[Bug tree-optimization/115538] wrong-code with SLP vectorization of conversions

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115538

--- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:4931a637479aba35e35c50a86f58ecd6262bc487

commit r15-7411-g4931a637479aba35e35c50a86f58ecd6262bc487
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Feb 7 08:46:31 2025 +0100

    tree-optimization/115538 - possible wrong-code with SLP conversion

    The following fixes a latent issue where we use ranges to verify
    correctness of a vector conversion optimization.  We rely on ranges
    from 'op0' which for SLP is extracted from the representative stmt
    which does not necessarily correspond to any actual scalar operation.
    We also do not verify the range of all scalar lanes in the SLP
    operand match.  The following rectifies this, restricting the support
    to single-lane SLP nodes at this point - on branches we'd simply
    not perform this optimization with SLP.

            PR tree-optimization/115538
            * tree-vectorizer.h (vect_get_slp_scalar_def): Declare.
            * tree-vect-slp.cc (vect_get_slp_scalar_def): New helper.
            * tree-vect-generic.cc (expand_vector_conversion): Adjust.
            * tree-vect-stmts.cc (vectorizable_conversion): For SLP
            correctly look at ranges of the scalar defs of the SLP operand.
            (supportable_indirect_convert_operation): Likewise.