[the8472]

Afaik there's no guarantee that the compiler won't perform such changes. Even if it happens to generate the expected instructions today it could change with the next compiler release.

I think on some x86 cpu tuning levels this can happen around 1bit integers (aka bools) when the cost model says it's cheaper for whatever reason

   (carry: bool, c: u64) = a.carrying_add(b)
   d += carry as u64

could be turned into

   (carry: bool, c: u64) = a.carrying_add(b)
   if carry
     d += 1

And I recall doing some bittwiddling to get something like a cmov but the compiler recognized the pattern and turned it back into a branch (this was for performance optimization, not crypto, but still...)