[llvm] [VPlan] Model branch cond to enter scalar epilogue in VPlan. (PR #92651)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Still many comments to address, but I'd like to note https://github.com/llvm/llvm-project/pull/95816 which uses VPIRBasicBlock to wrap middle.block (and replaces the custom branch back-patching logic for the middle block from VPBasicBlock::execute with the generic updating in VPIRBasicBlock, to be reused here)

https://github.com/llvm/llvm-project/pull/92651