[Bug target/125538] [17 Regression] ICE on aarch64 during vregs pass: unrecognizable insn with V4QI vec_duplicate

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125538

--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Artemiy Volkov <artemiyv@gcc.gnu.org>:

https://gcc.gnu.org/g:80b78b2504fba037c4edf7172712210b323dcf32

commit r17-1372-g80b78b2504fba037c4edf7172712210b323dcf32
Author: Artemiy Volkov <artemiy.volkov@arm.com>
Date:   Thu Jun 4 14:47:17 2026 +0000

    aarch64: define duplication into sub-64-bit AdvSIMD vectors [PR125538]

    This is a second attempt to deal with the ICE reported in PR125538,
    triggering when we generate a (vec_duplicate:V4QI (reg:QI)) expression
    for which we currently lack RTL support.  More specifically, this occurs
    when doing a splat of the most common element in
    aarch64_expand_vector_init_fallback () at aarch64.cc:25876.

    This is the alternative approach mentioned in the original commit message
    at [0], whereby we simply define vec_duplicate patterns for 16-bit and
32-bit
    destinations.

    Same tests are added as in [0] (a full test reduced in the comments to the
    PR, as well as some new vector constructor element combinations in
    vec_init_5.c and vec-init-23.c).

    Regtested and bootstrapped on aarch64-linux-gnu.

    [0] https://gcc.gnu.org/pipermail/gcc-patches/2026-June/719181.html

            PR target/125538

    gcc/ChangeLog:

            * config/aarch64/aarch64-simd.md
            (*aarch64_simd_dup_subvector<vcons><mode>): New insn pattern.
            (*aarch64_simd_dup_subvectorv2qiqi): Likewise.
            * config/aarch64/iterators.md (VSDUP): New mode iterator.
            (VCONS): New mode attribute.
            (vcons): Likewise.

    gcc/testsuite/ChangeLog:

            * gcc.target/aarch64/sve/vec_init_5.c: Add new 8/16-bit testcases.
            * gcc.target/aarch64/vec-init-23.c: Likewise.
            * gcc.target/aarch64/pr125538.c: New test.