[LLVMdev] Running an IR pass after all IR passes

[John Criswell]

Dear Rahman,

I think your best option is to modify the code in libLTO so that it runs 
your pass when you want it to run.  I believe the file you want to 
modify is LTOCodeGenerator.cpp.

This does mean that passing options to your pass will be difficult or 
impossible.  However, you can either hard-code the options you need or 
read them from an environment variable if there is no easy way to pass 
options to the libLTO.

If you want to go the llc route, then you'll need to modify the llc code 
so that it runs your pass instead of opt; sadly, I don't know off-hand 
where the code is that you would need to modify (it is either in llc or 
in some LLVM library somewhere).  The only reason I discourage the llc 
route is because it is difficult to get whole-program bitcode files for 
large programs (e.g., Apache).

Regards,

John Criswell

On 3/29/14, 12:47 AM, Rahman Lavaee wrote:
> Hi,
> I am finding it difficult to see how I can run an IR instrumentation 
> pass after "all" IR passes.
> I previously used opt to run my pass after linking all the llvm 
> bitcode files and then ran llc.
> I found out that llc runs some other Function passes which depend on 
> the target.
> For example, tail calls are only supported in x86 under some 
> circumstances.
>
> Then I tried lto and link time optimization. But I found it difficult 
> to specify a flag option for my instrumentation pass.
>
> Is there any way in llvm to run an IR pass after all IR passes?
>
>
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