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

[Vladimir Kozlov]

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