From: Richard Biener <richard.guenther@gmail.com>
To: Uros Bizjak <ubizjak@gmail.com>
Cc: gcc-patches@gcc.gnu.org, Xinliang David Li <davidxl@google.com>
Subject: Re: [PATCH i386]: Enable push/pop in pro/epilogue for modern CPUs
Date: Mon, 10 Dec 2012 09:23:00 -0000 [thread overview]
Message-ID: <CAFiYyc150rLk2yuiMVQAiUN+4sYJ_UsAW9L2UwVhEV1hi_6GQA@mail.gmail.com> (raw)
In-Reply-To: <CAFULd4Z4hGXfjF-VXdazsnSQpnBszLxQidaVVOsZddZx0ep69w@mail.gmail.com>
On Sun, Dec 9, 2012 at 2:50 PM, Uros Bizjak <ubizjak@gmail.com> wrote:
> Hello!
>
>> I noticed in prologue/epilogue, GCC prefers to use MOVs followed by a
>> SP adjustment instead of a sequence of pushes/pops. The preference to
>> the MOVs are good for old CPU micro-architectures (before pentium-4,
>> K10), because it breaks the data dependency. In modern
>> micro-architecture, push/pop is implemented using a mechanism called
>> stack engine. The data dependency is removed by the hardware, and
>> push/pop becomes very cheap (1 uOp, 1 cycle latency), and they are
>> smaller. There is no longer the need to avoid using them. This is
>> also what ICC does.
>
>> 2012-12-08 Xinliang David Li <davidxl@google.com>
>> * config/i386/i386.c: Eanble push/pop in pro/epilogue for moderen CPUs.
>
> s/moderen/modern
>
> OK for mainline SVN.
It's also more costly for unwind info in the prologue/epilogue. Thus, did you
measure the effect on CFI size?
Thanks,
Richard.
> Thanks,
> Uros.
next prev parent reply other threads:[~2012-12-10 9:23 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-09 13:50 Uros Bizjak
2012-12-09 17:09 ` Дмитрий Дьяченко
2012-12-10 9:23 ` Richard Biener [this message]
2012-12-10 20:42 ` Xinliang David Li
2012-12-10 21:07 ` Mike Stump
2012-12-11 9:49 ` Richard Biener
2012-12-11 17:15 ` Xinliang David Li
-- strict thread matches above, loose matches on Subject: below --
2012-12-21 7:26 Xinliang David Li
2012-12-21 8:20 ` Zamyatin, Igor
2012-12-11 22:53 Xinliang David Li
2012-12-11 23:39 ` Xinliang David Li
2012-12-12 11:00 ` Richard Biener
2012-12-08 18:13 Xinliang David Li
2012-12-12 16:37 ` Jan Hubicka
2012-12-12 17:25 ` Xinliang David Li
2012-12-12 17:34 ` Xinliang David Li
2012-12-12 18:30 ` Jan Hubicka
2012-12-12 18:37 ` Andi Kleen
2012-12-12 18:43 ` Jan Hubicka
2012-12-12 18:43 ` Andi Kleen
2012-12-13 0:16 ` Xinliang David Li
2012-12-13 0:16 ` Xinliang David Li
2012-12-13 1:19 ` Jan Hubicka
2012-12-13 6:09 ` Xinliang David Li
2012-12-13 6:21 ` Jakub Jelinek
2012-12-13 7:05 ` Xinliang David Li
2012-12-13 19:28 ` Jan Hubicka
2012-12-13 10:22 ` Richard Biener
2012-12-13 19:43 ` H.J. Lu
2012-12-13 20:26 ` Jan Hubicka
2012-12-13 20:28 ` H.J. Lu
2012-12-13 20:40 ` Jan Hubicka
2012-12-13 21:02 ` H.J. Lu
2012-12-13 21:35 ` Jan Hubicka
2012-12-20 12:13 ` Melik-adamyan, Areg
2012-12-20 14:08 ` H.J. Lu
2012-12-20 15:05 ` Jan Hubicka
2012-12-20 15:07 ` Jan Hubicka
2012-12-20 15:22 ` H.J. Lu
2012-12-21 8:28 ` Zamyatin, Igor
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