Index: include/clang/Driver/ToolChain.h
===================================================================
--- include/clang/Driver/ToolChain.h
+++ include/clang/Driver/ToolChain.h
@@ -68,6 +68,7 @@
 private:
   const Driver &D;
   const llvm::Triple Triple;
+  mutable llvm::Triple EffectiveTriple;
   const llvm::opt::ArgList &Args;
   // We need to initialize CachedRTTIArg before CachedRTTIMode
   const llvm::opt::Arg *const CachedRTTIArg;
@@ -141,6 +142,15 @@
     return Triple.getTriple();
   }
 
+  /// \brief Set the toolchain's effective clang triple.
+  void setEffectiveTriple(llvm::Triple ET) const { EffectiveTriple = ET; }
+
+  /// \brief Get the toolchain's effective clang triple.
+  const llvm::Triple &getEffectiveTriple() const {
+    assert(!EffectiveTriple.getTriple().empty() && "No effective triple");
+    return EffectiveTriple;
+  }
+
   path_list &getFilePaths() { return FilePaths; }
   const path_list &getFilePaths() const { return FilePaths; }
 
@@ -432,6 +442,19 @@
   virtual VersionTuple getMSVCVersionFromExe() const { return VersionTuple(); }
 };
 
+/// Set a ToolChain's effective triple and clear it when the registration object
+/// passes out of scope.
+class RegisterEffectiveTriple {
+  const ToolChain &TC;
+
+public:
+  RegisterEffectiveTriple(const ToolChain &TC, llvm::Triple T) : TC(TC) {
+    TC.setEffectiveTriple(T);
+  }
+
+  ~RegisterEffectiveTriple() { TC.setEffectiveTriple(llvm::Triple()); }
+};
+
 } // end namespace driver
 } // end namespace clang
 
Index: lib/Driver/Driver.cpp
===================================================================
--- lib/Driver/Driver.cpp
+++ lib/Driver/Driver.cpp
@@ -2246,6 +2246,19 @@
     InputInfos.append(OffloadDependencesInputInfo.begin(),
                       OffloadDependencesInputInfo.end());
 
+  // Set the effective triple of the toolchain for the duration of this job.
+  llvm::Triple EffectiveTriple;
+  const ToolChain &ToolTC = T->getToolChain();
+  const ArgList &Args = C.getArgsForToolChain(TC, BoundArch);
+  if (InputInfos.size() != 1) {
+    EffectiveTriple = llvm::Triple(ToolTC.ComputeEffectiveClangTriple(Args));
+  } else {
+    // Pass along the input type if it can be unambiguously determined.
+    EffectiveTriple = llvm::Triple(
+        ToolTC.ComputeEffectiveClangTriple(Args, InputInfos[0].getType()));
+  }
+  RegisterEffectiveTriple TripleRAII(ToolTC, EffectiveTriple);
+
   // Determine the place to write output to, if any.
   InputInfo Result;
   if (JA->getType() == types::TY_Nothing)
Index: lib/Driver/ToolChain.cpp
===================================================================
--- lib/Driver/ToolChain.cpp
+++ lib/Driver/ToolChain.cpp
@@ -67,7 +67,8 @@
 
 ToolChain::ToolChain(const Driver &D, const llvm::Triple &T,
                      const ArgList &Args)
-    : D(D), Triple(T), Args(Args), CachedRTTIArg(GetRTTIArgument(Args)),
+    : D(D), Triple(T), EffectiveTriple(), Args(Args),
+      CachedRTTIArg(GetRTTIArgument(Args)),
       CachedRTTIMode(CalculateRTTIMode(Args, Triple, CachedRTTIArg)) {
   if (Arg *A = Args.getLastArg(options::OPT_mthread_model))
     if (!isThreadModelSupported(A->getValue()))
Index: lib/Driver/ToolChains.h
===================================================================
--- lib/Driver/ToolChains.h
+++ lib/Driver/ToolChains.h
@@ -312,9 +312,6 @@
   /// @name ToolChain Implementation
   /// {
 
-  std::string ComputeEffectiveClangTriple(const llvm::opt::ArgList &Args,
-                                          types::ID InputType) const override;
-
   types::ID LookupTypeForExtension(const char *Ext) const override;
 
   bool HasNativeLLVMSupport() const override;
Index: lib/Driver/ToolChains.cpp
===================================================================
--- lib/Driver/ToolChains.cpp
+++ lib/Driver/ToolChains.cpp
@@ -176,13 +176,6 @@
 
