diff --git a/include/dxc/HLSL/DxilRootSignature.h b/include/dxc/HLSL/DxilRootSignature.h
index d984e059e..a2ff5f7f3 100644
--- a/include/dxc/HLSL/DxilRootSignature.h
+++ b/include/dxc/HLSL/DxilRootSignature.h
@@ -346,16 +346,16 @@ void SerializeRootSignature(const DxilVersionedRootSignatureDesc *pRootSignature
                             _Outptr_ IDxcBlob **ppBlob, _Outptr_ IDxcBlobEncoding **ppErrorBlob,
                             bool bAllowReservedRegisterSpace);
 
-void DeserializeRootSignature(__in_bcount(SrcDataSizeInBytes) const void *pSrcData,
-                              __in uint32_t SrcDataSizeInBytes,
-                              __out const DxilVersionedRootSignatureDesc **ppRootSignature);
+void DeserializeRootSignature(_In_reads_bytes_(SrcDataSizeInBytes) const void *pSrcData,
+                              _In_ uint32_t SrcDataSizeInBytes,
+                              _Out_ const DxilVersionedRootSignatureDesc **ppRootSignature);
 
 // Takes PSV - pipeline state validation data, not shader container.
-bool VerifyRootSignatureWithShaderPSV(__in const DxilVersionedRootSignatureDesc *pDesc,
-                                      __in DXIL::ShaderKind ShaderKind,
+bool VerifyRootSignatureWithShaderPSV(_In_ const DxilVersionedRootSignatureDesc *pDesc,
+                                      _In_ DXIL::ShaderKind ShaderKind,
                                       _In_reads_bytes_(PSVSize) const void *pPSVData,
-                                      __in uint32_t PSVSize,
-                                      __in llvm::raw_ostream &DiagStream);
+                                      _In_ uint32_t PSVSize,
+                                      _In_ llvm::raw_ostream &DiagStream);
 
 } // namespace hlsl
 
diff --git a/lib/HLSL/DxilContainerReflection.cpp b/lib/HLSL/DxilContainerReflection.cpp
index e0222ce8b..ccef479d1 100644
--- a/lib/HLSL/DxilContainerReflection.cpp
+++ b/lib/HLSL/DxilContainerReflection.cpp
@@ -302,7 +302,7 @@ public:
   STDMETHOD(IsOfType)(THIS_ ID3D12ShaderReflectionType* pType);
   STDMETHOD(ImplementsInterface)(THIS_ ID3D12ShaderReflectionType* pBase);
 
-  bool CheckEqual(__in CShaderReflectionType *pOther) {
+  bool CheckEqual(_In_ CShaderReflectionType *pOther) {
     return m_Identity == pOther->m_Identity;
   }
 };
diff --git a/lib/HLSL/DxilRootSignature.cpp b/lib/HLSL/DxilRootSignature.cpp
index 08535fe45..efa766207 100644
--- a/lib/HLSL/DxilRootSignature.cpp
+++ b/lib/HLSL/DxilRootSignature.cpp
@@ -117,7 +117,7 @@ public:
   HRESULT AddBlock(void *pData, unsigned cbSize, unsigned *pOffset);
   HRESULT ReserveBlock(void **ppData, unsigned cbSize, unsigned *pOffset);
 
-  HRESULT Compact(__out_bcount(cbSize) char *pData, unsigned cbSize);
+  HRESULT Compact(_Out_writes_bytes_(cbSize) char *pData, unsigned cbSize);
   unsigned GetSize();
 
