RFR (S) 8145428: Optimize StringUTF16 compress/copy methods for C1

[Xueming Shen]

+1

On 12/16/15, 11:11 AM, Aleksey Shipilev wrote:
> Hi,
>
> I would like to suggest a simple cleanup/improvement in current
> StringUTF16, which somewhat closes the gap between C1 and C2 performance
> with Compact Strings:
>    https://bugs.openjdk.java.net/browse/JDK-8145428
>    http://cr.openjdk.java.net/~shade/8145428/webrev.02/
>
> It does improve the score on C1 (-client) configurations significantly,
> without affecting C2 performance (because we basically modifying the
> code that C2 would overthrow with vectorized intrinsic):
>    http://cr.openjdk.java.net/~shade/8145428/notes.txt
>
> ...and the generated code looks much better now. It also alleviates some
> performance regressions on client configurations we observed in a
> regular performance testing.
>
> The subsequent improvements may further eliminate range checks, plus
> unroll/vectorize the loop, but I would like to defer that until array
> comparison intrinsics are stable and exposed to both C1 and C2.
>
> Testing: microbenchmarks, JPRT
>
> Thanks,
> -Aleksey
>