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SubjectRe: [patch 13/17] Immediate Values - x86 Optimization (updated)
Mathieu Desnoyers wrote:
>
> Hrm, since even the nmi-safe version supports REX-prefixed instructions,
> there is no need for an =q constraint on single-byte immediate values
> anymore. (thanks to your "discard" section used in the nmi-safe version)
>

WRONG!

Using =r for single-byte values is incorrect for 32-bit code -- that
would permit %spl, %bpl, %sil, %dil which are illegal in 32-bit mode.
That is not the incorrect bit, it's the description that is confused.

-hpa


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