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gcse.c (replace_one_set): New function.

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* gcse.c (replace_one_set): New function.
        (pre_insert_copy_insn): Change the order of copying
        to make copy propagation discover additional PRE opportunities.

From-SVN: r71047
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Mostafa Hagog 2003-09-04 02:10:32 +00:00 committed by Richard Henderson
parent bcfb807527
commit b885908b11
2 changed files with 46 additions and 3 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2003-09-03 Mostafa Hagog <mustafa@il.ibm.com>
* gcse.c (replace_one_set): New function.
(pre_insert_copy_insn): Change the order of copying
to make copy propagation discover additional PRE opportunities.
2003-09-03 Roger Sayle <roger@eyesopen.com>
PR optimization/11700.

43
gcc/gcse.c
View File

@ -559,6 +559,7 @@ static void alloc_reg_set_mem (int);
static void free_reg_set_mem (void);
static int get_bitmap_width (int, int, int);
static void record_one_set (int, rtx);
static void replace_one_set (int, rtx, rtx);
static void record_set_info (rtx, rtx, void *);
static void compute_sets (rtx);
static void hash_scan_insn (rtx, struct hash_table *, int);
@ -1176,6 +1177,24 @@ free_reg_set_mem (void)
obstack_free (&reg_set_obstack, NULL);
}
/* An OLD_INSN that used to set REGNO was replaced by NEW_INSN.
Update the corresponding `reg_set_table' entry accordingly.
We assume that NEW_INSN is not already recorded in reg_set_table[regno]. */
static void
replace_one_set (int regno, rtx old_insn, rtx new_insn)
{
struct reg_set *reg_info;
if (regno >= reg_set_table_size)
return;
for (reg_info = reg_set_table[regno]; reg_info; reg_info = reg_info->next)
if (reg_info->insn == old_insn)
{
reg_info->insn = new_insn;
break;
}
}
/* Record REGNO in the reg_set table. */
static void
@ -5327,7 +5346,14 @@ pre_edge_insert (struct edge_list *edge_list, struct expr **index_map)
return did_insert;
}
/* Copy the result of INSN to REG. INDX is the expression number. */
/* Copy the result of INSN to REG. INDX is the expression number.
Given "old_reg <- expr" (INSN), instead of adding after it
reaching_reg <- old_reg
it's better to do the following:
reaching_reg <- expr
old_reg <- reaching_reg
because this way copy propagation can discover additional PRE
opportunuties. */
static void
pre_insert_copy_insn (struct expr *expr, rtx insn)
@ -5337,14 +5363,25 @@ pre_insert_copy_insn (struct expr *expr, rtx insn)
int indx = expr->bitmap_index;
rtx set = single_set (insn);
rtx new_insn;
rtx new_set;
rtx old_reg;
if (!set)
abort ();
new_insn = emit_insn_after (gen_move_insn (reg, copy_rtx (SET_DEST (set))), insn);
old_reg = SET_DEST (set);
new_insn = emit_insn_after (gen_move_insn (old_reg,
reg),
insn);
new_set = single_set (new_insn);
if (!new_set)
abort();
SET_DEST (set) = reg;
/* Keep register set table up to date. */
record_one_set (regno, new_insn);
replace_one_set (REGNO (old_reg), insn, new_insn);
record_one_set (regno, insn);
gcse_create_count++;