[LLVMdev] Performing my own pass with a single command line?

[John Criswell]

Zheng Wang wrote:
> Hi John,
>
> Are there any documents about how to add a pass into LTO?
>   

No, but I believe you may want to look at  
LTOCodeGenerator::generateAssemblyCode in LTOCodeGenerator.cpp.  That is 
where I added the SAFECode passes in libLTO from LLVM 2.6.

I should warn you that using libLTO for running additional passes is 
rather new.  I've only used it once or twice myself.  That said, it 
looks to be a very promising approach; I've got a graduate student here 
who is trying the approach out for his own project.

-- John T.
> Cheers,
> Zheng
>
> On 19 April 2010 15:11, John Criswell <criswell at uiuc.edu> wrote:
>   
>> Dear Zheng Wang,
>>
>> You have a few options:
>>
>> 1) You can add your pass to the set of passes that llvm-gcc runs when it
>> optimizes code.  This requires re-compiling llvm-gcc; it also means that
>> your pass must be able to run on incomplete programs and be run multiple
>> times over the same code (i.e., it cannot do whole-program analysis).
>>
>> 2) You can change the build system of the program you're working with to
>> generate an LLVM bitcode file.  It's the same as what you're doing now,
>> except that the program's Makefiles automate the task for you.
>>
>> 3) You can add your passes to libLTO (http://llvm.org/docs/GoldPlugin.html
>> and http://llvm.org/docs/LinkTimeOptimization.html).  This will allow your
>> passes to be run at link-time by the linker.  This method takes some time to
>> set up, but it should work beautfully once set up.  Furthermore, it can do
>> whole-program analysis and optimization (the linker knows when it is
>> creating a final executable vs. an object file and can defer whole program
>> analysis and transformation until the final link stage).
>>
>> -- John T.
>>
>>
>> Zheng Wang wrote:
>>     
>>> Hello,
>>>
>>>
>>> As far as I know, the LLVM pass manager only perform at the llvm
>>> bytecode level.
>>>
>>> This means for each program, I have to convert it to a LLVM bytecode by:
>>>
>>> llvm-gcc -c -emit-llvm test.c
>>>
>>> then, I can issue the llvm pass manager to invoke my own pass and
>>> produce an output as LLVM bytecode, such as:
>>>
>>> opt -my-pass < test.o > test.new.o
>>>
>>> After this point, I need to convert it to assembly code using llc,
>>> then to use 'as' to compile the assembly code to an object file, and
>>> finally I can
>>> use gcc to generate an executable program.
>>>
>>> *****My question is*****, is there any way to automatically evoke the
>>> pass manager, such as:
>>>
>>> llvm-gcc -c test.c
>>>
>>> and in such a way my own pass will be evoked?
>>>
>>> Cheers,
>>> Zheng
>>> _______________________________________________
>>> 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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