| Issue |
184510
|
| Summary |
[Matrix] Implement matrix support for the `mad` HLSL Function
|
| Labels |
HLSL,
bot:HLSL
|
| Assignees |
|
| Reporter |
kmpeng
|
Matrix requirements:
- [ ] https://github.com/llvm/wg-hlsl/issues/387
## HLSL:
Performs an arithmetic multiply/add operation on three values.
## Syntax
``` syntax
numeric mad(
in numeric mvalue,
in numeric avalue,
in numeric bvalue
);
```
## Parameters
<dl> <dt>
*mvalue* \[in\]
</dt> <dd>
Type: **numeric**
The multiplication value.
</dd> <dt>
*avalue* \[in\]
</dt> <dd>
Type: **numeric**
The first addition value.
</dd> <dt>
*bvalue* \[in\]
</dt> <dd>
Type: **numeric**
The second addition value.
</dd> </dl>
## Return value
Type: **numeric**
The result of *mvalue* \* *avalue* + *bvalue*.
## Remarks
### Minimum Shader Model
This function is supported in the following shader models.
This function is supported in the following types of shaders:
| Vertex | Hull | Domain | Geometry | Pixel | Compute |
|--------|------|--------|----------|-------|---------|
| x | x | x | x | x | x |
Shader authors can use the **mad** instrinsic to explicitly target the **mad** hardware instruction in the compiled shader output, which is particularly useful with shaders that mark results with the [precise](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/direct3dhlsl/dx-graphics-hlsl-appendix-keywords.md) keyword. The **mad** instruction can be implemented in hardware as either "fused," which offers higher precision than implementing a **mul** instruction followed by an **add** instruction, or as a **mul** + **add**.
If shader authors use the **mad** instrinsic to calculate a result that the shader marked as precise, they indicate to the hardware to use any valid implementation of the **mad** instruction (fused or not) as long as the implementation is consistent for all uses of that **mad** intrinsic in any shader on that hardware. Shaders can then take advantage of potential performance improvements by using a native **mad** instruction (versus **mul** + **add**) on some hardware. The result of performing a native **mad** hardware instruction might or might not be different than performing a **mul** followed by an **add**. However, whatever the result is, the result must be consistent for the same operation to occur in multiple shaders or different parts of a shader.
## See also
<dl> <dt>
[Intrinsic Functions](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/direct3dhlsl/dx-graphics-hlsl-intrinsic-functions.md)
</dt> <dt>
[Shader Model 5](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/direct3dhlsl/d3d11-graphics-reference-sm5.md)
</dt> </dl>
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