RFR(XS): 8141624: Limit calculation of pre loop during super word optimization is wrong

[Volker Simonis]

Hi,

can I please have a second review and a sponsor for this fix
contributed by gunter.haug at sap.com:

http://cr.openjdk.java.net/~simonis/webrevs/2015/8141624/
https://bugs.openjdk.java.net/browse/JDK-8141624

The variable "MemNode* best_align_to_mem_ref" is hidden by a second
declaration of a variable with the same name in an inner block of the
function "SuperWord::find_adjacent_refs()". This leads to unaligned
accesses in generated code. While many platforms handle these
correctly (slower, though), Itanium and potentially other platforms
which don't allow unaligned access will crash.

Thank you and best regards,
Volker