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Re: [PATCH] x86: fix handling of 64-bit operand size VPCMPESTR{I,M}


On Tue, Feb 21, 2017 at 2:40 AM, Jan Beulich <JBeulich@suse.com> wrote:
> Just like REX.W affects operand size of the implicit rAX/rDX inputs to
> PCMPESTR{I,M}, VEX.W does for VPCMPESTR{I,M}. For that to work,
> build_vex_prefix() needs to not only honor internally specified REX
> flags (converting them to their VEX equivalents), but also such
> resulting from explicit REX* prefix uses. Also adjust
> build_evex_prefix() for consistency.

I prefer to use the "q" suffix instead of using rex64 prefix.  It will work with
both VPCMPESTR{I,M} and PCMPESTR{I,M}.

> Similarly the disassembler needs to be adjusted to no longer require
> VEX.W to be zero for the instructions to be valid.
>
> Note, however, that this doesn't address the problem of there being no
> way to control (at least) {,E}VEX.W for 32- or 16-bit code. Nor does it
> address the problem of the many WIG instructions not getting properly
> disassembled when VEX.W=1.
>




-- 
H.J.


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