llvm dev - Aug 2012 - [LLVMdev] How to insert metadata in llvm IR?

As title.
I try to write a pass to covert the bitcode with no debug info to the bitcode 
with 
debug info. I use DIBuilder as a LLVM API so that I can generate DI(Debug info).
Now I have some DIDescriptor , e.g. DIVariable ,DICompileUnit, DISubprogram , I 
can use some function to insert metadata.

1. LLVM::Instruction::SetDebugLoc(...) => insert the debug info location like
DILexicalBlock ,and insert !dbg appending an instruction.
2. LLVM::Instruction::setMetadata(...) => insert the metadta and !dbg
appending
an 
instruction.
3. DIBuilder::insertDeclare(...) =>  insert variable declare (like 
@llvm.dbg.declare) and metadata.
4. llvm::NamedMDNode::addOperand(...) => insert and Named Metadata. Like 

I can use above four function to insert metadata into bitcode. But I can't
just
insert a metadata. 
This problem is occur when I want to create an DISubprogram 
metadata into bc. 
I can't use above four function because this descriptor not 
append any instruction and I can't use declare to generate it. 
This descriptor is 
not a NamedMDNode too. I have try many way to insert it, but I failed...

Can you tell me a right way to insert this MD? 
thanks

--
Kevin FangA

On Aug 1, 2012, at 4:49 AM, Kevin Fang <keigi1203 at gmail.com> wrote:
> Can you tell me a right way to insert this MD? 
Why would you do this in this way? Why not just do it at the time you create the
module in the first place? Your summation of how the debug information is
supposed to be added via the classes also isn't quite correct. I'd look
into how clang emits debug information as a guideline.

-eric