[LLVMdev] creating new Metadata

陳韋任 chenwj at iis.sinica.edu.tw
Tue Dec 20 19:25:59 PST 2011

> Dear llvm-ers,
> I am trying to attach a customized metadata to llvm instructions.
> Let's say, I want to attach some number to each instruction.
> I am trying to use
> void Instruction::setMetadata(unsigned KindID, MDNode* Node)
> but I am not sure how to create a brand new instance of an MDNode.
> Do you have any code samples demonstrating how to do that?
> Due to some tool dependencies, I am using LLVM 2.7

  `grep -r MDNode` in $LLVM_SOURCE may give you some examples.  I don't know if
there is a doxygen for LLVM 2.7, but you can see include/llvm/Metadata.h and 
unittests/VMCore/MetadataTest.cpp to know how to create a MDNode. Below is code
snipt taken form MetadataTest.cpp.

  MDString *s1 = MDString::get(Context, StringRef(&x[0], 3));
  MDString *s2 = MDString::get(Context, StringRef(&y[0], 3));
  ConstantInt *CI = ConstantInt::get(getGlobalContext(), APInt(8, 0));

  std::vector<Value *> V;

  MDNode *n1 = MDNode::get(Context, &V[0], 3);


Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj

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