<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/111247>111247</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Xtensa: Reachable assert in `decodeImm8_sh8Operand()`
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          Rot127
      </td>
    </tr>
</table>

<pre>
    We discovered a reachable assert in the Xtensa disassembler in `decodeImm8_sh8Operand()`.

The immediate given to `decodeImm8_sh8Operand` has already been shifted. Checking if it is an 8bit value fails therefore.

`decodeImm8_sh8Operand` gets called from `XtensaGenDisassemblerTables.inc` like this:
```cpp
...
    if (!Check(S, DecodeARRegisterClass(MI, tmp, Address, Decoder))) { return MCDisassembler::Fail; }
    tmp = fieldFromInstruction(insn, 16, 8) << 8;
    if (!Check(S, decodeImm8_sh8Operand(MI, tmp, Address, Decoder))) { return MCDisassembler::Fail; }
    return S;
...
```

Fix (in C): https://github.com/capstone-engine/llvm-capstone/pull/62
</pre>
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