diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -185,12 +185,16 @@
       (R.getVersion() >= VersionTuple(major, minor));
   }
 
+  StringRef SymbolPrefix() {
+    return CGM.getTriple().isOSBinFormatCOFF() ? "_" : "._";
+  }
+
   std::string SymbolForProtocol(StringRef Name) {
-    return (StringRef("._OBJC_PROTOCOL_") + Name).str();
+    return (SymbolPrefix() + "OBJC_PROTOCOL_" + Name).str();
   }
 
   std::string SymbolForProtocolRef(StringRef Name) {
-    return (StringRef("._OBJC_REF_PROTOCOL_") + Name).str();
+    return (SymbolPrefix() + "OBJC_REF_PROTOCOL_" + Name).str();
   }
 
 
@@ -906,12 +910,15 @@
     ConstantStringSection
   };
   static const char *const SectionsBaseNames[8];
+  static const char *const PECOFFSectionsBaseNames[8];
   template<SectionKind K>
   std::string sectionName() {
-    std::string name(SectionsBaseNames[K]);
-    if (CGM.getTriple().isOSBinFormatCOFF())
+    if (CGM.getTriple().isOSBinFormatCOFF()) {
+      std::string name(PECOFFSectionsBaseNames[K]);
       name += "$m";
-    return name;
+      return name;
+    }
+    return SectionsBaseNames[K];
   }
   /// The GCC ABI superclass message lookup function.  Takes a pointer to a
   /// structure describing the receiver and the class, and a selector as
@@ -932,15 +939,19 @@
   bool EmittedClass = false;
   /// Generate the name of a symbol for a reference to a class.  Accesses to
   /// classes should be indirected via this.
+
+  typedef std::pair<std::string, std::pair<llvm::Constant*, int>> EarlyInitPair;
+  std::vector<EarlyInitPair> EarlyInitList;
+
   std::string SymbolForClassRef(StringRef Name, bool isWeak) {
     if (isWeak)
-      return (StringRef("._OBJC_WEAK_REF_CLASS_") + Name).str();
+      return (SymbolPrefix() + "OBJC_WEAK_REF_CLASS_" + Name).str();
     else
-      return (StringRef("._OBJC_REF_CLASS_") + Name).str();
+      return (SymbolPrefix() + "OBJC_REF_CLASS_" + Name).str();
   }
   /// Generate the name of a class symbol.
   std::string SymbolForClass(StringRef Name) {
-    return (StringRef("._OBJC_CLASS_") + Name).str();
+    return (SymbolPrefix() + "OBJC_CLASS_" + Name).str();
   }
   void CallRuntimeFunction(CGBuilderTy &B, StringRef FunctionName,
       ArrayRef<llvm::Value*> Args) {
@@ -994,10 +1005,13 @@
 
     llvm::Constant *isa = TheModule.getNamedGlobal(Sym);
 
-    if (!isa)
+    if (!isa) {
       isa = new llvm::GlobalVariable(TheModule, IdTy, /* isConstant */false,
               llvm::GlobalValue::ExternalLinkage, nullptr, Sym);
-    else if (isa->getType() != PtrToIdTy)
+      if (CGM.getTriple().isOSBinFormatCOFF()) {
+        cast<llvm::GlobalValue>(isa)->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
+      }
+    } else if (isa->getType() != PtrToIdTy)
       isa = llvm::ConstantExpr::getBitCast(isa, PtrToIdTy);
 
