[llvm] [TailDuplicator] Add a limit on the number of indirect branch successors (PR #78582)

[Quentin Dian via llvm-commits]

DianQK wrote:

@efriedma-quic I've put most of the analysis into [this comment](https://github.com/llvm/llvm-project/issues/78578#issuecomment-1962363580).

In a nutshell, I speculate that duplicating critical BBs makes CFG exceptionally complex, especially within loops, which may be the primary reason for increased time consumption by other passes. A critical BB refers to one with multiple predecessors and multiple successors.

https://github.com/llvm/llvm-project/pull/78582