[UnJ] Common some code. NFC
[UnJ] Common some code. NFC

Create a processHeaderPhiOperands for analysing the instructions
in the aft blocks that must be moved before the loop.

Differential Revision: https://reviews.llvm.org/D49061



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@338033 91177308-0d34-0410-b5e6-96231b3b80d8

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