     //  struct
@@ -1012,7 +1026,11 @@
 
     ConstantInitBuilder Builder(CGM);
     auto Fields = Builder.beginStruct();
-    Fields.add(isa);
+    if (!CGM.getTriple().isOSBinFormatCOFF()) {
+      Fields.add(isa);
+    } else {
+      Fields.addNullPointer(PtrTy);
+    }
     // For now, all non-ASCII strings are represented as UTF-16.  As such, the
     // number of bytes is simply double the number of UTF-16 codepoints.  In
     // ASCII strings, the number of bytes is equal to the number of non-ASCII
@@ -1083,6 +1101,10 @@
       ObjCStrGV->setComdat(TheModule.getOrInsertComdat(StringName));
       ObjCStrGV->setVisibility(llvm::GlobalValue::HiddenVisibility);
     }
+    if (CGM.getTriple().isOSBinFormatCOFF()) {
+      std::pair<llvm::Constant*, int> v{ObjCStrGV, 0};
+      EarlyInitList.emplace_back(Sym, v);
+    }
     llvm::Constant *ObjCStr = llvm::ConstantExpr::getBitCast(ObjCStrGV, IdTy);
     ObjCStrings[Str] = ObjCStr;
     ConstantStrings.push_back(ObjCStr);
@@ -1196,6 +1218,26 @@
       ClassSymbol->setInitializer(new llvm::GlobalVariable(TheModule,
           Int8Ty, false, llvm::GlobalValue::ExternalWeakLinkage,
           nullptr, SymbolForClass(Name)));
+    else {
+      if (CGM.getTriple().isOSBinFormatCOFF()) {
+        IdentifierInfo &II = CGM.getContext().Idents.get(Name);
+        TranslationUnitDecl *TUDecl = CGM.getContext().getTranslationUnitDecl();
+        DeclContext *DC = TranslationUnitDecl::castToDeclContext(TUDecl);
+
+        const ObjCInterfaceDecl *OID = nullptr;
+        for (const auto &Result : DC->lookup(&II))
+          if ((OID = dyn_cast<ObjCInterfaceDecl>(Result)))
+            break;
+
+        auto Storage = llvm::GlobalValue::DefaultStorageClass;
+        if (OID->hasAttr<DLLImportAttr>())
+          Storage = llvm::GlobalValue::DLLImportStorageClass;
+        else if (OID->hasAttr<DLLExportAttr>())
+          Storage = llvm::GlobalValue::DLLExportStorageClass;
+
+        cast<llvm::GlobalValue>(ClassSymbol)->setDLLStorageClass(Storage);
+      }
+    }
     assert(ClassSymbol->getName() == SymbolName);
     return ClassSymbol;
   }
@@ -1448,7 +1490,7 @@
         Sym->setSection((Section + SecSuffix).str());
         Sym->setComdat(TheModule.getOrInsertComdat((Prefix +
             Section).str()));
-        Sym->setAlignment(1);
+        Sym->setAlignment(CGM.getPointerAlign().getQuantity());
         return Sym;
       };
       return { Sym("__start_", "$a"), Sym("__stop", "$z") };
@@ -1483,11 +1525,19 @@
     ConstantInitBuilder builder(CGM);
     auto InitStructBuilder = builder.beginStruct();
     InitStructBuilder.addInt(Int64Ty, 0);
-    for (auto *s : SectionsBaseNames) {
-      auto bounds = GetSectionBounds(s);
-      InitStructBuilder.add(bounds.first);
-      InitStructBuilder.add(bounds.second);
-    };
+    if (CGM.getTriple().isOSBinFormatCOFF()) {
+      for (auto *s : PECOFFSectionsBaseNames) {
+        auto bounds = GetSectionBounds(s);
+        InitStructBuilder.add(bounds.first);
+        InitStructBuilder.add(bounds.second);
+      }
+    } else {
+      for (auto *s : SectionsBaseNames) {
+        auto bounds = GetSectionBounds(s);
+        InitStructBuilder.add(bounds.first);
+        InitStructBuilder.add(bounds.second);
+      }
+    }
     auto *InitStruct = InitStructBuilder.finishAndCreateGlobal(".objc_init",
         CGM.getPointerAlign(), false, llvm::GlobalValue::LinkOnceODRLinkage);
     InitStruct->setVisibility(llvm::GlobalValue::HiddenVisibility);
@@ -1577,6 +1627,29 @@
     ConstantStrings.clear();
     Categories.clear();
     Classes.clear();
+
+    if (EarlyInitList.size() > 0) {
+      auto *Init = llvm::Function::Create(llvm::FunctionType::get(CGM.VoidTy,
+            {}), llvm::GlobalValue::InternalLinkage, ".objc_early_init",
+          &CGM.getModule());
+      llvm::IRBuilder<> b(llvm::BasicBlock::Create(CGM.getLLVMContext(), "entry",
+            Init));
+      for (const auto &lateInit : EarlyInitList) {
+        auto *global = TheModule.getGlobalVariable(lateInit.first);
+        if (global) {
+          b.CreateAlignedStore(global,
+              b.CreateStructGEP(lateInit.second.first, lateInit.second.second), CGM.getPointerAlign().getQuantity());
+        }
+      }
+      b.CreateRetVoid();
+      // We can't use the normal LLVM global initialisation array, because we
+      // need to specify that this runs early in library initialisation.
+      auto *InitVar = new llvm::GlobalVariable(CGM.getModule(), Init->getType(), 
+          /*isConstant*/true, llvm::GlobalValue::InternalLinkage,
+          Init, ".objc_early_init_ptr");
+      InitVar->setSection(".CRT$XCLb");
+      CGM.addUsedGlobal(InitVar);
+    }
     return nullptr;
   }
   /// In the v2 ABI, ivar offset variables use the type encoding in their name
@@ -1608,6 +1681,7 @@
   }
   void GenerateClass(const ObjCImplementationDecl *OID) override {
     ASTContext &Context = CGM.getContext();
+    bool IsCOFF = CGM.getTriple().isOSBinFormatCOFF();
 
     // Get the class name
     ObjCInterfaceDecl *classDecl =
@@ -1666,8 +1740,8 @@
     // struct objc_property_list *properties
     metaclassFields.add(GeneratePropertyList(OID, classDecl, /*isClassProperty*/true));
 
