llvm/utils/TableGen/LLVMCConfigurationEmitter.cpp

//===- LLVMCConfigurationEmitter.cpp - Generate LLVMC config ----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open
// Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This tablegen backend is responsible for emitting LLVMC configuration code.
//
//===----------------------------------------------------------------------===//

#include "LLVMCConfigurationEmitter.h"
#include "Record.h"

#include "llvm/ADT/IntrusiveRefCntPtr.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/Support/Streams.h"
#include <algorithm>
#include <cassert>
#include <functional>
#include <stdexcept>
#include <string>
#include <typeinfo>
using namespace llvm;

namespace {

//===----------------------------------------------------------------------===//
/// Typedefs

typedef std::vector<Record*> RecordVector;
typedef std::vector<std::string> StrVector;

//===----------------------------------------------------------------------===//
/// Constants

// Indentation strings.
const char * Indent1 = "    ";
const char * Indent2 = "        ";
const char * Indent3 = "            ";
const char * Indent4 = "                ";

// Default help string.
const char * DefaultHelpString = "NO HELP MESSAGE PROVIDED";

// Name for the "sink" option.
const char * SinkOptionName = "AutoGeneratedSinkOption";

//===----------------------------------------------------------------------===//
/// Helper functions

int InitPtrToInt(const Init* ptr) {
  const IntInit& val = dynamic_cast<const IntInit&>(*ptr);
  return val.getValue();
}

const std::string& InitPtrToString(const Init* ptr) {
  const StringInit& val = dynamic_cast<const StringInit&>(*ptr);
  return val.getValue();
}

const ListInit& InitPtrToList(const Init* ptr) {
  const ListInit& val = dynamic_cast<const ListInit&>(*ptr);
  return val;
}

const DagInit& InitPtrToDag(const Init* ptr) {
  const DagInit& val = dynamic_cast<const DagInit&>(*ptr);
  return val;
}

// checkNumberOfArguments - Ensure that the number of args in d is
// less than or equal to min_arguments, otherwise throw an exception.
void checkNumberOfArguments (const DagInit* d, unsigned min_arguments) {
  if (d->getNumArgs() < min_arguments)
    throw "Property " + d->getOperator()->getAsString()
      + " has too few arguments!";
}

// isDagEmpty - is this DAG marked with an empty marker?
bool isDagEmpty (const DagInit* d) {
  return d->getOperator()->getAsString() == "empty";
}

//===----------------------------------------------------------------------===//
/// Back-end specific code

// A command-line option can have one of the following types:
//
// Alias - an alias for another option.
//
// Switch - a simple switch without arguments, e.g. -O2
//
// Parameter - an option that takes one(and only one) argument, e.g. -o file,
// --output=file
//
// ParameterList - same as Parameter, but more than one occurence
// of the option is allowed, e.g. -lm -lpthread
//
// Prefix - argument is everything after the prefix,
// e.g. -Wa,-foo,-bar, -DNAME=VALUE
//
// PrefixList - same as Prefix, but more than one option occurence is
// allowed.

namespace OptionType {
  enum OptionType { Alias, Switch,
                    Parameter, ParameterList, Prefix, PrefixList};
}

bool IsListOptionType (OptionType::OptionType t) {
  return (t == OptionType::ParameterList || t == OptionType::PrefixList);
}

// Code duplication here is necessary because one option can affect
// several tools and those tools may have different actions associated
// with this option. GlobalOptionDescriptions are used to generate
// the option registration code, while ToolOptionDescriptions are used
// to generate tool-specific code.

