From: Laurent Desnogues <laurent.desnogues@gmail.com>
To: Avi Kivity <avi@redhat.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
Aurelien Jarno <aurelien@aurel32.net>
Subject: Re: [Qemu-devel] Re: [Qemu-commits] [COMMIT a4b18c6] tcg/x86_64: generated dec/inc instead of sub/addwhen possible
Date: Mon, 28 Sep 2009 10:21:43 +0200 [thread overview]
Message-ID: <761ea48b0909280121r13c14861y4a0a2683ffb79d2b@mail.gmail.com> (raw)
In-Reply-To: <4AC06AF0.7010300@redhat.com>
On Mon, Sep 28, 2009 at 9:51 AM, Avi Kivity <avi@redhat.com> wrote:
> On 09/27/2009 06:13 PM, Anthony Liguori wrote:
>>
>> From: Aurelien Jarno<aurelien@aurel32.net>
>>
>
> Intel recommends not using inc/dec. Since these instructions don't update
> all of the flags, they cannot be issued in parallel to previous instructions
> that do.
That's true, but I think Icache misses will cost you more than
the false dependencies; due to code size expansion in the
translation process, optimizing rules should not be obeyed
blindly. I guess this should be measured.
Laurent
next prev parent reply other threads:[~2009-09-28 8:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200909271613.n8RGDCLo020606@d01av04.pok.ibm.com>
2009-09-28 7:51 ` [Qemu-devel] Re: [Qemu-commits] [COMMIT a4b18c6] tcg/x86_64: generated dec/inc instead of sub/addwhen possible Avi Kivity
2009-09-28 8:21 ` Laurent Desnogues [this message]
2009-09-29 15:51 ` Filip Navara
2009-09-29 15:53 ` Laurent Desnogues
2009-09-29 15:55 ` Filip Navara
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