;; Originally from GBDK by Pascal Felber.
.area _CODE
-__divschar::
- push de
- push bc
- push ix
- ld ix,#0
- add ix,sp
-
- ld c,8(ix)
- ld e,9(ix)
- call .div8
+__divschar::
+ push bc
+ ld c,l
+
+ call .div8
ld l,c
-
- pop ix
+ ld h,b
+
pop bc
- pop de
ret
__modschar::
- push de
- push bc
- push ix
- ld ix,#0
- add ix,sp
+ push bc
+ ld c,l
- ld c,8(ix)
- ld e,9(ix)
- call .div8
+ call .div8
ld l,e
-
- pop ix
+ ld h,d
+
pop bc
- pop de
ret
__divsint::
- push de
push bc
- push ix
- ld ix,#0
- add ix,sp
+ ld b,h
+ ld c,l
- ld c,8(ix)
- ld b,9(ix)
- ld e,10(ix)
- ld d,11(ix)
call .div16
ld l,c
ld h,b
- pop ix
pop bc
- pop de
ret
__modsint::
- push de
push bc
- push ix
- ld ix,#0
- add ix,sp
+ ld b,h
+ ld c,l
- ld c,8(ix)
- ld b,9(ix)
- ld e,10(ix)
- ld d,11(ix)
call .div16
ld l,e
ld h,d
- pop ix
pop bc
- pop de
ret
;; Unsigned
call .divu8
ld l,c
-
+ ld h,b
+
pop ix
pop bc
pop de
call .divu8
ld l,e
-
+ ld h,d
+
pop ix
pop bc
pop de
ret
__divuint::
- push de
push bc
- push ix
- ld ix,#0
- add ix,sp
-
- ld c,8(ix)
- ld b,9(ix)
- ld e,10(ix)
- ld d,11(ix)
+ ld b,h
+ ld c,l
call .divu16
ld l,c
ld h,b
- pop ix
pop bc
- pop de
ret
__moduint::
- push de
push bc
- push ix
- ld ix,#0
- add ix,sp
+ ld b,h
+ ld c,l
- ld c,8(ix)
- ld b,9(ix)
- ld e,10(ix)
- ld d,11(ix)
call .divu16
ld l,e
ld h,d
- pop ix
pop bc
- pop de
ret
.div8::
LD (.squot),A ; Save sign of quotient
;; Take absolute value of divisor
BIT 7,D
- JR Z,.chkde ; Jump if divisor is positive
+ jp Z,.chkde ; Jump if divisor is positive
SUB A ; Substract divisor from 0
SUB E
LD E,A
;; Take absolute value of dividend
.chkde:
BIT 7,B
- JR Z,.dodiv ; Jump if dividend is positive
+ jp Z,.dodiv ; Jump if dividend is positive
SUB A ; Substract dividend from 0
SUB C
LD C,A
;; Negate quotient if it is negative
LD A,(.squot)
AND #0x80
- JR Z,.dorem ; Jump if quotient is positive
+ jp Z,.dorem ; Jump if quotient is positive
SUB A ; Substract quotient from 0
SUB C
LD C,A
;; Check for division by zero
LD A,E
OR D
- JR NZ,.divide ; Branch if divisor is non-zero
+ jp NZ,.divide ; Branch if divisor is non-zero
LD BC,#0x00 ; Divide by zero error
LD D,B
LD E,C
SCF ; Set carry, invalid result
RET
.divide:
- LD L,C ; L = low byte of dividend/quotient
- LD H,B ; H = high byte of dividend/quotient
- LD BC,#0x00 ; BC = remainder
+ ld hl,#0
+; LD L,C ; L = low byte of dividend/quotient
+; LD H,B ; H = high byte of dividend/quotient
+; LD BC,#0x00 ; BC = remainder
OR A ; Clear carry to start
+ ex af,af
LD A,#16 ; 16 bits in dividend
.dvloop:
;; Shift next bit of quotient into bit 0 of dividend
;; HL holds remainder
;; Do a 32-bit left shift, shifting carry to L, L to H,
;; H to C, C to B
- LD (.dcnt),A
- RL L ; Carry (next bit of quotient) to bit 0
- RL H ; Shift remaining bytes
- RL C
+ ex af,af'
+ RL C ; Carry (next bit of quotient) to bit 0
RL B ; Clears carry since BC was 0
+ adc hl,hl
+
;; If remainder is >= divisor, next bit of quotient is 1. This
;; bit goes to carry
- PUSH BC ; Save current remainder
- LD A,C ; Substract divisor from remainder
- SBC E
- LD C,A
- LD A,B
- SBC D
- LD B,A
+ PUSH HL ; Save current remainder
+ sbc hl,de
+; LD A,C ; Substract divisor from remainder
+; SBC E
+; LD C,A
+; LD A,B
+; SBC D
+; LD B,A
CCF ; Complement borrow so 1 indicates a
; successful substraction (this is the
; next bit of quotient)
- JR C,.drop ; Jump if remainder is >= dividend
- POP BC ; Otherwise, restore remainder
- JR .nodrop
+ jp C,.drop ; Jump if remainder is >= dividend
+ POP HL ; Otherwise, restore remainder
+ jp .nodrop
.drop:
INC SP
INC SP
.nodrop:
- LD A,(.dcnt)
+ ex af,af'
DEC A ; DEC does not affect carry flag
- JR NZ,.dvloop
+ jp NZ,.dvloop
+ ex af,af'
;; Shift last carry bit into quotient
- LD D,B ; DE = remainder
- LD E,C
- RL L ; Carry to L
- LD C,L ; C = low byte of quotient
- RL H
- LD B,H ; B = high byte of quotient
+ LD D,H ; DE = remainder
+ LD E,L
+ RL C ; Carry to L
+; LD C,L ; C = low byte of quotient
+ RL B
+; LD B,H ; B = high byte of quotient
OR A ; Clear carry, valid result
RET
projects / fw / sdcc / blobdiff