review (XS) for 6982533: Crash in ~StubRoutines::jbyte_fill with AggressiveOpts enabled

[Tom Rodriguez]

http://cr.openjdk.java.net/~never/6982533

6982533: Crash in  ~StubRoutines::jbyte_fill with AggressiveOpts enabled
Reviewed-by:

The logic for matching a byte fill is missing a check for the use of
the index.  It normally happens as part of the check for a shift
expression but since a byte array doesn't have a shift the check is
missed.  The fix is to make the index check explicit.  The reason it
didn't always crash was because of differences in heap size caused by
ergonomics.  With a 16m heap it crashes on any machine.  Tested with
failing test case.

src/share/vm/opto/loopTransform.cpp