Evaluating Runtime - Compiled Value - Speci c Optimizations 1 Evaluating Runtime - Compiled Value - Speci c Optimizations

Traditional compiler optimizations are either dataindependent or optimize around common data values while retaining correct behavior for uncommon values. This paper examines value-speci c data-dependent optimizations (VSO), where code is optimized at runtime around particular input values. Because VSO optimizes for the speci c case, the resulting code is more e cient. However, since optimization is performed at runtime, the performance improvement must more than pay for the runtime compile costs. We describe two VSO implementation techniques and compare the performance of applications that have been implemented using both VSO and static code. The results demonstrate that VSO produces better code and often for reasonable input sizes. The machine-independent implementations showed speedups of up to 1.5 over static C code, and the machine-dependent versions showed speedups of up to 4.3 over static assembly code.