RFR: 8214205: PPC64: Add instructions for counting trailing zeros

Doerr, Martin martin.doerr at sap.com
Thu Nov 22 10:20:05 UTC 2018

Hi Michihiro,

this change needs to get reviewed on hotspot-compiler-dev (added).
Also added missing "RFR".

The change looks good. I only have very minor requests:

"_Ex" should be removed from the new instruct names. They aren't expand rules.

Please also update the copyright year in the header of the ad file.

Maybe Gustavo can test it, write a 2nd review and push it when it's good.

Best regards,


From: Michihiro Horie <HORIE at jp.ibm.com>
Sent: Donnerstag, 22. November 2018 06:40
To: ppc-aix-port-dev at openjdk.java.net
Cc: Gustavo Romero <gromero at linux.vnet.ibm.com>; Doerr, Martin <martin.doerr at sap.com>
Subject: RFR: 8214205: PPC64: Add instructions for counting trailing zeros

Dear all,

Would you please review the following change that enables POWER9's instructions for counting trailing zeros?

Bug: https://bugs.openjdk.java.net/browse/JDK-8214205
Webrev: http://cr.openjdk.java.net/~mhorie/8214205/webrev.00/

Simple micro benchmark attached showed improvements by around 30%.
(See attached file: CNTTZTest.java)

Currently, Gustavo at IBM can test POWER9 specific changes. (Thanks Gustavo!)

Best regards,
IBM Research - Tokyo
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