Exploiting Java bytecode parallelism by enhanced POC folding model

Abstract

Instruction-level parallelism of stack codes like Java is severely limited by accessing the operand stack sequentially. To resolve this problem in Java processor design, our earlier works have presented stack operations folding to reduce the number of push/pop operations in between the operand stack and the local variable. In those studies, Java bytecodes are classified into three major POC types. Statistical data indicates that the 4-foldable strategy of the POC folding model can eliminate 86% of push/pop operations. In this research note, we propose an Enhanced POC (EPOC) folding model to eliminate more than 99% of push/pop operations with an instruction buffer size of 8 bytes and the same 4-foldable strategy. The average issued instructions per cycle for a single pipelined architecture is further enhanced from 1.70 to 1.87.