[LLVMdev] DIBuilder - what's with the null compile units?

[James Molloy]

Hi Talin,

Followup as promised: in our case we weren't calling finalize(). As this manifests itself as exactly the same assertion failure as yours I suggest you double-check you are actually calling it before any passes run on the Module.

Functionally, instead of maintaining a pointer to the CU in all Debug nodes, the main CompilationUnit node has a list of subprogram nodes. It is from this that a map gets generated of Subprogram -> CU. If such a mapping doesn't exist, the assertion you see (assuming it is the same as ours) fires.

First thing I'd do is check the generated metadata. Is second-to-last parameter of the DW_TAG_subprogram metadata pointing at a pointer to NULL, or is it pointing at a pointer to DW_TAG_subprogram?

If the former, finalize() is not being run (or something is failing at that point). If the latter, your problem is different to ours.

Hope this helps,

James

-----Original Message-----
From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of James Molloy
Sent: 24 September 2011 09:38
To: Devang Patel; Talin
Cc: LLVM Developers Mailing List
Subject: Re: [LLVMdev] DIBuilder - what's with the null compile units?

Hi,

Thanks for bringing this up, I'm just about to investigate an identical case which has broken our front-end. Both ours and clang generate subroutineinfo with null compilationunits, but ours asserts and clang's doesn't.

I'll take a look at this on Monday, if it is a bug in LLVM.

Cheers,

James

-----Original Message-----
From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Devang Patel
Sent: 23 September 2011 21:06
To: Talin
Cc: LLVM Developers Mailing List
Subject: Re: [LLVMdev] DIBuilder - what's with the null compile units?


On Sep 23, 2011, at 12:39 PM, Talin wrote:

> Sometime about two months ago, something changed in LLVM that broke my frontend's ability to generate debug info. This was around the time that the requirement to call DIBuilder::finalize() was added (and yes, I am calling it.) Specifically, what I am seeing is an assertion failure in llc because it can't find the compile unit for a subroutine.

I forgot to say earlier, that's a bug. Please file a PR with a test case.
-
Devang

>
> I took a look at the code in DIBuilder.cpp, and I see that indeed it is setting the compile unit to null for all of the various descriptors being created. I assume that the intent is that these references would be filled in later - but apparently this is not happening in my case. Any idea what could be wrong?
>
> --
> -- Talin
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