OP2-Clang: A source-to-source translator using Clang/LLVM LibTooling

Abstract text:

OP2-Clang: A source-to-source translator using Clang/LLVM LibTooling

Gábor Dániel Balogh1, Gihan R. Mudalige2 and István Zoltán Reguly1

1 Pázmány Péter Catholic University, Information Technology and Bionics
2 The University of Warwick, Department of Computer Science

Correspondence: balogh.gabor.daniel@hallgato.ppke.hu

Domain Specific Languages or Active Library frameworks have recently emerged as
an important method for gaining performance portability, where an application
can be efficiently executed on a wide range of HPC architectures without
significant manual modifications. Embedded DSLs such as OP2, provides an API
embedded in general purpose languages such as C/C++/Fortran. They rely on
source-to-source translation and code refactorization to translate the
higher-level API calls to platform specific parallel implementations. OP2 that
provides a high-level API for the solution of unstructured-mesh computations can
generate a wide range of parallel implantations for execution on architectures
such as CPUs, GPUs, distributed memory clusters and heterogeneous processors
making use of radical platform specific optimizations. Compiler tool-chains
supporting source-to-source translation of code written in mainstream languages
currently lacks the capabilities to carry out such wide-ranging code
transformations. Clang/LLVMís Tooling library (LibTooling) has long been touted
as having such capabilities but have only demonstrated its use in simple source
refactoring tasks.

In this talk we introduce OP2-Clang, a source-to-source translator based on
LibTooling, for OP2's C/C++ API, capable of generating target parallel
code based on SIMD, OpenMP, CUDA and their combinations with MPI. OP2-Clang is
designed to significantly reduce maintenance, particularly making it easy to be
extended to generate new paralleizations and optimizations for hardware
platforms. In this research, we demonstrate its capabilities including (1) the
use of LibToolingís AST matchers together with a novel strategy that use
parallelization templates or skeletons to significantly reduce the complexity of
generating radically different and transformed target code and (2) the
generation of optimized kernels for computation loops with indirections for two
industrial representative unstructured-mesh applications. We determine the
current limits of LibTooling to support the source-to-source translations in
eDSLs such as OP2 and provide recommendations for its future development to
facilitate code-generation requirements of such frameworks.

Gábor Dániel Balogh

End of talk: 6/21/2018 11:40:00 AM

Start of talk: 6/21/2018 11:20:00 AM