These branch types behave identically, except in the determination of whether to branch or not. For br.ctop, the branch is taken if either LC is non-zero or EC is greater than one. For br.cexit, the opposite is true. It is not taken if either LC is non-zero or EC is greater than one and is taken otherwise.
These branch types also use LC and EC to control register rotation and predicate initialization. During the prolog and kernel phase, when LC is non-zero, LC counts down. When br.ctop or br.cexit is executed with LC equal to zero, the epilog phase is entered, and EC counts down. When br.ctop or br.cexit is executed with LC equal to zero and EC equal to one, a final decrement of EC and a final register rotation are done. If LC and EC are equal to zero, register rotation stops. These other effects are the same for the two branch types.