[patterns-instanceof-primitive] RFR: 8303374: Compiler Implementation for Primitive types in patterns, instanceof, and switch [v3]

[Aggelos Biboudis]

On Fri, 10 Mar 2023 18:12:32 GMT, Michael Hixson <duke at openjdk.org> wrote:

>> @michaelhixson The more compact variant given above in the comment by @biboudis, compiles to minimal machine code. There's hardly any need for an intrinsic.
>
> @rgiulietti In local benchmarks, the compact version of `long_double` is slower than what was in the PR originally, which in turn is slower than the "lazy trailing zeros" version in my previous comment.
> 
> Did you arrive at that compact form through benchmarking?  If so, great - my benchmarks might be bad or I might have conflicting results because I'm on Windows.  If not, I'll suggest that faster forms of this method may exist, which may be worth investigating... eventually.

I added a benchmarks file (we may or may not keep it in the final PR) that we can discuss during the finalization of the PR on openjdk/jdk/. In any case, feel free to take a look on the test.

I followed these [instructions](https://openjdk.org/groups/build/doc/testing.html) for more info. 

The following are quick measurements on an Apple M1 Max chip/macOS 13.2.1 (22D68) -- quick meaning that if we want to keep them, we should run them with 3 forks for 15wi/15i at least.


sh make/devkit/createJMHBundle.sh

bash configure --with-boot-jdk="<.....>/prebuilt/jdk-19.jdk/Contents/Home/" --with-jmh=<.....>/jdk/make/devkit/../../build/jmh/jars/ -disable-warnings-as-errors

make test TEST="micro:org.openjdk.bench.jdk.preview.patterns.Exactness" MICRO="OPTIONS=-p "pollute=true";VM_OPTIONS=--enable-native-access=ALL-UNNAMED;RESULTS_FORMAT=json" CONF=rel

Exactness.test_float_int_based_on_compare             avgt    5  22001.714 ±  21.124  ms/op
Exactness.test_float_int_based_on_filtering           avgt    5  21459.505 ± 159.797  ms/op
Exactness.test_int_float_based_on_filtering           avgt    5   1464.611 ±   5.375  ms/op
Exactness.test_int_float_based_on_leading_trailing    avgt    5   2741.839 ±  10.300  ms/op
Exactness.test_long_double_based_on_filtering         avgt    5   1379.058 ±   4.329  ms/op
Exactness.test_long_double_based_on_leading_trailing  avgt    5   2439.624 ±   4.366  ms/op
Exactness.test_long_float_based_on_filtering          avgt    5   1491.983 ±   8.019  ms/op
Exactness.test_long_float_based_on_leading_trailing   avgt    5   2736.461 ±   9.508  ms/op


Interesting that both float_int are the same and I observe that the filtering ones (or compact) are better than all the analytical (leading_trailing).

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PR: https://git.openjdk.org/amber/pull/91