In chapter 3.2, `Why Aliasing Matters` section, is the optimize example wrong?

[adispring]

In chapter 3.2(Aliasing), Why Aliasing Matters section, is the optimize example wrong?

fn compute(input: &u32, output: &mut u32) {
    let cached_input = *input; // keep *input in a register
    if cached_input > 10 {
        *output = 2;  // x > 10 implies x > 5, so double and exit immediately
    } else if cached_input > 5 {
        *output *= 2;
    }
}

should be:

fn compute(input: &u32, output: &mut u32) {
    let cached_input = *input; // keep *input in a register
    if cached_input > 10 {
        *output *= 2;  // x > 10 implies x > 5, so double and exit immediately
    } else if cached_input > 5 {
        *output *= 2;
    }
}

or

fn compute(input: &u32, output: &mut u32) {
    let cached_input = *input; // keep *input in a register
    if cached_input > 10 {
        *output = 1;  // x > 10 implies x > 5, so double and exit immediately
    } else if cached_input > 5 {
        *output *= 2;
    }
}

[Gankra]

No it's correct. When it's > 10 we set it to 1 and then double it. The given optimization is to just replace this with setting it to 2.

It's a misleading comment, though. That should be fixed.