RFR 8189230: JDK method:java.lang.Integer.numberOfLeadingZeros(int) can be optimized

Brian Burkhalter brian.burkhalter at oracle.com
Tue Mar 13 23:44:39 UTC 2018

On Mar 13, 2018, at 4:42 PM, Paul Sandoz <paul.sandoz at oracle.com> wrote:

> Given how trivial the changes are it looks ok, but not sure it really matters in practice.

Nor do I.

> Note that it’s possible to selectively disable intrinsics. For future reference, when you want to avoid copying code if you happen to benchmark intrinsics in the future:
>  -XX:+UnlockDiagnosticVMOptions -XX:DisableIntrinsic=_numberOfLeadingZeros_i

Yes, I knew about that.

> But you have to know the intrinsic name, you can find ‘em here:
>  http://hg.openjdk.java.net/jdk/jdk/file/63eceefeb347/src/hotspot/share/classfile/vmSymbols.hpp#l805

This latter is very helpful, thanks.


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