[llvm] [ctx_prof] Flattened profile lowering pass (PR #107329)

[Mircea Trofin via llvm-commits]

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+; REQUIRES: x86_64-linux
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mtrofin wrote:

Yes (we do have a unittest for flattening, fwiw, but can't hurt)

https://github.com/llvm/llvm-project/pull/107329