[Bug tree-optimization/99956] loop interchange fails when altering bwaves inner loop

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99956

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

https://gcc.gnu.org/g:6ff66d1ea48960fe96bb51a750c01135e65fe452

commit r12-125-g6ff66d1ea48960fe96bb51a750c01135e65fe452
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Apr 7 14:53:40 2021 +0200

    tree-optimization/99956 - improve loop interchange

    When we apply store motion and DSE manually to the bwaves kernel
    in gfortran.dg/pr81303.f loop interchange no longer happens because
    the perfect nest considered covers outer loops we cannot analyze
    strides for.  The following compensates for this by shrinking the
    nest in this analysis which was already possible but on a too coarse
    granularity.  It shares the shrinked nest with the rest of the DRs
    so the complexity overhead should be negligible.

    2021-04-07  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/99956
            * gimple-loop-interchange.cc (compute_access_stride):
            Try instantiating the access in a shallower loop nest
            if instantiating failed.
            (compute_access_strides): Pass adjustable loop_nest
            to compute_access_stride.

            * gfortran.dg/pr99956.f: New testcase.