From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001 From: upstream source tree Date: Sun, 15 Mar 2015 20:14:05 -0400 Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository. --- gcc/tree-ssa-uninit.c | 1897 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1897 insertions(+) create mode 100644 gcc/tree-ssa-uninit.c (limited to 'gcc/tree-ssa-uninit.c') diff --git a/gcc/tree-ssa-uninit.c b/gcc/tree-ssa-uninit.c new file mode 100644 index 000000000..39785d4b5 --- /dev/null +++ b/gcc/tree-ssa-uninit.c @@ -0,0 +1,1897 @@ +/* Predicate aware uninitialized variable warning. + Copyright (C) 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2010 Free Software + Foundation, Inc. + Contributed by Xinliang David Li + +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 3, 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 COPYING3. If not see +. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "tree.h" +#include "flags.h" +#include "tm_p.h" +#include "langhooks.h" +#include "basic-block.h" +#include "output.h" +#include "function.h" +#include "gimple-pretty-print.h" +#include "bitmap.h" +#include "pointer-set.h" +#include "tree-flow.h" +#include "gimple.h" +#include "tree-inline.h" +#include "timevar.h" +#include "hashtab.h" +#include "tree-dump.h" +#include "tree-pass.h" +#include "diagnostic-core.h" +#include "timevar.h" + +/* This implements the pass that does predicate aware warning on uses of + possibly uninitialized variables. The pass first collects the set of + possibly uninitialized SSA names. For each such name, it walks through + all its immediate uses. For each immediate use, it rebuilds the condition + expression (the predicate) that guards the use. The predicate is then + examined to see if the variable is always defined under that same condition. + This is done either by pruning the unrealizable paths that lead to the + default definitions or by checking if the predicate set that guards the + defining paths is a superset of the use predicate. */ + + +/* Pointer set of potentially undefined ssa names, i.e., + ssa names that are defined by phi with operands that + are not defined or potentially undefined. */ +static struct pointer_set_t *possibly_undefined_names = 0; + +/* Bit mask handling macros. */ +#define MASK_SET_BIT(mask, pos) mask |= (1 << pos) +#define MASK_TEST_BIT(mask, pos) (mask & (1 << pos)) +#define MASK_EMPTY(mask) (mask == 0) + +/* Returns the first bit position (starting from LSB) + in mask that is non zero. Returns -1 if the mask is empty. */ +static int +get_mask_first_set_bit (unsigned mask) +{ + int pos = 0; + if (mask == 0) + return -1; + + while ((mask & (1 << pos)) == 0) + pos++; + + return pos; +} +#define MASK_FIRST_SET_BIT(mask) get_mask_first_set_bit (mask) + + +/* Return true if T, an SSA_NAME, has an undefined value. */ + +bool +ssa_undefined_value_p (tree t) +{ + tree var = SSA_NAME_VAR (t); + + /* Parameters get their initial value from the function entry. */ + if (TREE_CODE (var) == PARM_DECL) + return false; + + /* When returning by reference the return address is actually a hidden + parameter. */ + if (TREE_CODE (SSA_NAME_VAR (t)) == RESULT_DECL + && DECL_BY_REFERENCE (SSA_NAME_VAR (t))) + return false; + + /* Hard register variables get their initial value from the ether. */ + if (TREE_CODE (var) == VAR_DECL && DECL_HARD_REGISTER (var)) + return false; + + /* The value is undefined iff its definition statement is empty. */ + return (gimple_nop_p (SSA_NAME_DEF_STMT (t)) + || (possibly_undefined_names + && pointer_set_contains (possibly_undefined_names, t))); +} + +/* Checks if the operand OPND of PHI is defined by + another phi with one operand defined by this PHI, + but the rest operands are all defined. If yes, + returns true to skip this this operand as being + redundant. Can be enhanced to be more general. */ + +static bool +can_skip_redundant_opnd (tree opnd, gimple phi) +{ + gimple op_def; + tree phi_def; + int i, n; + + phi_def = gimple_phi_result (phi); + op_def = SSA_NAME_DEF_STMT (opnd); + if (gimple_code (op_def) != GIMPLE_PHI) + return false; + n = gimple_phi_num_args (op_def); + for (i = 0; i < n; ++i) + { + tree op = gimple_phi_arg_def (op_def, i); + if (TREE_CODE (op) != SSA_NAME) + continue; + if (op != phi_def && ssa_undefined_value_p (op)) + return false; + } + + return true; +} + +/* Returns a bit mask holding the positions of arguments in PHI + that have empty (or possibly empty) definitions. */ + +static unsigned +compute_uninit_opnds_pos (gimple phi) +{ + size_t i, n; + unsigned uninit_opnds = 0; + + n = gimple_phi_num_args (phi); + /* Bail out for phi with too many args. */ + if (n > 32) + return 0; + + for (i = 0; i < n; ++i) + { + tree op = gimple_phi_arg_def (phi, i); + if (TREE_CODE (op) == SSA_NAME + && ssa_undefined_value_p (op) + && !can_skip_redundant_opnd (op, phi)) + MASK_SET_BIT (uninit_opnds, i); + } + return uninit_opnds; +} + +/* Find the immediate postdominator PDOM of the specified + basic block BLOCK. */ + +static inline basic_block +find_pdom (basic_block block) +{ + if (block == EXIT_BLOCK_PTR) + return EXIT_BLOCK_PTR; + else + { + basic_block bb + = get_immediate_dominator (CDI_POST_DOMINATORS, block); + if (! bb) + return EXIT_BLOCK_PTR; + return bb; + } +} + +/* Find the immediate DOM of the specified + basic block BLOCK. */ + +static inline basic_block +find_dom (basic_block block) +{ + if (block == ENTRY_BLOCK_PTR) + return ENTRY_BLOCK_PTR; + else + { + basic_block bb = get_immediate_dominator (CDI_DOMINATORS, block); + if (! bb) + return ENTRY_BLOCK_PTR; + return bb; + } +} + +/* Returns true if BB1 is postdominating BB2 and BB1 is + not a loop exit bb. The loop exit bb check is simple and does + not cover all cases. */ + +static bool +is_non_loop_exit_postdominating (basic_block bb1, basic_block bb2) +{ + if (!dominated_by_p (CDI_POST_DOMINATORS, bb2, bb1)) + return false; + + if (single_pred_p (bb1) && !single_succ_p (bb2)) + return false; + + return true; +} + +/* Find the closest postdominator of a specified BB, which is control + equivalent to BB. */ + +static inline basic_block +find_control_equiv_block (basic_block bb) +{ + basic_block pdom; + + pdom = find_pdom (bb); + + /* Skip the postdominating bb that is also loop exit. */ + if (!is_non_loop_exit_postdominating (pdom, bb)) + return NULL; + + if (dominated_by_p (CDI_DOMINATORS, pdom, bb)) + return pdom; + + return NULL; +} + +#define MAX_NUM_CHAINS 8 +#define MAX_CHAIN_LEN 5 + +/* Computes the control dependence chains (paths of edges) + for DEP_BB up to the dominating basic block BB (the head node of a + chain should be dominated by it). CD_CHAINS is pointer to a + dynamic array holding the result chains. CUR_CD_CHAIN is the current + chain being computed. *NUM_CHAINS is total number of chains. The + function returns true if the information is successfully computed, + return false if there is no control dependence or not computed. */ + +static bool +compute_control_dep_chain (basic_block bb, basic_block dep_bb, + VEC(edge, heap) **cd_chains, + size_t *num_chains, + VEC(edge, heap) **cur_cd_chain) +{ + edge_iterator ei; + edge e; + size_t i; + bool found_cd_chain = false; + size_t cur_chain_len = 0; + + if (EDGE_COUNT (bb->succs) < 2) + return false; + + /* Could use a set instead. */ + cur_chain_len = VEC_length (edge, *cur_cd_chain); + if (cur_chain_len > MAX_CHAIN_LEN) + return false; + + for (i = 0; i < cur_chain_len; i++) + { + edge e = VEC_index (edge, *cur_cd_chain, i); + /* cycle detected. */ + if (e->src == bb) + return false; + } + + FOR_EACH_EDGE (e, ei, bb->succs) + { + basic_block cd_bb; + if (e->flags & (EDGE_FAKE | EDGE_ABNORMAL)) + continue; + + cd_bb = e->dest; + VEC_safe_push (edge, heap, *cur_cd_chain, e); + while (!is_non_loop_exit_postdominating (cd_bb, bb)) + { + if (cd_bb == dep_bb) + { + /* Found a direct control dependence. */ + if (*num_chains < MAX_NUM_CHAINS) + { + cd_chains[*num_chains] + = VEC_copy (edge, heap, *cur_cd_chain); + (*num_chains)++; + } + found_cd_chain = true; + /* check path from next edge. */ + break; + } + + /* Now check if DEP_BB is indirectly control dependent on BB. */ + if (compute_control_dep_chain (cd_bb, dep_bb, cd_chains, + num_chains, cur_cd_chain)) + { + found_cd_chain = true; + break; + } + + cd_bb = find_pdom (cd_bb); + if (cd_bb == EXIT_BLOCK_PTR) + break; + } + VEC_pop (edge, *cur_cd_chain); + gcc_assert (VEC_length (edge, *cur_cd_chain) == cur_chain_len); + } + gcc_assert (VEC_length (edge, *cur_cd_chain) == cur_chain_len); + + return found_cd_chain; +} + +typedef struct use_pred_info +{ + gimple cond; + bool invert; +} *use_pred_info_t; + +DEF_VEC_P(use_pred_info_t); +DEF_VEC_ALLOC_P(use_pred_info_t, heap); + + +/* Converts the chains of control dependence edges into a set of + predicates. A control dependence chain is represented by a vector + edges. DEP_CHAINS points to an array of dependence chains. + NUM_CHAINS is the size of the chain array. One edge in a dependence + chain is mapped to predicate expression represented by use_pred_info_t + type. One dependence chain is converted to a composite predicate that + is the result of AND operation of use_pred_info_t mapped to each edge. + A composite predicate is presented by a vector of use_pred_info_t. On + return, *PREDS points to the resulting array of composite predicates. + *NUM_PREDS is the number of composite predictes. */ + +static bool +convert_control_dep_chain_into_preds (VEC(edge, heap) **dep_chains, + size_t num_chains, + VEC(use_pred_info_t, heap) ***preds, + size_t *num_preds) +{ + bool has_valid_pred = false; + size_t i, j; + if (num_chains == 0 || num_chains >= MAX_NUM_CHAINS) + return false; + + /* Now convert CD chains into predicates */ + has_valid_pred = true; + + /* Now convert the control dep chain into a set + of predicates. */ + *preds = XCNEWVEC (VEC(use_pred_info_t, heap) *, + num_chains); + *num_preds = num_chains; + + for (i = 0; i < num_chains; i++) + { + VEC(edge, heap) *one_cd_chain = dep_chains[i]; + for (j = 0; j < VEC_length (edge, one_cd_chain); j++) + { + gimple cond_stmt; + gimple_stmt_iterator gsi; + basic_block guard_bb; + use_pred_info_t one_pred; + edge e; + + e = VEC_index (edge, one_cd_chain, j); + guard_bb = e->src; + gsi = gsi_last_bb (guard_bb); + if (gsi_end_p (gsi)) + { + has_valid_pred = false; + break; + } + cond_stmt = gsi_stmt (gsi); + if (gimple_code (cond_stmt) == GIMPLE_CALL + && EDGE_COUNT (e->src->succs) >= 2) + { + /* Ignore EH edge. Can add assertion + on the other edge's flag. */ + continue; + } + /* Skip if there is essentially one succesor. */ + if (EDGE_COUNT (e->src->succs) == 2) + { + edge e1; + edge_iterator ei1; + bool skip = false; + + FOR_EACH_EDGE (e1, ei1, e->src->succs) + { + if (EDGE_COUNT (e1->dest->succs) == 0) + { + skip = true; + break; + } + } + if (skip) + continue; + } + if (gimple_code (cond_stmt) != GIMPLE_COND) + { + has_valid_pred = false; + break; + } + one_pred = XNEW (struct use_pred_info); + one_pred->cond = cond_stmt; + one_pred->invert = !!(e->flags & EDGE_FALSE_VALUE); + VEC_safe_push (use_pred_info_t, heap, (*preds)[i], one_pred); + } + + if (!has_valid_pred) + break; + } + return has_valid_pred; +} + +/* Computes all control dependence chains for USE_BB. The control + dependence chains are then converted to an array of composite + predicates pointed to by PREDS. PHI_BB is the basic block of + the phi whose result is used in USE_BB. */ + +static bool +find_predicates (VEC(use_pred_info_t, heap) ***preds, + size_t *num_preds, + basic_block phi_bb, + basic_block use_bb) +{ + size_t num_chains = 0, i; + VEC(edge, heap) **dep_chains = 0; + VEC(edge, heap) *cur_chain = 0; + bool has_valid_pred = false; + basic_block cd_root = 0; + + dep_chains = XCNEWVEC (VEC(edge, heap) *, MAX_NUM_CHAINS); + + /* First find the closest bb that is control equivalent to PHI_BB + that also dominates USE_BB. */ + cd_root = phi_bb; + while (dominated_by_p (CDI_DOMINATORS, use_bb, cd_root)) + { + basic_block ctrl_eq_bb = find_control_equiv_block (cd_root); + if (ctrl_eq_bb && dominated_by_p (CDI_DOMINATORS, use_bb, ctrl_eq_bb)) + cd_root = ctrl_eq_bb; + else + break; + } + + compute_control_dep_chain (cd_root, use_bb, + dep_chains, &num_chains, + &cur_chain); + + has_valid_pred + = convert_control_dep_chain_into_preds (dep_chains, + num_chains, + preds, + num_preds); + /* Free individual chain */ + VEC_free (edge, heap, cur_chain); + for (i = 0; i < num_chains; i++) + VEC_free (edge, heap, dep_chains[i]); + free (dep_chains); + return