Continuing the work initiated by @luhenry to unroll and then intrinsify polynomial hash loops.
I've rewired the library changes to route via a single `@IntrinsicCandidate` method. To make this work I've harmonized how they are invoked so that there's less special handling and checks in the intrinsic. Mainly do the null-check outside of the intrinsic for `Arrays.hashCode` cases. Having a centralized entry point means it'll be easier to parameterize the factor and start values which are now hard-coded (always 31, and a start value of either one for `Arrays` or zero for `String`). It seems somewhat premature to parameterize this up front. The current implementation is performance neutral on microbenchmarks on all tested platforms (x64, aarch64) when not enabling the intrinsic. We do add a few trivial method calls which increase the call stack depth, so surprises cannot be ruled out on complex workloads. With the most recent fixes the x64 intrinsic results on my workstation look like this: Benchmark (size) Mode Cnt Score Error Units StringHashCode.Algorithm.defaultLatin1 1 avgt 5 2.199 ± 0.017 ns/op StringHashCode.Algorithm.defaultLatin1 10 avgt 5 6.933 ± 0.049 ns/op StringHashCode.Algorithm.defaultLatin1 100 avgt 5 29.935 ± 0.221 ns/op StringHashCode.Algorithm.defaultLatin1 10000 avgt 5 1596.982 ± 7.020 ns/op Baseline: Benchmark (size) Mode Cnt Score Error Units StringHashCode.Algorithm.defaultLatin1 1 avgt 5 2.200 ± 0.013 ns/op StringHashCode.Algorithm.defaultLatin1 10 avgt 5 9.424 ± 0.122 ns/op StringHashCode.Algorithm.defaultLatin1 100 avgt 5 90.541 ± 0.512 ns/op StringHashCode.Algorithm.defaultLatin1 10000 avgt 5 9425.321 ± 67.630 ns/op I.e. no measurable overhead compared to baseline even for `size == 1`. The vectorized code now nominally works for all unsigned cases as well as ints, though more testing would be good. Benchmark for `Arrays.hashCode`: Benchmark (size) Mode Cnt Score Error Units ArraysHashCode.bytes 1 avgt 5 1.884 ± 0.013 ns/op ArraysHashCode.bytes 10 avgt 5 6.955 ± 0.040 ns/op ArraysHashCode.bytes 100 avgt 5 87.218 ± 0.595 ns/op ArraysHashCode.bytes 10000 avgt 5 9419.591 ± 38.308 ns/op ArraysHashCode.chars 1 avgt 5 2.200 ± 0.010 ns/op ArraysHashCode.chars 10 avgt 5 6.935 ± 0.034 ns/op ArraysHashCode.chars 100 avgt 5 30.216 ± 0.134 ns/op ArraysHashCode.chars 10000 avgt 5 1601.629 ± 6.418 ns/op ArraysHashCode.ints 1 avgt 5 2.200 ± 0.007 ns/op ArraysHashCode.ints 10 avgt 5 6.936 ± 0.034 ns/op ArraysHashCode.ints 100 avgt 5 29.412 ± 0.268 ns/op ArraysHashCode.ints 10000 avgt 5 1610.578 ± 7.785 ns/op ArraysHashCode.shorts 1 avgt 5 1.885 ± 0.012 ns/op ArraysHashCode.shorts 10 avgt 5 6.961 ± 0.034 ns/op ArraysHashCode.shorts 100 avgt 5 87.095 ± 0.417 ns/op ArraysHashCode.shorts 10000 avgt 5 9420.617 ± 50.089 ns/op Baseline: Benchmark (size) Mode Cnt Score Error Units ArraysHashCode.bytes 1 avgt 5 3.213 ± 0.207 ns/op ArraysHashCode.bytes 10 avgt 5 8.483 ± 0.040 ns/op ArraysHashCode.bytes 100 avgt 5 90.315 ± 0.655 ns/op ArraysHashCode.bytes 10000 avgt 5 9422.094 ± 62.402 ns/op ArraysHashCode.chars 1 avgt 5 3.040 ± 0.066 ns/op ArraysHashCode.chars 10 avgt 5 8.497 ± 0.074 ns/op ArraysHashCode.chars 100 avgt 5 90.074 ± 0.387 ns/op ArraysHashCode.chars 10000 avgt 5 9420.474 ± 41.619 ns/op ArraysHashCode.ints 1 avgt 5 2.827 ± 0.019 ns/op ArraysHashCode.ints 10 avgt 5 7.727 ± 0.043 ns/op ArraysHashCode.ints 100 avgt 5 89.405 ± 0.593 ns/op ArraysHashCode.ints 10000 avgt 5 9426.539 ± 51.308 ns/op ArraysHashCode.shorts 1 avgt 5 3.071 ± 0.062 ns/op ArraysHashCode.shorts 10 avgt 5 8.168 ± 0.049 ns/op ArraysHashCode.shorts 100 avgt 5 90.399 ± 0.292 ns/op ArraysHashCode.shorts 10000 avgt 5 9420.171 ± 44.474 ns/op As we can see the `Arrays` intrinsics are faster for small inputs, and faster on large inputs for `char` and `int` (the ones currently vectorized). I aim to fix `byte` and `short` cases before integrating, though it might be acceptable to hand that off as follow-up enhancements to not further delay integration of this enhancement. ------------- Commit messages: - ws - Add ArraysHashCode microbenchmarks - Fixed vector loops for int and char arrays - Split up Arrays/HashCode tests - Fixes, optimized short inputs, temporarily disabled vector loop for Arrays.hashCode cases, added and improved tests - typo - Add Arrays.hashCode tests, enable intrinsic by default on x86 - Correct start values for array hashCode methods - Merge branch 'master' into 8282664-polyhash - Fold identical ops; only add coef expansion for Arrays cases - ... and 28 more: https://git.openjdk.org/jdk/compare/303548ba...22fec5f0 Changes: https://git.openjdk.org/jdk/pull/10847/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10847&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8282664 Stats: 1129 lines in 32 files changed: 1071 ins; 32 del; 26 mod Patch: https://git.openjdk.org/jdk/pull/10847.diff Fetch: git fetch https://git.openjdk.org/jdk pull/10847/head:pull/10847 PR: https://git.openjdk.org/jdk/pull/10847
