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

[Vladimir Kozlov]

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
>>>>>
>>>
>