Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -1769,6 +1769,13 @@
   let Documentation = [SectionDocs];
 }
 
+def CodeSeg : InheritableAttr {
+  let Spellings = [Declspec<"code_seg">];
+  let Args = [StringArgument<"Name">];
+  let Subjects = SubjectList<[Function, CXXRecord], ErrorDiag>;
+  let Documentation = [CodeSegDocs];
+}
+
 def PragmaClangBSSSection : InheritableAttr {
   // This attribute has no spellings as it is only ever created implicitly.
   let Spellings = [];
Index: include/clang/Basic/AttrDocs.td
===================================================================
--- include/clang/Basic/AttrDocs.td
+++ include/clang/Basic/AttrDocs.td
@@ -306,6 +306,18 @@
   }];
 }
 
+def CodeSegDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+The ``__declspec(code_seg)`` attribute enables the placement of code into separate
+named segments that can be paged or locked in memory individually. This attribute
+is used to control the placement of instantiated templates and compiler-generated
+code. See the documentation for `__declspec(code_seg)`_ on MSDN.
+
+.. _`__declspec(code_seg)`: http://msdn.microsoft.com/en-us/library/dn636922.aspx
+  }];
+}
+
 def AllocAlignDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -2668,6 +2668,14 @@
 def warn_attribute_section_on_redeclaration : Warning<
   "section attribute is specified on redeclared variable">, InGroup<Section>;
 
+def err_mismatched_code_seg_base : Error<
+  "derived class must specify the same code segment as its base classes">;
+def err_mismatched_code_seg_override : Error<
+  "overriding virtual function must specify the same code segment as its overridden function">;
+def err_conflicting_codeseg_attribute : Error<
+  "conflicting code segment specifiers">;
+def warn_duplicate_codeseg_attribute : Warning<
+  "duplicate code segment specifiers">, InGroup<Section>;
 def err_anonymous_property: Error<
   "anonymous property is not supported">;
 def err_property_is_variably_modified : Error<
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -1934,6 +1934,7 @@
   bool shouldLinkDependentDeclWithPrevious(Decl *D, Decl *OldDecl);
   void CheckMain(FunctionDecl *FD, const DeclSpec &D);
   void CheckMSVCRTEntryPoint(FunctionDecl *FD);
+  Attr *getImplicitSectionAttrForFunction(const FunctionDecl *FD, bool IsDefinition = true);
   Decl *ActOnParamDeclarator(Scope *S, Declarator &D);
   ParmVarDecl *BuildParmVarDeclForTypedef(DeclContext *DC,
                                           SourceLocation Loc,
@@ -5836,6 +5837,7 @@
   /// ensure that referenceDLLExportedClassMethods is called some point later
   /// when all outer classes of Class are complete.
   void checkClassLevelDLLAttribute(CXXRecordDecl *Class);
+  void checkClassLevelSectionAttribute(CXXRecordDecl *Class);
 
   void referenceDLLExportedClassMethods();
 
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -2667,9 +2667,14 @@
         Diag(New->getLocation(), diag::warn_attribute_section_on_redeclaration);
         Diag(Old->getLocation(), diag::note_previous_declaration);
       }
+    } else if (isa<CXXMethodDecl>(New)) {
+      const auto *NewSA = New->getAttr<SectionAttr>();
+      if (!NewSA->isImplicit()) {
+        Diag(New->getLocation(), diag::warn_mismatched_section);
+        Diag(Old->getLocation(), diag::note_previous_declaration);
+      }
     }
   }
-
   if (!Old->hasAttrs())
     return;
 
@@ -8716,18 +8721,18 @@
                                                  PragmaClangTextSection.PragmaLocation));
   }
 
-  // Apply an implicit SectionAttr if #pragma code_seg is active.
-  if (CodeSegStack.CurrentValue && D.isFunctionDefinition() &&
-      !NewFD->hasAttr<SectionAttr>()) {
-    NewFD->addAttr(
-        SectionAttr::CreateImplicit(Context, SectionAttr::Declspec_allocate,
-                                    CodeSegStack.CurrentValue->getString(),
-                                    CodeSegStack.CurrentPragmaLocation));
-    if (UnifySection(CodeSegStack.CurrentValue->getString(),
-                     ASTContext::PSF_Implicit | ASTContext::PSF_Execute |
-                         ASTContext::PSF_Read,
-                     NewFD))
-      NewFD->dropAttr<SectionAttr>();
+  // Apply an implicit SectionAttr from class declspec or from
+  // #pragma code_seg if active.
+  if (!NewFD->hasAttr<SectionAttr>()) {
+    if (Attr *SAttr = getImplicitSectionAttrForFunction(NewFD,
+                                                        D.isFunctionDefinition())) {
+      NewFD->addAttr(SAttr);
+      if (UnifySection(cast<SectionAttr>(SAttr)->getName(),
+                       ASTContext::PSF_Implicit | ASTContext::PSF_Execute |
+                       ASTContext::PSF_Read,
+                       NewFD))
+        NewFD->dropAttr<SectionAttr>();
+    }
   }
 
