Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -7398,6 +7398,9 @@
 def err_builtin_annotation_second_arg : Error<
   "second argument to __builtin_annotation must be a non-wide string constant">;
 
+def err_builtin_signbit_wrong_argument : Error<
+  "Argument type mismatch, must be float, double or long double">;
+
 // CFString checking
 def err_cfstring_literal_not_string_constant : Error<
   "CFString literal is not a string constant">;
Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -99,6 +99,22 @@
   return false;
 }
 
+static bool SemaBuiltinSignbit(Sema &S, CallExpr *TheCall) {
+  if (checkArgCount(S, TheCall, 1))
+    return true;
+
+  // Argument should be an float, double or long double.
+  Expr *ValArg = TheCall->getArg(0);
+  QualType Ty = ValArg->getType();
+  if (!Ty->isRealFloatingType()) {
+    S.Diag(ValArg->getLocStart(), diag::err_builtin_signbit_wrong_argument)
+      << ValArg->getSourceRange();
+    return true;
+  }
+
+  return false;
+}
+
 /// Check that the argument to __builtin_addressof is a glvalue, and set the
 /// result type to the corresponding pointer type.
 static bool SemaBuiltinAddressof(Sema &S, CallExpr *TheCall) {
@@ -763,6 +779,10 @@
     }
     break;
   }
+  case Builtin::BI__builtin_signbit:
+    if (SemaBuiltinSignbit(*this, TheCall))
+      return ExprError();
+    break;
   case Builtin::BI__builtin_isgreater:
   case Builtin::BI__builtin_isgreaterequal:
   case Builtin::BI__builtin_isless:
Index: test/Sema/builtins.c
===================================================================
--- test/Sema/builtins.c
+++ test/Sema/builtins.c
@@ -248,3 +248,11 @@
 
     return buf;
 }
+
+int test21(double a) {
+  return __builtin_signbit();  // expected-error {{too few arguments}}
+}
+
+int test22(void) {
+  return __builtin_signbit("1");  // expected-error {{Argument type mismatch}}
+}