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

[Finn Plummer via llvm-commits]

================
@@ -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 {
----------------
inbelic wrote:

>From the front-end use case, there hasn't and I don't expect there to be a use-case of defining such helper functions. So I think adding it will add unneeded complexity.

If you are planning to re-use it for the back-end then we could maybe do that then?

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