13 files changed, 265 insertions, 170 deletions

diff --git a/include/clang/Driver/ArgList.h b/include/clang/Driver/ArgList.h
index e2b4cf47fd..fea6dd8ef2 100644
--- a/include/clang/Driver/ArgList.h
+++ b/include/clang/Driver/ArgList.h
@@ -36,30 +36,23 @@ namespace driver {
     typedef arglist_type::const_reverse_iterator const_reverse_iterator;
 
   private:
-    /// List of argument strings used by the contained Args.
-    ///
-    /// This is mutable since we treat the ArgList as being the list
-    /// of Args, and allow routines to add new strings (to have a
-    /// convenient place to store the memory) via MakeIndex.
-    mutable ArgStringList ArgStrings;
-
-    /// Strings for synthesized arguments.
-    ///
-    /// This is mutable since we treat the ArgList as being the list
-    /// of Args, and allow routines to add new strings (to have a
-    /// convenient place to store the memory) via MakeIndex.
-    mutable std::list<std::string> SynthesizedStrings;
-
     /// The full list of arguments.
-    arglist_type Args;
+    arglist_type &Args;
 
-    /// The number of original input argument strings.
-    unsigned NumInputArgStrings;
+  protected:
+    ArgList(arglist_type &Args);
 
   public:
-    ArgList(const char **ArgBegin, const char **ArgEnd);
-    ArgList(const ArgList &);
-    ~ArgList();
+    virtual ~ArgList();
+
+    /// @name Arg Access
+    /// @{
+
+    /// append - Append \arg A to the arg list.
+    void append(Arg *A);
+
+    arglist_type &getArgs() { return Args; }
+    const arglist_type &getArgs() const { return Args; }
 
     unsigned size() const { return Args.size(); }
 
@@ -74,16 +67,6 @@ namespace driver {
     
     const_reverse_iterator rbegin() const { return Args.rbegin(); }
     const_reverse_iterator rend() const { return Args.rend(); }
-    
-    /// append - Append \arg A to the arg list, taking ownership.
-    void append(Arg *A);
-
-    /// getArgString - Return the input argument string at \arg Index.
-    const char *getArgString(unsigned Index) const { return ArgStrings[Index]; }
-
-    /// getNumInputArgStrings - Return the number of original input
-    /// argument strings.
-    unsigned getNumInputArgStrings() const { return NumInputArgStrings; }
 
     /// hasArg - Does the arg list contain any option matching \arg Id.
     ///
@@ -98,36 +81,8 @@ namespace driver {
     Arg *getLastArg(options::ID Id, bool Claim=true) const;
     Arg *getLastArg(options::ID Id0, options::ID Id1, bool Claim=true) const;
 
-    /// @name Arg Synthesis
-    /// @{
-
-  private:    
-    /// MakeIndex - Get an index for the given string(s).
-    unsigned MakeIndex(const char *String0) const;
-    unsigned MakeIndex(const char *String0, const char *String1) const;
-
-  public:
-    /// MakeArgString - Construct a constant string pointer whose
-    /// lifetime will match that of the ArgList.
-    const char *MakeArgString(const char *Str) const;
-
-    /// MakeFlagArg - Construct a new FlagArg for the given option
-    /// \arg Id.
-    Arg *MakeFlagArg(const Option *Opt) const;
-
-    /// MakePositionalArg - Construct a new Positional arg for the
-    /// given option \arg Id, with the provided \arg Value.
-    Arg *MakePositionalArg(const Option *Opt, const char *Value) const;
-
-    /// MakeSeparateArg - Construct a new Positional arg for the
-    /// given option \arg Id, with the provided \arg Value.
-    Arg *MakeSeparateArg(const Option *Opt, const char *Value) const;
-
-    /// MakeJoinedArg - Construct a new Positional arg for the
-    /// given option \arg Id, with the provided \arg Value.
-    Arg *MakeJoinedArg(const Option *Opt, const char *Value) const;
-
-    /// @}
+    /// getArgString - Return the input argument string at \arg Index.
+    virtual const char *getArgString(unsigned Index) const = 0;
     /// @name Translation Utilities
     /// @{
 
@@ -156,7 +111,114 @@ namespace driver {
                          options::ID Id1) const;
 
