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Subject: [Bug tree-optimization/94802] Failure to recognize identities with
 __builtin_clz
Date: Tue, 05 Jan 2021 18:14:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94802

--- Comment #11 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:5de7bf5bc98ec9edc6838a443521204d0eca7605

commit r11-6482-g5de7bf5bc98ec9edc6838a443521204d0eca7605
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Jan 5 19:13:29 2021 +0100

    expand: Fold x - y < 0 to x < y during expansion [PR94802]

    My earlier patch to simplify x - y < 0 etc. for signed subtraction
    with undefined overflow into x < y in match.pd regressed some tests,
    even when it was guarded to be post-IPA, the following patch thus
    attempts to optimize that during expansion instead (which is the last
    time we can do it, afterwards we lose the information whether it was
    x - y < 0 or (int) ((unsigned) x - y) < 0 for which we couldn't
    optimize it.

    2021-01-05  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/94802
            * expr.h (maybe_optimize_sub_cmp_0): Declare.
            * expr.c: Include tree-pretty-print.h and flags.h.
            (maybe_optimize_sub_cmp_0): New function.
            (do_store_flag): Use it.
            * cfgexpand.c (expand_gimple_cond): Likewise.

            * gcc.target/i386/pr94802.c: New test.
            * gcc.dg/Wstrict-overflow-25.c: Remove xfail.=