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From: Richard Henderson <rth@twiddle.net>
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Date: Mon, 7 Sep 2015 22:13:12 -0700
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Subject: Re: [Qemu-devel] [PATCH v2 01/11] target-arm: Share all common TCG
	temporaries
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>

On 09/07/2015 09:57 AM, Peter Maydell wrote:
> On 2 September 2015 at 18:57, Richard Henderson <rth@twiddle.net> wrote:
>> This is a bug fix for aarch64.  At present, we have branches using
>> the 32-bit (translate.c) versions of cpu_[NZCV]F, but we set the flags
>> using the 64-bit (translate-a64.c) versions of cpu_[NZCV]F.  From
>> the view of the TCG code generator, these are unrelated variables.
>>
>> The bug is hard to see because we currently only read these variables
>> from branches, and upon reaching a branch TCG will first spill live
>> variables and then reload the arguments of the branch.  Since the
>> 32-bit versions were never live until reaching the branch, we'd re-read
>> the data that had just been spilled from the 64-bit versions.
>>
>> There is currently no such problem with the cpu_exclusive_* variables,
>> but there's no point in tempting fate.
>>
>> Signed-off-by: Richard Henderson <rth@twiddle.net>
>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
>
> Should this be cc:qemu-stable@nongnu.org ?

Possibly.  It's certainly low risk.


r~