diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5558cc535ba1299c4ff6bdbbd58c933b84afe70a..6cb9af49ec0e723f234c80b01d4c31a40b55dd1a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,20 @@
+2003-10-17 Mostafa Hagog <mustafa@il.ibm.com>
+
+ * common.opt: Add description of the new -fgcse-las flag.
+ * flags.h (flag_gcse_las): Declaration of global flag_gcse_las.
+ * gcse.c (hash_scan_set): Handle the case of store expression and
+ insert the memory expression to the hash table, this way we make it
+ possible to discover redundant loads after stores and remove them.
+ (pre_insert_copy_insn): moved the call to update_ld_motion_stores,
+ to pre_insert_copies, it is not the correct place to call it after
+ adding stores to be in the available expression hash table.
+ (pre_insert_copies): Added the call to update_ld_motion_stores when
+ one or more copies were inserted.
+ * opts.c (common_handle_option): Handle the -fgcse-las flag.
+ * toplev.c (flag_gcse_las): Initialization of flag_gcse_las.
+
+ * doc/invoke.tex: Document new -fgcse-las flag.
+
2003-10-18 Alan Modra <amodra@bigpond.net.au>
* config/rs6000/crtsavres.asm: Correct alignment of powerpc64 code
diff --git a/gcc/common.opt b/gcc/common.opt
index 26af2806a24d318517fe3712e161ffc38762c1ea..fdf28b214259a1841b498249d4af37e526fbb73b 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -362,6 +362,10 @@ fgcse-sm
Common
Perform store motion after global common subexpression elimination
+fgcse-las
+Common
+Perform redundant load after store elimination in global common subexpression elimination
+
fgnu-linker
Common
Output GNU ld formatted global initializers
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 474c9b711c714bc3581f8abb1891e034e70c5545..fd2040034a89d61372c844b2a671f2b89d0d79ae 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -270,8 +270,8 @@ in the following sections.
-fdelayed-branch -fdelete-null-pointer-checks @gol
-fexpensive-optimizations -ffast-math -ffloat-store @gol
-fforce-addr -fforce-mem -ffunction-sections @gol
--fgcse -fgcse-lm -fgcse-sm -floop-optimize -fcrossjumping @gol
--fif-conversion -fif-conversion2 @gol
+-fgcse -fgcse-lm -fgcse-sm -fgcse-las -floop-optimize @gol
+-fcrossjumping -fif-conversion -fif-conversion2 @gol
-finline-functions -finline-limit=@var{n} -fkeep-inline-functions @gol
-fkeep-static-consts -fmerge-constants -fmerge-all-constants @gol
-fmove-all-movables -fnew-ra -fno-branch-count-reg @gol
@@ -3677,10 +3677,10 @@ also turns on the following optimization flags:
-fstrength-reduce @gol
-fcse-follow-jumps -fcse-skip-blocks @gol
-frerun-cse-after-loop -frerun-loop-opt @gol
--fgcse -fgcse-lm -fgcse-sm @gol
+-fgcse -fgcse-lm -fgcse-sm -fgcse-las @gol
-fdelete-null-pointer-checks @gol
-fexpensive-optimizations @gol
--fregmove -@gol
+-fregmove @gol
-fschedule-insns -fschedule-insns2 @gol
-fsched-interblock -fsched-spec @gol
-fcaller-saves @gol
@@ -3996,10 +3996,19 @@ Enabled by default when gcse is enabled.
@item -fgcse-sm
@opindex fgcse-sm
-When @option{-fgcse-sm} is enabled, A store motion pass is run after global common
-subexpression elimination. This pass will attempt to move stores out of loops.
-When used in conjunction with @option{-fgcse-lm}, loops containing a load/store sequence
-can be changed to a load before the loop and a store after the loop.
+When @option{-fgcse-sm} is enabled, a store motion pass is run after
+global common subexpression elimination. This pass will attempt to move
+stores out of loops. When used in conjunction with @option{-fgcse-lm},
+loops containing a load/store sequence can be changed to a load before
+the loop and a store after the loop.
+
+Enabled by default when gcse is enabled.
+
+@item -fgcse-las
+@opindex fgcse-las
+When @option{-fgcse-las} is enabled, the global common subexpression
+elimination pass eliminates redundant loads that come after stores to the
+same memory location (both partial and full redundacies).
