llvm dev - Mar 2011 - [LLVMdev] Accessing metadata & creating DIVariable

>>> I am  adding local var to existing IR with debug info. I am not
using
>>> the Pass infrastructure.
>>>
>>> void InsertDbg(AllocaInst *i, StringRef varname, Instruction,
inserbefore)
>>> {
>>>
>>> DIBuilder di(*module);
>>> cu = di.createCU        / * How do I get the MDNode of  already in
the
>>> IR . Instead of recreating it, using filename and directory I knew
out
>>> of band */
>>
>> DIBuilder.createCompileUnit() does not return anything.
>>
>>> file= di.createFile
>>
>> You don't need CU here.
>>
>>>
>>> type= di.createBasicType   //long
>>
>> same, you don't need CU here.
>
> If I don't have a di.createCompileUnit.  di.createFile fails with this
message.
>
> DIBuilder.cpp:59: llvm::DIFile
> llvm::DIBuilder::createFile(llvm::StringRef, llvm::StringRef):
> Assertion `TheCU && "Unable to create DW_TAG_file_type without
> CompileUnit"' failed.
>
> Which had me scratching my head, If DIFile needs a CU it  would be an
> argument to DIBuilder::.createFile
> Also type.Verify() thought createBasicType succeeds.
I meant type.Verify() fails, though the call creatBasicType succeeds.

Hi,
> You need to call di.createCompileUnit() once for your translation unit in
the beginning. You don't need to keep track of CU yourself. DIBuilder will
take care of it. After words, you can call di.createBasicType(..) and it will
work.
Actually it doesn't. But if I call di.createCompileUnit(file, dir,
producer, ...) with file or dir different from that of  CU already in
the file, then it works. It isn't sufficient if the producer is
different. That fixes my problem, so many thanks.

If  DIBuiler constructor would  pick existing CU from the Module,  we
can retain original CU entry.  But, I do no have enough knowledge of
DWARF or LLVM, to know if it is valid/reasonable thing to do.

thanks,
Vyas