RFR(S): 8187964: [s390][ppc]: Intrinsify Math.multiplyHigh(long, long)

Doerr, Martin martin.doerr at sap.com
Fri Oct 6 13:03:46 UTC 2017

Hi Lutz,

looks good. If you like, you can get rid of one or both tmp registers if you want to save them.

Did you also check if it improves long division which also uses multiply high nodes?

I can sponsor this change.

Best regards,

From: hotspot-compiler-dev [mailto:hotspot-compiler-dev-bounces at openjdk.java.net] On Behalf Of Schmidt, Lutz
Sent: Freitag, 6. Oktober 2017 11:10
To: hotspot-compiler-dev at openjdk.java.net
Subject: RFR(S): 8187964: [s390][ppc]: Intrinsify Math.multiplyHigh(long, long)

Dear all,

I would like to request reviews for this s390-only enhancement (ppc support was already implemented for other purpose):

Bug:    https://bugs.openjdk.java.net/browse/JDK-8187964
Webrev: http://cr.openjdk.java.net/~lucy/webrevs/8187964.00/index.html

This change provides platform-specific implementations for the Math.multiplyHigh method, exploiting 64bit x 64bit => 128bit multiply instructions available on these platforms. Microbenchmark performance shows improvement of 4x to 5x for [s390] and 10x to 15x for [ppc].

Thank you!

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