Index: lib/AST/MicrosoftMangle.cpp
===================================================================
--- lib/AST/MicrosoftMangle.cpp
+++ lib/AST/MicrosoftMangle.cpp
@@ -2761,7 +2761,18 @@
 
 void MicrosoftMangleContextImpl::mangleCXXVTableBitSet(const CXXRecordDecl *RD,
                                                        raw_ostream &Out) {
-  llvm::report_fatal_error("Cannot mangle bitsets yet");
+  Linkage L = RD->getLinkageInternal();
+  if (L == InternalLinkage || L == UniqueExternalLinkage) {
+    // This part of the identifier needs to be unique across all translation
+    // units in the linked program. The scheme fails if multiple translation
+    // units are compiled using the same relative source file path, or if
+    // multiple translation units are built from the same source file.
+    SourceManager &SM = getASTContext().getSourceManager();
+    Out << "[" << SM.getFileEntryForID(SM.getMainFileID())->getName() << "]";
+  }
+
+  MicrosoftCXXNameMangler mangler(*this, Out);
+  mangler.mangleName(RD);
 }
 
 MicrosoftMangleContext *
Index: lib/CodeGen/MicrosoftCXXABI.cpp
===================================================================
--- lib/CodeGen/MicrosoftCXXABI.cpp
+++ lib/CodeGen/MicrosoftCXXABI.cpp
@@ -205,6 +205,9 @@
                           CXXDtorType Type, bool ForVirtualBase,
                           bool Delegating, llvm::Value *This) override;
 
+  void emitVTableBitSetEntries(VPtrInfo *Info, const CXXRecordDecl *RD,
+                               llvm::GlobalVariable *VTable);
+
   void emitVTableDefinitions(CodeGenVTables &CGVT,
                              const CXXRecordDecl *RD) override;
 
@@ -1401,6 +1404,58 @@
                           getFromDtorType(Type));
 }
 
+void MicrosoftCXXABI::emitVTableBitSetEntries(VPtrInfo *Info,
+                                              const CXXRecordDecl *RD,
+                                              llvm::GlobalVariable *VTable) {
+  if (!getContext().getLangOpts().Sanitize.has(SanitizerKind::CFIVCall) &&
+      !getContext().getLangOpts().Sanitize.has(SanitizerKind::CFINVCall) &&
+      !getContext().getLangOpts().Sanitize.has(SanitizerKind::CFIDerivedCast) &&
+      !getContext().getLangOpts().Sanitize.has(SanitizerKind::CFIUnrelatedCast))
+    return;
+
+  llvm::NamedMDNode *BitsetsMD =
+      CGM.getModule().getOrInsertNamedMetadata("llvm.bitsets");
+  CharUnits PointerWidth = getContext().toCharUnitsFromBits(
+      getContext().getTargetInfo().getPointerWidth(0));
+
+  // FIXME: Add blacklisting scheme.
+
+  if (Info->PathToBaseWithVPtr.empty()) {
+    BitsetsMD->addOperand(
+        CGM.CreateVTableBitSetEntry(VTable, PointerWidth, RD));
+    return;
+  }
+
+  // Add a bitset entry for the least derived base belonging to this vftable.
+  BitsetsMD->addOperand(CGM.CreateVTableBitSetEntry(
+      VTable, PointerWidth, Info->PathToBaseWithVPtr.back()));
+
+  // Add a bitset entry for each derived class that is laid out at the same
+  // offset as the least derived base.
+  for (unsigned I = Info->PathToBaseWithVPtr.size() - 1; I != 0; --I) {
+    const CXXRecordDecl *DerivedRD = Info->PathToBaseWithVPtr[I - 1];
+    const CXXRecordDecl *BaseRD = Info->PathToBaseWithVPtr[I];
+
+    const ASTRecordLayout &Layout =
+        getContext().getASTRecordLayout(DerivedRD);
+    CharUnits Offset;
+    auto VBI = Layout.getVBaseOffsetsMap().find(BaseRD);
+    if (VBI == Layout.getVBaseOffsetsMap().end())
+      Offset = Layout.getBaseClassOffset(BaseRD);
+    else
+      Offset = VBI->second.VBaseOffset;
+    if (!Offset.isZero())
+      return;
+    BitsetsMD->addOperand(
+        CGM.CreateVTableBitSetEntry(VTable, PointerWidth, DerivedRD));
+  }
+
+  // Finally do the same for the most derived class.
+  if (Info->FullOffsetInMDC.isZero())
+    BitsetsMD->addOperand(
+        CGM.CreateVTableBitSetEntry(VTable, PointerWidth, RD));
+}
+
 void MicrosoftCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
                                             const CXXRecordDecl *RD) {
   MicrosoftVTableContext &VFTContext = CGM.getMicrosoftVTableContext();
@@ -1423,6 +1478,8 @@
         VTLayout.getNumVTableThunks(), RTTI);
 
