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From: "hjl dot tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/36992] Very stange code for _mm_move_epi64
Date: Fri, 01 Aug 2008 13:27:00 -0000	[thread overview]
Message-ID: <20080801132542.7948.qmail@sourceware.org> (raw)
In-Reply-To: <bug-36992-682@http.gcc.gnu.org/bugzilla/>



------- Comment #7 from hjl dot tools at gmail dot com  2008-08-01 13:25 -------
(In reply to comment #6)
> with -march=core2 it uses
> 
>         movd    %xmm0, %rax
>         movq    %rax, %xmm0
>

Even this isn't necessary. We should just use

movq %xmm0,%xmm0

> with -march=opteron (and -march=generic) it uses
> 
>         movhps  .LC0(%rip), %xmm0
> 
> ISTR there is some penalty for using movq on opteron?

Opteron doesn't like inter-unit move, like

movd    %xmm0, %rax

But it isn't necessary at all. We should use

movq %xmm0,%xmm0

anyway.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36992


  parent reply	other threads:[~2008-08-01 13:27 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-08-01  3:30 [Bug target/36992] New: " hjl dot tools at gmail dot com
2008-08-01 11:59 ` [Bug target/36992] " rguenth at gcc dot gnu dot org
2008-08-01 12:05 ` rguenth at gcc dot gnu dot org
2008-08-01 12:08 ` rguenth at gcc dot gnu dot org
2008-08-01 12:54 ` hjl dot tools at gmail dot com
2008-08-01 12:57 ` hjl dot tools at gmail dot com
2008-08-01 13:22 ` rguenth at gcc dot gnu dot org
2008-08-01 13:27 ` hjl dot tools at gmail dot com [this message]
2008-08-01 19:34 ` ubizjak at gmail dot com
2008-08-02 13:10 ` ubizjak at gmail dot com
2008-08-02 13:11 ` ubizjak at gmail dot com
2008-08-02 13:23 ` ubizjak at gmail dot com
2008-08-02 15:08 ` ubizjak at gmail dot com
2008-08-02 15:20 ` hjl dot tools at gmail dot com
2008-08-02 16:03 ` ubizjak at gmail dot com
2008-08-02 18:45 ` ubizjak at gmail dot com
2008-08-03  6:15 ` uros at gcc dot gnu dot org
2008-08-03  6:50 ` ubizjak at gmail dot com
2008-08-05 14:20 ` hjl dot tools at gmail dot com
2008-08-05 17:35 ` hjl dot tools at gmail dot com
2008-08-05 17:42 ` hjl at gcc dot gnu dot org
2008-08-07 13:18 ` hjl at gcc dot gnu dot org
2008-08-07 13:19 ` hjl dot tools at gmail dot com

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