diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index d3f3162..34bb07c 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -1451,6 +1451,12 @@
 
   // Builtin type used to help define __builtin_va_list.
   VaListTagDecl = nullptr;
+
+  // MSVC predeclares struct _GUID, and we need it to create MSGuidDecls.
+  if (LangOpts.MicrosoftExt || LangOpts.Borland) {
+    MSGuidTagDecl = buildImplicitRecord("_GUID");
+    TUDecl->addDecl(MSGuidTagDecl);
+  }
 }
 
 DiagnosticsEngine &ASTContext::getDiagnostics() const {
@@ -10580,6 +10586,23 @@
   return Result;
 }
 
+MSGuidDecl *
+ASTContext::getMSGuidDecl(MSGuidDecl::Parts Parts) const {
+  assert(MSGuidTagDecl && "building MS GUID without MS extensions?");
+
+  llvm::FoldingSetNodeID ID;
+  MSGuidDecl::Profile(ID, Parts);
+
+  void *InsertPos;
+  if (MSGuidDecl *Existing = MSGuidDecls.FindNodeOrInsertPos(ID, InsertPos))
+    return Existing;
+
+  QualType GUIDType = getMSGuidType().withConst();
+  MSGuidDecl *New = MSGuidDecl::Create(*this, GUIDType, Parts);
+  MSGuidDecls.InsertNode(New, InsertPos);
+  return New;
+}
+
 bool ASTContext::AtomicUsesUnsupportedLibcall(const AtomicExpr *E) const {
   const llvm::Triple &T = getTargetInfo().getTriple();
   if (!T.isOSDarwin())