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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/94783] Abs-equivalent pattern is not recognized as abs
Date: Fri, 08 May 2020 07:36:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94783

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:a0d732eea2e152fc51f7c5249abaa9ef56fc5121

commit r11-195-ga0d732eea2e152fc51f7c5249abaa9ef56fc5121
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri May 8 09:35:41 2020 +0200

    match.pd: Canonicalize (X + (X >> (prec - 1))) ^ (X >> (prec - 1)) to a=
bs
(X) [PR94783]

    The following patch canonicalizes M =3D X >> (prec - 1); (X + M) ^ M
    for signed integral types into ABS_EXPR (X).  For X =3D=3D min it is al=
ready
    UB because M is -1 and min + -1 is UB, so we can use ABS_EXPR rather th=
an
    say ABSU_EXPR + cast.

    The backend might then emit the abs code back using the shift and addit=
ion
    and xor if it is the best sequence for the target, but could do somethi=
ng
    different that is better.

    2020-05-08  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/94783
            * match.pd ((X + (X >> (prec - 1))) ^ (X >> (prec - 1)) to abs
(X)):
            New simplification.

            * gcc.dg/tree-ssa/pr94783.c: New test.=