Request for reviews (M): 6873116: Modify reexecute implementation to use pcDesc to record the reexecute bit

[Tom Rodriguez]

The only use of the objects() method is in deopt so it seems pretty  
straightforwards but it doesn't have to happen now.  However you want  
to handle it is fine.

tom

On Aug 19, 2009, at 3:22 PM, Vladimir Kozlov wrote:

> Currently I am not sure that it is the only place where we need  
> object values.
> This is why I don't want to rush with this change.
>
> Vladimir
>
> changpeng fang - Sun Microsystems - Santa Clara United States wrote:
>> On 08/19/09 15:09, Vladimir Kozlov wrote:
>>> No. What Tom talks about is to do it only in
>>> Deoptimization::fetch_unroll_info_helper().
>>> In other cases we will generate just empty ObjectValue(id).
>>>
>> Yes, I saw that only use:
>> GrowableArray<ScopeValue*>* objects = chunk->at(0)->scope()- 
>> >objects();
>> Can we do it in this way:
>> GrowableArray<ScopeValue*>* objects = chunk->at(0)->scope()- 
>> >decode_object_values();
>> i.e. we only decode the object when necessary, and don't do it in  
>> the constructor?
>> Maybe we need to remember the offset.
>> Thanks,
>> Changpeng
>>> Vladimir
>>>
>>> changpeng fang - Sun Microsystems - Santa Clara United States wrote:
>>>>
>>>> Is this the approach to make it lazy? Thanks. -- Changpeng
>>>>
>>>>
>>>> diff -r d0acbc302e14 src/share/vm/code/scopeDesc.cpp
>>>> --- a/src/share/vm/code/scopeDesc.cpp   Mon Aug 17 14:45:02 2009  
>>>> -0700
>>>> +++ b/src/share/vm/code/scopeDesc.cpp   Wed Aug 19 14:49:27 2009  
>>>> -0700
>>>> @@ -90,16 +90,21 @@ GrowableArray<ScopeValue*>* ScopeDesc::d
>>>>
>>>> GrowableArray<ScopeValue*>* ScopeDesc::decode_object_values(int  
>>>> decode_offset) {
>>>>  if (decode_offset == DebugInformationRecorder::serialized_null)  
>>>> return NULL;
>>>> -  GrowableArray<ScopeValue*>* result = new  
>>>> GrowableArray<ScopeValue*>();
>>>> -  DebugInfoReadStream* stream = new DebugInfoReadStream(_code,  
>>>> decode_offset, result);
>>>> -  int length = stream->read_int();
>>>> -  for (int index = 0; index < length; index++) {
>>>> -    // Objects values are pushed to 'result' array during read  
>>>> so that
>>>> -    // object's fields could reference it (OBJECT_ID_CODE).
>>>> -    (void)ScopeValue::read_from(stream);
>>>> +#ifdef COMPILER2
>>>> +  if (DoEscapeAnalysis && EliminateAllocations) {
>>>> +    GrowableArray<ScopeValue*>* result = new  
>>>> GrowableArray<ScopeValue*>();
>>>> +    DebugInfoReadStream* stream = new DebugInfoReadStream(_code,  
>>>> decode_offset, result);
>>>> +    int length = stream->read_int();
>>>> +    for (int index = 0; index < length; index++) {
>>>> +      // Objects values are pushed to 'result' array during read  
>>>> so that
>>>> +      // object's fields could reference it (OBJECT_ID_CODE).
>>>> +      (void)ScopeValue::read_from(stream);
>>>> +    }
>>>> +    assert(result->length() == length, "inconsistent debug  
>>>> information");
>>>> +    return result;
>>>>  }
>>>> -  assert(result->length() == length, "inconsistent debug  
>>>> information");
>>>> -  return result;
>>>> +#endif
>>>> +  return NULL;
>>>> }
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>> Tom Rodriguez wrote:
>>>>>> By the way, does anyone know why the objects for EA are decoded  
>>>>>> eagerly instead of being decoded lazily like all the other  
>>>>>> debug info?  That seems like unneeded overhead for most uses of  
>>>>>> ScopeDesc for stack walking.
>>>>>
>>>>> Do you mean the call to decode_object_values()?
>>>>> It is done only for top frame.
>>>>> But you are right that we may need to call it only when we
>>>>> need to decode narrow oop. I will look on it.
>>>>>
>>>>> Vladimir
>>>>>
>>>>>>
>>>>>> tom
>>>>>>
>>>>