Implementing Jalapeño in Java

Abstract

Jalape~no is a virtual machine for Java TM servers written in Java. A running Java program involves four layers of functionality: the user code, the virtual-machine, the operating system, and the hardware. By drawing the Java / non-Java boundary below the virtual machine rather than above it, Jalape~no reduces the boundary-crossing overhead and opens up more opportunities for optimization. To get Jalape~no started, a boot image of a working Jalape ~no virtual machine is concocted and written to a file. Later, this file can be loaded into memory and executed. Because the boot image consists entirely of Java objects, it can be concocted by a Java program that runs in any JVM. This program uses reflection to convert the boot image into Jalape~no's object format. A special Magic class allows unsafe casts and direct access to the hardware. Methods of this class are recognized by Jalape~no's three compilers, which ignore their bytecodes and emit special-purpose machine code. User code w...