[Bug target/124908] [14/15/16/17 Regression] ICE when folding svld1rq_u8(svptrue_b8(), p) for -msve-vector-bits=128

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124908

--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-15 branch has been updated by Kyrylo Tkachov
<ktkachov@gcc.gnu.org>:

https://gcc.gnu.org/g:fa38f8c2e043ffddaff023174926b0a30f002033

commit r15-11331-gfa38f8c2e043ffddaff023174926b0a30f002033
Author: Kyrylo Tkachov <ktkachov@nvidia.com>
Date:   Mon Apr 20 00:56:01 2026 -0700

    aarch64: PR124908 Fix ICE in svld1rq fold with -msve-vector-bits=128

    svld1rq is a replicated-quadword load: it loads 16 bytes and
    replicates them to fill the SVE register.  When -msve-vector-bits=128
    the instruction can be folded to a normal load.

    The GIMPLE fold for svld1rq transforms the intrinsic into a 128-bit
    memory load followed by a VEC_PERM_EXPR that replicates the loaded
    value.  When VL == 128, the VEC_PERM_EXPR becomes an identity
    permutation.  The checking assertion that validates the permutation
    (can_vec_perm_const_p) fails for this degenerate case because the
    vec_perm_const hook does not recognise the cross-mode identity
    permutation (e.g. V16QI -> VNx16QI).

    Fix by detecting when the SVE vector has the same number of elements as
    the 128-bit quadword (known_eq (lhs_len, source_nelts)) and emitting a
    VIEW_CONVERT_EXPR instead of a VEC_PERM_EXPR.

    Bootstrapped and tested on aarch64-none-linux-gnu.

    Signed-off-by: Kyrylo Tkachov <ktkachov@nvidia.com>

    gcc/ChangeLog:

            PR target/124908
            * config/aarch64/aarch64-sve-builtins-base.cc
            (svld1rq_impl::fold): When the SVE vector length equals the
            quadword width, emit VIEW_CONVERT_EXPR instead of VEC_PERM_EXPR.

    gcc/testsuite/ChangeLog:

            PR target/124908
            * gcc.target/aarch64/sve/acle/general/ld1rq_2.c: New test.

    (cherry picked from commit b8ac2356c691f76c19246c4c7b94c23015b8b8aa)