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

[Pengfei Li (Arm Technology China)]

Hi Andrew,

> > This patch aligns with the implementation in [1] which makes the
> > x86_64
> > r12 register allocatable. Please let me know if I have missed anything
> > for AArch64.
> 
> We don't generally use r27 for compressed class pointers.

Do you mean that r27 is only used for encoding/decoding oops but not for
any klass pointers? I looked at the AArch64 code and find it also used in
MacroAssembler::encode_klass_not_null() if the compressed mode is not
zero-based.

--
Thanks,
Pengfei