mirror of https://github.com/mist64/msbasic.git
155 lines
3.4 KiB
ArmAsm
155 lines
3.4 KiB
ArmAsm
; generic stack and memory management code
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; this code is identical across all versions of
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; BASIC
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.segment "CODE"
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; ----------------------------------------------------------------------------
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; CALLED BY "NEXT" AND "FOR" TO SCAN THROUGH
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; THE STACK FOR A FRAME WITH THE SAME VARIABLE.
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;
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; (FORPNT) = ADDRESS OF VARIABLE IF "FOR" OR "NEXT"
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; = $XXFF IF CALLED FROM "RETURN"
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; <<< BUG: SHOULD BE $FFXX >>>
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;
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; RETURNS .NE. IF VARIABLE NOT FOUND,
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; (X) = STACK PNTR AFTER SKIPPING ALL FRAMES
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;
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; .EQ. IF FOUND
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; (X) = STACK PNTR OF FRAME FOUND
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; ----------------------------------------------------------------------------
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GTFORPNT:
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tsx
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inx
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inx
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inx
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inx
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L2279:
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lda STACK+1,x
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cmp #$81
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bne L22A1
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lda FORPNT+1
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bne L228E
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lda STACK+2,x
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sta FORPNT
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lda STACK+3,x
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sta FORPNT+1
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L228E:
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cmp STACK+3,x
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bne L229A
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lda FORPNT
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cmp STACK+2,x
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beq L22A1
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L229A:
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txa
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clc
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adc #BYTES_PER_FRAME
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tax
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bne L2279
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L22A1:
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rts
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; ----------------------------------------------------------------------------
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; MOVE BLOCK OF MEMORY UP
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;
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; ON ENTRY:
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; (Y,A) = (HIGHDS) = DESTINATION END+1
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; (LOWTR) = LOWEST ADDRESS OF SOURCE
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; (HIGHTR) = HIGHEST SOURCE ADDRESS+1
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; ----------------------------------------------------------------------------
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BLTU:
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jsr REASON
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sta STREND
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sty STREND+1
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BLTU2:
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sec
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lda HIGHTR
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sbc LOWTR
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sta INDEX
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tay
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lda HIGHTR+1
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sbc LOWTR+1
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tax
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inx
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tya
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beq L22DD
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lda HIGHTR
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sec
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sbc INDEX
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sta HIGHTR
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bcs L22C6
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dec HIGHTR+1
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sec
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L22C6:
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lda HIGHDS
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sbc INDEX
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sta HIGHDS
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bcs L22D6
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dec HIGHDS+1
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bcc L22D6
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L22D2:
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lda (HIGHTR),y
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sta (HIGHDS),y
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L22D6:
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dey
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bne L22D2
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lda (HIGHTR),y
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sta (HIGHDS),y
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L22DD:
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dec HIGHTR+1
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dec HIGHDS+1
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dex
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bne L22D6
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rts
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; ----------------------------------------------------------------------------
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; CHECK IF ENOUGH ROOM LEFT ON STACK
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; FOR "FOR", "GOSUB", OR EXPRESSION EVALUATION
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; ----------------------------------------------------------------------------
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CHKMEM:
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asl a
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adc #SPACE_FOR_GOSUB
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bcs MEMERR
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sta INDEX
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tsx
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cpx INDEX
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bcc MEMERR
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rts
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; ----------------------------------------------------------------------------
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; CHECK IF ENOUGH ROOM BETWEEN ARRAYS AND STRINGS
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; (Y,A) = ADDR ARRAYS NEED TO GROW TO
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; ----------------------------------------------------------------------------
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REASON:
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cpy FRETOP+1
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bcc L231E
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bne L22FC
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cmp FRETOP
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bcc L231E
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L22FC:
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pha
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ldx #FAC-TEMP1-1
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tya
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L2300:
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pha
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lda TEMP1,x
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dex
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bpl L2300
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jsr GARBAG
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ldx #TEMP1-FAC+1
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L230B:
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pla
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sta FAC,x
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inx
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bmi L230B
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pla
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tay
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pla
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cpy FRETOP+1
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bcc L231E
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bne MEMERR
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cmp FRETOP
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bcs MEMERR
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L231E:
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rts
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