It does. This is bread-and-butter peep-hole optimisation stuff. i.e. it actually gets "optimised" to have no modulus call even without any optimisations on, e.g.

```rust
#[crate_type="lib"];

#[no_mangle]
pub fn parity(n: uint) -> bool {
    n % 2 == 1
}
```

Then compiling with `rustc -S modulo.rs` (no optimisations) and trimming out the relevant section of `parity`, gives:

```asm
	andq	$1, %rax    # a bitwise and!
	cmpq	$1, %rax
	sete	%cl
```

(There's a pile of other junk from the possibility of `%` failing if the RHS is zero (this code path is removed with optimisation), and because of our poor handling of booleans.)