<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/124579>124579</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [HLSL][SPIRV] Add subpass inputs
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            HLSL,
            SPIR-V
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
            s-perron
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          s-perron
      </td>
    </tr>
</table>

<pre>
    Subpass inputs are a Vulkan specific resource type. They are useful for mobile platforms, and we want to add them the clang as well. The problem is that in DXC, they were not added in the vk namespace, and they should be. Here are the steps to implement this feature:

- [ ] Update the spec to more `SubpassInput` to the `vk` namespace.
- [ ] Design how the resource will be represented in the AST
- [ ] Add the type to HLSLExternalSemaSource.cpp
- [ ] Implement the `vk::input_attachment_index` attribute.
- [ ] Generate the correct target type for the subpass input
- [ ] Generate intrinsics to do the subpass load.
- [ ] Resubmit the tests removed in https://github.com/llvm/llvm-project/pull/122355 that relate to subpass inputs.
</pre>
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