[LLVMdev] Running an IR pass after all IR passes

[Rahman Lavaee]

Dear Will,
Thank you,
--plugin-opt does not seem to work on my linux system. I have installed
gold and configured and made LLVM under gold.



On Sun, Mar 30, 2014 at 9:55 PM, Will Dietz <willdtz at gmail.com> wrote:

> FWIW you can pass flags to LTO by escaping it with the following when
> invoking clang:
>
> -Wl,--plugin-opt,-my-pass-option
>
> Or at least you used to be able to.  That said, environment variables
> can be a good fallback
> for stubborn build systems that do things like strip unrecognized linker
> flags.
>
> ~Will
>
> On Sun, Mar 30, 2014 at 12:47 PM, Rahman Lavaee
> <rlavaee at cs.rochester.edu> wrote:
> > 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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> >> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >>
> >>
> >
> >
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>
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