Restructure how the driver communicates information about the

target Objective-C runtime down to the frontend:  break this
down into a single target runtime kind and version, and compute
all the relevant information from that.  This makes it
relatively painless to add support for new runtimes to the
compiler.  Make the new -cc1 flag, -fobjc-runtime=blah-x.y.z,
available at the driver level as a better and more general
alternative to -fgnu-runtime and -fnext-runtime.  This new
concept of an Objective-C runtime also encompasses what we
were previously separating out as the "Objective-C ABI", so
fragile vs. non-fragile runtimes are now really modelled as
different kinds of runtime, paving the way for better overall
differentiation.

As a sort of special case, continue to accept the -cc1 flag
-fobjc-runtime-has-weak, as a sop to PLCompatibilityWeak.

I won't go so far as to say "no functionality change", even
ignoring the new driver flag, but subtle changes in driver
semantics are almost certainly not intended.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158793 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 185 insertions, 189 deletions

diff --git a/lib/Driver/ToolChain.cpp b/lib/Driver/ToolChain.cpp
index 2e3523cf1d..21aefb6439 100644
--- a/lib/Driver/ToolChain.cpp
+++ b/lib/Driver/ToolChain.cpp
@@ -14,10 +14,10 @@
 #include "clang/Driver/ArgList.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/DriverDiagnostic.h"
-#include "clang/Driver/ObjCRuntime.h"
 #include "clang/Driver/Options.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "clang/Basic/ObjCRuntime.h"
 using namespace clang::driver;
 using namespace clang;
 
@@ -49,25 +49,9 @@ bool ToolChain::HasNativeLLVMSupport() const {
   return false;
 }
 
-void ToolChain::configureObjCRuntime(ObjCRuntime &runtime) const {
-  switch (runtime.getKind()) {
-  case ObjCRuntime::NeXT:
-    // Assume a minimal NeXT runtime.
-    runtime.HasARC = false;
-    runtime.HasWeak = false;
-    runtime.HasSubscripting = false;
-    runtime.HasTerminate = false;
-    return;
-
-  case ObjCRuntime::GNU:
-    // Assume a maximal GNU runtime.
-    runtime.HasARC = true;
-    runtime.HasWeak = true;
-    runtime.HasSubscripting = false; // to be added
-    runtime.HasTerminate = false; // to be added
-    return;
-  }
-  llvm_unreachable("invalid runtime kind!");
+ObjCRuntime ToolChain::getDefaultObjCRuntime(bool isNonFragile) const {
+  return ObjCRuntime(isNonFragile ? ObjCRuntime::GNU : ObjCRuntime::FragileGNU,
+                     VersionTuple());
 }
 
 /// getARMTargetCPU - Get the (LLVM) name of the ARM cpu we are targeting.
diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index 7c75583eea..1a0cd939dd 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -14,10 +14,10 @@
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/DriverDiagnostic.h"
-#include "clang/Driver/ObjCRuntime.h"
 #include "clang/Driver/OptTable.h"
 #include "clang/Driver/Option.h"
 #include "clang/Driver/Options.h"
+#include "clang/Basic/ObjCRuntime.h"
 #include "clang/Basic/Version.h"
 
 #include "llvm/ADT/SmallString.h"
@@ -42,9 +42,7 @@ using namespace clang;
 /// Darwin - Darwin tool chain for i386 and x86_64.
 
 Darwin::Darwin(const Driver &D, const llvm::Triple& Triple)
-  : ToolChain(D, Triple), TargetInitialized(false),
-    ARCRuntimeForSimulator(ARCSimulator_None),
-    LibCXXForSimulator(LibCXXSimulator_None)
+  : ToolChain(D, Triple), TargetInitialized(false)
 {
   // Compute the initial Darwin version from the triple
   unsigned Major, Minor, Micro;
@@ -80,42 +78,19 @@ bool Darwin::HasNativeLLVMSupport() const {
   return true;
 }
 
