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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/95867] Failure to optimize successive multiplications of ___uint128_t
Date: Wed, 24 Jun 2020 14:02:36 +0000	[thread overview]
Message-ID: <bug-95867-4-IktELmlrSV@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-95867-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95867

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's done through POWI internally, I guess we could open the internal function
to also operate on integers...

As for overflow for a multiplication chain of the same operand there shouldn't
be any issue, but not sure how far we should go with signed arithmetic support
early (for the late reassoc the idea is still to set flag_wrapv = 1).

We could carefully handle some cases by ensuring to only perform
"safe" linearization and for the resulting chains adjust operand sorting
to only perform "safe" commutations (basically not sort, only optimize
trailing constants / cancellations).

  parent reply	other threads:[~2020-06-24 14:02 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-24 12:40 [Bug tree-optimization/95867] New: " gabravier at gmail dot com
2020-06-24 12:46 ` [Bug tree-optimization/95867] " gabravier at gmail dot com
2020-06-24 13:42 ` jakub at gcc dot gnu.org
2020-06-24 13:58 ` rguenth at gcc dot gnu.org
2020-06-24 14:02 ` rguenth at gcc dot gnu.org [this message]
2021-01-09 18:50 ` jakub at gcc dot gnu.org
2021-01-11  9:36 ` cvs-commit at gcc dot gnu.org
2021-01-11  9:37 ` jakub at gcc dot gnu.org

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