has_valid_pred; +} + +/* Computes the set of incoming edges of PHI that have non empty + definitions of a phi chain. The collection will be done + recursively on operands that are defined by phis. CD_ROOT + is the control dependence root. *EDGES holds the result, and + VISITED_PHIS is a pointer set for detecting cycles. */ + +static void +collect_phi_def_edges (gimple phi, basic_block cd_root, + VEC(edge, heap) **edges, + struct pointer_set_t *visited_phis) +{ + size_t i, n; + edge opnd_edge; + tree opnd; + + if (pointer_set_insert (visited_phis, phi)) + return; + + n = gimple_phi_num_args (phi); + for (i = 0; i < n; i++) + { + opnd_edge = gimple_phi_arg_edge (phi, i); + opnd = gimple_phi_arg_def (phi, i); + + if (TREE_CODE (opnd) != SSA_NAME) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "\n[CHECK] Found def edge %d in ", (int)i); + print_gimple_stmt (dump_file, phi, 0, 0); + } + VEC_safe_push (edge, heap, *edges, opnd_edge); + } + else + { + gimple def = SSA_NAME_DEF_STMT (opnd); + + if (gimple_code (def) == GIMPLE_PHI + && dominated_by_p (CDI_DOMINATORS, + gimple_bb (def), cd_root)) + collect_phi_def_edges (def, cd_root, edges, + visited_phis); + else if (!ssa_undefined_value_p (opnd)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "\n[CHECK] Found def edge %d in ", (int)i); + print_gimple_stmt (dump_file, phi, 0, 0); + } + VEC_safe_push (edge, heap, *edges, opnd_edge); + } + } + } +} + +/* For each use edge of PHI, computes all control dependence chains. + The control dependence chains are then converted to an array of + composite predicates pointed to by PREDS. */ + +static bool +find_def_preds (VEC(use_pred_info_t, heap) ***preds, + size_t *num_preds, gimple phi) +{ + size_t num_chains = 0, i, n; + VEC(edge, heap) **dep_chains = 0; + VEC(edge, heap) *cur_chain = 0; + VEC(edge, heap) *def_edges = 0; + bool has_valid_pred = false; + basic_block phi_bb, cd_root = 0; + struct pointer_set_t *visited_phis; + + dep_chains = XCNEWVEC (VEC(edge, heap) *, MAX_NUM_CHAINS); + + phi_bb = gimple_bb (phi); + /* First find the closest dominating bb to be + the control dependence root */ + cd_root = find_dom (phi_bb); + if (!cd_root) + return false; + + visited_phis = pointer_set_create (); + collect_phi_def_edges (phi, cd_root, &def_edges, visited_phis); + pointer_set_destroy (visited_phis); + + n = VEC_length (edge, def_edges); + if (n == 0) + return false; + + for (i = 0; i < n; i++) + { + size_t prev_nc, j; + edge opnd_edge; + + opnd_edge = VEC_index (edge, def_edges, i); + prev_nc = num_chains; + compute_control_dep_chain (cd_root, opnd_edge->src, + dep_chains, &num_chains, + &cur_chain); + /* Free individual chain */ + VEC_free (edge, heap, cur_chain); + cur_chain = 0; + + /* Now update the newly added chains with + the phi operand edge: */ + if (EDGE_COUNT (opnd_edge->src->succs) > 1) + { + if (prev_nc == num_chains + && num_chains < MAX_NUM_CHAINS) + num_chains++; + for (j = prev_nc; j < num_chains; j++) + { + VEC_safe_push (edge, heap, dep_chains[j], opnd_edge); + } + } + } + + has_valid_pred + = convert_control_dep_chain_into_preds (dep_chains, + num_chains, + preds, + num_preds); + for (i = 0; i < num_chains; i++) + VEC_free (edge, heap, dep_chains[i]); + free (dep_chains); + return has_valid_pred; +} + +/* Dumps the predicates (PREDS) for USESTMT. */ + +static void +dump_predicates (gimple usestmt, size_t num_preds, + VEC(use_pred_info_t, heap) **preds, + const char* msg) +{ + size_t i, j; + VEC(use_pred_info_t, heap) *one_pred_chain; + fprintf (dump_file, msg); + print_gimple_stmt (dump_file, usestmt, 0, 0); + fprintf (dump_file, "is guarded by :\n"); + /* do some dumping here: */ + for (i = 0; i < num_preds; i++) + { + size_t np; + + one_pred_chain = preds[i]; + np = VEC_length (use_pred_info_t, one_pred_chain); + + for (j = 0; j < np; j++) + { + use_pred_info_t one_pred + = VEC_index (use_pred_info_t, one_pred_chain, j); + if (one_pred->invert) + fprintf (dump_file, " (.NOT.) "); + print_gimple_stmt (dump_file, one_pred->cond, 0, 0); + if (j < np - 1) + fprintf (dump_file, "(.AND.)\n"); + } + if (i < num_preds - 1) + fprintf (dump_file, "(.OR.)\n"); + } +} + +/* Destroys the predicate set *PREDS. */ + +static void +destroy_predicate_vecs (size_t n, + VEC(use_pred_info_t, heap) ** preds) +{ + size_t i, j; + for (i = 0; i < n; i++) + { + for (j = 0; j < VEC_length (use_pred_info_t, preds[i]); j++) + free (VEC_index (use_pred_info_t, preds[i], j)); + VEC_free (use_pred_info_t, heap, preds[i]); + } + free (preds); +} + + +/* Computes the 'normalized' conditional code with operand + swapping and condition inversion. */ + +static enum tree_code +get_cmp_code (enum tree_code orig_cmp_code, + bool swap_cond, bool invert) +{ + enum tree_code tc = orig_cmp_code; + + if (swap_cond) + tc = swap_tree_comparison (orig_cmp_code); + if (invert) + tc = invert_tree_comparison (tc, false); + + switch (tc) + { + case LT_EXPR: + case LE_EXPR: + case GT_EXPR: + case GE_EXPR: + case EQ_EXPR: + case NE_EXPR: + break; + default: + return ERROR_MARK; + } + return tc; +} + +/* Returns true if VAL falls in the range defined by BOUNDARY and CMPC, i.e. + all values in the range satisfies (x CMPC BOUNDARY) == true. */ + +static bool +is_value_included_in (tree val, tree boundary, enum tree_code cmpc) +{ + bool inverted = false; + bool is_unsigned; + bool result; + + /* Only handle integer constant here. */ + if (TREE_CODE (val) != INTEGER_CST + || TREE_CODE (boundary) != INTEGER_CST) + return true; + + is_unsigned = TYPE_UNSIGNED (TREE_TYPE (val)); + + if (cmpc == GE_EXPR || cmpc == GT_EXPR + || cmpc == NE_EXPR) + { + cmpc = invert_tree_comparison (cmpc, false); + inverted = true; + } + + if (is_unsigned) + { + if (cmpc == EQ_EXPR) + result = tree_int_cst_equal (val, boundary); + else if (cmpc == LT_EXPR) + result = INT_CST_LT_UNSIGNED (val, boundary); + else + { + gcc_assert (cmpc == LE_EXPR); + result = (tree_int_cst_equal (val, boundary) + || INT_CST_LT_UNSIGNED (val, boundary)); + } + } + else + { + if (cmpc == EQ_EXPR) + result = tree_int_cst_equal (val, boundary); + else if (cmpc == LT_EXPR) + result = INT_CST_LT (val, boundary); + else + { + gcc_assert (cmpc == LE_EXPR); + result = (tree_int_cst_equal (val, boundary) + || INT_CST_LT (val, boundary)); + } + } + + if (inverted) + result ^= 1; + + return result; +} + +/* Returns true if PRED is common among all the predicate + chains (PREDS) (and therefore can be factored out). + NUM_PRED_CHAIN is the size of array PREDS. */ + +static bool +find_matching_predicate_in_rest_chains (use_pred_info_t pred, + VEC(use_pred_info_t, heap) **preds, + size_t num_pred_chains) +{ + size_t i, j, n; + + /* trival case */ + if (num_pred_chains == 1) + return true; + + for (i = 1; i < num_pred_chains; i++) + { + bool found = false; + VEC(use_pred_info_t, heap) *one_chain = preds[i]; + n = VEC_length (use_pred_info_t, one_chain); + for (j = 0; j < n; j++) + { + use_pred_info_t pred2 + = VEC_index (use_pred_info_t, one_chain, j); + /* can relax the condition comparison to not + use address comparison. However, the most common + case is that multiple control dependent paths share + a common path prefix, so address comparison should + be ok. */ + + if (pred2->cond == pred->cond + && pred2->invert == pred->invert) + { + found = true; + break; + } + } + if (!found) + return false; + } + return true; +} + +/* Forward declaration. */ +static bool +is_use_properly_guarded (gimple use_stmt, + basic_block use_bb, + gimple phi, + unsigned uninit_opnds, + struct pointer_set_t *visited_phis); + +/* Returns true if all uninitialized opnds are pruned. Returns false + otherwise. PHI is the phi node with uninitialized operands, + UNINIT_OPNDS is the bitmap of the uninitialize operand positions, + FLAG_DEF is the statement defining the flag guarding the use of the + PHI output, BOUNDARY_CST is the const value used in the predicate + associated with the flag, CMP_CODE is the comparison code used in + the predicate, VISITED_PHIS is the pointer set of phis visited, and + VISITED_FLAG_PHIS is the pointer to the pointer set of flag definitions + that are also phis. + + Example scenario: + + BB1: + flag_1 = phi <0, 1> // (1) + var_1 = phi + + + BB2: + flag_2 = phi <0, flag_1, flag_1> // (2) + var_2 = phi + if (flag_2 == 1) + goto BB3; + + BB3: + use of var_2 // (3) + + Because some flag arg in (1) is not constant, if we do not look into the + flag phis recursively, it is conservatively treated as unknown and var_1 + is thought to be flowed into use at (3). Since var_1 is potentially uninitialized + a false warning will be emitted. Checking recursively into (1), the compiler can + find out that only some_val (which is defined) can flow into (3) which is OK. + +*/ + +static bool +prune_uninit_phi_opnds_in_unrealizable_paths ( + gimple phi, unsigned uninit_opnds, + gimple flag_def, tree boundary_cst, + enum tree_code cmp_code, + struct pointer_set_t *visited_phis, + bitmap *visited_flag_phis) +{ + unsigned i; + + for (i = 0; i < MIN (32, gimple_phi_num_args (flag_def)); i++) + { + tree flag_arg; + + if (!MASK_TEST_BIT (uninit_opnds, i)) + continue; + + flag_arg = gimple_phi_arg_def (flag_def, i); + if (!is_gimple_constant (flag_arg)) + { + gimple flag_arg_def, phi_arg_def; + tree phi_arg; + unsigned uninit_opnds_arg_phi; + + if (TREE_CODE (flag_arg) != SSA_NAME) + return false; + flag_arg_def = SSA_NAME_DEF_STMT (flag_arg); + if (gimple_code (flag_arg_def) != GIMPLE_PHI) + return false; + + phi_arg = gimple_phi_arg_def (phi, i); + if (TREE_CODE (phi_arg) != SSA_NAME) + return false; + + phi_arg_def = SSA_NAME_DEF_STMT (phi_arg); + if (gimple_code (phi_arg_def) != GIMPLE_PHI) + return false; + + if (gimple_bb (phi_arg_def) != gimple_bb (flag_arg_def)) + return false; + + if (!*visited_flag_phis) + *visited_flag_phis = BITMAP_ALLOC (NULL); + + if (bitmap_bit_p (*visited_flag_phis, + SSA_NAME_VERSION (gimple_phi_result (flag_arg_def)))) + return false; + + bitmap_set_bit (*visited_flag_phis, + SSA_NAME_VERSION (gimple_phi_result (flag_arg_def))); + + /* Now recursively prune the uninitialized phi args. */ + uninit_opnds_arg_phi = compute_uninit_opnds_pos (phi_arg_def); + if (!prune_uninit_phi_opnds_in_unrealizable_paths ( + phi_arg_def, uninit_opnds_arg_phi, + flag_arg_def, boundary_cst, cmp_code, + visited_phis, visited_flag_phis)) + return false; + + bitmap_clear_bit (*visited_flag_phis, + SSA_NAME_VERSION (gimple_phi_result (flag_arg_def))); + continue; + } + + /* Now check if the constant is in the guarded range. */ + if (is_value_included_in (flag_arg, boundary_cst, cmp_code)) + { + tree opnd; + gimple opnd_def; + + /* Now that we know that this undefined edge is not + pruned. If the operand is defined by another phi, + we can further prune the incoming edges of that + phi by checking the predicates of this operands. */ + + opnd = gimple_phi_arg_def (phi, i); + opnd_def = SSA_NAME_DEF_STMT (opnd); + if (gimple_code (opnd_def) == GIMPLE_PHI) + { + edge opnd_edge; + unsigned uninit_opnds2 + = compute_uninit_opnds_pos (opnd_def); + gcc_assert (!MASK_EMPTY (uninit_opnds2)); + opnd_edge = gimple_phi_arg_edge (phi, i); + if (!is_use_properly_guarded (phi, + opnd_edge->src, + opnd_def, + uninit_opnds2, + visited_phis)) + return false; + } + else + return false; + } + } + + return true; +} + +/* A helper function that determines if the predicate set + of the use is not overlapping with that of the uninit paths. + The most common senario of guarded use is in Example 1: + Example 1: + if (some_cond) + { + x = ...; + flag = true; + } + + ... some code ... + + if (flag) + use (x); + + The real world examples are usually more complicated, but similar + and usually result from inlining: + + bool init_func (int * x) + { + if (some_cond) + return false; + *x = .. + return true; + } + + void foo(..) + { + int x; + + if (!init_func(&x)) + return; + + .. some_code ... + use (x); + } + + Another possible use scenario is in the following trivial example: + + Example 2: + if (n > 0) + x = 1; + ... + if (n > 0) + { + if (m < 2) + .. = x; + } + + Predicate analysis needs to compute the composite predicate: + + 1) 'x' use predicate: (n > 0) .AND. (m < 2) + 2) 'x' default value (non-def) predicate: .NOT. (n > 0) + (the predicate chain for phi operand defs can be computed + starting from a bb that is control equivalent to the phi's + bb and is dominating the operand def.) + + and check overlapping: + (n > 0) .AND. (m < 2) .AND. (.NOT. (n > 0)) + <==> false + + This implementation provides framework that can handle + scenarios. (Note