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From "Caldarale, Charles R" <Chuck.Caldar...@unisys.com>
Subject RE: Java 1.6
Date Wed, 26 Sep 2007 19:26:35 GMT
> From: Christopher Schultz [mailto:chris@christopherschultz.net] 
> Subject: Re: Java 1.6
> 
> Really? Other than crap like auto-boxing, attributes, and 
> foreach-style 'for' syntax, what has the compiler done for
> me, lately? I see all that as syntactic sugar.

Agreed, that is just syntax "enhancement".  I was referring to byte code
generation, which has improved somewhat over the years.  (I don't have
any numbers, though.)

> Has the bytecode emitted by previous versions been perticularly
> non-optimized?

Loops have gotten better, and there's less wasted byte codes (e.g.,
computations whose results aren't stored anywhere now usually don't
generate any code rather than just being discarded at the end with a pop
of the operand stack).  The JITs usually took care of this anyhow, but
the first few thousand trips through a given method via the interpreter
would suffer.

> I suppose by "leaner", I meant in terms of required RAM.

Not sure about that.  A lot of the JIT-related performance improvement
is due to increased inlining and loop unrolling; those techniques
consume more memory per method, not less.

 - Chuck


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