Index: include/clang/Driver/ToolChain.h
===================================================================
--- include/clang/Driver/ToolChain.h
+++ include/clang/Driver/ToolChain.h
@@ -93,7 +93,7 @@
 
 private:
   const Driver &D;
-  const llvm::Triple Triple;
+  llvm::Triple Triple;
   const llvm::opt::ArgList &Args;
   // We need to initialize CachedRTTIArg before CachedRTTIMode
   const llvm::opt::Arg *const CachedRTTIArg;
@@ -136,6 +136,8 @@
   ToolChain(const Driver &D, const llvm::Triple &T,
             const llvm::opt::ArgList &Args);
 
+  void setTripleEnvironment(llvm::Triple::EnvironmentType Env);
+
   virtual Tool *buildAssembler() const;
   virtual Tool *buildLinker() const;
   virtual Tool *getTool(Action::ActionClass AC) const;
Index: lib/CodeGen/CGObjCMac.cpp
===================================================================
--- lib/CodeGen/CGObjCMac.cpp
+++ lib/CodeGen/CGObjCMac.cpp
@@ -4885,10 +4885,7 @@
   }
 
   // Indicate whether we're compiling this to run on a simulator.
-  const llvm::Triple &Triple = CGM.getTarget().getTriple();
-  if ((Triple.isiOS() || Triple.isWatchOS()) &&
-      (Triple.getArch() == llvm::Triple::x86 ||
-       Triple.getArch() == llvm::Triple::x86_64))
+  if (CGM.getTarget().getTriple().isSimulatorEnvironment())
     Mod.addModuleFlag(llvm::Module::Error, "Objective-C Is Simulated",
                       eImageInfo_ImageIsSimulated);
 
Index: lib/Driver/ToolChain.cpp
===================================================================
--- lib/Driver/ToolChain.cpp
+++ lib/Driver/ToolChain.cpp
@@ -79,6 +79,12 @@
     getFilePaths().push_back(CandidateLibPath);
 }
 
+void ToolChain::setTripleEnvironment(llvm::Triple::EnvironmentType Env) {
+  Triple.setEnvironment(Env);
+  if (EffectiveTriple != llvm::Triple())
+    EffectiveTriple.setEnvironment(Env);
+}
+
 ToolChain::~ToolChain() {
 }
 
Index: lib/Driver/ToolChains/Darwin.h
===================================================================
--- lib/Driver/ToolChains/Darwin.h
+++ lib/Driver/ToolChains/Darwin.h
@@ -317,7 +317,7 @@
   // FIXME: Eliminate these ...Target functions and derive separate tool chains
   // for these targets and put version in constructor.
   void setTarget(DarwinPlatformKind Platform, unsigned Major, unsigned Minor,
-                 unsigned Micro) const {
+                 unsigned Micro, bool Simulator) const {
     // FIXME: For now, allow reinitialization as long as values don't
     // change. This will go away when we move away from argument translation.
     if (TargetInitialized && TargetPlatform == Platform &&
@@ -328,6 +328,8 @@
     TargetInitialized = true;
     TargetPlatform = Platform;
     TargetVersion = VersionTuple(Major, Minor, Micro);
+    if (Simulator)
+      const_cast<Darwin *>(this)->setTripleEnvironment(llvm::Triple::Simulator);
   }
 
   bool isTargetIPhoneOS() const {
Index: lib/Driver/ToolChains/Darwin.cpp
===================================================================
--- lib/Driver/ToolChains/Darwin.cpp
+++ lib/Driver/ToolChains/Darwin.cpp
@@ -1214,13 +1214,16 @@
   if (iOSVersion)
     ExplicitIOSDeploymentTargetStr = iOSVersion->getAsString(Args);
 
