diff --git a/include/llvm/GlobalValue.h b/include/llvm/GlobalValue.h
index 81a11a4c925..d43a2fa227c 100644
--- a/include/llvm/GlobalValue.h
+++ b/include/llvm/GlobalValue.h
@@ -192,6 +192,14 @@ public:
            Linkage == LinkerPrivateWeakDefAutoLinkage;
   }
 
+  /// mayBeRemovedByLinker - Whether the definition of this global may be
+  /// removed at link time.
+  static bool mayBeRemovedByLinker(LinkageTypes Linkage) {
+    return isLinkerPrivateLinkage(Linkage) ||
+      isLinkerPrivateWeakLinkage(Linkage) ||
+      isLinkerPrivateWeakDefAutoLinkage(Linkage);
+  }
+
   bool hasExternalLinkage() const { return isExternalLinkage(Linkage); }
   bool hasAvailableExternallyLinkage() const {
     return isAvailableExternallyLinkage(Linkage);
@@ -225,6 +233,8 @@ public:
 
   bool isWeakForLinker() const { return isWeakForLinker(Linkage); }
 
+  bool mayBeRemovedByLinker() const { return mayBeRemovedByLinker(Linkage); }
+
   /// copyAttributesFrom - copy all additional attributes (those not needed to
   /// create a GlobalValue) from the GlobalValue Src to this one.
   virtual void copyAttributesFrom(const GlobalValue *Src);
diff --git a/lib/Transforms/IPO/ConstantMerge.cpp b/lib/Transforms/IPO/ConstantMerge.cpp
index c3ecb7afff7..268a281aae4 100644
--- a/lib/Transforms/IPO/ConstantMerge.cpp
+++ b/lib/Transforms/IPO/ConstantMerge.cpp
@@ -140,18 +140,21 @@ bool ConstantMerge::runOnModule(Module &M) {
           UsedGlobals.count(GV))
         continue;
 
+      // Ignore any constants which may be removed by the linker.
+      if (GV->mayBeRemovedByLinker())
+        continue;
+
       Constant *Init = GV->getInitializer();
 
       // Check to see if the initializer is already known.
       PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
       GlobalVariable *&Slot = CMap[Pair];
 
-      // If this is the first constant we find or if the old on is local,
-      // replace with the current one. It the current is externally visible
+      // If this is the first constant we find or if the old one is local,
+      // replace with the current one. If the current is externally visible
       // it cannot be replace, but can be the canonical constant we merge with.
-      if (Slot == 0 || IsBetterCannonical(*GV, *Slot)) {
+      if (Slot == 0 || IsBetterCannonical(*GV, *Slot))
         Slot = GV;
-      }
     }
 
     // Second: identify all globals that can be merged together, filling in
@@ -169,8 +172,9 @@ bool ConstantMerge::runOnModule(Module &M) {
           UsedGlobals.count(GV))
         continue;
 
-      // We can only replace constant with local linkage.
-      if (!GV->hasLocalLinkage())
+      // We can only replace constants with local linkage and which aren't
+      // removed by the linker.
+      if (!GV->hasLocalLinkage() || GV->mayBeRemovedByLinker())
         continue;
 
       Constant *Init = GV->getInitializer();
diff --git a/test/Transforms/ConstantMerge/linker-private.ll b/test/Transforms/ConstantMerge/linker-private.ll
new file mode 100644
index 00000000000..eba7880e8af
--- /dev/null
+++ b/test/Transforms/ConstantMerge/linker-private.ll
@@ -0,0 +1,23 @@
+; RUN: opt < %s -constmerge -S | FileCheck %s
+; <rdar://problem/10564621>
+
+%0 = type opaque
+%struct.NSConstantString = type { i32*, i32, i8*, i32 }
+
+; CHECK: @.str3 = linker_private unnamed_addr constant [1 x i8] zeroinitializer, align 1
+
+@isLogVisible = global i8 0, align 1
+@__CFConstantStringClassReference = external global [0 x i32]
+@.str3 = linker_private unnamed_addr constant [1 x i8] zeroinitializer, align 1
+@_unnamed_cfstring_4 = private constant %struct.NSConstantString { i32* getelementptr inbounds ([0 x i32]* @__CFConstantStringClassReference, i32 0, i32 0), i32 1992, i8* getelementptr inbounds ([1 x i8]* @.str3, i32 0, i32 0), i32 0 }, section "__DATA,__cfstring"
+@null.array = weak_odr constant [1 x i8] zeroinitializer, align 1
+
+define linkonce_odr void @bar() nounwind ssp align 2 {
+entry:
+  %stack = alloca i8*, align 4
+  %call = call %0* bitcast (i8* (i8*, i8*, ...)* @objc_msgSend to %0* (i8*, i8*, %0*)*)(i8* null, i8* null, %0* bitcast (%struct.NSConstantString* @_unnamed_cfstring_4 to %0*))
+  store i8* getelementptr inbounds ([1 x i8]* @null.array, i32 0, i32 0), i8** %stack, align 4
+  ret void
+}
+
+declare i8* @objc_msgSend(i8*, i8*, ...) nonlazybind