     /// @}
+    /// @name Arg Synthesis
+    /// @{
+
+    /// MakeArgString - Construct a constant string pointer whose
+    /// lifetime will match that of the ArgList.
+    virtual const char *MakeArgString(const char *Str) const = 0;
+
+    /// @}
   };
+
+  class InputArgList : public ArgList  {
+  private:
+    /// The internal list of arguments.
+    arglist_type ActualArgs;
+
+    /// List of argument strings used by the contained Args.
+    ///
+    /// This is mutable since we treat the ArgList as being the list
+    /// of Args, and allow routines to add new strings (to have a
+    /// convenient place to store the memory) via MakeIndex.
+    mutable ArgStringList ArgStrings;
+
+    /// Strings for synthesized arguments.
+    ///
+    /// This is mutable since we treat the ArgList as being the list
+    /// of Args, and allow routines to add new strings (to have a
+    /// convenient place to store the memory) via MakeIndex.
+    mutable std::list<std::string> SynthesizedStrings;
+
+    /// The number of original input argument strings.
+    unsigned NumInputArgStrings;
+
+  public:
+    InputArgList(const char **ArgBegin, const char **ArgEnd);
+    InputArgList(const ArgList &);
+    ~InputArgList();
+
+    virtual const char *getArgString(unsigned Index) const { 
+      return ArgStrings[Index]; 
+    }
+
+    /// getNumInputArgStrings - Return the number of original input
+    /// argument strings.
+    unsigned getNumInputArgStrings() const { return NumInputArgStrings; }
+
+    /// @name Arg Synthesis
+    /// @{
+
+  public:
+    /// MakeIndex - Get an index for the given string(s).
+    unsigned MakeIndex(const char *String0) const;
+    unsigned MakeIndex(const char *String0, const char *String1) const;
+
+    virtual const char *MakeArgString(const char *Str) const;
+
+    /// @}
+  };
+
+  /// DerivedArgList - An ordered collection of driver arguments,
+  /// whose storage may be in another argument list.
+  class DerivedArgList : public ArgList {
+    InputArgList &BaseArgs;
+
+    /// The internal list of arguments.
+    arglist_type ActualArgs;
+
+    /// The list of arguments we synthesized.
+    arglist_type SynthesizedArgs;
+
+    /// Is this only a proxy for the base ArgList?
+    bool OnlyProxy;
+
+  public:
+    /// Construct a new derived arg list from \arg BaseArgs.
+    ///
+    /// \param OnlyProxy - If true, this is only a proxy for the base
+    /// list (to adapt the type), and it's Args list is unused.
+    DerivedArgList(InputArgList &BaseArgs, bool OnlyProxy);
+    ~DerivedArgList();
+
+    virtual const char *getArgString(unsigned Index) const {
+      return BaseArgs.getArgString(Index); 
+    }
+
+    /// @name Arg Synthesis
+    /// @{
+
+    virtual const char *MakeArgString(const char *Str) const;
+
+    /// MakeFlagArg - Construct a new FlagArg for the given option
+    /// \arg Id.
+    Arg *MakeFlagArg(const Option *Opt) const;
+
+    /// MakePositionalArg - Construct a new Positional arg for the
+    /// given option \arg Id, with the provided \arg Value.
+    Arg *MakePositionalArg(const Option *Opt, const char *Value) const;
+
+    /// MakeSeparateArg - Construct a new Positional arg for the
+    /// given option \arg Id, with the provided \arg Value.
+    Arg *MakeSeparateArg(const Option *Opt, const char *Value) const;
+
+    /// MakeJoinedArg - Construct a new Positional arg for the
+    /// given option \arg Id, with the provided \arg Value.
+    Arg *MakeJoinedArg(const Option *Opt, const char *Value) const;
+
+    /// @}
+  };
+
 } // end namespace driver
 } // end namespace clang
 
diff --git a/include/clang/Driver/Compilation.h b/include/clang/Driver/Compilation.h
index 1a6d7b02ea..4985f30ad5 100644
--- a/include/clang/Driver/Compilation.h
+++ b/include/clang/Driver/Compilation.h
@@ -22,8 +22,9 @@ namespace llvm {
 
 namespace clang {
 namespace driver {
-  class ArgList;
+  class DerivedArgList;
   class Driver;
+  class InputArgList;
   class JobList;
   class ToolChain;
 
