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Date: Sat, 06 Aug 2011 22:33:54 +0200
From: Stefan Weil <weil@mail.berlios.de>
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Subject: Re: [Qemu-devel] [PATCH] TCG: fix copy propagation
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To: Blue Swirl <blauwirbel@gmail.com>
Cc: TeLeMan <geleman@gmail.com>, qemu-devel <qemu-devel@nongnu.org>, zhur@ispras.ru, Kirill Batuzov <batuzovk@ispras.ru>

Am 06.08.2011 22:13, schrieb Stefan Weil:
> Am 06.08.2011 16:06, schrieb Blue Swirl:
>> Copy propagation introduced in 22613af4a6d9602001e6d0e7b6d98aa40aa018dc
>> considered only global registers. However, register temps and stack
>> allocated locals must be handled differently because register temps
>> don't survive across brcond.
>>
>> Fix by propagating only within same class of temps.
>>
>> Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
>> ---
>> tcg/optimize.c | 13 +++++++------
>> tcg/tcg.h | 5 +++++
>> 2 files changed, 12 insertions(+), 6 deletions(-)
>>
>> diff --git a/tcg/optimize.c b/tcg/optimize.c
>> index a3bfa5e..748ecf9 100644
>> --- a/tcg/optimize.c
>> +++ b/tcg/optimize.c
>> @@ -185,12 +185,13 @@ static int op_to_movi(int op)
>> }
>> }
>>
>> -static void tcg_opt_gen_mov(TCGArg *gen_args, TCGArg dst, TCGArg src,
>> - int nb_temps, int nb_globals)
>> +static void tcg_opt_gen_mov(TCGContext *s, TCGArg *gen_args, TCGArg 
>> dst,
>> + TCGArg src, int nb_temps, int nb_globals)
>> {
>> reset_temp(dst, nb_temps, nb_globals);
>> assert(temps[src].state != TCG_TEMP_COPY);
>> - if (src >= nb_globals) {
>> + if (src >= nb_globals &&
>> + tcg_arg_is_local(s, src) == tcg_arg_is_local(s, dst)) {
>> assert(temps[src].state != TCG_TEMP_CONST);
> [snip]
>
> Hi Blue,
>
> your patch fixes qemu-system-x86_64 which now seems to work on 32 bit 
> hosts, too.
>
> qemu-system-mips64(el) still fail with the same abort. They work when 
> I remove the
> if block in tcg_opt_gen_mov.
>
> The Debian kernel for qemu-system-mips64 which I used for the test is 
> available on
> http://qemu.weilnetz.de/mips64/.
>
> I could not reproduce the crash with qemu-system-ppc64 - neither with 
> nor without
> your patch.
>
> Kind regards,
> Stefan

The patch works with qemu-system-mips64(el) after a small modification:

if (src >= nb_globals &&
     tcg_arg_is_local(s, src) && tcg_arg_is_local(s, dst)) {

Cheers,
Stefan