Comment by jonstewart

One reason to move conditionals out of loops is that it makes it easier for the compiler to vectorize and otherwise optimize the loop.

With conditionals, it's also useful to express them as ternary assignment when possible. This makes it more likely the optimizer will generate a conditional move instead of a branch. When the condition is not sufficiently predictable, a conditional move is far faster due to branch misprediction. Sometimes it's not always faster in the moment, but it can still alleviate pressure on the branch prediction cache.