Language Implementation Patterns

Pattern 28

Register-Based Bytecode Interpreter

Purpose

This pattern executes bytecode instructions that store function parameters, local variables, and temporary values in simulated registers.

Discussion

A register-based bytecode interpreter is identical to a stack-based interpreter except for the instruction set and where it keeps local variables, parameters, return values, and any temporary values. The instructions use registers instead of an operand stack. Our simulated machine gives each stack frame an “infinite” set of registers.

Table 9. Register-based arithmetic bytecode instructions

Instruction	Description
iadd ri, rj, rk isub ri, rj, rk imul ri, rj, rk	Arithmetic operators for integers. rk=ri op rj
fadd ri, rj, rk fsub ri, rj, rk fmul ri, ...