Invalid monomorphization of an intrinsic function was used. Erroneous code example: ```ignore (error-emitted-at-codegen-which-cannot-be-handled-by-compile_fail) #![feature(platform_intrinsics)] extern "platform-intrinsic" { fn simd_add(a: T, b: T) -> T; } fn main() { unsafe { simd_add(0, 1); } // error: invalid monomorphization of `simd_add` intrinsic } ``` The generic type has to be a SIMD type. Example: ``` #![feature(repr_simd)] #![feature(platform_intrinsics)] #[repr(simd)] #[derive(Copy, Clone)] struct i32x2(i32, i32); extern "platform-intrinsic" { fn simd_add(a: T, b: T) -> T; } unsafe { simd_add(i32x2(0, 0), i32x2(1, 2)); } // ok! ```