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Re: [Xen-devel] [PATCH] x86-32: use __builtin_{memcpy,memset}

To: Jan Beulich <JBeulich@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] x86-32: use __builtin_{memcpy,memset}
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 11 May 2010 13:04:47 +0100
Cc: Charles Arnold <CARNOLD@xxxxxxxxxx>
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On 11/05/2010 11:39, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

> Hm, well, I hate having to change this stuff as we always seem to end up
> broken on some gcc or other. But otoh this will eliminate a bunch of code if
> we do this unconditionally, and I'm particularly not keen on doing this only
> for x86-32 and particular versions of gcc. I suggest the attached patch: it
> should work fine so long as all our supported versions of gcc have
> __builtin_memcpy and __builtin_memset. Given we nowadays only support GCC
> 3.4+, I imagine we are okay in this regard.
> What do you think to this alternative patch?


What about this alternative version which distinguishes between GCC 4.3+
(which should auto-inline quite sensibly) and earlier versions (which need
help via macro mapping explicitly to __builtin_*)?

 -- Keir

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