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From: Marc Glisse <marc.glisse@inria.fr>
To: GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: [i386] __builtin_ia32_stmxcsr could be pure
Date: Tue, 20 Jun 2017 21:34:00 -0000	[thread overview]
Message-ID: <alpine.DEB.2.20.1706202334060.2569@stedding.saclay.inria.fr> (raw)
In-Reply-To: <alpine.DEB.2.20.1706032058510.6395@stedding.saclay.inria.fr>

Ping.

On Sat, 3 Jun 2017, Marc Glisse wrote:

> Hello,
>
> I don't think Richard's "sounds good" was meant as "ok to commit". Does an 
> x86 maintainer want to approve or criticize the patch?
>
> https://gcc.gnu.org/ml/gcc-patches/2017-05/msg02009.html
>
> On Fri, 26 May 2017, Richard Biener wrote:
>
>> On Fri, May 26, 2017 at 10:55 AM, Marc Glisse <marc.glisse@inria.fr> wrote:
>>> Hello,
>>> 
>>> glibc marks fegetround as a pure function. On x86, people tend to use
>>> _MM_GET_ROUNDING_MODE instead, which could benefit from the same. I think 
>>> it
>>> is safe, but a second opinion would be welcome.
>> 
>> Sounds good.  The important part is to keep the dependency to 
>> SET_ROUNDING_MODE
>> which is done via claiming both touch global memory.
>> 
>>> I could have handled just this builtin, but it seemed better to provide
>>> def_builtin_pure (like "const" already has) since there should be other
>>> builtins that can be marked this way (maybe the gathers?).
>> 
>> Should work for gathers.  They could even use stronger guarantees,
>> namely a fnspec with "..R" (the pointer argument is only read from 
>> directly).
>> Similarly scatter can use ".W" (the pointer argument is only written to
>> directly).
>> 
>> Richard.
>> 
>>> Bootstrap+testsuite on x86_64-pc-linux-gnu with default languages.
>>> 
>>> 2017-05-29  Marc Glisse  <marc.glisse@inria.fr>
>>> 
>>> gcc/
>>>         * config/i386/i386.c (struct builtin_isa): New field pure_p.
>>>         Reorder for compactness.
>>>         (def_builtin, def_builtin2, ix86_add_new_builtins): Handle pure_p.
>>>         (def_builtin_pure, def_builtin_pure2): New functions.
>>>         (ix86_init_mmx_sse_builtins) [__builtin_ia32_stmxcsr]: Mark as 
>>> pure.
>>> 
>>> gcc/testsuite/
>>>         * gcc.target/i386/getround.c: New file.
>>> 
>>> --
>>> Marc Glisse
>> 
>
>

-- 
Marc Glisse

  reply	other threads:[~2017-06-20 21:34 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-26  8:57 Marc Glisse
2017-05-26  9:13 ` Richard Biener
2017-06-03 19:05   ` Marc Glisse
2017-06-20 21:34     ` Marc Glisse [this message]
2017-06-21  7:43 Uros Bizjak

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