RFR: 8131062: aarch64: add support for GHASH acceleration

[Edward Nevill]

Hi,

http://cr.openjdk.java.net/~enevill/8131062/webrev.0/

adds support for GHASH acceleration on aarch64 using the 128 bit pmull and pmull2 instructions.

This patch was contributed by alexander.alexeev at caviumnetworks.com

Note that the 128 pmull instructions are not supported on all aarch64. The patch uses the HWCAP_PMULL bit from getauxv() to determine whether the 128 bit pmull is supported.

I have tested this with jtreg / hotspot.

Without patch: Test results: passed: 876; failed: 3; error: 9
With patch: Test results: passed: 876; failed: 3; error: 9

In both cases the set of failing/error tests is identical.

I have done some performance testing using TestAESMain from the jtreg/hotspot test suite. Here are the results I get:-

java -XX:-UseGHASHIntrinsics -DcheckOutput=true -Dmode=GCM TestAESMain

encode time = 66945.63635, decode time = 34085.08754

java -XX:+UseGHASHIntrinsics -DcheckOutput=true -Dmode=GCM TestAESMain

encode time = 43469.38244, decode time = 17783.6603

This is an improvement of 54% and 92% respectively.

Alexander has done some benchmarking to measure the raw performance improvement of GHASH on its own using the following benchmark.

http://cr.openjdk.java.net/~enevill/8131062/GHash.java

Here are the results he gets:-

-XX:-UseGHASHIntrinsics.

Benchmark             Mode  Cnt    Score   Error  Units
GHash.calculateGHash  avgt    5  118.688 ? 0.009  us/op

-XX:+UseGHASHIntrinsics
Benchmark             Mode  Cnt   Score   Error  Units
GHash.calculateGHash  avgt    5  21.164 ? 1.763  us/op

This represents a 5.6X speed increase on the raw GHASH performance.

Thanks your your review,

Ed.