review (M) for 4809552: Optimize Arrays.fill(...)

[Ulf Zibis]

A comment aside:
Having:
     int[] ia = new int[SIZE];
     Arrays.fill(ia, 1234);

The 1st line causes the array to be first filled with zeroes according 
the JLS.
The 2nd line causes the array to be *again* filled with 1234's.

This situation could be optimized by the JIT in skipping the zero-filling.
Maybe this is just done by HotSpot, then forget my 2 cents.

1 cent more:
To give programmer better control of that and to enhance the interpreter 
in the same way, we would need to have an additional syntax, something 
like:
int [] ia = new int[SIZE](1234); // Project Coin candidate!

-Ulf


Am 20.08.2010 00:11, schrieb Tom Rodriguez:
> 4809552: Optimize Arrays.fill(...)
> Reviewed-by:
>
> This adds new logic to recognize fill idioms and convert them into a
> call to an optimized fill routine.  Loop predication creates easily
> matched loops that are simply replaced with calls to the new assembly
> stubs.  Currently only 1,2 and 4 byte primitive types are supported.
> Objects and longs/double will be supported in a later putback.  Tested
> with runthese, nsk and ctw plus jbb2005.
>
> http://cr.openjdk.java.net/~never/4809552
>
>
>    
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