Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -4170,6 +4170,10 @@
   unsigned getUnwindWordWidth() const override { return 64; }
   unsigned getRegisterWidth() const override { return 64; }
 
+  bool hasFloat128Type() const override {
+    return true;
+  }
+
   bool validateGlobalRegisterVariable(StringRef RegName,
                                       unsigned RegSize,
                                       bool &HasSizeMismatch) const override {
Index: test/Sema/128bitfloat.cpp
===================================================================
--- test/Sema/128bitfloat.cpp
+++ test/Sema/128bitfloat.cpp
@@ -1,6 +1,16 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -std=gnu++11 %s
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
 
+#ifdef __x86_64__
+__float128 f;
+template<typename> struct __is_floating_point_helper {};
+template<> struct __is_floating_point_helper<__float128> {};
+int g(int x, __float128 *y) {
+  return x + *y;
+}
+
+// expected-no-diagnostics
+#else
 #if !defined(__STRICT_ANSI__)
 __float128 f;  // expected-error {{__float128 is not supported on this target}}
 // But this should work:
@@ -22,3 +32,4 @@
 }
 
 #endif
+#endif
Index: test/Sema/attr-mode.c
===================================================================
--- test/Sema/attr-mode.c
+++ test/Sema/attr-mode.c
@@ -76,7 +76,7 @@
 void test_long_to_i64(long* y) { f_i64_arg(y); }
 void test_long_to_ui64(unsigned long* y) { f_ui64_arg(y); }
 #endif
-typedef          float f128ibm __attribute__ ((mode (TF)));     // expected-error{{unsupported machine mode 'TF'}}
+typedef          float f128ibm __attribute__ ((mode (TF)));
 #elif TEST_64BIT_PPC64
 typedef          float f128ibm __attribute__ ((mode (TF)));
 typedef _Complex float c128ibm __attribute__ ((mode (TC)));