fn generic_simd_intrinsic<'ll, 'tcx>( bx: &mut Builder<'_, 'll, 'tcx>, name: Symbol, callee_ty: Ty<'tcx>, args: &[OperandRef<'tcx, &'ll Value>], ret_ty: Ty<'tcx>, llret_ty: &'ll Type, span: Span) -> Result<&'ll Value, ()>