   // Handle attributes.
@@ -9177,6 +9182,64 @@
   return NewFD;
 }
 
+/// Return a SectionAttr from a containing class.  The Microsoft docs say
+/// when __declspec(code_seg) "is applied to a class, all member functions of
+/// the class and nested classes -- this includes compiler-generated special
+/// member functions -- are put in the specified segment."
+/// The actual behavior is a little more complicated. The Microsoft compiler
+/// won't check outer classes if there is an active value from #pragma code_seg.
+/// The section is always applied from the direct parent but only from outer
+/// classes when the #pragma code_seg stack is empty. See:
+/// https://reviews.llvm.org/D22931, the Microsoft feedback page is no longer
+/// available since MS has removed the page.
+static Attr *getImplicitSectionAttrFromClass(Sema &S, const FunctionDecl *FD) {
+  const auto *Method = dyn_cast<CXXMethodDecl>(FD);
+  if (!Method)
+    return nullptr;
+  const CXXRecordDecl *Parent = Method->getParent();
+  if (const auto *SAttr = Parent->getAttr<SectionAttr>()) {
+    Attr *NewAttr = SAttr->clone(S.getASTContext());
+    NewAttr->setImplicit(true);
+    return NewAttr;
+  }
+
+  // The Microsoft compiler won't check outer classes for the section
+  // when the #pragma code_seg stack is active.
+  if (S.CodeSegStack.CurrentValue)
+    return nullptr;
+
+  while (Parent = dyn_cast<CXXRecordDecl>(Parent->getParent())) {
+    if (const auto *SAttr = Parent->getAttr<SectionAttr>()) {
+      Attr *NewAttr = SAttr->clone(S.getASTContext());
+      NewAttr->setImplicit(true);
+      return NewAttr;
+    }
+  }
+  return nullptr;
+}
+
+/// \brief Returns an implicit SectionAttr for a function.
+///
+/// \param FD Function being declared.
+/// \param IsDefinition Whether it is a definition or just a declarartion.
+/// \returns A SectionAttr to apply to the function or nullptr if no
+///          attribute should be added.
+///
+/// First tries to find a SectionAttr on a containing class (from
+/// a __declspec(code_seg)).  If not found on the class, and if the function is
+/// also a definition it will use the current #pragma code_seg value.
+Attr *Sema::getImplicitSectionAttrForFunction(const FunctionDecl *FD, bool IsDefinition) {
+  if (Attr *A = getImplicitSectionAttrFromClass(*this, FD))
+    return A;
+  if (IsDefinition && CodeSegStack.CurrentValue) {
+    return SectionAttr::CreateImplicit(getASTContext(),
+                                       SectionAttr::Declspec_allocate,
+                                       CodeSegStack.CurrentValue->getString(),
+                                       CodeSegStack.CurrentPragmaLocation);
+  }
+  return nullptr;
+}
+
 /// Checks if the new declaration declared in dependent context must be
 /// put in the same redeclaration chain as the specified declaration.
 ///
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -2853,6 +2853,13 @@
 SectionAttr *Sema::mergeSectionAttr(Decl *D, SourceRange Range,
                                     StringRef Name,
                                     unsigned AttrSpellingListIndex) {
+  // Explicit or partial specializations do not inherit
+  // the code_seg attribute from the primary template.
+  if (const auto *FD = dyn_cast<FunctionDecl>(D)){
+    if (FD->isFunctionTemplateSpecialization())
+      return nullptr;
+  }
+
   if (SectionAttr *ExistingAttr = D->getAttr<SectionAttr>()) {
     if (ExistingAttr->getName() == Name)
       return nullptr;
@@ -2941,6 +2948,25 @@
       ::new (S.Context) TargetAttr(AL.getRange(), S.Context, Str, Index);
   D->addAttr(NewAttr);
 }
+static void handleCodeSegAttr(Sema &S, Decl *D, const AttributeList &AL) {
+  StringRef Str;
+  SourceLocation LiteralLoc;
+  if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, &LiteralLoc))
+    return;
+  if (!S.checkSectionName(LiteralLoc, Str))
+    return;
+  if (const auto *ExistingAttr = D->getAttr<SectionAttr>()) {
+    if (!ExistingAttr->isImplicit()) {
+      S.Diag(AL.getLoc(), ExistingAttr->getName() == Str 
+		            ? diag::warn_duplicate_codeseg_attribute
+			    : diag::err_conflicting_codeseg_attribute);	    
+      return;
+    }
+    D->dropAttr<SectionAttr>();
+  }
+  D->addAttr(::new (S.Context) SectionAttr(
+      AL.getRange(), S.Context, Str, AL.getAttributeSpellingListIndex()));
+}
 
 static void handleCleanupAttr(Sema &S, Decl *D, const AttributeList &AL) {
   Expr *E = AL.getArgAsExpr(0);
@@ -6297,6 +6323,9 @@
   case AttributeList::AT_Uuid:
     handleUuidAttr(S, D, AL);
     break;
+  case AttributeList::AT_CodeSeg:
+    handleCodeSegAttr(S, D, AL);
+    break;
   case AttributeList::AT_MSInheritance:
     handleMSInheritanceAttr(S, D, AL);
     break;
Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -2231,6 +2231,20 @@
   CXXRecordDecl *CXXBaseDecl = cast<CXXRecordDecl>(BaseDecl);
   assert(CXXBaseDecl && "Base type is not a C++ type");
 
