[aarch64-port-dev ] RFR: 8169697: aarch64: vectorized MLA instruction not generated for some test cases

[Ningsheng Jian]

Hi,

NEON vector MLA instructions can not be generated in some simple
multiply-add cases.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8169697

The following webrev contributed by Yang Zhang (yang.zhang at linaro.org)
can resolve it.

Webrev:
http://cr.openjdk.java.net/~njian/8169697/webrev.00/

Please help to review it. To minimize impact, this patch only changes
aarch64 specified code. Do you think this is OK for 9? If yes, do we
need a FC Extension Request?

In the mean time, Yang also has a more generic fix for this issue,
which patches share code and could also fix this issue:

http://cr.openjdk.java.net/~njian/8169697/webrev.share/

Which do you think is better?

Both patches tested with fastdebug jtreg.

Thanks,
Ningsheng