/* 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-simple.h" #include "tree-inline.h" #include "varray.h" #include "timevar.h" #include "tree-alias-common.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; /* Remove the appropriate PHI arguments in E's destination block. */ for (phi = phi_nodes (e->dest); phi; phi = TREE_CHAIN (phi)) remove_phi_arg (phi, e->src); remove_edge (e); } /* Remove 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; 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 = TREE_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; } /* 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. */ static bool verify_def (basic_block bb, basic_block *definition_block, tree ssa_name, tree stmt) { bool err = false; if (TREE_CODE (ssa_name) != SSA_NAME) { error ("Expected an SSA_NAME object"); debug_generic_stmt (ssa_name); debug_generic_stmt (stmt); } 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); fprintf (stderr, "SSA_NAME: "); debug_generic_stmt (ssa_name); debug_generic_stmt (stmt); err = true; } 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, "SSA_NAME: "); debug_generic_stmt (ssa_name); fprintf (stderr, "Expected definition statement:\n"); debug_generic_stmt (SSA_NAME_DEF_STMT (ssa_name)); fprintf (stderr, "\nActual definition statement:\n"); debug_generic_stmt (stmt); err = true; } return err; } /* 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). */ static bool verify_use (basic_block bb, basic_block def_bb, tree ssa_name, tree stmt, bool check_abnormal) { bool err = false; if (IS_EMPTY_STMT (SSA_NAME_DEF_STMT (ssa_name))) ; /* 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; } 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: "); debug_generic_stmt (ssa_name); fprintf (stderr, "in statement:\n"); debug_generic_stmt (stmt); } 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); /* Mark all the incoming edges. */ for (e = bb->pred; e; e = e->pred_next) 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); 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"); debug_generic_stmt (op); } e->aux = (void *) 2; } for (e = bb->pred; e; e = e->pred_next) { if (e->aux != (void *) 2) { error ("No argument flowing through edge %d->%d\n", e->src->index, e->dest->index); err = true; } e->aux = (void *) 0; } if (err) { fprintf (stderr, "for PHI node\n"); debug_generic_stmt (phi); } return err; } /* Verify common invariants in the SSA web. TODO: verify the variable annotations. */ void verify_ssa (void) { bool err = false; basic_block bb; basic_block *definition_block = xcalloc (highest_ssa_version, sizeof (basic_block)); timevar_push (TV_TREE_SSA_VERIFY); 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 = TREE_CHAIN (phi)) err |= verify_def (bb, definition_block, PHI_RESULT (phi), phi); for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) { tree stmt; unsigned int j; vdef_optype vdefs; def_optype defs; stmt = bsi_stmt (bsi); get_stmt_operands (stmt); vdefs = STMT_VDEF_OPS (stmt); for (j = 0; j < NUM_VDEFS (vdefs); j++) { tree op = VDEF_RESULT (vdefs, j); if (is_gimple_reg (op)) { error ("Found a virtual definition for a GIMPLE register"); debug_generic_stmt (op); debug_generic_stmt (stmt); err = true; } err |= verify_def (bb, definition_block, op, stmt); } defs = STMT_DEF_OPS (stmt); for (j = 0; j < NUM_DEFS (defs); j++) { tree op = DEF_OP (defs, j); if (TREE_CODE (op) == SSA_NAME && !is_gimple_reg (op)) { error ("Found a real definition for a non-GIMPLE register"); debug_generic_stmt (op); debug_generic_stmt (stmt); err = true; } err |= verify_def (bb, definition_block, op, stmt); } } } /* 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; block_stmt_iterator bsi; /* Make sure that all edges have a clear 'aux' field. */ for (e = bb->pred; e; e = e->pred_next) { if (e->aux) { error ("AUX pointer initialized for edge %d->%d\n", e->src->index, e->dest->index); err = true; } } /* Verify the arguments for every PHI node in the block. */ for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi)) err |= verify_phi_args (phi, bb, definition_block); /* 