+  // Microsoft docs say:
+  // "If a base-class has a code_seg attribute, derived classes must have the
+  // same attribute."
+   const auto *BaseSA = CXXBaseDecl->getAttr<SectionAttr>();
+   const auto *DerivedSA = Class->getAttr<SectionAttr>();
+   if (BaseSA || DerivedSA) {
+     if (!BaseSA || !DerivedSA || BaseSA->getName() != DerivedSA->getName()) {
+       Diag(Class->getLocation(), diag::err_mismatched_code_seg_base);
+       Diag(CXXBaseDecl->getLocation(), diag::note_base_class_specified_here)
+	  << CXXBaseDecl;
+       return nullptr;
+     }
+   }
+
   // A class which contains a flexible array member is not suitable for use as a
   // base class:
   //   - If the layout determines that a base comes before another base,
@@ -5576,6 +5590,16 @@
   }
 }
 
+void Sema::checkClassLevelSectionAttribute(CXXRecordDecl *Class) {
+  // Mark any compiler-generated routines with the implicit Section attribute.
+  for (auto *Method : Class->methods()) {
+    if (Method->isUserProvided())
+      continue;
+    if (Attr *A = getImplicitSectionAttrForFunction(Method))
+      Method->addAttr(A);
+  }
+}
+
 /// Check class-level dllimport/dllexport attribute.
 void Sema::checkClassLevelDLLAttribute(CXXRecordDecl *Class) {
   Attr *ClassAttr = getDLLAttr(Class);
@@ -6095,6 +6119,7 @@
   }
 
   checkClassLevelDLLAttribute(Record);
+  checkClassLevelSectionAttribute(Record);
 
   bool ClangABICompat4 =
       Context.getLangOpts().getClangABICompat() <= LangOptions::ClangABI::Ver4;
@@ -14537,6 +14562,16 @@
              diag::note_overridden_marked_noescape);
       }
   }
+  // Virtual overrides must have the same code_seg.
+  const auto *OldSA = Old->getAttr<SectionAttr>();
+  const auto *NewSA = New->getAttr<SectionAttr>();
+  if (OldSA || NewSA) {
+    if (!OldSA || !NewSA || NewSA->getName() != OldSA->getName()) {
+      Diag(New->getLocation(), diag::err_mismatched_code_seg_override);
+      Diag(Old->getLocation(), diag::note_previous_declaration);
+      return true;
+    }
+  }
 
   CallingConv NewCC = NewFT->getCallConv(), OldCC = OldFT->getCallConv();
 
Index: lib/Sema/SemaLambda.cpp
===================================================================
--- lib/Sema/SemaLambda.cpp
+++ lib/Sema/SemaLambda.cpp
@@ -910,6 +910,10 @@
   AddRangeBasedOptnone(Method);
   
   // Attributes on the lambda apply to the method.  
+  if (Attr *A = getImplicitSectionAttrForFunction(Method))
+    Method->addAttr(A);
+  
+  // Attributes on the lambda apply to the method.
   ProcessDeclAttributes(CurScope, Method, ParamInfo);
 