/// OptionDescription - Base class for option descriptions.
struct OptionDescription {
  OptionType::OptionType Type;
  std::string Name;

  OptionDescription(OptionType::OptionType t = OptionType::Switch,
                    const std::string& n = "")
  : Type(t), Name(n)
  {}

  const char* GenTypeDeclaration() const {
    switch (Type) {
    case OptionType::Alias:
      return "cl::alias";
    case OptionType::PrefixList:
    case OptionType::ParameterList:
      return "cl::list<std::string>";
    case OptionType::Switch:
      return "cl::opt<bool>";
    case OptionType::Parameter:
    case OptionType::Prefix:
    default:
      return "cl::opt<std::string>";
    }
  }

  // Escape commas and other symbols not allowed in the C++ variable
  // names. Makes it possible to use options with names like "Wa,"
  // (useful for prefix options).
  std::string EscapeVariableName(const std::string& Var) const {
    std::string ret;
    for (unsigned i = 0; i != Var.size(); ++i) {
      char cur_char = Var[i];
      if (cur_char == ',') {
        ret += "_comma_";
      }
      else if (cur_char == '+') {
        ret += "_plus_";
      }
      else if (cur_char == ',') {
        ret += "_comma_";
      }
      else {
        ret.push_back(cur_char);
      }
    }
    return ret;
  }

  std::string GenVariableName() const {
    const std::string& EscapedName = EscapeVariableName(Name);
    switch (Type) {
    case OptionType::Alias:
     return "AutoGeneratedAlias" + EscapedName;
    case OptionType::Switch:
      return "AutoGeneratedSwitch" + EscapedName;
    case OptionType::Prefix:
      return "AutoGeneratedPrefix" + EscapedName;
    case OptionType::PrefixList:
      return "AutoGeneratedPrefixList" + EscapedName;
    case OptionType::Parameter:
      return "AutoGeneratedParameter" + EscapedName;
    case OptionType::ParameterList:
    default:
      return "AutoGeneratedParameterList" + EscapedName;
    }
  }

};

// Global option description.

namespace GlobalOptionDescriptionFlags {
  enum GlobalOptionDescriptionFlags { Required = 0x1 };
}

struct GlobalOptionDescription : public OptionDescription {
  std::string Help;
  unsigned Flags;

  // We need to provide a default constructor because
  // StringMap can only store DefaultConstructible objects.
  GlobalOptionDescription() : OptionDescription(), Flags(0)
  {}

  GlobalOptionDescription (OptionType::OptionType t, const std::string& n,
                           const std::string& h = DefaultHelpString)
    : OptionDescription(t, n), Help(h), Flags(0)
  {}

  bool isRequired() const {
    return Flags & GlobalOptionDescriptionFlags::Required;
  }
  void setRequired() {
    Flags |= GlobalOptionDescriptionFlags::Required;
  }

  /// Merge - Merge two option descriptions.
  void Merge (const GlobalOptionDescription& other)
  {
    if (other.Type != Type)
      throw "Conflicting definitions for the option " + Name + "!";

    if (Help == DefaultHelpString)
      Help = other.Help;
    else if (other.Help != DefaultHelpString) {
      llvm::cerr << "Warning: more than one help string defined for option "
        + Name + "\n";
    }

    Flags |= other.Flags;
  }
};

/// GlobalOptionDescriptions - A GlobalOptionDescription array
/// together with some flags affecting generation of option
/// declarations.
struct GlobalOptionDescriptions {
  typedef StringMap<GlobalOptionDescription> container_type;
  typedef container_type::const_iterator const_iterator;

  /// Descriptions - A list of GlobalOptionDescriptions.
  container_type Descriptions;
  /// HasSink - Should the emitter generate a "cl::sink" option?
  bool HasSink;

  /// FindOption - exception-throwing wrapper for find().
  const GlobalOptionDescription& FindOption(const std::string& OptName) const {
    const_iterator I = Descriptions.find(OptName);
    if (I != Descriptions.end())
      return I->second;
    else
      throw OptName + ": no such option!";
  }

  /// insertDescription - Insert new GlobalOptionDescription into
  /// GlobalOptionDescriptions list
  void insertDescription (const GlobalOptionDescription& o)
  {
    container_type::iterator I = Descriptions.find(o.Name);
    if (I != Descriptions.end()) {
      GlobalOptionDescription& D = I->second;
      D.Merge(o);
    }
    else {
      Descriptions[o.Name] = o;
    }
  }

  // Support for STL-style iteration
  const_iterator begin() const { return Descriptions.begin(); }
  const_iterator end() const { return Descriptions.end(); }
};


// Tool-local option description.

// Properties without arguments are implemented as flags.
namespace ToolOptionDescriptionFlags {
  enum ToolOptionDescriptionFlags { StopCompilation = 0x1,
                                    Forward = 0x2, UnpackValues = 0x4};
}
namespace OptionPropertyType {
  enum OptionPropertyType { AppendCmd, ForwardAs, OutputSuffix };
}

typedef std::pair<OptionPropertyType::OptionPropertyType, std::string>
OptionProperty;
typedef SmallVector<OptionProperty, 4> OptionPropertyList;

struct ToolOptionDescription : public OptionDescription {
  unsigned Flags;
  OptionPropertyList Props;

  // StringMap can only store DefaultConstructible objects
  ToolOptionDescription() : OptionDescription(), Flags(0) {}

  ToolOptionDescription (OptionType::OptionType t, const std::string& n)
    : OptionDescription(t, n)
  {}

  // Various boolean properties
  bool isStopCompilation() const {
    return Flags & ToolOptionDescriptionFlags::StopCompilation;
  }
  void setStopCompilation() {
    Flags |= ToolOptionDescriptionFlags::StopCompilation;
  }

  bool isForward() const {
    return Flags & ToolOptionDescriptionFlags::Forward;
  }
  void setForward() {
    Flags |= ToolOptionDescriptionFlags::Forward;
  }

  bool isUnpackValues() const {
    return Flags & ToolOptionDescriptionFlags::UnpackValues;
  }
  void setUnpackValues() {
    Flags |= ToolOptionDescriptionFlags::UnpackValues;
  }

  void AddProperty (OptionPropertyType::OptionPropertyType t,
                    const std::string& val)
  {
    Props.push_back(std::make_pair(t, val));
  }
};

typedef StringMap<ToolOptionDescription> ToolOptionDescriptions;

// Tool information record

namespace ToolFlags {
  enum ToolFlags { Join = 0x1, Sink = 0x2 };
}

struct ToolProperties : public RefCountedBase<ToolProperties> {
  std::string Name;
  Init* CmdLine;
  StrVector InLanguage;
  std::string OutLanguage;
  std::string OutputSuffix;
  unsigned Flags;
  ToolOptionDescriptions OptDescs;

  // Various boolean properties
  void setSink()      { Flags |= ToolFlags::Sink; }
  bool isSink() const { return Flags & ToolFlags::Sink; }
  void setJoin()      { Flags |= ToolFlags::Join; }
  bool isJoin() const { return Flags & ToolFlags::Join; }

  // Default ctor here is needed because StringMap can only store
  // DefaultConstructible objects
  ToolProperties() : CmdLine(0), Flags(0) {}
  ToolProperties (const std::string& n) : Name(n), CmdLine(0), Flags(0) {}
};


/// ToolPropertiesList - A list of Tool information records
/// IntrusiveRefCntPtrs are used here because StringMap has no copy
/// constructor (and we want to avoid copying ToolProperties anyway).
typedef std::vector<IntrusiveRefCntPtr<ToolProperties> > ToolPropertiesList;


/// CollectOptionProperties - Function object for iterating over a
/// list (usually, a DAG) of option property records.
class CollectOptionProperties {
private:
  // Implementation details.

  /// OptionPropertyHandler - a function that extracts information
  /// about a given option property from its DAG representation.
  typedef void (CollectOptionProperties::* OptionPropertyHandler)
  (const DagInit*);

  /// OptionPropertyHandlerMap - A map from option property names to
  /// option property handlers
  typedef StringMap<OptionPropertyHandler> OptionPropertyHandlerMap;

  static OptionPropertyHandlerMap optionPropertyHandlers_;
  static bool staticMembersInitialized_;

