.ref-Research-V6/usr/source/tmg/tmgb/stack.s

/ builtins for shift-reduce parsking
f = r5
i = r3
g = r4
.globl succ,pbundle,goto,iget
.globl g1
.globl stack,unstack,gotab,accept

/stack label of present rule (state)
/should come first in a rule

stack:
        mov     i,(g)
        sub     $2,(g)+
        jmp     succ

/unstack(n) deletes last n stacked states
/states are distinguishable from translations in not having
/an exit bit ($1) nor being bundles ($100000)
unstack:
        jsr     pc,iget
        mov     (r0),r0
        mov     g,r1
1:
        bit     -(r1),$100001
        bne     1b
        dec     r0
        bge     1b
        tst     (r1)+
        br      1f

accept:                 /clean out all states from stack
        mov     f,r1
        add     $g1,r1
1:
        mov     r1,r0
        mov     r1,-(sp)
1:
        cmp     r1,g
        bge     2f
        bit     (r1)+,$100001
        beq     1b
        mov     -2(r1),(r0)+
        br      1b
2:
        mov     r0,g
        mov     (sp)+,r0
        jsr     pc,pbundle
        tst     r0
        beq     1f
        mov     r0,(g)+
1:
        jmp     succ

/gotab(s1,t1,s2,t2,...sn,tn,0,t)
/checks top of stack for states
/s1,s2,... and goes to t1, t2 accordingly
/if top of stack is not in table, goes to t

gotab:
        mov     g,r0
1:
        bit     -(r0),$100001   /find top state
        bne     1b
        mov     (r0),-(sp)
1:
        jsr     pc,iget
        tst     (r0)
        beq     1f
        cmp     (sp),r0
        beq     1f
        jsr     pc,iget
        br      1b
1:
        tst     (sp)+
        jmp     goto