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); unsigned int j; vuse_optype vuses; use_optype uses; vuses = STMT_VUSE_OPS (stmt); for (j = 0; j < NUM_VUSES (vuses); j++) { tree op = VUSE_OP (vuses, j); if (is_gimple_reg (op)) { error ("Found a virtual use for a GIMPLE register"); debug_generic_stmt (op); debug_generic_stmt (stmt); err = true; } err |= verify_use (bb, definition_block[SSA_NAME_VERSION (op)], op, stmt, false); } uses = STMT_USE_OPS (stmt); for (j = 0; j < NUM_USES (uses); j++) { tree op = USE_OP (uses, j); if (TREE_CODE (op) == SSA_NAME && !is_gimple_reg (op)) { error ("Found a real use of a non-GIMPLE register"); debug_generic_stmt (op); debug_generic_stmt (stmt); err = true; } err |= verify_use (bb, definition_block[SSA_NAME_VERSION (op)], op, stmt, false); } } } free (definition_block); timevar_pop (TV_TREE_SSA_VERIFY); if (err) internal_error ("verify_ssa failed."); } /* Set the USED bit in the annotation for T. */ void set_is_used (tree t) { while (1) { if (SSA_VAR_P (t)) break; switch (TREE_CODE (t)) { case ARRAY_REF: case COMPONENT_REF: case REALPART_EXPR: case IMAGPART_EXPR: case INDIRECT_REF: t = TREE_OPERAND (t, 0); break; default: return; } } if (TREE_CODE (t) == SSA_NAME) t = SSA_NAME_VAR (t); var_ann (t)->used = 1; } /* Initialize global DFA and SSA structures. */ void init_tree_ssa (void) { VARRAY_TREE_INIT (referenced_vars, 20, "referenced_vars"); call_clobbered_vars = BITMAP_XMALLOC (); init_ssa_operands (); init_ssanames (); init_phinodes (); global_var = NULL_TREE; aliases_computed_p = false; } /* 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)) bsi_stmt (bsi)->common.ann = NULL; /* Remove annotations from every referenced variable. */ if (referenced_vars) { for (i = 0; i < num_referenced_vars; i++) referenced_var (i)->common.ann = NULL; referenced_vars = NULL; } fini_ssanames (); fini_phinodes (); fini_ssa_operands (); global_var = NULL_TREE; BITMAP_FREE (call_clobbered_vars); call_clobbered_vars = NULL; aliases_computed_p = false; } /* 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) && 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) && lang_hooks.types_compatible_p (inner_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. Note that type _Bool can have size of 4 (only happens on powerpc-darwin right now but can happen on any target that defines BOOL_TYPE_SIZE to be INT_TYPE_SIZE) and a precision of 1 while unsigned int is the same expect for a precision of 4 so 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) && TREE_UNSIGNED (inner_type) == TREE_UNSIGNED (outer_type) && TYPE_PRECISION (inner_type) == TYPE_PRECISION (outer_type)) 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) 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. */ static bool walk_use_def_chains_1 (tree var, walk_use_def_chains_fn fn, void *data, bitmap visited) { 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; /* Otherwise, follow use-def links out of each PHI argument and call FN after visiting each one. */ 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)) return true; if ((*fn) (arg, 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. For each argument ARG of the PHI node, this function will: 1- Walk the use-def chains for ARG. 2- Call (*FN) (ARG, PHI, DATA). Note how 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). */ void walk_use_def_chains (tree var, walk_use_def_chains_fn fn, void *data) { tree def_stmt; #if defined ENABLE_CHECKING if (TREE_CODE (var) != SSA_NAME) abort (); #endif 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); BITMAP_XFREE (visited); } } /* Replaces immediate uses of VAR by REPL. */ static void replace_immediate_uses (tree var, tree repl) { use_optype uses; vuse_optype vuses; vdef_optype vdefs; int i, j, n; dataflow_t df; tree stmt; 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) { 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); if (is_gimple_reg (SSA_NAME_VAR (var))) { uses = STMT_USE_OPS (stmt); for (j = 0; j < (int) NUM_USES (uses); j++) if (USE_OP (uses, j) == var) propagate_value (USE_OP_PTR (uses, j), repl); } else { vuses = STMT_VUSE_OPS (stmt); for (j = 0; j < (int) NUM_VUSES (vuses); j++) if (VUSE_OP (vuses, j) == var) propagate_value (VUSE_OP_PTR (vuses, j), repl); vdefs = STMT_VDEF_OPS (stmt); for (j = 0; j < (int) NUM_VDEFS (vdefs); j++) if (VDEF_OP (vdefs, j) == var) propagate_value (VDEF_OP_PTR (vdefs, j), repl); } modify_stmt (stmt); /* 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 (POINTER_TYPE_P (TREE_TYPE (repl))) mark_new_vars_to_rename (stmt, vars_to_rename); } } /* Raises value of phi node PHI by joining it with VAL. Processes immediate uses of PHI recursively. */ static void raise_value (tree phi, tree val, tree *eq_to) { int i, n; tree var = PHI_RESULT (phi), stmt; int ver = SSA_NAME_VERSION (var); dataflow_t df; if (eq_to[ver] == var) return; switch (TREE_CODE (val)) { case SSA_NAME: case REAL_CST: case COMPLEX_CST: break; case INTEGER_CST: if (TREE_CODE (TREE_TYPE (var)) != POINTER_TYPE) break; default: /* Do not propagate pointer constants. This might require folding things like *&foo and rewriting the ssa, which is not worth the trouble. */ val = var; } if (eq_to[ver]) { if (operand_equal_p (eq_to[ver], val, 0)) return; eq_to[ver] = var; } else eq_to[ver] = val; 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) continue; raise_value (stmt, eq_to[ver], 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. */ static void kill_redundant_phi_nodes (void) { tree *eq_to, *ssa_names; unsigned i, ver, aver; basic_block bb; tree phi, t, stmt, var; /* The EQ_TO array holds the current value of the ssa name in the lattice: top / | \ const variables \ | / bottom Bottom is represented by NULL and top by the variable itself. Once the dataflow stabilizes, we know that the phi nodes we need to keep are exactly those with top as their result. The remaining phi nodes have their uses replaced with their value in the lattice and the phi node itself is removed. */ eq_to = xcalloc (highest_ssa_version, sizeof (tree)); /* The SSA_NAMES array holds each SSA_NAME node we encounter in a PHI node (indexed by ssa version number). One could argue that the SSA_NAME manager ought to provide a generic interface to get at the SSA_NAME node for a given ssa version number. */ ssa_names = xcalloc (highest_ssa_version, 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); FOR_EACH_BB (bb) { for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi)) { var = PHI_RESULT (phi); ver = SSA_NAME_VERSION (var); ssa_names[ver] = var; for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++) { t = PHI_ARG_DEF (phi, i); if (TREE_CODE (t) != SSA_NAME) { raise_value (phi, t, eq_to); continue; } stmt = SSA_NAME_DEF_STMT (t); aver = SSA_NAME_VERSION (t); ssa_names[aver] = t; /* If the defining statement for this argument is not a phi node or the argument is associated with an abnormal edge, then we need to recursively start the forward dataflow starting with PHI. */ if (TREE_CODE (stmt) != PHI_NODE || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (t)) { eq_to[aver] = t; raise_value (phi, t, eq_to); } } } } /* Now propagate the values. */ for (i = 0; i < highest_ssa_version; i++) if (eq_to[i] && eq_to[i] != ssa_names[i]) replace_immediate_uses (ssa_names[i], eq_to[i]); /* And remove the dead phis. */ for (i = 0; i < highest_ssa_version; i++) if (eq_to[i] && eq_to[i] != ssa_names[i]) { stmt = SSA_NAME_DEF_STMT (ssa_names[i]); remove_phi_node (stmt, 0, bb_for_stmt (stmt)); } free_df (); free (eq_to); free (ssa_names); } 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, /* 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 */ }; /* 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 (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'%D' is used uninitialized in this function", locus); *walk_subtrees = 0; } else if (DECL_P (t) || TYPE_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'%D' 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 = TREE_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 */ }; 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 */ };