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70 lines
1.0 KiB
ArmAsm
70 lines
1.0 KiB
ArmAsm
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; Ullrich von Bassewitz, 13.08.1998
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; CC65 runtime: multiplication for long (unsigned) ints
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;
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.export tosumul0ax, tosumuleax, tosmul0ax, tosmuleax
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.import addysp1
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.importzp sp, sreg, tmp1, tmp2, tmp3, tmp4, ptr1, ptr3, ptr4
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tosmul0ax:
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tosumul0ax:
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ldy #$00
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sty sreg
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sty sreg+1
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tosmuleax:
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tosumuleax:
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mul32: sta ptr1
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stx ptr1+1 ; op2 now in ptr1/sreg
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ldy #0
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lda (sp),y
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sta ptr3
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iny
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lda (sp),y
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sta ptr3+1
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iny
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lda (sp),y
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sta ptr4
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iny
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lda (sp),y
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sta ptr4+1 ; op1 in pre3/ptr4
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jsr addysp1 ; Drop TOS
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; Do (ptr1:sreg)*(ptr3:ptr4) --> EAX.
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lda #0
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sta tmp4
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sta tmp3
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sta tmp2
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ldy #32
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L0: lsr tmp4
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ror tmp3
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ror tmp2
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ror a
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ror sreg+1
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ror sreg
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ror ptr1+1
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ror ptr1
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bcc L1
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clc
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adc ptr3
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pha
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lda ptr3+1
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adc tmp2
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sta tmp2
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lda ptr4
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adc tmp3
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sta tmp3
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lda ptr4+1
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adc tmp4
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sta tmp4
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pla
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L1: dey
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bpl L0
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lda ptr1 ; Load the low result word
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ldx ptr1+1
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rts
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