8211908: PPC64: Enable SuperWordLoopUnrollAnalysis by default

[Doerr, Martin]

Hi Michihiro,

looks good. Thanks for doing some performance measurements.

The change itself could be considered as trivial, but the impact may be significant, so I'd appreciate a 2nd review.

We already tested this flag in our nightly tests for a few weeks and didn't see any issues. It's also enabled on other platforms which use vector instructions so I think we should use it on PPC, too.

Best regards,
Martin


From: Michihiro Horie <HORIE at jp.ibm.com>
Sent: Dienstag, 9. Oktober 2018 09:11
To: hotspot compiler <hotspot-compiler-dev at openjdk.java.net>; ppc-aix-port-dev at openjdk.java.net
Cc: Doerr, Martin <martin.doerr at sap.com>; Lindenmaier, Goetz <goetz.lindenmaier at sap.com>; Gustavo Romero <gromero at linux.vnet.ibm.com>
Subject: RFR: 8211908: PPC64: Enable SuperWordLoopUnrollAnalysis by default


Dear all,

Would you please review this simple change?
Bug: https://bugs.openjdk.java.net/browse/JDK-8211908
Webrev: http://cr.openjdk.java.net/~mhorie/8211908/webrev.00

Since PPC64 supports SLP with VSX, we can have the benefit from enabled SuperWordLoopUnrollAnalysis on PPC64.

In the attached micro benchmarks, performance improved by 1.7x at maximum. In SPECjvm2008, the score improved by a couple of % in xml.validation and scimark.lu.large

(See attached file: microbench_slp.tar.gz)

Best regards,
--
Michihiro,
IBM Research - Tokyo
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