Enabled by default when gcse is enabled.
diff --git a/gcc/flags.h b/gcc/flags.h
index 93600fbd15fdb875cb01728c5863958575cb9904..2a1a10ff679df803232f9b2e336d7c649e8fa9ff 100644
--- a/gcc/flags.h
+++ b/gcc/flags.h
@@ -675,6 +675,11 @@ extern int flag_gcse_lm;
extern int flag_gcse_sm;
+/* Nonzero if we want to perform redundant load-after-store elimination
+ in gcse. */
+
+extern int flag_gcse_las;
+
/* Perform branch target register optimization before prologue / epilogue
threading. */
diff --git a/gcc/gcse.c b/gcc/gcse.c
index 84524b37d198005b46695ac4e7d847b9ec1e9be6..3e09f02252bb9bb7168219f14186fea4f228a5cb 100644
--- a/gcc/gcse.c
+++ b/gcc/gcse.c
@@ -2205,6 +2205,49 @@ hash_scan_set (rtx pat, rtx insn, struct hash_table *table)
&& oprs_available_p (pat, tmp))))
insert_set_in_table (pat, insn, table);
}
+ /* In case of store we want to consider the memory value as avaiable in
+ the REG stored in that memory. This makes it possible to remove
+ redundant loads from due to stores to the same location. */
+ else if (flag_gcse_las && GET_CODE (src) == REG && GET_CODE (dest) == MEM)
+ {
+ unsigned int regno = REGNO (src);
+
+ /* Do not do this for constant/copy propagation. */
+ if (! table->set_p
+ /* Only record sets of pseudo-regs in the hash table. */
+ && regno >= FIRST_PSEUDO_REGISTER
+ /* Don't GCSE something if we can't do a reg/reg copy. */
+ && can_copy_p (GET_MODE (src))
+ /* GCSE commonly inserts instruction after the insn. We can't
+ do that easily for EH_REGION notes so disable GCSE on these
+ for now. */
+ && ! find_reg_note (insn, REG_EH_REGION, NULL_RTX)
+ /* Is SET_DEST something we want to gcse? */
+ && want_to_gcse_p (dest)
+ /* Don't CSE a nop. */
+ && ! set_noop_p (pat)
+ /* Don't GCSE if it has attached REG_EQUIV note.
+ At this point this only function parameters should have
+ REG_EQUIV notes and if the argument slot is used somewhere
+ explicitly, it means address of parameter has been taken,
+ so we should not extend the lifetime of the pseudo. */
+ && ((note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) == 0
+ || GET_CODE (XEXP (note, 0)) != MEM))
+ {
+ /* Stores are never anticipatable. */
+ int antic_p = 0;
+ /* An expression is not available if its operands are
+ subsequently modified, including this insn. It's also not
+ available if this is a branch, because we can't insert
+ a set after the branch. */
+ int avail_p = oprs_available_p (dest, insn)
+ && ! JUMP_P (insn);
+
+ /* Record the memory expression (DEST) in the hash table. */
+ insert_expr_in_table (dest, GET_MODE (dest), insn,
+ antic_p, avail_p, table);
+ }
+ }
}
static void
@@ -5360,7 +5403,13 @@ pre_edge_insert (struct edge_list *edge_list, struct expr **index_map)
reaching_reg <- expr
old_reg <- reaching_reg
because this way copy propagation can discover additional PRE
- opportunities. But if this fails, we try the old way. */
+ opportunities. But if this fails, we try the old way.
+ When "expr" is a store, i.e.
