Function computePointerICmp

A significant optimization not implemented here is assuming that alloca addresses are not equal to incoming argument values. They don't *alias*, as we say, but that doesn't mean they aren't equal, so we take a conservative approach. This is inspired in part by C++11 5.10p1: "Two pointers of the same type compare equal if and only if they are both null, both point to the same function, or both rep