llvm dev - Jul 2010 - [LLVMdev] DIFactory

Hi All,

Is there any documentation on how to use DIFactory to generate basic debug info?

It seems similar enough to IRBuilder but working with objects (rather
than pointers) and that's raising some issues.

Also, am I supposed to run the ModuleDebugInfoPrinterPass manually, or
it gets printed automatically when I WriteBitcodeToFile?


-- 
cheers,
--renato

http://systemcall.org/

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On Wed, Jul 14, 2010 at 8:34 AM, Renato Golin <rengolin at systemcall.org>
wrote:
> Hi All,
>
> Is there any documentation on how to use DIFactory to generate basic debug
info?
Use Create* methods to create basic debug info. There is not any
tutorial document explaining how to generated basic debug info.
>
> It seems similar enough to IRBuilder but working with objects (rather
> than pointers) and that's raising some issues.
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.

It is on my wish list to enhance IRBuilder to cover functionality
supported by DIFactory. If you're interested then patches are welcome
in that direction!
> Also, am I supposed to run the ModuleDebugInfoPrinterPass manually, or
> it gets printed automatically when I WriteBitcodeToFile?
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.

-
Devang

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.

> 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?).

> 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.


-- 
cheers,
--renato

http://systemcall.org/

Reclaim your digital rights, eliminate DRM, learn more at
http://www.defectivebydesign.org/what_is_drm