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

[Tom Rodriguez]

On Aug 20, 2010, at 3:20 AM, Ulf Zibis wrote:

> 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. 

My change will skip the initial zeroing and replace it by the work done in the fill.

tom

> 
> 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
>> 
>> 
>> 
>>   
>>