7 files changed, 40 insertions, 5 deletions
diff --git a/include/clang/AST/DeclObjC.h b/include/clang/AST/DeclObjC.h
index 8282e0aab5..2112d537c3 100644
--- a/include/clang/AST/DeclObjC.h
+++ b/include/clang/AST/DeclObjC.h
@@ -1367,7 +1367,8 @@ public:
     OBJC_PR_retain    = 0x10,
     OBJC_PR_copy      = 0x20,
     OBJC_PR_nonatomic = 0x40,
-    OBJC_PR_setter    = 0x80
+    OBJC_PR_setter    = 0x80,
+    OBJC_PR_atomic    = 0x100
   };
 
   enum SetterKind { Assign, Retain, Copy };
@@ -1375,8 +1376,8 @@ public:
 private:
   SourceLocation AtLoc;   // location of @property
   TypeSourceInfo *DeclType;
-  unsigned PropertyAttributes : 8;
-  unsigned PropertyAttributesAsWritten : 8;
+  unsigned PropertyAttributes : 9;
+  unsigned PropertyAttributesAsWritten : 9;
   // @required/@optional
   unsigned PropertyImplementation : 2;
 
diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td
index 92b29b2c98..141770a942 100644
--- a/include/clang/Basic/DiagnosticGroups.td
+++ b/include/clang/Basic/DiagnosticGroups.td
@@ -148,6 +148,7 @@ def UsedButMarkedUnused : DiagGroup<"used-but-marked-unused">;
 def ReadOnlySetterAttrs : DiagGroup<"readonly-setter-attrs">;
 def Reorder : DiagGroup<"reorder">;
 def UndeclaredSelector : DiagGroup<"undeclared-selector">;
+def ImplicitAtomic : DiagGroup<"implicit-atomic-properties">;
 def Selector : DiagGroup<"selector">;
 def NonfragileAbi2 : DiagGroup<"nonfragile-abi2">;
 def Protocol : DiagGroup<"protocol">;
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 40029855dd..cfa2ab6d21 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -436,6 +436,11 @@ def warn_objc_property_attr_mutually_exclusive : Warning<
   InGroup<ReadOnlySetterAttrs>, DefaultIgnore;
 def warn_undeclared_selector : Warning<
   "undeclared selector %0">, InGroup<UndeclaredSelector>, DefaultIgnore;
+def warn_implicit_atomic_property : Warning<
+  "property is assumed atomic by default">, InGroup<ImplicitAtomic>, DefaultIgnore;
+def warn_auto_implicit_atomic_property : Warning<
+  "property is assumed atomic when auto-synthesizing the property">, 
+  InGroup<ImplicitAtomic>, DefaultIgnore;
 def warn_unimplemented_selector:  Warning<
   "unimplemented selector %0">, InGroup<Selector>, DefaultIgnore;
 def warn_unimplemented_protocol_method : Warning<
diff --git a/include/clang/Sema/DeclSpec.h b/include/clang/Sema/DeclSpec.h
index aab63c0863..484204b1b2 100644
--- a/include/clang/Sema/DeclSpec.h
+++ b/include/clang/Sema/DeclSpec.h
@@ -539,7 +539,8 @@ public:
     DQ_PR_retain = 0x10,
     DQ_PR_copy = 0x20,
     DQ_PR_nonatomic = 0x40,
-    DQ_PR_setter = 0x80
+    DQ_PR_setter = 0x80,
+    DQ_PR_atomic = 0x100
   };
 
 
@@ -573,7 +574,7 @@ private:
   ObjCDeclQualifier objcDeclQualifier : 6;
 
   // NOTE: VC++ treats enums as signed, avoid using ObjCPropertyAttributeKind
-  unsigned PropertyAttributes : 8;
+  unsigned PropertyAttributes : 9;
   IdentifierInfo *GetterName;    // getter name of NULL if no getter
   IdentifierInfo *SetterName;    // setter name of NULL if no setter
 };
diff --git a/lib/Parse/ParseObjc.cpp b/lib/Parse/ParseObjc.cpp
index 4324e0824d..f1c48a6a3a 100644
--- a/lib/Parse/ParseObjc.cpp
+++ b/lib/Parse/ParseObjc.cpp
@@ -509,6 +509,8 @@ void Parser::ParseObjCPropertyAttribute(ObjCDeclSpec &DS, Decl *ClassDecl,
       DS.setPropertyAttributes(ObjCDeclSpec::DQ_PR_copy);
     else if (II->isStr("nonatomic"))
       DS.setPropertyAttributes(ObjCDeclSpec::DQ_PR_nonatomic);
+    else if (II->isStr("atomic"))
+      DS.setPropertyAttributes(ObjCDeclSpec::DQ_PR_atomic);
     else if (II->isStr("getter") || II->isStr("setter")) {
       bool IsSetter = II->getNameStart()[0] == 's';
 
diff --git a/lib/Sema/SemaObjCProperty.cpp b/lib/Sema/SemaObjCProperty.cpp
index a1664d558e..65a447e2a1 100644
--- a/lib/Sema/SemaObjCProperty.cpp
+++ b/lib/Sema/SemaObjCProperty.cpp
@@ -299,6 +299,8 @@ ObjCPropertyDecl *Sema::CreatePropertyDecl(Scope *S,
 
   if (Attributes & ObjCDeclSpec::DQ_PR_nonatomic)
     PDecl->setPropertyAttributes(ObjCPropertyDecl::OBJC_PR_nonatomic);
+  else if (Attributes & ObjCDeclSpec::DQ_PR_atomic)
+    PDecl->setPropertyAttributes(ObjCPropertyDecl::OBJC_PR_atomic);
 
   PDecl->setPropertyAttributesAsWritten(PDecl->getPropertyAttributes());
   
@@ -349,6 +351,16 @@ Decl *Sema::ActOnPropertyImplDecl(Scope *S,
       Diag(PropertyLoc, diag::error_bad_property_decl) << IDecl->getDeclName();
       return 0;
     }
+    unsigned PIkind = property->getPropertyAttributesAsWritten();
+    if ((PIkind & (ObjCPropertyDecl::OBJC_PR_atomic |
+                   ObjCPropertyDecl::OBJC_PR_nonatomic) ) == 0) {
+      if (AtLoc.isValid())
+        Diag(AtLoc, diag::warn_implicit_atomic_property);
+      else
+        Diag(IC->getLocation(), diag::warn_auto_implicit_atomic_property);
+      Diag(property->getLocation(), diag::note_property_declare);
+    }
+    
     if (const ObjCCategoryDecl *CD =
         dyn_cast<ObjCCategoryDecl>(property->getDeclContext())) {
       if (!CD->IsClassExtension()) {
diff --git a/test/SemaObjC/warn-implicit-atomic-property.m b/test/SemaObjC/warn-implicit-atomic-property.m
new file mode 100644
index 0000000000..b0a6597989
--- /dev/null
+++ b/test/SemaObjC/warn-implicit-atomic-property.m
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -Wimplicit-atomic-properties -fobjc-nonfragile-abi2 -verify %s
+// rdar://8774580
+
+@interface Super
+@property (nonatomic, readwrite) int P; // OK
+@property (atomic, readwrite) int P1; // OK
+@property (readwrite) int P2; // expected-note {{property declared here}}
+@property int P3; // expected-note {{property declared here}}
+@end
+
+@implementation Super // expected-warning {{property is assumed atomic when auto-synthesizing the property [-Wimplicit-atomic-properties]}}
+@synthesize P,P1,P2; // expected-warning {{property is assumed atomic by default [-Wimplicit-atomic-properties]}}
+@end