[LLVMdev] New kind of metadata to capture LLVM IR linking structure

David Blaikie dblaikie at gmail.com
Mon Mar 23 09:46:41 PDT 2015

On Mon, Mar 23, 2015 at 8:15 AM, Khilan Gudka <Khilan.Gudka at cl.cam.ac.uk>

> Hi David
> Thanks for your email.
> What's the benefit/purpose of the MDLLVMModule over just having the
>> MDCompileUnits themselves? I would imagine the user cares about which
>> source file the problem was in (obtained from the MDCompileUnit), not the
>> sequence of BC modules that may've been built into?
> We envisage it to be useful when an analysis tool built using LLVM needs
> to know which MDCompileUnits were part of a particular library that has
> been linked in. For instance, we're currently analysing the sandboxing
> behaviour within the Chromium web browser, which comprises hundreds of
> internal libraries and many external ones. To be able to perform this
> analysis  we have to link them all together into a single .bc/.ll file.
> Having the module structure allows us to model interactions between
> different modules (without manually (and sometimes unreliably) having to
> work out which source file corresponds to which library (e.g. libssl,
> libpci, libpolicy, librenderer, etc)). It also allows an analysis tool to
> support turning on/off output warnings for particular libraries (as they
> can lead to a lot of analysis output).

Fair enough - I've no idea/opinion on whether that's the right abstraction
(other people with more domain knowledge of analysis infrastructure might
chime in with some thoughts).

Practically speaking: would directory paths be sufficient? The
MDCompileUnits already have information about where the source file was.

- David

>>> I would be very grateful if someone could review this.
>>> Thanks
>>> --
>>> Khilan Gudka
>>> Research Associate
>>> Security Group
>>> Computer Laboratory
>>> University of Cambridge
>>> http://www.cl.cam.ac.uk/~kg365/
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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