Yes. One of the major ways undefined behavior lets compilers optimize is by outsourcing the proofs to humans. If the compiler detects undefined behavior, it can

Yes. One of the major ways undefined behavior lets compilers optimize is by outsourcing the proofs to humans. If the compiler detects undefined behavior, it can interpret that as a guarantee that the execution path leading into that behavior cannot happen. The simplest example I can think of is code that looks like: if(x){ foo(); }else{ undefined(); } which can be optimized to foo()