Index: lib/CodeGen/CGExpr.cpp
===================================================================
--- lib/CodeGen/CGExpr.cpp
+++ lib/CodeGen/CGExpr.cpp
@@ -3892,6 +3892,23 @@
   return EmitLValueForField(LambdaLV, Field);
 }
 
+/// Get the field index in the debug info. The debug info structure/union
+/// will ignore the unnamed bitfields.
+unsigned CodeGenFunction::getDebugInfoFIndex(const RecordDecl *Rec,
+                                             unsigned FieldIndex) {
+  unsigned I = 0, Skipped = 0;
+
+  for (auto F : Rec->getDefinition()->fields()) {
+    if (I == FieldIndex)
+      break;
+    if (F->isUnnamedBitfield())
+      Skipped++;
+    I++;
+  }
+
+  return FieldIndex - Skipped;
+}
+
 /// Get the address of a zero-sized field within a record. The resulting
 /// address doesn't necessarily have the right type.
 static Address emitAddrOfZeroSizeField(CodeGenFunction &CGF, Address Base,
@@ -3931,7 +3948,7 @@
       CGF.CGM.getTypes().getCGRecordLayout(rec).getLLVMFieldNo(field);
 
   return CGF.Builder.CreatePreserveStructAccessIndex(
-      base, idx, field->getFieldIndex(), DbgInfo);
+      base, idx, CGF.getDebugInfoFIndex(rec, field->getFieldIndex()), DbgInfo);
 }
 
 static bool hasAnyVptr(const QualType Type, const ASTContext &Context) {
@@ -4048,7 +4065,7 @@
           getContext().getRecordType(rec), rec->getLocation());
       addr = Address(
           Builder.CreatePreserveUnionAccessIndex(
-              addr.getPointer(), field->getFieldIndex(), DbgInfo),
+              addr.getPointer(), getDebugInfoFIndex(rec, field->getFieldIndex()), DbgInfo),
           addr.getAlignment());
     }
   } else {
Index: lib/CodeGen/CodeGenFunction.h
===================================================================
--- lib/CodeGen/CodeGenFunction.h
+++ lib/CodeGen/CodeGenFunction.h
@@ -2652,6 +2652,9 @@
   /// Converts Location to a DebugLoc, if debug information is enabled.
   llvm::DebugLoc SourceLocToDebugLoc(SourceLocation Location);
 
+  /// Get the record field index as represented in debug info.
+  unsigned getDebugInfoFIndex(const RecordDecl *Rec, unsigned FieldIndex);
+
 