  /// This is where the information is stored

  /// toolProps_ -  Properties of the current Tool.
  ToolProperties* toolProps_;
  /// optDescs_ - OptionDescriptions table (used to register options
  /// globally).
  GlobalOptionDescription& optDesc_;

public:

  explicit CollectOptionProperties(ToolProperties* TP,
                                   GlobalOptionDescription& OD)
    : toolProps_(TP), optDesc_(OD)
  {
    if (!staticMembersInitialized_) {
      optionPropertyHandlers_["append_cmd"] =
        &CollectOptionProperties::onAppendCmd;
      optionPropertyHandlers_["forward"] =
        &CollectOptionProperties::onForward;
      optionPropertyHandlers_["forward_as"] =
        &CollectOptionProperties::onForwardAs;
      optionPropertyHandlers_["help"] =
        &CollectOptionProperties::onHelp;
      optionPropertyHandlers_["output_suffix"] =
        &CollectOptionProperties::onOutputSuffix;
      optionPropertyHandlers_["required"] =
        &CollectOptionProperties::onRequired;
      optionPropertyHandlers_["stop_compilation"] =
        &CollectOptionProperties::onStopCompilation;
      optionPropertyHandlers_["unpack_values"] =
        &CollectOptionProperties::onUnpackValues;

      staticMembersInitialized_ = true;
    }
  }

  /// operator() - Gets called for every option property; Just forwards
  /// to the corresponding property handler.
  void operator() (Init* i) {
    const DagInit& option_property = InitPtrToDag(i);
    const std::string& option_property_name
      = option_property.getOperator()->getAsString();
    OptionPropertyHandlerMap::iterator method
      = optionPropertyHandlers_.find(option_property_name);

    if (method != optionPropertyHandlers_.end()) {
      OptionPropertyHandler h = method->second;
      (this->*h)(&option_property);
    }
    else {
      throw "Unknown option property: " + option_property_name + "!";
    }
  }

private:

  /// Option property handlers --
  /// Methods that handle properties that are common for all types of
  /// options (like append_cmd, stop_compilation)

  void onAppendCmd (const DagInit* d) {
    checkNumberOfArguments(d, 1);
    checkToolProps(d);
    const std::string& cmd = InitPtrToString(d->getArg(0));

    toolProps_->OptDescs[optDesc_.Name].
      AddProperty(OptionPropertyType::AppendCmd, cmd);
  }

  void onOutputSuffix (const DagInit* d) {
    checkNumberOfArguments(d, 1);
    checkToolProps(d);
    const std::string& suf = InitPtrToString(d->getArg(0));

    if (toolProps_->OptDescs[optDesc_.Name].Type != OptionType::Switch)
      throw "Option " + optDesc_.Name
        + " can't have 'output_suffix' property since it isn't a switch!";

    toolProps_->OptDescs[optDesc_.Name].AddProperty
      (OptionPropertyType::OutputSuffix, suf);
  }

  void onForward (const DagInit* d) {
    checkNumberOfArguments(d, 0);
    checkToolProps(d);
    toolProps_->OptDescs[optDesc_.Name].setForward();
  }

  void onForwardAs (const DagInit* d) {
    checkNumberOfArguments(d, 1);
    checkToolProps(d);
    const std::string& cmd = InitPtrToString(d->getArg(0));

    toolProps_->OptDescs[optDesc_.Name].
      AddProperty(OptionPropertyType::ForwardAs, cmd);
  }

  void onHelp (const DagInit* d) {
    checkNumberOfArguments(d, 1);
    const std::string& help_message = InitPtrToString(d->getArg(0));

    optDesc_.Help = help_message;
  }

  void onRequired (const DagInit* d) {
    checkNumberOfArguments(d, 0);
    checkToolProps(d);
    optDesc_.setRequired();
  }

  void onStopCompilation (const DagInit* d) {
    checkNumberOfArguments(d, 0);
    checkToolProps(d);
    if (optDesc_.Type != OptionType::Switch)
      throw std::string("Only options of type Switch can stop compilation!");
    toolProps_->OptDescs[optDesc_.Name].setStopCompilation();
  }

  void onUnpackValues (const DagInit* d) {
    checkNumberOfArguments(d, 0);
    checkToolProps(d);
    toolProps_->OptDescs[optDesc_.Name].setUnpackValues();
  }

