[intrinsics] performance improvements for the intrinsified version of Objects::hash

[Alex Buckley]

// Adopting a zero-decimal-places policy because precision to multiple 
decimal places is less important than accuracy and repeatability.

On 3/4/2019 4:28 PM, Vicente Romero wrote:
> I have uploaded another round of experiments for Objects::hash, see [1].
> The main variation I have included a variant of most of the tests in
> which instead of invoking Objects::hash 10 times sequentially, the same
> invocation occurs inside a loop which is executed 10 times. This shows
> that when the call site is reused, the execution time trumps vanilla
> JDK13 most of the time.

That's not really the story though :-) Yes, the *Int*StringsLoop10 tests 
run faster with intrinsified invocation than with vanilla invocation, 
but generally, the *Int*StringsLoop10 tests enjoy less impressive 
speedups than the *Int*Strings tests. (Example: 25Int25Strings gets a 
21x speedup, but 25Int25StringsLoop10 only gets a 2x speedup.)

This is because the *Int*StringsLoop10 tests already run faster on 
vanilla JDK 13 than the *Int*Strings tests, presumably thanks to 
inlining ("the call site is reused").

I guess that 1IntLoop10, 2IntsLoop10, and 2Ints2StringsLoop10 would have 
such high throughput on vanilla JDK 13 that their speedups with 
intrinsification might be significantly <1.

Alex