/* Dead store elimination
- Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation,
- Inc.
+ Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009
+ Free Software Foundation, Inc.
This file is part of GCC.
#include "tree-dump.h"
#include "domwalk.h"
#include "flags.h"
+#include "langhooks.h"
/* This file implements dead store elimination.
relationship between dead store and redundant load elimination. In
fact, they are the same transformation applied to different views of
the CFG. */
-
+
struct dse_global_data
{
bitmap stores;
};
-/* Basic blocks of the potentially dead store and the following
- store, for memory_address_same. */
-struct address_walk_data
-{
- basic_block store1_bb, store2_bb;
-};
-
static bool gate_dse (void);
static unsigned int tree_ssa_dse (void);
static void dse_initialize_block_local_data (struct dom_walk_data *,
basic_block,
bool);
-static void dse_optimize_stmt (struct dom_walk_data *,
- basic_block,
- block_stmt_iterator);
-static void dse_record_phis (struct dom_walk_data *, basic_block);
-static void dse_finalize_block (struct dom_walk_data *, basic_block);
+static void dse_enter_block (struct dom_walk_data *, basic_block);
+static void dse_leave_block (struct dom_walk_data *, basic_block);
static void record_voperand_set (bitmap, bitmap *, unsigned int);
/* Returns uid of statement STMT. */
static unsigned
-get_stmt_uid (tree stmt)
+get_stmt_uid (gimple stmt)
{
- if (TREE_CODE (stmt) == PHI_NODE)
- return SSA_NAME_VERSION (PHI_RESULT (stmt)) + gimple_stmt_max_uid (cfun);
+ if (gimple_code (stmt) == GIMPLE_PHI)
+ return SSA_NAME_VERSION (gimple_phi_result (stmt))
+ + gimple_stmt_max_uid (cfun);
- return gimple_stmt_uid (stmt);
+ return gimple_uid (stmt);
}
/* Set bit UID in bitmaps GLOBAL and *LOCAL, creating *LOCAL as needed. */
}
}
-/* Helper function for memory_address_same via walk_tree. Returns
- non-NULL if it finds an SSA_NAME which is part of the address,
- such that the definition of the SSA_NAME post-dominates the store
- we want to delete but not the store that we believe makes it
- redundant. This indicates that the address may change between
- the two stores. */
-
-static tree
-memory_ssa_name_same (tree *expr_p, int *walk_subtrees ATTRIBUTE_UNUSED,
- void *data)
-{
- struct address_walk_data *walk_data = (struct address_walk_data *) data;
- tree expr = *expr_p;
- tree def_stmt;
- basic_block def_bb;
-
- if (TREE_CODE (expr) != SSA_NAME)
- return NULL_TREE;
-
- /* If we've found a default definition, then there's no problem. Both
- stores will post-dominate it. And def_bb will be NULL. */
- if (SSA_NAME_IS_DEFAULT_DEF (expr))
- return NULL_TREE;
-
- def_stmt = SSA_NAME_DEF_STMT (expr);
- def_bb = bb_for_stmt (def_stmt);
-
- /* DEF_STMT must dominate both stores. So if it is in the same
- basic block as one, it does not post-dominate that store. */
- if (walk_data->store1_bb != def_bb
- && dominated_by_p (CDI_POST_DOMINATORS, walk_data->store1_bb, def_bb))
- {
- if (walk_data->store2_bb == def_bb
- || !dominated_by_p (CDI_POST_DOMINATORS, walk_data->store2_bb,
- def_bb))
- /* Return non-NULL to stop the walk. */
- return def_stmt;
- }
-
- return NULL_TREE;
-}
-
-/* Return TRUE if the destination memory address in STORE1 and STORE2
- might be modified after STORE1, before control reaches STORE2. */
-
-static bool
-memory_address_same (tree store1, tree store2)
-{
- struct address_walk_data walk_data;
-
- walk_data.store1_bb = bb_for_stmt (store1);
- walk_data.store2_bb = bb_for_stmt (store2);
-
- return (walk_tree (&GIMPLE_STMT_OPERAND (store1, 0), memory_ssa_name_same,
- &walk_data, NULL)
- == NULL);
-}
-
-/* Return true if there is a stmt that kills the lhs of STMT and is in the
- virtual def-use chain of STMT without a use in between the kill and STMT.
- Returns false if no such stmt is found.