that many simple cases are handled properly + without the predicate analysis -- this is due to jump threading + transformation which eliminates the merge point thus makes + path sensitive analysis unnecessary.) + + NUM_PREDS is the number is the number predicate chains, PREDS is + the array of chains, PHI is the phi node whose incoming (undefined) + paths need to be pruned, and UNINIT_OPNDS is the bitmap holding + uninit operand positions. VISITED_PHIS is the pointer set of phi + stmts being checked. */ + + +static bool +use_pred_not_overlap_with_undef_path_pred ( + size_t num_preds, + VEC(use_pred_info_t, heap) **preds, + gimple phi, unsigned uninit_opnds, + struct pointer_set_t *visited_phis) +{ + unsigned int i, n; + gimple flag_def = 0; + tree boundary_cst = 0; + enum tree_code cmp_code; + bool swap_cond = false; + bool invert = false; + VEC(use_pred_info_t, heap) *the_pred_chain; + bitmap visited_flag_phis = NULL; + bool all_pruned = false; + + gcc_assert (num_preds > 0); + /* Find within the common prefix of multiple predicate chains + a predicate that is a comparison of a flag variable against + a constant. */ + the_pred_chain = preds[0]; + n = VEC_length (use_pred_info_t, the_pred_chain); + for (i = 0; i < n; i++) + { + gimple cond; + tree cond_lhs, cond_rhs, flag = 0; + + use_pred_info_t the_pred + = VEC_index (use_pred_info_t, the_pred_chain, i); + + cond = the_pred->cond; + invert = the_pred->invert; + cond_lhs = gimple_cond_lhs (cond); + cond_rhs = gimple_cond_rhs (cond); + cmp_code = gimple_cond_code (cond); + + if (cond_lhs != NULL_TREE && TREE_CODE (cond_lhs) == SSA_NAME + && cond_rhs != NULL_TREE && is_gimple_constant (cond_rhs)) + { + boundary_cst = cond_rhs; + flag = cond_lhs; + } + else if (cond_rhs != NULL_TREE && TREE_CODE (cond_rhs) == SSA_NAME + && cond_lhs != NULL_TREE && is_gimple_constant (cond_lhs)) + { + boundary_cst = cond_lhs; + flag = cond_rhs; + swap_cond = true; + } + + if (!flag) + continue; + + flag_def = SSA_NAME_DEF_STMT (flag); + + if (!flag_def) + continue; + + if ((gimple_code (flag_def) == GIMPLE_PHI) + && (gimple_bb (flag_def) == gimple_bb (phi)) + && find_matching_predicate_in_rest_chains ( + the_pred, preds, num_preds)) + break; + + flag_def = 0; + } + + if (!flag_def) + return false; + + /* Now check all the uninit incoming edge has a constant flag value + that is in conflict with the use guard/predicate. */ + cmp_code = get_cmp_code (cmp_code, swap_cond, invert); + + if (cmp_code == ERROR_MARK) + return false; + + all_pruned = prune_uninit_phi_opnds_in_unrealizable_paths (phi, + uninit_opnds, + flag_def, + boundary_cst, + cmp_code, + visited_phis, + &visited_flag_phis); + + if (visited_flag_phis) + BITMAP_FREE (visited_flag_phis); + + return all_pruned; +} + +/* Returns true if TC is AND or OR */ + +static inline bool +is_and_or_or (enum tree_code tc, tree typ) +{ + return (tc == TRUTH_AND_EXPR + || tc == TRUTH_OR_EXPR + || tc == BIT_IOR_EXPR + || (tc == BIT_AND_EXPR + && (typ == 0 || TREE_CODE (typ) == BOOLEAN_TYPE))); +} + +typedef struct norm_cond +{ + VEC(gimple, heap) *conds; + enum tree_code cond_code; + bool invert; +} *norm_cond_t; + + +/* Normalizes gimple condition COND. The normalization follows + UD chains to form larger condition expression trees. NORM_COND + holds the normalized result. COND_CODE is the logical opcode + (AND or OR) of the normalized tree. */ + +static void +normalize_cond_1 (gimple cond, + norm_cond_t norm_cond, + enum tree_code cond_code) +{ + enum gimple_code gc; + enum tree_code cur_cond_code; + tree rhs1, rhs2; + + gc = gimple_code (cond); + if (gc != GIMPLE_ASSIGN) + { + VEC_safe_push (gimple, heap, norm_cond->conds, cond); + return; + } + + cur_cond_code = gimple_assign_rhs_code (cond); + rhs1 = gimple_assign_rhs1 (cond); + rhs2 = gimple_assign_rhs2 (cond); + if (cur_cond_code == NE_EXPR) + { + if (integer_zerop (rhs2) + && (TREE_CODE (rhs1) == SSA_NAME)) + normalize_cond_1 ( + SSA_NAME_DEF_STMT (rhs1), + norm_cond, cond_code); + else if (integer_zerop (rhs1) + && (TREE_CODE (rhs2) == SSA_NAME)) + normalize_cond_1 ( + SSA_NAME_DEF_STMT (rhs2), + norm_cond, cond_code); + else + VEC_safe_push (gimple, heap, norm_cond->conds, cond); + + return; + } + + if (is_and_or_or (cur_cond_code, TREE_TYPE (rhs1)) + && (cond_code == cur_cond_code || cond_code == ERROR_MARK) + && (TREE_CODE (rhs1) == SSA_NAME && TREE_CODE (rhs2) == SSA_NAME)) + { + normalize_cond_1 (SSA_NAME_DEF_STMT (rhs1), + norm_cond, cur_cond_code); + normalize_cond_1 (SSA_NAME_DEF_STMT (rhs2), + norm_cond, cur_cond_code); + norm_cond->cond_code = cur_cond_code; + } + else + VEC_safe_push (gimple, heap, norm_cond->conds, cond); +} + +/* See normalize_cond_1 for details. INVERT is a flag to indicate + if COND needs to be inverted or not. */ + +static void +normalize_cond (gimple cond, norm_cond_t norm_cond, bool invert) +{ + enum tree_code cond_code; + + norm_cond->cond_code = ERROR_MARK; + norm_cond->invert = false; + norm_cond->conds = NULL; + gcc_assert (gimple_code (cond) == GIMPLE_COND); + cond_code = gimple_cond_code (cond); + if (invert) + cond_code = invert_tree_comparison (cond_code, false); + + if (cond_code == NE_EXPR) + { + if (integer_zerop (gimple_cond_rhs (cond)) + && (TREE_CODE (gimple_cond_lhs (cond)) == SSA_NAME)) + normalize_cond_1 ( + SSA_NAME_DEF_STMT (gimple_cond_lhs (cond)), + norm_cond, ERROR_MARK); + else if (integer_zerop (gimple_cond_lhs (cond)) + && (TREE_CODE (gimple_cond_rhs (cond)) == SSA_NAME)) + normalize_cond_1 ( + SSA_NAME_DEF_STMT (gimple_cond_rhs (cond)), + norm_cond, ERROR_MARK); + else + { + VEC_safe_push (gimple, heap, norm_cond->conds, cond); + norm_cond->invert = invert; + } + } + else + { + VEC_safe_push (gimple, heap, norm_cond->conds, cond); + norm_cond->invert = invert; + } + + gcc_assert (VEC_length (gimple, norm_cond->conds) == 1 + || is_and_or_or (norm_cond->cond_code, NULL)); +} + +/* Returns true if the domain for condition COND1 is a subset of + COND2. REVERSE is a flag. when it is true the function checks + if COND1 is a superset of COND2. INVERT1 and INVERT2 are flags + to indicate if COND1 and COND2 need to be inverted or not. */ + +static bool +is_gcond_subset_of (gimple cond1, bool invert1, + gimple cond2, bool invert2, + bool reverse) +{ + enum