Index: cfe/trunk/include/clang/Basic/LangOptions.def
===================================================================
--- cfe/trunk/include/clang/Basic/LangOptions.def
+++ cfe/trunk/include/clang/Basic/LangOptions.def
@@ -218,7 +218,7 @@
 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(IncludeDefaultHeader, 1, 0, "Include default header file for OpenCL")
 BENIGN_LANGOPT(DelayedTemplateParsing , 1, 0, "delayed template parsing")
 LANGOPT(BlocksRuntimeOptional , 1, 0, "optional blocks runtime")
 
Index: cfe/trunk/include/clang/Driver/CC1Options.td
===================================================================
--- cfe/trunk/include/clang/Driver/CC1Options.td
+++ cfe/trunk/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 finclude_default_header : Flag<["-"], "finclude-default-header">,
+  HelpText<"Include the default header file for OpenCL">;
 
 // C++ TSes.
 def fcoroutines : Flag<["-"], "fcoroutines">,
Index: cfe/trunk/include/clang/Frontend/CompilerInvocation.h
===================================================================
--- cfe/trunk/include/clang/Frontend/CompilerInvocation.h
+++ cfe/trunk/include/clang/Frontend/CompilerInvocation.h
@@ -155,9 +155,10 @@
   /// \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: cfe/trunk/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- cfe/trunk/lib/Frontend/CompilerInvocation.cpp
+++ cfe/trunk/lib/Frontend/CompilerInvocation.cpp
@@ -1459,6 +1459,7 @@
 
 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
@@ -1543,6 +1544,10 @@
     Opts.DefaultFPContract = 1;
     Opts.NativeHalfType = 1;
     Opts.NativeHalfArgsAndReturns = 1;
+    // Include default header file for OpenCL.
+    if (Opts.IncludeDefaultHeader) {
+      PPOpts.Includes.push_back("opencl-c.h");
+    }
   }
 
   Opts.CUDA = IK == IK_CUDA || IK == IK_PreprocessedCuda ||
@@ -1589,6 +1594,7 @@
 
 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;
@@ -1660,8 +1666,10 @@
       LangStd = OpenCLLangStd;
   }
 
+  Opts.IncludeDefaultHeader = Args.hasArg(OPT_finclude_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,
@@ -2331,7 +2339,8 @@
                         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: cfe/trunk/lib/Headers/module.modulemap
===================================================================
--- cfe/trunk/lib/Headers/module.modulemap
+++ cfe/trunk/lib/Headers/module.modulemap
@@ -157,3 +157,8 @@
 module _Builtin_stddef_max_align_t [system] [extern_c] {
   header "__stddef_max_align_t.h"
 }
+
+module opencl_c {
+  requires opencl
+  header "opencl-c.h"
+}
Index: cfe/trunk/test/Headers/opencl-c-header.cl
===================================================================
--- cfe/trunk/test/Headers/opencl-c-header.cl
+++ cfe/trunk/test/Headers/opencl-c-header.cl
@@ -1,33 +1,90 @@
 // RUN: %clang_cc1 -triple spir-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple spir-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.1| FileCheck %s
 // RUN: %clang_cc1 -triple spir-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.2| FileCheck %s
-// RUN: %clang_cc1 -triple spir-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck %s
+// RUN: %clang_cc1 -triple spir-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck --check-prefix=CHECK20 %s
 // RUN: %clang_cc1 -triple spir64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple spir64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.1| FileCheck %s
 // RUN: %clang_cc1 -triple spir64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.2| FileCheck %s
-// RUN: %clang_cc1 -triple spir64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck %s
+// RUN: %clang_cc1 -triple spir64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck --check-prefix=CHECK20 %s
 // RUN: %clang_cc1 -triple amdgcn-unknown-amdhsa -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple amdgcn-unknown-amdhsa -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.1| FileCheck %s
 // RUN: %clang_cc1 -triple amdgcn-unknown-amdhsa -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.2| FileCheck %s
-// RUN: %clang_cc1 -triple amdgcn-unknown-amdhsa -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck %s
+// RUN: %clang_cc1 -triple amdgcn-unknown-amdhsa -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck --check-prefix=CHECK20 %s
 // RUN: %clang_cc1 -triple ppc64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple ppc64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.1| FileCheck %s
 // RUN: %clang_cc1 -triple ppc64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.2| FileCheck %s
-// RUN: %clang_cc1 -triple ppc64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck %s
+// RUN: %clang_cc1 -triple ppc64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck --check-prefix=CHECK20 %s
 // RUN: %clang_cc1 -triple powerpc-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple powerpc-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.1| FileCheck %s
 // RUN: %clang_cc1 -triple powerpc-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.2| FileCheck %s
-// RUN: %clang_cc1 -triple powerpc-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck %s
+// RUN: %clang_cc1 -triple powerpc-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck --check-prefix=CHECK20 %s
 // RUN: %clang_cc1 -triple nvptx-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple nvptx-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.1| FileCheck %s
 // RUN: %clang_cc1 -triple nvptx-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.2| FileCheck %s
-// RUN: %clang_cc1 -triple nvptx-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck %s
+// RUN: %clang_cc1 -triple nvptx-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck --check-prefix=CHECK20 %s
 // RUN: %clang_cc1 -triple nvptx64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple nvptx64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.1| FileCheck %s
 // RUN: %clang_cc1 -triple nvptx64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -emit-llvm -o - %s -cl-std=CL1.2| FileCheck %s
-// RUN: %clang_cc1 -triple nvptx64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck %s
+// RUN: %clang_cc1 -triple nvptx64-unknown-unknown -internal-isystem ../../lib/Headers -include opencl-c.h -fblocks -emit-llvm -o - %s -cl-std=CL2.0| FileCheck --check-prefix=CHECK20 %s
 
