[lworld] RFR(M): Multiple compiler fixes and refactoring

[Roland Westrelin]

>> callGenerator.cpp line 921. Shouldn't we know statically if arg is null
>> (a null litteral) because we filter nulls early?
>
> What do you mean by "filter nulls early"? The check at method entry? In this case we don't have a
> null check at method entry because we are compiling a lambda form and the arg type is
> java.lang.Object. We then need to emit a null check when inlining the linkTo call and casting the
> arg to a value type.

Right.

>> Same question for
>> parse1.cpp line 617.
>
> This is the null check for value type arguments at method entry.

That one can (and should) be restricted to the root of the compilation
(depth() == 1).

Except for that, looks good.

Roland.