-bool Darwin::hasARCRuntime() const {
-  // FIXME: Remove this once there is a proper way to detect an ARC runtime
-  // for the simulator.
-  switch (ARCRuntimeForSimulator) {
-  case ARCSimulator_None:
-    break;
-  case ARCSimulator_HasARCRuntime:
-    return true;
-  case ARCSimulator_NoARCRuntime:
-    return false;
-  }
-
-  if (isTargetIPhoneOS())
-    return !isIPhoneOSVersionLT(5);
-  else
-    return !isMacosxVersionLT(10, 7);
-}
-
-bool Darwin::hasSubscriptingRuntime() const {
-    return !isTargetIPhoneOS() && !isMacosxVersionLT(10, 8);
-}
-
 /// Darwin provides an ARC runtime starting in MacOS X 10.7 and iOS 5.0.
-void Darwin::configureObjCRuntime(ObjCRuntime &runtime) const {
-  if (runtime.getKind() != ObjCRuntime::NeXT)
-    return ToolChain::configureObjCRuntime(runtime);
-
-  runtime.HasARC = runtime.HasWeak = hasARCRuntime();
-  runtime.HasSubscripting = hasSubscriptingRuntime();
-
-  // So far, objc_terminate is only available in iOS 5.
-  // FIXME: do the simulator logic properly.
-  if (!ARCRuntimeForSimulator && isTargetIPhoneOS())
-    runtime.HasTerminate = !isIPhoneOSVersionLT(5);
-  else
-    runtime.HasTerminate = false;
+ObjCRuntime Darwin::getDefaultObjCRuntime(bool isNonFragile) const {
+  if (isTargetIPhoneOS()) {
+    return ObjCRuntime(ObjCRuntime::iOS, TargetVersion);
+  } else if (TargetSimulatorVersionFromDefines != VersionTuple()) {
+    return ObjCRuntime(ObjCRuntime::iOS, TargetSimulatorVersionFromDefines);
+  } else {
+    if (isNonFragile) {
+      return ObjCRuntime(ObjCRuntime::MacOSX, TargetVersion);
+    } else {
+      return ObjCRuntime(ObjCRuntime::FragileMacOSX, TargetVersion);
+    }
+  }
 }
 
 /// Darwin provides a blocks runtime starting in MacOS X 10.6 and iOS 3.2.
@@ -313,7 +288,7 @@ void DarwinClang::AddLinkARCArgs(const ArgList &Args,
   else if (isTargetIPhoneOS())
     s += "iphoneos";
   // FIXME: Remove this once we depend fully on -mios-simulator-version-min.
-  else if (ARCRuntimeForSimulator != ARCSimulator_None)
+  else if (TargetSimulatorVersionFromDefines != VersionTuple())
     s += "iphonesimulator";
   else
     s += "macosx";
@@ -484,10 +459,7 @@ void Darwin::AddDeploymentTarget(DerivedArgList &Args) const {
         unsigned Major = 0, Minor = 0, Micro = 0;
         if (GetVersionFromSimulatorDefine(define, Major, Minor, Micro) &&
             Major < 10 && Minor < 100 && Micro < 100) {
-          ARCRuntimeForSimulator = Major < 5 ? ARCSimulator_NoARCRuntime
-                                             : ARCSimulator_HasARCRuntime;
-          LibCXXForSimulator = Major < 5 ? LibCXXSimulator_NotAvailable
-                                         : LibCXXSimulator_Available;
+          TargetSimulatorVersionFromDefines = VersionTuple(Major, Minor, Micro);
         }
         break;
       }
@@ -901,22 +873,19 @@ DerivedArgList *Darwin::TranslateArgs(const DerivedArgList &Args,
   // Validate the C++ standard library choice.
   CXXStdlibType Type = GetCXXStdlibType(*DAL);
   if (Type == ToolChain::CST_Libcxx) {
-    switch (LibCXXForSimulator) {
-    case LibCXXSimulator_None:
-      // Handle non-simulator cases.
-      if (isTargetIPhoneOS()) {
-        if (isIPhoneOSVersionLT(5, 0)) {
-          getDriver().Diag(clang::diag::err_drv_invalid_libcxx_deployment)
-            << "iOS 5.0";
-        }
-      }
-      break;
-    case LibCXXSimulator_NotAvailable:
+    // Check whether the target provides libc++.
+    StringRef where;
+
+    // Complain about targetting iOS < 5.0 in any way.
+    if ((TargetSimulatorVersionFromDefines != VersionTuple() &&
+         TargetSimulatorVersionFromDefines < VersionTuple(5, 0)) ||
+        (isTargetIPhoneOS() && isIPhoneOSVersionLT(5, 0))) {
+      where = "iOS 5.0";
+    }
+
+    if (where != StringRef()) {
       getDriver().Diag(clang::diag::err_drv_invalid_libcxx_deployment)
-        << "iOS 5.0";
-      break;
-    case LibCXXSimulator_Available:
-      break;
+        << where;
     }
   }
 
diff --git a/lib/Driver/ToolChains.h b/lib/Driver/ToolChains.h
index 3fdcba04dd..dce3b6d8e9 100644
--- a/lib/Driver/ToolChains.h
+++ b/lib/Driver/ToolChains.h
@@ -176,22 +176,6 @@ private:
   // the argument translation business.
   mutable bool TargetInitialized;
 
