[clang] [llvm] [NFC][HLSL][DXIL] Move D3D12.h enums and flags to DXILABI (PR #143041)

[Finn Plummer via llvm-commits]

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@@ -99,6 +99,128 @@ enum class SamplerFeedbackType : uint32_t {
 const unsigned MinWaveSize = 4;
 const unsigned MaxWaveSize = 128;
 
+// Definition of the various d3d12.h enumerations and flags. The definitions of
+// all values here correspond to their description in the d3d12.h header and
+// are carried over from their values in DXC. For reference:
+// https://learn.microsoft.com/en-us/windows/win32/api/d3d12/
+
+// D3D12_ROOT_SIGNATURE_FLAGS
+enum class RootFlags : uint32_t {
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inbelic wrote:

>From offline: we will re-address this when the use-case is immediately visible (when re-using in backend-end)

https://github.com/llvm/llvm-project/pull/143041