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

[changpeng fang - Sun Microsystems - Santa Clara United States]

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
>>>>
>>