{PING] [PATCH] Sign extension elimination

Leehod Baruch leehod.baruch@weizmann.ac.il
Thu Apr 20 18:08:00 GMT 2006


> On Thu, Apr 20, 2006 at 08:53:15PM +0300, Leehod Baruch wrote:
>> > On Thu, Apr 20, 2006 at 10:23:21AM -0700, Mark Mitchell wrote:
>> >> H. J. Lu wrote:
>> >> > On Thu, Apr 20, 2006 at 09:39:23AM -0700, Mark Mitchell wrote:
>> >> >> I'm not finding this discussion very illuminating.
>> >> >>
>> >> >> I'm trying to understand whether the current SEE pass is ready for
>> >> >> inclusion in the compiler.  Roger has approved it on technical
>> >> merits,
>> >> >> but HJ has raised the issue that somehow this pass is a bad thing
>> for
>> >> >> x86-64.
>> >> >
>> >> > The current SEE implemented isn't designed for x86-64 and doesn't
>> help
>> >> > x86-64 at all, if it doesn't make it worse on x86-64. But its
>> >> > infrastructure is needed for future x86-64 SEE work.
>> >>
>> >> OK.  So, then, there's no problem with incorporating the SEE
>> >> implementation, and we proceed with that.
>> >>
>> >
>> > Oh, it shouldn't be enabled for a target with any -On unless we can
>> > demonstrate it does something useful.
>> >
>> I guess you referred here to x86-64.
>
> Yes. I am curious how it performs for 32bit targets, like x86 or ppc32.
On ppc32 it is harmless but it doesn't help much either since the number
of optimization opportunities is very small.

Leehod.



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