[LLVMdev] creating new Metadata

[John Criswell]

On 12/20/11 9:25 PM, 陳韋任 wrote:
>> 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.

There's example code in SAFECode for LLVM 2.7 for attaching metadata:

http://llvm.org/viewvc/llvm-project/safecode/branches/release_27/lib/Utility/PoolHandles.cpp?revision=135925&view=markup

Look at PoolMDPass::createPoolMetaData().

-- John T.

>
> ---
>    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;
>    V.push_back(s1);
>    V.push_back(CI);
>    V.push_back(s2);
>
>    MDNode *n1 = MDNode::get(Context,&V[0], 3);
> ---
>
> HTH,
> chenwj
>