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53 lines
1.1 KiB
ArmAsm
53 lines
1.1 KiB
ArmAsm
;
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; Ullrich von Bassewitz, 05.08.1998
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; Christian Krueger, 11-Mar-2017, ímproved 65SC02 optimization
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; CC65 runtime: long sub
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;
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;
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; EAX = TOS - EAX
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;
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.export tossub0ax, tossubeax
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.import addysp1
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.importzp sp, sreg
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.macpack cpu
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tossub0ax:
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.if (.cpu .bitand ::CPU_ISET_65SC02)
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stz sreg
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stz sreg+1
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.else
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ldy #$00
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sty sreg
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sty sreg+1
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.endif
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tossubeax:
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sec
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eor #$FF
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.if (.cpu .bitand ::CPU_ISET_65SC02)
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adc (sp) ; 65SC02 version - saves 2 cycles
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ldy #1
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.else
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ldy #0
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adc (sp),y ; lo byte
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iny
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.endif
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pha ; Save low byte
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txa
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eor #$FF
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adc (sp),y ; byte 1
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tax
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iny
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lda (sp),y
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sbc sreg ; byte 2
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sta sreg
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iny
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lda (sp),y
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sbc sreg+1 ; byte 3
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sta sreg+1
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pla ; Restore byte 0
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jmp addysp1 ; Drop TOS
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