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Subject: [Bug tree-optimization/94802] Failure to recognize identities with
 __builtin_clz
Date: Thu, 31 Dec 2020 10:10:11 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94802

--- Comment #3 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:d2eb616a0f7bea78164912aa438c29fe1ef5774a

commit r11-6378-gd2eb616a0f7bea78164912aa438c29fe1ef5774a
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Dec 31 11:09:26 2020 +0100

    match.pd: Add clz(X) =3D=3D 0 -> (int)X < 0 etc. simpifications [PR9480=
2]

    The following patch adds some clz simplifications.  If
    clz is 0, then the MSB of the argument is set, and if clz is prec-1, th=
en
    the argument is 1.

    2020-12-31  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/94802
            * match.pd (clz(X) =3D=3D 0 -> (int)X < 0): New simplification.
            (clz(X) =3D=3D (prec-1) -> X =3D=3D 1): Likewise.

            * gcc.dg/tree-ssa/pr94802-1.c: New test.=