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[Qemu-devel] [PATCH 8/9] tcg/optimize: prefer the "op a, a, b" form for
From: |
Aurelien Jarno |
Subject: |
[Qemu-devel] [PATCH 8/9] tcg/optimize: prefer the "op a, a, b" form for commutative ops |
Date: |
Wed, 19 Sep 2012 22:00:22 +0200 |
The "op a, a, b" form is better handled on non-RISC host than the "op
a, b, a" form, so swap the arguments to this form when possible, and
when b is not a constant.
This reduces the number of generated instructions by a tiny bit.
Signed-off-by: Aurelien Jarno <address@hidden>
---
tcg/optimize.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/tcg/optimize.c b/tcg/optimize.c
index 6e2a37d..3495b7a 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -432,7 +432,10 @@ static TCGArg *tcg_constant_folding(TCGContext *s,
uint16_t *tcg_opc_ptr,
CASE_OP_32_64(eqv):
CASE_OP_32_64(nand):
CASE_OP_32_64(nor):
- if (temps[args[1]].state == TCG_TEMP_CONST) {
+ /* Prefer the constant in second argument, and then the form
+ op a, a, b, which is better handled on non-RISC hosts. */
+ if (temps[args[1]].state == TCG_TEMP_CONST || (args[0] == args[2]
+ && temps[args[2]].state != TCG_TEMP_CONST)) {
tmp = args[1];
args[1] = args[2];
args[2] = tmp;
--
1.7.10.4
- [Qemu-devel] [PATCH 1/9] tcg/optimizer: remove TCG_TEMP_ANY, (continued)
- [Qemu-devel] [PATCH 7/9] tcg/optimize: further optimize brcond/setcond, Aurelien Jarno, 2012/09/19
- [Qemu-devel] [PATCH 8/9] tcg/optimize: prefer the "op a, a, b" form for commutative ops,
Aurelien Jarno <=
- [Qemu-devel] [PATCH 3/9] tcg/optimizer: rework copy progagation, Aurelien Jarno, 2012/09/19
- [Qemu-devel] [PATCH 5/9] tcg/optimize: optimize "op r, a, a => mov r, a", Aurelien Jarno, 2012/09/19
- Re: [Qemu-devel] [PATCH 0/9] tcg/optimize: rework copy propagation, Laurent Desnogues, 2012/09/21