53 lines
773 B
ArmAsm
53 lines
773 B
ArmAsm
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.define .rck
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! Range check
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! Expects on stack: address of range check descriptor
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! index
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! Yields index on stack unchanged
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! Causes a trap if index is out of bounds
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.rck: pop h
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shld .retadr
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mov h,b
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mov l,c
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shld .bcreg
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pop h ! hl = return address
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pop d ! de = index
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mov c,m ! bc = lower bound
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inx h
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mov b,m
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inx h
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mov a,d
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xor b
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jm 1f ! jump if index and l.b. have different signs
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mov a,e
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sub c
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mov a,d
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sbb b
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jmp 2f
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1: xor b ! now a = d again
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2: cm erange ! trap if index too small
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mov c,m
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inx h
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mov b,m
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mov a,d
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xor b
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jm 1f ! jump if index and u.b. have different signs
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mov a,c
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sub e
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mov a,b
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sbb d
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jmp 2f
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1: xor d ! now a = b
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2: cm erange ! trap if index is too large
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lhld .bcreg
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mov b,h
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mov c,l
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lhld .retadr
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pchl
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