Constraint driven code selection for fixed-point DSPs

Fixed-point DSPs are a class of embedded processors with highly irregular architectures. This irregularity makes it difficult to generate high-quality machine code from programming languages such as C. In this paper we present a novel constraint driven approach to code selection for irregular processor architectures, which provides a twofold improvement of earlier work. First, it handles complete data flow graphs instead of trees and thereby generates better code in the presence of common subexpressions. Second, the presented technique is not restricted to computation of a single solution, but it generates alternative solutions. This feature enables the tight coupling of different code generation phases, resulting in better exploitation of instruction-level parallelism. Experimental results indicate that our technique is capable of generating machine code that competes well with handwritten assembly code.