llvm dev - Oct 2013 - [LLVMdev] Implementing the ARM NEON Intrinsics for PowerPC

Hello LLVM Devs,

Thanks for helping me previously to cross-compile for ARM, I managed to get
a working toolchain and am currently having fun compiling different toy
problems and running them on a pandaboard.

As part of my research I am trying to implement the ARM NEON Intrinsics in
the PowerPC LLVM backend. I am still at the beginning of my efforts and am
not yet familiar with either the ARM or the PowerPC backends. After I
started investigating the code and found out that in total it is more than
100 kloc for the two backends I thought it is a good idea to ask you for
some hints of where I should start from.

I have written a small unrelated experimental backend for LLVM before, so I
have some experience with the topic.

Thanks,
 - Stan
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Stan,

Do you mean that you want to emulate the ARM NEON intrinsics on PowerPC?

 -Hal

----- Original Message -----
> 
> 
> Hello LLVM Devs,
> 
> 
> Thanks for helping me previously to cross-compile for ARM, I managed
> to get a working toolchain and am currently having fun compiling
> different toy problems and running them on a pandaboard.
> 
> As part of my research I am trying to implement the ARM NEON
> Intrinsics in the PowerPC LLVM backend. I am still at the beginning
> of my efforts and am not yet familiar with either the ARM or the
> PowerPC backends. After I started investigating the code and found
> out that in total it is more than 100 kloc for the two backends I
> thought it is a good idea to ask you for some hints of where I
> should start from.
> 
> I have written a small unrelated experimental backend for LLVM
> before, so I have some experience with the topic.
> 
> 
> Thanks,
> - Stan
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory

Hello Hal,

I am not very familiar with the DSP capabilities of PowerPC, but I imagine
there will be instructions for simple vector operations like vector
addition, multiplication, etc. so for these I imagine the implementation
would consist of just outputting the correct instruction. However, for NEON
instructions like the reciprocal step (see
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0489c/CIHDIACI.html)
it
is unlikely that there is a corresponding PowerPC vector instruction, so
these will need to be emulated, yes.

 - Stan


On 2 October 2013 04:14, Hal Finkel <hfinkel at anl.gov> wrote:
> Stan,
>
> Do you mean that you want to emulate the ARM NEON intrinsics on PowerPC?
>
>  -Hal
>
> ----- Original Message -----
> >
> >
> > Hello LLVM Devs,
> >
> >
> > Thanks for helping me previously to cross-compile for ARM, I managed
> > to get a working toolchain and am currently having fun compiling
> > different toy problems and running them on a pandaboard.
> >
> > As part of my research I am trying to implement the ARM NEON
> > Intrinsics in the PowerPC LLVM backend. I am still at the beginning
> > of my efforts and am not yet familiar with either the ARM or the
> > PowerPC backends. After I started investigating the code and found
> > out that in total it is more than 100 kloc for the two backends I
> > thought it is a good idea to ask you for some hints of where I
> > should start from.
> >
> > I have written a small unrelated experimental backend for LLVM
> > before, so I have some experience with the topic.
> >
> >
> > Thanks,
> > - Stan
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
>
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As crazy as this is, the reverse (AltiVec intrinsics on ARM hardware) was
working in tree for a while for the common functions.

Another approach would be to develop a libTooling tool that helps rewrite
processor-specific SIMD code to use some generic SIMD library (a C++1y one?) and
provide ports of that library.

Alex
> On Oct 1, 2013, at 9:14 AM, Stanislav Manilov <stanislav.manilov at
gmail.com> wrote:
> 
> Hello LLVM Devs,
> 
> Thanks for helping me previously to cross-compile for ARM, I managed to get
a working toolchain and am currently having fun compiling different toy problems
and running them on a pandaboard.
> 
> As part of my research I am trying to implement the ARM NEON Intrinsics in
the PowerPC LLVM backend. I am still at the beginning of my efforts and am not
yet familiar with either the ARM or the PowerPC backends. After I started
investigating the code and found out that in total it is more than 100 kloc for
the two backends I thought it is a good idea to ask you for some hints of where
I should start from.
> 
> I have written a small unrelated experimental backend for LLVM before, so I
have some experience with the topic.
> 
> Thanks,
>  - Stan
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev