RFR: 8244413: Avoid rebinds in MethodHandle.viewAsType

[Claes Redestad]

On 2020-05-06 00:34, Claes Redestad wrote:
> Hi Mandy,
> 
> On 2020-05-06 00:23, Mandy Chung wrote:
>>
>> This looks good.
> 
> thanks!

Pushed.

FTR, I took inventory of existing micros, and found a few where
the effect of this change on capturing lambdas can be studied.

For example:

$ make build-microbenchmark
$ java -jar build/linux-x64/images/test/micro/benchmarks.jar 
Capture.*lambda_01$ -f 1 -w 1 -r 1

As expected, no statistically significant effect after JIT:

         Benchmark           Mode  Cnt  Score   Error  Units
15-b19  Capture0.lambda_01  avgt    5  5.444 ± 0.872  ns/op
15-b20  Capture0.lambda_01  avgt    5  5.516 ± 1.199  ns/op
jdk     Capture0.lambda_01  avgt    5  5.465 ± 1.101  ns/op

-Xint:
         Benchmark           Mode  Cnt    Score   Error  Units
15-b19  Capture0.lambda_01  avgt    5  616.555 ± 2.732  ns/op
15-b20  Capture0.lambda_01  avgt    5  859.594 ± 7.954  ns/op
jdk     Capture0.lambda_01  avgt    5  745.150 ± 1.821  ns/op

-XX:TieredStopAtLevel=1:
         Benchmark           Mode  Cnt    Score   Error  Units
15-b19  Capture0.lambda_01  avgt    5    6.312 ± 0.919  ns/op
15-b20  Capture0.lambda_01  avgt    5  105.761 ± 7.575  ns/op
jdk     Capture0.lambda_01  avgt    5  105.228 ± 7.175  ns/op

So outside of the direct bootstrap improvement, there's a positive
effect during early warmup. Sadly this patch doesn't translate into an
improvement in C1. I can see a rather large regression in C1 on this
specific micro in 15-b20 (which is where the Hidden Classes integration
happened).

/Claes