Abstract

Abstract- This paper describes techniques for optimizing range checks performed to detect array bound violations. In addition to the elimination of range check:s, the optimizations discussed in this paper also reduce the overhead due to range checks that cannot be eliminated by compile-time analysis. The optimizations reduce the program execution time and the object code size through elimination of redundant checks, propagation of checks out of loops, and combination of multiple checks into a single check. A minimal control flow graph (MCFG) is constructed using which the minimal amount of data flow information required for range check optimizations is com-puted. The range check optimizations are per-formed using the MCFG rather the CFG for the entire program. This allows the global range check optimizations to be performed efficiently since the MCFG is significantly smaller than the CFG. Any array bound violation that is detected by a program with all range checks included, will also be detel:ted by the program after range check optimization and vice versa. Even though the above optimizations may appear to be similar to traditional code optimizations, similar reduction in the number of range checks executed can not be achieved by a traditional code optimizer. Experi-mental results indicate that the number of range checks performed in executing a program is greatly reduced using the above techniques.

Citations

295	Constant propagation with conditional branches - Wegman, Zadeck - 1991
76	Compiler analysis of the value ranges for variables - Harrison - 1977
66	A portable machine-independent global optimizer–design and measurements - Chow - 1984
58	K.: Implementation of an array bound checker - Suzuki, Ishihata - 1977
46	Optimization of range checking - Markstein, Cocke, et al. - 1982
1	Symbolic Debugging of Optimized Code,” Trans - Hennessy - 1982