diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index 7da7554..52e7d04 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -259,7 +259,7 @@
   if (NumBytes > 1)
     Ty = llvm::ArrayType::get(Ty, NumBytes);
 
-  llvm::Constant *C = llvm::Constant::getNullValue(Ty);
+  llvm::Constant *C = llvm::UndefValue::get(Ty);
   Elements.push_back(C);
   assert(getAlignment(C) == 1 && "Padding must have 1 byte alignment!");
 
@@ -297,7 +297,7 @@
       if (NumBytes > 1)
         Ty = llvm::ArrayType::get(Ty, NumBytes);
 
-      llvm::Constant *Padding = llvm::Constant::getNullValue(Ty);
+      llvm::Constant *Padding = llvm::UndefValue::get(Ty);
       PackedElements.push_back(Padding);
       ElementOffsetInBytes += getSizeInBytes(Padding);
     }
@@ -537,7 +537,7 @@
         if (NumPadBytes > 1)
           Ty = llvm::ArrayType::get(Ty, NumPadBytes);
 
-        Elts.push_back(llvm::Constant::getNullValue(Ty));
+        Elts.push_back(llvm::UndefValue::get(Ty));
         Types.push_back(Ty);
       }
 
diff --git a/test/CodeGen/decl.c b/test/CodeGen/decl.c
index 0c7ef5f..8bbeb24 100644
--- a/test/CodeGen/decl.c
+++ b/test/CodeGen/decl.c
@@ -2,7 +2,7 @@
 
 // CHECK: @test1.x = internal constant [12 x i32] [i32 1
 // CHECK: @test2.x = internal constant [13 x i32] [i32 1,
-// CHECK: @test5w = global %0 { i32 2, [4 x i8] zeroinitializer }
+// CHECK: @test5w = global %0 { i32 2, [4 x i8] undef }
 // CHECK: @test5y = global %union.test5u { double 7.300000e+0{{[0]*}}1 }
 
 // CHECK: @test6.x = internal constant %struct.SelectDest { i8 1, i8 2, i32 3, i32 0 }
diff --git a/test/CodeGen/designated-initializers.c b/test/CodeGen/designated-initializers.c
index 652238f..1ad5e6c 100644
--- a/test/CodeGen/designated-initializers.c
+++ b/test/CodeGen/designated-initializers.c
@@ -1,22 +1,34 @@
-// RUN: %clang_cc1 -triple i386-unknown-unknown %s -emit-llvm -o %t
-// RUN: grep "{ i8\* null, i32 1024 }" %t
-// RUN: grep "i32 0, i32 22" %t
+// RUN: %clang_cc1 -triple i386-unknown-unknown %s -emit-llvm -o - | FileCheck %s
 
 struct foo {
     void *a;
     int b;
 };
 
+// CHECK: @u = global %union.anon zeroinitializer
 union { int i; float f; } u = { };
 
+// CHECK: @u2 = global %0 { i32 0, [4 x i8] undef }
+union { int i; double f; } u2 = { };
+
+// CHECK: @b = global [2 x i32] [i32 0, i32 22]
+int b[2] = {
+  [1] = 22
+};
+
 int main(int argc, char **argv)
 {
-  union { int i; float f; } u2 = { };
-    static struct foo foo = {
-        .b = 1024,
-    };
-}
+  // CHECK: internal global %struct.foo { i8* null, i32 1024 }
+  static struct foo foo = {
+    .b = 1024,
+  };
 
-int b[2] = {
-    [1] 22
-};
+  // CHECK: bitcast %union.anon* %u2
+  // CHECK: call void @llvm.memset
+   union { int i; float f; } u2 = { };
+
+  // CHECK-NOT: call void @llvm.memset
+  union { int i; float f; } u3;
+
+  // CHECK: ret i32
+}
diff --git a/test/CodeGen/global-init.c b/test/CodeGen/global-init.c
index e166fb4..651f7d8 100644
--- a/test/CodeGen/global-init.c
+++ b/test/CodeGen/global-init.c
@@ -12,19 +12,28 @@
 // CHECK: @c = weak global i32 0
 
 
-
 // Since this is marked const, it should get weak_odr linkage, since all
 // definitions have to be the same.
 // CHECK: @d = weak_odr constant i32 0
 const int d __attribute__((weak))= 0;
 
+// PR6168 "too many undefs"
+struct ManyFields {
+  int a;
+  int b;
+  int c;
+  char d;
+  int e;
+  int f;
+};
+
+// CHECK: global %0 { i32 1, i32 2, i32 0, i8 0, i32 0, i32 0 }
+struct ManyFields FewInits = {1, 2};
 
 
 // NOTE: tentative definitions are processed at the end of the translation unit.
 
 // This shouldn't be emitted as common because it has an explicit section.
 // rdar://7119244
-int b __attribute__((section("foo")));
-
 // CHECK: @b = global i32 0, section "foo"
-
+int b __attribute__((section("foo")));
diff --git a/test/CodeGen/union-init2.c b/test/CodeGen/union-init2.c
index bd56f9e..1386c27 100644
--- a/test/CodeGen/union-init2.c
+++ b/test/CodeGen/union-init2.c
@@ -1,7 +1,13 @@
 // RUN: %clang_cc1 -emit-llvm %s -o - -triple i686-pc-linux-gnu | FileCheck %s
 
 // Make sure we generate something sane instead of a ptrtoint
+// CHECK: bitcast (%0* @r to %union.x*), [4 x i8] undef
 union x {long long b;union x* a;} r = {.a = &r};
 
 
-// CHECK: bitcast (%0* @r to %union.x*), [4 x i8] zero
\ No newline at end of file
+// CHECK: global %1 { [3 x i8] zeroinitializer, [5 x i8] undef }
+union z {
+  char a[3];
+  long long b;
+};
+union z y = {};