Index: cfe/trunk/include/clang/Basic/OpenCLOptions.h
===================================================================
--- cfe/trunk/include/clang/Basic/OpenCLOptions.h
+++ cfe/trunk/include/clang/Basic/OpenCLOptions.h
@@ -15,6 +15,8 @@
 #ifndef LLVM_CLANG_BASIC_OPENCLOPTIONS_H
 #define LLVM_CLANG_BASIC_OPENCLOPTIONS_H
 
+#include "llvm/ADT/StringRef.h"
+
 namespace clang {
 
 /// \brief OpenCL supported extensions and optional core features
@@ -28,9 +30,39 @@
 #include "clang/Basic/OpenCLExtensions.def"
   }
 
-  // Enable all options.
-  void setAll() {
-#define OPENCLEXT(nm)   nm = 1;
+  // Enable or disable all options.
+  void setAll(bool Enable = true) {
+#define OPENCLEXT(nm)   nm = Enable;
+#include "clang/Basic/OpenCLExtensions.def"
+  }
+
+  /// \brief Enable or disable support for OpenCL extensions
+  /// \param Ext name of the extension optionally prefixed with
+  ///        '+' or '-'
+  /// \param Enable used when \p Ext is not prefixed by '+' or '-'
+  void set(llvm::StringRef Ext, bool Enable = true) {
+    assert(!Ext.empty() && "Extension is empty.");
+
+    switch (Ext[0]) {
+    case '+':
+      Enable = true;
+      Ext = Ext.drop_front();
+      break;
+    case '-':
+      Enable = false;
+      Ext = Ext.drop_front();
+      break;
+    }
+
+    if (Ext.equals("all")) {
+      setAll(Enable);
+      return;
+    }
+
+#define OPENCLEXT(nm)       \
+    if (Ext.equals(#nm)) {  \
+      nm = Enable;          \
+    }
 #include "clang/Basic/OpenCLExtensions.def"
   }
 
Index: cfe/trunk/include/clang/Basic/TargetInfo.h
===================================================================
--- cfe/trunk/include/clang/Basic/TargetInfo.h
+++ cfe/trunk/include/clang/Basic/TargetInfo.h
@@ -995,6 +995,13 @@
   /// \brief Set supported OpenCL extensions and optional core features.
   virtual void setSupportedOpenCLOpts() {}
 
+  /// \brief Set supported OpenCL extensions as written on command line
+  virtual void setOpenCLExtensionOpts() {
+    for (const auto &Ext : getTargetOpts().OpenCLExtensionsAsWritten) {
+      getTargetOpts().SupportedOpenCLOptions.set(Ext);
+    }
+  }
+
   /// \brief Get supported OpenCL extensions and optional core features.
   OpenCLOptions &getSupportedOpenCLOpts() {
     return getTargetOpts().SupportedOpenCLOptions;
Index: cfe/trunk/include/clang/Basic/TargetOptions.h
===================================================================
--- cfe/trunk/include/clang/Basic/TargetOptions.h
+++ cfe/trunk/include/clang/Basic/TargetOptions.h
@@ -58,6 +58,10 @@
 
   /// Supported OpenCL extensions and optional core features.
   OpenCLOptions SupportedOpenCLOptions;
+
+  /// \brief The list of OpenCL extensions to enable or disable, as written on
+  /// the command line.
+  std::vector<std::string> OpenCLExtensionsAsWritten;
 };
 
 }  // end namespace clang
Index: cfe/trunk/include/clang/Driver/CC1Options.td
===================================================================
--- cfe/trunk/include/clang/Driver/CC1Options.td
+++ cfe/trunk/include/clang/Driver/CC1Options.td
@@ -688,6 +688,13 @@
   HelpText<"include a detailed record of preprocessing actions">;
 
 //===----------------------------------------------------------------------===//
+// OpenCL Options
+//===----------------------------------------------------------------------===//
+
+def cl_ext_EQ : CommaJoined<["-"], "cl-ext=">,
+  HelpText<"OpenCL only. Enable or disable OpenCL extensions. The argument is a comma-separated sequence of one or more extension names, each prefixed by '+' or '-'.">;
+
+//===----------------------------------------------------------------------===//
 // CUDA Options
 //===----------------------------------------------------------------------===//
 
