[lworld] Move null check from method entry into i2c adapter

[Roland Westrelin]

> http://cr.openjdk.java.net/~thartmann/valhalla/lworld/adapter_null_check/

That was fast!

How is the change in sharedRuntime.cpp related to the null check change?

We could still have a null literal in the code so checks for non null
arguments and an unconditional deoptimization is required.

Another related change to move null checks out of the common path would
be to null check return values in the callee rather than the caller and
then deoptimize the caller if it is compiled. That would require a
runtime check in the interpreter but in new code we would statically
know that a value being returned is not null and so would have no check
(unless the value returned is a null literal).

Roland.