compiler/c2/irTests/TestDuplicateBackedge.java fails after JDK-8314307 (was problemlisted). The problem is the following:

PhaseIdealLoop::duplicate_loop_backedge() splits a loop that cannot be transformed to a counted loop into an inner and outer loop. The idea is that the inner loop can then be converted into a counted loop afterward.

However, this is no longer possible after JDK-8314307 due to requiring a Loop Limit Check Predicate (with a Loop Limit Check Parse Predicate) for the inner loop because we cannot statically prove that there is no overflow. We can only transform the loop to a counted loop if we have a guarantee that there is no overflow.

After duplicate_loop_backedge(), we have Loop -> Loop without any Parse Predicate in between. We fail to transform the inner loop to a counted loop and the IR matching done in TestDuplicateBackedge fails. We should try to fix this.