microsoft / microsoft/DirectXShaderCompiler

Incorrect application of semantic interpolation modifiers

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bug needs-triage
Dominant language
C++
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Description

As highlighted in https://github.com/llvm/wg-hlsl/pull/432#discussion_r3422848837, DXC does not apply the modifiers in the same way as FXC and the documentation do.

This is likely an unintentional deviation from the expected behaviour and should be addressed as a bug.

Repro: https://godbolt.org/z/EzKG51W7E

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 Godbolt reproduction and the linked wg-hlsl discussion to identify how DXC differs from FXC and the documentation when applying semantic interpolation modifiers. Trace the relevant HLSL compiler behavior and verify the result against the reproduction. Done means DXC applies the modifiers consistently with the expected 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
Quiet
Clarity
Mostly clear
Newbie friendliness
52/100

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