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

[Khilan Gudka]

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).


>
>
>>
>> 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/
>>
>>
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>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>>
>>
>
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