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Subject: [Bug tree-optimization/104931] [9/10/11 Regression] wrong-code with
 number_of_iterations_lt_to_ne
Date: Wed, 23 Mar 2022 14:08:08 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104931

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:d1f4dfd409dedf4d00ca7be001cf757d0d6e82f4

commit r11-9688-gd1f4dfd409dedf4d00ca7be001cf757d0d6e82f4
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Mar 16 14:53:06 2022 +0100

    tree-optimization/104931 - mitigate niter analysis issue

    The following backports a pointer associating pattern from trunk
    that mitigates an issue with number_of_iterations_lt_to_ne in
    which context we fail to fold a comparison but succeed in folding
    a related subtraction.  In the failure mode this results in
    a loop wrongly assumed looping with a bogus number of iterations,
    resulting in crashing of the premake application on start.

    With the backported simplification we are able to fold the
    comparison and correctly compute the loop as not iterating.

    I have failed to create a standalone testcase.  I belive part
    of the issue is still latent but I have failed to nail down
    the issue exactly.  Still I believe the backporting of the
    mitigation patch is the most sensible and safe thing at this
    point.

    2022-03-16  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/104931
            * match.pd ((ptr) (x p+ y) p+ z -> (ptr) (x p+ (y + z))): New
GENERIC
            simplification.=