-  // FIXME: Remove this once there is a proper way to detect an ARC runtime
-  // for the simulator.
- public:
-  mutable enum {
-    ARCSimulator_None,
-    ARCSimulator_HasARCRuntime,
-    ARCSimulator_NoARCRuntime
-  } ARCRuntimeForSimulator;
-
-  mutable enum {
-    LibCXXSimulator_None,
-    LibCXXSimulator_NotAvailable,
-    LibCXXSimulator_Available
-  } LibCXXForSimulator;
-
-private:
   /// Whether we are targeting iPhoneOS target.
   mutable bool TargetIsIPhoneOS;
 
@@ -201,6 +185,12 @@ private:
   /// The OS version we are targeting.
   mutable VersionTuple TargetVersion;
 
+protected:
+  // FIXME: Remove this once there is a proper way to detect an ARC runtime
+  // for the simulator.
+  mutable VersionTuple TargetSimulatorVersionFromDefines;
+
+private:
   /// The default macosx-version-min of this tool chain; empty until
   /// initialized.
   std::string MacosxVersionMin;
@@ -209,9 +199,6 @@ private:
   /// initialized.
   std::string iOSVersionMin;
 
-  bool hasARCRuntime() const;
-  bool hasSubscriptingRuntime() const;
-
 private:
   void AddDeploymentTarget(DerivedArgList &Args) const;
 
@@ -258,7 +245,7 @@ public:
   bool isTargetMacOS() const {
     return !isTargetIOSSimulator() &&
            !isTargetIPhoneOS() &&
-           ARCRuntimeForSimulator == ARCSimulator_None;
+           TargetSimulatorVersionFromDefines == VersionTuple();
   }
 
   bool isTargetInitialized() const { return TargetInitialized; }
@@ -300,7 +287,7 @@ public:
 
   virtual bool HasNativeLLVMSupport() const;
 
-  virtual void configureObjCRuntime(ObjCRuntime &runtime) const;
+  virtual ObjCRuntime getDefaultObjCRuntime(bool isNonFragile) const;
   virtual bool hasBlocksRuntime() const;
 
   virtual DerivedArgList *TranslateArgs(const DerivedArgList &Args,
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 1669fd515d..aff9688818 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -16,11 +16,11 @@
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Job.h"
-#include "clang/Driver/ObjCRuntime.h"
 #include "clang/Driver/Option.h"
 #include "clang/Driver/Options.h"
 #include "clang/Driver/ToolChain.h"
 #include "clang/Driver/Util.h"
+#include "clang/Basic/ObjCRuntime.h"
 
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringSwitch.h"
@@ -1187,13 +1187,12 @@ void Clang::AddHexagonTargetArgs(const ArgList &Args,
 }
 
 static bool
-shouldUseExceptionTablesForObjCExceptions(unsigned objcABIVersion,
+shouldUseExceptionTablesForObjCExceptions(const ObjCRuntime &runtime,
                                           const llvm::Triple &Triple) {
   // We use the zero-cost exception tables for Objective-C if the non-fragile
   // ABI is enabled or when compiling for x86_64 and ARM on Snow Leopard and
   // later.
-
-  if (objcABIVersion >= 2)
+  if (runtime.isNonFragile())
     return true;
 
   if (!Triple.isOSDarwin())
@@ -1212,7 +1211,7 @@ shouldUseExceptionTablesForObjCExceptions(unsigned objcABIVersion,
 static void addExceptionArgs(const ArgList &Args, types::ID InputType,
                              const llvm::Triple &Triple,
                              bool KernelOrKext,
-                             unsigned objcABIVersion,
+                             const ObjCRuntime &objcRuntime,
                              ArgStringList &CmdArgs) {
   if (KernelOrKext) {
     // -mkernel and -fapple-kext imply no exceptions, so claim exception related
@@ -1258,7 +1257,7 @@ static void addExceptionArgs(const ArgList &Args, types::ID InputType,
     CmdArgs.push_back("-fobjc-exceptions");
 
