.export tosumulax, tosmulax
.import mul8x16, mul8x16a ; in mul8.s
- .import popsreg
- .importzp sreg, tmp1, ptr4
+ .import popptr1
+ .importzp tmp1, ptr1, ptr4
;---------------------------------------------------------------------------
txa ; High byte zero
beq @L3 ; Do 8x16 multiplication if high byte zero
stx ptr4+1 ; Save right operand
- jsr popsreg ; Get left operand
+ jsr popptr1 ; Get left operand (Y=0 by popptr1)
-; Do ptr4:ptr4+1 * sreg:sreg+1 --> AX
+; Do ptr4:ptr4+1 * ptr1:ptr1+1 --> AX
- lda #0
- ldx sreg+1 ; Get high byte into register for speed
+ tya ; A = 0
+ ldx ptr1+1 ; check if lhs is 8 bit only
beq @L4 ; -> we can do 8x16 after swap
sta tmp1
ldy #16 ; Number of bits
@L0: bcc @L1
clc
- adc sreg
- pha
- txa ; hi byte of left op
+ adc ptr1
+ tax
+ lda ptr1+1 ; hi byte of left op
adc tmp1
sta tmp1
- pla
+ txa
@L1: ror tmp1
ror a
; If the high byte of rhs is zero, swap the operands and use the 8x16
; routine. On entry, A and X are zero
-@L4: ldy sreg ; Save right operand (8 bit)
+@L4: ldy ptr1 ; Save right operand (8 bit)
ldx ptr4 ; Copy left 16 bit operand to right
- stx sreg
+ stx ptr1
ldx ptr4+1 ; Don't store, this is done later
sty ptr4 ; Copy low 8 bit of right op to left
ldy #8
.export tosumula0, tosmula0
.export mul8x16, mul8x16a
- .import popsreg
- .importzp sreg, ptr4
+ .import popptr1
+ .importzp ptr1, ptr4
;---------------------------------------------------------------------------
tosmula0:
tosumula0:
sta ptr4
-mul8x16:jsr popsreg ; Get left operand
+mul8x16:jsr popptr1 ; Get left operand (Y=0 by popptr1)
- lda #0 ; Clear byte 1
+ tya ; Clear byte 1
ldy #8 ; Number of bits
- ldx sreg+1 ; Get into register for speed
+ ldx ptr1+1 ; check if lhs is 8 bit only
beq mul8x8 ; Do 8x8 multiplication if high byte zero
mul8x16a:
sta ptr4+1 ; Clear byte 2
@L0: bcc @L1
clc
- adc sreg
- pha
- txa ; hi byte of left op
+ adc ptr1
+ tax
+ lda ptr1+1 ; hi byte of left op
adc ptr4+1
sta ptr4+1
- pla
+ txa
@L1: ror ptr4+1
ror a
lsr ptr4 ; Get first bit into carry
@L0: bcc @L1
clc
- adc sreg
+ adc ptr1
@L1: ror
ror ptr4
dey