<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/126569>126569</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [HLSL] Implement the Root Signature Parser for Descriptor Tables
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            HLSL
      </td>
    </tr>

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

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

<pre>
    This issues handles the implementation of parsing the root signature in its token form into the in-memory representation of `RootElement`s. Specifically, it handles all Descriptor Table related tokens and parses these into the `DescriptorTable` and `DescriptorTableClause` struct representation.

This will define all the helper methods of Root Signature Parser needed for the other Root Element types and so it constitutes the "first 90%" of work for implementing the complete parser.

Note that this parser definition will be completely self-contained and can be invoked externally when creating the `HLSLRootSignatureAttr`

AC:
- [ ] Define the in-memory representation of `RootElement`, `DescriptorTable` and `DescriptorTableClause` in `HLSLRootSignatures.h`
- [ ] Define `RootSignatureParser` and provide a public `Parse` that will take an input `RootSignatureLexer` and generate a list of `RootElement`s
- [ ] Implement the internal methods and helper methods required to parse the different types of `RootElements`
- [ ] Add unit testing in `ParseHLSLRootSignatureTest.cpp`
</pre>
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