diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 21a5480..3f63a50 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1787,8 +1787,9 @@
   "redeclaration has different alignment requirement (%1 vs %0)">;
 def err_alignas_underaligned : Error<
   "requested alignment is less than minimum alignment of %1 for type %0">;
-def err_attribute_first_argument_not_int_or_bool : Error<
-  "%0 attribute first argument must be of int or bool type">;
+def err_attribute_argument_n_type : Error<
+  "%0 attribute requires parameter %1 to be %select{int or bool|an integer "
+  "constant|a string|an identifier}2">;
 def err_attribute_argument_outof_range : Error<
   "init_priority attribute requires integer constant between "
   "101 and 65535 inclusive">;
@@ -1797,12 +1798,6 @@
   "of objects of class type">;
 def err_attribute_argument_vec_type_hint : Error<
   "invalid attribute argument %0 - expecting a vector or vectorizable scalar type">;
-def err_attribute_argument_n_not_int : Error<
-  "'%0' attribute requires parameter %1 to be an integer constant">;
-def err_attribute_argument_n_not_string : Error<
-  "'%0' attribute requires parameter %1 to be a string">;
-def err_attribute_argument_n_not_identifier : Error<
-  "'%0' attribute requires parameter %1 to be an identifier">;
 def err_attribute_argument_out_of_bounds : Error<
   "'%0' attribute parameter %1 is out of bounds">;
 def err_attribute_uuid_malformed_guid : Error<
@@ -2015,10 +2010,10 @@
   "variables, functions and tag types|thread-local variables|"
   "variables and fields|variables, data members and tag types|"
   "types and namespaces|Objective-C interfaces}1">;
-def warn_type_attribute_wrong_type : Warning<
-  "'%0' only applies to %select{function|pointer|"
-  "Objective-C object or block pointer}1 types; type here is %2">,
-  InGroup<IgnoredAttributes>;
+def warn_type_attribute_wrong_type : Warning<
+  "'%0' only applies to %select{function|pointer|"
+  "Objective-C object or block pointer}1 types; type here is %2">,
+  InGroup<IgnoredAttributes>;
 def warn_attribute_requires_functions_or_static_globals : Warning<
   "%0 only applies to variables with static storage duration and functions">,
   InGroup<IgnoredAttributes>;
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 8079787..00379b6 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -56,6 +56,15 @@
   ExpectedObjectiveCInterface
 };
 
+/// These constants match the enumerated choices of
+/// err_attribute_argument_n_type.
+enum AttributeArgumentNType {
+  ArgumentIntOrBool,
+  ArgumentIntegerConstant,
+  ArgumentString,
+  ArgumentIdentifier
+};
+
 //===----------------------------------------------------------------------===//
 //  Helper functions
 //===----------------------------------------------------------------------===//
@@ -252,8 +261,9 @@
   llvm::APSInt IdxInt;
   if (IdxExpr->isTypeDependent() || IdxExpr->isValueDependent() ||
       !IdxExpr->isIntegerConstantExpr(IdxInt, S.Context)) {
-    S.Diag(AttrLoc, diag::err_attribute_argument_n_not_int)
-      << AttrName << AttrArgNum << IdxExpr->getSourceRange();
+    std::string Name = std::string("'") + AttrName.str() + std::string("'");
+    S.Diag(AttrLoc, diag::err_attribute_argument_n_type) << Name.c_str()
+      << AttrArgNum << ArgumentIntegerConstant << IdxExpr->getSourceRange();
     return false;
   }
 
@@ -832,8 +842,8 @@
   }
 
   if (!isIntOrBool(Attr.getArg(0))) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_first_argument_not_int_or_bool)
-      << Attr.getName();
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 1 << ArgumentIntOrBool;
     return false;
   }
 
@@ -1324,8 +1334,8 @@
   // a list append function may well be __attribute((ownership_holds)).
 
