[CodeMoverUtils] Improve IsControlFlowEquivalent.
Currently IsControlFlowEquivalent determine if two blocks are control
flow equivalent by checking if A dominates B and B post dominates A.
There exists blocks that are control flow equivalent even if they don't
satisfy the A dominates B and B post dominates A condition.
In the PR, we determine if two blocks are control flow equivalent by
also checking if the two sets of conditions A and B depends on are
Reviewer: jdoerfert, Meinersbur, dmgreen, etiotto, bmahjour, fhahn,
Reviewed By: fhahn
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D71578