/* Dead store elimination
- Copyright (C) 2004 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005, 2006, 2007 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)
+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,
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. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
-#include "errors.h"
#include "ggc.h"
#include "tree.h"
#include "rtl.h"
#include "tree-dump.h"
#include "domwalk.h"
#include "flags.h"
+#include "hashtab.h"
+#include "sbitmap.h"
/* This file implements dead store elimination.
the CFG. */
+/* Given an aggregate, this records the parts of it which have been
+ stored into. */
+struct aggregate_vardecl_d
+{
+ /* The aggregate. */
+ tree decl;
+
+ /* Some aggregates are too big for us to handle or never get stored
+ to as a whole. If this field is TRUE, we don't care about this
+ aggregate. */
+ bool ignore;
+
+ /* Number of parts in the whole. */
+ unsigned nparts;
+
+ /* A bitmap of parts of the aggregate that have been set. If part N
+ of an aggregate has been stored to, bit N should be on. */
+ sbitmap parts_set;
+};
+
struct dse_global_data
{
/* This is the global bitmap for store statements.
that we want to record, set the bit corresponding to the statement's
unique ID in this bitmap. */
bitmap stores;
+
+ /* A hash table containing the parts of an aggregate which have been
+ stored to. */
+ htab_t aggregate_vardecl;
};
/* We allocate a bitmap-per-block for stores which are encountered
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 void tree_ssa_dse (void);
+static unsigned int tree_ssa_dse (void);
static void dse_initialize_block_local_data (struct dom_walk_data *,
basic_block,
bool);
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 fix_phi_uses (tree, tree);
-static void fix_stmt_v_may_defs (tree, tree);
static void record_voperand_set (bitmap, bitmap *, unsigned int);
+static void dse_record_partial_aggregate_store (tree, struct dse_global_data *);
static unsigned max_stmt_uid; /* Maximal uid of a statement. Uids to phi
nodes are assigned using the versions of
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. */
+/* Set bit UID in bitmaps GLOBAL and *LOCAL, creating *LOCAL as needed. */
+
+static void
+record_voperand_set (bitmap global, bitmap *local, unsigned int uid)
+{
+ /* Lazily allocate the bitmap. Note that we do not get a notification
+ when the block local data structures die, so we allocate the local
+ bitmap backed by the GC system. */
+ if (*local == NULL)
+ *local = BITMAP_GGC_ALLOC ();
+
+ /* Set the bit in the local and global bitmaps. */
+ bitmap_set_bit (*local, uid);
+ bitmap_set_bit (global, uid);
+}
+
+/* Initialize block local data structures. */
+
+static void
+dse_initialize_block_local_data (struct dom_walk_data *walk_data,
+ basic_block bb ATTRIBUTE_UNUSED,
+ bool recycled)
+{
+ struct dse_block_local_data *bd
+ = (struct dse_block_local_data *)
+ VEC_last (void_p, walk_data->block_data_stack);
+
+ /* If we are given a recycled block local data structure, ensure any
+ bitmap associated with the block is cleared. */
+ if (recycled)
+ {
+ if (bd->stores)
+ bitmap_clear (bd->stores);
+ }
+}
+
+/* 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
-need_imm_uses_for (tree var)
+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 the use stmt for the lhs of STMT following the virtual
+ def-use chains. Returns the MODIFY_EXPR stmt which lhs is equal to
+ the lhs of STMT or NULL_TREE if no such stmt can be found. */
+static tree
+get_use_of_stmt_lhs (tree stmt,
+ use_operand_p * first_use_p,
+ use_operand_p * use_p, tree * use_stmt)
{
- return !is_gimple_reg (var);
+ tree usevar, lhs;
+ def_operand_p def_p;
+
+ if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT)
+ return NULL_TREE;
+
+ lhs = GIMPLE_STMT_OPERAND (stmt, 0);
+
+ /* 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 NULL_TREE;
+
+ if (!has_single_use (DEF_FROM_PTR (def_p)))
+ return NULL_TREE;
+ /* Get the immediate use of the def. */
+ single_imm_use (DEF_FROM_PTR (def_p), use_p, use_stmt);
+ gcc_assert (*use_p != NULL_USE_OPERAND_P);
+ first_use_p = use_p;
+ if (TREE_CODE (*use_stmt) != GIMPLE_MODIFY_STMT)
+ return NULL_TREE;
+
+ do
+ {
+ /* Look at the use stmt and see if it's LHS matches
+ stmt's lhs SSA_NAME. */
+ def_p = SINGLE_SSA_DEF_OPERAND (*use_stmt, SSA_OP_VDEF);
+ if (def_p == NULL_DEF_OPERAND_P)
+ return NULL_TREE;
+
+ usevar = GIMPLE_STMT_OPERAND (*use_stmt, 0);
+ if (operand_equal_p (usevar, lhs, 0))
+ return *use_stmt;
+
+ if (!has_single_use (DEF_FROM_PTR (def_p)))
+ return NULL_TREE;
+ single_imm_use (DEF_FROM_PTR (def_p), use_p, use_stmt);
+ gcc_assert (*use_p != NULL_USE_OPERAND_P);
+ if (TREE_CODE (*use_stmt) != GIMPLE_MODIFY_STMT)
+ return NULL_TREE;
+ }
+ while (1);
+
+ return NULL_TREE;
}
+/* 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.
