[LLVMdev] DIFactory

[Devang Patel]

On Wed, Jul 14, 2010 at 1:04 PM, Renato Golin <rengolin at systemcall.org> wrote:
> On 14 July 2010 18:21, Devang Patel <devang.patel at gmail.com> wrote:
>> Use Create* methods to create basic debug info. There is not any
>> tutorial document explaining how to generated basic debug info.
>
> I got that far... ;)
>
> I could prepare a how-to when I'm finished, if that interests you.

sure


>
>> It is encapsulating how debug info is encoded. Earlier it was using
>> GlobalVariable, now it uses MDNode. The idea is that debug info user
>> will only rely on DIDescriptor class hierarchy to manipulate debug
>> info. The classes in this hierarchy are light weight enough to pass
>> around as objects.
>
> The problem with that is that you can't do:
>
> DIDescriptor file = factory->CreateFile(...);
>
> You have to get the type of file to be DIFile.
>
> When creating a Subprogram, you can't pass a DIFile object, but only a
> DIDescriptor, so you have to:
>
> DIDescriptor* desc = &file;
> factory->CreateSubprogram(*desc, ...);
>
> Also, because they're not pointers, you can't use cast, as you would
> when passing arguments to IRBuilder.
>
> I understand that the objects are lightweight, thus the ability to
> pass them as objects, but some casting could be allowed, especially to
> DIDescriptor (copy ctor? new and assignment operators?).

If it helps then go ahead add them.

>> Debug info is encoded in llvm IR as MDNodes. And all MDNodes from a
>> Module, just like any other llvm values, are automatically emitted
>> when the Module is written to a bitcode file.
>
> Weird, I wasn't getting the metadata before I started forcing
> ModuleDebugInfoPrinterPass via PassManager. Could be other changes I
> did, too, will check.

Make sure at least one regular llvm value is using these MDNodes.
MDNodes are like Constants, if nobody is using them then they
disappear magically.

-
Devang