@@ -37,7 +38,7 @@ class Compilation {
   ToolChain &DefaultToolChain;
 
   /// The original (untranslated) input argument list.
-  ArgList *Args;
+  InputArgList *Args;
 
   /// The list of actions.
   ActionList Actions;
@@ -46,7 +47,7 @@ class Compilation {
   JobList Jobs;
 
   /// Cache of translated arguments for a particular tool chain.
-  llvm::DenseMap<const ToolChain*, ArgList*> TCArgs;
+  llvm::DenseMap<const ToolChain*, DerivedArgList*> TCArgs;
 
   /// Temporary files which should be removed on exit.
   ArgStringList TempFiles;
@@ -55,24 +56,24 @@ class Compilation {
   ArgStringList ResultFiles;
 
 public:
-  Compilation(Driver &D, ToolChain &DefaultToolChain, ArgList *Args);
+  Compilation(Driver &D, ToolChain &DefaultToolChain, InputArgList *Args);
   ~Compilation();
 
   const Driver &getDriver() const { return TheDriver; }
 
   const ToolChain &getDefaultToolChain() const { return DefaultToolChain; }
 
-  const ArgList &getArgs() const { return *Args; }
+  const InputArgList &getArgs() const { return *Args; }
 
   ActionList &getActions() { return Actions; }
   const ActionList &getActions() const { return Actions; }
 
   JobList &getJobs() { return Jobs; }
 
-  /// getArgsForToolChain - Return the argument list, possibly
-  /// translated by the tool chain \arg TC (or by the default tool
-  /// chain, if TC is not specified).
-  const ArgList &getArgsForToolChain(const ToolChain *TC = 0);
+  /// getArgsForToolChain - Return the derived argument list for the
+  /// tool chain \arg TC (or the default tool chain, if TC is not
+  /// specified).
+  const DerivedArgList &getArgsForToolChain(const ToolChain *TC = 0);
 
   /// addTempFile - Add a file to remove on exit, and returns its
   /// argument.
diff --git a/include/clang/Driver/Driver.h b/include/clang/Driver/Driver.h
index 5ba737379d..4935acc66d 100644
--- a/include/clang/Driver/Driver.h
+++ b/include/clang/Driver/Driver.h
@@ -27,6 +27,7 @@ namespace driver {
   class ArgList;
   class Compilation;
   class HostInfo;
+  class InputArgList;
   class InputInfo;
   class JobAction;
   class OptTable;
@@ -130,7 +131,7 @@ public:
 
   /// ParseArgStrings - Parse the given list of strings into an
   /// ArgList.
-  ArgList *ParseArgStrings(const char **ArgBegin, const char **ArgEnd);
+  InputArgList *ParseArgStrings(const char **ArgBegin, const char **ArgEnd);
 
   /// BuildActions - Construct the list of actions to perform for the
   /// given arguments, which are only done for a single architecture.
diff --git a/include/clang/Driver/Option.h b/include/clang/Driver/Option.h
index 57e15cb00f..79b512e607 100644
--- a/include/clang/Driver/Option.h
+++ b/include/clang/Driver/Option.h
@@ -22,7 +22,7 @@ using llvm::dyn_cast_or_null;
 namespace clang {
 namespace driver {
   class Arg;
-  class ArgList;
+  class InputArgList;
   class OptionGroup;
   
   /// Option - Abstract representation for a single form of driver
@@ -140,7 +140,7 @@ namespace driver {
     /// If the option accepts the current argument, accept() sets
     /// Index to the position where argument parsing should resume
     /// (even if the argument is missing values).
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const = 0;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const = 0;
     
     void dump() const;
 