-/* Replace uses in PHI which match V_MAY_DEF_RESULTs in STMT with the
- corresponding V_MAY_DEF_OP in STMT. */
+ Return TRUE if the above conditions are met, otherwise FALSE. */
-static void
-fix_phi_uses (tree phi, tree stmt)
+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;
stmt_ann_t ann = stmt_ann (stmt);
- v_may_def_optype v_may_defs;
- unsigned int i;
- int j;
- get_stmt_operands (stmt);
- v_may_defs = V_MAY_DEF_OPS (ann);
+ /* 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;
+
+ /* In the case of memory partitions, we may get:
+
+ # MPT.764_162 = VDEF <MPT.764_161(D)>
+ x = {};
+ # MPT.764_167 = VDEF <MPT.764_162>
+ y = {};
- /* Walk each V_MAY_DEF in STMT. */
- for (i = 0; i < NUM_V_MAY_DEFS (v_may_defs); i++)
+ 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)
+ {
+ fail = true;
+ break;
+ }
+ }
+
+ /* 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)
+ {
+ /* The immediate use and the previously found immediate use
+ must be the same, except... if they're uses of different
+ parts of the whole. */
+ if (TREE_CODE (defvar) == SSA_NAME
+ && TREE_CODE (SSA_NAME_VAR (defvar)) == STRUCT_FIELD_TAG
+ && TREE_CODE (prev_defvar) == SSA_NAME
+ && TREE_CODE (SSA_NAME_VAR (prev_defvar)) == STRUCT_FIELD_TAG
+ && (SFT_PARENT_VAR (SSA_NAME_VAR (defvar))
+ == SFT_PARENT_VAR (SSA_NAME_VAR (prev_defvar))))
+ ;
+ else
+ {
+ fail = true;
+ break;
+ }
+ }
+ }
+
+ if (fail)
{
- tree v_may_def = V_MAY_DEF_RESULT (v_may_defs, i);
+ record_voperand_set (dse_gd->stores, &bd->stores, ann->uid);
+ dse_record_partial_aggregate_store (stmt, dse_gd);
+ return false;
+ }
+
+ /* Skip through any PHI nodes we have already seen if the PHI
+ represents the only use of this store.
- /* Find any uses in the PHI which match V_MAY_DEF and replace
- them with the appropriate V_MAY_DEF_OP. */
- for (j = 0; j < PHI_NUM_ARGS (phi); j++)
- if (v_may_def == PHI_ARG_DEF (phi, j))
- SET_PHI_ARG_DEF (phi, j, V_MAY_DEF_OP (v_may_defs, i));
+ Note this does not handle the case where the store has
+ multiple VDEFs 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
+ && bitmap_bit_p (dse_gd->stores, get_stmt_uid (*use_stmt)))
+ {
+ /* A PHI node can both define and use the same SSA_NAME if
+ the PHI is at the top of a loop and the PHI_RESULT is
+ a loop invariant and copies have not been fully propagated.