     ShouldUseExceptionTables |=
-      shouldUseExceptionTablesForObjCExceptions(objcABIVersion, Triple);
+      shouldUseExceptionTablesForObjCExceptions(objcRuntime, Triple);
   }
 
   if (types::isCXX(InputType)) {
@@ -1444,8 +1443,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   CmdArgs.push_back(Args.MakeArgString(TripleStr));
 
   // Select the appropriate action.
-  bool IsRewriter = false;
-  bool IsModernRewriter = false;
+  RewriteKind rewriteKind = RK_None;
   
   if (isa<AnalyzeJobAction>(JA)) {
     assert(JA.getType() == types::TY_Plist && "Invalid output type.");
@@ -1517,10 +1515,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       CmdArgs.push_back("-emit-pch");
     } else if (JA.getType() == types::TY_RewrittenObjC) {
       CmdArgs.push_back("-rewrite-objc");
-      IsModernRewriter = true;
+      rewriteKind = RK_NonFragile;
     } else if (JA.getType() == types::TY_RewrittenLegacyObjC) {
       CmdArgs.push_back("-rewrite-objc");
-      IsRewriter = true;
+      rewriteKind = RK_Fragile;
     } else {
       assert(JA.getType() == types::TY_PP_Asm &&
              "Unexpected output type!");
@@ -2442,80 +2440,11 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (Args.hasArg(options::OPT_fno_inline_functions))
     CmdArgs.push_back("-fno-inline-functions");
 
-  // -fobjc-nonfragile-abi=0 is default.
-  ObjCRuntime objCRuntime;
-  unsigned objcABIVersion = 0;
-  bool NeXTRuntimeIsDefault
-    = (IsRewriter || IsModernRewriter ||
-       getToolChain().getTriple().isOSDarwin());
-  if (Args.hasFlag(options::OPT_fnext_runtime, options::OPT_fgnu_runtime,
-                   NeXTRuntimeIsDefault)) {
-    objCRuntime.setKind(ObjCRuntime::NeXT);
-  } else {
-    CmdArgs.push_back("-fgnu-runtime");
-    objCRuntime.setKind(ObjCRuntime::GNU);
-  }
-  getToolChain().configureObjCRuntime(objCRuntime);
-  if (objCRuntime.HasARC)
-    CmdArgs.push_back("-fobjc-runtime-has-arc");
-  if (objCRuntime.HasWeak)
-    CmdArgs.push_back("-fobjc-runtime-has-weak");
-  if (objCRuntime.HasTerminate)
-    CmdArgs.push_back("-fobjc-runtime-has-terminate");
-
-  // Compute the Objective-C ABI "version" to use. Version numbers are
-  // slightly confusing for historical reasons:
-  //   1 - Traditional "fragile" ABI
-  //   2 - Non-fragile ABI, version 1
-  //   3 - Non-fragile ABI, version 2
-  objcABIVersion = 1;
-  // If -fobjc-abi-version= is present, use that to set the version.
-  if (Arg *A = Args.getLastArg(options::OPT_fobjc_abi_version_EQ)) {
-    if (StringRef(A->getValue(Args)) == "1")
-      objcABIVersion = 1;
-    else if (StringRef(A->getValue(Args)) == "2")
-      objcABIVersion = 2;
-    else if (StringRef(A->getValue(Args)) == "3")
-      objcABIVersion = 3;
-    else
-      D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
-  } else {
-    // Otherwise, determine if we are using the non-fragile ABI.
-    bool NonFragileABIIsDefault = 
-      (IsModernRewriter || 
-       (!IsRewriter && getToolChain().IsObjCNonFragileABIDefault()));
-    if (Args.hasFlag(options::OPT_fobjc_nonfragile_abi,
-                     options::OPT_fno_objc_nonfragile_abi,
-                     NonFragileABIIsDefault)) {
-      // Determine the non-fragile ABI version to use.
-#ifdef DISABLE_DEFAULT_NONFRAGILEABI_TWO
-      unsigned NonFragileABIVersion = 1;
-#else
-      unsigned NonFragileABIVersion = 2;
-#endif
-
-      if (Arg *A = Args.getLastArg(
-            options::OPT_fobjc_nonfragile_abi_version_EQ)) {
-        if (StringRef(A->getValue(Args)) == "1")
-          NonFragileABIVersion = 1;
-        else if (StringRef(A->getValue(Args)) == "2")
-          NonFragileABIVersion = 2;
-        else
-          D.Diag(diag::err_drv_clang_unsupported)
-            << A->getAsString(Args);
-      }
-
-      objcABIVersion = 1 + NonFragileABIVersion;
-    } else {
-      objcABIVersion = 1;
-    }
-  }
+  ObjCRuntime objcRuntime = AddObjCRuntimeArgs(Args, CmdArgs, rewriteKind);
 
