Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64() | Date | Thu, 15 Apr 2010 09:48:12 +0100 |
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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.
David
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