     VTable->setInitializer(Init);
+
+    emitVTableBitSetEntries(Info, RD, VTable);
   }
 }
 
@@ -1585,6 +1642,49 @@
   return VTable;
 }
 
+// Compute the identity of the most derived class whose virtual table is located
+// at the given offset into RD.
+static const CXXRecordDecl *getClassAtVTableLocation(ASTContext &Ctx,
+                                                     const CXXRecordDecl *RD,
+                                                     CharUnits Offset) {
+  if (Offset.isZero())
+    return RD;
+
+  const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD);
+  const CXXRecordDecl *MaxBase = nullptr;
+  CharUnits MaxBaseOffset;
+  for (auto &&B : RD->bases()) {
+    const CXXRecordDecl *Base = B.getType()->getAsCXXRecordDecl();
+    CharUnits BaseOffset = Layout.getBaseClassOffset(Base);
+    if (BaseOffset <= Offset && BaseOffset > MaxBaseOffset) {
+      MaxBase = Base;
+      MaxBaseOffset = BaseOffset;
+    }
+  }
+  for (auto &&B : RD->vbases()) {
+    const CXXRecordDecl *Base = B.getType()->getAsCXXRecordDecl();
+    CharUnits BaseOffset = Layout.getVBaseClassOffset(Base);
+    if (BaseOffset <= Offset && BaseOffset > MaxBaseOffset) {
+      MaxBase = Base;
+      MaxBaseOffset = BaseOffset;
+    }
+  }
+  assert(MaxBase);
+  return getClassAtVTableLocation(Ctx, MaxBase, Offset - MaxBaseOffset);
+}
+
+// Compute the identity of the most derived class whose virtual table is located
+// at the MethodVFTableLocation ML.
+static const CXXRecordDecl *
+getClassAtVTableLocation(ASTContext &Ctx, GlobalDecl GD,
+                         MicrosoftVTableContext::MethodVFTableLocation &ML) {
+  const CXXRecordDecl *RD = ML.VBase;
+  if (!RD)
+    RD = cast<CXXMethodDecl>(GD.getDecl())->getParent();
+
+  return getClassAtVTableLocation(Ctx, RD, ML.VFPtrOffset);
+}
+
 llvm::Value *MicrosoftCXXABI::getVirtualFunctionPointer(CodeGenFunction &CGF,
                                                         GlobalDecl GD,
                                                         llvm::Value *This,
@@ -1600,6 +1700,10 @@
 
