RFR: 8305896: Alternative full GC forwarding [v29]

[Roman Kennke]

On Thu, 4 May 2023 12:56:11 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add usual header include guards
>
> src/hotspot/share/gc/shared/slidingForwarding.inline.hpp line 87:
> 
>> 85:   assert(to == decode_forwarding(from, encoded), "must be reversible");
>> 86:   return encoded;
>> 87: }
> 
> Since encoding should produce a 32-bit value, why not return a 32-bit value? Same below, for decoding. Or, at least assert that returned value has no higher bits set.

I'm adding asserts. The encoded value will be or-ed into the mark-word which is 64bit anyway, I don't see much value to use 32bit here and then require up-casting and stuff like that. Type mess tends to make compilers unhappy ;-)

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PR Review Comment: https://git.openjdk.org/jdk/pull/13582#discussion_r1185257704