-  if (objcABIVersion == 1) {
-    CmdArgs.push_back("-fobjc-fragile-abi");
-  } else {
-    // -fobjc-dispatch-method is only relevant with the nonfragile-abi, and
-    // legacy is the default.
+  // -fobjc-dispatch-method is only relevant with the nonfragile-abi, and
+  // legacy is the default.
+  if (objcRuntime.isNonFragile()) {
     if (!Args.hasFlag(options::OPT_fobjc_legacy_dispatch,
                       options::OPT_fno_objc_legacy_dispatch,
                       getToolChain().IsObjCLegacyDispatchDefault())) {
@@ -2561,7 +2490,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   // -fobjc-infer-related-result-type is the default, except in the Objective-C
   // rewriter.
-  if (IsRewriter || IsModernRewriter)
+  if (rewriteKind != RK_None)
     CmdArgs.push_back("-fno-objc-infer-related-result-type");
 
   // Handle -fobjc-gc and -fobjc-gc-only. They are exclusive, and -fobjc-gc-only
@@ -2584,7 +2513,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   // Add exception args.
   addExceptionArgs(Args, InputType, getToolChain().getTriple(),
-                   KernelOrKext, objcABIVersion, CmdArgs);
+                   KernelOrKext, objcRuntime, CmdArgs);
 
   if (getToolChain().UseSjLjExceptions())
     CmdArgs.push_back("-fsjlj-exceptions");
@@ -2873,6 +2802,126 @@ void ClangAs::AddARMTargetArgs(const ArgList &Args,
     addFPMathArgs(D, A, Args, CmdArgs, getARMTargetCPU(Args, Triple));
 }
 
