<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/99133>99133</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
Implement the `ldexp` 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 `ldexp` clang builtin,
- [ ] Link `ldexp` clang builtin with `hlsl_intrinsics.h`
- [ ] Add sema checks for `ldexp` to `CheckHLSLBuiltinFunctionCall` in `SemaChecking.cpp`
- [ ] Add codegen for `ldexp` to `EmitHLSLBuiltinExpr` in `CGBuiltin.cpp`
- [ ] Add codegen tests to `clang/test/CodeGenHLSL/builtins/ldexp.hlsl`
- [ ] Add sema tests to `clang/test/SemaHLSL/BuiltIns/ldexp-errors.hlsl`
- [ ] Create the `int_dx_ldexp` intrinsic in `IntrinsicsDirectX.td`
- [ ] Create the `DXILOpMapping` of `int_dx_ldexp` to `21` in `DXIL.td`
- [ ] Create the `ldexp.ll` and `ldexp_errors.ll` tests in `llvm/test/CodeGen/DirectX/`
- [ ] Create the `int_spv_ldexp` intrinsic in `IntrinsicsSPIRV.td`
- [ ] In SPIRVInstructionSelector.cpp create the `ldexp` lowering and map it to `int_spv_ldexp` in `SPIRVInstructionSelector::selectIntrinsic`.
- [ ] Create SPIR-V backend test case in `llvm/test/CodeGen/SPIRV/hlsl-intrinsics/ldexp.ll`
## DirectX
| DXIL Opcode | DXIL OpName | Shader Model | Shader Stages |
| ----------- | ----------- | ------------ | ------------- |
| 21 | Exp | 6.0 | () |
## SPIR-V
# Exp2:
## Description:
**Exp2**
Result is 2 raised to the *x* power; 2<sup>*x*</sup>.
The operand *x* must be a scalar or vector whose component type is
16-bit or 32-bit floating-point.
*Result Type* and the type of *x* must be the same type. Results are
computed per component.
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<td class="tableblock halign-left valign-top"><p>29</p></td>
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## Test Case(s)
### Example 1
```hlsl
//dxc ldexp_test.hlsl -T lib_6_8 -enable-16bit-types -O0
export float4 fn(float4 p1, float4 p2) {
return ldexp(p1, p2);
}
```
## HLSL:
Returns the result of multiplying the specified value by two, raised to the power of the specified exponent.
| *ret* ldexp(*x*, *exp*) |
|-------------------------|
This function uses the following formula: *x* \* 2<sup>exp</sup>
## Parameters
| Item | Description |
|--------------------------------------------------------------|-------------------------------------------|
| <span id="x"></span><span id="X"></span>*x*<br/> | \[in\] The specified value.<br/> |
| <span id="exp"></span><span id="EXP"></span>*exp*<br/> | \[in\] The specified exponent.<br/> |
## Return Value
The result of multiplying the *x* parameter by two, raised to the power of the *exp* parameter.
## 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 |
| *exp* | 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) |
## Requirements
| Requirement | Value |
|-------------------|--------------------------------------------------------------------------------------------|
| Header<br/> | <dl> <dt>Corecrt\_math.h</dt> </dl> |
## 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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