Translation to MIPS Code

This JDK release includes support for translating Java bytecode to MIPS machine code and running it instead of the bytecode in order to improve Java runtime performance.

java, the Java virtual machine, and appletviewer, the Java applet viewer, are able to translate the code for each class when it is loaded, and then subsequently to use the MIPS code. This is called JIT (Just In Time) compilation. It is turned on and off by the -jit and -nojit options, and is on by default.

In previous releases, MIPS code could be generated ahead of time using the tool javat, in order to avoid doing this translation every time a program was run. Due to the speed of our JIT compiler, and particularly now because translation is done at a method (rather than class) granularity, this capability is not generally beneficial, so it is no longer provided.

MIPS code execution is not available:

• on systems with R4000 processors, revisions 3.0 and earlier
• when a program is being debugged

Also, the -prof option to java does not work properly in the presence of MIPS code execution. If you use the -prof option, use the -nojit option also.

JIT and your Web Browser

Having this software installed does not automatically mean that JIT compilation will be in effect when running Java applets in your Web browser.

• If you use Netscape, you will not have the advantage of a JIT compiler unless you use SGI's release of Netscape Communicator 4.05. A version of this will be included in IRIX 6.5, and an updated version will appear on Silicon Surf in the very near future.
  
  
• If you use a Web browser written in Java (such as hotjava), and you run the browser using this Java implementation, the JIT compiler will be used.

  In order to run hotjava, download it from Sun, unzip it, and set your JDK_HOME environment variable to point to where you have installed the Java software:

  • setenv JDK_HOME /usr/java

  You should then be able to run hotjava out of the distribution's bin directory.

  If you downloaded a hotjava distribution containing a runtime directory, you can remove it, since it is a Solaris Java implementation.

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