<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/99175>99175</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
Implement the `QuadReadAcrossX` 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 `QuadReadAcrossX` clang builtin,
- [ ] Link `QuadReadAcrossX` clang builtin with `hlsl_intrinsics.h`
- [ ] Add sema checks for `QuadReadAcrossX` to `CheckHLSLBuiltinFunctionCall` in `SemaChecking.cpp`
- [ ] Add codegen for `QuadReadAcrossX` to `EmitHLSLBuiltinExpr` in `CGBuiltin.cpp`
- [ ] Add codegen tests to `clang/test/CodeGenHLSL/builtins/QuadReadAcrossX.hlsl`
- [ ] Add sema tests to `clang/test/SemaHLSL/BuiltIns/QuadReadAcrossX-errors.hlsl`
- [ ] Create the `int_dx_QuadReadAcrossX` intrinsic in `IntrinsicsDirectX.td`
- [ ] Create the `DXILOpMapping` of `int_dx_QuadReadAcrossX` to `123` in `DXIL.td`
- [ ] Create the `QuadReadAcrossX.ll` and `QuadReadAcrossX_errors.ll` tests in `llvm/test/CodeGen/DirectX/`
- [ ] Create the `int_spv_QuadReadAcrossX` intrinsic in `IntrinsicsSPIRV.td`
- [ ] In SPIRVInstructionSelector.cpp create the `QuadReadAcrossX` lowering and map it to `int_spv_QuadReadAcrossX` in `SPIRVInstructionSelector::selectIntrinsic`.
- [ ] Create SPIR-V backend test case in `llvm/test/CodeGen/SPIRV/hlsl-intrinsics/QuadReadAcrossX.ll`
## DirectX
| DXIL Opcode | DXIL OpName | Shader Model | Shader Stages |
| ----------- | ----------- | ------------ | ------------- |
| 123 | QuadOp | 6.0 | ('library', 'compute', 'amplification', 'mesh', 'pixel', 'node') |
## SPIR-V
# [OpGroupNonUniformQuadSwap](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#OpGroupNonUniformQuadSwap):
## Description:
Swap the *Value* of the [invocation](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Invocation) within the
[quad](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Quad) with another invocation in the quad using *Direction*.
*Result Type* must be a scalar or vector of [*floating-point
type*](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Floating), [*integer type*](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Integer), or [*Boolean
type*](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Boolean).
*Execution* is a [*Scope*](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Scope_-id-), but has no effect on the
behavior of this instruction. It must be **Subgroup**.
The type of *Value* must be the same as *Result Type*.
*Direction* is the kind of swap to perform.
*Direction* must be a scalar of [*integer type*](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Integer), whose
*Signedness* operand is 0.
*Direction* must come from a [*constant
instruction*](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#ConstantInstruction).
The value returned in *Result* is the value provided to *Value* by
another invocation in the same quad scope instance. The invocation
providing this value is determined according to *Direction*.
A *Direction* of 0 indicates a horizontal swap;
- Invocations with [quad indices](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#QuadIndex) of 0 and 1 swap values
- Invocations with [quad indices](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#QuadIndex) of 2 and 3 swap values
A *Direction* of 1 indicates a vertical swap;
- Invocations with [quad indices](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#QuadIndex) of 0 and 2 swap values
- Invocations with [quad indices](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#QuadIndex) of 1 and 3 swap values
A *Direction* of 2 indicates a diagonal swap;
- Invocations with [quad indices](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#QuadIndex) of 0 and 3 swap values
- Invocations with [quad indices](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#QuadIndex) of 1 and 2 swap values
*Direction* must be one of the above values.
If an active invocation reads *Value* from an inactive invocation, the
resulting value is undefined.
[Capability](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Capability):
**GroupNonUniformQuad**
[Missing before](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#Unified) **version 1.3**.
<table style="width:100%;">
<colgroup>
<col style="width: 14%" />
<col style="width: 14%" />
<col style="width: 14%" />
<col style="width: 14%" />
<col style="width: 14%" />
<col style="width: 14%" />
<col style="width: 14%" />
</colgroup>
<thead>
<tr>
<th>Word Count</th>
<th>Opcode</th>
<th>Results</th>
<th>Operands</th>
<th></th>
<th></th>
<th></th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p>6</p></td>
<td class="tableblock halign-left valign-top"><p>366</p></td>
<td
class="tableblock halign-left valign-top"><p><em><id></em><br />
<em>Result Type</em></p></td>
<td class="tableblock halign-left valign-top"><p><a
href="#ResultId"><em>Result <id></em></a></p></td>
<td class="tableblock halign-left valign-top"><p><a
href="#Scope_-id-"><em>Scope <id></em></a><br />
<em>Execution</em></p></td>
<td
class="tableblock halign-left valign-top"><p><em><id></em><br />
<em>Value</em></p></td>
<td
class="tableblock halign-left valign-top"><p><em><id></em><br />
<em>Direction</em></p></td>
</tr>
</tbody>
</table>
## Test Case(s)
### Example 1
```hlsl
//dxc QuadReadAcrossX_test.hlsl -T lib_6_8 -enable-16bit-types -O0
export float4 fn(float4 p1) {
return QuadReadAcrossX(p1);
}
```
### Example 2
```hlsl
//dxc QuadReadAcrossX_1_test.hlsl -T lib_6_8 -enable-16bit-types -O0
export uint4 fn(uint4 p1) {
return QuadReadAcrossX(p1);
}
```
### Example 3
```hlsl
//dxc QuadReadAcrossX_2_test.hlsl -T lib_6_8 -enable-16bit-types -O0
export int4 fn(int4 p1) {
return QuadReadAcrossX(p1);
}
```
## HLSL:
Returns the specified local value read from the other lane in this quad in the X direction.
## Syntax
``` syntax
<type> QuadReadAcrossX(
<type> localValue
);
```
## Parameters
<dl> <dt>
*localValue*
</dt> <dd>
The requested type.
</dd> </dl>
## Return value
The specified local value. If the source lane is inactive, the results are undefined.
## Remarks
For more information on quads, refer to [Overview of Shader Model 6](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/hlsl-shader-model-6-0-features-for-direct3d-12.md).
This function is supported from shader model 6.0 only in pixel and compute shaders.
## See also
<dl> <dt>
[Shader Model 6](https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src//direct3dhlsl/shader-model-6-0.md)
</dt> </dl>
</pre>
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