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From Tim Ellison <t.p.elli...@gmail.com>
Subject Re: RT: Escape analysis
Date Sun, 02 Oct 2005 19:42:19 GMT
What Brian fails to mention though is the speculative nature of such
optimizations in the presence of polymorphism.

Since Point and Component are not declared final/private they could at
some point be subclassed to, say, not simply return x from getx() or
return a new Point from getLocation().  Obviously if that happens the
pseudocode in listing 4 would do 'the wrong thing'.

The VM/JIT either has to be conservative, or able to undo such
speculative optimizations if the assumptions later prove false.  The
ability to undo optimizations requires some book-keeping.

Regards,
Tim

acoliver@apache.org wrote:
> http://www-128.ibm.com/developerworks/java/library/j-jtp09275.html - Yummy.
> 
> 

-- 

Tim Ellison (t.p.ellison@gmail.com)
IBM Java technology centre, UK.

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