 protected:
@@ -205,7 +205,7 @@ Cleanup:
   return hr;
 }
 
-HRESULT SimpleSerializer::Compact(__out_bcount(cbSize) char *pData,
+HRESULT SimpleSerializer::Compact(_Out_writes_bytes_(cbSize) char *pData,
                                   unsigned cbSize) {
   unsigned cb = GetSize();
   IFRBOOL(cb <= cbSize, E_FAIL);
@@ -1264,11 +1264,11 @@ template<typename T_ROOT_SIGNATURE_DESC,
   typename T_ROOT_PARAMETER,
   typename T_ROOT_DESCRIPTOR_INTERNAL,
   typename T_DESCRIPTOR_RANGE_INTERNAL>
-void SerializeRootSignatureTemplate(__in const T_ROOT_SIGNATURE_DESC* pRootSignature,
+void SerializeRootSignatureTemplate(_In_ const T_ROOT_SIGNATURE_DESC* pRootSignature,
                                     DxilRootSignatureVersion DescVersion,
                                     _COM_Outptr_ IDxcBlob** ppBlob,
                                     DiagnosticPrinter &DiagPrinter,
-                                    __in bool bAllowReservedRegisterSpace) {
+                                    _In_ bool bAllowReservedRegisterSpace) {
   DxilContainerRootSignatureDesc RS;
   uint32_t Offset;
   SimpleSerializer Serializer;
@@ -1423,8 +1423,8 @@ public:
   CVersionedRootSignatureDeserializer();
   ~CVersionedRootSignatureDeserializer();
 
-  void Initialize(__in_bcount(SrcDataSizeInBytes) const void *pSrcData,
-                  __in uint32_t SrcDataSizeInBytes);
+  void Initialize(_In_reads_bytes_(SrcDataSizeInBytes) const void *pSrcData,
+                  _In_ uint32_t SrcDataSizeInBytes);
 
   const DxilVersionedRootSignatureDesc *GetRootSignatureDescAtVersion(DxilRootSignatureVersion convertToVersion);
 
@@ -1442,8 +1442,8 @@ CVersionedRootSignatureDeserializer::~CVersionedRootSignatureDeserializer() {
   DeleteRootSignature(m_pRootSignature11);
 }
 
-void CVersionedRootSignatureDeserializer::Initialize(__in_bcount(SrcDataSizeInBytes) const void *pSrcData,
-                                                     __in uint32_t SrcDataSizeInBytes) {
+void CVersionedRootSignatureDeserializer::Initialize(_In_reads_bytes_(SrcDataSizeInBytes) const void *pSrcData,
+                                                     _In_ uint32_t SrcDataSizeInBytes) {
   const DxilVersionedRootSignatureDesc *pRootSignature = nullptr;
   DeserializeRootSignature(pSrcData, SrcDataSizeInBytes, &pRootSignature);
 
@@ -1501,8 +1501,8 @@ template<typename T_ROOT_SIGNATURE_DESC,
          typename T_ROOT_DESCRIPTOR_INTERNAL,
          typename T_DESCRIPTOR_RANGE,
          typename T_DESCRIPTOR_RANGE_INTERNAL>
-void DeserializeRootSignatureTemplate(__in_bcount(SrcDataSizeInBytes) const void *pSrcData,
-                                      __in uint32_t SrcDataSizeInBytes,
+void DeserializeRootSignatureTemplate(_In_reads_bytes_(SrcDataSizeInBytes) const void *pSrcData,
+                                      _In_ uint32_t SrcDataSizeInBytes,
                                       DxilRootSignatureVersion DescVersion,
                                       T_ROOT_SIGNATURE_DESC &RootSignatureDesc) {
   // Note that in case of failure, outside code must deallocate memory.
diff --git a/tools/clang/lib/Sema/SemaHLSL.cpp b/tools/clang/lib/Sema/SemaHLSL.cpp
index 3a9664dba..167b9a95e 100644
--- a/tools/clang/lib/Sema/SemaHLSL.cpp
+++ b/tools/clang/lib/Sema/SemaHLSL.cpp
@@ -4428,7 +4428,7 @@ FunctionDecl* HLSLExternalSource::AddSubscriptSpecialization(
 /// and want to treat either side equally you should call it twice, swapping the
 /// parameter order.
 /// </summary>
-static bool CombineObjectTypes(ArBasicKind Target, __in ArBasicKind Source,
+static bool CombineObjectTypes(ArBasicKind Target, _In_ ArBasicKind Source,
                                _Out_opt_ ArBasicKind *pCombined) {
   if (Target == Source) {
     AssignOpt(Target, pCombined);