   MicrosoftVTableContext::MethodVFTableLocation ML =
       CGM.getMicrosoftVTableContext().getMethodVFTableLocation(GD);
+  if (CGF.SanOpts.has(SanitizerKind::CFIVCall))
+    CGF.EmitVTablePtrCheck(getClassAtVTableLocation(getContext(), GD, ML),
+                           VTable, CodeGenFunction::CFITCK_VCall, Loc);
+
   llvm::Value *VFuncPtr =
       Builder.CreateConstInBoundsGEP1_64(VTable, ML.Index, "vfn");
   return Builder.CreateLoad(VFuncPtr);
Index: test/CodeGenCXX/cfi-vcall.cpp
===================================================================
--- test/CodeGenCXX/cfi-vcall.cpp
+++ test/CodeGenCXX/cfi-vcall.cpp
@@ -1,6 +1,14 @@
-// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=NDIAG %s
-// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=DIAG --check-prefix=DIAG-ABORT %s
-// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-vcall -fsanitize-recover=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=DIAG --check-prefix=DIAG-RECOVER %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=ITANIUM --check-prefix=NDIAG %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=ITANIUM --check-prefix=DIAG --check-prefix=DIAG-ABORT %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-vcall -fsanitize-recover=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=ITANIUM --check-prefix=DIAG --check-prefix=DIAG-RECOVER %s
+// RUN: %clang_cc1 -triple x86_64-pc-windows-msvc -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=MS --check-prefix=NDIAG %s
+
+// MS: @[[VTA:[0-9]*]] {{.*}} comdat($"\01??_7A@@6B@")
+// MS: @[[VTB:[0-9]*]] {{.*}} comdat($"\01??_7B@@6B0@@")
+// MS: @[[VTAinB:[0-9]*]] {{.*}} comdat($"\01??_7B@@6BA@@@")
+// MS: @[[VTAinC:[0-9]*]] {{.*}} comdat($"\01??_7C@@6B@")
+// MS: @[[VTBinD:[0-9]*]] {{.*}} comdat($"\01??_7D@?A@@6BB@@@")
+// MS: @[[VTAinBinD:[0-9]*]] {{.*}} comdat($"\01??_7D@?A@@6BA@@@")
 
 struct A {
   A();
@@ -9,6 +17,8 @@
 
 struct B : virtual A {
   B();
+  virtual void g();
+  virtual void h();
 };
 
 struct C : virtual A {
@@ -20,6 +30,7 @@
 struct D : B, C {
   D();
   virtual void f();
+  virtual void h();
 };
 
 }
@@ -32,16 +43,24 @@
 void A::f() {
 }
 
+void B::g() {
+}
+
 void D::f() {
 }
 
+void D::h() {
+}
+
 // DIAG: @[[SRC:.*]] = private unnamed_addr constant [{{.*}} x i8] c"{{.*}}test/CodeGenCXX/cfi-vcall.cpp\00", align 1
 // DIAG: @[[TYPE:.*]] = private unnamed_addr constant { i16, i16, [4 x i8] } { i16 -1, i16 0, [4 x i8] c"'A'\00" }
-// DIAG: @[[BADTYPESTATIC:.*]] = private unnamed_addr global { { [{{.*}} x i8]*, i32, i32 }, { i16, i16, [4 x i8] }*, i8 } { { [{{.*}} x i8]*, i32, i32 } { [{{.*}} x i8]* @[[SRC]], i32 58, i32 3 }, { i16, i16, [4 x i8] }* @[[TYPE]], i8 0 }
+// DIAG: @[[BADTYPESTATIC:.*]] = private unnamed_addr global { { [{{.*}} x i8]*, i32, i32 }, { i16, i16, [4 x i8] }*, i8 } { { [{{.*}} x i8]*, i32, i32 } { [{{.*}} x i8]* @[[SRC]], i32 [[@LINE+20]], i32 3 }, { i16, i16, [4 x i8] }* @[[TYPE]], i8 0 }
 
-// CHECK: define void @_Z2afP1A
+// ITANIUM: define void @_Z2afP1A
+// MS: define void @"\01?af@@YAXPEAUA@@@Z"
 void af(A *a) {
-  // CHECK: [[P:%[^ ]*]] = call i1 @llvm.bitset.test(i8* [[VT:%[^ ]*]], metadata !"1A")
+  // ITANIUM: [[P:%[^ ]*]] = call i1 @llvm.bitset.test(i8* [[VT:%[^ ]*]], metadata !"1A")
+  // MS: [[P:%[^ ]*]] = call i1 @llvm.bitset.test(i8* [[VT:%[^ ]*]], metadata !"A@@")
   // CHECK-NEXT: br i1 [[P]], label %[[CONTBB:[^ ,]*]], label %[[TRAPBB:[^ ,]*]]
 
