Assembly Code Conversion of Software-Pipelined Loop between two VLIW DSP Processors

In order to fully utilize the instruction level parallelism of VLIW DSP processors, DSP programs have to be optimized by software pipelining. Software pipelining has been studied for many years and widely implemented in optimizing compilers. However, due to the rearrangement of the original instructions, it is often very difficult to re-use or port the code of a software-pipelined loop to other processors. In this paper we present a practical approach to solve this problem. Our approach involves the following steps: (1) Using a newly developed software de-pipelining algorithm to convert the assembly code of a software-pipelined loop to a semantically equivalent sequential loop; (2) Using our pattern mapping technique to convert the sequential loop to a machineindependent high-level intermediate code; (3) Converting the machine-independent intermediate code to that of the target machine; (4) Feed the intermediate code of the target machine to the backend of the compiler of the target machine to obtain the optimized assembly code of the target DSP processor We have conducted a series of experiments using the popular TIC62 as the source DSP and SC140 as the target DSP. Six DSP kernel programs have been selected for the experiments. To verify the validity of the converted code, we have used a simulator to compare the results of various steps in the conversion process. All the results of our experiments show that the converted assembly code of target DSP processor are correct with comparable performance to the assembly code directly generated by compiling the source code with the optimizing compiler of the target machine.