One other advantage of signed overflow not listed here -- loop termination. Consider the following loop:
for(int i = A; i <= B; i+=4) ...
This loop can be infinite if overflow is defined, and B is less than 4 from the largest value. Checking for this is a pain (and extra code), and in practice (almost) no-one would ever mean to write this and get an infinite loop when B is close to the top of the integer range.
Special case checking for this case is a pain for various kinds of loop unrolling / peeling, and also removing empty loops if they don't contain any code (which often comes up in practice with C++ templates).
Special case checking for this case is a pain for various kinds of loop unrolling / peeling, and also removing empty loops if they don't contain any code (which often comes up in practice with C++ templates).