That's very funny to me.

A) x is always removed.

B) no, it's never removed if volatile.

But neither person can prove what a compiler will actually do, despite claiming they'll always act a certain way given 5 lines of code.

Also, at behavioural edges what you'll see on Godbolt is compiler bugs. So you learn nothing about what should happen.

All popular modern C++ compilers have known bugs and while I'm sure there are C compilers with no known bugs that will be because nobody tested very hard.

I made the weaker claim that x can be removed. This is something I could prove with compiler output but I would have to find a compiler willing to make this optimization which is not something I can guarantee.