   // CUDA lambdas get implicit attributes based on the scope in which they're
Index: test/CodeGenCXX/code_seg1.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/code_seg1.cpp
@@ -0,0 +1,135 @@
+// RUN: %clang_cc1 -emit-llvm -triple i686-pc-win32 -fms-extensions -verify -o - %s | FileCheck %s
+// expected-no-diagnostics
+
+// Simple case
+
+int __declspec(code_seg("foo_one")) bar_one() { return 1; }
+//CHECK: define {{.*}}bar_one{{.*}} section "foo_one"
+
+// Simple case - explicit attribute used over pragma
+#pragma code_seg("foo_two")
+int __declspec(code_seg("foo_three")) bar2() { return 2; }
+//CHECK: define {{.*}}bar2{{.*}} section "foo_three"
+
+// Check that attribute on one function doesn't affect another
+int another1() { return 1001; }
+//CHECK: define {{.*}}another1{{.*}} section "foo_two"
+
+// Member functions
+
+struct __declspec(code_seg("foo_four")) Foo {
+  int bar3() {return 0;}
+  int bar4();
+  int __declspec(code_seg("foo_six")) bar6() { return 6; }
+  int bar7() { return 7; }
+  struct Inner {
+    int bar5() { return 5; }
+  } z;
+  virtual int baz1() { return 1; }
+};
+
+struct __declspec(code_seg("foo_four")) FooTwo : Foo {
+  int baz1() { return 20; }
+};
+
+int caller1() {
+  Foo f; return f.bar3();
+}
+
+//CHECK: define {{.*}}bar3@Foo{{.*}} section "foo_four"
+int Foo::bar4() { return 4; }
+//CHECK: define {{.*}}bar4@Foo{{.*}} section "foo_four"
+
+#pragma code_seg("someother")
+
+int caller2() {
+  Foo f;
+  Foo *fp = new FooTwo;
+  return f.z.bar5() + f.bar6() + f.bar7() + fp->baz1();
+}
+// TBD: MS Compiler and Docs do not match for nested routines
+// Doc says:      define {{.*}}bar5@Inner@Foo{{.*}} section "foo_four"
+// Compiler says: define {{.*}}bar5@Inner@Foo{{.*}} section "foo_two"
+//CHECK: define {{.*}}bar6@Foo{{.*}} section "foo_six"
+//CHECK: define {{.*}}bar7@Foo{{.*}} section "foo_four"
+// Check that code_seg active at class declaration is not used on member
+// declared outside class when it is not active.
+
+#pragma code_seg(push,"AnotherSeg")
+
+struct FooThree {
+  int bar8();
+  int bar9() { return 9; }
+};
+
+#pragma code_seg(pop)
+
+
+int FooThree::bar8() {return 0;}
+
+int caller3()
+{
+  FooThree f;
+  return f.bar8() + f.bar9();
+}
+
+//CHECK: define {{.*}}bar8@FooThree{{.*}} section "someother"
+//CHECK: define {{.*}}bar9@FooThree{{.*}} section "AnotherSeg"
+
+struct NonTrivialCopy {
+  NonTrivialCopy();
+  NonTrivialCopy(const NonTrivialCopy&);
+  ~NonTrivialCopy();
+};
+
+// check the section for compiler-generated function with declspec.
+
+struct __declspec(code_seg("foo_seven")) FooFour {
+  FooFour() {}
+  int __declspec(code_seg("foo_eight")) bar10(int t) { return t; }
+  NonTrivialCopy f;
+};
+
+//CHECK: define {{.*}}0FooFour@@QAE@ABU0@@Z{{.*}} section "foo_seven"
+// check the section for compiler-generated function with no declspec.
+
+struct FooFive {
+  FooFive() {}
+  int __declspec(code_seg("foo_nine")) bar11(int t) { return t; }
+  NonTrivialCopy f;
+};
+
+//CHECK: define {{.*}}0FooFive@@QAE@ABU0@@Z{{.*}} section "someother"
+
+#pragma code_seg("YetAnother")
+int caller4()
+{
+  FooFour z1;
+  FooFour z2 = z1;
+  FooFive y1;
+  FooFive y2 = y1;
+  return z2.bar10(0) + y2.bar11(1);
+}
+
+//CHECK: define {{.*}}bar10@FooFour{{.*}} section "foo_eight"
+//CHECK: define {{.*}}bar11@FooFive{{.*}} section "foo_nine"
+
+struct FooSix {
+  #pragma code_seg("foo_ten")
+  int bar12() { return 12; }
+  #pragma code_seg("foo_eleven")
+  int bar13() { return 13; }
+};
+
+int bar14() { return 14; }
+//CHECK: define {{.*}}bar14{{.*}} section "foo_eleven"
+
+int caller5()
+{
+  FooSix fsix;
+  return fsix.bar12() + fsix.bar13();
+}
+
+//CHECK: define {{.*}}bar12@FooSix{{.*}} section "foo_ten"
+//CHECK: define {{.*}}bar13@FooSix{{.*}} section "foo_eleven"
+//CHECK: define {{.*}}baz1@FooTwo{{.*}} section "foo_four"
Index: test/CodeGenCXX/code_seg2.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/code_seg2.cpp
@@ -0,0 +1,141 @@
+// RUN: %clang_cc1 -emit-llvm -triple i686-pc-win32 -std=c++11 -fms-extensions -verify -o - %s | FileCheck %s
+// expected-no-diagnostics
+
+// Class member templates
+
+#pragma code_seg(push, "something")
+
+template <typename T>
+struct __declspec(code_seg("foo_one")) ClassOne {
+  int bar1(T t) { return int(t); }
+  int bar2(T t);
+  int bar3(T t);
