Reverse compilation for digital signal processors: a working example

We describe the implementation and use of a reverse compiler from Analog Devices 21xx assembler source to ANSI-C (with optional use of the language extensions for the TMS320C6x processors) which has been used to port substantial applications. The main results of this work are that reverse compilation is feasible and that some of the features that make small DSPs hard to compile for, actually assist the process of reverse compilation compared to that of a general purpose processor. The article presents statistics on the occurrence of non-statically visible features of handwritten assembler code. It also looks at the quality of the code generated by an optimising ANSI-C compiler from our reverse compiled source and compares it to code generated from conventionally authored ANSI-C programs.