Request for reviews (M): 7079329: Adjust allocation prefetching for T4

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/7079329/webrev

7079329: Adjust allocation prefetching for T4

L2 cache line size is 32 bytes on T4 instead of 64 bytes on T series before. As 
result BIS instruction prefetches only 32 bytes. Jbb2005 runs show that 
prefetching 64 bytes is still better on T4 so 2 BIS instructions should be issued.

BIS can't be use for general prefetching since it may fault. New 
PrefetchAllocation node was added for allocation prefetching.

Changed prefetchAlloc_bis parameter from memory to regP.

Use AllocatePrefetchInstr on Sparc to allow specify what instruction to use for 
allocation prefetching (0: prefetch write, 1: BIS).

Added new instructions on Sparc cacheLineAdrX to reduce number of instructions 
generated for finding next cache line address.

Added new flag AllocateInstPrefetchLines to specify number of lines to prefetch 
for instance allocation.

L1_data_cache_line_size() renamed to prefetch_data_size().