+// RUN: %clang_cc1 -finclude-default-header -emit-llvm -o - %s | FileCheck %s
 // CHECK: _Z16convert_char_rtec
+// CHECK-NOT: _Z3ctzc
+// CHECK20: _Z3ctzc
+// CHECK20-NOT: _Z16convert_char_rtec
+// CHECK-MOD: Reading modules
+
+// Test including the default header as a module.
+// The module should be compiled only once and loaded from cache afterwards.
+// Change the directory mode to read only to make sure no new modules are created.
+// Check time report to make sure module is used.
+
+// ===
+// Clear current directory.
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+
+// ===
+// Compile for OpenCL 1.0 for the first time. A module should be generated.
+// RUN: %clang_cc1 -triple spir-unknown-unknown -emit-llvm -o - -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fdisable-module-hash -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK --check-prefix=CHECK-MOD %s
+// RUN: chmod u-w %t/opencl_c.pcm
+
+// ===
+// Compile for OpenCL 1.0 for the second time. The module should not be re-created.
+// RUN: %clang_cc1 -triple spir-unknown-unknown -emit-llvm -o - -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fdisable-module-hash -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK --check-prefix=CHECK-MOD %s
+// RUN: chmod u+w %t/opencl_c.pcm
+// RUN: mv %t/opencl_c.pcm %t/1_0.pcm
+
+// ===
+// Compile for OpenCL 2.0 for the first time. The module should change.
+// RUN: %clang_cc1 -triple spir-unknown-unknown -emit-llvm -o - -cl-std=CL2.0 -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fdisable-module-hash -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK20 --check-prefix=CHECK-MOD %s
+// RUN: not diff %t/1_0.pcm %t/opencl_c.pcm
+// RUN: chmod u-w %t/opencl_c.pcm
+
+// ===
+// Compile for OpenCL 2.0 for the second time. The module should not change.
+// RUN: %clang_cc1 -triple spir-unknown-unknown -emit-llvm -o - -cl-std=CL2.0 -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fdisable-module-hash -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK20 --check-prefix=CHECK-MOD %s
+
+// Check cached module works for different OpenCL versions.
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: %clang_cc1 -triple spir-unknown-unknown -emit-llvm -o - -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK --check-prefix=CHECK-MOD %s
+// RUN: %clang_cc1 -triple spir-unknown-unknown -emit-llvm -o - -cl-std=CL2.0 -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK20 --check-prefix=CHECK-MOD %s
+// RUN: %clang_cc1 -triple amdgcn--amdhsa -emit-llvm -o - -cl-std=CL2.0  -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK20 --check-prefix=CHECK-MOD %s
+// RUN: chmod u-w %t/* 
+// RUN: %clang_cc1 -triple spir-unknown-unknown -emit-llvm -o - -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK --check-prefix=CHECK-MOD %s
+// RUN: %clang_cc1 -triple spir-unknown-unknown -emit-llvm -o - -cl-std=CL2.0 -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK20 --check-prefix=CHECK-MOD %s
+// RUN: %clang_cc1 -triple amdgcn--amdhsa -emit-llvm -o - -cl-std=CL2.0 -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -ftime-report %s 2>&1 | FileCheck --check-prefix=CHECK20 --check-prefix=CHECK-MOD %s
+// RUN: chmod u+w %t/*
+
 char f(char x) {
+#if __OPENCL_C_VERSION__ != CL_VERSION_2_0
   return convert_char_rte(x);
+#ifdef NO_HEADER
+  //expected-warning@-2{{implicit declaration of function 'convert_char_rte' is invalid in C99}}
+#endif //NO_HEADER
+
+#else //__OPENCL_C_VERSION__
+  return ctz(x);
+#endif //__OPENCL_C_VERSION__
 }