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Re: [Fwd: performance with gcc -O0/-O2]
- From: Andi Kleen <andi at firstfloor dot org>
- To: Andrew Haley <aph at redhat dot com>
- Cc: gcc at gcc dot gnu dot org, Howard Chu <hyc at highlandsun dot com>
- Date: Tue, 27 Nov 2007 16:50:53 +0100
- Subject: Re: [Fwd: performance with gcc -O0/-O2]
- References: <474C1A62.9000300@highlandsun.com.suse.lists.egcs> <18252.8713.124845.847654@zebedee.pink.suse.lists.egcs>
Andrew Haley <aph@redhat.com> writes:
> Howard Chu writes:
>
> > A bit of a minor mystery. Not a problem, just a curiosity. If
> > someone knew off the top of their head a reason for it, that'd be
> > cool, but otherwise no sweat.
>
> It's possible, although unlikley, that the optimized code has worse
> cache behaviour. No way to know better without doing some profiling.
It's quite possible if he hits the conditional store "optimization"
(that actually adds unnecessary cache misses) that was recently discussed
in the load thread safety thread.
-Andi