+};
+
+template <typename T>
+int ClassOne<T>::bar2(T t) {
+  return int(t);
+}
+
+int caller1() {
+  ClassOne<int> coi;
+  return coi.bar1(6) + coi.bar2(3);
+}
+
+//CHECK: define {{.*}}bar1@?$ClassOne{{.*}} section "foo_one"
+//CHECK: define {{.*}}bar2@?$ClassOne{{.*}} section "foo_one"
+
+
+template <typename T>
+struct ClassTwo {
+  int bar11(T t) { return int(t); }
+  int bar22(T t);
+  int bar33(T t);
+};
+
+#pragma code_seg("newone")
+
+template <typename T>
+int ClassTwo<T>::bar22(T t) {
+  return int(t);
+}
+
+#pragma code_seg("someother")
+
+template <typename T>
+int ClassTwo<T>::bar33(T t) {
+  return int(t);
+}
+
+#pragma code_seg("yetanother")
+
+int caller2() {
+  ClassTwo<int> coi;
+  return coi.bar11(6) + coi.bar22(3) + coi.bar33(44);
+}
+
+//CHECK: define {{.*}}bar11@?$ClassTwo{{.*}} section "something"
+//CHECK: define {{.*}}bar22@?$ClassTwo{{.*}} section "newone"
+//CHECK: define {{.*}}bar33@?$ClassTwo{{.*}} section "someother"
+
+template<>
+struct ClassOne<double>
+{
+  int bar44(double d) { return 1; }
+};
+template<>
+struct  __declspec(code_seg("foo_three")) ClassOne<long>
+{
+  int bar55(long d) { return 1; }
+};
+
+#pragma code_seg("onemore")
+int caller3() {
+  ClassOne<double> d;
+  ClassOne<long> l;
+  return d.bar44(1.0)+l.bar55(1);
+}
+
+//CHECK: define {{.*}}bar44{{.*}} section "yetanother"
+//CHECK: define {{.*}}bar55{{.*}} section "foo_three"
+
+
+// Function templates
+template <typename T>
+int __declspec(code_seg("foo_four")) bar66(T t) { return int(t); }
+
+// specializations do not take the segment from primary
+template<>
+int bar66(int i) { return 0; }
+
+#pragma code_seg(pop)
+
+template<>
+int bar66(char c) { return 0; }
+
+struct A1 {int i;};
+template<>
+int __declspec(code_seg("foo_five")) bar66(A1 a) { return a.i; }
+
+int caller4()
+{
+// but instantiations do use the section from the primary
+return bar66(0) + bar66(1.0) + bar66('c');
+}
+//CHECK: define {{.*}}bar66@H{{.*}} section "onemore"
+//CHECK-NOT: define {{.*}}bar66@D{{.*}} section
+//CHECK: define {{.*}}bar66@UA1{{.*}} section "foo_five"
+//CHECK: define {{.*}}bar66@N{{.*}} section "foo_four"
+
+
+#pragma code_seg("another")
+// Member functions
+struct __declspec(code_seg("foo_four")) Foo {
+  int bar3() {return 0;}
+ __declspec(code_seg("foo_lala")) int bar4() {return 0;} }; int caller() {Foo f; return f.bar3() + f.bar4(); }
+
+//CHECK: define {{.*}}bar3@Foo{{.*}} section "foo_four"
+//CHECK: define {{.*}}bar4@Foo{{.*}} section "foo_lala"
+
+// Lambdas
+#pragma code_seg("something")
+
+int __declspec(code_seg("foo")) bar1()
+{
+  int lala = 4;
+  auto l = [=](int i) { return i+4; };
+  return l(-4);
+}
+
+//CHECK: define {{.*}}bar1{{.*}} section "foo"
+//CHECK: define {{.*}}lambda{{.*}}bar1{{.*}} section "something"
+
+double __declspec(code_seg("foo")) bar2()
+{
+  double lala = 4.0;
+  auto l = [=](double d) __declspec(code_seg("another"))  { return d+4.0; };
+  return l(4.0);
+}
+
+//CHECK: define {{.*}}bar2{{.*}} section "foo"
+//CHECK: define {{.*}}lambda{{.*}}bar2{{.*}} section "another"
Index: test/CodeGenCXX/code_seg3.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/code_seg3.cpp
@@ -0,0 +1,86 @@
+// RUN: %clang_cc1 -emit-llvm -triple i686-pc-win32 -fms-extensions -verify -o - %s | FileCheck %s
+// expected-no-diagnostics
+// The Microsoft document says: "When this attribute is applied to a class,
+// all member functions of the class and nested classes - this includes 
+// compiler-generated special member functions - are put in the specified segment."
+// But the MS compiler does not always follow that.  A bug has been reported:
+// see https://reviews.llvm.org/D22931, the Microsoft feedback page is no
+// longer available.
+// The MS compiler will apply a declspec from the parent class if there is no
+// #pragma code_seg active at the class definition.  If there is an active
+// code_seg that is used instead.
+
+// No active code_seg
+
+struct __declspec(code_seg("foo_outer")) Foo1 {
+  struct Inner {
+    void bar1();
+    static void bar2();
+  };
+};
+void Foo1::Inner::bar1() {}
+void Foo1::Inner::bar2() {}
+
+//CHECK: define {{.*}}bar1@Inner@Foo1{{.*}} section "foo_outer"
+//CHECK: define {{.*}}bar2@Inner@Foo1{{.*}} section "foo_outer"
+
+struct __declspec(code_seg("foo_outer")) Foo2 {
