6502basiccompiler/arch/6502/__sandbox__/library-asm/sub32.asm

; SUB32
; TOP of the stack - DEHL
; Pops operand out of the stack (CALLEE)
; and returns result in DEHL
; Operands come reversed => So we swap then using EX (SP), HL
;
__SUB32:
lda z80_c     ;- exx
ldx z80_cp
stx z80_c
sta z80_cp
lda z80_b
ldx z80_bp
stx z80_b
sta z80_bp
lda z80_e
ldx z80_ep
stx z80_e
sta z80_ep
lda z80_d
ldx z80_dp
stx z80_d
sta z80_dp
lda z80_l
ldx z80_lp
stx z80_l
sta z80_lp
lda z80_h
ldx z80_hp
stx z80_h
sta z80_hp
pla            ;- pop bc		; Return address
sta z80_b
pla
sta z80_c
lda z80_c     ;- exx
ldx z80_cp
stx z80_c
sta z80_cp
lda z80_b
ldx z80_bp
stx z80_b
sta z80_bp
lda z80_e
ldx z80_ep
stx z80_e
sta z80_ep
lda z80_d
ldx z80_dp
stx z80_d
sta z80_dp
lda z80_l
ldx z80_lp
stx z80_l
sta z80_lp
lda z80_h
ldx z80_hp
stx z80_h
sta z80_hp
tsx             ;- ex (sp),hl
lda $0103,x
ldy z80_h
sta z80_h
tya
sta $0103,x
lda $0104,x
ldy z80_l
sta z80_l
tya
sta $104,x
pla            ;- pop bc
sta z80_b
pla
sta z80_c
ora z80_a      ;- or a
lda z80_l      ;- sbc hl,bc
sbc z80_c
sta z80_l
lda z80_h
sbc z80_b
sta z80_h
lda z80_e      ;- ex_de_hl
ldx z80_l
stx z80_e
sta z80_l
lda z80_d
ldx z80_h
stx z80_d
sta z80_h
tsx             ;- ex (sp),hl
lda $0103,x
ldy z80_h
sta z80_h
tya
sta $0103,x
lda $0104,x
ldy z80_l
sta z80_l
tya
sta $104,x
pla            ;- pop bc
sta z80_b
pla
sta z80_c
lda z80_l      ;- sbc hl,bc
sbc z80_c
sta z80_l
lda z80_h
sbc z80_b
sta z80_h
lda z80_e      ;- ex_de_hl
ldx z80_l
stx z80_e
sta z80_l
lda z80_d
ldx z80_h
stx z80_d
sta z80_h
lda z80_c     ;- exx
ldx z80_cp
stx z80_c
sta z80_cp
lda z80_b
ldx z80_bp
stx z80_b
sta z80_bp
lda z80_e
ldx z80_ep
stx z80_e
sta z80_ep
lda z80_d
ldx z80_dp
stx z80_d
sta z80_dp
lda z80_l
ldx z80_lp
stx z80_l
sta z80_lp
lda z80_h
ldx z80_hp
stx z80_h
sta z80_hp
lda z80_c      ;- push bc		; Put return address
pha
lda z80_b
pha
lda z80_c      ;- exx
ldx z80_cp
stx z80_c
sta z80_cp
lda z80_b
ldx z80_bp
stx z80_b
sta z80_bp
lda z80_e
ldx z80_ep
stx z80_e
sta z80_ep
lda z80_d
ldx z80_dp
stx z80_d
sta z80_dp
lda z80_l
ldx z80_lp
stx z80_l
sta z80_lp
lda z80_h
ldx z80_hp
stx z80_h
sta z80_hp
rts            ;- ret