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SubjectRe: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64()
On 04/15/2010 11:48 AM, David Howells wrote:
> Avi Kivity<avi@redhat.com> wrote:
>
>
>> Even if Intel processors behave that way, other processors (real and
>> emulated) use those manuals as a specification. Emulated processors are
>> unlikely to touch an undefined register, but real processors may.
>>
>> (qemu tcg appears not to touch the output)
>>
> Possibly because the AMD64 spec specifies that the destination will be
> unchanged if the source was 0.
>

Likely. But we haven't tested all current and future x86 clones, and
they may be based off the Intel documentation instead of the AMD
documentation.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.



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