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Re: [Qemu-devel] 64-on-32 TCG broken
From: |
Kirill Batuzov |
Subject: |
Re: [Qemu-devel] 64-on-32 TCG broken |
Date: |
Wed, 7 Nov 2012 17:26:58 +0400 (MSK) |
User-agent: |
Alpine 2.02 (DEB 1266 2009-07-14) |
> 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
tcg-properly-check-op-s-output.patch
Description: Text Data
- Re: [Qemu-devel] 64-on-32 TCG broken,
Kirill Batuzov <=