90 lines
1 KiB
ArmAsm
90 lines
1 KiB
ArmAsm
.define .dvi4
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.sect .text
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.sect .rom
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.sect .data
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.sect .bss
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.sect .text
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! 4-byte divide routine for z80
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! parameters:
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! stack: divisor
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! dividend
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! stack: quotient (out)
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! bc de: remainder (out) (high part in bc)
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.dvi4:
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pop hl
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ld (retaddr),hl
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xor a
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ld (.flag1),a
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ld (.flag2),a
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ld ix,0
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add ix,sp
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ld b,(ix+7) ! dividend
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bit 7,b
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jr z,1f
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ld c,(ix+6)
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ld d,(ix+5)
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ld e,(ix+4)
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call .negbd
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ld (ix+7),b
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ld (ix+6),c
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ld (ix+5),d
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ld (ix+4),e
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ld a,1
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ld (.flag1),a
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1:
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ld b,(ix+3)
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bit 7,b
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jr z,2f
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call .negst
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ld a,1
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ld (.flag2),a
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2:
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call .dvu4
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ld a,(.flag1)
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or a
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jr z,3f
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call .negbd
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3:
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ld (.savebc),bc
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ld (.savede),de
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ld a,(.flag2)
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ld b,a
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ld a,(.flag1)
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xor b
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jr z,4f
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call .negst
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4:
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ld bc,(.savebc)
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ld de,(.savede)
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ld hl,(retaddr)
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jp (hl)
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.negbd:
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xor a
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ld h,a
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ld l,a
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sbc hl,de
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ex de,hl
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ld h,a
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ld l,a
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sbc hl,bc
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ld b,h
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ld c,l
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ret
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.negst:
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pop ix
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pop de
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pop bc
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call .negbd
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push bc
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push de
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jp (ix)
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.sect .data
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.flag1: .data1 0
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.flag2: .data1 0
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retaddr:.data2 0
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.savebc: .data2 0
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.savede: .data2 0
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