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Re: GCC optimizes integer overflow: bug or feature?
- From: Andrew Pinski <pinskia at gmail dot com>
- To: Robert Dewar <dewar at adacore dot com>
- Cc: Dave Korn <dave dot korn at artimi dot com>, 'Denis Vlasenko' <vda dot linux at googlemail dot com>, 'Paul Brook' <paul at codesourcery dot com>, gcc at gcc dot gnu dot org, 'Andrew Haley' <aph at redhat dot com>, 'Paolo Bonzini' <bonzini at gnu dot org>, bug-gnulib at gnu dot org
- Date: Fri, 22 Dec 2006 09:36:30 -0800
- Subject: Re: GCC optimizes integer overflow: bug or feature?
- References: <005101c725eb$bce0a650$a501a8c0@CAM.ARTIMI.COM> <1166807835.31053.4.camel@celery.andrew.com> <458C1649.3050303@adacore.com>
On Fri, 2006-12-22 at 12:30 -0500, Robert Dewar wrote:
>
> > Maybe on x86, but on PPC, at least for the (current) Cell's PPU
> > misaligned accesses for most cases unaligned are optimal.
>
> is that true across cache boundaries?
For Cell, crossing the 32byte boundary causes the microcode to happen.
But the question is how often does that happen compare to non crossing,
I am willing to bet hardly at all, yes I need to test this and I am
going to have anyways for my job :).
-- Pinski