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Scientific Programming
Volume 9, Issue 2-3, Pages 131-142

Compiler Optimization Techniques for OpenMP Programs

Shigehisa Satoh,1 Kazuhiro Kusano,2 and Mitsuhisa Sato3

1Systems Development Laboratory, Hitachi, Ltd., 1099 Ohzenji, Asao, Kawasaki, Kanagawa 215-0013, Japan
21st Computers Software Division, NEC Solutions, NEC Corporation, 1-10 Nissin-cho, Fuchu, Tokyo 183-8501, Japan
3Center for Computational Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan

Received 29 January 2002; Accepted 29 January 2002

Copyright © 2001 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We have developed compiler optimization techniques for explicit parallel programs using the OpenMP API. To enable optimization across threads, we designed dataflow analysis techniques in which interactions between threads are effectively modeled. Structured description of parallelism and relaxed memory consistency in OpenMP make the analyses effective and efficient. We developed algorithms for reaching definitions analysis, memory synchronization analysis, and cross-loop data dependence analysis for parallel loops. Our primary target is compiler-directed software distributed shared memory systems in which aggressive compiler optimizations for software-implemented coherence schemes are crucial to obtaining good performance. We also developed optimizations applicable to general OpenMP implementations, namely redundant barrier removal and privatization of dynamically allocated objects. Experimental results for the coherency optimization show that aggressive compiler optimizations are quite effective for a shared-write intensive program because the coherence-induced communication volume in such a program is much larger than that in shared-read intensive programs.