RFR: Make Zero build and run with JDK8

[Christian Thalinger]

On Oct 17, 2012, at 3:05 PM, Roman Kennke <rkennke at redhat.com> wrote:

> Am Mittwoch, den 17.10.2012, 14:40 -0700 schrieb 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.
> 
> Arg! I did the changes in my hotspot-comp tree then made the webrev in
> my hotspot-main :-) Here's the correct one:
> 
> http://cr.openjdk.java.net/~rkennke/zerojdk8/webrev.02/

That looks better.  The only thing is we don't use camel-case for methods:

+  void initializeMethodHandleEntries();

Could you change it to:

+  void initialize_method_handle_entries();

I would do it myself but I cannot verify that I didn't break Zero.  I really should set up a build environment for Zero...

-- Chris

> 
> Cheers,
> Roman
> 
>