   // CHECK: [[TRAPBB]]
@@ -58,20 +77,40 @@
   a->f();
 }
 
-// CHECK: define internal void @_Z3df1PN12_GLOBAL__N_11DE
+// ITANIUM: define internal void @_Z3df1PN12_GLOBAL__N_11DE
+// MS: define internal void @"\01?df1@@YAXPEAUD@?A@@@Z"
 void df1(D *d) {
-  // CHECK: {{%[^ ]*}} = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"[{{.*}}cfi-vcall.cpp]N12_GLOBAL__N_11DE")
+  // ITANIUM: {{%[^ ]*}} = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"[{{.*}}cfi-vcall.cpp]N12_GLOBAL__N_11DE")
+  // MS: {{%[^ ]*}} = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"A@@")
   d->f();
 }
 
-// CHECK: define internal void @_Z3df2PN12_GLOBAL__N_11DE
+// ITANIUM: define internal void @_Z3dg1PN12_GLOBAL__N_11DE
+// MS: define internal void @"\01?dg1@@YAXPEAUD@?A@@@Z"
+void dg1(D *d) {
+  // ITANIUM: {{%[^ ]*}} = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"1B")
+  // MS: {{%[^ ]*}} = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"B@@")
+  d->g();
+}
+
+// ITANIUM: define internal void @_Z3dh1PN12_GLOBAL__N_11DE
+// MS: define internal void @"\01?dh1@@YAXPEAUD@?A@@@Z"
+void dh1(D *d) {
+  // ITANIUM: {{%[^ ]*}} = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"[{{.*}}cfi-vcall.cpp]N12_GLOBAL__N_11DE")
+  // MS: {{%[^ ]*}} = call i1 @llvm.bitset.test(i8* {{%[^ ]*}}, metadata !"[{{.*}}cfi-vcall.cpp]D@?A@@")
+  d->h();
+}
+
+// ITANIUM: define internal void @_Z3df2PN12_GLOBAL__N_11DE
+// MS: define internal void @"\01?df2@@YAXPEAUD@?A@@@Z"
 __attribute__((no_sanitize("cfi")))
 void df2(D *d) {
   // CHECK-NOT: call i1 @llvm.bitset.test
   d->f();
 }
 
-// CHECK: define internal void @_Z3df3PN12_GLOBAL__N_11DE
+// ITANIUM: define internal void @_Z3df3PN12_GLOBAL__N_11DE
+// MS: define internal void @"\01?df3@@YAXPEAUD@?A@@@Z"
 __attribute__((no_sanitize("address"))) __attribute__((no_sanitize("cfi-vcall")))
 void df3(D *d) {
   // CHECK-NOT: call i1 @llvm.bitset.test
@@ -82,20 +121,33 @@
 