Index: cfe/trunk/lib/Basic/Targets.cpp
===================================================================
--- cfe/trunk/lib/Basic/Targets.cpp
+++ cfe/trunk/lib/Basic/Targets.cpp
@@ -8799,6 +8799,7 @@
     return nullptr;
 
   Target->setSupportedOpenCLOpts();
+  Target->setOpenCLExtensionOpts();
 
   if (!Target->validateTarget(Diags))
     return nullptr;
Index: cfe/trunk/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- cfe/trunk/lib/Frontend/CompilerInvocation.cpp
+++ cfe/trunk/lib/Frontend/CompilerInvocation.cpp
@@ -2385,6 +2385,7 @@
   // Use the default target triple if unspecified.
   if (Opts.Triple.empty())
     Opts.Triple = llvm::sys::getDefaultTargetTriple();
+  Opts.OpenCLExtensionsAsWritten = Args.getAllArgValues(OPT_cl_ext_EQ);
 }
 
 bool CompilerInvocation::CreateFromArgs(CompilerInvocation &Res,
Index: cfe/trunk/test/SemaOpenCL/extensions.cl
===================================================================
--- cfe/trunk/test/SemaOpenCL/extensions.cl
+++ cfe/trunk/test/SemaOpenCL/extensions.cl
@@ -2,7 +2,26 @@
 // RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -pedantic -fsyntax-only -cl-std=CL1.1
 
 // Test with a target not supporting fp64.
-// RUN: %clang_cc1 %s -triple r600-unknown-unknown -target-cpu r600 -verify -pedantic -fsyntax-only -DNOFP64
+// RUN: %clang_cc1 %s -triple r600-unknown-unknown -target-cpu r600 -verify -pedantic -fsyntax-only -DNOFP64 -DNOFP16
+
+// Test with some extensions enabled or disabled by cmd-line args
+//
+// Target does not support fp64 and fp16 - override it
+// RUN: %clang_cc1 %s -triple r600-unknown-unknown -target-cpu r600 -verify -pedantic -fsyntax-only -cl-ext=+cl_khr_fp64,+cl_khr_fp16
+//
+// Disable or enable all extensions
+// RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -pedantic -fsyntax-only -cl-ext=-all -DNOFP64 -DNOFP16
+// RUN: %clang_cc1 %s -triple r600-unknown-unknown -target-cpu r600 -verify -pedantic -fsyntax-only -cl-ext=+all
+// RUN: %clang_cc1 %s -triple r600-unknown-unknown -target-cpu r600 -verify -pedantic -fsyntax-only -cl-ext=+all,-cl_khr_fp64 -DNOFP64
+// RUN: %clang_cc1 %s -triple r600-unknown-unknown -target-cpu r600 -verify -pedantic -fsyntax-only -cl-ext=-all,+cl_khr_fp64 -DNOFP16
+//
+// Concatenating
+// RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -pedantic -fsyntax-only -cl-ext=-cl_khr_fp64 -cl-ext=+cl_khr_fp64
+// RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -pedantic -fsyntax-only -cl-ext=-cl_khr_fp64,+cl_khr_fp64
+// RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -pedantic -fsyntax-only -cl-ext=-all -cl-ext=+cl_khr_fp64 -cl-ext=+cl_khr_fp16 -cl-ext=-cl_khr_fp64 -DNOFP64
+// RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -pedantic -fsyntax-only -cl-ext=-all -cl-ext=+cl_khr_fp64,-cl_khr_fp64,+cl_khr_fp16 -DNOFP64
+
+
 
 void f1(double da) { // expected-error {{type 'double' requires cl_khr_fp64 extension}}
   double d; // expected-error {{type 'double' requires cl_khr_fp64 extension}}
@@ -14,6 +33,11 @@
 // expected-warning@-2{{unsupported OpenCL extension 'cl_khr_fp64' - ignoring}}
 #endif
 
+#pragma OPENCL EXTENSION cl_khr_fp16 : enable
+#ifdef NOFP16
+// expected-warning@-2{{unsupported OpenCL extension 'cl_khr_fp16' - ignoring}}
+#endif
+
 void f2(void) {
   double d;
 #ifdef NOFP64