@@ -153,7 +153,7 @@ namespace driver {
   public:
     OptionGroup(options::ID ID, const char *Name, const OptionGroup *Group);
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::GroupClass; 
@@ -168,7 +168,7 @@ namespace driver {
   public:
     InputOption();
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::InputClass; 
@@ -181,7 +181,7 @@ namespace driver {
   public:
     UnknownOption();
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::UnknownClass; 
@@ -196,7 +196,7 @@ namespace driver {
     FlagOption(options::ID ID, const char *Name, const OptionGroup *Group, 
                const Option *Alias);
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::FlagClass; 
@@ -209,7 +209,7 @@ namespace driver {
     JoinedOption(options::ID ID, const char *Name, const OptionGroup *Group, 
                  const Option *Alias);
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::JoinedClass; 
@@ -222,7 +222,7 @@ namespace driver {
     SeparateOption(options::ID ID, const char *Name, const OptionGroup *Group, 
                    const Option *Alias);
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::SeparateClass; 
@@ -235,7 +235,7 @@ namespace driver {
     CommaJoinedOption(options::ID ID, const char *Name, 
                       const OptionGroup *Group, const Option *Alias);
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::CommaJoinedClass; 
@@ -256,7 +256,7 @@ namespace driver {
 
     unsigned getNumArgs() const { return NumArgs; }
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::MultiArgClass; 
@@ -271,7 +271,7 @@ namespace driver {
     JoinedOrSeparateOption(options::ID ID, const char *Name, 
                            const OptionGroup *Group, const Option *Alias);
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::JoinedOrSeparateClass; 
@@ -286,7 +286,7 @@ namespace driver {
     JoinedAndSeparateOption(options::ID ID, const char *Name, 
                             const OptionGroup *Group, const Option *Alias);
 
-    virtual Arg *accept(const ArgList &Args, unsigned &Index) const;
+    virtual Arg *accept(const InputArgList &Args, unsigned &Index) const;
 
     static bool classof(const Option *O) { 
       return O->getKind() == Option::JoinedAndSeparateClass; 
diff --git a/include/clang/Driver/Options.h b/include/clang/Driver/Options.h
index efa32d929c..d5bc4d5b8a 100644
--- a/include/clang/Driver/Options.h
+++ b/include/clang/Driver/Options.h
@@ -15,8 +15,8 @@ namespace driver {
 namespace options {
   enum ID {
     OPT_INVALID = 0, // This is not an option ID.
-    OPT_INPUT,      // Reserved ID for input option.
-    OPT_UNKNOWN,    // Reserved ID for unknown option.
+    OPT_INPUT,       // Reserved ID for input option.
+    OPT_UNKNOWN,     // Reserved ID for unknown option.
 #define OPTION(NAME, ID, KIND, GROUP, ALIAS, FLAGS, PARAM) OPT_##ID,
 #include "clang/Driver/Options.def"
     LastOption
@@ -25,7 +25,7 @@ namespace options {
 }
   
   class Arg;
-  class ArgList;
+  class InputArgList;
   class Option;
 
   /// OptTable - Provide access to the Option info table.
@@ -70,7 +70,7 @@ namespace options {
     /// \return - The parsed argument, or 0 if the argument is missing
     /// values (in which case Index still points at the conceptual
     /// next argument string to parse).
-    Arg *ParseOneArg(const ArgList &Args, unsigned &Index) const;
+    Arg *ParseOneArg(const InputArgList &Args, unsigned &Index) const;
   };
 }
 }
diff --git a/include/clang/Driver/ToolChain.h b/include/clang/Driver/ToolChain.h
index 99d9bcb3cb..e85d7a7e20 100644
--- a/include/clang/Driver/ToolChain.h
+++ b/include/clang/Driver/ToolChain.h
@@ -16,9 +16,10 @@
 
 namespace clang {
 namespace driver {
-  class ArgList;
   class Compilation;
+  class DerivedArgList;
   class HostInfo;
+  class InputArgList;
   class JobAction;
   class Tool;
 
@@ -63,10 +64,7 @@ public:
 
   /// TranslateArgs - Create a new derived argument list for any
   /// argument translations this ToolChain may wish to perform.
-  ///
-  /// The client implementation is free to return Args directly if no
-  /// translations need to be performed.
-  virtual ArgList *TranslateArgs(ArgList &Args) const = 0;
+  virtual DerivedArgList *TranslateArgs(InputArgList &Args) const = 0;
 
   /// SelectTool - Choose a tool to use to handle the action \arg JA.
   virtual Tool &SelectTool(const Compilation &C, const JobAction &JA) const = 0;
diff --git a/lib/Driver/ArgList.cpp b/lib/Driver/ArgList.cpp
index d74e3bd59d..bd3aab351d 100644
--- a/lib/Driver/ArgList.cpp
+++ b/lib/Driver/ArgList.cpp
@@ -13,22 +13,13 @@
 
 using namespace clang::driver;
 
