CODEWITHSUNDEEP
metadatallvm
henry
henry

Reputation: 185

llvm Invalid operand for global metadata

I want to assign unique IDs for basic blocks in a module using global metadata. But I got an error: "Invalid operand for global metadata!". Any problems in the follow code snippet?

Here is part of the code I add operand of a named metadata node:

bool runOnModule(Module &M) {
    ...
    NamedMDNode *NMD = M.getOrInsertNamedMetadata(mdKindName);
    for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
        for (Function::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ++BI) {
            errs() << "Basic Block number: " << counter << "\n";
            NMD->addOperand(assignID(BI, ++counter));
            errs() << "Basic Block name: " << BI->getName() << "\n";
        }
    }
    ...
}

// Assign unique IDs to Basic Blocks as Metadata Nodes
MDNode* assignID (BasicBlock* BB, unsigned id) {
    // Fetch the context in which the enclosing module was defined
    LLVMContext &Context = BB->getParent()->getParent()->getContext();

    // Create a metadata node that contains ID as a constant:
    Value* ID[2];
    ID[0] = BB;
    ID[1] = ConstantInt::get(Type::getInt32Ty(Context), id);
    return MDNode::getWhenValsUnresolved(Context, ArrayRef<Value*>(ID, 2), false);
}

The version of llvm is 3.6.0. I am using visual studio 2013 for my project.

Thanks, henry

Solution: ID[0] should store MDString::get(Context, BB->getName())

Upvotes: 2

Views: 350

Answers (1)

Oak
Oak

Reputation: 26878

By passing false as the last argument for getWhenValsUnresolved, you have created a global metadata node. Global metadata may only contain:

  1. Constants, including addresses of global values.
  2. MDNodes.
  3. MDStrings.

If you want to use something which is function-local - such as instruction, argument or (in your case) a basic-block, you need to use local metadata. Create one by using true as the last argument there.

Upvotes: 2

Related Questions