[cfe-dev] [llvm-dev] LLVM/CUDA generate LLVM IR

[Gurunath Kadam via cfe-dev]

Hi,

Thank you Justin for your prompt reply. I was able to generate an LLVM IR.

For the error reproduction purposes, I have listed below all the commands
which worked and which did not work.

Works (I have not yet checked if files generated by all of them are same or
not):

    * clang++ -O3 -emit-llvm -c axpy.cu <http://axpy.cu> -o axpy.bc
--cuda-gpu-arch=sm_35 --cuda-path=/usr/local/cuda/ --cuda-device-only*

     *clang++ -O3 -emit-llvm -c axpy.cu <http://axpy.cu> -o axpy.bc
--cuda-device-only*

Does not work:

      *clang++ -O3 -emit-llvm -c axpy.cu <http://axpy.cu>
--cuda-gpu-arch=sm_35 -o axpy.bc*

I think *--cuda-gpu-arch=sm_35* and *--cuda-path=/usr/local/cuda/* should
be included, as the resulting code might be optimized for that
architecture. I might be wrong though.

Thank you again.

-Guru

On Thu, Oct 13, 2016 at 4:38 PM, Justin Lebar <jlebar at google.com> wrote:

> If you add -### to your original command, you'll see that for CUDA
> compilations, we invoke clang -cc1 twice: Once for the host, and once
> for the device.  We can't emit llvm or asm for both host and device at
> once, so you need to tell clang which one you want.
>
> The flag to do this is --cuda-device-only (or --cuda-host-only).
>
> Alternatively, you could compile with -save-temps to get everything.
>
> Feel free to send me a patch adding this information to
> http://llvm.org/docs/CompileCudaWithLLVM.html so that we can help
> others avoid this hiccup.  The document lives in
> llvm/docs/CompileCudaWithLLVM.rst.
>
> > I tried adding -S -emit-llvm and changed the output file name, but I
> keep getting following error:
>
> That is a bug -- we should give you a meaningful error.  It looks like
> this bug was probably introduced by the generic offloading driver
> changes.
>
> I am having difficulty reproducing the assertion failure, however.
> Can you please provide a concrete steps to reproduce?
>
> Regards,
> -Justin
>
> On Thu, Oct 13, 2016 at 1:28 PM, Reid Kleckner <rnk at google.com> wrote:
> > Moving to cfe-dev
> >
> > +Art and Justin
> >
> > On Thu, Oct 13, 2016 at 1:13 PM, Gurunath Kadam via llvm-dev
> > <llvm-dev at lists.llvm.org> wrote:
> >>
> >> So for a c program we do:
> >>
> >>         clang -O3 -emit-llvm hello.c -c -o hello.bc
> >>
> >> But how to generate an LLVM IR when working with CUDA.
> >>
> >> for normal compilation:
> >>          clang++ axpy.cu -o axpy --cuda-gpu-arch=<GPU arch> -L<CUDA
> >> install path>/<lib64 or lib> -lcudart_static -ldl -lrt -pthread
> >>
> >> I tried adding -S -emit-llvm and changed the output file name, but I
> keep
> >> getting following error:
> >>
> >> clang++:
> >> /stor/gakadam/llvm_projects/llvm/tools/clang/lib/Driver/
> Driver.cpp:1618:
> >> virtual
> >> {anonymous}::OffloadingActionBuilder::DeviceActionBuilder::
> ActionBuilderReturnCode
> >> {anonymous}::OffloadingActionBuilder::CudaActionBuilder::
> getDeviceDepences(clang::driver::OffloadAction::DeviceDependences&,
> >> clang::driver::phases::ID, clang::driver::phases::ID,
> >> {anonymous}::OffloadingActionBuilder::DeviceActionBuilder::PhasesTy&):
> >> Assertion `CurPhase < phases::Backend && "Generating single CUDA "
> >> "instructions should only occur " "before the backend phase!"' failed.
> >>
> >> I tried several combinations but no avail!
> >>
> >> Any suggestions?
> >>
> >> Thank you.
> >>
> >> Sincerely,
> >> Guru
> >>
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> llvm-dev at lists.llvm.org
> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >>
> >
>
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