   if (!AL.getParameterName()) {
-    S.Diag(AL.getLoc(), diag::err_attribute_argument_n_not_string)
-        << AL.getName()->getName() << 1;
+    S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
+      << AL.getName()->getName() << 1 << ArgumentString;
     return;
   }
   // Figure out our Kind, and check arguments while we're at it.
@@ -1530,8 +1540,8 @@
     StringLiteral *Str = dyn_cast<StringLiteral>(Arg);
 
     if (!Str || !Str->isAscii()) {
-      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
-          << "weakref" << 1;
+      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+        << Attr.getName() << 1 << ArgumentString;
       return;
     }
     // GCC will accept anything as the argument of weakref. Should we
@@ -1555,8 +1565,8 @@
   StringLiteral *Str = dyn_cast<StringLiteral>(Arg);
 
   if (!Str || !Str->isAscii()) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
-      << "alias" << 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 1 << ArgumentString;
     return;
   }
 
@@ -1985,8 +1995,9 @@
     llvm::APSInt Idx(32);
     if (E->isTypeDependent() || E->isValueDependent() ||
         !E->isIntegerConstantExpr(Idx, S.Context)) {
-      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_int)
-        << "constructor" << 1 << E->getSourceRange();
+      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+        << Attr.getName() << 1 << ArgumentIntegerConstant
+        << E->getSourceRange();
       return;
     }
     priority = Idx.getZExtValue();
@@ -2016,8 +2027,9 @@
     llvm::APSInt Idx(32);
     if (E->isTypeDependent() || E->isValueDependent() ||
         !E->isIntegerConstantExpr(Idx, S.Context)) {
-      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_int)
-        << "destructor" << 1 << E->getSourceRange();
+      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+        << Attr.getName() << 1 << ArgumentIntegerConstant
+        << E->getSourceRange();
       return;
     }
     priority = Idx.getZExtValue();
@@ -2387,8 +2399,8 @@
   StringLiteral *Str = dyn_cast<StringLiteral>(Arg);
 
   if (!Str || !Str->isAscii()) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
-      << (isTypeVisibility ? "type_visibility" : "visibility") << 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 1 << ArgumentString;
     return;
   }
 
@@ -2439,8 +2451,8 @@
 
   if (Attr.getNumArgs() != 0 || !Attr.getParameterName()) {
     if (!Attr.getParameterName() && Attr.getNumArgs() == 1) {
-      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
-        << "objc_method_family" << 1;
+      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+        << Attr.getName() << 1 << ArgumentString;
     } else {
       S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 0;
     }
@@ -2546,8 +2558,8 @@
 
 static void handleBlocksAttr(Sema &S, Decl *D, const AttributeList &Attr) {
   if (!Attr.getParameterName()) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
-      << "blocks" << 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 1 << ArgumentString;
     return;
   }
 
@@ -2577,14 +2589,20 @@
     return;
   }
 
+  // Normalize the attribute name, __foo__ becomes foo.
+  StringRef AttrName = Attr.getName()->getName();
+  if (AttrName.startswith("__") && AttrName.endswith("__"))
+    AttrName = AttrName.substr(2, AttrName.size() - 4);
+
   unsigned sentinel = 0;
   if (Attr.getNumArgs() > 0) {
     Expr *E = Attr.getArg(0);
     llvm::APSInt Idx(32);
     if (E->isTypeDependent() || E->isValueDependent() ||
         !E->isIntegerConstantExpr(Idx, S.Context)) {
-      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_int)
-       << "sentinel" << 1 << E->getSourceRange();
+      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+        << "'" + AttrName.str() + "'" << 1 << ArgumentIntegerConstant
+        << E->getSourceRange();
       return;
     }
 
@@ -2603,8 +2621,9 @@
     llvm::APSInt Idx(32);
     if (E->isTypeDependent() || E->isValueDependent() ||
         !E->isIntegerConstantExpr(Idx, S.Context)) {
-      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_int)
-        << "sentinel" << 2 << E->getSourceRange();
+      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+        << "'" + AttrName.str() + "'" << 2 << ArgumentIntegerConstant
+        << E->getSourceRange();
       return;
     }
     nullPos = Idx.getZExtValue();
@@ -3030,8 +3049,9 @@
   llvm::APSInt Idx(32);
   if (IdxExpr->isTypeDependent() || IdxExpr->isValueDependent() ||
       !IdxExpr->isIntegerConstantExpr(Idx, S.Context)) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_int)
-    << "format" << 2 << IdxExpr->getSourceRange();
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 2 << ArgumentIntegerConstant
+      << IdxExpr->getSourceRange();
     return;
   }
 
