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

[Tom Rodriguez]

I figured it would look like the other lazy ones, i.e. record the  
offset in the constructor and do the decode in ScopeDesc::objects().

tom

On Aug 19, 2009, at 3:09 PM, 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).
>
> 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
>>>>