 void foo() {
   df1(&d);
+  dg1(&d);
+  dh1(&d);
   df2(&d);
   df3(&d);
 }
 
-// CHECK-DAG: !{!"1A", [3 x i8*]* @_ZTV1A, i64 16}
-// CHECK-DAG: !{!"1A", [5 x i8*]* @_ZTCN12_GLOBAL__N_11DE0_1B, i64 32}
-// CHECK-DAG: !{!"1B", [5 x i8*]* @_ZTCN12_GLOBAL__N_11DE0_1B, i64 32}
-// CHECK-DAG: !{!"1A", [9 x i8*]* @_ZTCN12_GLOBAL__N_11DE8_1C, i64 64}
-// CHECK-DAG: !{!"1C", [9 x i8*]* @_ZTCN12_GLOBAL__N_11DE8_1C, i64 32}
-// CHECK-DAG: !{!"1A", [10 x i8*]* @_ZTVN12_GLOBAL__N_11DE, i64 32}
-// CHECK-DAG: !{!"1B", [10 x i8*]* @_ZTVN12_GLOBAL__N_11DE, i64 32}
-// CHECK-DAG: !{!"1C", [10 x i8*]* @_ZTVN12_GLOBAL__N_11DE, i64 72}
-// CHECK-DAG: !{!"[{{.*}}cfi-vcall.cpp]N12_GLOBAL__N_11DE", [10 x i8*]* @_ZTVN12_GLOBAL__N_11DE, i64 32}
-// CHECK-DAG: !{!"1A", [5 x i8*]* @_ZTV1B, i64 32}
-// CHECK-DAG: !{!"1B", [5 x i8*]* @_ZTV1B, i64 32}
-// CHECK-DAG: !{!"1A", [5 x i8*]* @_ZTV1C, i64 32}
-// CHECK-DAG: !{!"1C", [5 x i8*]* @_ZTV1C, i64 32}
+// Check for the expected number of elements (7 or 13 respectively).
+// MS: !llvm.bitsets = !{[[X:[^,]*(,[^,]*){6}]]}
+// ITANIUM: !llvm.bitsets = !{[[X:[^,]*(,[^,]*){12}]]}
+
+// ITANIUM-DAG: !{!"1A", [3 x i8*]* @_ZTV1A, i64 16}
+// ITANIUM-DAG: !{!"1A", [7 x i8*]* @_ZTCN12_GLOBAL__N_11DE0_1B, i64 32}
+// ITANIUM-DAG: !{!"1B", [7 x i8*]* @_ZTCN12_GLOBAL__N_11DE0_1B, i64 32}
+// ITANIUM-DAG: !{!"1A", [9 x i8*]* @_ZTCN12_GLOBAL__N_11DE8_1C, i64 64}
+// ITANIUM-DAG: !{!"1C", [9 x i8*]* @_ZTCN12_GLOBAL__N_11DE8_1C, i64 32}
+// ITANIUM-DAG: !{!"1A", [12 x i8*]* @_ZTVN12_GLOBAL__N_11DE, i64 32}
+// ITANIUM-DAG: !{!"1B", [12 x i8*]* @_ZTVN12_GLOBAL__N_11DE, i64 32}
+// ITANIUM-DAG: !{!"1C", [12 x i8*]* @_ZTVN12_GLOBAL__N_11DE, i64 88}
+// ITANIUM-DAG: !{!"[{{.*}}cfi-vcall.cpp]N12_GLOBAL__N_11DE", [12 x i8*]* @_ZTVN12_GLOBAL__N_11DE, i64 32}
+// ITANIUM-DAG: !{!"1A", [7 x i8*]* @_ZTV1B, i64 32}
+// ITANIUM-DAG: !{!"1B", [7 x i8*]* @_ZTV1B, i64 32}
+// ITANIUM-DAG: !{!"1A", [5 x i8*]* @_ZTV1C, i64 32}
+// ITANIUM-DAG: !{!"1C", [5 x i8*]* @_ZTV1C, i64 32}
+// MS-DAG: !{!"A@@", [2 x i8*]* @[[VTA]], i64 8}
+// MS-DAG: !{!"B@@", [3 x i8*]* @[[VTB]], i64 8}
+// MS-DAG: !{!"A@@", [2 x i8*]* @[[VTAinB]], i64 8}
+// MS-DAG: !{!"A@@", [2 x i8*]* @[[VTAinC]], i64 8}
+// MS-DAG: !{!"B@@", [3 x i8*]* @[[VTBinD]], i64 8}
+// MS-DAG: !{!"[{{.*}}cfi-vcall.cpp]D@?A@@", [3 x i8*]* @[[VTBinD]], i64 8}
+// MS-DAG: !{!"A@@", [2 x i8*]* @[[VTAinBinD]], i64 8}