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Re: [PATCH] x86: drop vex_encoding_vex2 enumerator
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Jan Beulich <jbeulich at suse dot com>
- Cc: "binutils at sourceware dot org" <binutils at sourceware dot org>
- Date: Wed, 15 Jan 2020 14:22:01 -0800
- Subject: Re: [PATCH] x86: drop vex_encoding_vex2 enumerator
- References: <c8ca9ce3-4dcc-f251-88d4-e3fb31d80f71@suse.com>
On Tue, Jan 14, 2020 at 11:42 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> Documentation clearly says "prefer {2,3}-byte VEX prefix for VEX
> instruction", as opposed to "encode with EVEX prefix" for {evex}. Hence
> there not being a way to VEX-encode an insn should not be an error (not
We can't prefer any VEX prefix on non AVX instructions:
{vex} inc %rax
should be an error.
> even a warning), and with this the separate enumerator becomes unneeded.
> (Really I'm having trouble seeing what {vex2} would be useful for when
> it's just a suggestion hint, not one allowing the programmer to mandate
> the used encoding.)
Please keep it for now. We are planning to use it in the future.
--
H.J.