Vector35 / Vector35/Z80

BIT opcode not lifted correctly

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Dominant language
Python
Stars
12
Forks
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PR merge metrics
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Description

need to set H, unset N, and set Z based on the bit, can probably just change the op that is appended:

    elif decoded.op == OP.BIT:
        assert oper_type == OPER_TYPE.IMM
        assert oper_val >= 0 and oper_val <= 7
        mask = il.const(1, 1<<oper_val)
        operand = operand_to_il(operb_type, operb_val, il, 1)
-         il.append(il.and_expr(1, operand, mask, flags='*'))
+         il.append(il.and_expr(1, operand, mask, flags='z'))

and then manually set the other 2 flags

image

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by locating the Python handler for decoded.op == OP.BIT and the il.and_expr call shown in the issue. Compare the lifted flags with Z80 BIT semantics, then verify that the resulting IL sets Z from the tested bit while setting H and clearing N.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
reverse-engineering
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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