An unknown intrinsic function was declared.
Erroneous code example:
```compile_fail,E0093
#![feature(intrinsics)]
extern "rust-intrinsic" {
fn foo(); // error: unrecognized intrinsic function: `foo`
}
fn main() {
unsafe {
foo();
}
}
```
Please check you didn't make a mistake in the function's name. All intrinsic
functions are defined in `librustc_codegen_llvm/intrinsic.rs` and in
`libcore/intrinsics.rs` in the Rust source code. Example:
```
#![feature(intrinsics)]
extern "rust-intrinsic" {
fn atomic_fence(); // ok!
}
fn main() {
unsafe {
atomic_fence();
}
}
```