GC and pointer masking

[Tony Printezis]

Hi all,

Pointer masking is available for some architectures (including RISC-V!). This can allow us to mark the top bits of an object reference with what type of objects it is (young / old / humongous / etc.) without needing to clear those bits explicitly before we use the reference. This can be helpful both in the GC itself but also in the barriers (e.g., efficiently filter out young objects in barriers that are not needed on young objects).

Has anyone already looked into taking advantage of pointer masking in HotSpot? I tried a couple of searches but I didn’t find anything. If there’s been a discussion on this before, can you please point me to it?

Thanks,

Tony