`Location::caller` calls an intrinsic: 
```rust
    #[must_use]
    #[stable(feature = "track_caller", since = "1.46.0")]
    #[rustc_const_stable(feature = "const_caller_location", since = "1.79.0")]
    #[track_caller]
    #[inline]
    pub const fn caller() -> &'static Location<'static> {
        crate::intrinsics::caller_location()
    }

0010fe48 <core::panic::location::Location::caller::h73de69a832e488f3>:
;     pub const fn caller() -> &'static Location<'static> {
  10fe48: e24dd004     	sub	sp, sp, #4
;         crate::intrinsics::caller_location()
  10fe4c: e58d0000     	str	r0, [sp]
  10fe50: e59d0000     	ldr	r0, [sp]
;     }
  10fe54: e28dd004     	add	sp, sp, #4
  10fe58: e12fff1e     	bx	lr


```

I could not find source code for the intrinsic so far