diff --git a/linux-x64/clang/include/llvm/Option/Arg.h b/linux-x64/clang/include/llvm/Option/Arg.h
index d3623a0..22e2bcf 100644
--- a/linux-x64/clang/include/llvm/Option/Arg.h
+++ b/linux-x64/clang/include/llvm/Option/Arg.h
@@ -58,6 +58,11 @@
   /// The argument values, as C strings.
   SmallVector<const char *, 2> Values;
 
+  /// If this arg was created through an alias, this is the original alias arg.
+  /// For example, *this might be "-finput-charset=utf-8" and Alias might
+  /// point to an arg representing "/source-charset:utf-8".
+  std::unique_ptr<Arg> Alias;
+
 public:
   Arg(const Option Opt, StringRef Spelling, unsigned Index,
       const Arg *BaseArg = nullptr);
@@ -70,7 +75,15 @@
   ~Arg();
 
   const Option &getOption() const { return Opt; }
+
+  /// Returns the used prefix and name of the option:
+  /// For `--foo=bar`, returns `--foo=`.
+  /// This is often the wrong function to call:
+  /// * Use `getValue()` to get `bar`.
+  /// * Use `getAsString()` to get a string suitable for printing an Arg in
+  ///   a diagnostic.
   StringRef getSpelling() const { return Spelling; }
+
   unsigned getIndex() const { return Index; }
 
   /// Return the base argument which generated this arg.
@@ -82,6 +95,11 @@
   }
   void setBaseArg(const Arg *BaseArg) { this->BaseArg = BaseArg; }
 
+  /// Args are converted to their unaliased form.  For args that originally
+  /// came from an alias, this returns the alias the arg was produced from.
+  const Arg* getAlias() const { return Alias.get(); }
+  void setAlias(std::unique_ptr<Arg> Alias) { this->Alias = std::move(Alias); }
+
   bool getOwnsValues() const { return OwnsValues; }
   void setOwnsValues(bool Value) const { OwnsValues = Value; }
 
@@ -119,8 +137,10 @@
   void print(raw_ostream &O) const;
   void dump() const;
 
-  /// Return a formatted version of the argument and
-  /// its values, for debugging and diagnostics.
+  /// Return a formatted version of the argument and its values, for
+  /// diagnostics. Since this is for diagnostics, if this Arg was produced
+  /// through an alias, this returns the string representation of the alias
+  /// that the user wrote.
   std::string getAsString(const ArgList &Args) const;
 };
 
diff --git a/linux-x64/clang/include/llvm/Option/ArgList.h b/linux-x64/clang/include/llvm/Option/ArgList.h
index a0cd2b8..74bfadc 100644
--- a/linux-x64/clang/include/llvm/Option/ArgList.h
+++ b/linux-x64/clang/include/llvm/Option/ArgList.h
@@ -301,10 +301,12 @@
   bool hasFlag(OptSpecifier Pos, OptSpecifier PosAlias, OptSpecifier Neg,
                bool Default = true) const;
 
-  /// AddLastArg - Render only the last argument match \p Id0, if present.
-  void AddLastArg(ArgStringList &Output, OptSpecifier Id0) const;
-  void AddLastArg(ArgStringList &Output, OptSpecifier Id0,
-                  OptSpecifier Id1) const;
+  /// Render only the last argument match \p Id0, if present.
+  template<typename ...OptSpecifiers>
+  void AddLastArg(ArgStringList &Output, OptSpecifiers ...Ids) const {
+    if (Arg *A = getLastArg(Ids...)) // Calls claim() on all Ids's Args.
+      A->render(*this, Output);
+  }
 
   /// AddAllArgsExcept - Render all arguments matching any of the given ids
   /// and not matching any of the excluded ids.
diff --git a/linux-x64/clang/include/llvm/Option/Option.h b/linux-x64/clang/include/llvm/Option/Option.h
index c11487e..33813d2 100644
--- a/linux-x64/clang/include/llvm/Option/Option.h
+++ b/linux-x64/clang/include/llvm/Option/Option.h
@@ -206,6 +206,11 @@
   ///                start.
   Arg *accept(const ArgList &Args, unsigned &Index, unsigned ArgSize) const;
 
+private:
+  Arg *acceptInternal(const ArgList &Args, unsigned &Index,
+                      unsigned ArgSize) const;
+
+public:
   void print(raw_ostream &O) const;
   void dump() const;
 };