@@ -3188,8 +3208,8 @@
 static void handleFormatAttr(Sema &S, Decl *D, const AttributeList &Attr) {
 
   if (!Attr.getParameterName()) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
-      << "format" << 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 1 << ArgumentString;
     return;
   }
 
@@ -3233,8 +3253,9 @@
   llvm::APSInt Idx(32);
   if (IdxExpr->isTypeDependent() || IdxExpr->isValueDependent() ||
       !IdxExpr->isIntegerConstantExpr(Idx, S.Context)) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_int)
-      << "format" << 2 << IdxExpr->getSourceRange();
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 2 << ArgumentIntegerConstant
+      << IdxExpr->getSourceRange();
     return;
   }
 
@@ -3288,8 +3309,9 @@
   llvm::APSInt FirstArg(32);
   if (FirstArgExpr->isTypeDependent() || FirstArgExpr->isValueDependent() ||
       !FirstArgExpr->isIntegerConstantExpr(FirstArg, S.Context)) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_int)
-      << "format" << 3 << FirstArgExpr->getSourceRange();
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 3 << ArgumentIntegerConstant
+      << FirstArgExpr->getSourceRange();
     return;
   }
 
@@ -4085,8 +4107,8 @@
     Expr *Arg = attr.getArg(0);
     StringLiteral *Str = dyn_cast<StringLiteral>(Arg);
     if (!Str || !Str->isAscii()) {
-      Diag(attr.getLoc(), diag::err_attribute_argument_n_not_string)
-        << "pcs" << 1;
+      Diag(attr.getLoc(), diag::err_attribute_argument_n_type)
+        << attr.getName() << 1 << ArgumentString;
       attr.setInvalid();
       return true;
     }
@@ -4201,8 +4223,9 @@
     if (MaxThreadsExpr->isTypeDependent() ||
         MaxThreadsExpr->isValueDependent() ||
         !MaxThreadsExpr->isIntegerConstantExpr(MaxThreads, S.Context)) {
-      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_int)
-        << "launch_bounds" << 1 << MaxThreadsExpr->getSourceRange();
+      S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+        << Attr.getName() << 1 << ArgumentIntegerConstant
+        << MaxThreadsExpr->getSourceRange();
       return;
     }
 
@@ -4212,8 +4235,9 @@
       if (MinBlocksExpr->isTypeDependent() ||
           MinBlocksExpr->isValueDependent() ||
           !MinBlocksExpr->isIntegerConstantExpr(MinBlocks, S.Context)) {
-        S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_int)
-          << "launch_bounds" << 2 << MinBlocksExpr->getSourceRange();
+        S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+          << Attr.getName() << 2 << ArgumentIntegerConstant
+          << MinBlocksExpr->getSourceRange();
         return;
       }
     }
@@ -4232,8 +4256,8 @@
                                           const AttributeList &Attr) {
   StringRef AttrName = Attr.getName()->getName();
   if (!Attr.getParameterName()) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_identifier)
-      << Attr.getName() << /* arg num = */ 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << /* arg num = */ 1 << ArgumentIdentifier;
     return;
   }
 
@@ -4283,8 +4307,8 @@
                                          const AttributeList &Attr) {
   IdentifierInfo *PointerKind = Attr.getParameterName();
   if (!PointerKind) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_identifier)
-      << "type_tag_for_datatype" << 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 1 << ArgumentIdentifier;
     return;
   }
 
