[HLSL][DirectX] update verifyRootDescriptorFlag to match the spec

Author: inbelic

llvm/include/llvm/Frontend/HLSL/RootSignatureValidations.h

@@ -27,7 +27,7 @@ bool verifyRootFlag(uint32_t Flags);
 bool verifyVersion(uint32_t Version);
 bool verifyRegisterValue(uint32_t RegisterValue);
 bool verifyRegisterSpace(uint32_t RegisterSpace);
-bool verifyDescriptorFlag(uint32_t Flags);
+bool verifyRootDescriptorFlag(uint32_t Version, uint32_t FlagsVal);
 bool verifyRangeType(uint32_t Type);
 bool verifyDescriptorRangeFlag(uint32_t Version, uint32_t Type,
                                uint32_t FlagsVal);

llvm/lib/Frontend/HLSL/RootSignatureValidations.cpp

@@ -32,7 +32,24 @@ bool verifyRegisterSpace(uint32_t RegisterSpace) {
   return !(RegisterSpace >= 0xFFFFFFF0 && RegisterSpace <= 0xFFFFFFFF);
 }
 
-bool verifyDescriptorFlag(uint32_t Flags) { return (Flags & ~0xE) == 0; }
+bool verifyRootDescriptorFlag(uint32_t Version, uint32_t FlagsVal) {
+  using FlagT = dxbc::RootDescriptorFlags;
+  FlagT Flags = FlagT(FlagsVal);
+  if (Version == 1)
+    return FlagsVal == FlagT::DataVolatile;
+
+  assert(Version == 2 && "Provided invalid root signature version");
+
+  // The data-specific flags are mutually exclusive.
+  FlagT DataFlags = FlagT::DataVolatile | FlagT::DataStatic |
+                    FlagT::DataStaticWhileSetAtExecute;
+
+  if (popcount(llvm::to_underlying(Flags & DataFlags)) > 1)
+    return false;
+
+  // Only a data flag or no flags is valid
+  return (FlagsVal & ~0xE) == 0;
+}
 
 bool verifyRangeType(uint32_t Type) {
   switch (Type) {

llvm/lib/Target/DirectX/DXILRootSignature.cpp

@@ -432,7 +432,8 @@ static bool validate(LLVMContext *Ctx, const mcdxbc::RootSignatureDesc &RSD) {
         return reportValueError(Ctx, "RegisterSpace", Descriptor.RegisterSpace);
 
       if (RSD.Version > 1) {
-        if (!llvm::hlsl::rootsig::verifyDescriptorFlag(Descriptor.Flags))
+        if (!llvm::hlsl::rootsig::verifyRootDescriptorFlag(RSD.Version,
+                                                           Descriptor.Flags))
           return reportValueError(Ctx, "DescriptorRangeFlag", Descriptor.Flags);
       }
       break;