llvm dev - Jan 2016 - Whole program LLVM bitcode files

Hi all,

I'm trying to generate whole program bitcode files for linux kernel
and do interprocedural
analysis on kernel.

I use llvmlinux to compile kernel with clang and  generate a bunch of
bitcode files successfully.
I need to link all these bitcode files together into a single bitcode file,
so that I can run whole program analysis.

Can I use llvm-link to achieve this?
Or should I use libLTO to link all these bitcode files together? I guess I
have to modify the linux kernel's build scripts and Makefiles?
I'm kind of confused. Any suggestions?

Thank you

Regards,
Kai
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Hi,
> On Jan 5, 2016, at 3:22 PM, Kai Wang via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> 
> Hi all,
> 
> I'm trying to generate whole program bitcode files for linux kernel and
do interprocedural analysis on kernel.
> 
> I use llvmlinux to compile kernel with clang and  generate a bunch of
bitcode files successfully.
> I need to link all these bitcode files together into a single bitcode file,
so that I can run whole program analysis.
> 
> Can I use llvm-link to achieve this?
Yes.
> Or should I use libLTO to link all these bitcode files together? I guess I
have to modify the linux kernel's build scripts and Makefiles?
libLTO is used directly by *some* linkers to perform both linking the modules
and optimizing the result. Depending on what you’re trying to achieve, it can be
interesting for you.
In any case you can start with llvm-link to get your analysis working with opt,
and it won’t be hard to integrate it in LTO later if needed.

— 
Mehdi

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> On 2016-Jan-06, at 08:53, Mehdi Amini via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi,
> 
>> On Jan 5, 2016, at 3:22 PM, Kai Wang via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>> 
>> 
>> Hi all,
>> 
>> I'm trying to generate whole program bitcode files for linux kernel
and do interprocedural analysis on kernel.
>> 
>> I use llvmlinux to compile kernel with clang and  generate a bunch of
bitcode files successfully.
>> I need to link all these bitcode files together into a single bitcode
file, so that I can run whole program analysis.
>> 
>> Can I use llvm-link to achieve this?
> 
> Yes.
Just a note: llvm-link is a tool for LLVM developers (i.e., compiler
hackers), mainly for use in regression tests.  I don't recommend using
it in a production workflow.  It will certainly work for hacking
around though!