RFR: Make Zero build and run with JDK8

[Christian Thalinger]

On Oct 16, 2012, at 8:01 AM, Roman Kennke <rkennke at redhat.com> wrote:

> 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/

It seems this webrev contains the old changes.

-- Chris

> 
> Is this ok to commit now?
> 
> Roman
> 
>