /* Re-do the plain uninitialized variable check, as optimization may have straightened control flow. Do this first so that we don't accidentally get a "may be" warning when we'd have seen an "is" warning later. */ execute_early_warn_uninitialized (); FOR_EACH_BB (bb) for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) warn_uninitialized_phi (phi); } static bool gate_warn_uninitialized (void) { return warn_uninitialized != 0; } struct tree_opt_pass pass_early_warn_uninitialized = { NULL, /* name */ gate_warn_uninitialized, /* gate */ execute_early_warn_uninitialized, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ 0, /* tv_id */ PROP_ssa, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ 0, /* todo_flags_finish */ 0 /* letter */ }; struct tree_opt_pass pass_late_warn_uninitialized = { NULL, /* name */ gate_warn_uninitialized, /* gate */ execute_late_warn_uninitialized, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ 0, /* tv_id */ PROP_ssa, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ 0, /* todo_flags_finish */ 0 /* letter */ };