  // Helper functions

  /// checkToolProps - Throw an error if toolProps_ == 0.
  void checkToolProps(const DagInit* d) {
    if (!d)
      throw "Option property " + d->getOperator()->getAsString()
        + " can't be used in this context";
  }

};

CollectOptionProperties::OptionPropertyHandlerMap
CollectOptionProperties::optionPropertyHandlers_;

bool CollectOptionProperties::staticMembersInitialized_ = false;


/// processOptionProperties - Go through the list of option
/// properties and call a corresponding handler for each.
void processOptionProperties (const DagInit* d, ToolProperties* t,
                              GlobalOptionDescription& o) {
  checkNumberOfArguments(d, 2);
  DagInit::const_arg_iterator B = d->arg_begin();
  // Skip the first argument: it's always the option name.
  ++B;
  std::for_each(B, d->arg_end(), CollectOptionProperties(t, o));
}

/// AddOption - A function object wrapper for
/// processOptionProperties. Used by CollectProperties and
/// CollectPropertiesFromOptionList.
class AddOption {
private:
  GlobalOptionDescriptions& OptDescs_;
  ToolProperties* ToolProps_;

public:
  explicit AddOption(GlobalOptionDescriptions& OD, ToolProperties* TP = 0)
    : OptDescs_(OD), ToolProps_(TP)
  {}

  void operator()(const Init* i) {
    const DagInit& d = InitPtrToDag(i);
    checkNumberOfArguments(&d, 2);

    const OptionType::OptionType Type =
      getOptionType(d.getOperator()->getAsString());
    const std::string& Name = InitPtrToString(d.getArg(0));

    GlobalOptionDescription OD(Type, Name);
    if (Type != OptionType::Alias) {
      processOptionProperties(&d, ToolProps_, OD);
      if (ToolProps_) {
        ToolProps_->OptDescs[Name].Type = Type;
        ToolProps_->OptDescs[Name].Name = Name;
      }
    }
    else {
      OD.Help = InitPtrToString(d.getArg(1));
    }
    OptDescs_.insertDescription(OD);
  }

private:
  OptionType::OptionType getOptionType(const std::string& T) const {
    if (T == "alias_option")
      return OptionType::Alias;
    else if (T == "switch_option")
      return OptionType::Switch;
    else if (T == "parameter_option")
      return OptionType::Parameter;
    else if (T == "parameter_list_option")
      return OptionType::ParameterList;
    else if (T == "prefix_option")
      return OptionType::Prefix;
    else if (T == "prefix_list_option")
      return OptionType::PrefixList;
    else
      throw "Unknown option type: " + T + '!';
  }
};


/// CollectProperties - Function object for iterating over a list of
/// tool property records.
class CollectProperties {
private:

  // Implementation details

  /// PropertyHandler - a function that extracts information
  /// about a given tool property from its DAG representation
  typedef void (CollectProperties::*PropertyHandler)(const DagInit*);

  /// PropertyHandlerMap - A map from property names to property
  /// handlers.
  typedef StringMap<PropertyHandler> PropertyHandlerMap;

  // Static maps from strings to CollectProperties methods("handlers")
  static PropertyHandlerMap propertyHandlers_;
  static bool staticMembersInitialized_;