+  struct __declspec(code_seg("foo_inner")) Inner {
+    void bar1();
+    static void bar2();
+  };
+};
+void Foo2::Inner::bar1() {}
+void Foo2::Inner::bar2() {}
+
+//CHECK: define {{.*}}bar1@Inner@Foo2{{.*}} section "foo_inner"
+//CHECK: define {{.*}}bar2@Inner@Foo2{{.*}} section "foo_inner"
+
+#pragma code_seg(push, "otherseg")
+struct __declspec(code_seg("foo_outer")) Foo3 {
+  struct Inner {
+    void bar1();
+    static void bar2();
+  };
+};
+void Foo3::Inner::bar1() {}
+void Foo3::Inner::bar2() {}
+
+//CHECK: define {{.*}}bar1@Inner@Foo3{{.*}} section "otherseg"
+//CHECK: define {{.*}}bar2@Inner@Foo3{{.*}} section "otherseg"
+
+struct __declspec(code_seg("foo_outer")) Foo4 {
+  struct __declspec(code_seg("foo_inner")) Inner {
+    void bar1();
+    static void bar2();
+  };
+};
+void Foo4::Inner::bar1() {}
+void Foo4::Inner::bar2() {}
+
+//CHECK: define {{.*}}bar1@Inner@Foo4{{.*}} section "foo_inner"
+//CHECK: define {{.*}}bar2@Inner@Foo4{{.*}} section "foo_inner"
+
+#pragma code_seg(pop)
+// Back to no active pragma
+struct __declspec(code_seg("foo_outer")) Foo5 {
+  struct Inner {
+    void bar1();
+    static void bar2();
+    struct __declspec(code_seg("inner1_seg")) Inner1 {
+      struct Inner2 {
+        void bar1();
+        static void bar2();
+      };
+    };
+  };
+};
+void Foo5::Inner::bar1() {}
+void Foo5::Inner::bar2() {}
+void Foo5::Inner::Inner1::Inner2::bar1() {}
+void Foo5::Inner::Inner1::Inner2::bar2() {}
+
+//CHECK: define {{.*}}bar1@Inner@Foo5{{.*}} section "foo_outer"
+//CHECK: define {{.*}}bar2@Inner@Foo5{{.*}} section "foo_outer"
+//CHECK: define {{.*}}bar1@Inner2@Inner1@Inner@Foo5{{.*}} section "inner1_seg"
+//CHECK: define {{.*}}bar2@Inner2@Inner1@Inner@Foo5{{.*}} section "inner1_seg"
Index: test/CodeGenCXX/code_seg4.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/code_seg4.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-extensions %s -triple x86_64-pc-win32
+// expected-no-diagnostics
+
+// Non-Member Function Overloading is involved
+
+int __declspec(code_seg("foo_one")) bar_one(int) { return 1; }
+//CHECK: define {{.*}}bar_one{{.*}} section "foo_one"
+int __declspec(code_seg("foo_two")) bar_one(int,float) { return 11; }
+//CHECK: define {{.*}}bar_one{{.*}} section "foo_two"
+int __declspec(code_seg("foo_three")) bar_one(float) { return 12; }
+//CHECK: define {{.*}}bar_one{{.*}} section "foo_three"
+
+// virtual function overloading is involved
+
+struct __declspec(code_seg("my_one")) Base3 {
+  virtual int barA(int) { return 1; }
+  virtual int barA(int,float) { return 2; }
+  virtual int barA(float) { return 3; }
+
+  virtual void __declspec(code_seg("my_two")) barB(int) { }
+  virtual void  __declspec(code_seg("my_three")) barB(float) { }
+  virtual void __declspec(code_seg("my_four")) barB(int, float) { }
+
+};
+
+//CHECK: define {{.*}}barA@Base3{{.*}} section "my_one"
+//CHECK: define {{.*}}barA@Base3{{.*}} section "my_one"
+//CHECK: define {{.*}}barA@Base3{{.*}} section "my_one"
+//CHECK: define {{.*}}barB@Base3{{.*}} section "my_two"
+//CHECK: define {{.*}}barB@Base3{{.*}} section "my_three"
+//CHECK: define {{.*}}barB@Base3{{.*}} section "my_four"
Index: test/SemaCXX/code_seg.cpp
===================================================================
--- /dev/null
+++ test/SemaCXX/code_seg.cpp
@@ -0,0 +1,104 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-extensions %s -triple x86_64-pc-win32
+
+struct __declspec(code_seg("my_one")) FooOne {
+  int barC();
+};
+
+struct FooTwo {
+  int __declspec(code_seg("my_three")) barD();
+  int barE();
+};
+int __declspec(code_seg("my_four")) FooOne::barC() { return 10; }
+// expected-warning@-1 {{section does not match previous declaration}}
+// expected-note@3{{previous attribute is here}}
+int __declspec(code_seg("my_five")) FooTwo::barD() { return 20; }
+// expected-warning@-1 {{section does not match previous declaration}}
+// expected-note@8 {{previous attribute is here}}
+int __declspec(code_seg("my_six")) FooTwo::barE() { return 30; }
+// expected-warning@-1 {{section does not match previous declaration}}
+// expected-note@9 {{previous declaration is here}}
+
+// Microsoft docs say:
+// If a base-class has a code_seg attribute, derived classes must have the
+// same attribute.
+struct __declspec(code_seg("my_base")) Base1 {};
