<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/89952>89952</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [DirectX] Fix DXIL part header version encoding
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            backend:DirectX
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          llvm-beanz
      </td>
    </tr>
</table>

<pre>
    Today we are encoding the DXIL version in the DXIL part's program header backwards. Compiling a shader targeting `lib_6_8` with DXC then disassembling it with `obj2yaml` prints:

```
      DXILMajorVersion: 8
      DXILMinorVersion: 1
```

This probably means we're crossing the ordering of the fields somewhere in our handling.

We also need to set the DXIL version from the triple sub-architecture. Right now during DXIL header generation we are not setting the version. See [here](https://github.com/llvm/llvm-project/blob/main/llvm/lib/MC/MCDXContainerWriter.cpp#L121) where we set the shader model version but we don't set the DXIL version.

## Acceptance Criteria

* Updated obj2yaml tests verifying correct reproduction of major and minor versions.
* Updated llc -> obj2yaml testing verifying correct code generation from llc.
</pre>
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