+
+ The safe thing to do is exit assuming no optimization is
+ possible. */
+ if (SSA_NAME_DEF_STMT (PHI_RESULT (*use_stmt)) == *use_stmt)
+ return false;
+
+ /* Skip past this PHI and loop again in case we had a PHI
+ chain. */
+ single_imm_use (PHI_RESULT (*use_stmt), use_p, use_stmt);
}
+
+ return true;
}
-/* Replace the V_MAY_DEF_OPs in STMT1 which match V_MAY_DEF_RESULTs
- in STMT2 with the appropriate V_MAY_DEF_OPs from STMT2. */
-static void
-fix_stmt_v_may_defs (tree stmt1, tree stmt2)
+/* Given a DECL, return its AGGREGATE_VARDECL_D entry. If no entry is
+ found and INSERT is TRUE, add a new entry. */
+
+static struct aggregate_vardecl_d *
+get_aggregate_vardecl (tree decl, struct dse_global_data *dse_gd, bool insert)
{
- stmt_ann_t ann1 = stmt_ann (stmt1);
- stmt_ann_t ann2 = stmt_ann (stmt2);
- v_may_def_optype v_may_defs1;
- v_may_def_optype v_may_defs2;
- unsigned int i, j;
-
- get_stmt_operands (stmt1);
- get_stmt_operands (stmt2);
- v_may_defs1 = V_MAY_DEF_OPS (ann1);
- v_may_defs2 = V_MAY_DEF_OPS (ann2);
-
- /* Walk each V_MAY_DEF_OP in stmt1. */
- for (i = 0; i < NUM_V_MAY_DEFS (v_may_defs1); i++)
+ struct aggregate_vardecl_d av, *av_p;
+ void **slot;
+
+ av.decl = decl;
+ slot = htab_find_slot (dse_gd->aggregate_vardecl, &av, insert ? INSERT : NO_INSERT);
+
+
+ /* Not found, and we don't want to insert. */
+ if (slot == NULL)
+ return NULL;
+
+ /* Create new entry. */
+ if (*slot == NULL)
{
- tree v_may_def1 = V_MAY_DEF_OP (v_may_defs1, i);
+ av_p = XNEW (struct aggregate_vardecl_d);
+ av_p->decl = decl;
- /* Find the appropriate V_MAY_DEF_RESULT in STMT2. */
- for (j = 0; j < NUM_V_MAY_DEFS (v_may_defs2); j++)
+ /* Record how many parts the whole has. */
+ if (TREE_CODE (TREE_TYPE (decl)) == COMPLEX_TYPE)
+ av_p->nparts = 2;
+ else if (TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE)
{
- if (v_may_def1 == V_MAY_DEF_RESULT (v_may_defs2, j))
+ tree fields;
+
+ /* Count the number of fields. */
+ fields = TYPE_FIELDS (TREE_TYPE (decl));
+ av_p->nparts = 0;
+ while (fields)
{
- /* Update. */
- SET_V_MAY_DEF_OP (v_may_defs1, i, V_MAY_DEF_OP (v_may_defs2, j));
- break;
+ av_p->nparts++;
+ fields = TREE_CHAIN (fields);
}
}
+ else
+ abort ();
- /* If we did not find a corresponding V_MAY_DEF_RESULT, then something
- has gone terribly wrong. */
- gcc_assert (j != NUM_V_MAY_DEFS (v_may_defs2));
+ av_p->ignore = true;
+ av_p->parts_set = sbitmap_alloc (HOST_BITS_PER_LONG);
+ sbitmap_zero (av_p->parts_set);
+ *slot = av_p;
}
+ else
+ av_p = (struct aggregate_vardecl_d *) *slot;
+
+ return av_p;
}
-/* Set bit UID in bitmaps GLOBAL and *LOCAL, creating *LOCAL as needed. */
+/* If STMT is a partial store into an aggregate, record which part got set. */
+
static void
-record_voperand_set (bitmap global, bitmap *local, unsigned int uid)
+dse_record_partial_aggregate_store (tree stmt, struct dse_global_data *dse_gd)
{
- /* Lazily allocate the bitmap. Note that we do not get a notification
- when the block local data structures die, so we allocate the local
- bitmap backed by the GC system. */
- if (*local == NULL)
- *local = BITMAP_GGC_ALLOC ();
+ tree lhs, decl;
+ enum tree_code code;
