Comment by karatinversion

I always thought the problem with this was that the compilers do loads of these optimisations in very mundane ways. Eg if I have a

  #define FOO 17
  void bar(int x, int y) {
    if (x + y >= FOO) {
      //do stuff
    }
  }
  void baz(int x) {
    bar(x, FOO);
  }

the compiler can inline the call to bar in baz, and then optimise the condition to (x>=0)… because signed integer overflow is undefined, so can’t happen, so the two conditions are equivalent.

The countless messages about optimisations like that would swamp ones about real dangerous optimisations.