For every native code generator which is worth its salt, this shouldn't make a difference at all. Swapping the "polarity" of a condition is an extremely common transformation, which can be used for many reasons. And even if you don't have anything sophisticated, a simple peephole optimizer can get rid of the negation operation. And even if all that doesn't help: Perhaps the negation + condition are fused together in the microcode operations, depending on your CPU.