+ struct aggregate_vardecl_d *av_p;
+ int part;
+
+ gcc_assert (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT);
+
+ lhs = GIMPLE_STMT_OPERAND (stmt, 0);
+ code = TREE_CODE (lhs);
+ if (code != IMAGPART_EXPR
+ && code != REALPART_EXPR
+ && code != COMPONENT_REF)
+ return;
+ decl = TREE_OPERAND (lhs, 0);
+ /* Early bail on things like nested COMPONENT_REFs. */
+ if (TREE_CODE (decl) != VAR_DECL)
+ return;
+ /* Early bail on unions. */
+ if (code == COMPONENT_REF
+ && TREE_CODE (TREE_TYPE (TREE_OPERAND (lhs, 0))) != RECORD_TYPE)
+ return;
+
+ av_p = get_aggregate_vardecl (decl, dse_gd, /*insert=*/false);
+ /* Run away, this isn't an aggregate we care about. */
+ if (!av_p || av_p->ignore)
+ return;
- /* Set the bit in the local and global bitmaps. */
- bitmap_set_bit (*local, uid);
- bitmap_set_bit (global, uid);
+ switch (code)
+ {
+ case IMAGPART_EXPR:
+ part = 0;
+ break;
+ case REALPART_EXPR:
+ part = 1;
+ break;
+ case COMPONENT_REF:
+ {
+ tree orig_field, fields;
+ tree record_type = TREE_TYPE (TREE_OPERAND (lhs, 0));
+
+ /* Get FIELD_DECL. */
+ orig_field = TREE_OPERAND (lhs, 1);
+
+ /* FIXME: Eeech, do this more efficiently. Perhaps
+ calculate bit/byte offsets. */
+ part = -1;
+ fields = TYPE_FIELDS (record_type);
+ while (fields)
+ {
+ ++part;
+ if (fields == orig_field)
+ break;
+ fields = TREE_CHAIN (fields);
+ }
+ gcc_assert (part >= 0);
+ }
+ break;
+ default:
+ return;
+ }
+
+ /* Record which part was set. */
+ SET_BIT (av_p->parts_set, part);
}
-/* Initialize block local data structures. */
-static void
-dse_initialize_block_local_data (struct dom_walk_data *walk_data,
- basic_block bb ATTRIBUTE_UNUSED,
- bool recycled)
+
+/* Return TRUE if all parts in an AGGREGATE_VARDECL have been set. */
+
+static inline bool
+dse_whole_aggregate_clobbered_p (struct aggregate_vardecl_d *av_p)
{
- struct dse_block_local_data *bd
- = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
+ unsigned int i;
+ sbitmap_iterator sbi;
+ int nbits_set = 0;
- /* If we are given a recycled block local data structure, ensure any
- bitmap associated with the block is cleared. */
- if (recycled)
+ /* Count the number of partial stores (bits set). */
+ EXECUTE_IF_SET_IN_SBITMAP (av_p->parts_set, 0, i, sbi)
+ nbits_set++;
+ return ((unsigned) nbits_set == av_p->nparts);
+}
+
+
+/* Return TRUE if STMT is a store into a whole aggregate whose parts we
+ have already seen and recorded. */
+
+static bool
+dse_partial_kill_p (tree stmt, struct dse_global_data *dse_gd)
+{
+ tree decl;
+ struct aggregate_vardecl_d *av_p;
+
+ /* Make sure this is a store into the whole. */
+ if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
{
- if (bd->stores)
- bitmap_clear (bd->stores);
+ enum tree_code code;
+
+ decl = GIMPLE_STMT_OPERAND (stmt, 0);
+ code = TREE_CODE (TREE_TYPE (decl));
+
+ if (code != COMPLEX_TYPE && code != RECORD_TYPE)
+ return false;
+
+ if (TREE_CODE (decl) != VAR_DECL)
+ return false;
}
+ else
+ return false;
+
+ av_p = get_aggregate_vardecl (decl, dse_gd, /*insert=*/false);
+ gcc_assert (av_p != NULL);
+
+ return dse_whole_aggregate_clobbered_p (av_p);
}
+
/* Attempt to eliminate dead stores in the statement referenced by BSI.
