I fail to see the difference between what you are asking for and BAKR/PR.
BAKR and PC already do a 'hardware' save of the 64-bit registers into
storage that is not accessable by the application. I personally have never
seen a Stack-Full condition and your new instructions could still suffer
from such a condition. BAKR/PC build the Linkage Stack in the 'Home Address
Space' so I don't see much difference to your proposed LSQA. The POP says
that the Linkage Stack is not modifiable except by the BAKR, PC, PR,and
MSTA. So I not sure about the 'HACKER' comment. The ONLY difference I do
see is your wish to use it in SRB mode. I would think that the setup
overhead for using ANY type of PUSHR or BAKR for a SRB could significently
slow down a process that is meant to be fast.