-ArgList::ArgList(const char **ArgBegin, const char **ArgEnd) 
-  : NumInputArgStrings(ArgEnd - ArgBegin) 
-{
-  ArgStrings.append(ArgBegin, ArgEnd);
+ArgList::ArgList(arglist_type &_Args) : Args(_Args) {
 }
 
 ArgList::~ArgList() {
-  for (iterator it = begin(), ie = end(); it != ie; ++it)
-    delete *it;
 }
 
 void ArgList::append(Arg *A) {
-  if (A->getOption().isUnsupported()) {
-    assert(0 && "FIXME: unsupported unsupported.");
-  }
-
   Args.push_back(A);
 }
 
@@ -68,46 +59,6 @@ bool ArgList::hasFlag(options::ID Pos, options::ID Neg, bool Default) const {
   return Default;
 }
 
-unsigned ArgList::MakeIndex(const char *String0) const {
-  unsigned Index = ArgStrings.size();
-
-  // Tuck away so we have a reliable const char *.
-  SynthesizedStrings.push_back(String0);
-  ArgStrings.push_back(SynthesizedStrings.back().c_str());
-
-  return Index;
-}
-
-unsigned ArgList::MakeIndex(const char *String0, const char *String1) const {
-  unsigned Index0 = MakeIndex(String0);
-  unsigned Index1 = MakeIndex(String1);
-  assert(Index0 + 1 == Index1 && "Unexpected non-consecutive indices!");
-  (void) Index1;
-  return Index0;
-}
-
-const char *ArgList::MakeArgString(const char *Str) const {
-  return getArgString(MakeIndex(Str));
-}
-
-Arg *ArgList::MakeFlagArg(const Option *Opt) const {
-  return new FlagArg(Opt, MakeIndex(Opt->getName()));
-}
-
-Arg *ArgList::MakePositionalArg(const Option *Opt, const char *Value) const {
-  return new PositionalArg(Opt, MakeIndex(Value));
-}
-
-Arg *ArgList::MakeSeparateArg(const Option *Opt, const char *Value) const {
-  return new SeparateArg(Opt, MakeIndex(Opt->getName(), Value), 1);
-}
-
-Arg *ArgList::MakeJoinedArg(const Option *Opt, const char *Value) const {
-  std::string Joined(Opt->getName());
-  Joined += Value;
-  return new JoinedArg(Opt, MakeIndex(Joined.c_str()));
-}
-
 void ArgList::AddLastArg(ArgStringList &Output, options::ID Id) const {
   if (Arg *A = getLastArg(Id)) {
     A->claim();
@@ -175,3 +126,80 @@ void ArgList::AddAllArgValues(ArgStringList &Output, options::ID Id0,
     }
   }
 }
+
+//
+
+InputArgList::InputArgList(const char **ArgBegin, const char **ArgEnd) 
+  : ArgList(ActualArgs), NumInputArgStrings(ArgEnd - ArgBegin) 
+{
+  ArgStrings.append(ArgBegin, ArgEnd);
+}
+
+InputArgList::~InputArgList() {
+  // An InputArgList always owns its arguments.
+  for (iterator it = begin(), ie = end(); it != ie; ++it)
+    delete *it;
+}
+
+unsigned InputArgList::MakeIndex(const char *String0) const {
+  unsigned Index = ArgStrings.size();
+
+  // Tuck away so we have a reliable const char *.
+  SynthesizedStrings.push_back(String0);
+  ArgStrings.push_back(SynthesizedStrings.back().c_str());
+
+  return Index;
+}
+
+unsigned InputArgList::MakeIndex(const char *String0, 
+                                 const char *String1) const {
+  unsigned Index0 = MakeIndex(String0);
+  unsigned Index1 = MakeIndex(String1);
+  assert(Index0 + 1 == Index1 && "Unexpected non-consecutive indices!");
+  (void) Index1;
+  return Index0;
+}
+
+const char *InputArgList::MakeArgString(const char *Str) const {
+  return getArgString(MakeIndex(Str));
+}
+
+//
+
+DerivedArgList::DerivedArgList(InputArgList &_BaseArgs, bool _OnlyProxy)
+  : ArgList(_OnlyProxy ? _BaseArgs.getArgs() : ActualArgs),
+    BaseArgs(_BaseArgs), OnlyProxy(_OnlyProxy)
+{
+}
+
+DerivedArgList::~DerivedArgList() {
+  // We only own the arguments we explicitly synthesized.
+  for (iterator it = SynthesizedArgs.begin(), ie = SynthesizedArgs.end(); 
+       it != ie; ++it)
+    delete *it;
+}
+
+const char *DerivedArgList::MakeArgString(const char *Str) const {
+  return BaseArgs.MakeArgString(Str);
+}
+
+Arg *DerivedArgList::MakeFlagArg(const Option *Opt) const {
+  return new FlagArg(Opt, BaseArgs.MakeIndex(Opt->getName()));
+}
+
+Arg *DerivedArgList::MakePositionalArg(const Option *Opt, 
+                                       const char *Value) const {
+  return new PositionalArg(Opt, BaseArgs.MakeIndex(Value));
+}
+
+Arg *DerivedArgList::MakeSeparateArg(const Option *Opt, 
+                                     const char *Value) const {
+  return new SeparateArg(Opt, BaseArgs.MakeIndex(Opt->getName(), Value), 1);
+}
+
+Arg *DerivedArgList::MakeJoinedArg(const Option *Opt, 
+                                   const char *Value) const {
+  std::string Joined(Opt->getName());
+  Joined += Value;
+  return new JoinedArg(Opt, BaseArgs.MakeIndex(Joined.c_str()));
+}
diff --git a/lib/Driver/Compilation.cpp b/lib/Driver/Compilation.cpp
index 2165bb7401..1e044c6b8f 100644
--- a/lib/Driver/Compilation.cpp
+++ b/lib/Driver/Compilation.cpp
@@ -23,7 +23,7 @@ using namespace clang::driver;
 
