microsoft / microsoft/DirectXShaderCompiler

Rewriter incorrectly removes types that are used in a member array of another struct

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

In the following example MultipleChildren being an array causes Child type to be be stripped by the rewriter when using -remove-unused-globals

// dxr -E InitArgs -remove-unused-globals test.hlsl
struct Child {
	uint Test;
};

struct Parent {
	Child MultipleChildren[2];
};

RWStructuredBuffer<Parent> ParentBuffer;

[numthreads(1, 1, 1)]
void InitArgs()
{
	ParentBuffer[0] = (Parent)0;
}

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 by reproducing the issue with dxr -E InitArgs -remove-unused-globals test.hlsl using the HLSL example in the report. Trace the rewriter's handling of Child when it is referenced through Parent's member array; done means Child is retained while removing unused globals and the reproducer passes.

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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