66 lines
1.4 KiB
ArmAsm
66 lines
1.4 KiB
ArmAsm
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.define Gto
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! This subroutine performs the non_local goto.
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! The address of the descriptor is stored in zeropage locations
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! ADDR, ADDR+1.
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! Since there are two stacks (hardware_stack and the real_stack),
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! the stackpointer of the hard_stack is resetted by searching the
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! new localbase in the real_stack while adjusting the hardware_stack.
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Gto:
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stx ADDR ! address of descripto (lowbyte)
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sta ADDR+1 ! address of descriptor (highbyte)
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pla ! remove
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pla ! __gto return address.
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ldy #4
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lda (ADDR),y ! new localbase (lowbyte)
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sta ARTH
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tax
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iny
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lda (ADDR),y ! new localbase (highbyte)
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sta ARTH+1
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cmp LB+1
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bne 1f
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cpx LB
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beq 2f ! goto within same procedure
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1: ldy #0
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lda (LB),y ! get localbase (lowbyte)
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tax
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iny
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lda (LB),y ! get localbase (highbyte)
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cmp ARTH+1
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bne 3f
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cpx ARTH
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beq 2f ! found localbase
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3: stx LB ! temporary save of localbase
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sta LB+1
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pla ! adjust
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pla ! hardware_stack
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jmp 1b
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2: sta LB+1 ! store localbase (highbyte)
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pha
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stx LB ! store localbase (lowbyte)
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sec
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txa
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sbc #BASE
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sta LBl ! localbase - 240 (lowbyte)
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pla
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sbc #0
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sta LBl+1 ! localbase - 240 (highbyte)
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ldy #3
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lda (ADDR),y ! new stackpointer (highbyte)
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sta SP+1
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dey
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lda (ADDR),y ! new stackpointer (lowbyte)
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sta SP+2
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dey
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lda (ADDR),y ! jump address (highbyte)
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sta ADDR+3
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dey
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lda (ADDR),y ! jump address (lowbyte)
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sta ADDR+2
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jmp (ADDR+2) ! jump to address
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