+ given "MEM <- old_reg", instead of adding after it
+ reaching_reg <- old_reg
+ it's better to add it before as follows:
+ reaching_reg <- old_reg
+ MEM <- reaching_reg. */
static void
pre_insert_copy_insn (struct expr *expr, rtx insn)
@@ -5395,22 +5444,38 @@ pre_insert_copy_insn (struct expr *expr, rtx insn)
else
abort ();
- old_reg = SET_DEST (set);
-
- /* Check if we can modify the set destination in the original insn. */
- if (validate_change (insn, &SET_DEST (set), reg, 0))
+ if (GET_CODE (SET_DEST (set)) == REG)
{
- new_insn = gen_move_insn (old_reg, reg);
- new_insn = emit_insn_after (new_insn, insn);
+ old_reg = SET_DEST (set);
+ /* Check if we can modify the set destination in the original insn. */
+ if (validate_change (insn, &SET_DEST (set), reg, 0))
+ {
+ new_insn = gen_move_insn (old_reg, reg);
+ new_insn = emit_insn_after (new_insn, insn);
- /* Keep register set table up to date. */
- replace_one_set (REGNO (old_reg), insn, new_insn);
- record_one_set (regno, insn);
+ /* Keep register set table up to date. */
+ replace_one_set (REGNO (old_reg), insn, new_insn);
+ record_one_set (regno, insn);
+ }
+ else
+ {
+ new_insn = gen_move_insn (reg, old_reg);
+ new_insn = emit_insn_after (new_insn, insn);
+
+ /* Keep register set table up to date. */
+ record_one_set (regno, new_insn);
+ }
}
- else
+ else /* This is possible only in case of a store to memory. */
{
+ old_reg = SET_SRC (set);
new_insn = gen_move_insn (reg, old_reg);
- new_insn = emit_insn_after (new_insn, insn);
+
+ /* Check if we can modify the set source in the original insn. */
+ if (validate_change (insn, &SET_SRC (set), reg, 0))
+ new_insn = emit_insn_before (new_insn, insn);
+ else
+ new_insn = emit_insn_after (new_insn, insn);
/* Keep register set table up to date. */
record_one_set (regno, new_insn);
@@ -5423,7 +5488,6 @@ pre_insert_copy_insn (struct expr *expr, rtx insn)
"PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
BLOCK_NUM (insn), INSN_UID (new_insn), indx,
INSN_UID (insn), regno);
- update_ld_motion_stores (expr);
}
/* Copy available expressions that reach the redundant expression
@@ -5432,7 +5496,7 @@ pre_insert_copy_insn (struct expr *expr, rtx insn)
static void
pre_insert_copies (void)
{
- unsigned int i;
+ unsigned int i, added_copy;
struct expr *expr;
struct occr *occr;
struct occr *avail;
@@ -5453,6 +5517,9 @@ pre_insert_copies (void)
expression wasn't deleted anywhere. */
if (expr->reaching_reg == NULL)
continue;
+
+ /* Set when we add a copy for that expression. */
+ added_copy = 0;
for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
{
@@ -5477,11 +5544,16 @@ pre_insert_copies (void)
BLOCK_FOR_INSN (occr->insn)))
continue;
+ added_copy = 1;
+
/* Copy the result of avail to reaching_reg. */
pre_insert_copy_insn (expr, insn);
avail->copied_p = 1;
}
}
+
+ if (added_copy)
+ update_ld_motion_stores (expr);
}
}
diff --git a/gcc/opts.c b/gcc/opts.c
index 9da64d543bb04ec79cd0dacee416340be572b0a9..8418d1a96c2e3936923537fa5ab5b68d86588696 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -1019,6 +1019,10 @@ common_handle_option (size_t scode, const char *arg,
flag_gcse_sm = value;
break;
+ case OPT_fgcse_las:
+ flag_gcse_las = value;
+ break;
+
case OPT_fgnu_linker:
flag_gnu_linker = value;
break;
diff --git a/gcc/toplev.c b/gcc/toplev.c
index e711135476ae96a8b185e842916ea2e68a30f2f9..c1a05f6e26ded1862f21e599ed4db3ec525741e7 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -697,6 +697,11 @@ int flag_gcse_lm = 1;
int flag_gcse_sm = 1;
+/* Nonzero if we want to perfrom redundant load after store elimination
+ in gcse. */
+
+int flag_gcse_las = 1;
+
/* Perform target register optimization before prologue / epilogue
threading. */
@@ -1075,6 +1080,7 @@ static const lang_independent_options f_options[] =
{"gcse", &flag_gcse, 1 },
{"gcse-lm", &flag_gcse_lm, 1 },
{"gcse-sm", &flag_gcse_sm, 1 },
+ {"gcse-las", &flag_gcse_las, 1 },
{"branch-target-load-optimize", &flag_branch_target_load_optimize, 1 },
{"branch-target-load-optimize2", &flag_branch_target_load_optimize2, 1 },
{"loop-optimize", &flag_loop_optimize, 1 },