Flacc: Towards OpenACC support for Fortran in the LLVM Ecosystem

Valentin Clement; Jeffrey S. Vetter

doi:10.1109/LLVMHPC54804.2021.00007

Flacc: Towards OpenACC support for Fortran in the LLVM Ecosystem

Valentin Clement, Jeffrey S. Vetter

Computer Science and Mathematics Div

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

4 Scopus citations

Abstract

OpenACC is a directive-based programming model for heterogeneous accelerators initially launched in 2010 to provide a portable solution at a level of abstraction above OpenCL, CUDA, and other lower-level programming models. Various implementations of OpenACC for C, C++, and Fortran exist; however, only one open-source, production implementation of OpenACC for Fortran does exist. Moreover, most contemporary compiler tool chains for heterogeneous computing are based on LLVM. This lack of support poses a serious risk for high-performance computing application developers targeting GPUs and other accelerators, and it limits the ability of the community to experiment with, extend, and contribute to the OpenACC specification and open-source implementation itself. To address this gap, we have designed and begun implementing Flacc: An effort funded by the US Exascale Computing Project to develop production OpenACC compiler support for Fortran based on Flang within the LLVM ecosystem. In this paper, we describe the Flacc goals, initial design and prototype, and challenges that we have encountered so far in our prototyping efforts. Flacc is implemented as a MLIR dialect in the Flang Fortran front end in LLVM. The Flacc front end currently supports OpenACC version 3.1, and the Flacc run time is currently under development and relies on contributions from the Clacc project. Current contributions to Flacc are available in the main {\color{Green}{\mathbf{LLVM}}\;{\mathbf{repository}}}.1

Original language	English
Title of host publication	Proceedings of LLVM-HPC 2021
Subtitle of host publication	7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis
Publisher	Institute of Electrical and Electronics Engineers Inc.
Pages	12-19
Number of pages	8
ISBN (Electronic)	9781665411349
DOIs	https://doi.org/10.1109/LLVMHPC54804.2021.00007
State	Published - 2021
Event	7th IEEE/ACM Annual Workshop on the LLVM Compiler Infrastructure in HPC, LLVM-HPC 2021 - St. Louis, United States Duration: Nov 14 2021 → …

Publication series

Name	Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis

Conference

Conference	7th IEEE/ACM Annual Workshop on the LLVM Compiler Infrastructure in HPC, LLVM-HPC 2021
Country/Territory	United States
City	St. Louis
Period	11/14/21 → …

Funding

This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725with the US Department of Energy (DOE), Office of Science. This research was supported by the Exascale Computing Project (17-SC-20-SC), a collaborative effort of the U.S. Department of Energy Office of Science and the National Nuclear Security Administration. This research used resources of the Experimental Computing Laboratory at the Oak Ridge National Laboratory, which is supported by the US Department of Energy’s Office of Science under Contract No. DE-AC05-00OR22725.

Keywords

GPU
LLVM
MLIR
OpenACC
OpenMP
accelerators
compiler
multicore

Access to Document

10.1109/LLVMHPC54804.2021.00007

Cite this

Clement, V., & Vetter, J. S. (2021). Flacc: Towards OpenACC support for Fortran in the LLVM Ecosystem. In Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis (pp. 12-19). (Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/LLVMHPC54804.2021.00007

Clement, Valentin ; Vetter, Jeffrey S. / Flacc : Towards OpenACC support for Fortran in the LLVM Ecosystem. Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis. Institute of Electrical and Electronics Engineers Inc., 2021. pp. 12-19 (Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis).

@inproceedings{b4bcdb7023f74ea1987a14f63d25a3ea,

title = "Flacc: Towards OpenACC support for Fortran in the LLVM Ecosystem",

abstract = "OpenACC is a directive-based programming model for heterogeneous accelerators initially launched in 2010 to provide a portable solution at a level of abstraction above OpenCL, CUDA, and other lower-level programming models. Various implementations of OpenACC for C, C++, and Fortran exist; however, only one open-source, production implementation of OpenACC for Fortran does exist. Moreover, most contemporary compiler tool chains for heterogeneous computing are based on LLVM. This lack of support poses a serious risk for high-performance computing application developers targeting GPUs and other accelerators, and it limits the ability of the community to experiment with, extend, and contribute to the OpenACC specification and open-source implementation itself. To address this gap, we have designed and begun implementing Flacc: An effort funded by the US Exascale Computing Project to develop production OpenACC compiler support for Fortran based on Flang within the LLVM ecosystem. In this paper, we describe the Flacc goals, initial design and prototype, and challenges that we have encountered so far in our prototyping efforts. Flacc is implemented as a MLIR dialect in the Flang Fortran front end in LLVM. The Flacc front end currently supports OpenACC version 3.1, and the Flacc run time is currently under development and relies on contributions from the Clacc project. Current contributions to Flacc are available in the main {\color{Green}{\mathbf{LLVM}}\;{\mathbf{repository}}}.1",

keywords = "GPU, LLVM, MLIR, OpenACC, OpenMP, accelerators, compiler, multicore",

