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

[Hannes Wallnöfer]

Vicente,

could it be that your your change in Object::hash bootstraps[1] mostly benefits invocations with very large numbers of parameters (like your original 100 parameter tests) but hurts performance with medium-to-lower number of parameters? I don’t have your latest benchmark sources, but I did some quick tests such as a testHash5Ints5Strings that suggest that may be the case.

[1] http://hg.openjdk.java.net/amber/amber/rev/0f40d5752eb9

Hannes


> Am 05.03.2019 um 03:52 schrieb Vicente Romero <vicente.romero at oracle.com>:
> 
> 
> 
> On 3/4/19 8:11 PM, Alex Buckley wrote:
>> // 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.
> 
> not in all cases, see [1] the new information is highlighted in yellow
>> 
>> Alex
> 
> Vicente
> 
> [1] http://cr.openjdk.java.net/~vromero/intrinsics_benchmark_results/benchmarkResults_intrinsics_all_data_v4.html