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89 lines
1.4 KiB
ArmAsm
89 lines
1.4 KiB
ArmAsm
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; Ullrich von Bassewitz, 17.08.1998
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; CC65 runtime: switch statement with int selector
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;
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; Subroutine to handle a switch statement with an int selector. The table
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; is located at the return address from the function. It contains the negative
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; of the case label count as first word, followed by two words for each case
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; label, the first one being the value, and the second one the label to jump
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; to in case of a match. The default case is located at the end of the table.
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.export switch
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.importzp ptr1, ptr2, ptr3
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switch: sta ptr1
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stx ptr1+1 ; Save AX
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clc
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pla
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adc #1
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sta ptr2
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pla
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adc #0
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sta ptr2+1 ; Get pointer to table
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ldy #0
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lda (ptr2),y
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sta ptr3
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iny
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lda (ptr2),y
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sta ptr3+1 ; Remember the count of labels
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ldy #0
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clc ; Skip the label count
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lda ptr2
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adc #2
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sta ptr2
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bcc L2
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inc ptr2+1
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bne L2 ; Branch always
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; Search for the label
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L0: lda (ptr2),y
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iny
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cmp ptr1
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beq L4
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L1: iny
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iny
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iny ; Overflow only here
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bne L2
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inc ptr2+1 ; Bump high byte
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; Check if there are any labels left
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L2: inc ptr3
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bne L0
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inc ptr3+1
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bne L0
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; Out of labels
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tya
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clc
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adc ptr2
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sta ptr2
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bcc L3
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inc ptr2+1
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L3: jmp (ptr2)
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; Check high byte
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L4: lda (ptr2),y
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cmp ptr1+1
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bne L1
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; Label found
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iny
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lda (ptr2),y
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sta ptr3
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iny
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lda (ptr2),y
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sta ptr3+1
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jmp (ptr3)
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