Based on the equivalence a[x & (a.length - 1)] throws if and only if a.length == 0, I'm proposing this simple algorithm:
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Hi Martin and John,

I did a quick-and-dirty patch and it seems to work: https://gist.github.com/rednaxelafx/8964030
If it looks right then I'll refactor that code a little bit and send it in for official review.

- Kris


On Wed, Feb 12, 2014 at 11:17 AM, John Rose <john.r.rose@oracle.com> wrote:
It's totally reasonable, and is already filed as an RFE (please comment on it!):


— John

On Feb 12, 2014, at 9:40 AM, Martin Grajcar <maaartinus@gmail.com> wrote:

Most hash tables are power-of-two sized so that they can use masking for the access. It looks like the bounds check doesn't get eliminated, although it could be.


Based on the equivalence a[x & (a.length - 1)] throws if and only if a.length == 0, I'm proposing this simple algorithm:


  • For each array access, check if the index has been computed via a bitwise and.

  • If so, check if either of the operands was computed as length minus one.

  • If so, replace the bounds check by a zero-length check.

This zero-length check can then be easily moved out of the loop by the existing optimizations.

I hope I'm not talking non-sense. For more details see 

Regards,
Martin.