A dead store is a store into a memory location which will later be
block_stmt_iterator bsi)
{
struct dse_block_local_data *bd
- = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
- struct dse_global_data *dse_gd = walk_data->global_data;
+ = (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);
- v_may_def_optype v_may_defs;
-
- get_stmt_operands (stmt);
- v_may_defs = V_MAY_DEF_OPS (ann);
- /* If this statement has no virtual uses, then there is nothing
+ /* If this statement has no virtual defs, then there is nothing
to do. */
- if (NUM_V_MAY_DEFS (v_may_defs) == 0)
+ if (ZERO_SSA_OPERANDS (stmt, SSA_OP_VDEF))
return;
- /* We know we have virtual definitions. If this is a MODIFY_EXPR that's
- not also a function call, then record it into our table. */
+ /* We know we have virtual definitions. If this is a GIMPLE_MODIFY_STMT
+ that's not also a function call, then record it into our table. */
if (get_call_expr_in (stmt))
return;
if (ann->has_volatile_ops)
return;
- if (TREE_CODE (stmt) == MODIFY_EXPR)
+ if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
{
- dataflow_t df = get_immediate_uses (stmt);
- unsigned int num_uses = num_immediate_uses (df);
- tree use;
- tree skipped_phi;
-
-
- /* If there are no uses then there is nothing left to do. */
- if (num_uses == 0)
- {
- record_voperand_set (dse_gd->stores, &bd->stores, ann->uid);
- return;
- }
-
- use = immediate_use (df, 0);
- skipped_phi = NULL;
-
- /* Skip through any PHI nodes we have already seen if the PHI
- 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
- same block. */
- while (num_uses == 1
- && TREE_CODE (use) == PHI_NODE
- && bitmap_bit_p (dse_gd->stores, get_stmt_uid (use)))
- {
- /* Record the first PHI we skip so that we can fix its
- uses if we find that STMT is a dead store. */
- if (!skipped_phi)
- skipped_phi = use;
-
- /* Skip past this PHI and loop again in case we had a PHI
- chain. */
- df = get_immediate_uses (use);
- num_uses = num_immediate_uses (df);
- use = immediate_use (df, 0);
- }
-
- /* If we have precisely one immediate use at this point, then we may
- have found redundant store. */
- if (num_uses == 1
- && bitmap_bit_p (dse_gd->stores, get_stmt_uid (use))
- && operand_equal_p (TREE_OPERAND (stmt, 0),
- TREE_OPERAND (use, 0), 0))
+ use_operand_p first_use_p = NULL_USE_OPERAND_P;
+ use_operand_p use_p = NULL;
+ tree use_stmt;
+
+ if (!dse_possible_dead_store_p (stmt, &first_use_p, &use_p, &use_stmt,
+ dse_gd, bd))
+ return;
+
+ /* If this is a partial store into an aggregate, record it. */
+ dse_record_partial_aggregate_store (stmt, dse_gd);
+
+ 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)
+ && !dse_partial_kill_p (stmt, dse_gd))
+ && 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_use_of_stmt_lhs (stmt, &first_use_p, &use_p, &use_stmt) ==
+ NULL_TREE)
+ {
+ record_voperand_set (dse_gd->stores, &bd->stores, ann->uid);
+ 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)
+ || dse_partial_kill_p (stmt, dse_gd))
+ && memory_address_same (stmt, use_stmt))
{
- /* We need to fix the operands if either the first PHI we
- skipped, or the store which we are not deleting if we did
- not skip any PHIs. */
- if (skipped_phi)
- fix_phi_uses (skipped_phi, stmt);
- else
- fix_stmt_v_may_defs (use, stmt);
+ ssa_op_iter op_iter;
+ def_operand_p var1;
+ vuse_vec_p vv;
+ tree stmt_lhs;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "'\n");
}
- /* Any immediate uses which reference STMT need to instead
- reference the new consumer, either SKIPPED_PHI or USE.
