Using register-transfer paths in code generation for heterogeneous memory-register architectures

In this paper we address the problem of code generation for basic blocks in heterogeneous memory-register DSP processors. We propose a new a technique, based on register-transfer paths, that can be used for efficiently dismantling basic block DAGs (Directed Acyclic Graphs) into expression trees. This approach builds on recent results which report optimal code generation algorithm for expression trees for these architectures. This technique has been implemented and experimentally validated for the TMS320C25, a popular fixed point DSP processor. The results show that good code quality can be obtained using the proposed technique. An analysis of the type of DAGs found in the DSPstone benchmark programs reveals that the majority of basic blocks in this benchmark set are expression trees and leaf DAGs. This leads to our claim that tree based algorithms, like the one described in this paper, should be the technique of choice for basic blocks code generation with heterogeneous memory register architectures.