[llvm-dev] Looking for suggestions: Inferring GPU memory accesses

Johannes Doerfert via llvm-dev llvm-dev at lists.llvm.org
Sun Aug 23 09:47:55 PDT 2020

Hi Ees,

a while back we started a project with similar scope.
Unfortunately the development slowed down and the plans to revive it 
this summer got tanked by the US travel restrictions.

Anyway, there is some some existing code that might be useful, though in 
a prototype stage. While I'm obviously biased, I would suggest we 
continue from there.

@Alex @Holger can we put the latest version on github or some other 
place to share it, I'm unsure if the code I (might have) access to is 
the latest.

@Ees I attached a recent paper and you might find the following links 

    * 2017 LLVM Developers’ Meeting: J. Doerfert “Polyhedral Value & 
Memory Analysis ” https://youtu.be/xSA0XLYJ-G0

    * "Automated Partitioning of Data-Parallel Kernels using Polyhedral 
Compilation.", P2S2 2020 (slides and video 

Let us know what you think :)

~ Johannes

On 8/22/20 9:38 AM, Ees Kee via llvm-dev wrote:
 > Hi all,
 > As part of my research I want to investigate the relation between the
 > grid's geometry and the memory accesses of a kernel in common gpu
 > benchmarks (e.g Rodinia, Polybench etc). As a first step i want to
 > answer the following question:
 > - Given a kernel function with M possible memory accesses. For how 
many of
 > those M accesses we can statically infer its location given concrete 
 > for the grid/block and executing thread?
 > (Assume CUDA only for now)
 > My initial idea is to replace all uses of dim-related values, e.g:
 >     __cuda_builtin_blockDim_t::__fetch_builtin_x()
 >     __cuda_builtin_gridDim_t::__fetch_builtin_x()
 > and index related values, e.g:
 >     __cuda_builtin_blockIdx_t::__fetch_builtin_x()
 >     __cuda_builtin_threadIdx_t::__fetch_builtin_x()
 > with ConstantInts. Then run constant folding on the result and check how
 > many GEPs have constant values.
 > Would something like this work or are there complications I am not 
 > of? I'd appreciate any suggestions.
 > P.S i am new to LLVM
 > Thanks in advance,
 > Ees
 > _______________________________________________
 > LLVM Developers mailing list
 > llvm-dev at lists.llvm.org
 > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

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