[clang] [llvm] [AMDGPU] Change CF intrinsics lowering to reconverge on predecessors. (PR #92809)

[Matt Arsenault via cfe-commits]

https://github.com/arsenm requested changes to this pull request.

There are quite a few code quality regressions, and XFAILed tests. The description needs more elaboration on what the strategy is here 

https://github.com/llvm/llvm-project/pull/92809