On Wed, 16 Feb 2022 12:30:27 GMT, Jatin Bhateja <jbhat...@openjdk.org> wrote:
>> Summary of changes: >> - Intrinsify Math.round(float) and Math.round(double) APIs. >> - Extend auto-vectorizer to infer vector operations on encountering scalar >> IR nodes for above intrinsics. >> - Test creation using new IR testing framework. >> >> Following are the performance number of a JMH micro included with the patch >> >> Test System: Intel(R) Xeon(R) Platinum 8380 CPU @ 2.30GHz (Icelake Server) >> >> >> Benchmark | TESTSIZE | Baseline AVX3 (ops/ms) | Withopt AVX3 (ops/ms) | Gain >> ratio | Baseline AVX2 (ops/ms) | Withopt AVX2 (ops/ms) | Gain ratio >> -- | -- | -- | -- | -- | -- | -- | -- >> FpRoundingBenchmark.test_round_double | 1024.00 | 584.99 | 1870.70 | 3.20 | >> 510.35 | 548.60 | 1.07 >> FpRoundingBenchmark.test_round_double | 2048.00 | 257.17 | 965.33 | 3.75 | >> 293.60 | 273.15 | 0.93 >> FpRoundingBenchmark.test_round_float | 1024.00 | 825.69 | 3592.54 | 4.35 | >> 825.32 | 1836.42 | 2.23 >> FpRoundingBenchmark.test_round_float | 2048.00 | 388.55 | 1895.77 | 4.88 | >> 412.31 | 945.82 | 2.29 >> >> >> Kindly review and share your feedback. >> >> Best Regards, >> Jatin > > Jatin Bhateja has updated the pull request with a new target base due to a > merge or a rebase. The pull request now contains seven commits: > > - 8279508: Adding few descriptive comments. > - Merge branch 'master' of http://github.com/openjdk/jdk into JDK-8279508 > - 8279508: Replacing by efficient instruction sequence based on MXCSR.RC > mode. > - 8279508: Adding vectorized algorithms to match the semantics of rounding > operations. > - Merge branch 'master' of http://github.com/openjdk/jdk into JDK-8279508 > - 8279508: Adding a test for scalar intrinsification. > - 8279508: Auto-vectorize Math.round API > _Mailing list message from [Joseph D. Darcy](mailto:joe.da...@oracle.com) on > [hotspot-dev](mailto:hotspot-...@mail.openjdk.java.net):_ > > On 2/12/2022 6:55 PM, Jatin Bhateja wrote: > > > On Fri, 21 Jan 2022 00:49:04 GMT, Sandhya Viswanathan <sviswanathan at > > openjdk.org> wrote: > > > The JVM currently initializes the x86 mxcsr to round to nearest even, see > > > below in stubGenerator_x86_64.cpp: // Round to nearest (even), 64-bit > > > mode, exceptions masked StubRoutines::x86::_mxcsr_std = 0x1F80; The above > > > works for Math.rint which is specified to be round to nearest even. > > > Please see: > > > https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html > > > : section 4.8.4 > > > The rounding mode needed for Math.round is round to positive infinity > > > which needs a different x86 mxcsr initialization(0x5F80). > > > Hi @sviswa7 , > > > As per JLS 17 section 15.4 Java follows round to nearest rounding policy > > > for all floating point operations except conversion to integer and > > > remainder where it uses round toward zero. > > That is a true background condition, but I will note that the Math.round > method does independently define the semantics of its operation and rounding > behavior, which has changed (slightly) over the lifetime of the platform. > > -Joe Hi @jddarcy , Thanks for your comments, patch has been updated to follow the prescribed semantics of Math.round API. ------------- PR: https://git.openjdk.java.net/jdk/pull/7094