https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65236
--- Comment #5 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
This is the code generated for thunk:
_Z5test11A:
.LFB12:
.cfi_startproc
pushq %rbx
.cfi_def_cfa_offset 16
.cfi_offset 3, -16
movq %rdi, %rbx
subq $16, %rsp
.cfi_def_cfa_offset 32
movq %rsp, %rdi
call _Z5test21A
movq (%rsp), %rax
movq %rax, (%rbx)
movq 8(%rsp), %rax
movq %rax, 8(%rbx)
addq $16, %rsp
.cfi_def_cfa_offset 16
movq %rbx, %rax
popq %rbx
.cfi_def_cfa_offset 8
ret
which is wrong; the extra copy should not exist.
