llvm dev - May 2015 - [LLVMdev] How to write a custom LTO pass?

I'd like to write an inter-modular analysis pass. My understanding is that
this should take the form of an LTO pass. However, I have been unable to
find any resources on the mechanics of writing and running a custom LTO
pass. Does anyone have any pointers?

Thanks,
Steve
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On 5/18/15 2:16 PM, Stephen Thomas wrote:
> I'd like to write an inter-modular analysis pass. My understanding is 
> that this should take the form of an LTO pass. However, I have been 
> unable to find any resources on the mechanics of writing and running a 
> custom LTO pass. Does anyone have any pointers?
All you need to do is to write a ModulePass and modify the libLTO plugin 
to run it.  Writing a ModulePass is described in the "How to Write an 
LLVM Pass" document in the LLVM documentation.  To modify libLTO,
you'll
need to read the documents on how to install it, and you'll need to 
modify the plugin (in llvm/tools/LTO, I think). Alternatively, you can 
modify the LLVM library that defines which passes get run when you use 
-O2 and -flto optimization, but the result is the same: you'll need to 
install a new libLTO plugin.

Regards,

John Criswell
>
> Thanks,
> Steve
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

-- 
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
http://www.cs.rochester.edu/u/criswell

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It works in debug mode.  I left the std::cout statements in and compiled in 
sim mode.  ir2v aborted.  

A similar abort happened with more than 8 memcpy's to cpu_ptrs.  I don't
know if
there are other limits we should be diagnosing or documenting.  

-jon

On May 18, 2015, at 2:34 PM, John Criswell wrote:
> On 5/18/15 2:16 PM, Stephen Thomas wrote:
>> I'd like to write an inter-modular analysis pass. My understanding
is that this should take the form of an LTO pass. However, I have been unable to
find any resources on the mechanics of writing and running a custom LTO pass.
Does anyone have any pointers?
> 
> All you need to do is to write a ModulePass and modify the libLTO plugin to
run it.  Writing a ModulePass is described in the "How to Write an LLVM
Pass" document in the LLVM documentation.  To modify libLTO, you'll
need to read the documents on how to install it, and you'll need to modify
the plugin (in llvm/tools/LTO, I think).  Alternatively, you can modify the LLVM
library that defines which passes get run when you use -O2 and -flto
optimization, but the result is the same: you'll need to install a new
libLTO plugin.
> 
> Regards,
> 
> John Criswell
> 
>> 
>> Thanks,
>> Steve
>> 
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
> 
> -- 
> John Criswell
> Assistant Professor
> Department of Computer Science, University of Rochester
> http://www.cs.rochester.edu/u/criswell
> _______________________________________________
> 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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On Mon, May 18, 2015 at 3:34 PM, John Criswell <jtcriswel at gmail.com>
wrote:
>  On 5/18/15 2:16 PM, Stephen Thomas wrote:
>
> I'd like to write an inter-modular analysis pass. My understanding is
that
> this should take the form of an LTO pass. However, I have been unable to
> find any resources on the mechanics of writing and running a custom LTO
> pass. Does anyone have any pointers?
>
>
> All you need to do is to write a ModulePass and modify the libLTO plugin
> to run it.  Writing a ModulePass is described in the "How to Write an
LLVM
> Pass" document in the LLVM documentation.
>
Great, that makes sense.

> To modify libLTO, you'll need to read the documents on how to install
it,
> and you'll need to modify the plugin (in llvm/tools/LTO, I think).
>
Alternatively, you can modify the LLVM library that defines which
passes
> get run when you use -O2 and -flto optimization, but the result is the
> same: you'll need to install a new libLTO plugin.
>
Just to check my understanding: I will have to change LLVM source code
(probably to some .cpp file in llvm/tools/LTO or in llvm/lib/LTO) and
recompile in order to run my custom LTO pass? I'm double checking because
for custom intra-modular analysis passes, it is not a requirement to change
LLVM source code. Instead, one just adds the name of the .so to the opt
invocation. (
http://llvm.org/docs/WritingAnLLVMPass.html#running-a-pass-with-opt).

Thanks,
Steve

>
> Regards,
>
> John Criswell
>
>
>  Thanks,
> Steve
>
>
> _______________________________________________
> LLVM Developers mailing listLLVMdev at cs.uiuc.edu        
http://llvm.cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
>
> --
> John Criswell
> Assistant Professor
> Department of Computer Science, University of
Rochesterhttp://www.cs.rochester.edu/u/criswell
>
>
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