RFR (S) JDK-8223017: [lworld] checkcast/instance broken for LW2 arrays

[David Simms]

Updated webrev: http://cr.openjdk.java.net/~dsimms/valhalla/8223017/

Remove "QDescBit" constant pool tag encoding for arrays of Q, it wasn't 
required. Since I was there I removed macro and renamed to 
"JVM_CONSTANT_QDescBit" in-line with the rest of the code...sorry for 
the extra noise in the patch.

Cheers
/David Simms


On 30/04/19 3:46 PM, David Simms wrote:
>
> Nice spotting, I didn't differentiate the "checkcast" behavior for 
> "Q-type descriptors" and "Array Q-type descriptors".
>
> Since we are heading into a local holiday (tonight and tomorrow, 
> bonfire night), I'll leave a note on my thinking here if I don't get 
> to it until Thursday...
>
>      * I probably need to || in another bit for arrays of q-type in the
>        constant pool tag for the difference in behavior. Thinking of
>        using "JVM_CONSTANT_Unicode" since it is unused (further mess,
>        but there are not separate bits left)
>      * anewarray and multianewarray needs something to tell them it's a
>        q-type array, but for the interpreter at least we jump into the
>        VM...so I wonder if we need the constant tag encoding at all
>
> Will look a little further into this...
>
> Cheers
>
> /D
>
>
> On 30/04/19 12:27 PM, Tobias Hartmann wrote:
>> Hi Mr. Simms,
>>
>> I'm seeing the following inconsistent behavior:
>>
>>    MyValue1?[] va1 = (MyValue1?[])null;  // does not throw NPE
>>    MyValue1?[] va2 = null;               // does not throw NPE
>>    MyValue1[]  va3 = null;               // does not throw NPE
>>    MyValue1[]  va4 = (MyValue1[])null;   // throws NPE
>>
>> Thanks,
>> Tobias
>>
>> On 29.04.19 12:01, David Simms wrote:
>>> Here's a fix for the missing super type relationship for null-free 
>>> arrays, i.e. "[QFoo;" <:
>>> "[LFoo;"...once LW2 array support went in, it accidentally skipped 
>>> it's null-allow type and went
>>> straight to Object[]...added a few more test cases.
>>>
>>> Webrev:
>>>
>>> http://cr.openjdk.java.net/~dsimms/valhalla/8223017/
>>>
>>> Bug:
>>>
>>> https://bugs.openjdk.java.net/browse/JDK-8223017
>>>
>