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;
; Ullrich von Bassewitz, 17.08.1998
; Christian Krueger, 11-Mar-2017, added 65SC02 optimization
;
; CC65 runtime: division for long unsigned ints
;
.export tosudiv0ax, tosudiveax, getlop, udiv32
.import addysp1
.importzp sp, sreg, tmp3, tmp4, ptr1, ptr2, ptr3, ptr4
.macpack cpu
tosudiv0ax:
.if (.cpu .bitand ::CPU_ISET_65SC02)
stz sreg
stz sreg+1
.else
ldy #$00
sty sreg
sty sreg+1
.endif
tosudiveax:
jsr getlop ; Get the paramameters
jsr udiv32 ; Do the division
lda ptr1 ; Result is in ptr1:sreg
ldx ptr1+1
rts
; Pop the parameters for the long division and put it into the relevant
; memory cells. Called from the signed divisions also.
getlop: sta ptr3 ; Put right operand in place
stx ptr3+1
lda sreg
sta ptr4
lda sreg+1
sta ptr4+1
.if (.cpu .bitand ::CPU_ISET_65SC02)
lda (sp)
ldy #1
.else
ldy #0 ; Put left operand in place
lda (sp),y
iny
.endif
sta ptr1
lda (sp),y
sta ptr1+1
iny
lda (sp),y
sta sreg
iny
lda (sp),y
sta sreg+1
jmp addysp1 ; Drop parameters
; Do (ptr1:sreg) / (ptr3:ptr4) --> (ptr1:sreg), remainder in (ptr2:tmp3:tmp4)
; This is also the entry point for the signed division
udiv32: lda #0
sta ptr2+1
sta tmp3
sta tmp4
; sta ptr1+1
ldy #32
L0: asl ptr1
rol ptr1+1
rol sreg
rol sreg+1
rol a
rol ptr2+1
rol tmp3
rol tmp4
; Do a subtraction. we do not have enough space to store the intermediate
; result, so we may have to do the subtraction twice.
tax
cmp ptr3
lda ptr2+1
sbc ptr3+1
lda tmp3
sbc ptr4
lda tmp4
sbc ptr4+1
bcc L1
; Overflow, do the subtraction again, this time store the result
sta tmp4 ; We have the high byte already
txa
sbc ptr3 ; byte 0
tax
lda ptr2+1
sbc ptr3+1
sta ptr2+1 ; byte 1
lda tmp3
sbc ptr4
sta tmp3 ; byte 2
inc ptr1 ; Set result bit
L1: txa
dey
bne L0
sta ptr2
rts
|
