在嵌入式Java芯片中使用即时编译技术

Java虚拟机具有面向堆栈与面向对象的特点，不利于硬件有效支持字节码的直接执行，传统JIT也不适应嵌入式系统的应用环境，介绍了在自行设计的嵌入式Java芯片中使用JIT的技术途径，通过对Java虚拟机堆栈和复杂指令的支持，密切配合JIT软件，较好地解决了Java芯片设计中的问题。测试结果表明，相对于目前前界最好的picoJava-Ⅱ内核而言内核而言，JC401的编译后代码性能提高了1．2至1．9倍，在硬件复杂度、执行速度、内存开销等方面都有较大程度的改善，适合于嵌入式应用。

APPLYING JUST IN TIME COMPILING TECHNOLOGY IN EMBEDDED JAVA CHIP

The Java virtual machine is stack based and object oriented. These features are not suitable for the hardware to execute the bytecodes directly, and the traditional just in time (JIT) compilers can't meet the requirements of embedded system too. It is really a great challenge to design a good embedded Java chip. Introduced in this paper is the approach used in embedded Java chip JC401. With the support of the stack architecture and complicated instructions of Java virtual machine, and close matched with the JIT compiler and other software techniques, the problems in Java chip design have been overcome. The result of simulation indicates that the compiled Java programs in JC401 are 1.2 to 1.9 times as fast as the picoJava II which has the best performance in the existing Java chips, while the compiling cost can be ignored and JC401 improves considerably in hardware complex, native performance, and memory cost, compared with picoJava II. So the JC401 is suitable for embedded systems, and can provide high Java performance for embedded applications.