 Compilation::Compilation(Driver &D,
                          ToolChain &_DefaultToolChain,
-                         ArgList *_Args) 
+                         InputArgList *_Args) 
   : TheDriver(D), DefaultToolChain(_DefaultToolChain), Args(_Args) {
 }
 
@@ -31,12 +31,9 @@ Compilation::~Compilation() {
   delete Args;
   
   // Free any derived arg lists.
-  for (llvm::DenseMap<const ToolChain*, ArgList*>::iterator 
-         it = TCArgs.begin(), ie = TCArgs.end(); it != ie; ++it) {
-    ArgList *A = it->second;
-    if (A != Args)
-      delete Args;
-  }
+  for (llvm::DenseMap<const ToolChain*, DerivedArgList*>::iterator 
+         it = TCArgs.begin(), ie = TCArgs.end(); it != ie; ++it)
+    delete it->second;
 
   // Free the actions, if built.
   for (ActionList::iterator it = Actions.begin(), ie = Actions.end(); 
@@ -44,11 +41,11 @@ Compilation::~Compilation() {
     delete *it;
 }
 
-const ArgList &Compilation::getArgsForToolChain(const ToolChain *TC) {
+const DerivedArgList &Compilation::getArgsForToolChain(const ToolChain *TC) {
   if (!TC)
     TC = &DefaultToolChain;
 
-  ArgList *&Entry = TCArgs[TC];
+  DerivedArgList *&Entry = TCArgs[TC];
   if (!Entry)
     Entry = TC->TranslateArgs(*Args);
 
diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 2ffd641910..85d76c8c20 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -56,9 +56,10 @@ Driver::~Driver() {
   delete Host;
 }
 
-ArgList *Driver::ParseArgStrings(const char **ArgBegin, const char **ArgEnd) {
+InputArgList *Driver::ParseArgStrings(const char **ArgBegin, 
+                                      const char **ArgEnd) {
   llvm::PrettyStackTraceString CrashInfo("Command line argument parsing");
-  ArgList *Args = new ArgList(ArgBegin, ArgEnd);
+  InputArgList *Args = new InputArgList(ArgBegin, ArgEnd);
   
   // FIXME: Handle '@' args (or at least error on them).
 
