microsoft / microsoft/DirectXShaderCompiler

Amplification shader: support for empty payload

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bug
Dominant language
C++
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Merged PRs (30d)
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Description

Currently DXIL generates invalid byte-code, if playload structure is empty:
https://shader-playground.timjones.io/2af967f58c70b528724326a00b414c30

Resulting in validation error:

For amplification shader with entry 'main', payload size 4 is greater than declared size of 0 bytes.

Empty (or rather absence of it) payload is allowed in Vulkan
This issue complicated cross-compilation from Vulkan, for cross-api engine.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked Shader Playground reproducer and the reported DXIL validation error for an amplification shader with an empty payload. Trace the compiler output for that case and verify that the resulting bytecode accepts an absent payload while preserving valid payload behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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