   //===--------------------------------------------------------------------===//
   //                            Declaration Emission
Index: test/CodeGen/builtin-preserve-access-index.c
===================================================================
--- /dev/null
+++ test/CodeGen/builtin-preserve-access-index.c
@@ -0,0 +1,177 @@
+// RUN: %clang -target x86_64 -emit-llvm -S -g %s -o - | FileCheck %s
+
+#define _(x) (__builtin_preserve_access_index(x))
+
+const void *unit1(const void *arg) {
+  return _(arg);
+}
+// CHECK: define dso_local i8* @unit1(i8* %arg)
+// CHECK-NOT: llvm.preserve.array.access.index
+// CHECK-NOT: llvm.preserve.struct.access.index
+// CHECK-NOT: llvm.preserve.union.access.index
+
+const void *unit2(void) {
+  return _((const void *)0xffffffffFFFF0000ULL);
+}
+// CHECK: define dso_local i8* @unit2()
+// CHECK-NOT: llvm.preserve.array.access.index
+// CHECK-NOT: llvm.preserve.struct.access.index
+// CHECK-NOT: llvm.preserve.union.access.index
+
+const void *unit3(const int *arg) {
+  return _(arg + 1);
+}
+// CHECK: define dso_local i8* @unit3(i32* %arg)
+// CHECK-NOT: llvm.preserve.array.access.index
+// CHECK-NOT: llvm.preserve.struct.access.index
+// CHECK-NOT: llvm.preserve.union.access.index
+
+const void *unit4(const int *arg) {
+  return _(&arg[1]);
+}
+// CHECK: define dso_local i8* @unit4(i32* %arg)
+// CHECK-NOT: getelementptr
+// CHECK: call i32* @llvm.preserve.array.access.index.p0i32.p0i32(i32* %0, i32 0, i32 1)
+
+const void *unit5(const int *arg[5]) {
+  return _(&arg[1][2]);
+}
+// CHECK: define dso_local i8* @unit5(i32** %arg)
+// CHECK-NOT: getelementptr
+// CHECK: call i32** @llvm.preserve.array.access.index.p0p0i32.p0p0i32(i32** %0, i32 0, i32 1)
+// CHECK-NOT: getelementptr
+// CHECK: call i32* @llvm.preserve.array.access.index.p0i32.p0i32(i32* %2, i32 0, i32 2)
+
+struct s1 {
+  char a;
+  int b;
+};
+
+struct s2 {
+  char a1:1;
+  char a2:1;
+  int b;
+};
+
+struct s3 {
+  char a1:1;
+  char a2:1;
+  char :6;
+  int b;
+};
+
+const void *unit6(struct s1 *arg) {
+  return _(&arg->a);
+}
+// CHECK: define dso_local i8* @unit6(%struct.s1* %arg)
+// CHECK-NOT: getelementptr
+// CHECK: call i8* @llvm.preserve.struct.access.index.p0i8.p0s_struct.s1s(%struct.s1* %0, i32 0, i32 0), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[STRUCT_S1:[0-9]+]]
+
+const void *unit7(struct s1 *arg) {
+  return _(&arg->b);
+}
+// CHECK: define dso_local i8* @unit7(%struct.s1* %arg)
+// CHECK-NOT: getelementptr
+// CHECK: call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.s1s(%struct.s1* %0, i32 1, i32 1), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[STRUCT_S1]]
+
+const void *unit8(struct s2 *arg) {
+  return _(&arg->b);
+}
+// CHECK: define dso_local i8* @unit8(%struct.s2* %arg)
+// CHECK-NOT: getelementptr
+// CHECK: call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.s2s(%struct.s2* %0, i32 1, i32 2), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[STRUCT_S2:[0-9]+]]
+
+const void *unit9(struct s3 *arg) {
+  return _(&arg->b);
+}
+// CHECK: define dso_local i8* @unit9(%struct.s3* %arg)
+// CHECK-NOT: getelementptr
+// CHECK: call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.s3s(%struct.s3* %0, i32 1, i32 2), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[STRUCT_S3:[0-9]+]]
+
+union u1 {
+  char a;
+  int b;
+};
+
+union u2 {
+  char a;
+  int :32;
+  int b;
+};
+
+const void *unit10(union u1 *arg) {
+  return _(&arg->a);
+}
+// CHECK: define dso_local i8* @unit10(%union.u1* %arg)
+// CHECK-NOT: getelementptr
+// CHECK: call %union.u1* @llvm.preserve.union.access.index.p0s_union.u1s.p0s_union.u1s(%union.u1* %0, i32 0), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[UNION_U1:[0-9]+]]
+
+const void *unit11(union u1 *arg) {
+  return _(&arg->b);
+}
+// CHECK: define dso_local i8* @unit11(%union.u1* %arg)
+// CHECK-NOT: getelementptr
+// CHECK: call %union.u1* @llvm.preserve.union.access.index.p0s_union.u1s.p0s_union.u1s(%union.u1* %0, i32 1), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[UNION_U1]]
+
+const void *unit12(union u2 *arg) {
+  return _(&arg->b);
+}
+// CHECK: define dso_local i8* @unit12(%union.u2* %arg)
+// CHECK-NOT: getelementptr
