RFR: 8196331: Optimize Character.digit for latin1 input

[Paul Sandoz]

Smaller in only the upper bound? I would an explicit upper bounds check would dominate that of the bounds check for the array itself.

Paul.

> On Jan 29, 2018, at 11:37 AM, Claes Redestad <claes.redestad at oracle.com> wrote:
> 
> I ran with a smaller byte[] initially and saw about a 10% improvement from removing the branch, which is why I felt the superfluous bytes were motivated.
> 
> /Claes
> 
> Paul Sandoz <paul.sandoz at oracle.com> skrev: (29 januari 2018 19:14:44 CET)
> 
> 
>  On Jan 29, 2018, at 9:44 AM, Martin Buchholz <martinrb at google.com> wrote:
>  
>  Thanks.  I might try to shrink the size of the static array, by only
>  storing values between '0' and 'z', at the cost of slightly greater lookup
>  costs for each char.
>  
> 
> I was wondering the same, or just clip the end of the array to’z'
> 
> if (ch <= ‘z’ && radix …) { // Might even fold the upper bounds check for DIGITS
>   value = DIGITS[ch];
>   ...
> }
> 
> Paul.
> 
>  On Mon, Jan 29, 2018 at 3:15 AM, Claes Redestad <claes.redestad at oracle.com>
>  wrote:
>  
>  Hi,
>  
>  for the latin1 block of CharacterData we can improve the
>  digit(int, int) implementation by providing an optimized lookup
>  table. This improves microbenchmarks exercising Integer.parseInt,
>  Long.parseLong and UUID.fromString etc by around 50%for typical
>  inputs.
>  
>  Webrev: http://cr.openjdk.java.net/~redestad/8196331/open.00/ <http://cr.openjdk.java.net/~redestad/8196331/open.00/>
>  Bug: https://bugs.openjdk.java.net/browse/JDK-8196331 <https://bugs.openjdk.java.net/browse/JDK-8196331>
>  
>  The lookup array is pre-calculated to minimize startup impact
>  (adds 1,027 bytecodes executed during initialization)
>  
>  /Claes
>  
> 
> 
> -- 
> Sent from my Android device with K-9 Mail. Please excuse my brevity.