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Re: SPECfp95: Huge performance loss with -fnew-ra?
- From: Daniel Berlin <dberlin at dberlin dot org>
- To: Diego Novillo <dnovillo at redhat dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Mon, 22 Jul 2002 22:04:05 -0400 (EDT)
- Subject: Re: SPECfp95: Huge performance loss with -fnew-ra?
On Mon, 22 Jul 2002, Diego Novillo wrote:
> I started using "-O2 -fnew-ra" for SPEC95 peak runs. The flag
> seems to have had a negligible effect on SPECint, but on SPECfp
> we have lost 4 SPEC marks (about 25% performance loss).
>
> http://people.redhat.com/dnovillo/SPEC/gcc/global-run-ratio.html
>
> I am not sure at the moment if it's the new register allocator by
> itself or some combination of -fnew-ra and some other change.
No, it's the new-ra, i'm sure.
In particular, Michael, the GENERAL_REGS change you mad (instead
of the old ALL_REGS) guarantees we'll always spill float_regs, since at
least on x86, it doesn't include them.
You'll note the severe drop was 07-21, and the diffs for the day include
the GENERAL_REGS change.
>
> The first run with the new allocator was on 2002-07-17.
>
>
> Diego.
>
>