Fully Distributed On-chip Instruction Memory Design for Stream Architecture Based on Field-Divided VLIW Compression

Huge code size and poor code density have always been a serious problem in VLIW processor. In order to deal with the problem and its influence on the instruction memory in stream architecture, this paper proposes a novel method called field-divided VLIW compression through analyzing the code characteristics of stream program across a wide range of typical stream application domains and dividing the instruction code unrelated to each other into different subfields. Based on the field-divided VLIW compression, this paper designs a fully distributed on-chip instruction memory (FDIM) for stream architecture. The experiment on MASA stream processor demonstrates that the field-divided VLIW compression can reduce about 38% of off-chip instruction code and about 66% of on-chip instruction memory space demand in the case of having little influence on the program performance; FDIM reduces the area of on-chip instruction memory by about 37%, thus reduces the area of the MASA stream processor by about 8.92%. Besides, the energy consumption of instruction memory is decreased by about 61%.