gimple_code gc1, gc2; + enum tree_code cond1_code, cond2_code; + gimple tmp; + tree cond1_lhs, cond1_rhs, cond2_lhs, cond2_rhs; + + /* Take the short cut. */ + if (cond1 == cond2) + return true; + + if (reverse) + { + tmp = cond1; + cond1 = cond2; + cond2 = tmp; + } + + gc1 = gimple_code (cond1); + gc2 = gimple_code (cond2); + + if ((gc1 != GIMPLE_ASSIGN && gc1 != GIMPLE_COND) + || (gc2 != GIMPLE_ASSIGN && gc2 != GIMPLE_COND)) + return cond1 == cond2; + + cond1_code = ((gc1 == GIMPLE_ASSIGN) + ? gimple_assign_rhs_code (cond1) + : gimple_cond_code (cond1)); + + cond2_code = ((gc2 == GIMPLE_ASSIGN) + ? gimple_assign_rhs_code (cond2) + : gimple_cond_code (cond2)); + + if (TREE_CODE_CLASS (cond1_code) != tcc_comparison + || TREE_CODE_CLASS (cond2_code) != tcc_comparison) + return false; + + if (invert1) + cond1_code = invert_tree_comparison (cond1_code, false); + if (invert2) + cond2_code = invert_tree_comparison (cond2_code, false); + + cond1_lhs = ((gc1 == GIMPLE_ASSIGN) + ? gimple_assign_rhs1 (cond1) + : gimple_cond_lhs (cond1)); + cond1_rhs = ((gc1 == GIMPLE_ASSIGN) + ? gimple_assign_rhs2 (cond1) + : gimple_cond_rhs (cond1)); + cond2_lhs = ((gc2 == GIMPLE_ASSIGN) + ? gimple_assign_rhs1 (cond2) + : gimple_cond_lhs (cond2)); + cond2_rhs = ((gc2 == GIMPLE_ASSIGN) + ? gimple_assign_rhs2 (cond2) + : gimple_cond_rhs (cond2)); + + /* Assuming const operands have been swapped to the + rhs at this point of the analysis. */ + + if (cond1_lhs != cond2_lhs) + return false; + + if (!is_gimple_constant (cond1_rhs) + || TREE_CODE (cond1_rhs) != INTEGER_CST) + return (cond1_rhs == cond2_rhs); + + if (!is_gimple_constant (cond2_rhs) + || TREE_CODE (cond2_rhs) != INTEGER_CST) + return (cond1_rhs == cond2_rhs); + + if (cond1_code == EQ_EXPR) + return is_value_included_in (cond1_rhs, + cond2_rhs, cond2_code); + if (cond1_code == NE_EXPR || cond2_code == EQ_EXPR) + return ((cond2_code == cond1_code) + && tree_int_cst_equal (cond1_rhs, cond2_rhs)); + + if (((cond1_code == GE_EXPR || cond1_code == GT_EXPR) + && (cond2_code == LE_EXPR || cond2_code == LT_EXPR)) + || ((cond1_code == LE_EXPR || cond1_code == LT_EXPR) + && (cond2_code == GE_EXPR || cond2_code == GT_EXPR))) + return false; + + if (cond1_code != GE_EXPR && cond1_code != GT_EXPR + && cond1_code != LE_EXPR && cond1_code != LT_EXPR) + return false; + + if (cond1_code == GT_EXPR) + { + cond1_code = GE_EXPR; + cond1_rhs = fold_binary (PLUS_EXPR, TREE_TYPE (cond1_rhs), + cond1_rhs, + fold_convert (TREE_TYPE (cond1_rhs), + integer_one_node)); + } + else if (cond1_code == LT_EXPR) + { + cond1_code = LE_EXPR; + cond1_rhs = fold_binary (MINUS_EXPR, TREE_TYPE (cond1_rhs), + cond1_rhs, + fold_convert (TREE_TYPE (cond1_rhs), + integer_one_node)); + } + + if (!cond1_rhs) + return false; + + gcc_assert (cond1_code == GE_EXPR || cond1_code == LE_EXPR); + + if (cond2_code == GE_EXPR || cond2_code == GT_EXPR || + cond2_code == LE_EXPR || cond2_code == LT_EXPR) + return is_value_included_in (cond1_rhs, + cond2_rhs, cond2_code); + else if (cond2_code == NE_EXPR) + return + (is_value_included_in (cond1_rhs, + cond2_rhs, cond2_code) + && !is_value_included_in (cond2_rhs, + cond1_rhs, cond1_code)); + return false; +} + +/* Returns true if the domain of the condition expression + in COND is a subset of any of the sub-conditions + of the normalized condtion NORM_COND. INVERT is a flag + to indicate of the COND needs to be inverted. + REVERSE is a flag. When it is true, the check is reversed -- + it returns true if COND is a superset of any of the subconditions + of NORM_COND. */ + +static bool +is_subset_of_any (gimple cond, bool invert, + norm_cond_t norm_cond, bool reverse) +{ + size_t i; + size_t len = VEC_length (gimple, norm_cond->conds); + + for (i = 0; i < len; i++) + { + if (is_gcond_subset_of (cond, invert, + VEC_index (gimple, norm_cond->conds, i), + false, reverse)) + return true; + } + return false; +} + +/* NORM_COND1 and NORM_COND2 are normalized logical/BIT OR + expressions (formed by following UD chains not control + dependence chains). The function returns true of domain + of and expression NORM_COND1 is a subset of NORM_COND2's. + The implementation is conservative, and it returns false if + it the inclusion relationship may not hold. */ + +static bool +is_or_set_subset_of (norm_cond_t norm_cond1, + norm_cond_t norm_cond2) +{ + size_t i; + size_t len = VEC_length (gimple, norm_cond1->conds); + + for (i = 0; i < len; i++) + { + if (!is_subset_of_any (VEC_index (gimple, norm_cond1->conds, i), + false, norm_cond2, false)) + return false; + } + return true; +} + +/* NORM_COND1 and NORM_COND2 are normalized logical AND + expressions (formed by following UD chains not control + dependence chains). The function returns true of domain + of and expression NORM_COND1 is a subset of NORM_COND2's. */ + +static bool +is_and_set_subset_of (norm_cond_t norm_cond1, + norm_cond_t norm_cond2) +{ + size_t i; + size_t len = VEC_length (gimple, norm_cond2->conds); + + for (i = 0; i < len; i++) + { + if (!is_subset_of_any (VEC_index (gimple, norm_cond2->conds, i), + false, norm_cond1, true)) + return false; + } + return true; +} + +/* Returns true of the domain if NORM_COND1 is a subset + of that of NORM_COND2. Returns false if it can not be + proved to be so. */ + +static bool +is_norm_cond_subset_of (norm_cond_t norm_cond1, + norm_cond_t norm_cond2) +{ + size_t i; + enum tree_code code1, code2; + + code1 = norm_cond1->cond_code; + code2 = norm_cond2->cond_code; + + if (code1 == TRUTH_AND_EXPR || code1 == BIT_AND_EXPR) + { + /* Both conditions are AND expressions. */ + if (code2 == TRUTH_AND_EXPR || code2 == BIT_AND_EXPR) + return is_and_set_subset_of (norm_cond1, norm_cond2); + /* NORM_COND1 is an AND expression, and NORM_COND2 is an OR + expression. In this case, returns true if any subexpression + of NORM_COND1 is a subset of any subexpression of NORM_COND2. */ + else if (code2 == TRUTH_OR_EXPR || code2 == BIT_IOR_EXPR) + { + size_t len1; + len1 = VEC_length (gimple, norm_cond1->conds); + for (i = 0; i < len1; i++) + { + gimple cond1 = VEC_index (gimple, norm_cond1->conds, i); + if (is_subset_of_any (cond1, false, norm_cond2, false)) + return true; + } + return false; + } + else + { + gcc_assert (code2 == ERROR_MARK); + gcc_assert (VEC_length (gimple, norm_cond2->conds) == 1); + return is_subset_of_any (VEC_index (gimple, norm_cond2->conds, 0), + norm_cond2->invert, norm_cond1, true); + } + } + /* NORM_COND1 is an OR expression */ + else if (code1 == TRUTH_OR_EXPR || code1 == BIT_IOR_EXPR) + { + if (code2 != code1) + return false; + + return is_or_set_subset_of (norm_cond1, norm_cond2); + } + else + { + gcc_assert (code1 == ERROR_MARK); + gcc_assert (VEC_length (gimple, norm_cond1->conds) == 1); + /* Conservatively returns false if NORM_COND1 is non-decomposible + and NORM_COND2 is an AND expression. */ + if (code2 == TRUTH_AND_EXPR || code2 == BIT_AND_EXPR) + return false; + + if (code2 == TRUTH_OR_EXPR || code2 == BIT_IOR_EXPR) + return is_subset_of_any (VEC_index (gimple, norm_cond1->conds, 0), + norm_cond1->invert, norm_cond2, false); + + gcc_assert (code2 == ERROR_MARK); + gcc_assert (VEC_length (gimple, norm_cond2->conds) == 1); + return is_gcond_subset_of (VEC_index (gimple, norm_cond1->conds, 0), + norm_cond1->invert, + VEC_index (gimple, norm_cond2->conds, 0), + norm_cond2->invert, false); + } +} + +/* Returns true of the domain of single predicate expression + EXPR1 is a subset of that of EXPR2. Returns false if it + can not be proved. */ + +static bool +is_pred_expr_subset_of (use_pred_info_t expr1, + use_pred_info_t expr2) +{ + gimple cond1, cond2; + enum tree_code code1, code2; + struct norm_cond norm_cond1, norm_cond2; + bool is_subset = false; + + cond1 = expr1->cond; + cond2 = expr2->cond; + code1 = gimple_cond_code (cond1); + code2 = gimple_cond_code (cond2); + + if (expr1->invert) + code1 = invert_tree_comparison (code1, false); + if (expr2->invert) + code2 = invert_tree_comparison (code2, false); + + /* Fast path -- match exactly */ + if ((gimple_cond_lhs (cond1) == gimple_cond_lhs (cond2)) + && (gimple_cond_rhs (cond1) == gimple_cond_rhs (cond2)) + && (code1 == code2)) + return true; + + /* Normalize conditions. To keep NE_EXPR, do not invert + with both need inversion. */ + normalize_cond (cond1, &norm_cond1, (expr1->invert)); + normalize_cond (cond2, &norm_cond2, (expr2->invert)); + + is_subset = is_norm_cond_subset_of (&norm_cond1, &norm_cond2); + + /* Free memory */ + VEC_free (gimple, heap, norm_cond1.conds); + VEC_free (gimple, heap, norm_cond2.conds); + return is_subset ; +} + +/* Returns true if the domain of PRED1 is a subset + of that of PRED2. Returns false if it can not be proved so. */ + +static bool +is_pred_chain_subset_of (VEC(use_pred_info_t, heap) *pred1, + VEC(use_pred_info_t, heap) *pred2) +{ + size_t np1, np2, i1, i2; + + np1 = VEC_length (use_pred_info_t, pred1); + np2 = VEC_length (use_pred_info_t, pred2); + + for (i2 = 0; i2 < np2; i2++) + { + bool found = false; + use_pred_info_t info2 + = VEC_index (use_pred_info_t, pred2, i2); + for (i1 = 0; i1 < np1; i1++) + { + use_pred_info_t info1 + = VEC_index (use_pred_info_t, pred1, i1); + if (is_pred_expr_subset_of (info1, info2)) + { + found = true; + break; + } + } + if (!found) + return false; + } + return true; +} + +/* Returns true if the domain defined by + one pred chain ONE_PRED is a subset of the domain + of *PREDS. It returns false if ONE_PRED's domain is + not a subset of any of the sub-domains of PREDS ( + corresponding to each individual chains in it), even + though it may be still be a subset of whole domain + of PREDS which is the union (ORed) of all its subdomains. + In other words, the result is conservative. */ + +static bool +is_included_in (VEC(use_pred_info_t, heap) *one_pred, + VEC(use_pred_info_t, heap) **preds, + size_t n) +{ + size_t i; + + for (i = 0; i < n; i++) + { + if (is_pred_chain_subset_of (one_pred, preds[i])) + return true; + } + + return false; +} + +/* compares two predicate sets PREDS1 and PREDS2 and returns + true if the domain defined by PREDS1 is a superset + of PREDS2's domain. N1 and N2 are array sizes of PREDS1 and + PREDS2 respectively. The implementation chooses not to build + generic trees (and relying on the folding capability of the + compiler), but instead performs brute force comparison of + individual predicate chains (won't be a compile time problem + as the chains are pretty short). When the function returns + false, it does not necessarily mean *PREDS1 is not a superset + of *PREDS2, but mean it may not be so since the analysis can + not prove it. In such cases, false warnings may still be + emitted. */ + +static bool +is_superset_of (VEC(use_pred_info_t, heap) **preds1, + size_t n1, + VEC(use_pred_info_t, heap) **preds2, + size_t n2) +{ + size_t i; + VEC(use_pred_info_t, heap) *one_pred_chain; + + for (i = 0; i < n2; i++) + { + one_pred_chain = preds2[i]; + if (!is_included_in (one_pred_chain, preds1, n1)) + return false; + } + + return true; +} + +/* Computes the predicates that guard the use and checks + if the incoming paths that have empty (or possibly + empty) defintion can be pruned/filtered. The function returns + true if it can be determined that the use of PHI's def in + USE_STMT is guarded with a predicate set not overlapping with + predicate sets of all runtime paths that do not have a definition. + Returns false if it is not or it can not be determined. USE_BB is + the bb of the use (for phi operand use, the bb is not the bb of + the phi stmt, but the src bb of the operand edge). UNINIT_OPNDS + is a bit vector. If an operand of PHI is uninitialized, the + correponding bit in the vector is 1. VISIED_PHIS is a pointer + set of phis being visted. */ + +static bool +is_use_properly_guarded (gimple use_stmt, + basic_block use_bb, + gimple phi, + unsigned uninit_opnds, + struct pointer_set_t *visited_phis) +{ + basic_block phi_bb; + VEC(use_pred_info_t, heap) **preds = 0; + VEC(use_pred_info_t, heap) **def_preds = 0; + size_t num_preds = 0, num_def_preds = 0; + bool has_valid_preds = false; + bool is_properly_guarded = false; + + if (pointer_set_insert (visited_phis, phi)) + return false; + + phi_bb = gimple_bb (phi); + + if (is_non_loop_exit_postdominating (use_bb, phi_bb)) + return false; + + has_valid_preds = find_predicates (&preds, &num_preds, + phi_bb, use_bb); + + if (!has_valid_preds) + { + destroy_predicate_vecs (num_preds, preds); + return false; + } + + if (dump_file) + dump_predicates (use_stmt, num_preds, preds, + "\nUse