RFR: 8245452: Clean up compressed pointer logic in lcm.cpp

[Nils Eliasson]

+1

Best regards,
Nils

On 2020-06-02 03:40, Vladimir Kozlov wrote:
> Looks good.
>
> Thanks,
> Vladimir
>
> On 5/27/20 6:14 AM, Erik Österlund wrote:
>> Hi,
>>
>> After my change enabling compressed class pointers when compressed 
>> oops is disabled,
>> Vladimir Kozlov pointed out that there is potential for simplifying 
>> some code in lcm.cpp
>> that uses various checks if there is any form of compressed class/oop 
>> pointers with shift 0,
>> as a way of using either the base->get_ptr_type() or 
>> base->bottom_type()->is_ptr() of
>> a base pointer. These tests have always had false positives, where 
>> the base->get_ptr_type()
>> is used when there is no way it could be a compressed pointer with 
>> shift 0.
>>
>> This dance is not really necessary if we just use the 
>> base->get_ptr_type() always, instead of
>> carefully figuring out when we can use the bottom type. Because it 
>> works in both cases.
>>
>> Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8245452
>>
>> Webrev:
>> http://cr.openjdk.java.net/~eosterlund/8245452/webrev.00/
>>
>> Thanks,
>> /Erik