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Execution Tests: Prevent sinking in long vector derivative hlk #8054

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alsepkow merged 2 commits into from
Jan 13, 2026
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Execution Tests: Prevent sinking in long vector derivative hlk #8054

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1673678
Prevent sinking in derivative hlk
alsepkow Jan 12, 2026
f800e6c
Use the return value of WaveReadLaneAt
alsepkow Jan 13, 2026
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4 changes: 4 additions & 0 deletions tools/clang/unittests/HLSLExec/ShaderOpArith.xml
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Expand Up @@ -4475,6 +4475,10 @@ void MSMain(uint GID : SV_GroupIndex,

vector<OUT_TYPE, NUM> Result = DERIVATIVE_FUNC(Vector);

// Prevents the above derivative call from being sunk into the if
// condition below. DXC Bug: https://github.com/microsoft/DirectXShaderCompiler/issues/8001
Result = WaveReadLaneAt(Result, 3);

// For coarse derivatives, all lanes in the quad get the same result.
// But for fine derivatives, each lane gets a different result. To
// keep things generic we only store in the third lane as thats the
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