[LLVMdev] Running an IR pass after all IR passes

[Rahman Lavaee]

Thank you very much John.
With an environment variable I need to take some special care, but it looks
like the only way to go.


On Sun, Mar 30, 2014 at 11:07 AM, John Criswell <criswell at illinois.edu>wrote:

>  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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>
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