- *FIRST_USE_P is set to the first use of the single virtual def of
- STMT. *USE_P is set to the vop killed by *USE_STMT. */
+/* A helper of dse_optimize_stmt.
+ Given a GIMPLE_ASSIGN in STMT, find a candidate statement *USE_STMT that
+ may prove STMT to be dead.
+ Return TRUE if the above conditions are met, otherwise FALSE. */
static bool
-get_kill_of_stmt_lhs (tree stmt,
- use_operand_p * first_use_p,
- use_operand_p * use_p, tree * use_stmt)
+dse_possible_dead_store_p (gimple stmt, gimple *use_stmt)
{
- tree lhs;
-
- gcc_assert (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT);
+ gimple temp;
+ unsigned cnt = 0;
- lhs = GIMPLE_STMT_OPERAND (stmt, 0);
+ *use_stmt = NULL;
- /* We now walk the chain of single uses of the single VDEFs.
- We succeeded finding a kill if the lhs of the use stmt is
- equal to the original lhs. We can keep walking to the next
- use if there are no possible uses of the original lhs in
- the stmt. */
+ /* Find the first dominated statement that clobbers (part of) the
+ memory stmt stores to with no intermediate statement that may use
+ part of the memory stmt stores. That is, find a store that may
+ prove stmt to be a dead store. */
+ temp = stmt;
do
{
- tree use_lhs, use_rhs;
- def_operand_p def_p;
-
- /* The stmt must have a single VDEF. */
- def_p = SINGLE_SSA_DEF_OPERAND (stmt, SSA_OP_VDEF);
- if (def_p == NULL_DEF_OPERAND_P)
- return false;
-
- /* Get the single immediate use of the def. */
- if (!single_imm_use (DEF_FROM_PTR (def_p), first_use_p, &stmt))
+ gimple prev, use_stmt;
+ imm_use_iterator ui;
+ bool fail = false;
+ tree defvar;
+
+ /* Limit stmt walking to be linear in the number of possibly
+ dead stores. */
+ if (++cnt > 256)
return false;
- first_use_p = use_p;
- /* If there are possible hidden uses, give up. */
- if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT)
- return false;
- use_rhs = GIMPLE_STMT_OPERAND (stmt, 1);
- if (TREE_CODE (use_rhs) == CALL_EXPR
- || (!is_gimple_min_invariant (use_rhs)
- && TREE_CODE (use_rhs) != SSA_NAME))
- return false;
-
- /* If the use stmts lhs matches the original lhs we have
- found the kill, otherwise continue walking. */
- use_lhs = GIMPLE_STMT_OPERAND (stmt, 0);
- if (operand_equal_p (use_lhs, lhs, 0))
+ if (gimple_code (temp) == GIMPLE_PHI)
+ defvar = PHI_RESULT (temp);
+ else
+ defvar = gimple_vdef (temp);
+ prev = temp;
+ temp = NULL;
+ FOR_EACH_IMM_USE_STMT (use_stmt, ui, defvar)
{
- *use_stmt = stmt;
- return true;
- }
- }
- while (1);
-}
-
-/* A helper of dse_optimize_stmt.
- Given a GIMPLE_MODIFY_STMT in STMT, check that each VDEF has one
- use, and that one use is another VDEF clobbering the first one.
-
- Return TRUE if the above conditions are met, otherwise FALSE. */
-
-static bool
-dse_possible_dead_store_p (tree stmt,
- use_operand_p *first_use_p,
- use_operand_p *use_p,
- tree *use_stmt,
- struct dse_global_data *dse_gd,
- struct dse_block_local_data *bd)
-{
- ssa_op_iter op_iter;
- bool fail = false;
- def_operand_p var1;
- vuse_vec_p vv;
- tree defvar = NULL_TREE, temp;
- tree prev_defvar = NULL_TREE;
-
- /* 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 statement which uses
- all of the virtual definitions from STMT. */
- *use_stmt = NULL;
- FOR_EACH_SSA_VDEF_OPERAND (var1, vv, stmt, op_iter)
- {
- defvar = DEF_FROM_PTR (var1);
-
- /* If this virtual def does not have precisely one use, then
- we will not be able to eliminate STMT. */
- if (!has_single_use (defvar))
- {
- 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;
-
- /* ??? If we hit a PHI_NODE we could skip to the PHI_RESULT uses.
