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48 lines
616 B
ArmAsm
48 lines
616 B
ArmAsm
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; Ullrich von Bassewitz, 05.08.1998
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;
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; CC65 runtime: add ints
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;
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; Make this as fast as possible, even if it needs more space since it's
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; called a lot!
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.export tosadda0, tosaddax
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.importzp sp, tmp1
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tosadda0:
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ldx #0
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tosaddax:
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ldy #0
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clc
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adc (sp),y ; lo byte
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sta tmp1 ; save it
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txa
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iny
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adc (sp),y ; hi byte
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tax
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clc
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lda sp
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adc #2
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sta sp
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bcc L1
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inc sp+1
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L1: txa ; Test high byte
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bmi L2
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bne L3
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lda tmp1 ; Get low byte
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rts
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; Value is negative
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L2: lda tmp1 ; Get low byte
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ldy #$FF ; Force negative
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rts
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; Value is positive != 0
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L3: lda tmp1 ; Get low byte
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ldy #1
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rts
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