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From: "rsandifo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/98986] Try matching both orders of commutative RTX operations when there is no canonical order
Date: Wed, 10 Feb 2021 12:23:04 +0000	[thread overview]
Message-ID: <bug-98986-4-NI84F8KULD@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-98986-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98986

rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rsandifo at gcc dot gnu.org

--- Comment #3 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> ---
Yeah, I think making the canonicalisation rules go deep into
the operands has scalability problems.

FWIW, another similar thing I've wanted in the past is to try
recognising multiple possible constants in an (and X (const_int N))
when X is known to have some bits clear.  Often we try to make N contain
as few bits as possible, but that can give worse results than a fuller mask.

I had a WIP patch for this and binary order thing.  It used a wrapper
around recog (in recog.c) to apply useful-looking variations.
Of course, trying multiple variations has scalability issues too,
so it would need some kind of limiter.

  parent reply	other threads:[~2021-02-10 12:23 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-07 18:07 [Bug rtl-optimization/98986] New: " ktkachov at gcc dot gnu.org
2021-02-08  9:20 ` [Bug rtl-optimization/98986] " rguenth at gcc dot gnu.org
2021-02-08 11:00 ` segher at gcc dot gnu.org
2021-02-10 12:23 ` rsandifo at gcc dot gnu.org [this message]
2021-02-10 12:27 ` rguenther at suse dot de
2021-02-10 16:53 ` segher at gcc dot gnu.org
2021-02-10 17:02 ` segher at gcc dot gnu.org

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