in stmt "); + + has_valid_preds = find_def_preds (&def_preds, + &num_def_preds, phi); + + if (has_valid_preds) + { + if (dump_file) + dump_predicates (phi, num_def_preds, def_preds, + "Operand defs of phi "); + is_properly_guarded = + is_superset_of (def_preds, num_def_preds, + preds, num_preds); + } + + /* further prune the dead incoming phi edges. */ + if (!is_properly_guarded) + is_properly_guarded + = use_pred_not_overlap_with_undef_path_pred ( + num_preds, preds, phi, uninit_opnds, visited_phis); + + destroy_predicate_vecs (num_preds, preds); + destroy_predicate_vecs (num_def_preds, def_preds); + return is_properly_guarded; +} + +/* Searches through all uses of a potentially + uninitialized variable defined by PHI and returns a use + statement if the use is not properly guarded. It returns + NULL if all uses are guarded. UNINIT_OPNDS is a bitvector + holding the position(s) of uninit PHI operands. WORKLIST + is the vector of candidate phis that may be updated by this + function. ADDED_TO_WORKLIST is the pointer set tracking + if the new phi is already in the worklist. */ + +static gimple +find_uninit_use (gimple phi, unsigned uninit_opnds, + VEC(gimple, heap) **worklist, + struct pointer_set_t *added_to_worklist) +{ + tree phi_result; + use_operand_p use_p; + gimple use_stmt; + imm_use_iterator iter; + + phi_result = gimple_phi_result (phi); + + FOR_EACH_IMM_USE_FAST (use_p, iter, phi_result) + { + struct pointer_set_t *visited_phis; + basic_block use_bb; + + use_stmt = USE_STMT (use_p); + if (is_gimple_debug (use_stmt)) + continue; + + visited_phis = pointer_set_create (); + + if (gimple_code (use_stmt) == GIMPLE_PHI) + use_bb = gimple_phi_arg_edge (use_stmt, + PHI_ARG_INDEX_FROM_USE (use_p))->src; + else + use_bb = gimple_bb (use_stmt); + + if (is_use_properly_guarded (use_stmt, + use_bb, + phi, + uninit_opnds, + visited_phis)) + { + pointer_set_destroy (visited_phis); + continue; + } + pointer_set_destroy (visited_phis); + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "[CHECK]: Found unguarded use: "); + print_gimple_stmt (dump_file, use_stmt, 0, 0); + } + /* Found one real use, return. */ + if (gimple_code (use_stmt) != GIMPLE_PHI) + return use_stmt; + + /* Found a phi use that is not guarded, + add the phi to the worklist. */ + if (!pointer_set_insert (added_to_worklist, + use_stmt)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "[WORKLIST]: Update worklist with phi: "); + print_gimple_stmt (dump_file, use_stmt, 0, 0); + } + + VEC_safe_push (gimple, heap, *worklist, use_stmt); + pointer_set_insert (possibly_undefined_names, + phi_result); + } + } + + return NULL; +} + +/* Look for inputs to PHI that are SSA_NAMEs that have empty definitions + and gives warning if there exists a runtime path from the entry to a + use of the PHI def that does not contain a definition. In other words, + the warning is on the real use. The more dead paths that can be pruned + by the compiler, the fewer false positives the warning is. WORKLIST + is a vector of candidate phis to be examined. ADDED_TO_WORKLIST is + a pointer set tracking if the new phi is added to the worklist or not. */ + +static void +warn_uninitialized_phi (gimple phi, VEC(gimple, heap) **worklist, + struct pointer_set_t *added_to_worklist) +{ + unsigned uninit_opnds; + gimple uninit_use_stmt = 0; + tree uninit_op; + + /* Don't look at memory tags. */ + if (!is_gimple_reg (gimple_phi_result (phi))) + return; + + uninit_opnds = compute_uninit_opnds_pos (phi); + + if (MASK_EMPTY (uninit_opnds)) + return; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "[CHECK]: examining phi: "); + print_gimple_stmt (dump_file, phi, 0, 0); + } + + /* Now check if we have any use of the value without proper guard. */ + uninit_use_stmt = find_uninit_use (phi, uninit_opnds, + worklist, added_to_worklist); + + /* All uses are properly guarded. */ + if (!uninit_use_stmt) + return; + + uninit_op = gimple_phi_arg_def (phi, MASK_FIRST_SET_BIT (uninit_opnds)); + warn_uninit (uninit_op, + "%qD may be used uninitialized in this function", + uninit_use_stmt); + +} + + +/* Entry point to the late uninitialized warning pass. */ + +static unsigned int +execute_late_warn_uninitialized (void) +{ + basic_block bb; + gimple_stmt_iterator gsi; + VEC(gimple, heap) *worklist = 0; + struct pointer_set_t *added_to_worklist; + + calculate_dominance_info (CDI_DOMINATORS); + calculate_dominance_info (CDI_POST_DOMINATORS); + /* 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. */ + warn_uninitialized_vars (/*warn_possibly_uninitialized=*/1); + + timevar_push (TV_TREE_UNINIT); + + possibly_undefined_names = pointer_set_create (); + added_to_worklist = pointer_set_create (); + + /* Initialize worklist */ + FOR_EACH_BB (bb) + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gimple phi = gsi_stmt (gsi); + size_t n, i; + + n = gimple_phi_num_args (phi); + + /* Don't look at memory tags. */ + if (!is_gimple_reg (gimple_phi_result (phi))) + continue; + + for (i = 0; i < n; ++i) + { + tree op = gimple_phi_arg_def (phi, i); + if (TREE_CODE (op) == SSA_NAME + && ssa_undefined_value_p (op)) + { + VEC_safe_push (gimple, heap, worklist, phi); + pointer_set_insert (added_to_worklist, phi); + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "[WORKLIST]: add to initial list: "); + print_gimple_stmt (dump_file, phi, 0, 0); + } + break; + } + } + } + + while (VEC_length (gimple, worklist) != 0) + { + gimple cur_phi = 0; + cur_phi = VEC_pop (gimple, worklist); + warn_uninitialized_phi (cur_phi, &worklist, added_to_worklist); + } + + VEC_free (gimple, heap, worklist); + pointer_set_destroy (added_to_worklist); + pointer_set_destroy (possibly_undefined_names); + possibly_undefined_names = NULL; + free_dominance_info (CDI_POST_DOMINATORS); + timevar_pop (TV_TREE_UNINIT); + return 0; +} + +static bool +gate_warn_uninitialized (void) +{ + return warn_uninitialized != 0; +} + +struct gimple_opt_pass pass_late_warn_uninitialized = +{ + { + GIMPLE_PASS, + "uninit", /* name */ + gate_warn_uninitialized, /* gate */ + execute_late_warn_uninitialized, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_NONE, /* tv_id */ + PROP_ssa, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + 0 /* todo_flags_finish */ + } +}; -- cgit v1.2.3