[llvm] [CodeGen][CodeLayout] Fix segfault on access to deleted block in MBP. (PR #142357)

[via llvm-commits]

weiguozhi wrote:

> RemovalCallback erroneously won't erase B' from BlockWorkList, because UnscheduledPredecessors value of FunctionChain is not zero (and it is allowed to be non-zero).

>From function markBlockSuccessors, a BB can be added to BlockWorkList only when UnscheduledPredecessors reaches 0. So how was B added to BlockWorkList in the first place?


https://github.com/llvm/llvm-project/pull/142357