[Bug tree-optimization/104307] [11 Regression] '-fcompare-debug' failure (length) w/ -mavx512f -O2

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104307

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:c81d1a061e5cfab6bd276c5be4cd6161b11e6d44

commit r11-9596-gc81d1a061e5cfab6bd276c5be4cd6161b11e6d44
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Feb 1 16:02:54 2022 +0100

    veclower: Fix up -fcompare-debug issue in expand_vector_comparison
[PR104307]

    The following testcase fails -fcompare-debug, because
expand_vector_comparison
    since r11-1786-g1ac9258cca8030745d3c0b8f63186f0adf0ebc27 sets
    vec_cond_expr_only when it sees some use other than VEC_COND_EXPR that uses
    the lhs in its condition.
    Obviously we should ignore debug stmts when doing so, e.g. by not pushing
    them to uses.
    That would be a 2 liner change, but while looking at it, I'm also worried
    about VEC_COND_EXPRs that would use the lhs in more than one operand,
    like VEC_COND_EXPR <lhs, lhs, something> or VEC_COND_EXPR <lhs, something,
lhs>
    (sure, they ought to be folded, but what if they weren't).  Because if
    something like that happens, then FOR_EACH_IMM_USE_FAST would push the same
    stmt multiple times and expand_vector_condition can return true even when
    it modifies it (for vector bool masking).
    And lastly, it seems quite wasteful to safe_push statements that will just
    cause vec_cond_expr_only = false; and break; in the second loop, both for
    cases like 1000 immediate non-VEC_COND_EXPR uses and for cases like
    999 VEC_COND_EXPRs with lhs in cond followed by a single non-VEC_COND_EXPR
    use.  So this patch only pushes VEC_COND_EXPRs there.

    2022-02-01  Jakub Jelinek  <jakub@redhat.com>

            PR middle-end/104307
            * tree-vect-generic.c (expand_vector_comparison): Don't push debug
            stmts to uses vector, just set vec_cond_expr_only to false for
            non-VEC_COND_EXPRs instead of pushing them into uses.  Treat
            VEC_COND_EXPRs that use lhs not just in rhs1, but rhs2 or rhs3 too
            like non-VEC_COND_EXPRs.

            * gcc.target/i386/pr104307.c: New test.

    (cherry picked from commit e9bf6d6b0e1d67df6dcee042fbe37ab72c3a38d7)