It's more complicated than this, unfortunately. Imagine an int variable x and two expressions f(x) and g(x) of x. Now imagine an if statement with condition f

It's more complicated than this, unfortunately. Imagine an int variable x and two expressions f(x) and g(x) of x. Now imagine an if statement with condition f(x) < g(x). Precisely because incrementing the largest int is undefined behavior, the compiler may be able to simplify the if condition because, for example, it can assume x+1 > x is always true. So it's not necessary for the line to be useless or wrong for undefined behavior rules to trigger compiler optimizations.