[Bug tree-optimization/110131] [12/13/14 Regression] Missed Dead Code Elimination when using __builtin_unreachable since r12-6924-gc2b610e7c6c

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110131

--- Comment #10 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #8)
> With https://gcc.gnu.org/pipermail/gcc-patches/2023-September/629128.html we
> get:
>   _34 = (int) _13;
>   _30 = (unsigned int) _13;
>   _22 = _30 == 4294967295;
>   _35 = _22 ? _34 : 0;

Maybe:
(simplify
 (cond (eq (convert1?@4 @0) INTEGER_CST@1)
  (convert2? @0) INTEGER_CST@3)
  (if (type is a nop_conversion type from @1)
   (cond! @4 (convert @1) @3)))

This should give:
_30 = (unsigned int) _13;
_22 = _30 == 4294967295;
_35 = _22 ? -1 : 0;
if (_35 != 5)

_35 will -(convert)_22 really.
Anyways VRP will notice that _35 can't be 5 and optimize it out.