@@ -171,7 +172,7 @@ Compilation *Driver::BuildCompilation(int argc, const char **argv) {
     }
   }
 
-  ArgList *Args = ParseArgStrings(Start, End);
+  InputArgList *Args = ParseArgStrings(Start, End);
 
   Host = GetHostInfo(HostTriple);
 
@@ -851,8 +852,8 @@ void Driver::BuildJobsForAction(Compilation &C,
     }
     llvm::errs() << "], output: " << Result.getAsString() << "\n";
   } else {
-    const ArgList &TCArgs = C.getArgsForToolChain(TC);
-    T.ConstructJob(C, *JA, *Dest, Result, InputInfos, TCArgs, LinkingOutput);
+    T.ConstructJob(C, *JA, *Dest, Result, InputInfos, 
+                   C.getArgsForToolChain(TC), LinkingOutput);
   }
 }
 
diff --git a/lib/Driver/OptTable.cpp b/lib/Driver/OptTable.cpp
index 4524ecedd4..baaa886fec 100644
--- a/lib/Driver/OptTable.cpp
+++ b/lib/Driver/OptTable.cpp
@@ -208,7 +208,7 @@ static inline bool operator<(const char *Name, struct Info &I) {
   return StrCmpOptionName(Name, I.Name) == -1;
 }
 
-Arg *OptTable::ParseOneArg(const ArgList &Args, unsigned &Index) const {
+Arg *OptTable::ParseOneArg(const InputArgList &Args, unsigned &Index) const {
   unsigned Prev = Index;
   const char *Str = Args.getArgString(Index);
 
diff --git a/lib/Driver/Option.cpp b/lib/Driver/Option.cpp
index dc681c7295..6ea02aaf40 100644
--- a/lib/Driver/Option.cpp
+++ b/lib/Driver/Option.cpp
@@ -107,7 +107,7 @@ OptionGroup::OptionGroup(options::ID ID, const char *Name,
   : Option(Option::GroupClass, ID, Name, Group, 0) {
 }
 
-Arg *OptionGroup::accept(const ArgList &Args, unsigned &Index) const {
+Arg *OptionGroup::accept(const InputArgList &Args, unsigned &Index) const {
   assert(0 && "accept() should never be called on an OptionGroup");
   return 0;
 }
@@ -116,7 +116,7 @@ InputOption::InputOption()
   : Option(Option::InputClass, options::OPT_INPUT, "<input>", 0, 0) {
 }
 
-Arg *InputOption::accept(const ArgList &Args, unsigned &Index) const {
+Arg *InputOption::accept(const InputArgList &Args, unsigned &Index) const {
   assert(0 && "accept() should never be called on an InputOption");
   return 0;
 }
@@ -125,7 +125,7 @@ UnknownOption::UnknownOption()
   : Option(Option::UnknownClass, options::OPT_UNKNOWN, "<unknown>", 0, 0) {
 }
 
-Arg *UnknownOption::accept(const ArgList &Args, unsigned &Index) const {
+Arg *UnknownOption::accept(const InputArgList &Args, unsigned &Index) const {
   assert(0 && "accept() should never be called on an UnknownOption");
   return 0;
 }
@@ -135,7 +135,7 @@ FlagOption::FlagOption(options::ID ID, const char *Name,
   : Option(Option::FlagClass, ID, Name, Group, Alias) {
 }
 
-Arg *FlagOption::accept(const ArgList &Args, unsigned &Index) const {
+Arg *FlagOption::accept(const InputArgList &Args, unsigned &Index) const {
   // Matches iff this is an exact match.  
   // FIXME: Avoid strlen.
   if (strlen(getName()) != strlen(Args.getArgString(Index)))
@@ -149,7 +149,7 @@ JoinedOption::JoinedOption(options::ID ID, const char *Name,
   : Option(Option::JoinedClass, ID, Name, Group, Alias) {
 }
 
-Arg *JoinedOption::accept(const ArgList &Args, unsigned &Index) const {
+Arg *JoinedOption::accept(const InputArgList &Args, unsigned &Index) const {
   // Always matches.
   return new JoinedArg(this, Index++);
 }
@@ -160,7 +160,8 @@ CommaJoinedOption::CommaJoinedOption(options::ID ID, const char *Name,
   : Option(Option::CommaJoinedClass, ID, Name, Group, Alias) {
 }
 
-Arg *CommaJoinedOption::accept(const ArgList &Args, unsigned &Index) const {
+Arg *CommaJoinedOption::accept(const InputArgList &Args, 
+                               unsigned &Index) const {
   // Always matches. We count the commas now so we can answer
   // getNumValues easily.
   
