[SPIR-V] Fix usage of indices in subfunctions#7242
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Keenuts merged 3 commits intomicrosoft:mainfrom Mar 27, 2025
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The parameters tagged with indices are linked to a builtin. Because their layout is different between HLSL and SPIR-V, there is a common mechanism to handle those 'stage I/O variables'. Usually, a local variable with the correct HLSL layout is created, and when required, the value is copied in and copied out in the entrypoint wrapper. Then, a function-scoped pointer is passed to sub-functions. The issue is that `indices` marks an array which is also shared across invocations. Meaning we cannot simple copy-in/copy-out. We are only allowed to write to the indices touched by the shader. This required pushing the handling to the assignment expression handling: when a value is assigned to such builtin, the layout transformation is done, and the builtin written to. Issue was how to find back the Builtin from an assignment: the code assumed the ParmDecl of the entrypoint was the only way to access this variable, but nothing prevents the user to pass this indice array to another function. The simple solution is to move this out of the generic map, and have a new field which stored the SpirvVariable we created, and allow any HLSL function to access this as soon as the HLSLIndices attribute is found. Signed-off-by: Nathan Gauër <[email protected]>
cassiebeckley
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Mar 24, 2025
s-perron
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Mar 25, 2025
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s-perron
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LGTM just needs a little clean up.
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The parameters tagged with indices are linked to a builtin. Because their layout is different between HLSL and SPIR-V, there is a common mechanism to handle those 'stage I/O variables'.
Usually, a local variable with the correct HLSL layout is created, and when required, the value is copied in and copied out in the entrypoint wrapper. Then, a function-scoped pointer is passed to sub-functions.
The issue is that
indicesmarks an array which is also shared across invocations. Meaning we cannot simple copy-in/copy-out. We are only allowed to write to the indices touched by the shader.This required pushing the handling to the assignment expression handling: when a value is assigned to such builtin, the layout transformation is done, and the builtin written to.
Issue was how to find back the Builtin from an assignment: the code assumed the ParmDecl of the entrypoint was the only way to access this variable, but nothing prevents the user to pass this indice array to another function.
The simple solution is to move this out of the generic map, and have a new field which stored the SpirvVariable we created, and allow any HLSL function to access this as soon as the HLSLIndices attribute is found.
Fixes #7009