[arihant]

I am almost certain the pointer aliasing thing could be fixed by providing the proper optimization tag at compile time. I remember back in introductory systems classes, we saw mind boggling optimizations from GCC at O3 - the pointer example is so trivial it must be optimized by the compiler!

[brigade]

It isn't; there are very few flags that allow the compiler to perform optimizations not allowed by the language standard. Aliasing is not one of them for any compiler I know of. In fact, there are usually flags to go the opposite direction and assume all pointers alias because so many people write code that violates the standard (and results in GCC optimizing the code to behave differently than the author intended.)

[richardwhiuk]

You can only optimise if you know that it globally isn't ever passed the same, which won't be the case at compile time, as a separate object may be linked which does provide x==z.