Flattened value type field support for C2

Tobias Hartmann tobias.hartmann at oracle.com
Wed Nov 16 07:57:56 UTC 2016


Hi Zoltan,

On 15.11.2016 17:36, Zoltán Majó wrote:
> Hi Tobias,
> 
> 
> On 11/11/2016 12:00 PM, Tobias Hartmann wrote:
>> Hi,
>>
>> here's my implementation of (flattened) value type field support for C2:
>> http://cr.openjdk.java.net/~thartmann/valhalla/vt_prototype/webrev.03/
>>
>> The patch contains the following changes:
>> - Support for flattened value type fields in regular objects and value types
>>    - field list in ciInstanceKlass now contains flattened value type fields (recursively)
>>    - fixed instanceOopDesc::contains_field_offset() to account for different alignment of value type fields
>>    - fixed alias analysis to support value type fields
>>    - fixed deoptimization to correctly reassign flattened value type fields
>> - Improved ValueKlass::first_field_offset() to not iterate over all fields but compute the offset
>> - Improved ValueTypeNode::make_scalar_in_safepoints() and added support for value type fields
>> - Added new tests, increased coverage of existing tests and fixed test bench to support product builds
>> - Lots of refactoring, added more comments and more asserts
>>
>> I also tried to make it more clear/explicit in the code that ciValueKlass translates between the following field indexes:
>> 1) Value type factory parameter index: The index of the value type factory parameter that corresponds to a field index 2) in the valueKlass. The value of that field can be obtained by the value input edge of the ValueTypeNode in C2 IR with the same index.
>> 2) Field index in the valueKlass.
> 
> your change looks good to me -- thank you for the clarifications off-line!

Thanks for having a look!

> I've spotted a small issue with ValueTypeTestBench.java at line 547:
> 
> 547 "-XX:CompileCommand=inline,java.lang.Object::<init>",
> 
> You might have left that in by accident.

Yes, that's a leftover from some testing I did. I will remove the line before pushing.

Thanks,
Tobias

> Thank you!
> 
> Best regards,
> 
> 
> Zoltan
> 
> 
>> I'll write up a more detailed documentation in the next days.
>>
>> Please have a look at the code and let me know if you spot any problems.
>>
>> Thanks,
>> Tobias
> 


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