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Re: GCC trunk SPEC2000 performance
- From: Janis Johnson <janis187 at us dot ibm dot com>
- To: Richard Henderson <rth at redhat dot com>, David Edelsohn <dje at watson dot ibm dot com>, Mark Mitchell <mark at codesourcery dot com>, gcc at gcc dot gnu dot org
- Date: Thu, 20 Jun 2002 12:31:17 -0700
- Subject: Re: GCC trunk SPEC2000 performance
- References: <200206200243.WAA23358@makai.watson.ibm.com> <20020620111650.B16657@redhat.com>
On Thu, Jun 20, 2002 at 11:16:50AM -0700, Richard Henderson wrote:
> On Wed, Jun 19, 2002 at 10:43:40PM -0400, David Edelsohn wrote:
> > 2) "peak" (-O3 -funroll-all-loops -fprefetch=loop-arrays) produces slower
> > code than base (-O2) for many tests.
>
> Peak cannot be considered "peak" with -funroll-all-loops
> as opposed to -funroll-loops. That forces the compiler
> to unroll a loop against its better judgement.
>
> It's good for correctness testing, however.
-fprefetch-loop-arrays needs work to actually improve most programs.
Honza's description of it for 3.1 is that it's experimental, which is
still quite accurate.
Janis