RFR 8209171 : Simplify Java implementation of Integer/Long.numberOfTrailingZeros() (original) (raw)

Joseph D. Darcy joe.darcy at oracle.com
Thu Aug 9 23:20:43 UTC 2018

Hi Ivan,

On which platforms were the benchmark numbers collected?

Thanks,

-Joe

On 8/9/2018 4:15 PM, Ivan Gerasimov wrote:

Hello!

Integer.numberOfTrailingZeros() and Long.numberOfTrailingZeros() are intrinsified by Hotspot, so the Java implementation of these is not too important. However, they still can be improved by a tiny bit :) Could you please help review the fix? Bug: https://bugs.openjdk.java.net/browse/JDK-8209171 Webrev: http://cr.openjdk.java.net/~igerasim/8209171/00/webrev/ Benchmark for Integer: http://cr.openjdk.java.net/~igerasim/8209171/00/bench/int/MyBenchmark.java Benchmark for Long: http://cr.openjdk.java.net/~igerasim/8209171/00/bench/long/MyBenchmark.java The resulting code is both smaller and faster. It may also help to warm up Integer.numberOfLeadingZeros() quicker. On average, the new Integer.numberOfTrailingZeros() has got +11% to performance for -client and +1% for -server. Long.numberOfTrailingZeros() is faster on 17% for -client and +20% for -server.

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