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

[Afanasyev Ivan via llvm-commits]

ivafanas wrote:

We have caught the bug on the custom out-of-tree backend in a ~200Kb function of ~60 basic blocks. Any attempt to reduce the test case results in bug disappearing.

I'm afraid, I'm not able to provide the reproducer / regression test for any in-tree backend in a reasonable time.

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