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Re: [trunk<-vta] Re: [vtab] Permit coalescing of user variables


Richard Guenther <richard.guenther@gmail.com> writes:

> On Wed, Jun 3, 2009 at 9:15 PM, Alexandre Oliva <aoliva@redhat.com> wrote:
>> On Jun Â3, 2009, Richard Guenther <richard.guenther@gmail.com> wrote:
>>
>>> Btw, _is_ there really a such big effect with enabling the extra coalescing?
>>
>> I'm pretty sure I even posted SPEC results back when I first proposed
>> these changes.
>>
>> I remember there was a huge effect in compile time for some
>> machine-generated sources. ÂSurely if enabling coalescing for inlined
>> variables had such a huge effect, enabling it for non-inlined variables
>> would have an even larger effect.
>>
>> Difference in performance was nothing to write home about, but when
>> you're trying to squeeze the last bit of performance from a program,
>> losing it to debug info you're not even interested in doesn't speak well
>> of GCC.
>
> Ok, I think the tristate option may be useful then.  Can we enable
> full coalescing at -O3 then?  I'll defer to Ian to approve the patch.

I don't even understand the patch.  I don't think I should be the one to
approve it.  I don't mind if somebody else approves it, but if I'm going
to approve it I would want to see documentation with a user of the
compiler can understand.

Ian


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