Trap values are similar to undef values, however +
Trap values are similar to undef values, however instead of representing an unspecified bit pattern, they represent the fact that an instruction or constant expression which cannot evoke side effects has nevertheless detected a condition which results in undefined - behavior.
+ behavior.
Any non-void instruction or constant expression other than a non-intrinsic call, invoke, or phi with a trap operand has trap as its result value.