- Don't bother to do that for now. */
- if (TREE_CODE (temp) == PHI_NODE)
- {
- fail = true;
- break;
- }
-
- /* In the case of memory partitions, we may get:
+ cnt++;
- # MPT.764_162 = VDEF <MPT.764_161(D)>
- x = {};
- # MPT.764_167 = VDEF <MPT.764_162>
- y = {};
-
- So we must make sure we're talking about the same LHS.
- */
- if (TREE_CODE (temp) == GIMPLE_MODIFY_STMT)
- {
- tree base1 = get_base_address (GIMPLE_STMT_OPERAND (stmt, 0));
- tree base2 = get_base_address (GIMPLE_STMT_OPERAND (temp, 0));
-
- while (base1 && INDIRECT_REF_P (base1))
- base1 = TREE_OPERAND (base1, 0);
- while (base2 && INDIRECT_REF_P (base2))
- base2 = TREE_OPERAND (base2, 0);
-
- if (base1 != base2)
+ /* In simple cases we can look through PHI nodes, but we
+ have to be careful with loops and with memory references
+ containing operands that are also operands of PHI nodes.
+ See gcc.c-torture/execute/20051110-*.c. */
+ if (gimple_code (use_stmt) == GIMPLE_PHI)
+ {
+ if (temp
+ /* We can look through PHIs to post-dominated regions
+ without worrying if the use not also dominates prev
+ (in which case it would be a loop PHI with the use
+ in a latch block). */
+ || gimple_bb (prev) == gimple_bb (use_stmt)
+ || !dominated_by_p (CDI_POST_DOMINATORS,
+ gimple_bb (prev), gimple_bb (use_stmt))
+ || dominated_by_p (CDI_DOMINATORS,
+ gimple_bb (prev), gimple_bb (use_stmt)))
+ {
+ fail = true;
+ BREAK_FROM_IMM_USE_STMT (ui);
+ }
+ temp = use_stmt;
+ }
+ /* If the statement is a use the store is not dead. */
+ else if (ref_maybe_used_by_stmt_p (use_stmt,
+ gimple_assign_lhs (stmt)))
{
fail = true;
- break;
+ BREAK_FROM_IMM_USE_STMT (ui);
+ }
+ /* If this is a store, remember it or bail out if we have
+ multiple ones (the will be in different CFG parts then). */
+ else if (gimple_vdef (use_stmt))
+ {
+ if (temp)
+ {
+ fail = true;
+ BREAK_FROM_IMM_USE_STMT (ui);
+ }
+ temp = use_stmt;
}
}
- /* 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;
- prev_defvar = defvar;
- }
- else if (temp != *use_stmt)
+ if (fail)
+ return false;
+
+ /* If we didn't find any definition this means the store is dead
+ if it isn't a store to global reachable memory. In this case
+ just pretend the stmt makes itself dead. Otherwise fail. */
+ if (!temp)
{
- fail = true;
+ if (is_hidden_global_store (stmt))
+ return false;
+
+ temp = stmt;
break;
}
}
+ /* We deliberately stop on clobbering statements and not only on
+ killing ones to make walking cheaper. Otherwise we can just
+ continue walking until both stores have equal reference trees. */
+ while (!stmt_may_clobber_ref_p (temp, gimple_assign_lhs (stmt)));
- if (fail)
- {
- record_voperand_set (dse_gd->stores, &bd->stores, gimple_stmt_uid (stmt));
- return false;
- }
+ if (!is_gimple_assign (temp))
+ return false;
+
+ *use_stmt = temp;
return true;
}
post dominates the first store, then the first store is dead. */
static void
-dse_optimize_stmt (struct dom_walk_data *walk_data,
- basic_block bb ATTRIBUTE_UNUSED,
- block_stmt_iterator bsi)
+dse_optimize_stmt (struct dse_global_data *dse_gd,
