<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/99156>99156</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
Implement the `smoothstep` 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 `smoothstep` clang builtin,
- [ ] Link `smoothstep` clang builtin with `hlsl_intrinsics.h`
- [ ] Add sema checks for `smoothstep` to `CheckHLSLBuiltinFunctionCall` in `SemaChecking.cpp`
- [ ] Add codegen for `smoothstep` to `EmitHLSLBuiltinExpr` in `CGBuiltin.cpp`
- [ ] Add codegen tests to `clang/test/CodeGenHLSL/builtins/smoothstep.hlsl`
- [ ] Add sema tests to `clang/test/SemaHLSL/BuiltIns/smoothstep-errors.hlsl`
- [ ] Create the `int_dx_smoothstep` intrinsic in `IntrinsicsDirectX.td`
- [ ] Create the `DXILOpMapping` of `int_dx_smoothstep` to `7` in `DXIL.td`
- [ ] Create the `smoothstep.ll` and `smoothstep_errors.ll` tests in `llvm/test/CodeGen/DirectX/`
- [ ] Create the `int_spv_smoothstep` intrinsic in `IntrinsicsSPIRV.td`
- [ ] In SPIRVInstructionSelector.cpp create the `smoothstep` lowering and map it to `int_spv_smoothstep` in `SPIRVInstructionSelector::selectIntrinsic`.
- [ ] Create SPIR-V backend test case in `llvm/test/CodeGen/SPIRV/hlsl-intrinsics/smoothstep.ll`
## DirectX
| DXIL Opcode | DXIL OpName | Shader Model | Shader Stages |
| ----------- | ----------- | ------------ | ------------- |
| 7 | Saturate | 6.0 | () |
## SPIR-V
# SmoothStep:
## Description:
**SmoothStep**
Result is 0.0 if *x* ≤ *edge0* and 1.0 if *x* ≥ *edge1* and performs
smooth Hermite interpolation between 0 and 1 when *edge0* \< *x* \<
*edge1*. This is equivalent to:
*t* \* *t* \* (3 - 2 \* *t*), where *t* = clamp ((*x* - *edge0*) /
(*edge1* - *edge0*), 0, 1)
Result is undefined if *edge0* ≥ *edge1*.
The operands must all be a scalar or vector whose component type is
floating-point.
*Result Type* and the type of all operands must be the same type.
Results are computed per component.
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<th>Number</th>
<th>Operand 1</th>
<th>Operand 2</th>
<th>Operand 3</th>
<th>Operand 4</th>
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</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p>49</p></td>
<td
class="tableblock halign-left valign-top"><p><em><id></em><br />
<em>edge0</em></p></td>
<td
class="tableblock halign-left valign-top"><p><em><id></em><br />
<em>edge1</em></p></td>
<td
class="tableblock halign-left valign-top"><p><em><id></em><br />
<em>x</em></p></td>
<td></td>
</tr>
</tbody>
</table>
## Test Case(s)
### Example 1
```hlsl
//dxc smoothstep_test.hlsl -T lib_6_8 -enable-16bit-types -O0
export float4 fn(float4 p1, float4 p2, float4 p3) {
return smoothstep(p1, p2, p3);
}
```
## HLSL:
Returns a smooth Hermite interpolation between 0 and 1, if *x* is in the range \[*min*, *max*\].
| *ret* smoothstep(*min*, *max*, *x*) |
|-------------------------------------|
## Parameters
| Item | Description |
|--------------------------------------------------------------|-----------------------------------------------------------|
| <span id="min"></span><span id="MIN"></span>*min*<br/> | \[in\] The minimum range of the *x* parameter.<br/> |
| <span id="max"></span><span id="MAX"></span>*max*<br/> | \[in\] The maximum range of the *x* parameter.<br/> |
| <span id="x"></span><span id="X"></span>*x*<br/> | \[in\] The specified value to be interpolated.<br/> |
## Return Value
Returns 0 if *x* is less than *min*; 1 if *x* is greater than *max*; otherwise, a value between 0 and 1 if *x* is in the range \[*min*, *max*\].
## Remarks
Use the **smoothstep** HLSL intrinsic function to create a smooth transition between two values. For example, you can use this function to blend two colors smoothly.
## Type Description
| Name | [**Template Type**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md) | [**Component Type**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md) | Size |
|-------|----------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------|--------------------------------|
| *x* | [**scalar**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md), **vector**, or **matrix** | [**float**](/windows/desktop/WinProg/windows-data-types) | any |
| *min* | same as input *x* | [**float**](/windows/desktop/WinProg/windows-data-types) | same dimension(s) as input *x* |
| *max* | same as input *x* | [**float**](/windows/desktop/WinProg/windows-data-types) | same dimension(s) as input *x* |
| *ret* | same as input *x* | [**float**](/windows/desktop/WinProg/windows-data-types) | same dimension(s) as input *x* |
## Minimum Shader Model
This function is supported in the following shader models.
| Shader Model | Supported |
|------------------------------------------------------------------------------------|---------------------|
| [Shader Model 2 (DirectX HLSL)](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-sm2.md) and higher shader models | yes |
| [Shader Model 1 (DirectX HLSL)](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-sm1.md) | yes (vs\_1\_1 only) |
## See also
<dl> <dt>
[**Intrinsic Functions (DirectX HLSL)**](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md)
</dt> </dl>
</pre>
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