Index: include/clang/Basic/Sanitizers.def
===================================================================
--- include/clang/Basic/Sanitizers.def
+++ include/clang/Basic/Sanitizers.def
@@ -47,6 +47,9 @@
 // MemorySanitizer
 SANITIZER("memory", Memory)
 
+// libFuzzer
+SANITIZER("fuzzer", Fuzzer)
+
 // ThreadSanitizer
 SANITIZER("thread", Thread)
 
Index: include/clang/Driver/SanitizerArgs.h
===================================================================
--- include/clang/Driver/SanitizerArgs.h
+++ include/clang/Driver/SanitizerArgs.h
@@ -50,6 +50,7 @@
   bool needsSharedAsanRt() const { return AsanSharedRuntime; }
   bool needsTsanRt() const { return Sanitizers.has(SanitizerKind::Thread); }
   bool needsMsanRt() const { return Sanitizers.has(SanitizerKind::Memory); }
+  bool needsFuzzer() const { return Sanitizers.has(SanitizerKind::Fuzzer); }
   bool needsLsanRt() const {
     return Sanitizers.has(SanitizerKind::Leak) &&
            !Sanitizers.has(SanitizerKind::Address);
Index: lib/Driver/SanitizerArgs.cpp
===================================================================
--- lib/Driver/SanitizerArgs.cpp
+++ lib/Driver/SanitizerArgs.cpp
@@ -265,6 +265,10 @@
       Add &= ~InvalidTrappingKinds;
       Add &= Supported;
 
+      // Enable coverage if the fuzzing flag is set.
+      if (Add & Fuzzer)
+        CoverageFeatures |= CoverageTracePCGuard | CoverageIndirCall | CoverageTraceCmp;
+
       Kinds |= Add;
     } else if (Arg->getOption().matches(options::OPT_fno_sanitize_EQ)) {
       Arg->claim();
Index: lib/Driver/ToolChains/Darwin.h
===================================================================
--- lib/Driver/ToolChains/Darwin.h
+++ lib/Driver/ToolChains/Darwin.h
@@ -154,6 +154,8 @@
   /// Add the linker arguments to link the compiler runtime library.
   virtual void AddLinkRuntimeLibArgs(const llvm::opt::ArgList &Args,
                                      llvm::opt::ArgStringList &CmdArgs) const;
+  void AddLinkToFuzzer(const llvm::opt::ArgList &Args,
+                       llvm::opt::ArgStringList &CmdArgs) const;
 
   virtual void addStartObjectFileArgs(const llvm::opt::ArgList &Args,
                                       llvm::opt::ArgStringList &CmdArgs) const {
Index: lib/Driver/ToolChains/Darwin.cpp
===================================================================
--- lib/Driver/ToolChains/Darwin.cpp
+++ lib/Driver/ToolChains/Darwin.cpp
@@ -930,6 +930,18 @@
   }
 }
 
+void MachO::AddFuzzerLinkArgs(const ArgList &Args, ArgStringList &CmdArgs) const {
+
+  // Go up one directory from Clang to find the libfuzzer archive file.
+  StringRef ParentDir = llvm::sys::path::parent_path(getDriver().InstalledDir);
+  SmallString<128> P(ParentDir);
+  llvm::sys::path::append(P, "lib", "libLLVMFuzzer.a");
+  CmdArgs.push_back(Args.MakeArgString(P));
+
+  // Libfuzzer is written in C++ and requires libcxx.
+  AddCXXStdlibLibArgs(Args, CmdArgs);
+}
+
 StringRef Darwin::getPlatformFamily() const {
   switch (TargetPlatform) {
     case DarwinPlatformKind::MacOS:
@@ -1039,6 +1051,8 @@
     AddLinkSanitizerLibArgs(Args, CmdArgs, "ubsan");
   if (Sanitize.needsTsanRt())
     AddLinkSanitizerLibArgs(Args, CmdArgs, "tsan");
+  if (Sanitize.needsFuzzer())
+    AddFuzzerLinkArgs(Args, CmdArgs);
   if (Sanitize.needsStatsRt()) {
     StringRef OS = isTargetMacOS() ? "osx" : "iossim";
     AddLinkRuntimeLib(Args, CmdArgs,
@@ -1891,6 +1905,7 @@
   const bool IsX86_64 = getTriple().getArch() == llvm::Triple::x86_64;
   SanitizerMask Res = ToolChain::getSupportedSanitizers();
   Res |= SanitizerKind::Address;
+  Res |= SanitizerKind::Fuzzer;
   if (isTargetMacOS()) {
     if (!isMacosxVersionLT(10, 9))
       Res |= SanitizerKind::Vptr;
Index: lib/Driver/ToolChains/Linux.cpp
===================================================================
--- lib/Driver/ToolChains/Linux.cpp
+++ lib/Driver/ToolChains/Linux.cpp
@@ -869,6 +869,7 @@
                          llvm::Triple::thumbeb;
   SanitizerMask Res = ToolChain::getSupportedSanitizers();
   Res |= SanitizerKind::Address;
+  Res |= SanitizerKind::Fuzzer;
   Res |= SanitizerKind::KernelAddress;
   Res |= SanitizerKind::Vptr;
   Res |= SanitizerKind::SafeStack;
Index: test/Driver/fuzzer.c
===================================================================
--- /dev/null
+++ test/Driver/fuzzer.c
@@ -0,0 +1,15 @@
+// Test flags inserted by -fsanitize=fuzzer.
+
+// RUN: %clang -fsanitize=fuzzer %s -### 2>&1 | FileCheck --check-prefixes=CHECK-FUZZER-LIB,CHECK-LIBCXX,CHECK-COVERAGE-FLAGS %s
+//
+// CHECK-FUZZER-LIB: libLLVMFuzzer.a
+// CHECK-LIBCXX: -lc++
+// CHECK-COVERAGE: -fsanitize-coverage-trace-pc-guard
+// CHECK-COVERAGE-SAME: -fsanitize-coverage-indirect-calls
+// CHECK-COVERAGE-SAME: -fsanitize-coverage-trace-cmp
+
+// RUN: %clang -fsanitize=fuzzer %s
+
+int LLVMFuzzerTestOneInput(const char *Data, long Size) {
+  return 0;
+}