mirror of
https://gitlab.com/camelot/kickc.git
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208 lines
4.0 KiB
NASM
208 lines
4.0 KiB
NASM
// Commodore 64 PRG executable file
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.file [name="halfscii.prg", type="prg", segments="Program"]
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.segmentdef Program [segments="Basic, Code, Data"]
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.segmentdef Basic [start=$0801]
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.segmentdef Code [start=$80d]
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.segmentdef Data [startAfter="Code"]
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.segment Basic
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:BasicUpstart(main)
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.label SCREEN = $400
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.label CHARGEN = $d000
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.label PROCPORT = 1
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.label D018 = $d018
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.label CHARSET4 = $2800
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.segment Code
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main: {
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.label __1 = 8
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.label __11 = 9
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.label __21 = $a
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.label __30 = $b
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.label chargen1 = 6
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.label charset4 = 4
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.label chargen = 2
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// asm
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sei
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// *PROCPORT = $32
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lda #$32
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sta PROCPORT
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lda #<CHARSET4
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sta.z charset4
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lda #>CHARSET4
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sta.z charset4+1
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lda #<CHARGEN
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sta.z chargen
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lda #>CHARGEN
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sta.z chargen+1
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__b1:
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// byte* chargen1 = chargen+1
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clc
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lda.z chargen
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adc #1
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sta.z chargen1
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lda.z chargen+1
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adc #0
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sta.z chargen1+1
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// *chargen & %01100000
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lda #$60
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ldy #0
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and (chargen),y
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sta.z __1
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// *chargen1 & %01100000
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lda #$60
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and (chargen1),y
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// (*chargen1 & %01100000)/4
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lsr
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lsr
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// (*chargen & %01100000) | (*chargen1 & %01100000)/4
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ora.z __1
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// ((*chargen & %01100000) | (*chargen1 & %01100000)/4)/2
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lsr
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// ((*chargen & %01100000) | (*chargen1 & %01100000)/4)/2/4
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lsr
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lsr
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// byte bits = bits_count[((*chargen & %01100000) | (*chargen1 & %01100000)/4)/2/4]
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tay
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lda bits_count,y
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// if(bits>=2)
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cmp #2
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bcc __b6
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lda #1
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jmp __b2
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__b6:
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lda #0
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__b2:
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// bits_gen = bits_gen*2
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asl
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tax
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// *chargen & %00011000
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lda #$18
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ldy #0
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and (chargen),y
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sta.z __11
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// *chargen1 & %00011000
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lda #$18
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and (chargen1),y
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// (*chargen1 & %00011000)/4
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lsr
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lsr
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// (*chargen & %00011000) | (*chargen1 & %00011000)/4
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ora.z __11
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// ((*chargen & %00011000) | (*chargen1 & %00011000)/4)/2
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lsr
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// bits = bits_count[((*chargen & %00011000) | (*chargen1 & %00011000)/4)/2]
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tay
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lda bits_count,y
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// if(bits>=2)
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cmp #2
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bcc __b3
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// bits_gen = bits_gen + 1
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inx
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__b3:
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// bits_gen = bits_gen*2
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txa
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asl
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tax
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// *chargen & %00000110
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lda #6
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ldy #0
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and (chargen),y
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// (*chargen & %00000110)*2
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asl
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sta.z __21
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// *chargen1 & %00000110
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lda #6
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and (chargen1),y
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// (*chargen1 & %00000110)/2
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lsr
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// (*chargen & %00000110)*2 | (*chargen1 & %00000110)/2
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ora.z __21
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// bits = bits_count[((*chargen & %00000110)*2 | (*chargen1 & %00000110)/2)]
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tay
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lda bits_count,y
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// if(bits>=2)
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cmp #2
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bcc __b4
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// bits_gen = bits_gen + 1
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inx
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__b4:
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// bits_gen = bits_gen*2
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txa
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asl
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tax
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// *chargen & %00000001
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lda #1
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ldy #0
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and (chargen),y
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// (*chargen & %00000001)*4
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asl
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asl
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sta.z __30
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// *chargen1 & %00000001
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lda #1
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and (chargen1),y
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// (*chargen & %00000001)*4 | (*chargen1 & %00000001)
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ora.z __30
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// bits = bits_count[((*chargen & %00000001)*4 | (*chargen1 & %00000001))]
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tay
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lda bits_count,y
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// if(bits>=2)
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cmp #2
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bcc __b5
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// bits_gen = bits_gen + 1
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inx
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__b5:
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// bits_gen = bits_gen*2
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txa
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asl
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// *charset4 = bits_gen
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ldy #0
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sta (charset4),y
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// charset4++;
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inc.z charset4
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bne !+
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inc.z charset4+1
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!:
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// chargen = chargen+2
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lda #2
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clc
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adc.z chargen
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sta.z chargen
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bcc !+
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inc.z chargen+1
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!:
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// while (chargen<CHARGEN+$800)
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lda.z chargen+1
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cmp #>CHARGEN+$800
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bcs !__b1+
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jmp __b1
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!__b1:
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bne !+
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lda.z chargen
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cmp #<CHARGEN+$800
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bcs !__b1+
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jmp __b1
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!__b1:
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!:
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// *PROCPORT = $37
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lda #$37
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sta PROCPORT
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// asm
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cli
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ldx #0
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__b11:
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// SCREEN[i] = i
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txa
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sta SCREEN,x
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// for(byte i : 0..255)
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inx
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cpx #0
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bne __b11
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// *D018 = $19
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lda #$19
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sta D018
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// }
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rts
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}
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.segment Data
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bits_count: .byte 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4
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