author = "Valentin Clement and Vetter, {Jeffrey S.}",

note = "Publisher Copyright: {\textcopyright} 2021 IEEE.; 7th IEEE/ACM Annual Workshop on the LLVM Compiler Infrastructure in HPC, LLVM-HPC 2021 ; Conference date: 14-11-2021",

year = "2021",

doi = "10.1109/LLVMHPC54804.2021.00007",

language = "English",

series = "Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis",

publisher = "Institute of Electrical and Electronics Engineers Inc.",

pages = "12--19",

booktitle = "Proceedings of LLVM-HPC 2021",

}

Clement, V & Vetter, JS 2021, Flacc: Towards OpenACC support for Fortran in the LLVM Ecosystem. in Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis. Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis, Institute of Electrical and Electronics Engineers Inc., pp. 12-19, 7th IEEE/ACM Annual Workshop on the LLVM Compiler Infrastructure in HPC, LLVM-HPC 2021, St. Louis, United States, 11/14/21. https://doi.org/10.1109/LLVMHPC54804.2021.00007

Flacc: Towards OpenACC support for Fortran in the LLVM Ecosystem. / Clement, Valentin; Vetter, Jeffrey S.
Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis. Institute of Electrical and Electronics Engineers Inc., 2021. p. 12-19 (Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

TY - GEN

T1 - Flacc

T2 - 7th IEEE/ACM Annual Workshop on the LLVM Compiler Infrastructure in HPC, LLVM-HPC 2021

AU - Clement, Valentin

AU - Vetter, Jeffrey S.

PY - 2021

Y1 - 2021

N2 - OpenACC is a directive-based programming model for heterogeneous accelerators initially launched in 2010 to provide a portable solution at a level of abstraction above OpenCL, CUDA, and other lower-level programming models. Various implementations of OpenACC for C, C++, and Fortran exist; however, only one open-source, production implementation of OpenACC for Fortran does exist. Moreover, most contemporary compiler tool chains for heterogeneous computing are based on LLVM. This lack of support poses a serious risk for high-performance computing application developers targeting GPUs and other accelerators, and it limits the ability of the community to experiment with, extend, and contribute to the OpenACC specification and open-source implementation itself. To address this gap, we have designed and begun implementing Flacc: An effort funded by the US Exascale Computing Project to develop production OpenACC compiler support for Fortran based on Flang within the LLVM ecosystem. In this paper, we describe the Flacc goals, initial design and prototype, and challenges that we have encountered so far in our prototyping efforts. Flacc is implemented as a MLIR dialect in the Flang Fortran front end in LLVM. The Flacc front end currently supports OpenACC version 3.1, and the Flacc run time is currently under development and relies on contributions from the Clacc project. Current contributions to Flacc are available in the main {\color{Green}{\mathbf{LLVM}}\;{\mathbf{repository}}}.1

AB - OpenACC is a directive-based programming model for heterogeneous accelerators initially launched in 2010 to provide a portable solution at a level of abstraction above OpenCL, CUDA, and other lower-level programming models. Various implementations of OpenACC for C, C++, and Fortran exist; however, only one open-source, production implementation of OpenACC for Fortran does exist. Moreover, most contemporary compiler tool chains for heterogeneous computing are based on LLVM. This lack of support poses a serious risk for high-performance computing application developers targeting GPUs and other accelerators, and it limits the ability of the community to experiment with, extend, and contribute to the OpenACC specification and open-source implementation itself. To address this gap, we have designed and begun implementing Flacc: An effort funded by the US Exascale Computing Project to develop production OpenACC compiler support for Fortran based on Flang within the LLVM ecosystem. In this paper, we describe the Flacc goals, initial design and prototype, and challenges that we have encountered so far in our prototyping efforts. Flacc is implemented as a MLIR dialect in the Flang Fortran front end in LLVM. The Flacc front end currently supports OpenACC version 3.1, and the Flacc run time is currently under development and relies on contributions from the Clacc project. Current contributions to Flacc are available in the main {\color{Green}{\mathbf{LLVM}}\;{\mathbf{repository}}}.1

KW - GPU

KW - LLVM

KW - MLIR

KW - OpenACC

KW - OpenMP

KW - accelerators

KW - compiler

KW - multicore

UR - http://www.scopus.com/inward/record.url?scp=85124199183&partnerID=8YFLogxK

U2 - 10.1109/LLVMHPC54804.2021.00007

DO - 10.1109/LLVMHPC54804.2021.00007

M3 - Conference contribution

AN - SCOPUS:85124199183

T3 - Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis

SP - 12

EP - 19

BT - Proceedings of LLVM-HPC 2021

PB - Institute of Electrical and Electronics Engineers Inc.

Y2 - 14 November 2021

ER -

Clement V, Vetter JS. Flacc: Towards OpenACC support for Fortran in the LLVM Ecosystem. In Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis. Institute of Electrical and Electronics Engineers Inc. 2021. p. 12-19. (Proceedings of LLVM-HPC 2021: 7th Annual Workshop on the LLVM Compiler Infrastructure in HPC, Held in conjunction with SC 2021: The International Conference for High Performance Computing, Networking, Storage and Analysis). doi: 10.1109/LLVMHPC54804.2021.00007

Flacc: Towards OpenACC support for Fortran in the LLVM Ecosystem

Abstract

Publication series

Conference

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this