RFR(XS): 8028764: dtrace/hotspot_jni/ALL/ALL001 crashes the vm on Solaris-amd64, SIGSEGV in MarkSweep::follow_stack()+0x8a

[Roland Westrelin]

> C1 generated code encodes a compressed oop into to temp register before it stores it. In case of patching, a GC may happen and the compressed oop may be incorrect when it is stored to memory. 
> 
> http://cr.openjdk.java.net/~roland/8028764/webrev.00/

I should have acknowledged that all the credit for this bug (investigation and fix) goes to Mikael Gerdin and Erik Helin from the GC team. Thanks to them!

Roland.