C Register usage:
define(`RA', `%r14') C Return address
define(`SP', `%r15') C Stack pointer

define(`STANDARD_STACK_FRAME',`160')

C Dynamic stack space allocation
C AP is a general register to which the allocated space is assigned
C SPACE_LEN is the length of space, must be a multiple of 8
C FREE_STACK macro can be used to free the allocated space
C ALLOC_STACK(AP, SPACE_LEN)
define(`ALLOC_STACK',
`lgr            $1,SP
    aghi           SP,-(STANDARD_STACK_FRAME+$2)
    stg            $1,0(SP)
    la             $1,STANDARD_STACK_FRAME (SP)')

C Free allocated stack space
C FREE_STACK(SPACE_LEN)
define(`FREE_STACK',
`aghi           SP,STANDARD_STACK_FRAME+$1')