+ struct dse_block_local_data *bd,
+ gimple_stmt_iterator gsi)
{
- struct dse_block_local_data *bd
- = (struct dse_block_local_data *)
- VEC_last (void_p, walk_data->block_data_stack);
- struct dse_global_data *dse_gd
- = (struct dse_global_data *) walk_data->global_data;
- tree stmt = bsi_stmt (bsi);
- stmt_ann_t ann = stmt_ann (stmt);
+ gimple stmt = gsi_stmt (gsi);
/* If this statement has no virtual defs, then there is nothing
to do. */
- if (ZERO_SSA_OPERANDS (stmt, SSA_OP_VDEF))
+ if (!gimple_vdef (stmt))
return;
- /* We know we have virtual definitions. If this is a GIMPLE_MODIFY_STMT
+ /* We know we have virtual definitions. If this is a GIMPLE_ASSIGN
that's not also a function call, then record it into our table. */
- if (get_call_expr_in (stmt))
+ if (is_gimple_call (stmt) && gimple_call_fndecl (stmt))
return;
- if (ann->has_volatile_ops)
+ if (gimple_has_volatile_ops (stmt))
return;
- if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
+ if (is_gimple_assign (stmt))
{
- use_operand_p first_use_p = NULL_USE_OPERAND_P;
- use_operand_p use_p = NULL;
- tree use_stmt;
+ gimple use_stmt;
- if (!dse_possible_dead_store_p (stmt, &first_use_p, &use_p, &use_stmt,
- dse_gd, bd))
- return;
+ record_voperand_set (dse_gd->stores, &bd->stores, gimple_uid (stmt));
- /* If we have precisely one immediate use at this point, then we may
- have found redundant store. Make sure that the stores are to
- the same memory location. This includes checking that any
- SSA-form variables in the address will have the same values. */
- if (use_p != NULL_USE_OPERAND_P
- && bitmap_bit_p (dse_gd->stores, get_stmt_uid (use_stmt))
- && !operand_equal_p (GIMPLE_STMT_OPERAND (stmt, 0),
- GIMPLE_STMT_OPERAND (use_stmt, 0), 0)
- && memory_address_same (stmt, use_stmt))
- {
- /* If we have precisely one immediate use at this point, but
- the stores are not to the same memory location then walk the
- virtual def-use chain to get the stmt which stores to that same
- memory location. */
- if (!get_kill_of_stmt_lhs (stmt, &first_use_p, &use_p, &use_stmt))
- {
- record_voperand_set (dse_gd->stores, &bd->stores, gimple_stmt_uid (stmt));
- return;
- }
- }
+ if (!dse_possible_dead_store_p (stmt, &use_stmt))
+ return;
/* If we have precisely one immediate use at this point and the
stores are to the same memory location or there is a chain of
virtual uses from stmt and the stmt which stores to that same
memory location, then we may have found redundant store. */
- if (use_p != NULL_USE_OPERAND_P
- && bitmap_bit_p (dse_gd->stores, get_stmt_uid (use_stmt))
- && operand_equal_p (GIMPLE_STMT_OPERAND (stmt, 0),
- GIMPLE_STMT_OPERAND (use_stmt, 0), 0)
- && memory_address_same (stmt, use_stmt))
+ if (bitmap_bit_p (dse_gd->stores, get_stmt_uid (use_stmt))
+ && operand_equal_p (gimple_assign_lhs (stmt),
+ gimple_assign_lhs (use_stmt), 0))
{
- ssa_op_iter op_iter;
- def_operand_p var1;
- vuse_vec_p vv;
- tree stmt_lhs;
-
/* If use_stmt is or might be a nop assignment, e.g. for
struct { ... } S a, b, *p; ...
