diff options
Diffstat (limited to 'gcc/tree-ssa-dse.c')
| -rw-r--r-- | gcc/tree-ssa-dse.c | 70 |
1 files changed, 42 insertions, 28 deletions
diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c index 1f376c4b964..42b61553832 100644 --- a/gcc/tree-ssa-dse.c +++ b/gcc/tree-ssa-dse.c @@ -111,18 +111,8 @@ get_stmt_uid (tree stmt) return stmt_ann (stmt)->uid; } -/* Function indicating whether we ought to include information for 'var' - when calculating immediate uses. For this pass we only want use - information for virtual variables. */ - -static bool -need_imm_uses_for (tree var) -{ - return !is_gimple_reg (var); -} - - /* Set bit UID in bitmaps GLOBAL and *LOCAL, creating *LOCAL as needed. */ + static void record_voperand_set (bitmap global, bitmap *local, unsigned int uid) { @@ -136,6 +126,7 @@ record_voperand_set (bitmap global, bitmap *local, unsigned int uid) bitmap_set_bit (*local, uid); bitmap_set_bit (global, uid); } + /* Initialize block local data structures. */ static void @@ -177,12 +168,15 @@ dse_optimize_stmt (struct dom_walk_data *walk_data, tree stmt = bsi_stmt (bsi); stmt_ann_t ann = stmt_ann (stmt); v_may_def_optype v_may_defs; + v_must_def_optype v_must_defs; v_may_defs = V_MAY_DEF_OPS (ann); + v_must_defs = V_MUST_DEF_OPS (ann); /* If this statement has no virtual defs, then there is nothing to do. */ - if (NUM_V_MAY_DEFS (v_may_defs) == 0) + if (NUM_V_MAY_DEFS (v_may_defs) == 0 + && NUM_V_MUST_DEFS (v_must_defs) == 0) return; /* We know we have virtual definitions. If this is a MODIFY_EXPR that's @@ -195,33 +189,53 @@ dse_optimize_stmt (struct dom_walk_data *walk_data, if (TREE_CODE (stmt) == MODIFY_EXPR) { - unsigned int num_uses = 0, count = 0; use_operand_p first_use_p = NULL_USE_OPERAND_P; - use_operand_p use_p; - tree use, use_stmt; + use_operand_p use_p = NULL; + tree use, use_stmt, temp; tree defvar = NULL_TREE, usevar = NULL_TREE; + bool fail = false; use_operand_p var2; def_operand_p var1; ssa_op_iter op_iter; - FOR_EACH_SSA_MAYDEF_OPERAND (var1, var2, stmt, op_iter) - { + /* We want to verify that each virtual definition in STMT has + precisely one use and that all the virtual definitions are + used by the same single statement. When complete, we + want USE_STMT to refer to the one statment which uses + all of the virtual definitions from STMT. */ + use_stmt = NULL; + FOR_EACH_SSA_MUST_AND_MAY_DEF_OPERAND (var1, var2, stmt, op_iter) + { defvar = DEF_FROM_PTR (var1); usevar = USE_FROM_PTR (var2); - num_uses += num_imm_uses (defvar); - count++; - if (num_uses > 1 || count > 1) - break; - } - if (count == 1 && num_uses == 1) - { - single_imm_use (defvar, &use_p, &use_stmt); + /* If this virtual def does not have precisely one use, then + we will not be able to eliminate STMT. */ + if (num_imm_uses (defvar) != 1) + { + fail = true; + break; + } + + /* Get the one and only immediate use of DEFVAR. */ + single_imm_use (defvar, &use_p, &temp); gcc_assert (use_p != NULL_USE_OPERAND_P); first_use_p = use_p; use = USE_FROM_PTR (use_p); + + /* If the immediate use of DEF_VAR is not the same as the + previously find immediate uses, then we will not be able + to eliminate STMT. */ + if (use_stmt == NULL) + use_stmt = temp; + else if (temp != use_stmt) + { + fail = true; + break; + } } - else + + if (fail) { record_voperand_set (dse_gd->stores, &bd->stores, ann->uid); return; @@ -231,7 +245,7 @@ dse_optimize_stmt (struct dom_walk_data *walk_data, represents the only use of this store. Note this does not handle the case where the store has - multiple V_MAY_DEFs which all reach a set of PHI nodes in the + multiple V_{MAY,MUST}_DEFs which all reach a set of PHI nodes in the same block. */ while (use_p != NULL_USE_OPERAND_P && TREE_CODE (use_stmt) == PHI_NODE @@ -295,7 +309,7 @@ dse_record_phis (struct dom_walk_data *walk_data, basic_block bb) tree phi; for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) - if (need_imm_uses_for (PHI_RESULT (phi))) + if (!is_gimple_reg (PHI_RESULT (phi))) record_voperand_set (dse_gd->stores, &bd->stores, get_stmt_uid (phi)); |