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

[Changpeng Fang]

I am doing this now, and will send out the webrev soon.

Thanks,

Changpeng

On 08/19/09 15:57, Tom Rodriguez wrote:
> 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
>>>>>>>
>>>>>
>