> diff --git a/tcg/tcg.c b/tcg/tcg.c
> index c3a7f19..1133438 100644
> --- a/tcg/tcg.c
> +++ b/tcg/tcg.c
> @@ -1329,8 +1329,8 @@ static void tcg_liveness_analysis(TCGContext *s)
> the low part. The result can be optimized to a simple
> add or sub. This happens often for x86_64 guest when the
> cpu mode is set to 32 bit. */
> - if (dead_temps[args[1]]) {
> - if (dead_temps[args[0]]) {
> + if (dead_temps[args[1]] && !mem_temps[1]) {
> + if (dead_temps[args[0]] && !mem_temps[0]) {
This should be mem_temps[args[1]] and mem_temps[args[0]] I believe.
> goto do_remove;
> }
> /* Create the single operation plus nop. */
> @@ -1355,8 +1355,8 @@ static void tcg_liveness_analysis(TCGContext *s)
> nb_iargs = 2;
> nb_oargs = 2;
> /* Likewise, test for the high part of the operation dead. */
> - if (dead_temps[args[1]]) {
> - if (dead_temps[args[0]]) {
> + if (dead_temps[args[1]] && !mem_temps[1]) {
> + if (dead_temps[args[0]] && !mem_temps[0]) {
Same here.
> goto do_remove;
> }
> gen_opc_buf[op_index] = op = INDEX_op_mul_i32;
Looks like for x86_64 guest temp 0 is the env (always mem_temp), temp 1 -
cc_op. As a result it can accidentally remove high part of operation
when it is actually alive but will never optimize out whole operation
even if its output is really dead.
I've attached a small patch to fix this issue.
I was not able to boot gentoo install CD (amd64) with current trunk.
Boot process hangs soon after framebuffer initialization. With the patch
it boots successfully. Command line to reproduce:
qemu-system-x86_64 -cdrom install-amd64-minimal-20121013.iso
--
Kirill Batuzov
From 33e1fc03934cebea8d32c98ea34961c80f05d94a Mon Sep 17 00:00:00 2001
From: Kirill Batuzov <batuz...@ispras.ru>
Date: Wed, 7 Nov 2012 15:26:38 +0400
Subject: [PATCH] tcg: properly check that op's output needs to be synced to
memory
Fix typo introduced in b3a1be87bac3a6aaa59bb88c1410f170dc9b22d5.
Reported-by: Ruslan Savchenko <ruslan.savche...@gmail.com>
Signed-off-by: Kirill Batuzov <batuz...@ispras.ru>
---
tcg/tcg.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/tcg/tcg.c b/tcg/tcg.c
index 42052db..35fba50 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -1337,8 +1337,8 @@ static void tcg_liveness_analysis(TCGContext *s)
the low part. The result can be optimized to a simple
add or sub. This happens often for x86_64 guest when the
cpu mode is set to 32 bit. */
- if (dead_temps[args[1]] && !mem_temps[1]) {
- if (dead_temps[args[0]] && !mem_temps[0]) {
+ if (dead_temps[args[1]] && !mem_temps[args[1]]) {
+ if (dead_temps[args[0]] && !mem_temps[args[0]]) {
goto do_remove;
}
/* Create the single operation plus nop. */
@@ -1363,8 +1363,8 @@ static void tcg_liveness_analysis(TCGContext *s)
nb_iargs = 2;
nb_oargs = 2;
/* Likewise, test for the high part of the operation dead. */
- if (dead_temps[args[1]] && !mem_temps[1]) {
- if (dead_temps[args[0]] && !mem_temps[0]) {
+ if (dead_temps[args[1]] && !mem_temps[args[1]]) {
+ if (dead_temps[args[0]] && !mem_temps[args[0]]) {
goto do_remove;
}
gen_opc_buf[op_index] = op = INDEX_op_mul_i32;
--
1.7.9.5