 MachO::~MachO() {}
 
-std::string MachO::ComputeEffectiveClangTriple(const ArgList &Args,
-                                               types::ID InputType) const {
-  llvm::Triple Triple(ComputeLLVMTriple(Args, InputType));
-
-  return Triple.getTriple();
-}
-
 std::string Darwin::ComputeEffectiveClangTriple(const ArgList &Args,
                                                 types::ID InputType) const {
   llvm::Triple Triple(ComputeLLVMTriple(Args, InputType));
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -791,7 +791,7 @@
 // -mfloat-abi=.
 arm::FloatABI arm::getARMFloatABI(const ToolChain &TC, const ArgList &Args) {
   const Driver &D = TC.getDriver();
-  const llvm::Triple Triple(TC.ComputeEffectiveClangTriple(Args));
+  const llvm::Triple &Triple = TC.getEffectiveTriple();
   auto SubArch = getARMSubArchVersionNumber(Triple);
   arm::FloatABI ABI = FloatABI::Invalid;
   if (Arg *A =
@@ -1192,8 +1192,7 @@
 
 void Clang::AddAArch64TargetArgs(const ArgList &Args,
                                  ArgStringList &CmdArgs) const {
-  std::string TripleStr = getToolChain().ComputeEffectiveClangTriple(Args);
-  llvm::Triple Triple(TripleStr);
+  const llvm::Triple &Triple = getToolChain().getEffectiveTriple();
 
   if (!Args.hasFlag(options::OPT_mred_zone, options::OPT_mno_red_zone, true) ||
       Args.hasArg(options::OPT_mkernel) ||
@@ -3844,8 +3843,8 @@
 void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                          const InputInfo &Output, const InputInfoList &Inputs,
                          const ArgList &Args, const char *LinkingOutput) const {
-  std::string TripleStr = getToolChain().ComputeEffectiveClangTriple(Args);
-  const llvm::Triple Triple(TripleStr);
+  const llvm::Triple &Triple = getToolChain().getEffectiveTriple();
+  const std::string &TripleStr = Triple.getTriple();
 
   bool KernelOrKext =
       Args.hasArg(options::OPT_mkernel, options::OPT_fapple_kext);
@@ -6501,9 +6500,8 @@
   assert(Inputs.size() == 1 && "Unexpected number of inputs.");
   const InputInfo &Input = Inputs[0];
 
-  std::string TripleStr =
-      getToolChain().ComputeEffectiveClangTriple(Args, Input.getType());
-  const llvm::Triple Triple(TripleStr);
+  const llvm::Triple &Triple = getToolChain().getEffectiveTriple();
+  const std::string &TripleStr = Triple.getTriple();
 
   // Don't warn about "clang -w -c foo.s"
   Args.ClaimAllArgs(options::OPT_w);
@@ -8879,9 +8877,7 @@
     break;
   case llvm::Triple::armeb:
   case llvm::Triple::thumbeb:
-    arm::appendEBLinkFlags(
-        Args, CmdArgs,
-        llvm::Triple(getToolChain().ComputeEffectiveClangTriple(Args)));
+    arm::appendEBLinkFlags(Args, CmdArgs, getToolChain().getEffectiveTriple());
     CmdArgs.push_back("-m");
     switch (getToolChain().getTriple().getEnvironment()) {
     case llvm::Triple::EABI:
@@ -9045,8 +9041,7 @@
                                        const char *LinkingOutput) const {
   claimNoWarnArgs(Args);
 
-  std::string TripleStr = getToolChain().ComputeEffectiveClangTriple(Args);
-  llvm::Triple Triple = llvm::Triple(TripleStr);
+  const llvm::Triple &Triple = getToolChain().getEffectiveTriple();
 
   ArgStringList CmdArgs;
 
@@ -9381,8 +9376,7 @@
       static_cast<const toolchains::Linux &>(getToolChain());
   const Driver &D = ToolChain.getDriver();
 
-  std::string TripleStr = getToolChain().ComputeEffectiveClangTriple(Args);
-  llvm::Triple Triple = llvm::Triple(TripleStr);
+  const llvm::Triple &Triple = getToolChain().getEffectiveTriple();
 
   const llvm::Triple::ArchType Arch = ToolChain.getArch();
   const bool isAndroid = ToolChain.getTriple().isAndroid();