[zrm]

> If you use `&` instead of `&&` (so that all array elements are accessed unconditionally), the optimization will happen

But then you're accessing four elements of a string that could have a strlen of less than 3. If the strlen is 1 then the short circuit case saves you because s[1] will be '\0' instead of 'e' and then you don't access elements past the end of the string. The "optimized" version is UB for short strings.

[Denvercoder9]

Yes, so that's why the compiler can't and doesn't emit the optimized version if you write the short circuited version - because it behaves differently for short strings.

[immibis]

UB doesn't exist in the processor (it does, but not here). If the compiler knows the pointer is aligned it can do the transformation.

[zrm]

For the compiler to know the pointer is aligned it would have to actually be aligned and there is no guarantee that it is.