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While the language reference mention a lot about the LLVM Metadata,

and I see some posts on SO - How to add a Metadata String to an LLVM module with the C++ API?

I also see some code in the llvm source- http://llvm.org/doxygen/DIBuilder_8cpp_source.html

However, they dont seem to mention how to create a MDNode containing a ConstantInt of a particular width.

Following is the relevant code (doesn't work ) - 

std::vector<Metadata*> Elts = 
{
      ConstantInt::get(TheContext,APInt(returnType->getIntegerBitWidth(),decimal_val)) 
};



MDNode* Node = MDNode::get(TheContext, Elts);
callInst->setMetadata(LLVMContext::MD_range,Node);

Can anyone explain how this can be done ?

Thanks!

mal
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2 Answers2

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I have written this small post about how to insert metadata in LLVM IR. You can refer that. Basically you need to use ConstantAsMetadata to achieve this.

deLta
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So apparently I checked the llvm class hierarchy and checked the sub-classes under MetaData. I found a few classes and one of them was - ConstantAsMetadata

The change in the above code that works for me is - 

std::vector<Metadata*> Elts = {
    ConstantAsMetadata::get(ConstantInt::get(TheContext,APInt(returnType,0)) ),

ConstantAsMetadata::get(ConstantInt::get(TheContext,APInt(returnType,decimal_val)) )    

  };

Note- You should ( if you want correctness ) specify a pair of numbers for each range that you are trying to create.

If you are using the verifier pass provided by llvm , the above would not work/make sense if you just have a single ConstantInt inside the initializer. This is because of an assert inside the Verifier pass provided by the llvm.

mal
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