+struct Base2 {};
+
+struct D1 : Base1 {};
+//expected-error@-1 {{derived class must specify the same code segment as its base classes}}
+// expected-note@24 {{base class 'Base1' specified here}}
+struct __declspec(code_seg("my_derived")) D2 : Base1 {};
+// expected-error@-1 {{derived class must specify the same code segment as its base classes}}
+// expected-note@24 {{base class 'Base1' specified here}}
+struct __declspec(code_seg("my_derived")) D3 : Base2 {};
+// expected-error@-1 {{derived class must specify the same code segment as its base classes}}
+// expected-note@25 {{base class 'Base2' specified here}}
+
+template <typename T> struct __declspec(code_seg("my_base")) MB : T { };
+template <typename T> struct __declspec(code_seg("my_derived")) MD : T { };
+MB<Base1> mb1; // ok
+MB<Base2> mb2;
+// expected-error@37 {{derived class must specify the same code segment as its base classes}}
+// expected-note@-2 {{in instantiation of template class}}
+// expected-note@25  {{base class 'Base2' specified here}}
+MD<Base1> md1;
+// expected-error@38 {{derived class must specify the same code segment as its base classes}}
+// expected-note@-2 {{in instantiation of template class}}
+// expected-note@24 {{base class 'Base1' specified here}}
+MD<Base2> md2;
+// expected-error@38 {{derived class must specify the same code segment as its base classes}}
+// expected-note@-2 {{in instantiation of template class}}
+// expected-note@25 {{base class 'Base2' specified here}}
+
+// Virtual overrides must have the same code_seg.
+struct __declspec(code_seg("my_one")) Base3 {
+  virtual int barA() { return 1; }
+  virtual int __declspec(code_seg("my_two")) barB() { return 2; }
+};
+struct __declspec(code_seg("my_one")) Derived3 : Base3 {
+  int barA() { return 4; } // ok
+  int barB() { return 6; }
+  // expected-error@-1 {{overriding virtual function must specify the same code segment as its overridden function}}
+  // expected-note@56 {{previous declaration is here}}
+};
+
+struct Base4 {
+  virtual int __declspec(code_seg("my_one")) barA() {return 1;}
+  virtual int barB() { return 2;}
+};
+struct Derived4 : Base4 {
+  virtual int barA() {return 1;}
+  // expected-error@-1 {{overriding virtual function must specify the same code segment as its overridden function}}
+  // expected-note@66 {{previous declaration is here}}
+  virtual int __declspec(code_seg("my_two")) barB() {return 1;}
+  // expected-error@-1 {{overriding virtual function must specify the same code segment as its overridden function}}
+  // expected-note@67 {{previous declaration is here}}
+};
+
+// MS gives an error when different code segments are used but a warning when a duplicate is used
+
+// Function
+int __declspec(code_seg("foo")) __declspec(code_seg("foo")) bar1() { return 1; }
+// expected-warning@-1 {{duplicate code segment specifiers}}
+int __declspec(code_seg("foo")) __declspec(code_seg("bar")) bar2() { return 1; }
+// expected-error@-1 {{conflicting code segment specifiers}}
+
+// Class
+struct __declspec(code_seg("foo")) __declspec(code_seg("foo")) Foo {
+  // expected-warning@-1 {{duplicate code segment specifiers}}
+  int bar3() {return 0;}
+};
+struct __declspec(code_seg("foo")) __declspec(code_seg("bar")) FooSix {
+  // expected-error@-1 {{conflicting code segment specifiers}}
+  int bar3() {return 0;}
+};
+
+//Class Members
+struct FooThree {
+  int __declspec(code_seg("foo")) __declspec(code_seg("foo")) bar1() { return 1; }
+  // expected-warning@-1 {{duplicate code segment specifiers}}
+  int __declspec(code_seg("foo")) __declspec(code_seg("bar")) bar2() { return 1; }
+  // expected-error@-1 {{conflicting code segment specifiers}}
+  int bar8();
+  int bar9() { return 9; }
+};
Index: test/SemaCXX/code_seg1.cpp
===================================================================
--- /dev/null
+++ test/SemaCXX/code_seg1.cpp
@@ -0,0 +1,96 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-extensions %s -triple x86_64-pc-win32
+
+// Multiple inheritance is involved (code segmments all disagree between the bases and derived class)
+struct __declspec(code_seg("my_base")) Base1 {};
+struct Base2 {};
+
+struct D1 : Base1, Base2 {};
+// expected-error@-1 {{derived class must specify the same code segment as its base classes}}
+// expected-note@4 {{base class 'Base1' specified here}}
