Re: JavaMemoryModel: Array

From: Cliff Click (
Date: Mon Dec 10 2001 - 12:07:20 EST

Jean-Philippe Lesot wrote:

> Hello,
> Sorry if my question is out of topic in this mailing list.
> I know quite well mechanismes inside a JVM but I don't know what a java
> compiler is allowed to do to optimize Java _bytecode_. Because array
> elements can't be volatile, it is not clear for me what is possible: (i) Is
> it possible for a java compiler to optimize two consecutive writes (e.g.
> IASTORE) at the same index in only one?

Certainly possible. Most modern JITs do this.

> (ii) It is possible for a java
> compiler to reorder writes in two different arrays?


> I need a way to prevent
> such optimizations without using method call but using classic array access.
> Is it possible in the present Java Memory Model? And in your proposition?

Insert a lock/unlock between the array refs.

> Thanks you for your help, and sorry for my English.
> Bye,
> Jp.


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