b = a; b = b;
*p = *u; *p = *v; where p might be v, then USE_STMT
acts as a use as well as definition, so store in STMT
is not dead. */
- if (LOADED_SYMS (use_stmt)
- && bitmap_intersect_p (LOADED_SYMS (use_stmt),
- STORED_SYMS (use_stmt)))
- {
- record_voperand_set (dse_gd->stores, &bd->stores, ann->uid);
- return;
- }
+ if (stmt != use_stmt
+ && !is_gimple_reg (gimple_assign_rhs1 (use_stmt))
+ && !is_gimple_min_invariant (gimple_assign_rhs1 (use_stmt))
+ /* ??? Should {} be invariant? */
+ && gimple_assign_rhs_code (use_stmt) != CONSTRUCTOR
+ && refs_may_alias_p (gimple_assign_lhs (use_stmt),
+ gimple_assign_rhs1 (use_stmt)))
+ return;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " Deleted dead store '");
- print_generic_expr (dump_file, bsi_stmt (bsi), dump_flags);
+ print_gimple_stmt (dump_file, gsi_stmt (gsi), dump_flags, 0);
fprintf (dump_file, "'\n");
}
/* Then we need to fix the operand of the consuming stmt. */
- stmt_lhs = USE_FROM_PTR (first_use_p);
- FOR_EACH_SSA_VDEF_OPERAND (var1, vv, stmt, op_iter)
- {
- tree usevar, temp;
-
- single_imm_use (DEF_FROM_PTR (var1), &use_p, &temp);
- gcc_assert (VUSE_VECT_NUM_ELEM (*vv) == 1);
- usevar = VUSE_ELEMENT_VAR (*vv, 0);
- SET_USE (use_p, usevar);
-
- /* Make sure we propagate the ABNORMAL bit setting. */
- if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (stmt_lhs))
- SSA_NAME_OCCURS_IN_ABNORMAL_PHI (usevar) = 1;
- }
+ unlink_stmt_vdef (stmt);
/* Remove the dead store. */
- bsi_remove (&bsi, true);
+ gsi_remove (&gsi, true);
/* And release any SSA_NAMEs set in this statement back to the
SSA_NAME manager. */
release_defs (stmt);
}
-
- record_voperand_set (dse_gd->stores, &bd->stores, gimple_stmt_uid (stmt));
}
}
/* Record that we have seen the PHIs at the start of BB which correspond
to virtual operands. */
static void
-dse_record_phis (struct dom_walk_data *walk_data, basic_block bb)
+dse_record_phi (struct dse_global_data *dse_gd,
+ struct dse_block_local_data *bd,
+ gimple phi)
+{
+ if (!is_gimple_reg (gimple_phi_result (phi)))
+ record_voperand_set (dse_gd->stores, &bd->stores, get_stmt_uid (phi));
+}
+
+static void
+dse_enter_block (struct dom_walk_data *walk_data, basic_block bb)
{
struct dse_block_local_data *bd
= (struct dse_block_local_data *)
VEC_last (void_p, walk_data->block_data_stack);
struct dse_global_data *dse_gd
= (struct dse_global_data *) walk_data->global_data;
- tree phi;
+ gimple_stmt_iterator gsi;
- for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
- if (!is_gimple_reg (PHI_RESULT (phi)))
- record_voperand_set (dse_gd->stores,
- &bd->stores,
- get_stmt_uid (phi));
+ for (gsi = gsi_last (bb_seq (bb)); !gsi_end_p (gsi); gsi_prev (&gsi))
+ dse_optimize_stmt (dse_gd, bd, gsi);
+ for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+ dse_record_phi (dse_gd, bd, gsi_stmt (gsi));
}
static void
-dse_finalize_block (struct dom_walk_data *walk_data,
- basic_block bb ATTRIBUTE_UNUSED)
+dse_leave_block (struct dom_walk_data *walk_data,
+ basic_block bb ATTRIBUTE_UNUSED)
{
struct dse_block_local_data *bd
= (struct dse_block_local_data *)
this pass could be seen as an extension of DCE which needs post
dominators. */
calculate_dominance_info (CDI_POST_DOMINATORS);
+ calculate_dominance_info (CDI_DOMINATORS);
/* Dead store elimination is fundamentally a walk of the post-dominator
tree and a backwards walk of statements within each block. */
- walk_data.walk_stmts_backward = true;
walk_data.dom_direction = CDI_POST_DOMINATORS;
walk_data.initialize_block_local_data = dse_initialize_block_local_data;
- walk_data.before_dom_children_before_stmts = NULL;
- walk_data.before_dom_children_walk_stmts = dse_optimize_stmt;
- walk_data.before_dom_children_after_stmts = dse_record_phis;
- walk_data.after_dom_children_before_stmts = NULL;
- walk_data.after_dom_children_walk_stmts = NULL;
- walk_data.after_dom_children_after_stmts = dse_finalize_block;
- walk_data.interesting_blocks = NULL;
+ walk_data.before_dom_children = dse_enter_block;
+ walk_data.after_dom_children = dse_leave_block;
walk_data.block_local_data_size = sizeof (struct dse_block_local_data);
NULL, /* next */
0, /* static_pass_number */
TV_TREE_DSE, /* tv_id */
- PROP_cfg
- | PROP_ssa
- | PROP_alias, /* properties_required */
+ PROP_cfg | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
}
};
-/* A very simple dead store pass eliminating write only local variables.
