[foreign] RFR 8209496: Minimize allocation in NativeInvoker::invokeNormal

[Maurizio Cimadamore]

Hi,
this patch avoids some expensive allocations in the 
NativeInvoker::invokeNormal code path. This code has to perform two tasks:

* given an input array of (Java) object arguments, it has to copy the 
marshalled version of such arguments into a long array

* given a long array contaning return value, it has to extract a Java 
object out of it (or copying the contents in the desired memory location)

To carry out most of these operation, it suffices to operate at a low 
level, by viewing the long arrays managed by the system ABI as a 'heap' 
pointer (see new routine BoundedPointer::fromLongArray). From there, we 
can simply get/set values, using the pointer setter/getters which will 
directly affect the underlying array, with no need to go via a third 
pointer.

Webrev:

http://cr.openjdk.java.net/~mcimadamore/panama/8209496/

P.S.

Given the touched area is quite delicate, some testing on different 
platforms would be appreciated :-)

Cheers
Maurizio