Index: include/clang/Basic/LangOptions.def
===================================================================
--- include/clang/Basic/LangOptions.def
+++ include/clang/Basic/LangOptions.def
@@ -216,7 +216,7 @@
 LANGOPT(ObjCSubscriptingLegacyRuntime         , 1, 0, "Subscripting support in legacy ObjectiveC runtime")
 LANGOPT(FakeAddressSpaceMap , 1, 0, "OpenCL fake address space map")
 ENUM_LANGOPT(AddressSpaceMapMangling , AddrSpaceMapMangling, 2, ASMM_Target, "OpenCL address space map mangling mode")
-
+LANGOPT(NoDefaultHeader, 1, 0, "Do not include default header file for OpenCL")
 BENIGN_LANGOPT(DelayedTemplateParsing , 1, 0, "delayed template parsing")
 LANGOPT(BlocksRuntimeOptional , 1, 0, "optional blocks runtime")
 
Index: include/clang/Driver/CC1Options.td
===================================================================
--- include/clang/Driver/CC1Options.td
+++ include/clang/Driver/CC1Options.td
@@ -612,6 +612,8 @@
   HelpText<"Allow function arguments and returns of type half">;
 def fdefault_calling_conv_EQ : Joined<["-"], "fdefault-calling-conv=">,
   HelpText<"Set default MS calling convention">;
+def fno_default_header : Flag<["-"], "fno-default-header">,
+  HelpText<"Do not include the default header file for OpenCL">;
 
 // C++ TSes.
 def fcoroutines : Flag<["-"], "fcoroutines">,
Index: include/clang/Frontend/CompilerInvocation.h
===================================================================
--- include/clang/Frontend/CompilerInvocation.h
+++ include/clang/Frontend/CompilerInvocation.h
@@ -154,9 +154,10 @@
   /// \param Opts - The LangOptions object to set up.
   /// \param IK - The input language.
   /// \param T - The target triple.
+  /// \param PPOpts - The PreprocessorOptions affected.
   /// \param LangStd - The input language standard.
   static void setLangDefaults(LangOptions &Opts, InputKind IK,
-                   const llvm::Triple &T,
+                   const llvm::Triple &T, PreprocessorOptions &PPOpts,
                    LangStandard::Kind LangStd = LangStandard::lang_unspecified);
   
   /// \brief Retrieve a module hash string that is suitable for uniquely 
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -1400,6 +1400,7 @@
 
 void CompilerInvocation::setLangDefaults(LangOptions &Opts, InputKind IK,
                                          const llvm::Triple &T,
+                                         PreprocessorOptions &PPOpts,
                                          LangStandard::Kind LangStd) {
   // Set some properties which depend solely on the input kind; it would be nice
   // to move these to the language standard, and have the driver resolve the
@@ -1481,6 +1482,9 @@
     Opts.DefaultFPContract = 1;
     Opts.NativeHalfType = 1;
     Opts.NativeHalfArgsAndReturns = 1;
+    // Include default header file for OpenCL.
+    if (!Opts.NoDefaultHeader)
+      PPOpts.Includes.push_back("opencl-c.h");
   }
 
   Opts.CUDA = IK == IK_CUDA || IK == IK_PreprocessedCuda ||
@@ -1521,6 +1525,7 @@
 
 static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
                           const TargetOptions &TargetOpts,
+                          PreprocessorOptions &PPOpts,
                           DiagnosticsEngine &Diags) {
   // FIXME: Cleanup per-file based stuff.
   LangStandard::Kind LangStd = LangStandard::lang_unspecified;
@@ -1589,8 +1594,10 @@
       LangStd = OpenCLLangStd;
   }
 
+  Opts.NoDefaultHeader = Args.hasArg(OPT_fno_default_header);
+
   llvm::Triple T(TargetOpts.Triple);
-  CompilerInvocation::setLangDefaults(Opts, IK, T, LangStd);
+  CompilerInvocation::setLangDefaults(Opts, IK, T, PPOpts, LangStd);
 
   // We abuse '-f[no-]gnu-keywords' to force overriding all GNU-extension
   // keywords. This behavior is provided by GCC's poorly named '-fasm' flag,
@@ -1763,7 +1770,8 @@
 
