[8u] RFA for JDK-8148175: C1: G1 barriers don't preserve FP registers

[Muthusamy Chinnathambi]

Hi,

May I get the approval of backport of JDK-8148175: C1: G1 barriers don't preserve FP registers to jdk8u.

Jdk9 bug: https://bugs.openjdk.java.net/browse/JDK-8148175 
Jdk9 review thread: http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2016-March/022086.html 
Jdk8 review thread: http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2017-October/027221.html 
Webrev link: http://cr.openjdk.java.net/~mchinnathamb/8148175/webrev.00/ 

Regards,
Muthusamy C