Execution Tests: Prevent sinking in long vector derivative hlk #8054
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tex3d
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Jan 13, 2026
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Though the result of the wave op is unused, it appears that it still prevents ddx from being moved, and the compiler doesn't know it can remove the wave op, so as a workaround, that should be ok for now. It just might be more fragile if the compiler could DCE the wave op in the future, which would be legal.
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I went ahead and updated so we use the result.
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From: Tex Riddell ***@***.***>
Sent: Monday, January 12, 2026 4:06 PM
To: microsoft/DirectXShaderCompiler ***@***.***>
Cc: Alex Sepkowski ***@***.***>; Author ***@***.***>
Subject: Re: [microsoft/DirectXShaderCompiler] Execution Tests: Prevent sinking in long vector derivative hlk (PR #8054)
@tex3d approved this pull request.
Though the result of the wave op is unused, it appears that it still prevents ddx from being moved, and the compiler doesn't know it can remove the wave op, so as a workaround, that should be ok for now. It just might be more fragile if the compiler could DCE the wave op in the future, which would be legal.
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V-FEXrt
approved these changes
Jan 13, 2026
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This PR adds a workaround to the hlk long vector derivative tests to prevent sinking of the derivative call into the conditional. This is a known bug in DXC that will not be fixed for 6.9 release.
DXC bug tracked via issue #8001