Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64()

[David Howells]

Avi Kivity <avi@xxxxxxxxxx> 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/