Request for reviews (M): 7081933: Use zeroing elimination optimization for large array

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/7081933/webrev

7081933: Use zeroing elimination optimization for large array

Currently when a new array does not fit into TLAB (big array 
(FastAllocateSizeLimit) or most common case when no space left in TLAB) C2 calls 
runtime which does allocation and zeroing. But zeroing is not needed if 
allocation is followed by arraycopy which initialize it (ReduceBulkZeroing 
optimization).

Add a new runtime call _new_array_nozero_Java for such case and use it only for 
type arrays since obj arrays have to be initialized if deoptimization happened 
on the return from RT to compiled code.

These changes does not affect refworkload scores (including jbb2005). But
crypto.aes (jvm2008) score improved around 10% on sparc. I don't see improvement 
on x86, may by because it has different crypto code.

Added small fix to prefetch code in sparc arraycopy stub.

Thanks,
Vladimir