- The pass does not require alias information and thus can be run before
- inlining to quickly eliminate artifacts of some common C++ constructs. */
-
-static unsigned int
-execute_simple_dse (void)
-{
- block_stmt_iterator bsi;
- basic_block bb;
- bitmap variables_loaded = BITMAP_ALLOC (NULL);
- unsigned int todo = 0;
-
- /* Collect into VARIABLES LOADED all variables that are read in function
- body. */
- FOR_EACH_BB (bb)
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
- if (LOADED_SYMS (bsi_stmt (bsi)))
- bitmap_ior_into (variables_loaded,
- LOADED_SYMS (bsi_stmt (bsi)));
-
- /* Look for statements writing into the write only variables.
- And try to remove them. */
-
- FOR_EACH_BB (bb)
- for (bsi = bsi_start (bb); !bsi_end_p (bsi);)
- {
- tree stmt = bsi_stmt (bsi), op;
- bool removed = false;
- ssa_op_iter iter;
-
- if (STORED_SYMS (stmt) && TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
- && TREE_CODE (stmt) != RETURN_EXPR
- && !bitmap_intersect_p (STORED_SYMS (stmt), variables_loaded))
- {
- unsigned int i;
- bitmap_iterator bi;
- bool dead = true;
-
-
-
- /* See if STMT only stores to write-only variables and
- verify that there are no volatile operands. tree-ssa-operands
- sets has_volatile_ops flag for all statements involving
- reads and writes when aliases are not built to prevent passes
- from removing them as dead. The flag thus has no use for us
- and we need to look into all operands. */
-
- EXECUTE_IF_SET_IN_BITMAP (STORED_SYMS (stmt), 0, i, bi)
- {
- tree var = referenced_var_lookup (i);
- if (TREE_ADDRESSABLE (var)
- || is_global_var (var)
- || TREE_THIS_VOLATILE (var))
- dead = false;
- }
-
- if (dead && LOADED_SYMS (stmt))
- EXECUTE_IF_SET_IN_BITMAP (LOADED_SYMS (stmt), 0, i, bi)
- if (TREE_THIS_VOLATILE (referenced_var_lookup (i)))
- dead = false;
-
- if (dead)
- FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_ALL_OPERANDS)
- if (TREE_THIS_VOLATILE (op))
- dead = false;
-
- /* Look for possible occurrence var = indirect_ref (...) where
- indirect_ref itself is volatile. */
-
- if (dead && TREE_THIS_VOLATILE (GIMPLE_STMT_OPERAND (stmt, 1)))
- dead = false;
-
- if (dead)
- {
- tree call = get_call_expr_in (stmt);
-
- /* When LHS of var = call (); is dead, simplify it into
- call (); saving one operand. */
- if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
- && call
- && TREE_SIDE_EFFECTS (call))
- {
- if (dump_file && (dump_flags & TDF_DETAILS))
- {
- fprintf (dump_file, "Deleted LHS of call: ");
- print_generic_stmt (dump_file, stmt, TDF_SLIM);
- fprintf (dump_file, "\n");
- }
- push_stmt_changes (bsi_stmt_ptr (bsi));
- TREE_BLOCK (call) = TREE_BLOCK (stmt);
- bsi_replace (&bsi, call, false);
- maybe_clean_or_replace_eh_stmt (stmt, call);
- mark_symbols_for_renaming (call);
- pop_stmt_changes (bsi_stmt_ptr (bsi));
- }
- else
- {
- if (dump_file && (dump_flags & TDF_DETAILS))
- {
- fprintf (dump_file, " Deleted dead store '");
- print_generic_expr (dump_file, stmt, dump_flags);
- fprintf (dump_file, "'\n");
- }
- removed = true;
- bsi_remove (&bsi, true);
- todo |= TODO_cleanup_cfg;
- }
- todo |= TODO_remove_unused_locals | TODO_ggc_collect;
- }
- }
- if (!removed)
- bsi_next (&bsi);
- }
- BITMAP_FREE (variables_loaded);
- return todo;
-}
-
-struct gimple_opt_pass pass_simple_dse =
-{
- {
- GIMPLE_PASS,
- "sdse", /* name */
- NULL, /* gate */
- execute_simple_dse, /* 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 */
- TODO_dump_func /* todo_flags_finish */
- }
-};
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