RFR: 8149837: String.intern creates more work than necessary for G1

[Derek White]

This small change only does a STAB read barrier if we really read a 
string from the string intern table.

This is a small optimization, and the old code may contribute to the 
malloc failures in JDK-8134992 
<https://bugs.openjdk.java.net/browse/JDK-8134992> 
"vm/gc/compact/Compact_InternedStrings_Strings failed due to a malloc() 
failure"

RFE: JDK-8149837 <https://bugs.openjdk.java.net/browse/JDK-8149837>
Webrev: http://cr.openjdk.java.net/~drwhite/8149837/webrev.01/

Tested: jprt

Thanks!
  - Derek
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/hotspot-gc-dev/attachments/20160215/dac2fa61/attachment.htm>