[s390] RFR(XS): 8184267: Restore register from stack uses wrong offset

[Schmidt, Lutz]

Dear community,

may I please request reviews for this little s390-only bug fix? It corrects the offset used to restore a previously saved argument register value. At the same time, the save/restore code is improved by the use of “store multiple” and “load multiple” instructions.

Bug: https://bugs.openjdk.java.net/browse/JDK-8184267
Webrev: http://cr.openjdk.java.net/~lucy/webrevs/8184267.00/

Thank you very much!
Lutz