   Opts.RTTI = Opts.CPlusPlus && !Args.hasArg(OPT_fno_rtti);
   Opts.RTTIData = Opts.RTTI && !Args.hasArg(OPT_fno_rtti_data);
-  Opts.Blocks = Args.hasArg(OPT_fblocks);
+  Opts.Blocks = Args.hasArg(OPT_fblocks) || (Opts.OpenCL
+    && Opts.OpenCLVersion >= 200 && !Args.hasArg(OPT_fno_blocks));
   Opts.BlocksRuntimeOptional = Args.hasArg(OPT_fblocks_runtime_optional);
   Opts.Coroutines = Args.hasArg(OPT_fcoroutines);
   Opts.Modules = Args.hasArg(OPT_fmodules);
@@ -2249,7 +2257,8 @@
                         Diags, LangOpts.Sanitize);
   } else {
     // Other LangOpts are only initialzed when the input is not AST or LLVM IR.
-    ParseLangArgs(LangOpts, Args, DashX, Res.getTargetOpts(), Diags);
+    ParseLangArgs(LangOpts, Args, DashX, Res.getTargetOpts(),
+      Res.getPreprocessorOpts(), Diags);
     if (Res.getFrontendOpts().ProgramAction == frontend::RewriteObjC)
       LangOpts.ObjCExceptions = 1;
   }
Index: lib/Headers/module.modulemap
===================================================================
--- lib/Headers/module.modulemap
+++ lib/Headers/module.modulemap
@@ -155,6 +155,11 @@
       header "vecintrin.h"
     }
   }
+  
+  explicit module opencl_c {
+    requires opencl
+    header "opencl-c.h"
+  }
 }
 
 module _Builtin_stddef_max_align_t [system] [extern_c] {
Index: test/CodeGenOpenCL/bool_cast.cl
===================================================================
--- test/CodeGenOpenCL/bool_cast.cl
+++ test/CodeGenOpenCL/bool_cast.cl
@@ -1,9 +1,5 @@
 // RUN: %clang_cc1 %s -emit-llvm -o - -O0 | FileCheck %s
 
-typedef unsigned char uchar4 __attribute((ext_vector_type(4)));
-typedef unsigned int int4 __attribute((ext_vector_type(4)));
-typedef float float4 __attribute((ext_vector_type(4)));
-
 // CHECK-LABEL: define void @ker()
 void kernel ker() {
   bool t = true;
Index: test/Headers/opencl-c-header.cl
===================================================================
--- test/Headers/opencl-c-header.cl
+++ test/Headers/opencl-c-header.cl
@@ -1,9 +1,14 @@
-// RUN: %clang_cc1 -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s | FileCheck %s
-// RUN: %clang_cc1 -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.1| FileCheck %s
-// RUN: %clang_cc1 -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.2| FileCheck %s
-// RUN: %clang_cc1 -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck %s
+// RUN: %clang_cc1 -fno-default-header -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -fno-default-header -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.1| FileCheck %s
+// RUN: %clang_cc1 -fno-default-header -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.2| FileCheck %s
+// RUN: %clang_cc1 -fno-default-header -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck %s
 
+// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm -verify -fno-default-header -DNO_HEADER %s
 // CHECK: _Z16convert_char_rtec
 char f(char x) {
   return convert_char_rte(x);
+#ifdef NO_HEADER
+  //expected-warning@-2{{implicit declaration of function 'convert_char_rte' is invalid in C99}}
+#endif
 }
Index: test/Parser/opencl-atomics-cl20.cl
===================================================================
--- test/Parser/opencl-atomics-cl20.cl
+++ test/Parser/opencl-atomics-cl20.cl
@@ -1,4 +1,6 @@
-// RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -pedantic -fsyntax-only
+// ToDo: a bug causing cached AST of header containing typedef of atomic_int for CL1.0. After the bug is fixed
+// -fno-default-header should be removed.
+// RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -pedantic -fsyntax-only -fno-default-header
 // RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -fsyntax-only -cl-std=CL2.0 -DCL20
 // RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -fsyntax-only -cl-std=CL2.0 -DCL20 -DEXT