-    auto *metaclass = metaclassFields.finishAndCreateGlobal("._OBJC_METACLASS_"
-        + className, CGM.getPointerAlign());
+    auto *metaclass = metaclassFields.finishAndCreateGlobal(SymbolPrefix() +
+        "OBJC_METACLASS_" + className, CGM.getPointerAlign());
 
     auto classFields = builder.beginStruct();
     // struct objc_class *isa;
@@ -1676,15 +1750,28 @@
     // Get the superclass name.
     const ObjCInterfaceDecl * SuperClassDecl =
       OID->getClassInterface()->getSuperClass();
+    llvm::Constant *SuperClass = nullptr;
     if (SuperClassDecl) {
       auto SuperClassName = SymbolForClass(SuperClassDecl->getNameAsString());
-      llvm::Constant *SuperClass = TheModule.getNamedGlobal(SuperClassName);
+      SuperClass = TheModule.getNamedGlobal(SuperClassName);
       if (!SuperClass)
       {
         SuperClass = new llvm::GlobalVariable(TheModule, PtrTy, false,
             llvm::GlobalValue::ExternalLinkage, nullptr, SuperClassName);
+        if (IsCOFF) {
+          auto Storage = llvm::GlobalValue::DefaultStorageClass;
+          if (SuperClassDecl->hasAttr<DLLImportAttr>())
+            Storage = llvm::GlobalValue::DLLImportStorageClass;
+          else if (SuperClassDecl->hasAttr<DLLExportAttr>())
+            Storage = llvm::GlobalValue::DLLExportStorageClass;
+
+          cast<llvm::GlobalValue>(SuperClass)->setDLLStorageClass(Storage);
+        }
       }
-      classFields.add(llvm::ConstantExpr::getBitCast(SuperClass, PtrTy));
+      if (!IsCOFF)
+        classFields.add(llvm::ConstantExpr::getBitCast(SuperClass, PtrTy));
+      else
+        classFields.addNullPointer(PtrTy);
     } else
       classFields.addNullPointer(PtrTy);
     // const char *name;
@@ -1832,19 +1919,24 @@
       classFields.finishAndCreateGlobal(SymbolForClass(className),
         CGM.getPointerAlign(), false, llvm::GlobalValue::ExternalLinkage);
 
-    if (CGM.getTriple().isOSBinFormatCOFF()) {
-      auto Storage = llvm::GlobalValue::DefaultStorageClass;
-      if (OID->getClassInterface()->hasAttr<DLLImportAttr>())
-        Storage = llvm::GlobalValue::DLLImportStorageClass;
-      else if (OID->getClassInterface()->hasAttr<DLLExportAttr>())
-        Storage = llvm::GlobalValue::DLLExportStorageClass;
-      cast<llvm::GlobalValue>(classStruct)->setDLLStorageClass(Storage);
-    }
-
     auto *classRefSymbol = GetClassVar(className);
     classRefSymbol->setSection(sectionName<ClassReferenceSection>());
     classRefSymbol->setInitializer(llvm::ConstantExpr::getBitCast(classStruct, IdTy));
 
+    if (IsCOFF) {
+      // we can't import a class struct.
+      if (OID->getClassInterface()->hasAttr<DLLExportAttr>()) {
+        cast<llvm::GlobalValue>(classStruct)->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
+        cast<llvm::GlobalValue>(classRefSymbol)->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
+      }
+
+      if (SuperClass) {
+        std::pair<llvm::Constant*, int> v{classStruct, 1};
+        EarlyInitList.emplace_back(SuperClass->getName(), std::move(v));
+      }
+
+    }
+
 
     // Resolve the class aliases, if they exist.
     // FIXME: Class pointer aliases shouldn't exist!
@@ -1872,7 +1964,7 @@
 
     auto classInitRef = new llvm::GlobalVariable(TheModule,
         classStruct->getType(), false, llvm::GlobalValue::ExternalLinkage,
-        classStruct, "._OBJC_INIT_CLASS_" + className);
+        classStruct, SymbolPrefix() + "OBJC_INIT_CLASS_" + className);
     classInitRef->setSection(sectionName<ClassSection>());
     CGM.addUsedGlobal(classInitRef);
 
@@ -1909,6 +2001,18 @@
 "__objc_constant_string"
 };
 
+const char *const CGObjCGNUstep2::PECOFFSectionsBaseNames[8] =
+{
+".objcrt$SEL",
+".objcrt$CLS",
+".objcrt$CLR",
+".objcrt$CAT",
+".objcrt$PCL",
+".objcrt$PCR",
+".objcrt$CAL",
+".objcrt$STR"
+};
+
 /// Support for the ObjFW runtime.
 class CGObjCObjFW: public CGObjCGNU {
 protected: