[llvm] [AggressiveInstCombine] Bail out on graph nodes in unreachable blocks (PR #226383)

[Ömer Sinan Ağacan via llvm-commits]

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osa1 wrote:

Thanks. I'd find it helpful if the comment above (the one with "ordered around") said that unreachable predecessors don't happen in a full opt pipeline and therefore they're not worth reducing.

https://github.com/llvm/llvm-project/pull/226383