[mbfg]

It compiles code to an "idealized" instruction set. That instruction set is then mapped to a real instruction set by the jvm at runtime, first in some cases through interpretation, but mostly by recompiling it (potentially better and better as more statistics come in) by the jvm.

A big advantage to this approach has (over the instruction set independence), is the JVM knows exactly what the characteristics of the environment are, cache size, memory size, processor extensions, etc, etc, and can decide at runtime how to compile best. This is in contrast to like a C compiler that will give users compile switches to pick a target environment (which is only sometimes correct).