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Re: [PATCH] x86: Optimize VFIXUPIMM* patterns with multiple-alternative constraints
- From: Uros Bizjak <ubizjak at gmail dot com>
- To: wei dot william dot xiao at gmail dot com
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, "Lu, Hongjiu" <hongjiu dot lu at intel dot com>, "H. J. Lu" <hjl dot tools at gmail dot com>, Jeff Law <law at redhat dot com>, wei3 dot xiao at intel dot com
- Date: Wed, 7 Nov 2018 08:24:05 +0100
- Subject: Re: [PATCH] x86: Optimize VFIXUPIMM* patterns with multiple-alternative constraints
- References: <CAHFC=N=vy4bwxeBgcY=ZR8LFfAjS85Fqsy3rgnCC-5DBfujFQw@mail.gmail.com>
On Tue, Nov 6, 2018 at 11:16 AM Wei Xiao <wei.william.xiao@gmail.com> wrote:
>
> Hi maintainers,
>
> The attached patch intends to optimize VFIXUPIMM* patterns with
> multiple-alternative constraints and
> 4 patterns are combined into 2 patterns. Tested with bootstrap and
> regression tests on x86_64. No regressions.
>
> Is it OK for trunk?
I'm not convinced that this particular optimization is a good idea.
Looking at the patch, you have to add a whole bunch of substs just to
merge two pattern sets. Also, the approach diverges from established
approach of handling zero masks. The later raises maintenance costs
for no compelling reason.
I'd say to leave these patterns the way they are.
Uros.