- This allows us to cascade dead stores. */
- redirect_immediate_uses (stmt, skipped_phi ? skipped_phi : use);
+ /* 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;
+ }
- /* Be sure to remove any dataflow information attached to
- this statement. */
- free_df_for_stmt (stmt);
+ /* Remove the dead store. */
+ bsi_remove (&bsi, true);
/* And release any SSA_NAMEs set in this statement back to the
SSA_NAME manager. */
release_defs (stmt);
-
- /* Finally remove the dead store. */
- bsi_remove (&bsi);
}
record_voperand_set (dse_gd->stores, &bd->stores, ann->uid);
dse_record_phis (struct dom_walk_data *walk_data, basic_block bb)
{
struct dse_block_local_data *bd
- = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
- struct dse_global_data *dse_gd = walk_data->global_data;
+ = (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;
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));
basic_block bb ATTRIBUTE_UNUSED)
{
struct dse_block_local_data *bd
- = VARRAY_TOP_GENERIC_PTR (walk_data->block_data_stack);
- struct dse_global_data *dse_gd = walk_data->global_data;
+ = (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;
bitmap stores = dse_gd->stores;
unsigned int i;
bitmap_iterator bi;
}
}
+
+/* Hashing and equality functions for AGGREGATE_VARDECL. */
+
+static hashval_t
+aggregate_vardecl_hash (const void *p)
+{
+ return htab_hash_pointer
+ ((const void *)((const struct aggregate_vardecl_d *)p)->decl);
+}
+
+static int
+aggregate_vardecl_eq (const void *p1, const void *p2)
+{
+ return ((const struct aggregate_vardecl_d *)p1)->decl
+ == ((const struct aggregate_vardecl_d *)p2)->decl;
+}
+
+
+/* Free memory allocated by one entry in AGGREGATE_VARDECL. */
+
static void
+aggregate_vardecl_free (void *p)
+{
+ struct aggregate_vardecl_d *entry = (struct aggregate_vardecl_d *) p;
+ sbitmap_free (entry->parts_set);
+ free (entry);
+}
+
+
+/* Return true if STMT is a store into an entire aggregate. */
+
+static bool
+aggregate_whole_store_p (tree stmt)
+{
+ if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
+ {
+ tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
+ enum tree_code code = TREE_CODE (TREE_TYPE (lhs));
+
+ if (code == COMPLEX_TYPE || code == RECORD_TYPE)
+ return true;
+ }
+ return false;
+}
+
+
+/* Main entry point. */
+
+static unsigned int
tree_ssa_dse (void)
{
struct dom_walk_data walk_data;
struct dse_global_data dse_gd;
basic_block bb;
- /* Create a UID for each statement in the function. Ordering of the
- UIDs is not important for this pass. */
+ dse_gd.aggregate_vardecl =
+ htab_create (37, aggregate_vardecl_hash,
+ aggregate_vardecl_eq, aggregate_vardecl_free);
+
max_stmt_uid = 0;
FOR_EACH_BB (bb)
{
block_stmt_iterator bsi;
for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
- stmt_ann (bsi_stmt (bsi))->uid = max_stmt_uid++;
+ {
+ tree stmt = bsi_stmt (bsi);
+
+ /* Record aggregates which have been stored into as a whole. */
+ if (aggregate_whole_store_p (stmt))
+ {
+ tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
+ if (TREE_CODE (lhs) == VAR_DECL)
+ {
+ struct aggregate_vardecl_d *av_p;
+
+ av_p = get_aggregate_vardecl (lhs, &dse_gd, /*insert=*/true);
+ av_p->ignore = false;
+
+ /* Ignore aggregates with too many parts. */
+ if (av_p->nparts > HOST_BITS_PER_LONG)
+ av_p->ignore = true;
+ }
+ }
+
+ /* Create a UID for each statement in the function.
+ Ordering of the UIDs is not important for this pass. */
+ stmt_ann (stmt)->uid = max_stmt_uid++;
+ }
}
/* We might consider making this a property of each pass so that it
dominators. */
calculate_dominance_info (CDI_POST_DOMINATORS);
- /* We also need immediate use information for virtual operands. */
- compute_immediate_uses (TDFA_USE_VOPS, need_imm_uses_for);
-
/* 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.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.block_local_data_size = sizeof (struct dse_block_local_data);
/* This is the main hash table for the dead store elimination pass. */
- dse_gd.stores = BITMAP_XMALLOC ();
+ dse_gd.stores = BITMAP_ALLOC (NULL);
+
walk_data.global_data = &dse_gd;
/* Initialize the dominator walker. */
/* Finalize the dominator walker. */
fini_walk_dominator_tree (&walk_data);
- /* Release the main bitmap. */
- BITMAP_XFREE (dse_gd.stores);
-
- /* Free dataflow information. It's probably out of date now anyway. */
- free_df ();
+ /* Release unneeded data. */
+ BITMAP_FREE (dse_gd.stores);
+ htab_delete (dse_gd.aggregate_vardecl);
/* For now, just wipe the post-dominator information. */
free_dominance_info (CDI_POST_DOMINATORS);
+ return 0;
}
static bool
NULL, /* next */
0, /* static_pass_number */
TV_TREE_DSE, /* tv_id */
- PROP_cfg | PROP_ssa
+ PROP_cfg
+ | PROP_ssa
| PROP_alias, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_ggc_collect /* todo_flags_finish */
- | TODO_verify_ssa,
- 0 /* letter */
+ TODO_dump_func
+ | TODO_ggc_collect
+ | TODO_verify_ssa, /* todo_flags_finish */
+ 0 /* letter */
};