+// CHECK: call %union.u2* @llvm.preserve.union.access.index.p0s_union.u2s.p0s_union.u2s(%union.u2* %0, i32 1), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[UNION_U2:[0-9]+]]
+
+struct s4 {
+  char d;
+  union u {
+    int b[4];
+    char a;
+  } c;
+};
+
+union u3 {
+  struct s {
+    int b[4];
+  } c;
+  char a;
+};
+
+const void *unit13(struct s4 *arg) {
+  return _(&arg->c.b[2]);
+}
+// CHECK: define dso_local i8* @unit13(%struct.s4* %arg)
+// CHECK: call %union.u* @llvm.preserve.struct.access.index.p0s_union.us.p0s_struct.s4s(%struct.s4* %0, i32 1, i32 1), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[STRUCT_S4:[0-9]+]]
+// CHECK: call %union.u* @llvm.preserve.union.access.index.p0s_union.us.p0s_union.us(%union.u* %1, i32 0), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[UNION_I_U:[0-9]+]]
+// CHECK: call i32* @llvm.preserve.array.access.index.p0i32.p0a4i32([4 x i32]* %b, i32 1, i32 2)
+
+const void *unit14(union u3 *arg) {
+  return _(&arg->c.b[2]);
+}
+// CHECK: define dso_local i8* @unit14(%union.u3* %arg)
+// CHECK: call %union.u3* @llvm.preserve.union.access.index.p0s_union.u3s.p0s_union.u3s(%union.u3* %0, i32 0), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[UNION_U3:[0-9]+]]
+// CHECK: call [4 x i32]* @llvm.preserve.struct.access.index.p0a4i32.p0s_struct.ss(%struct.s* %c, i32 0, i32 0), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[STRUCT_I_S:[0-9]+]]
+// CHECK: call i32* @llvm.preserve.array.access.index.p0i32.p0a4i32([4 x i32]* %2, i32 1, i32 2)
+
+const void *unit15(struct s4 *arg) {
+  return _(&arg[2].c.a);
+}
+// CHECK: define dso_local i8* @unit15(%struct.s4* %arg)
+// CHECK: call %struct.s4* @llvm.preserve.array.access.index.p0s_struct.s4s.p0s_struct.s4s(%struct.s4* %0, i32 0, i32 2)
+// CHECK: call %union.u* @llvm.preserve.struct.access.index.p0s_union.us.p0s_struct.s4s(%struct.s4* %1, i32 1, i32 1), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[STRUCT_S4]]
+// CHECK: call %union.u* @llvm.preserve.union.access.index.p0s_union.us.p0s_union.us(%union.u* %2, i32 1), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[UNION_I_U]]
+
+const void *unit16(union u3 *arg) {
+  return _(&arg[2].a);
+}
+// CHECK: define dso_local i8* @unit16(%union.u3* %arg)
+// CHECK: call %union.u3* @llvm.preserve.array.access.index.p0s_union.u3s.p0s_union.u3s(%union.u3* %0, i32 0, i32 2)
+// CHECK: call %union.u3* @llvm.preserve.union.access.index.p0s_union.u3s.p0s_union.u3s(%union.u3* %1, i32 1), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[UNION_U3]]
+
+// CHECK: ![[STRUCT_S1]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s1",
+// CHECK: ![[STRUCT_S2]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s2",
+// CHECK: ![[STRUCT_S3]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s3",
+// CHECK: ![[UNION_U1]] = distinct !DICompositeType(tag: DW_TAG_union_type, name: "u1",
+// CHECK: ![[UNION_U2]] = distinct !DICompositeType(tag: DW_TAG_union_type, name: "u2",
+// CHECK: ![[STRUCT_S4]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s4",
+// CHECK: ![[UNION_I_U]] = distinct !DICompositeType(tag: DW_TAG_union_type, name: "u",
+// CHECK: ![[UNION_U3]] = distinct !DICompositeType(tag: DW_TAG_union_type, name: "u3",
+// CHECK: ![[STRUCT_I_S]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s",
Index: test/Sema/builtin-preserve-access-index.c
===================================================================
--- /dev/null
+++ test/Sema/builtin-preserve-access-index.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -x c -triple x86_64-pc-linux-gnu -dwarf-version=4 -fsyntax-only -verify %s
+
+const void *invalid1(const int *arg) {
+  return __builtin_preserve_access_index(&arg[1], 1); // expected-error {{too many arguments to function call, expected 1, have 2}}
+}
+
+void *invalid2(const int *arg) {
+  return __builtin_preserve_access_index(&arg[1]); // expected-warning {{returning 'const void *' from a function with result type 'void *' discards qualifiers}}
+}
+
+const void *invalid3(const int *arg) {
+  return __builtin_preserve_access_index(1); // expected-warning {{incompatible integer to pointer conversion passing 'int' to parameter of type 'const void *'}}
+}