AUTOSCALER for C: an optimizing floating-point to integer C program converter for fixed-point digital signal processors

Abstract

A translator which converts C-based floating-point digital signal processing programs to optimized integer C versions is developed for convenient programming and efficient use of fixed-point digital signal processors (DSPs). It not only converts data types and supports automatic scaling, but also conducts shift optimization to enhance execution speed. Since the input and output of this translator are ANSI C compliant programs, it can be used for any fixed-point DSP that supports ANSI C compiler. The number of shift operations that are required for scaling in the converted integer programs is reduced by equalizing the integer word-lengths of relevant variables and constants. For an optimal reduction, a cost function that represents the overhead of scaling is formulated by considering the data- path of a target processor, program parsing, and profiling results. This cost function is then minimized by using either integer linear programming or simulated annealing algorithms. The translated integer C codes are 5-400 times faster than the floating-point versions when applied to TMS320C50, TMS320C60 and Motorola 56000 DSPs.