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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/99956] loop interchange fails when altering
 bwaves inner loop
Date: Wed, 07 Apr 2021 12:28:24 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99956

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amker at gcc dot gnu.org
           Keywords|                            |missed-optimization

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
prepare_perfect_loop_nest fails doing compute_access_strides and I wonder if
we should do prepare_data_references data-ref analysis with respect to the
BBs containing loop and only after collecting all datarefs instantiate
the access fns up to the outermost loop possible.

I don't remember exactly how we deal with this but it looks like
compute_access_stride doesn't look at the access function as computed by
dataref analysis but instead it analyzes things itself and could in theory
instantiate_scev one-loop-at-a-time communicating "failure" upwards?=