[llvm-branch-commits] [ADCE][NFC] Use block numbers instead of DenseMap (PR #189406)

[Alexis Engelke via llvm-branch-commits]

https://github.com/aengelke created https://github.com/llvm/llvm-project/pull/189406

Straight-forward replacement of the DenseMap with a vector. Data
structure cleanup will follow as separate patch.