76 lines
1.6 KiB
ArmAsm
76 lines
1.6 KiB
ArmAsm
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.define .gto
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.extern .gto
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.gto:
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! nonlocal goto
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! the argument on the stack is a pointer to a GTO-descriptor containing:
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! - the new local base
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! - the new stackpointer
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! - the new program counter
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!
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! The main task of the GTO instruction is to restore the registers
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! used for local variables. It uses a word stored in each stackframe,
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! indicating how many data -and address registers the procedure of
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! that stackframe has.
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move.l (sp)+,a0
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add.l #8,a0 ! a0 now points to new local base entry
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! of the descriptor
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cmp.l (a0),a6 ! GTO within same procedure?
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beq noregs
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move.l d0,savd0 ! gto may not destroy the return area
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move.l d1,savd1
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1:
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tst.l (a6)
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beq err
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unlk a6
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move.w (sp)+,d0 ! word indicating which regs. were saved
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jsr restr
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cmp.l (a0),a6
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bne 1b
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move.l savd0,d0
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move.l savd1,d1
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noregs:
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move.l -4(a0),sp
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move.l -8(a0),a0 ! new program counter
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jmp (a0)
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err:
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move.w #EBADGTO,-(sp)
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jmp .fat
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restr:
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! restore the registers. Note that scratch register a0 may
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! not be changed here. d0 contains (8*#addr.regs + #data regs.)
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! note that registers are assigned in the order d7,d6 .. and
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! a5,a4...
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move.l (sp)+,d2 ! return address; can't use a0 here
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move.w d0,d1
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and.l #7,d0 ! #data registers
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asl.l #1,d0 ! * 2
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lea etabd,a1
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sub.l d0,a1
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jmp (a1)
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move.l (sp)+,d3
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move.l (sp)+,d4
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move.l (sp)+,d5
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move.l (sp)+,d6
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move.l (sp)+,d7
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etabd:
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and.l #070,d1
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asr.l #2,d1 ! # address registers
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lea etaba,a1
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sub.l d1,a1
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jmp (a1)
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move.l (sp)+,a2
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move.l (sp)+,a3
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move.l (sp)+,a4
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move.l (sp)+,a5
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etaba:
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move.l d2,a1
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jmp (a1) ! return
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.data
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savd0: .long 0
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savd1: .long 0
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.text
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