[LLVMdev] [cfe-dev][Openmp-dev] Provide LLVM IR and OpenMP LLVM IR as input in a Pass

Simone Atzeni
Tue, 21 Oct 2014 20:52:38 -0000

>> I want to use the pass Polly to find any data dependence in the code.
>> Since it does not work on OpenMP,
>
> Why not? The loops in the outlined OpenMP regions are just regular loops
(with runtime bounds). Can polly not handle them?

I tried it, it does not work and I also talked already with the Polly
developers. They are slightly different, for example when the pragmas are
translated actually the compiler introduces new functions and Polly get
confused.

>
>> I was thinking to apply it on the
>> not-OpenMP IR, then I need the results of Polly to apply other
>> passes to the OpenMP IR.
>
> I don't think this will work for the OpenMP'd loops. The IR will
look completely different, be in different functions, etc.

What I did, and it works, is to build a script that call clang with Polly the
first time and write the results in a file, then call Clang again with OpenMP
and at the point I can apply other passes on the OpenMP IR reading the Polly
results from that file.
But it’s kind of a “dirty" solution, I was wondering if I can, in some way,
introduce my own option "-myoption” that compile the code in both ways and
make it available to the passes I want to call.

Simone