On Fri, 14 May 2021 07:41:19 GMT, Richard Startin <github.com+16439049+richardstar...@openjdk.org> wrote:
>> Great analysis on C2, richard. >> >> maybe (x ^ 0x80) &0xFF would help C2 to eliminate bound checks... > > I don't know Laurent, I find the handling of signed order over-complicated. > Subtracting `Integer.MIN_VALUE` is really cheap... I made a JMH test on jdk16 to test count4 (xor) performance: https://github.com/bourgesl/nearly-optimal-mergesort-code/tree/master/sort-bench/results/count_xor Benchmark (size) Mode Cnt Score Error Units ArrayXorBenchmark.arrayAndOriginal 1000000 avgt 20 684561,951 ± 2177,120 ns/op ArrayXorBenchmark.arrayXorOriginal 1000000 avgt 20 777255,465 ± 1815,136 ns/op ArrayXorBenchmark.arrayXor_Masked 1000000 avgt 20 814163,377 ± 2665,436 ns/op ArrayXorBenchmark.arrayXor_Unsafe 1000000 avgt 20 707273,922 ± 2994,380 ns/op Masked xor does not get optimized by c2 too. Using Unsafe is better, see: https://github.com/bourgesl/nearly-optimal-mergesort-code/blob/master/sort-bench/src/main/java/edu/sorting/bench/ArrayXorBenchmark.java If you want, I could make another radixsort() using on or off heap count buffers and Unsafe, as I did in Marlin to avoid bound checks... ------------- PR: https://git.openjdk.java.net/jdk/pull/3938
