Index: lib/AST/RecordLayoutBuilder.cpp
===================================================================
--- lib/AST/RecordLayoutBuilder.cpp
+++ lib/AST/RecordLayoutBuilder.cpp
@@ -2692,7 +2692,8 @@
     auto FieldBitOffset = External.getExternalFieldOffset(FD);
     placeFieldAtBitOffset(FieldBitOffset);
     auto NewSize = Context.toCharUnitsFromBits(
-        llvm::alignTo(FieldBitOffset + Width, Context.getCharWidth()));
+        llvm::alignDown(FieldBitOffset, Context.toBits(Info.Alignment)) +
+        Context.toBits(Info.Size));
     Size = std::max(Size, NewSize);
     Alignment = std::max(Alignment, Info.Alignment);
   } else if (IsUnion) {
@@ -2741,12 +2742,17 @@
   CharUnits InjectionSite = VBPtrOffset;
   // But before we do, make sure it's properly aligned.
   VBPtrOffset = VBPtrOffset.alignTo(PointerInfo.Alignment);
+  // Determine where the first field should be laid out after the vbptr.
+  CharUnits FieldStart = VBPtrOffset + PointerInfo.Size;
   // Shift everything after the vbptr down, unless we're using an external
   // layout.
-  if (UseExternalLayout)
+  if (UseExternalLayout) {
+    // It is possible that there were no fields or bases located after vbptr,
+    // so the size was not adjusted before.
+    if (Size < FieldStart)
+      Size = FieldStart;
     return;
-  // Determine where the first field should be laid out after the vbptr.
-  CharUnits FieldStart = VBPtrOffset + PointerInfo.Size;
+  }
   // Make sure that the amount we push the fields back by is a multiple of the
   // alignment.
   CharUnits Offset = (FieldStart - InjectionSite)
@@ -2771,8 +2777,14 @@
   if (HasVBPtr)
     VBPtrOffset += Offset;
 
-  if (UseExternalLayout)
+  if (UseExternalLayout) {
+    // The class may have no bases or fields, but still have a vfptr
+    // (e.g. it's an interface class). The size was not correctly set before
+    // in this case.
+    if (FieldOffsets.empty() && Bases.empty())
+      Size += Offset;
     return;
+  }
 
   Size += Offset;
 
Index: test/CodeGenCXX/Inputs/override-bit-field-layout.layout
===================================================================
--- test/CodeGenCXX/Inputs/override-bit-field-layout.layout
+++ test/CodeGenCXX/Inputs/override-bit-field-layout.layout
@@ -14,3 +14,11 @@
   Size:128
   Alignment:64
   FieldOffsets: [64]>
+
+*** Dumping AST Record Layout
+Type: struct S3
+
+Layout: <ASTRecordLayout
+  Size:32
+  Alignment:32
+  FieldOffsets: [0, 1]>
Index: test/CodeGenCXX/Inputs/override-layout-virtual-base.layout
===================================================================
--- /dev/null
+++ test/CodeGenCXX/Inputs/override-layout-virtual-base.layout
@@ -0,0 +1,8 @@
+
+*** Dumping AST Record Layout
+Type: struct S2
+
+Layout: <ASTRecordLayout
+  Size:64
+  Alignment:64
+  FieldOffsets: []>
Index: test/CodeGenCXX/override-bit-field-layout.cpp
===================================================================
--- test/CodeGenCXX/override-bit-field-layout.cpp
+++ test/CodeGenCXX/override-bit-field-layout.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -w -fdump-record-layouts-simple -foverride-record-layout=%S/Inputs/override-bit-field-layout.layout %s | FileCheck %s
+// RUN: %clang_cc1 -w -triple=x86_64-pc-win32 -fms-compatibility -fdump-record-layouts-simple -foverride-record-layout=%S/Inputs/override-bit-field-layout.layout %s | FileCheck %s
 
 // CHECK: Type: struct S1
 // CHECK:   FieldOffsets: [0, 11]
@@ -14,7 +14,23 @@
   short a : 3;
 };
 
+// CHECK: Type: struct S3
+// CHECK:   Size:32
+// CHECK:   FieldOffsets: [0, 1]
+struct S3 {
+  int a : 1;
+  int b : 2;
+};
+
+// CHECK: Type: struct S4
+// CHECK:   FieldOffsets: [32]
+struct S4 : S3 {
+  char c;
+};
+
 void use_structs() {
   S1 s1s[sizeof(S1)];
   S2 s2s[sizeof(S2)];
+  S3 s3s[sizeof(S3)];
+  S4 s4s[sizeof(S4)];
 }
Index: test/CodeGenCXX/override-layout-virtual-base.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/override-layout-virtual-base.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -w -triple=x86_64-pc-win32 -fms-compatibility -fdump-record-layouts-simple -foverride-record-layout=%S/Inputs/override-layout-virtual-base.layout %s | FileCheck %s
+
+struct S1 {
+  int a;
+};
+
+struct S2 : virtual S1 {
+  virtual void foo() {}
+};
+
+// CHECK: Type: struct S3
+// CHECK:   FieldOffsets: [128]
+struct S3 : S2 {
+  char b;
+};
+
+void use_structs() {
+  S1 s1s[sizeof(S1)];
+  S2 s2s[sizeof(S2)];
+  S3 s3s[sizeof(S3)];
+}