Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -839,6 +839,9 @@
   case Builtin::BI__builtin_isinf_sign:
   case Builtin::BI__builtin_isnan:
   case Builtin::BI__builtin_isnormal:
+  case Builtin::BI__builtin_signbit:
+  case Builtin::BI__builtin_signbitf:
+  case Builtin::BI__builtin_signbitl:
     if (SemaBuiltinFPClassification(TheCall, 1))
       return ExprError();
     break;
Index: test/Sema/builtin-unary-fp.c
===================================================================
--- test/Sema/builtin-unary-fp.c
+++ test/Sema/builtin-unary-fp.c
@@ -9,6 +9,9 @@
   check(__builtin_isfinite(1)); // expected-error{{requires argument of floating point type}}
   check(__builtin_isinf()); // expected-error{{too few arguments}}
   check(__builtin_isnan(1,2)); // expected-error{{too many arguments}}
+  check(__builtin_signbit()); // expected-error{{too few arguments}}
+  check(__builtin_signbit(1,2)); // expected-error{{too many arguments}}
+  check(__builtin_signbit(1)); // expected-error{{requires argument of floating point type}}
   check(__builtin_fpclassify(0, 0, 0, 0, 0, 1.0));
   check(__builtin_fpclassify(0, 0, 0, 0, 0, 1)); // expected-error{{requires argument of floating point type}}
   check(__builtin_fpclassify(0, 1, 2, 3, 4.5, 5.0)); // expected-warning{{implicit conversion from 'double' to 'int' changes value from 4.5 to 4}}