[Bug tree-optimization/95001] std::terminate() and abort() do not have __builtin_unreachable() semantics

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95001

--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> ---
Simpler example:

[[noreturn]] void theend();

int f(int x){
  if(x&7)theend();
  return x&3;
}

(or replace "theend()" with "throw 42")

We shouldn't compute x&3, it is always 0 in the branch where it is computed.

But this simple example would probably be doable similarly to VRP, while the
original example requires that the information be available during another pass
(on-demand non-zero bits, like there is work on on-demand ranges?).