for review (M): 6812831 factor general subclass check (for 6655638)

[John Rose]

On Mar 5, 2009, at 9:06 PM, John Rose wrote:

> ... 2. Compare against wrong register in sparc stub generator  
> (stubGenerator_sparc.cpp at cmp(super_klass, sc_offset))...
>
> Number 2 would make System.arraycopy wrongly throw a CCE if the  
> target array element type is a secondary supertype and is *not*  
> already cached on the element subtypes.  I think I'll have to break  
> this one out as a separate fix, so it can be backported.

FTR, #2 is just a failed optimization in a corner case.  No CCE  
thrown, no need to backport.  When the fast loop gets the type test  
wrong, it just backs off to the slow (original) loop.

-- John