[PATCH] D82305: [Attr] Introduce the `nopoison` attribute

[Luofan Chen via Phabricator via llvm-commits]

bbn created this revision.
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Herald added subscribers: llvm-commits, dexonsmith, steven_wu, hiraditya.
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The `nopoison` IR attribute indicates that the value it associated with cannot be poison, so it will be safe for us to perform more optimizations to it.

For example, consider the following code[1]:

  t = x + 1;
  if (t == y) {
  w = x + 1;
  foo(w);
  }

if we determine that y cannot be poison, then we can apply the GVN optimization to the code above.

[1] 2016 LLVM Developers’ Meeting: N. Lopes “Undefined Behavior: Long Live Poison!"


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D82305

Files:
  llvm/docs/LangRef.rst
  llvm/include/llvm/Bitcode/LLVMBitCodes.h
  llvm/include/llvm/IR/Argument.h
  llvm/include/llvm/IR/Attributes.td
  llvm/lib/AsmParser/LLLexer.cpp
  llvm/lib/AsmParser/LLParser.cpp
  llvm/lib/AsmParser/LLToken.h
  llvm/lib/Bitcode/Reader/BitcodeReader.cpp
  llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
  llvm/lib/IR/Attributes.cpp
  llvm/lib/IR/Function.cpp
  llvm/test/Bitcode/attributes.ll

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