Flamel: A High-Level Hardware Compiler

This paper describes the design and implementation of a high-level hardware compiler called Flamel. Ordinary Pascal programs are used to define the behavior required of the hardware. Flamel undertakes to find parallelism in the program, so it can produce a fast-running implementation that meets a user-specified cost bound. A number of program transformations create sections of code with more parallel computations than the original program has. A novel feature of Flamel is a method for organizing the search for the transformations that best satisfy the goal. Another new algorithm is one for "expression height reduction": rewriting an ensemble of expressions using algebraic properties in order to compute the expressions faster. An implementation of Flamel has been completed. The output is a description of a datapath and a controller, and at a sufficient level of detail so that good area and execution time figures can be estimated. On a series of tests, Flamel produces implementations of programs that would run 22 to 200 times faster than an MC68000 running the same programs, if the clock cycles were the same. The tests also show that a wide range of time-area tradeoffs are produced by varying the area constraint.