[PATCH] D104602: [InstCombine] Use poison constant to represent the result of unreachable instrs

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune created this revision.
aqjune added reviewers: nikic, lebedev.ri, spatel, efriedma.
Herald added subscribers: jfb, hiraditya.
aqjune requested review of this revision.
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This patch updates InstCombine to use poison constant to represent the resulting value of (either semantically or syntactically) unreachable instrs.

This allows more aggressive folding of unused results, as shown in llvm/test/Transforms/InstCombine/getelementptr.ll .


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D104602

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
  llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
  llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
  llvm/test/Transforms/GVN/PRE/2017-06-28-pre-load-dbgloc.ll
  llvm/test/Transforms/InstCombine/atomic.ll
  llvm/test/Transforms/InstCombine/builtin-object-size-ptr.ll
  llvm/test/Transforms/InstCombine/getelementptr.ll
  llvm/test/Transforms/InstCombine/load.ll
  llvm/test/Transforms/InstCombine/pr44245.ll
  llvm/test/Transforms/InstCombine/sadd-with-overflow.ll
  llvm/test/Transforms/InstCombine/ssub-with-overflow.ll
  llvm/test/Transforms/InstCombine/store.ll
  llvm/test/Transforms/InstCombine/uadd-with-overflow.ll
  llvm/test/Transforms/InstCombine/with_overflow.ll

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