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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103218] (a < 0) << signbit is not always optimized to a & signbitmask at the gimple level
Date: Sat, 13 Nov 2021 02:11:00 +0000	[thread overview]
Message-ID: <bug-103218-4-LhCUmhne3v@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-103218-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103218

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
There is code in fold_ternary_loc which does:
      /* A < 0 ? <sign bit of A> : 0 is simply (A & <sign bit of A>).  */

And this works as fold also does (a<0)<<N into (a<0) ? 1<<N : 0 which is not
done in match.pd for reasons.

We should just handle ((cast)(a < 0)) << signbit in match.pd.

Implementing that.

  parent reply	other threads:[~2021-11-13  2:11 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-13  1:40 [Bug tree-optimization/103218] New: " pinskia at gcc dot gnu.org
2021-11-13  1:41 ` [Bug tree-optimization/103218] " pinskia at gcc dot gnu.org
2021-11-13  1:59 ` pinskia at gcc dot gnu.org
2021-11-13  2:11 ` pinskia at gcc dot gnu.org [this message]
2021-11-13  6:47 ` pinskia at gcc dot gnu.org
2021-11-13 20:15 ` pinskia at gcc dot gnu.org
2021-11-16 15:09 ` cvs-commit at gcc dot gnu.org
2021-11-16 15:10 ` pinskia at gcc dot gnu.org

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