Review request (S): 6711100: 64bit fastdebug server vm crashes with assert(_base == Int,"Not an Int")

[Chuck Rasbold]

http://webrev.invokedynamic.info/rasbold/6711100/index.html

6711100: 64bit fastdebug server vm crashes with assert(_base == Int,"Not 
an Int")
Summary: insert CastII nodes to narrow type of load_array_length() node
Reviewed-by:

Another variant of the bug caused by array_addressing() not stopping
the parse when there is enough info to know that the index is
out-of-bounds.  In this case, load_array_length() get the length from
the AllocateArrayNode for the array length, but doesn't narrow the
type.

The fix:

- add assertion in array_addressing() to catch problems of this nature
at a single point of failure

- add the function AllocateArrayNode::make_ideal_length(), which peeks
into the node for the length, and adds a CastII to narrow the type, if
appropriate

- use make_ideal_length() in all places where a CastII could narrow
the type of input to the allocation, including:
GraphKit::load_array_length(), GraphKit::new_array(), and the newly
added LoadRangeNode::Ideal()

- change LoadRangeNode::Identity() to only return the length argument
of a found AllocateArrayNode if a CastII is not needed