-  // Add a macro to differentiate between m(iphone|tv|watch)os-version-min=X.Y and
-  // -m(iphone|tv|watch)simulator-version-min=X.Y.
+  bool Simulator;
+  // Differentiate between m(iphone|tv|watch)os-version-min=X.Y and
+  // -m(iphone|tv|watch)simulator-version-min=X.Y using the 'simulator'
+  // environment in the triple.
   if (Args.hasArg(options::OPT_mios_simulator_version_min_EQ) ||
       Args.hasArg(options::OPT_mtvos_simulator_version_min_EQ) ||
       Args.hasArg(options::OPT_mwatchos_simulator_version_min_EQ))
-    Args.append(Args.MakeSeparateArg(nullptr, Opts.getOption(options::OPT_D),
-                                     " __APPLE_EMBEDDED_SIMULATOR__=1"));
+    Simulator = true;
+  else
+    Simulator = false;
 
   if (OSXVersion && (iOSVersion || TvOSVersion || WatchOSVersion)) {
     getDriver().Diag(diag::err_drv_argument_not_allowed_with)
@@ -1461,7 +1464,7 @@
                          getTriple().getArch() == llvm::Triple::x86_64))
     Platform = WatchOSSimulator;
 
-  setTarget(Platform, Major, Minor, Micro);
+  setTarget(Platform, Major, Minor, Micro, Simulator);
 
   if (const Arg *A = Args.getLastArg(options::OPT_isysroot)) {
     StringRef SDK = getSDKName(A->getValue());
Index: lib/Frontend/InitPreprocessor.cpp
===================================================================
--- lib/Frontend/InitPreprocessor.cpp
+++ lib/Frontend/InitPreprocessor.cpp
@@ -987,6 +987,11 @@
     Builder.defineMacro("__nullable", "_Nullable");
   }
 
+  // Add a macro to differentiate between regular iOS/tvOS/watchOS targets and
+  // the corresponding simulator targets.
+  if (TI.getTriple().isOSDarwin() && TI.getTriple().isSimulatorEnvironment())
+    Builder.defineMacro("__APPLE_EMBEDDED_SIMULATOR__", "1");
+
   // OpenMP definition
   // OpenMP 2.2:
   //   In implementations that support a preprocessor, the _OPENMP
Index: test/Driver/darwin-version.c
===================================================================
--- test/Driver/darwin-version.c
+++ test/Driver/darwin-version.c
@@ -41,7 +41,7 @@
 
 // RUN: %clang -target x86_64-apple-darwin -mios-simulator-version-min=11.0 -c -### %s 2>&1 | \
 // RUN: FileCheck --check-prefix=CHECK-VERSION-IOS10 %s
-// CHECK-VERSION-IOS10: x86_64-apple-ios11.0.0
+// CHECK-VERSION-IOS10: x86_64-apple-ios11.0.0-simulator
 
 // RUN: %clang -target arm64-apple-ios11.1 -c -### %s 2>&1 | \
 // RUN: FileCheck --check-prefix=CHECK-VERSION-IOS11 %s
@@ -85,13 +85,13 @@
 // CHECK-VERSION-TVOS83: "thumbv7-apple-tvos8.3.0"
 // RUN: %clang -target i386-apple-darwin -mtvos-simulator-version-min=8.3 -c %s -### 2>&1 | \
 // RUN:   FileCheck --check-prefix=CHECK-VERSION-TVSIM83 %s
-// CHECK-VERSION-TVSIM83: "i386-apple-tvos8.3.0"
+// CHECK-VERSION-TVSIM83: "i386-apple-tvos8.3.0-simulator"
 // RUN: %clang -target armv7k-apple-darwin -mwatchos-version-min=2.0 -c %s -### 2>&1 | \
 // RUN:   FileCheck --check-prefix=CHECK-VERSION-WATCHOS20 %s
 // CHECK-VERSION-WATCHOS20: "thumbv7k-apple-watchos2.0.0"
 // RUN: %clang -target i386-apple-darwin -mwatchos-simulator-version-min=2.0 -c %s -### 2>&1 | \
 // RUN:   FileCheck --check-prefix=CHECK-VERSION-WATCHSIM20 %s
-// CHECK-VERSION-WATCHSIM20: "i386-apple-watchos2.0.0"
+// CHECK-VERSION-WATCHSIM20: "i386-apple-watchos2.0.0-simulator"
 
 // Check environment variable gets interpreted correctly
 // RUN: env MACOSX_DEPLOYMENT_TARGET=10.5 IPHONEOS_DEPLOYMENT_TARGET=2.0 \