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Free 2 bytes again.
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@ -19,12 +19,12 @@ tosumulax:
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txa ; High byte zero
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beq @L3 ; Do 8x16 multiplication if high byte zero
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stx ptr4+1 ; Save right operand
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jsr popptr1 ; Get left operand (Y=0 by popptr1)
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jsr popptr1 ; Get left operand (Y=0, X untouched by popptr1)
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; Do ptr4:ptr4+1 * ptr1:ptr1+1 --> AX
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tya ; A = 0
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ldx ptr1+1 ; check if lhs is 8 bit only
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tya ; A = 0
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ldy ptr1+1 ; check if lhs is 8 bit only
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beq @L4 ; -> we can do 8x16 after swap
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sta tmp1
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ldy #16 ; Number of bits
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@ -36,7 +36,7 @@ tosumulax:
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clc
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adc ptr1
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tax
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lda ptr1+1 ; hi byte of left op
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lda ptr1+1 ; Hi byte of left op
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adc tmp1
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sta tmp1
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txa
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@ -56,15 +56,15 @@ tosumulax:
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@L3: jmp mul8x16
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; If the high byte of rhs is zero, swap the operands and use the 8x16
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; routine. On entry, A and X are zero
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; If the high byte of lhs is zero, swap the operands in ptr1/4 and
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; use the 8x16 routine. On entry, A and Y are zero and X has the value
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; of ptr4+1
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@L4: ldy ptr1 ; Save right operand (8 bit)
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@L4: stx ptr1+1 ; Store hi-byte from ptr4
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ldy ptr1 ; Save right operand (8 bit)
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ldx ptr4 ; Copy left 16 bit operand to right
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stx ptr1
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ldx ptr4+1 ; swap high-byte too
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stx ptr1+1
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sty ptr4 ; Copy low 8 bit of right op to left
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ldy #8
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jmp mul8x16a
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jmp mul8x16a ; There, ptr4+1 will be also cleared
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