diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 9ca078d..d27acf7 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -630,6 +630,9 @@
   "auto property synthesis will not synthesize property"
   " declared in a protocol">,
   InGroup<DiagGroup<"objc-protocol-property-synthesis">>;
+def warn_autosynthesis_property_ivar_match :Warning<
+  "auto autosynthesized property has same name as an existing ivar">,
+  InGroup<DiagGroup<"objc-autosynthesis-property-ivar-name-match">>;
 def warn_missing_explicit_synthesis : Warning <
   "auto property synthesis is synthesizing property not explicitly synthesized">,
   InGroup<DiagGroup<"objc-missing-property-synthesis">>, DefaultIgnore;
diff --git a/lib/Sema/SemaObjCProperty.cpp b/lib/Sema/SemaObjCProperty.cpp
index 84dc9ca..20dbf58 100644
--- a/lib/Sema/SemaObjCProperty.cpp
+++ b/lib/Sema/SemaObjCProperty.cpp
@@ -755,6 +755,22 @@
     }
 
     if (!Ivar) {
+      if (AtLoc.isInvalid()) {
+        // Check when default synthesizing a property that there is 
+        // an ivar matching property name and issue warning; since this
+        // is the most common case of not using an ivar used for backing
+        // property in non-default synthesis case.
+        ObjCInterfaceDecl *ClassDeclared=0;
+        ObjCIvarDecl *originalIvar = 
+          IDecl->lookupInstanceVariable(property->getIdentifier(), 
+                                        ClassDeclared);
+        if (originalIvar) {
+          Diag(PropertyDiagLoc, 
+               diag::warn_autosynthesis_property_ivar_match);
+          Diag(property->getLocation(), diag::note_property_declare);
+          Diag(originalIvar->getLocation(), diag::note_ivar_decl);
+        }
+      }
       // In ARC, give the ivar a lifetime qualifier based on the
       // property attributes.
       if (getLangOpts().ObjCAutoRefCount &&
diff --git a/test/SemaObjC/default-synthesize-2.m b/test/SemaObjC/default-synthesize-2.m
index b95f263..eeeab5f 100644
--- a/test/SemaObjC/default-synthesize-2.m
+++ b/test/SemaObjC/default-synthesize-2.m
@@ -41,12 +41,13 @@
 // Test3
 @interface Test3 
 { 
-  id uid; 
+  id uid;  // expected-note {{ivar is declared here}}
 } 
-@property (readwrite, assign) id uid; 
+@property (readwrite, assign) id uid;  // expected-note {{property declared here}}
 @end
 
-@implementation Test3
+// rdar://11671080
+@implementation Test3 // expected-warning {{auto autosynthesized property has same name as an existing ivar}}
 // Oops, forgot to write @synthesize! will be default synthesized
 - (void) myMethod { 
    self.uid = 0; // Use of the “setter”