[Bug target/121775] arm: wrong code in vset_lane*

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121775

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Earnshaw <rearn...@gcc.gnu.org>:

https://gcc.gnu.org/g:593e9ee05d683587c737df4fa7815a03f2c076c3

commit r16-3577-g593e9ee05d683587c737df4fa7815a03f2c076c3
Author: Richard Earnshaw <rearn...@arm.com>
Date:   Wed Sep 3 18:08:49 2025 +0100

    arm: wrong code from vset_lane_* [PR121775]

    Insufficient validation of the operands in vec_set_<mode>_internal
    means that the optimizers can transform the exanded code into
    something that is invalid.  We then emit code based on the incorrect
    RTL assuming that it is still valid.  A valid pattern can only have a
    single bit set in the immediate operand, representing the lane to be
    written.

    gcc/ChangeLog:

            PR target/121775
            * config/arm/neon.md (vec_set<mode>_internal, all variants):
            validate the immediate operand that indicates the lane to
            modify.

    gcc/testsuite/ChangeLog:

            PR target/121775
            * gcc.target/arm/simd/vset_lane_u8.c: New test.