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tcg: don't keep dead outputs in registers 

If an op with dead outputs is not removed, because it has side effects
or has multiple output and only one dead, mark the registers as dead
instead of saving them. This avoid a few register spills on TCG targets
with low register count, especially with div2 and mul2 ops, or when a
qemu_ld* result is not used (prefetch emulation for example).

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Aurelien Jarno 2011-05-17 18:25:45 +02:00
parent 6b64b624cd
commit 8c11ad25f4
1 changed files with 18 additions and 10 deletions
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28
tcg/tcg.c
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@ -1782,12 +1782,16 @@ static void tcg_reg_alloc_op(TCGContext *s,
if (!ts->fixed_reg) {
if (ts->val_type == TEMP_VAL_REG)
s->reg_to_temp[ts->reg] = -1;
ts->val_type = TEMP_VAL_REG;
ts->reg = reg;
/* temp value is modified, so the value kept in memory is
potentially not the same */
ts->mem_coherent = 0;
s->reg_to_temp[reg] = arg;
if (IS_DEAD_ARG(i)) {
ts->val_type = TEMP_VAL_DEAD;
} else {
ts->val_type = TEMP_VAL_REG;
ts->reg = reg;
/* temp value is modified, so the value kept in memory is
potentially not the same */
ts->mem_coherent = 0;
s->reg_to_temp[reg] = arg;
}
}
oarg_end:
new_args[i] = reg;
@ -1981,10 +1985,14 @@ static int tcg_reg_alloc_call(TCGContext *s, const TCGOpDef *def,
} else {
if (ts->val_type == TEMP_VAL_REG)
s->reg_to_temp[ts->reg] = -1;
ts->val_type = TEMP_VAL_REG;
ts->reg = reg;
ts->mem_coherent = 0;
s->reg_to_temp[reg] = arg;
if (IS_DEAD_ARG(i)) {
ts->val_type = TEMP_VAL_DEAD;
} else {
ts->val_type = TEMP_VAL_REG;
ts->reg = reg;
ts->mem_coherent = 0;
s->reg_to_temp[reg] = arg;
}
}
}