+
+struct __declspec(code_seg("my_derived")) D2 : Base2, Base1 {};
+// expected-error@-1 {{derived class must specify the same code segment as its base classes}}
+// expected-error@-2 {{derived class must specify the same code segment as its base classes}}
+// expected-note@5 {{base class 'Base2' specified here}}
+// expected-note@4 {{base class 'Base1' specified here}}
+
+// Multiple inheritance (code segments partially agree between the bases and the derived class)
+struct __declspec(code_seg("base_class")) BaseClass1 {};
+struct __declspec(code_seg("base_class")) BaseClass2 {};
+
+struct Derived1 : BaseClass1, BaseClass2 {};
+// expected-error@-1 {{derived class must specify the same code segment as its base classes}}
+// expected-error@-2 {{derived class must specify the same code segment as its base classes}}
+// expected-note@18 {{base class 'BaseClass1' specified here}}
+// expected-note@19 {{base class 'BaseClass2' specified here}}
+
+struct __declspec(code_seg("derived_class")) Derived2 : BaseClass2, BaseClass1 {};
+// expected-error@-1 {{derived class must specify the same code segment as its base classes}}
+// expected-error@-2 {{derived class must specify the same code segment as its base classes}}
+// expected-note@19 {{base class 'BaseClass2' specified here}}
+// expected-note@18 {{base class 'BaseClass1' specified here}}
+
+struct __declspec(code_seg("base_class")) Derived3 : BaseClass2, BaseClass1 {}; //OK
+struct __declspec(code_seg("base_class")) Derived4 : BaseClass1, BaseClass2 {}; //OK
+
+// Multiple inheritance is involved (code segmments all agree between the bases and derived class)
+struct __declspec(code_seg("foo_base")) B1 {};
+struct __declspec(code_seg("foo_base")) B2 {};
+struct __declspec(code_seg("foo_base")) Derived : B1, B2 {};
+
+// virtual Inheritance is involved (code segmments all disagree between the bases and derived class)
+struct __declspec(code_seg("my_one")) Base {
+  virtual int barA() { return 1; } ;
+};
+
+struct __declspec(code_seg("my_two")) Derived5 : virtual Base {
+  virtual int barB() { return 2; };
+};
+// expected-error@-3 {{derived class must specify the same code segment as its base classes}}
+// expected-note@42 {{base class 'Base' specified here}}
+
+struct __declspec(code_seg("my_three")) Derived6 : virtual Base {
+  virtual int barC() { return 3; };
+};
+// expected-error@-3 {{derived class must specify the same code segment as its base classes}}
+// expected-note@42 {{base class 'Base' specified here}}
+
+struct __declspec(code_seg("my_four")) Derived7 : Derived5, Derived6 {};
+// expected-error@-1 {{derived class must specify the same code segment as its base classes}}
+// expected-error@-2 {{derived class must specify the same code segment as its base classes}}
+// expected-note@46 {{base class 'Derived5' specified here}}
+// expected-note@52 {{base class 'Derived6' specified here}}
+
+// virtual Inheritance is involved (code segmments partially agree between the bases and derived class)
+struct __declspec(code_seg("my_class")) BaseClass {
+  virtual int barA() { return 1; } ;
+};
+
+struct __declspec(code_seg("my_class")) DerivedClass1 : virtual BaseClass { //OK
+  virtual int barB() { return 2; };
+};
+
+struct __declspec(code_seg("my_class")) DerivedClass2 : virtual BaseClass { //OK
+  virtual int barC() { return 3; };
+};
+
+struct __declspec(code_seg("my_derived_one")) DerivedClass3 : DerivedClass1, DerivedClass2 {};
+// expected-error@-1 {{derived class must specify the same code segment as its base classes}}
+// expected-error@-2 {{derived class must specify the same code segment as its base classes}}
+// expected-note@69 {{base class 'DerivedClass1' specified here}}
+// expected-note@73 {{base class 'DerivedClass2' specified here}}
+
+// virtual Inheritance is involved (code segmments all agree between the bases and derived class)
+struct __declspec(code_seg("foo_one")) Class {
+  virtual int foo1() { return 10; } ;
+};
+
+struct __declspec(code_seg("foo_one")) Derived_One: virtual Class { //OK
+  virtual int foo2() { return 20; };
+};
+
+struct __declspec(code_seg("foo_one")) Derived_Two : virtual Class { //OK
+  virtual int foo3() { return 30; };
+};
+
+struct __declspec(code_seg("foo_one")) Derived_Three : Derived_One, Derived_Two {}; //OK