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Re: 3.0 vs 3.0.1 on oopack's Max
- To: Richard Henderson <rth at redhat dot com>
- Subject: Re: 3.0 vs 3.0.1 on oopack's Max
- From: Paolo Carlini <pcarlini at rocketmail dot com>
- Date: Sat, 8 Sep 2001 02:15:53 -0700 (PDT)
- Cc: gcc at gcc dot gnu dot org
Hi and thank you very much for your feedback!
--- Richard Henderson <rth@redhat.com> wrote:
> You didn't mention how the compiler was configured,
> or what options you gave for compilation.
Well, I did mention that the options were:
-O2 -finline-limit=600
The compilers were built with a trivial:
--prefix=... --enable-languages=c,c++,f77
> The performance regression is caused by
>
> 3.0:
> > 8048912: 31 d2 xor %edx,%edx
> > 8048919: 0f 97 c2 seta %dl
> > 804891c: 85 d2 test %edx,%edx
>
> 3.0.1:
> > 8048917: 0f 97 c0 seta %al
> > 804891a: 83 e0 01 and $0x1,%eax
>
> The 3.0.1 version has a partial register stall on
> %al.
Thanks for your analysis! I'm really puzzled by the
fact that (of course!) only very safe patches went in
in the branch between 3.0.0 and 3.0.1.
Is there something else I can do for you, RTL dumps or
whatever?!?
Cheers,
Paolo.
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