Affiliations: Tsukuba Research Center, Real World Computing
Partnership, 1-6-1 Takezono, Tsukuba, Ibaraki 305-0032, Japan. E-mail:
{sh-sato,kusano,msato}@trc.rwcp.or.jp. Present addresses: Systems
Development Laboratory, Hitachi, Ltd., 1099 Ohzenji, Asao, Kawasaki, Kanagawa
215-0013, Japan | 1st Computers Software Division, NEC Solutions, NEC
Corporation, 1-10 Nissin-cho, Fuchu, Tokyo 183-8501, Japan | Center for Computational Physics, University of
Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
Abstract: 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.
