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From: "segher at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/101523] Huge number of combine attempts
Date: Wed, 06 Mar 2024 22:49:25 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101523

--- Comment #16 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Andreas Krebbel from comment #14)
> If my analysis from comment #1 is correct, combine does superfluous steps
> here. Getting rid of this should not cause any harm, but should be
> beneficial for other targets as well. I agree that the patch I've proposed
> is kind of a hack. Do you think this could be turned into a proper fix?

When some insns have changed (or might have changed, combine does not always
know
the details), combinations of the insn with later insns are tried again.=20
Sometimes
this finds new combination opportunities.

Not retrying combinations after one of the insns has changed would be a
regression.=