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Re: contribution
- From: Andi Kleen <ak at suse dot de>
- To: Toon Moene <moene at knmi dot nl>
- Cc: gcc at gcc dot gnu dot org, starlex at eng dot sun dot com
- Date: 12 Apr 2002 14:45:47 +0200
- Subject: Re: contribution
- References: <3CB6D448.45A4FE3E@knmi.nl.suse.lists.egcs>
Toon Moene <moene@knmi.nl> writes:
> Andi Kleen wrote:
>
> > Alexey Starovoytov <starlex@eng.sun.com> writes:
>
> >> For example SPECfp benchmark 172.mgrid showed 48% improvement
> >> compiled with "-O2 -Ws,-O2,-fno-strict-aliasing" vs plain GCC
> >> with "-O2"
>
> > You could compiled 172.mgrid with gcc twice this way and it showed
> > 48% improvement ? Or did you use a different compiler as backend?
> > If you used gcc - is it known where that huge difference comes
> > from?
>
> A more important aspect of such a compiler would be idempotency.
>
> I.e., is
>
> gcc(gcc(x.c)) = gcc(x.c)
>
> ?
To be honest I don't believe that he got that result with multiple runs
of gcc. If yes that would be a very bad bug in the optimizer. More likely
it was reached with the proprietary Sun compiler as backend (that would
make the patch more a porting tool for GNU C programs to Sun C)
-Andi