[aarch64-port-dev ] RFR(M): 8233743: AArch64: Make r27 conditionally allocatable

[Pengfei Li (Arm Technology China)]

Hi Andrew,

> We should have a flag which is set if the search for nicely-aligned memory is
> successful, and then you can use that flag to determine if r27 is needed.

I just found in current HotSpot code, UseCompressedOops must be on for
UseCompressedClassPointers to be on. See arguments.cpp [1].

If this is true, UseCompressedClassPointers cannot be used without
UseCompressedOops. So wouldn't a single condition of UseCompressedOops be
enough? But the x86_64 code which I referenced has both two conditions.
Is it because the relationship of the arguments are subject to change in the
future?

[1] http://hg.openjdk.java.net/jdk/jdk/file/7bdc4f073c7f/src/hotspot/share/runtime/arguments.cpp#l1715

--
Thanks,
Pengfei