Index: clang/lib/Sema/OpenCLBuiltins.td
===================================================================
--- clang/lib/Sema/OpenCLBuiltins.td
+++ clang/lib/Sema/OpenCLBuiltins.td
@@ -78,6 +78,8 @@
 def NoTypeExt   : TypeExtension<"">;
 def Fp16TypeExt : TypeExtension<"cl_khr_fp16">;
 def Fp64TypeExt : TypeExtension<"cl_khr_fp64">;
+def Atomic64TypeExt : TypeExtension<"cl_khr_int64_base_atomics cl_khr_int64_extended_atomics">;
+def AtomicFp64TypeExt : TypeExtension<"cl_khr_int64_base_atomics cl_khr_int64_extended_atomics cl_khr_fp64">;
 
 // FunctionExtension definitions.
 def FuncExtNone                          : FunctionExtension<"">;
@@ -389,10 +391,14 @@
 // OpenCL v2.0 s6.13.11: Atomic integer and floating-point types.
 def AtomicInt             : Type<"atomic_int", QualType<"Context.getAtomicType(Context.IntTy)">>;
 def AtomicUInt            : Type<"atomic_uint", QualType<"Context.getAtomicType(Context.UnsignedIntTy)">>;
-def AtomicLong            : Type<"atomic_long", QualType<"Context.getAtomicType(Context.LongTy)">>;
-def AtomicULong           : Type<"atomic_ulong", QualType<"Context.getAtomicType(Context.UnsignedLongTy)">>;
+let Extension = Atomic64TypeExt in {
+  def AtomicLong            : Type<"atomic_long", QualType<"Context.getAtomicType(Context.LongTy)">>;
+  def AtomicULong           : Type<"atomic_ulong", QualType<"Context.getAtomicType(Context.UnsignedLongTy)">>;
+}
 def AtomicFloat           : Type<"atomic_float", QualType<"Context.getAtomicType(Context.FloatTy)">>;
-def AtomicDouble          : Type<"atomic_double", QualType<"Context.getAtomicType(Context.DoubleTy)">>;
+let Extension = AtomicFp64TypeExt in {
+  def AtomicDouble          : Type<"atomic_double", QualType<"Context.getAtomicType(Context.DoubleTy)">>;
+}
 def AtomicHalf            : Type<"atomic_half", QualType<"Context.getAtomicType(Context.HalfTy)">>;
 def AtomicIntPtr          : Type<"atomic_intptr_t", QualType<"Context.getAtomicType(Context.getIntPtrType())">>;
 def AtomicUIntPtr         : Type<"atomic_uintptr_t", QualType<"Context.getAtomicType(Context.getUIntPtrType())">>;
Index: clang/test/SemaOpenCL/fdeclare-opencl-builtins.cl
===================================================================
--- clang/test/SemaOpenCL/fdeclare-opencl-builtins.cl
+++ clang/test/SemaOpenCL/fdeclare-opencl-builtins.cl
@@ -163,6 +163,25 @@
 }
 #endif // !defined(NO_HEADER) && __OPENCL_C_VERSION__ >= 200
 
+#if !defined(NO_HEADER) && __OPENCL_C_VERSION__ == 200 && defined(__opencl_c_generic_address_space)
+
+// Test that overloads that use atomic_double are not available when the fp64
+// extension is disabled.  Test this by counting the number of notes about
+// candidate functions.
+void test_atomic_double_reporting(volatile __generic atomic_int *a) {
+  atomic_init(a);
+  // expected-error@-1{{no matching function for call to 'atomic_init'}}
+#if defined(NO_FP64)
+  // Expecting 5 candidates: int, uint, long, ulong, float
+  // expected-note@-4 5 {{candidate function not viable: requires 2 arguments, but 1 was provided}}
+#else
+  // Expecting 6 candidates: int, uint, long, ulong, float, double
+  // expected-note@-7 6 {{candidate function not viable: requires 2 arguments, but 1 was provided}}
+#endif
+}
+
+#endif
+
 #if defined(NO_ATOMSCOPE) && __OPENCL_C_VERSION__ >= 300
 // Disable the feature by undefining the feature macro.
 #undef __opencl_c_atomic_scope_device
Index: clang/utils/TableGen/ClangOpenCLBuiltinEmitter.cpp
===================================================================
--- clang/utils/TableGen/ClangOpenCLBuiltinEmitter.cpp
+++ clang/utils/TableGen/ClangOpenCLBuiltinEmitter.cpp
@@ -733,6 +733,20 @@
   OS << "} // isOpenCLBuiltin\n";
 }
 
+// Emit an if-statement with an isMacroDefined call for each extension in
+// the space-separated list of extensions.
+static void EmitMacroChecks(raw_ostream &OS, StringRef Extensions) {
+  SmallVector<StringRef, 2> ExtVec;
+  Extensions.split(ExtVec, " ");
+  OS << "      if (";
+  for (StringRef Ext : ExtVec) {
+    if (Ext != ExtVec.front())
+      OS << " && ";
+    OS << "S.getPreprocessor().isMacroDefined(\"" << Ext << "\")";
+  }
+  OS << ") {\n  ";
+}
+
 void BuiltinNameEmitter::EmitQualTypeFinder() {
   OS << R"(
 
@@ -825,15 +839,14 @@
     // Collect all QualTypes for a single vector size into TypeList.
     OS << "      SmallVector<QualType, " << BaseTypes.size() << "> TypeList;\n";
     for (const auto *T : BaseTypes) {
-      StringRef Ext =
+      StringRef Exts =
           T->getValueAsDef("Extension")->getValueAsString("ExtName");
-      if (!Ext.empty()) {
-        OS << "      if (S.getPreprocessor().isMacroDefined(\"" << Ext
-           << "\")) {\n  ";
+      if (!Exts.empty()) {
+        EmitMacroChecks(OS, Exts);
       }
       OS << "      TypeList.push_back("
          << T->getValueAsDef("QTExpr")->getValueAsString("TypeExpr") << ");\n";
-      if (!Ext.empty()) {
+      if (!Exts.empty()) {
         OS << "      }\n";
       }
     }
@@ -877,15 +890,14 @@
     // Emit the cases for non generic, non image types.
     OS << "    case OCLT_" << T->getValueAsString("Name") << ":\n";
 
-    StringRef Ext = T->getValueAsDef("Extension")->getValueAsString("ExtName");
-    // If this type depends on an extension, ensure the extension macro is
+    StringRef Exts = T->getValueAsDef("Extension")->getValueAsString("ExtName");
+    // If this type depends on an extension, ensure the extension macros are
     // defined.
-    if (!Ext.empty()) {
-      OS << "      if (S.getPreprocessor().isMacroDefined(\"" << Ext
-         << "\")) {\n  ";
+    if (!Exts.empty()) {
+      EmitMacroChecks(OS, Exts);
     }
     OS << "      QT.push_back(" << QT->getValueAsString("TypeExpr") << ");\n";
-    if (!Ext.empty()) {
+    if (!Exts.empty()) {
       OS << "      }\n";
     }
     OS << "      break;\n";