usr/source/s1/as17.s

/
/ copyright 1972 bell telephone laboratories inc.
/

/  a7 -- pdp-11 assembler pass 1

expres:
        mov     r5,-(sp)
        mov     $'+,-(sp)
        clr     opfound
        clr     r2
        mov     $1,r3
        br      1f
advanc:
        jsr     pc,readop
1:
        mov     r4,r0
        jsr     r5,betwen; 0; 177
                br .+4
        br      7f
        movb    (r4),r0
        mov     2(r4),r1
        br      oprand
7:
        cmp     r4,$141
        blo     1f
        cmp     r4,$141+10.
        bhis    2f
        movb    curfbr-141(r4),r0
        asl     r4
        mov     curfb-[2*141](r4),r2
        bpl     oprand
        jsr     r5,error; 'f
        br      oprand
2:
        clr     r3
        clr     r2
        br      oprand
1:
        mov     $esw1,r1
1:
        cmp     (r1)+,r4
        beq     1f
        tst     (r1)+
        bne     1b
        tst     opfound
        bne     2f
        jsr     pc,errore
2:
        tst     (sp)+
        mov     (sp)+,r5
        rts     pc
1:
        jmp     *(r1)

esw1:
        '+;     binop
        '-;     binop
        '*;     binop
        '/;     binop
        '&;     binop
        037;    binop
        035;    binop
        036;    binop
        '%;     binop
        '[;     brack
        '^;     binop
        1;      exnum
        '!;     binop
        0;      0

binop:
        cmpb    (sp),$'+
        beq     1f
        jsr     pc,errore
1:
        movb    r4,(sp)
        br      advanc

exnum:
        mov     numval,r1
        mov     $1,r0
        br      oprand

brack:
        mov     r2,-(sp)
        mov     r3,-(sp)
        jsr     pc,readop
        jsr     pc,expres
        cmp     r4,$']
        beq     1f
        jsr     r5,error; ']
1:
        mov     r3,r0
        mov     r2,r1
        mov     (sp)+,r3
        mov     (sp)+,r2

oprand:
        inc     opfound
        mov     $exsw2,r5
1:
        cmp     (sp),(r5)+
        beq     1f
        tst     (r5)+
        bne     1b
        br      eoprnd
1:
        jmp     *(r5)

exsw2:
        '+; exadd
        '-; exsub
        '*; exmul
        '/; exdiv
        037; exor
        '&; exand
        035;exlsh
        036;exrsh
        '%; exmod
        '!; exnot
        '^; excmbin
        0;  0

excmbin:
        mov     r0,r3                   / give left flag of right
        br      eoprnd

exrsh:
        neg     r1
        beq     exlsh
        inc     r1
        clc
        ror     r2
exlsh:
        jsr     r5,combin; 0
        als     r1,r2
        br      eoprnd

exmod:
        jsr     r5,combin; 0
        mov     r1,-(sp)
        mov     r2,r1
        clr     r0
        dvd     (sp)+,r0
        mov     r1,r2
        br      eoprnd

exadd:
        jsr     r5,combin; 0
        add     r1,r2
        br      eoprnd

exsub:
        jsr     r5,combin; 1
        sub     r1,r2
        br      eoprnd

exand:
        jsr     r5,combin; 0
        com     r1
        bic     r1,r2
        br      eoprnd

exor:
        jsr     r5,combin; 0
        bis     r1,r2
        br      eoprnd

exmul:
        jsr     r5,combin; 0
        mpy     r2,r1
        mov     r1,r2
        br      eoprnd

exdiv:
        jsr     r5,combin; 0
        mov     r1,-(sp)
        mov     r2,r1
        clr     r0
        dvd     (sp)+,r0
        mov     r0,r2
        br      eoprnd

exnot:
        jsr     r5,combin; 0
        com     r1
        add     r1,r2
        br      eoprnd

eoprnd:
        mov     $'+,(sp)
        jmp     advanc

combin:
        mov     r0,-(sp)
        bis     r3,(sp)
        bic     $!40,(sp)
        bic     $!37,r0
        bic     $!37,r3
        cmp     r0,r3
        ble     1f
        mov     r0,-(sp)
        mov     r3,r0
        mov     (sp)+,r3
1:
        tst     r0
        beq     1f
        tst     (r5)+
        beq     2f
        cmp     r0,r3
        bne     2f
        mov     $1,r3
        br      2f
1:
        tst     (r5)+
        clr     r3
2:
        bis     (sp)+,r3
        rts     r5