ESP 12 SUB
! Save top of data stack in non-volatile register
%prepare-unbox
+ push-vm-ptr
EAX PUSH
! Restore data/call/retain stacks
"unnest_stacks" f %alien-invoke
! Place top of data stack in EAX
EAX POP
+ temp-reg POP
! Restore C stack
ESP 12 ADD
! Unbox EAX