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

[Justin Bogner via cfe-commits]

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@@ -99,6 +99,132 @@ 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 {
+  None = 0,
+  AllowInputAssemblerInputLayout = 0x1,
+  DenyVertexShaderRootAccess = 0x2,
+  DenyHullShaderRootAccess = 0x4,
+  DenyDomainShaderRootAccess = 0x8,
+  DenyGeometryShaderRootAccess = 0x10,
+  DenyPixelShaderRootAccess = 0x20,
+  AllowStreamOutput = 0x40,
+  LocalRootSignature = 0x80,
+  DenyAmplificationShaderRootAccess = 0x100,
+  DenyMeshShaderRootAccess = 0x200,
+  CBVSRVUAVHeapDirectlyIndexed = 0x400,
+  SamplerHeapDirectlyIndexed = 0x800,
+  ValidFlags = 0x00000fff
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bogner wrote:

I guess this is cribbed from DXC, but do we really want these "ValidFlags" entries in the enums? Who's going to use them? In general I feel like there are better ways to validate that whatever flags we get match what we expect/can handle, and adding extraneous values to enums makes things like `-Wcovered-switch` less effective.

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