preliminary review (L): 6939861: JVM should handle more conversion operations

[John Rose]

This is the JVM infrastructure for pushing a stack frame *during* a method handle call, so that some sort of intermediate fixup operation can be done before completing the call.

The requirement is that a recognizable stack frame be pushed during the intermediate fixup operation, so that if there is an exception, or a GC, or some other stack walk, the stack will be parsed properly.  Crucially, the pending arguments must be recognized as managed pointers.

This is a preliminary review, because it shows just the new stack frame type, rather than the use cases (which are forthcoming).

6939861: JVM should handle more conversion operations
http://cr.openjdk.java.net/~jrose/6939861/webrev.00/

-- John