[PATCH] D142801: [Local][InstCombine] Handle !noundef metadata in combineMetadata

[luxufan via Phabricator via llvm-commits]

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Handle !noundef metadata in comhineMetadata. The behavior of violating
!noundef metadata is undefined behavior. So if K dominates J, we can
preserve it uncontionally, otherwise, we preserve it if both K and J
have !noundef metadata been set.

This patch also makes !noundef metadata added in KnownIDs when doing
instruction combine for phi node.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D142801

Files:
  llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
  llvm/lib/Transforms/Utils/Local.cpp
  llvm/test/Transforms/InstCombine/phi-load-metadata-4.ll

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