Author Topic: BCEL instruction  (Read 4309 times)

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Offline meteor

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BCEL instruction
« on: February 01, 2012, 01:01:27 pm »
Hi all,

I am trying to write a timing strategy for Volta, an execution time analyzer for Java processors. In Volta, the execution time of a Java Bytecode instruction is determined with the following method:

public int getCycles(Instruction instruction)

This method looks up the instruction time of the Instruction. The class Instruction of BCEL is used: Instruction (http://commons.apache.org/bcel/apidocs/org/apache/bcel/generic/Instruction.html?is-external=true)

For example, getCycles(BIPUSH) returns "2", meaning it takes 2 cycles on a java processor to execute a bipush bytecode.

Okay, now the problem. On a particular Java processor, the execution time of the instruction varies with the argument. For example, using LDC to load an integer takes 7 cycles. Using LDC to load a string takes 3 cycles.

Therefore, I need to know exactly what an Instruction does, just the opcode isn't enough. Does anybody know how to do this? I might be able to get the index used by the LDC instruction with

instruction.getIndex();

but how can I determine which constant is actually loaded?

 

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