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Re: [PATCH 4.8, i386]: Enable post-reload compare optimization pass (PR28685)


On Tue, Feb 7, 2012 at 11:46 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
> On Tue, Feb 7, 2012 at 11:04 AM, Richard Guenther
> <richard.guenther@gmail.com> wrote:
>
>>> (BTW: I think that the change to combine.c would be nice to have, to
>>> find more other combine opportunities. I will propose the patch
>>> separately.)
>>
>> Shouldn't there be a canonical order for parallels throughout the whole
>> compiler? ?Maybe just enforced by gen_rtx_PARALLEL / RTL checking?
>> At least as far as I understand "execution order" of insns inside a PARALLEL
>> is undefined.
>
> All operations inside parallel happen "at the same time". And there is
> no canonical order enforced, as sadly shown by the discrepancy between
> combine and compare elimination passes.

Sure - all what I say is that the fix should be to enforce such canonical
order instead of dealing with both.

Richard.

> Uros.


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