From: Paolo Bonzini <bonzini@gnu.org>
To: Ian Lance Taylor <iant@google.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: PING: PR/17236, improve long long multiply on x86 (middle-end)
Date: Thu, 06 Mar 2008 17:49:00 -0000 [thread overview]
Message-ID: <47D02E92.5090404@gnu.org> (raw)
In-Reply-To: <m363vzhiub.fsf@localhost.localdomain>
>> That said, I wonder if it might actually make sense (no, I didn't
>> think it that way, but I ask) if we do this change only in
>> local-alloc.c?
>
> I think you need to make an argument for why that would be better.
Because local-alloc.c only allocates registers with a relatively short
live range, and bumping the priority of smaller register classes would
be less disrupting.
> I'm OK with making this sort of change without a clear argument, but
> only if you're prepared to do performance testing on three or more
> primary platforms. I'm not OK with making this sort of change with
> neither an argument nor performance testing. Right now, as far as I
> know, you just have a single test case which improves.
I already had SPEC on x86 and it was neutral, except that half of SPECfp
was perturbated by the machine load. I should be able to rerun it
sometime next week. Running i386 and x86_64 would not be very different
(the RA problems are the same -- %eax/%edx for MUL/DIV and %cl for shift
counts) and I don't have access to other platforms.
So, I will try to audit other back-ends like I did for MIPS. Before
that, I will see what IRA does; maybe we don't need at all the patch.
Paolo
next prev parent reply other threads:[~2008-03-06 17:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-20 8:55 Paolo Bonzini
2008-02-21 16:00 ` Richard Guenther
2008-02-21 16:54 ` Paolo Bonzini
2008-03-05 15:40 ` Ian Lance Taylor
2008-03-06 8:29 ` Paolo Bonzini
2008-03-06 17:19 ` Ian Lance Taylor
2008-03-06 17:49 ` Paolo Bonzini [this message]
2008-03-07 0:53 ` Ian Lance Taylor
2008-03-07 8:31 ` Paolo Bonzini
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