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    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - [AMDGPU][MC][GFX9] Disassembler failed to decode SMEM with IMM=0 and OFFSET>127"
   href="https://bugs.llvm.org/show_bug.cgi?id=49819">49819</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[AMDGPU][MC][GFX9] Disassembler failed to decode SMEM with IMM=0 and OFFSET>127
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libraries
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Windows NT
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Backend: AMDGPU
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>dpreobrazhensky@luxoft.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Debug build of disassembler triggers an assert when trying to decode the
following GFX9 code:

    0xc28948ff, 0x48b84d8b

The code is actually an illegal variant of s_atomic_add_x2:


SOFFSET      OFFSET                        OP     IMM GLC SOE SDATA   SBASE
|            |                             |        | |   |   |       |
0100100.0101.110000100110110001011  110000.10100010.0.1.0.1.0.0100011.111111  
|                                          |                  |       |
36                                         162                35      EXEC=126

The code is invalid for several reasons including:
  - unaligned SDATA
  - SBASE=EXEC
  - IMM=0 but OFFSET is not a valid SGPR

The last issue caused disassembler to assert.</pre>
        </div>
      </p>


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