[9] RFR (XS): 8155635: C2: opaque unsafe access triggers an assert

[Vladimir Ivanov]

Thanks, Vladimir.

> Looks good. What actual alias type in such case?

Both adr_type & alias_type are:

    java/lang/Object+12 * [narrow]

And LibraryCallKit::classify_unsafe_addr() returns Type::OopPtr for it.

Best regards,
Vladimir Ivanov
>
> Thanks,
> Vladimir
>
> On 5/5/16 11:48 AM, Vladimir Ivanov wrote:
>> http://cr.openjdk.java.net/~vlivanov/8155781/webrev.00/
>> https://bugs.openjdk.java.net/browse/JDK-8155781
>>
>> The following code hits an assert in
>> LibraryCallKit::inline_unsafe_access() during compilation of the
>> following code:
>>
>>      int test(Object o) {
>>          return UNSAFE.getInt(o, F_OFFSET);
>>      }
>>
>> It baffles the compiler since such shape can be used to access both
>> on-heap and off-heap memory (due to double-register addressing mode).
>>
>> The proposed fix is to convert the asserts into guards which revert to
>> native calls in such cases.
>>
>> Testing: JPRT, RBT (hs-tier0-comp).
>>
>> Thanks!
>>
>> Best regards,
>> Vladimir Ivanov