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float problems on c64
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Irmen de Jong
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e97303c226
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15c649024e
@ -1,7 +1,7 @@
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TODO
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====
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- fix on c64 target: examples/cube3d-float (broken since 9.3 with the evalstack removal) it works on x16 target, oddly enough.
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More detailed and simpler code for this problem in floatproblem64.p8
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More detailed and simpler code for this problem in floatproblem64.p8 / floatproblem64.asm (the minified version)
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- fix: search for TODO("swap operand order")
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- optimize: search for TODO optimize: don't use scratch var
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144
floatproblem64.asm
Normal file
144
floatproblem64.asm
Normal file
@ -0,0 +1,144 @@
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.cpu '6502'
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CHROUT = $FFD2
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; C64 addresses for float routines:
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;MOVFM = $bba2
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;CONUPK = $ba8c
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;MOVAF = $bc0c
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;MOVMF = $bbd4
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;FOUT = $bddd
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;FADDT = $b86a
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;FMULTT = $ba2b
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; CX16 addresses for float routines:
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MOVFM = $fe63
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CONUPK = $fe5a
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MOVAF = $fe6c
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MOVMF = $fe66
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FOUT = $fe06
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FADDT = $fe1b
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FMULTT = $fe21
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* = $0801
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; 10 SYS 2062
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.word (+), 10
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.null $9e, " 2062"
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+ .word 0
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; program starts here at address 2062
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lda #$8d
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jsr CHROUT
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; calculate: value1*one + value2*one
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; (yes the multiplications with one do nothing value-wise, but they influence the routines being called...)
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lda #<prog8_float_const_0 ; -0.8
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ldy #>prog8_float_const_0
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jsr MOVFM ; FAC1 = -0.8
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lda #<float_const_one ; 1.0
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ldy #>float_const_one
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jsr CONUPK ; ARG = 1.0
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jsr FMULTT ; FAC1 = -0.8*1.0 = -0.8
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jsr pushFAC1 ; save value...
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lda #<prog8_float_const_1 ; 0.3
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ldy #>prog8_float_const_1
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jsr MOVFM ; FAC1 = 0.3
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lda #<float_const_one ; 1.0
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ldy #>float_const_one
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jsr CONUPK ; ARG = 1.0
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jsr FMULTT ; FAC1 = 0.3*1.0 = 0.3
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jsr MOVAF ; ARG = FAC1 = 0.3
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jsr popFAC1 ; restore value... (-0.8)
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jsr FADDT ; FAC1 = -0.8 + 0.3 = -0.5
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; ... result in FAC1 will be wrong on C64 (1.1 instead of -0.5)....
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; print FAC1
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jsr FOUT ; fac1 to string in A/Y
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sta _mod+1
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sty _mod+2
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ldy #0
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_mod lda $ffff,y ; modified
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beq +
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jsr CHROUT
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iny
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bne _mod
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+ lda #$8d
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jsr CHROUT
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; print expected
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ldy #0
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- lda string_1,y
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beq +
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jsr CHROUT
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iny
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bne -
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+ rts
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string_1
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.text "-.5 was expected",$8d,0
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floats_temp_var .byte 0,0,0,0,0 ; temporary storage for a float
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pushFAC1
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;-- push floating point in FAC onto the cpu stack
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; save return address
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pla
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sta returnaddr
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pla
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sta returnaddr+1
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ldx #<floats_temp_var
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ldy #>floats_temp_var
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jsr MOVMF
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lda floats_temp_var
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pha
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lda floats_temp_var+1
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pha
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lda floats_temp_var+2
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pha
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lda floats_temp_var+3
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pha
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lda floats_temp_var+4
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pha
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; re-push return address
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lda returnaddr+1
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pha
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lda returnaddr
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pha
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rts
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returnaddr .word 0
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popFAC1
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; -- pop floating point value from cpu stack into FAC1
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; save return address
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pla
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sta returnaddr
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pla
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sta returnaddr+1
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pla
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sta floats_temp_var+4
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pla
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sta floats_temp_var+3
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pla
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sta floats_temp_var+2
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pla
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sta floats_temp_var+1
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pla
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sta floats_temp_var
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lda #<floats_temp_var
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ldy #>floats_temp_var
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jsr MOVFM
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; re-push return address
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lda returnaddr+1
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pha
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lda returnaddr
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pha
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rts
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; global float constants
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prog8_float_const_0 .byte $80, $cc, $cc, $cc, $cc ; float -0.8
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prog8_float_const_1 .byte $7f, $19, $99, $99, $99 ; float 0.3
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float_const_one .byte $81, $00, $00, $00, $00 ; float 1.0
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@ -1,32 +1,57 @@
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%import textio
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%import floats
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%import test_stack
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%zeropage dontuse
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main {
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sub start() {
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float value1 = -0.8
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float value2 = 0.3
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float two = 2.0
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float one = 1.0
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float result = value1*two + value2*two ; TODO FIX: invalid result on c64, ok when the *two is removed or expression is split (it's not caused by pushFAC1/popFAC1)
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float result = value1*one + value2*one ; TODO FIX: invalid result on c64, ok when the *one is removed or expression is split (it's not caused by pushFAC1/popFAC1)
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; TODO is it floats.CONUPK??
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floats.print_f(result)
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txt.nl()
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txt.print("-1 was expected\n\n") ; on C64: -1.1 is printed :(
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txt.print("-.5 was expected\n\n") ; on C64: -1.1 is printed :(
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result = value2*two + value1*two ; swapped operands around, now it's suddenly fine on C64...
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floats.print_f(result)
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txt.nl()
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txt.print("-1 was expected\n\n") ; on C64: correct value is printed
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; result = value2*one + value1*one ; swapped operands around, now it's suddenly fine on C64...
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; floats.print_f(result)
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; txt.nl()
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; txt.print("-.5 was expected\n\n") ; on C64: correct value is printed
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value1 = 0.8
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value2 = 0.3
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result = value1*two + value2*two
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floats.print_f(result)
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txt.nl()
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txt.print("2.2 was expected\n\n") ; on C64: correct value is printed
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; value1 = 0.8
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; value2 = 0.3
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; result = value1*one + value2*one
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; floats.print_f(result)
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; txt.nl()
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; txt.print("1.1 was expected\n\n") ; on C64: correct value is printed
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;
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; printFAC1()
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; printFAC1()
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; printFAC1()
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repeat {
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}
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}
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sub printFAC1() {
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ubyte[20] fac_save
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sys.memcopy($60, fac_save, sizeof(fac_save))
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txt.print("fac1=")
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%asm {{
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jsr floats.FOUT ; fac1 to string in A/Y
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sta P8ZP_SCRATCH_W1
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sty P8ZP_SCRATCH_W1+1
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ldy #0
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- lda (P8ZP_SCRATCH_W1),y
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beq +
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jsr cbm.CHROUT
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iny
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bne -
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+ }}
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txt.nl()
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sys.memcopy(fac_save, $60, sizeof(fac_save))
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}
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}
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