+/// Add options related to the Objective-C runtime/ABI.
+///
+/// Returns true if the runtime is non-fragile.
+ObjCRuntime Clang::AddObjCRuntimeArgs(const ArgList &args,
+                                      ArgStringList &cmdArgs,
+                                      RewriteKind rewriteKind) const {
+  // Look for the controlling runtime option.
+  Arg *runtimeArg = args.getLastArg(options::OPT_fnext_runtime,
+                                    options::OPT_fgnu_runtime,
+                                    options::OPT_fobjc_runtime_EQ);
+
+  // Just forward -fobjc-runtime= to the frontend.  This supercedes
+  // options about fragility.
+  if (runtimeArg &&
+      runtimeArg->getOption().matches(options::OPT_fobjc_runtime_EQ)) {
+    ObjCRuntime runtime;
+    StringRef value = runtimeArg->getValue(args);
+    if (runtime.tryParse(value)) {
+      getToolChain().getDriver().Diag(diag::err_drv_unknown_objc_runtime)
+        << value;
+    }
+
+    runtimeArg->render(args, cmdArgs);
+    return runtime;
+  }
+
+  // Otherwise, we'll need the ABI "version".  Version numbers are
+  // slightly confusing for historical reasons:
+  //   1 - Traditional "fragile" ABI
+  //   2 - Non-fragile ABI, version 1
+  //   3 - Non-fragile ABI, version 2
+  unsigned objcABIVersion = 1;
+  // If -fobjc-abi-version= is present, use that to set the version.
+  if (Arg *abiArg = args.getLastArg(options::OPT_fobjc_abi_version_EQ)) {
+    StringRef value = abiArg->getValue(args);
+    if (value == "1")
+      objcABIVersion = 1;
+    else if (value == "2")
+      objcABIVersion = 2;
+    else if (value == "3")
+      objcABIVersion = 3;
+    else
+      getToolChain().getDriver().Diag(diag::err_drv_clang_unsupported)
+        << value;
+  } else {
+    // Otherwise, determine if we are using the non-fragile ABI.
+    bool nonFragileABIIsDefault = 
+      (rewriteKind == RK_NonFragile || 
+       (rewriteKind == RK_None &&
+        getToolChain().IsObjCNonFragileABIDefault()));
+    if (args.hasFlag(options::OPT_fobjc_nonfragile_abi,
+                     options::OPT_fno_objc_nonfragile_abi,
+                     nonFragileABIIsDefault)) {
+      // Determine the non-fragile ABI version to use.
+#ifdef DISABLE_DEFAULT_NONFRAGILEABI_TWO
+      unsigned nonFragileABIVersion = 1;
+#else
+      unsigned nonFragileABIVersion = 2;
+#endif
+
+      if (Arg *abiArg = args.getLastArg(
+            options::OPT_fobjc_nonfragile_abi_version_EQ)) {
+        StringRef value = abiArg->getValue(args);
+        if (value == "1")
+          nonFragileABIVersion = 1;
+        else if (value == "2")
+          nonFragileABIVersion = 2;
+        else
+          getToolChain().getDriver().Diag(diag::err_drv_clang_unsupported)
+            << value;
+      }
+
+      objcABIVersion = 1 + nonFragileABIVersion;
+    } else {
+      objcABIVersion = 1;
+    }
+  }
+
+  // We don't actually care about the ABI version other than whether
+  // it's non-fragile.
+  bool isNonFragile = objcABIVersion != 1;
+
+  // If we have no runtime argument, ask the toolchain for its default runtime.
+  // However, the rewriter only really supports the Mac runtime, so assume that.
+  ObjCRuntime runtime;
+  if (!runtimeArg) {
+    switch (rewriteKind) {
+    case RK_None:
+      runtime = getToolChain().getDefaultObjCRuntime(isNonFragile);
+      break;
+    case RK_Fragile:
+      runtime = ObjCRuntime(ObjCRuntime::FragileMacOSX, VersionTuple());
+      break;
+    case RK_NonFragile:
+      runtime = ObjCRuntime(ObjCRuntime::MacOSX, VersionTuple());
+      break;
+    }
+
+  // -fnext-runtime
+  } else if (runtimeArg->getOption().matches(options::OPT_fnext_runtime)) {
+    // On Darwin, make this use the default behavior for the toolchain.
+    if (getToolChain().getTriple().isOSDarwin()) {
+      runtime = getToolChain().getDefaultObjCRuntime(isNonFragile);
+
+    // Otherwise, build for a generic macosx port.
+    } else {
+      runtime = ObjCRuntime(ObjCRuntime::MacOSX, VersionTuple());
+    }
+
+  // -fgnu-runtime
+  } else {
+    assert(runtimeArg->getOption().matches(options::OPT_fgnu_runtime));
+    runtime = ObjCRuntime(ObjCRuntime::GNU, VersionTuple());
+  }
+
+  cmdArgs.push_back(args.MakeArgString(
+                                 "-fobjc-runtime=" + runtime.getAsString()));
+  return runtime;
+}
+
 void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
                            const InputInfo &Output,
                            const InputInfoList &Inputs,
@@ -4340,11 +4389,11 @@ void darwin::Link::ConstructJob(Compilation &C, const JobAction &JA,
       // If we don't have ARC or subscripting runtime support, link in the
       // runtime stubs.  We have to do this *before* adding any of the normal
       // linker inputs so that its initializer gets run first.
-      ObjCRuntime runtime;
-      getDarwinToolChain().configureObjCRuntime(runtime);
+      ObjCRuntime runtime =
+        getDarwinToolChain().getDefaultObjCRuntime(/*nonfragile*/ true);
       // We use arclite library for both ARC and subscripting support.
-      if ((!runtime.HasARC && isObjCAutoRefCount(Args)) ||
-          !runtime.HasSubscripting)
+      if ((!runtime.hasARC() && isObjCAutoRefCount(Args)) ||
+          !runtime.hasSubscripting())
         getDarwinToolChain().AddLinkARCArgs(Args, CmdArgs);
     }
     CmdArgs.push_back("-framework");
diff --git a/lib/Driver/Tools.h b/lib/Driver/Tools.h
index aa15f3551c..0fc0690db5 100644
--- a/lib/Driver/Tools.h
+++ b/lib/Driver/Tools.h
@@ -18,6 +18,8 @@
 #include "llvm/Support/Compiler.h"
 
 namespace clang {
+  class ObjCRuntime;
+
 namespace driver {
   class Driver;
 
@@ -44,6 +46,11 @@ namespace tools {
     void AddX86TargetArgs(const ArgList &Args, ArgStringList &CmdArgs) const;
     void AddHexagonTargetArgs (const ArgList &Args, ArgStringList &CmdArgs) const;
 
+    enum RewriteKind { RK_None, RK_Fragile, RK_NonFragile };
+
+    ObjCRuntime AddObjCRuntimeArgs(const ArgList &args, ArgStringList &cmdArgs,
+                                   RewriteKind rewrite) const;
+
   public:
     Clang(const ToolChain &TC) : Tool("clang", "clang frontend", TC) {}