https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113978
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |jakub at gcc dot gnu.org
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> This is an ABI issue. I am not sure if GCC is correct or LLVM is correct.
The psABI doesn't cover that. It only talks about __m128, __m256 and __m512
types, and
as both compilers use the GNU vector_size attribute extension under the hood
for those types, that is how __attribute__((vector_size ({16,32,64}))) should
behave.
Smaller vectors (vector_size 2, 4, 8) on x86_64 are in GCC passed like __m128
(I think), larger vectors or even __m256/__m512 if AVX/AVX512 isn't supported
are classified as MEMORY like > 16 byte structures/unions.
> But basically clang/LLVM is returning in %zmm0 and %zmm1 while GCC is
> returning via memory.
There is certainly not anything in the psABI that would return something in
%zmm0/%zmm1 pair I believe.
