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Re: [PATCH v2] x86: fix handling of 64-bit operand size VPCMPESTR{I,M}
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Jan Beulich <JBeulich at suse dot com>
- Cc: Binutils <binutils at sourceware dot org>
- Date: Thu, 23 Feb 2017 07:58:17 -0800
- Subject: Re: [PATCH v2] x86: fix handling of 64-bit operand size VPCMPESTR{I,M}
- Authentication-results: sourceware.org; auth=none
- References: <58AEE65B020000780013D38E@prv-mh.provo.novell.com>
On Thu, Feb 23, 2017 at 4:40 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}. Allow Q or L suffixes on
> the instructions for AT&T mode.
>
> For Intel mode, however, suffixes aren't the preferred choice, so
> 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.
Please don't use EXISTING REX prefixes for this purpose. A new
prefix to control encoding is better, but it probably belongs to another
patch.
--
H.J.