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Subject: [Bug tree-optimization/105940] suggested_unroll_factor applying
 place looks wrong
Date: Tue, 14 Jun 2022 05:58:25 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105940

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Kewen Lin <linkw@gcc.gnu.org>:

https://gcc.gnu.org/g:f907cf4c07cf51863dadbe90894e2ae3382bada5

commit r13-1083-gf907cf4c07cf51863dadbe90894e2ae3382bada5
Author: Kewen Lin <linkw@linux.ibm.com>
Date:   Tue Jun 14 00:57:01 2022 -0500

    vect: Move suggested_unroll_factor applying [PR105940]

    As PR105940 shown, when rs6000 port tries to assign
    m_suggested_unroll_factor by 4 or so, there will be ICE on:

      exact_div (LOOP_VINFO_VECT_FACTOR (loop_vinfo),
                 loop_vinfo->suggested_unroll_factor);

    In function vect_analyze_loop_2, the current place of
    suggested_unroll_factor applying can't guarantee it's
    applied for all cases.  As the case shows, vectorizer
    could retry with SLP forced off, the vf is reset by
    saved_vectorization_factor which isn't applied with
    suggested_unroll_factor before.  It means it can end
    up with one vf which neglects suggested_unroll_factor.
    I think it's off design, we should move the applying
    of suggested_unroll_factor after start_over.

            PR tree-optimization/105940

    gcc/ChangeLog:

            * tree-vect-loop.cc (vect_analyze_loop_2): Move the place of
            applying suggested_unroll_factor after start_over.=