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Subject: [Bug tree-optimization/95731] Failure to optimize a >= 0 && b >= 0
 to (a | b) >= 0
Date: Tue, 12 Jan 2021 10:05:54 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95731

--- Comment #6 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:13d47c37a2c043f3e5981e73e4c82158a39f41e8

commit r11-6609-g13d47c37a2c043f3e5981e73e4c82158a39f41e8
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Jan 12 11:03:40 2021 +0100

    reassoc: Optimize in reassoc x < 0 && y < 0 to (x | y) < 0 etc. [PR9573=
1]

    We already had x !=3D 0 && y !=3D 0 to (x | y) !=3D 0 and
    x !=3D -1 && y !=3D -1 to (x & y) !=3D -1 and
    x < 32U && y < 32U to (x | y) < 32U, this patch adds signed
    x < 0 && y < 0 to (x | y) < 0.  In that case, the low/high seem to be
    always the same and just in_p indices whether it is >=3D 0 or < 0,
    also, all types in the same bucket (same precision) should be type
    compatible, but we can have some >=3D 0 and some < 0 comparison mixed,
    so the patch handles that by using the right BIT_IOR_EXPR or BIT_AND_EX=
PR
    and doing one set of < 0 or >=3D 0 first, then BIT_NOT_EXPR and then the
other
    one.  I had to move optimize_range_tests_var_bound before this optimiza=
tion
    because that one deals with signed a >=3D 0 && a < b, and limited it to=
 the
    last reassoc pass as reassoc itself can't virtually undo this optimizat=
ion
    yet (and not sure if vrp would be able to).

    2021-01-12  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/95731
            * tree-ssa-reassoc.c (optimize_range_tests_cmp_bitwise): Also
optimize
            x < 0 && y < 0 && z < 0 into (x | y | z) < 0 for signed x, y, z.
            (optimize_range_tests): Call optimize_range_tests_cmp_bitwise
            only after optimize_range_tests_var_bound.

            * gcc.dg/tree-ssa/pr95731.c: New test.
            * gcc.c-torture/execute/pr95731.c: New test.=