[Bug target/126512] ICE in copy_to_mode_reg, at explow.cc:657, mno-vsx with vec_sel builtin

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126512

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by jeevitha <jeevitha@gcc.gnu.org>:

https://gcc.gnu.org/g:8edcb1d9fbc204cb87598cddb94cc85e99b4e189

commit r17-3697-g8edcb1d9fbc204cb87598cddb94cc85e99b4e189
Author: Manjunath S Matti <mmatti@linux.ibm.com>
Date:   Sun Aug 23 10:38:02 2026 -0500

    rs6000: Fix ICE with __int128 vector built-ins and -mno-vsx [PR126512]

    The changes have been bootstrapped and regression tested on
    powerpc64le-linux and powerpc64-linux.

    V1TImode is only enabled when TARGET_VSX is set (see
    rs6000_init_hard_regno_mode_ok, where rs6000_vector_mem[V1TImode] and
    rs6000_vector_unit[V1TImode] are only set up under TARGET_VSX).
    Consequently rs6000_vector_mode_supported_p returns false for V1TImode
    with -mno-vsx, and vector_type_mode () demotes the "vector __int128"
    types to plain TImode.

    Moving these built-ins to the [vsx] stanza so they are gated on
    TARGET_VSX, which is where the corresponding V2DF/V2DI vperm/vsel/vsldoi
    built-ins already live.  We then emit a proper diagnostic instead of
    ICEing, similar to PR109932 was fixed for __builtin_pack_vector_int128:

    vec_perm and vec_sld on __int128 vectors ICEd in exactly the same way
    and are fixed by the same change. __builtin_altivec_lvx_v1ti is
    deliberately left in [altivec]: it goes through ldv_expand_builtin ()
    rather than the generic path, does not ICE, and produces semantically
    correct code with -mno-vsx.

    2026-08-23  Manjunath Matti  <mmatti@linux.ibm.com>

    gcc/ChangeLog:
            PR target/126512
            * config/rs6000/rs6000-builtins.def (__builtin_altivec_vperm_1ti,
            __builtin_altivec_vperm_1ti_uns, __builtin_altivec_vsel_1ti,
            __builtin_altivec_vsel_1ti_uns, __builtin_altivec_vsldoi_v1ti):
Move
            from the [altivec] stanza to the [vsx] stanza.

    gcc/testsuite/ChangeLog:
            PR target/126512
            * gcc.target/powerpc/pr126512.c: New test.