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[Bug tree-optimization/37312] -Os significantly faster than -O2 on test case wiht -funroll-all-loops
- From: "pinskia at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 1 Sep 2008 20:41:12 -0000
- Subject: [Bug tree-optimization/37312] -Os significantly faster than -O2 on test case wiht -funroll-all-loops
- References: <bug-37312-7834@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #5 from pinskia at gmail dot com 2008-09-01 20:41 -------
Subject: Re: -Os significantly faster than -O2 on test case
This is mostly because of extra register moves that IRA some times
introduces. There is another bug about Inline-asm and the return
register.
Sent from my iPhone
On Sep 1, 2008, at 7:36, "rguenth at gcc dot gnu dot org"
<gcc-bugzilla@gcc.gnu.org
> wrote:
>
>
> ------- Comment #4 from rguenth at gcc dot gnu dot org 2008-09-01
> 14:36 -------
> Well, now -Os -funroll-all-loops doesn't do any unrolling anymore
> while it did
> before. With -O2 you get what you ask for - unrolled loops.
>
> -funroll-all-loops isn't really a flag to be used in general.
>
>
> --
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37312
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37312