<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/111474>111474</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [llvm-mc] llcm-mc cannot decode certain aarch64 instructions
        </td>
    </tr>

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

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

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

<pre>
    My llvm-mc 20.0.0 can decode regular aarch64 instructions, but fail on some special instructions like LSE, MTE extension.

>  ./llvm-mc  --version
  LLVM (http://llvm.org/):
 LLVM version 20.0.0git
  DEBUG build with assertions.

> # llvm-mc works on regular aarch64 instructions
> llvm-mc  -triple=arm64 -disassemble <<< '0x91 0x00 0x22 0x94'   
        .text 
        bl #8913476`

# an CASA instruction word decoded by objdump      
> objdump -d aarch64.o
  000000000044b890 <__aarch64_cas4_acq>: 
  ...
  44b8a0:       88e07c41 casa    w0, w1, [x2]
  ...
  
# But llvm-mc cannot decode LSE instructions like CASA 
> llvm-mc  -triple=arm64  -disassemble <<<  '0x41 0x7c 0xe0 0xc8'
        .text                            
 <stdin>:1:1: warning: invalid instruction encoding
   0x41 0x7c 0xe0 0xc8 
</pre>
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