<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/99232>99232</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
Implement the `DispatchMesh` HLSL Function
</td>
</tr>
<tr>
<th>Labels</th>
<td>
metabug,
backend:DirectX,
HLSL,
backend:SPIR-V,
bot:HLSL
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
farzonl
</td>
</tr>
</table>
<pre>
- [ ] Implement `DispatchMesh` clang builtin,
- [ ] Link `DispatchMesh` clang builtin with `hlsl_intrinsics.h`
- [ ] Add sema checks for `DispatchMesh` to `CheckHLSLBuiltinFunctionCall` in `SemaChecking.cpp`
- [ ] Add codegen for `DispatchMesh` to `EmitHLSLBuiltinExpr` in `CGBuiltin.cpp`
- [ ] Add codegen tests to `clang/test/CodeGenHLSL/builtins/DispatchMesh.hlsl`
- [ ] Add sema tests to `clang/test/SemaHLSL/BuiltIns/DispatchMesh-errors.hlsl`
- [ ] Create the `int_dx_DispatchMesh` intrinsic in `IntrinsicsDirectX.td`
- [ ] Create the `DXILOpMapping` of `int_dx_DispatchMesh` to `173` in `DXIL.td`
- [ ] Create the `DispatchMesh.ll` and `DispatchMesh_errors.ll` tests in `llvm/test/CodeGen/DirectX/`
- [ ] Create the `int_spv_DispatchMesh` intrinsic in `IntrinsicsSPIRV.td`
- [ ] In SPIRVInstructionSelector.cpp create the `DispatchMesh` lowering and map it to `int_spv_DispatchMesh` in `SPIRVInstructionSelector::selectIntrinsic`.
- [ ] Create SPIR-V backend test case in `llvm/test/CodeGen/SPIRV/hlsl-intrinsics/DispatchMesh.ll`
## DirectX
| DXIL Opcode | DXIL OpName | Shader Model | Shader Stages |
| ----------- | ----------- | ------------ | ------------- |
| 173 | DispatchMesh | 6.5 | ('amplification',) |
## SPIR-V
# [OpEmitMeshTasksEXT](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#OpEmitMeshTasksEXT):
## Description:
Reserved.
[Capability](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Capability):
**MeshShadingEXT**
[Reserved](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Unified).
<table style="width:100%;">
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<col style="width: 16%" />
<col style="width: 16%" />
<col style="width: 16%" />
<col style="width: 16%" />
<col style="width: 16%" />
<col style="width: 16%" />
</colgroup>
<thead>
<tr>
<th>Word Count</th>
<th>Opcode</th>
<th>Results</th>
<th>Operands</th>
<th></th>
<th></th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p>4 + variable</p></td>
<td class="tableblock halign-left valign-top"><p>5294</p></td>
<td
class="tableblock halign-left valign-top"><p><em><id></em><br />
<em>Group Count X</em></p></td>
<td
class="tableblock halign-left valign-top"><p><em><id></em><br />
<em>Group Count Y</em></p></td>
<td
class="tableblock halign-left valign-top"><p><em><id></em><br />
<em>Group Count Z</em></p></td>
<td class="tableblock halign-left valign-top"><p>Optional<br />
<em><id></em><br />
<em>Payload</em></p></td>
</tr>
</tbody>
</table>
## Test Case(s)
### Example 1
```hlsl
//dxc DispatchMesh_test.hlsl -T lib_6_8 -enable-16bit-types -O0
[numthreads(1, 1, 1)]
[shader("amplification")]
export void fn(uint gtid : SV_GroupIndex) {
struct RayPayload
{
float4 color;
float distance;
};
uint p1;
uint p2;
uint p3;
RayPayload p4;
DispatchMesh(p1, p2, p3, p4);
}
```
### SPIRV Example(s):
### Example 2
```hlsl
//dxc DispatchMesh_spirv_test.hlsl -T lib_6_8 -E fn -enable-16bit-types -spirv -fspv-target-env=universal1.5 -fcgl -O0
struct RayPayload
{
float4 color;
float distance;
};
groupshared RayPayload p4;
[numthreads(1, 1, 1)]
[shader("amplification")]
void fn(uint gtid : SV_GroupIndex) {
uint p1;
uint p2;
uint p3;
DispatchMesh(p1, p2, p3, p4);
}
```
## HLSL:
## Syntax
```syntax
void DispatchMesh(uint threadGroupCountX, uint threadGroupCountY, uint threadGroupCountZ, udt meshPayload);
```
## Type Description
| Name | [**Template Type**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/../direct3dhlsl/dx-graphics-hlsl-data-types.md)| [**Component Type**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/../direct3dhlsl/dx-graphics-hlsl-data-types.md) | Size |
|-------|--------------------------------------------------------------------|----------------------------------------------------------------------|------|
| *ret* | **void** | **void** | 0 |
| *threadGroupCountX* | [**scalar**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/../direct3dhlsl/dx-graphics-hlsl-scalar.md) | [**uint**](../WinProg/windows-data-types) | 1 |
| *threadGroupCountY* | [**scalar**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/../direct3dhlsl/dx-graphics-hlsl-scalar.md) | [**uint**](../WinProg/windows-data-types) | 1 |
| *threadGroupCountZ* | [**scalar**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/../direct3dhlsl/dx-graphics-hlsl-scalar.md) | [**uint**](../WinProg/windows-data-types) | 1 |
| *meshPayload* | [**RayPayload**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/../direct3d12/ray-payload.md) [**Struct**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/../direct3dhlsl/dx-graphics-hlsl-struct.md) | **RayPayload** | 1 |
## Minimum Shader Model
This function is supported in the following shader models.
|Shader Model | Supported|
|-------------|----------|
|[Shader Model 6.5](https://microsoft.github.io/DirectX-Specs/d3d/HLSL_ShaderModel6_5) and higher shader models | yes |
## Shader Stages
* [**Amplification Shader**](https://microsoft.github.io/DirectX-Specs/d3d/MeshShader.html#amplification-shader-and-mesh-shader)
## See also
- [**Intrinsic Functions (DirectX HLSL)**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/../direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md)
- **See [DispatchMesh - intrinsic](https://microsoft.github.io/DirectX-Specs/d3d/MeshShader.html#dispatchmesh-intrinsic)**
</pre>
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