[Bug tree-optimization/94043] [9 Regression] ICE in superloop_at_depth, at cfgloop.c:78

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94043

--- Comment #23 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Kewen Lin <linkw@gcc.gnu.org>:

https://gcc.gnu.org/g:a809efd70d18c079d41051dc408de5e5f86a9797

commit r9-8506-ga809efd70d18c079d41051dc408de5e5f86a9797
Author: Kewen Lin <linkw@linux.ibm.com>
Date:   Tue Mar 31 22:48:46 2020 -0500

    Fix PR94043 by making vect_live_op generate lc-phi

    As PR94043 shows, my commit r10-4524 exposed one issue in
    vectorizable_live_operation, which inserts one extra BB
    before the single exit, leading unexpected operand expansion
    and unexpected loop depth assertion.  As Richi suggested,
    this patch is to teach vectorizable_live_operation to
    generate loop closed phi for vec_lhs, it looks like:
         loop;
         # lhs' = PHI <lhs>
    =>
         loop;
         # vec_lhs' = PHI <vec_lhs>
         new_tree = BIT_FIELD_REF <vec_lhs', ...>;
         lhs' = new_tree;

    I noticed that there are some SLP cases that have same lhs
    and vec_lhs but different offsets, which can make us have
    more PHIs for the same vec_lhs there.  But I think it would
    be fine since only one of them is actually live, the others
    should be eliminated by the following dce.  So the patch
    doesn't check whether there is one phi for vec_lhs, just
    create one directly instead.

    Bootstrapped/regtested on powerpc64le-linux-gnu (LE) P8.

    Backport from mainline.

      2020-04-01  Kewen Lin  <linkw@gcc.gnu.org>

      gcc/ChangeLog

          PR tree-optimization/94043
          * tree-vect-loop.c (vectorizable_live_operation): Generate
loop-closed
          phi for vec_lhs and use it for lane extraction.

      gcc/testsuite/ChangeLog

          PR tree-optimization/94043
          * gfortran.dg/graphite/vect-pr94043.f90: New test.