[llvm] [DirectX] Start the creation of a DXIL Instruction legalizer (PR #131221)

[Deric C. via llvm-commits]

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+//===- DXILLegalizePass.h - Legalizes llvm IR for DXIL-*- C++------------*-===//
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Icohedron wrote:

```suggestion
//===- DXILLegalizePass.h - Legalizes llvm IR for DXIL --------------------===//
```

https://github.com/llvm/llvm-project/pull/131221