[clang] [llvm] [mlir] [polly] [IRBuilder] Use SetInsertPoint without redundant BasicBlock argument (PR #228476)

[Nikita Popov via cfe-commits]

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nikic wrote:

They can in fact go out of sync, which I learned the hard way in https://github.com/llvm/llvm-project/pull/228117. I expect that dropping the separate BB member is going to run into similar complications as that PR.

I've left a TODO for dropping the member.

https://github.com/llvm/llvm-project/pull/228476