If the layout after the block placement is like this
BB#8: ...... JGE_1 <BB#9>, %EFLAGS<imp-use> Successors according to CFG: BB#9(0x80000000 / 0x80000000 = 100.00%) BB#10: ......
where BB#8 ends with a conditional branch, but the next block is not its successor. The conditional branch should be changed to unconditional branch in MachineBasicBlock::UpdateTerminator(), but this case is missing.
In cases like above example, the results returned by AnalyzeBranch() are: TBB = branch target; FBB = nullptr; Cond = branch condition (not empty)
This corner cases happens if a block (e.g. BB#8) branches and fallthourghs into the same block (e.g. BB#9) before the block placement, and the block placement moves this successor (e.g. BB#9) somewhere else.