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

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.

Uros.
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