@@ -4641,8 +4665,8 @@
   Expr *Arg = Attr.getArg(0);
   StringLiteral *Str = dyn_cast<StringLiteral>(Arg);
   if (!Str || !Str->isAscii()) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
-      << "uuid" << 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_type)
+      << Attr.getName() << 1 << ArgumentString;
     return;
   }
 
diff --git a/lib/Sema/SemaType.cpp b/lib/Sema/SemaType.cpp
index 2e0a06b..2e7f0ac 100644
--- a/lib/Sema/SemaType.cpp
+++ b/lib/Sema/SemaType.cpp
@@ -3936,8 +3936,8 @@
     AttrLoc = S.getSourceManager().getImmediateExpansionRange(AttrLoc).first;
 
   if (!attr.getParameterName()) {
-    S.Diag(AttrLoc, diag::err_attribute_argument_n_not_string)
-      << "objc_ownership" << 1;
+    S.Diag(AttrLoc, diag::err_attribute_argument_n_type)
+      << attr.getName() << 1 << 2 /*string*/;
     attr.setInvalid();
     return true;
   }
@@ -4072,8 +4072,8 @@
 
   // Check the attribute arguments.
   if (!attr.getParameterName()) {
-    S.Diag(attr.getLoc(), diag::err_attribute_argument_n_not_string)
-      << "objc_gc" << 1;
+    S.Diag(attr.getLoc(), diag::err_attribute_argument_n_type)
+      << attr.getName() << 1 << 2 /*string*/;
     attr.setInvalid();
     return true;
   }
diff --git a/test/SemaCXX/warn-thread-safety-parsing.cpp b/test/SemaCXX/warn-thread-safety-parsing.cpp
index ee6ec92..83db05b 100644
--- a/test/SemaCXX/warn-thread-safety-parsing.cpp
+++ b/test/SemaCXX/warn-thread-safety-parsing.cpp
@@ -760,11 +760,11 @@
 
 // illegal attribute arguments
 int etf_function_bad_1() EXCLUSIVE_TRYLOCK_FUNCTION(mu1); // \
-  // expected-error {{'exclusive_trylock_function' attribute first argument must be of int or bool type}}
+  // expected-error {{'exclusive_trylock_function' attribute requires parameter 1 to be int or bool}}
 int etf_function_bad_2() EXCLUSIVE_TRYLOCK_FUNCTION("mu"); // \
-  // expected-error {{'exclusive_trylock_function' attribute first argument must be of int or bool type}}
+  // expected-error {{'exclusive_trylock_function' attribute requires parameter 1 to be int or bool}}
 int etf_function_bad_3() EXCLUSIVE_TRYLOCK_FUNCTION(muDoublePointer); // \
-  // expected-error {{'exclusive_trylock_function' attribute first argument must be of int or bool type}}
+  // expected-error {{'exclusive_trylock_function' attribute requires parameter 1 to be int or bool}}
 
 int etf_function_bad_4() EXCLUSIVE_TRYLOCK_FUNCTION(1, "mu"); // \
   // expected-warning {{ignoring 'exclusive_trylock_function' attribute because its argument is invalid}}
@@ -834,11 +834,11 @@
 
 // illegal attribute arguments
 int stf_function_bad_1() SHARED_TRYLOCK_FUNCTION(mu1); // \
-  // expected-error {{'shared_trylock_function' attribute first argument must be of int or bool type}}
+  // expected-error {{'shared_trylock_function' attribute requires parameter 1 to be int or bool}}
 int stf_function_bad_2() SHARED_TRYLOCK_FUNCTION("mu"); // \
-  // expected-error {{'shared_trylock_function' attribute first argument must be of int or bool type}}
+  // expected-error {{'shared_trylock_function' attribute requires parameter 1 to be int or bool}}
 int stf_function_bad_3() SHARED_TRYLOCK_FUNCTION(muDoublePointer); // \
-  // expected-error {{'shared_trylock_function' attribute first argument must be of int or bool type}}
+  // expected-error {{'shared_trylock_function' attribute requires parameter 1 to be int or bool}}
 
 int stf_function_bad_4() SHARED_TRYLOCK_FUNCTION(1, "mu"); // \
   // expected-warning {{ignoring 'shared_trylock_function' attribute because its argument is invalid}}