@@ -175,7 +176,7 @@ SeparateOption::SeparateOption(options::ID ID, const char *Name,
   : Option(Option::SeparateClass, ID, Name, Group, Alias) {
 }
 
-Arg *SeparateOption::accept(const ArgList &Args, unsigned &Index) const {
+Arg *SeparateOption::accept(const InputArgList &Args, unsigned &Index) const {
   // Matches iff this is an exact match.  
   // FIXME: Avoid strlen.
   if (strlen(getName()) != strlen(Args.getArgString(Index)))
@@ -195,7 +196,7 @@ MultiArgOption::MultiArgOption(options::ID ID, const char *Name,
   assert(NumArgs > 1  && "Invalid MultiArgOption!");
 }
 
-Arg *MultiArgOption::accept(const ArgList &Args, unsigned &Index) const {
+Arg *MultiArgOption::accept(const InputArgList &Args, unsigned &Index) const {
   // Matches iff this is an exact match.  
   // FIXME: Avoid strlen.
   if (strlen(getName()) != strlen(Args.getArgString(Index)))
@@ -214,7 +215,7 @@ JoinedOrSeparateOption::JoinedOrSeparateOption(options::ID ID, const char *Name,
   : Option(Option::JoinedOrSeparateClass, ID, Name, Group, Alias) {
 }
 
-Arg *JoinedOrSeparateOption::accept(const ArgList &Args, 
+Arg *JoinedOrSeparateOption::accept(const InputArgList &Args, 
                                     unsigned &Index) const {
   // If this is not an exact match, it is a joined arg.
   // FIXME: Avoid strlen.
@@ -236,7 +237,7 @@ JoinedAndSeparateOption::JoinedAndSeparateOption(options::ID ID,
   : Option(Option::JoinedAndSeparateClass, ID, Name, Group, Alias) {
 }
 
-Arg *JoinedAndSeparateOption::accept(const ArgList &Args, 
+Arg *JoinedAndSeparateOption::accept(const InputArgList &Args, 
                                      unsigned &Index) const {
   // Always matches.
 
diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index c8df6c09e5..898f12e8f2 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -9,6 +9,8 @@
 
 #include "ToolChains.h"
 
+#include "clang/Driver/Arg.h"
+#include "clang/Driver/ArgList.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/HostInfo.h"
 
@@ -122,9 +124,9 @@ Tool &Darwin_X86::SelectTool(const Compilation &C,
   return *T;
 }
 
-ArgList *Darwin_X86::TranslateArgs(ArgList &Args) const { 
+DerivedArgList *Darwin_X86::TranslateArgs(InputArgList &Args) const { 
   // FIXME: Implement!
-  return &Args;
+  return new DerivedArgList(Args, true);
 } 
 
 bool Darwin_X86::IsMathErrnoDefault() const { 
@@ -223,3 +225,7 @@ const char *Generic_GCC::GetDefaultRelocationModel() const {
 const char *Generic_GCC::GetForcedPicModel() const {
   return 0;
 }
+
+DerivedArgList *Generic_GCC::TranslateArgs(InputArgList &Args) const {
+  return new DerivedArgList(Args, true);
+}
diff --git a/lib/Driver/ToolChains.h b/lib/Driver/ToolChains.h
index ea1661a970..305737b9a9 100644
--- a/lib/Driver/ToolChains.h
+++ b/lib/Driver/ToolChains.h
@@ -33,7 +33,7 @@ public:
               const char *OS);
   ~Generic_GCC();
 
-  virtual ArgList *TranslateArgs(ArgList &Args) const { return &Args; }
+  virtual DerivedArgList *TranslateArgs(InputArgList &Args) const;
 
   virtual Tool &SelectTool(const Compilation &C, const JobAction &JA) const;
 
@@ -62,7 +62,7 @@ public:
              const unsigned (&GCCVersion)[3]);
   ~Darwin_X86();
 
-  virtual ArgList *TranslateArgs(ArgList &Args) const;
+  virtual DerivedArgList *TranslateArgs(InputArgList &Args) const;
 
   virtual Tool &SelectTool(const Compilation &C, const JobAction &JA) const;