[Bug tree-optimization/120164] GCC fails vectorization when using conditional __builtin_prefetch

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120164

--- Comment #11 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tamar Christina <tnfchris@gcc.gnu.org>:

https://gcc.gnu.org/g:eae54dd6e4cc69b4c86521f501339ef9fe0eab3f

commit r17-840-geae54dd6e4cc69b4c86521f501339ef9fe0eab3f
Author: Tamar Christina <tamar.christina@arm.com>
Date:   Wed May 27 14:31:49 2026 +0100

    vect: drop prefetches during if-cvt [PR120164]

    PR114061 added support for dropping prefetches during vectorization but
that
    version doesn't work when the prefetch is conditional.

    The conditionality introduces a non-if-convertible block in the CFG.  The
    vectorizer removes the prefetch later on but it can't modify the CFG and as
    such the block where the prefetch was in remains with just a VUSEs chain.

    This change now drops them during if-conversion.  While this patch at the
moment
    removes them, it makes it easier for later on, should we want to start
    vectorizing these instead to just update predicate_statements.

    For now this follows the same approach as PR114061 and just drops them.

    gcc/ChangeLog:

            PR tree-optimization/120164
            * tree-if-conv.cc (if_convertible_stmt_p): Detect prefetches.
            (predicate_statements): Drop them during predication.

    gcc/testsuite/ChangeLog:

            PR tree-optimization/120164
            * gcc.dg/vect/vect-prefetch-drop_2.c: New test.