RFR: Make Zero build and run with JDK8

[Roman Kennke]

Hi Christian,

> >>>> In the recent weeks I worked on the Zero interpreter, to get it to build
> >>>> and run with JDK8, and in particular with the latest changes that came
> >>>> from mlvm (meth-lazy). The following webrev applies to hsx/hotspot-main:
> >>>> 
> >>>> http://cr.openjdk.java.net/~rkennke/zerojdk8/webrev.00/
> >> 
> >> src/share/vm/asm/codeBuffer.cpp:
> >> 
> >> -  if (dest->blob() == NULL) {
> >> +  if (dest->blob() == NULL && dest_filled != 0x0) {
> >> 
> >> Do we really need this when you have this:
> > 
> > The above is needed, because the loop above it that initializes
> > dest_filled is never executed. However, I will change the test to
> > dest_filled != NULL :-)
> > 
> >> static void pd_fill_to_bytes(void* to, size_t count, jubyte value) {
> >> 
> >> -  memset(to, value, count);
> >> +  if ( count > 0 ) memset(to, value, count);
> >> 
> >> }
> > 
> > Turns out that this is 1. not related to the other change above and 2.
> > not needed. I'll remove it.
> > 
> >> src/share/vm/interpreter/interpreter.cpp:
> >> 
> >> -  assert(_entry_table[kind] == _entry_table[abstract], "previous value must be AME entry");
> >> +  assert(_entry_table[kind] == NULL || _entry_table[kind] == _entry_table[abstract], "previous value must be AME entry or NULL");
> >> 
> >> Why did you need that change?
> > 
> > Apparently, before the whole table was initialized, and the methodhandle
> > related entries left as abstract. Now the methodhandle entries are
> > simply left to NULL. I suppose we could change the assert to 
> > 
> > assert(_entry_table[kind] == NULL, "previous value must be NULL");
> > 
> > Alternatively, we could fix the code that puts the other entries to also
> > set the methodhandle entries to AME and go back to the original assert.
> > What do you think?
> 
> TemplateInterpreterGenerator::generate_all sets all MH entries to AME:
> 
>   // method handle entry kinds are generated later in MethodHandlesAdapterGenerator::generate:                                                                  
>   for (int i = Interpreter::method_handle_invoke_FIRST; i <= Interpreter::method_handle_invoke_LAST; i++) {                                                      
>     Interpreter::MethodKind kind = (Interpreter::MethodKind) i;                                                                                                  
>     Interpreter::_entry_table[kind] = Interpreter::_entry_table[Interpreter::abstract];                                                                          
>   }                                                                                                                                                              
> 
> You need similar code in Zero.

Alright, I extracted this piece of code into a separate protected method
void AbstractInterpreterGenerator::initializeMethodHandleEntries() and
call it both from templateInterpreter and cppInterpreter to initialize
the method handle entries to AME.

This new webrev also reverts this:

>> static void pd_fill_to_bytes(void* to, size_t count, jubyte value) {
> >> 
> >> -  memset(to, value, count);
> >> +  if ( count > 0 ) memset(to, value, count);
> >> 
> >> }
> 

.. and changes the 0x0 to NULL here:


>> src/share/vm/asm/codeBuffer.cpp:
> >> 
> >> -  if (dest->blob() == NULL) {
> >> +  if (dest->blob() == NULL && dest_filled != 0x0) {
> >> 
> 

I tried JRuby a little more and verified that it's actually using +indy,
and it works all well.

http://cr.openjdk.java.net/~rkennke/zerojdk8/webrev.01/

Is this ok to commit now?

Roman