[14] RFR(XS): 8223769: Assert triggers with -XX:+StressReflectiveCode

[Christian Hagedorn]

Hi

Please review the following patch:
https://bugs.openjdk.java.net/browse/JDK-8223769
http://cr.openjdk.java.net/~thartmann/8223769/webrev.00/

The assertion is too strong when enabling the StressReflectiveCode flag. 
  While the type system knows the size of an array is constant, the 
ArrayCopyNode::Length input node itself is not. The layout helper is not 
used with StressReflectiveCode and therefore a load node is inserted as 
part of the entire input to the length node 
(http://hg.openjdk.java.net/jdk/jdk/file/3307a6ded22d/src/hotspot/share/opto/graphKit.cpp#l3455). 
This load node is not optimized away with StressReflectiveCode 
(http://hg.openjdk.java.net/jdk/jdk/file/3307a6ded22d/src/hotspot/share/opto/memnode.cpp#l1853).

Thanks!

Best regards,
Christian