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This is a list of the instructions that make up the Java bytecode, an abstract machine language that is ultimately executed by the Java virtual machine. [1] The Java bytecode is generated from languages running on the Java Platform, most notably the Java programming language.
The runtime overhead of added instrumentation is small (5–20%) and the bytecode instrumentor itself is very fast (mostly limited by file I/O speed). Memory overhead is a few hundred bytes per Java class. EMMA is 100% pure Java, has no external library dependencies, and works in any Java 2 JVM (even 1.2.x).
Since the late 1990s, the execution speed of Java programs improved significantly via introduction of just-in-time compilation (JIT) (in 1997 for Java 1.1), [2] [3] [4] the addition of language features supporting better code analysis, and optimizations in the JVM (such as HotSpot becoming the default for Sun's JVM in 2000).
For this reason, MIPS has become not a measure of instruction execution speed, but task performance speed compared to a reference. In the late 1970s, minicomputer performance was compared using VAX MIPS , where computers were measured on a task and their performance rated against the VAX-11/780 that was marketed as a 1 MIPS machine.
Java bytecode is the instruction set of the Java virtual machine (JVM), the language to which Java and other JVM-compatible source code is compiled. [1] Each instruction is represented by a single byte , hence the name bytecode , making it a compact form of data .
Loop unrolling, also known as loop unwinding, is a loop transformation technique that attempts to optimize a program's execution speed at the expense of its binary size, which is an approach known as space–time tradeoff.
For example, with six executions units, six new instructions are fetched in stage 1 only after the six previous instructions finish at stage 5, therefore on average the number of clock cycles it takes to execute an instruction is 5/6 (CPI = 5/6 < 1). To get better CPI values with pipelining, there must be at least two execution units.
The Jazelle instruction set is well documented as Java bytecode.However, ARM has not released details on the exact execution environment details; the documentation provided with Sun's HotSpot Java Virtual Machine goes as far as to state: "For the avoidance of doubt, distribution of products containing software code to exercise the BXJ instruction and enable the use of the ARM Jazelle ...