[llvm] [JumpThreading] Materialize PHIs in duplicateCondBranchOnPHIIntoPred (PR #204859)

[Hongyu Chen via llvm-commits]

https://github.com/XChy approved this pull request.

Generally looks good to me. And I wonder if there is a parallel replacement method without creating new blocks.

https://github.com/llvm/llvm-project/pull/204859