  /// This is where the information is stored

  /// toolProps_ -  Properties of the current Tool.
  ToolProperties& toolProps_;
  /// optDescs_ - OptionDescriptions table (used to register options
  /// globally).
  GlobalOptionDescriptions& optDescs_;

public:

  explicit CollectProperties (ToolProperties& p, GlobalOptionDescriptions& d)
    : toolProps_(p), optDescs_(d)
  {
    if (!staticMembersInitialized_) {
      propertyHandlers_["cmd_line"] = &CollectProperties::onCmdLine;
      propertyHandlers_["in_language"] = &CollectProperties::onInLanguage;
      propertyHandlers_["join"] = &CollectProperties::onJoin;
      propertyHandlers_["out_language"] = &CollectProperties::onOutLanguage;
      propertyHandlers_["output_suffix"] = &CollectProperties::onOutputSuffix;
      propertyHandlers_["parameter_option"]
        = &CollectProperties::addOption;
      propertyHandlers_["parameter_list_option"] =
        &CollectProperties::addOption;
      propertyHandlers_["prefix_option"] = &CollectProperties::addOption;
      propertyHandlers_["prefix_list_option"] =
        &CollectProperties::addOption;
      propertyHandlers_["sink"] = &CollectProperties::onSink;
      propertyHandlers_["switch_option"] = &CollectProperties::addOption;
      propertyHandlers_["alias_option"] = &CollectProperties::addOption;

      staticMembersInitialized_ = true;
    }
  }

  /// operator() - Gets called for every tool property; Just forwards
  /// to the corresponding property handler.
  void operator() (Init* i) {
    const DagInit& d = InitPtrToDag(i);
    const std::string& property_name = d.getOperator()->getAsString();
    PropertyHandlerMap::iterator method
      = propertyHandlers_.find(property_name);

    if (method != propertyHandlers_.end()) {
      PropertyHandler h = method->second;
      (this->*h)(&d);
    }
    else {
      throw "Unknown tool property: " + property_name + "!";
    }
  }

private:

  /// Property handlers --
  /// Functions that extract information about tool properties from
  /// DAG representation.

  void onCmdLine (const DagInit* d) {
    checkNumberOfArguments(d, 1);
    toolProps_.CmdLine = d->getArg(0);
  }

  void onInLanguage (const DagInit* d) {
    checkNumberOfArguments(d, 1);
    Init* arg = d->getArg(0);

    // Find out the argument's type.
    if (typeid(*arg) == typeid(StringInit)) {
      // It's a string.
      toolProps_.InLanguage.push_back(InitPtrToString(arg));
    }
    else {
      // It's a list.
      const ListInit& lst = InitPtrToList(arg);
      StrVector& out = toolProps_.InLanguage;

      // Copy strings to the output vector.
      for (ListInit::const_iterator B = lst.begin(), E = lst.end();
           B != E; ++B) {
        out.push_back(InitPtrToString(*B));
      }

      // Remove duplicates.
      std::sort(out.begin(), out.end());
      StrVector::iterator newE = std::unique(out.begin(), out.end());
      out.erase(newE, out.end());
    }
  }

  void onJoin (const DagInit* d) {
    checkNumberOfArguments(d, 0);
    toolProps_.setJoin();
  }

  void onOutLanguage (const DagInit* d) {
    checkNumberOfArguments(d, 1);
    toolProps_.OutLanguage = InitPtrToString(d->getArg(0));
  }

  void onOutputSuffix (const DagInit* d) {
    checkNumberOfArguments(d, 1);
    toolProps_.OutputSuffix = InitPtrToString(d->getArg(0));
  }

  void onSink (const DagInit* d) {
    checkNumberOfArguments(d, 0);
    optDescs_.HasSink = true;
    toolProps_.setSink();
  }

  // Just forwards to the AddOption function object. Somewhat
  // non-optimal, but avoids code duplication.
  void addOption (const DagInit* d) {
    checkNumberOfArguments(d, 2);
    AddOption(optDescs_, &toolProps_)(d);
  }

};

// Defintions of static members of CollectProperties.
CollectProperties::PropertyHandlerMap CollectProperties::propertyHandlers_;
bool CollectProperties::staticMembersInitialized_ = false;


/// CollectToolProperties - Gather information about tool properties
/// from the parsed TableGen data (basically a wrapper for the
/// CollectProperties function object).
void CollectToolProperties (RecordVector::const_iterator B,
                            RecordVector::const_iterator E,
                            ToolPropertiesList& TPList,
                            GlobalOptionDescriptions& OptDescs)
{
  // Iterate over a properties list of every Tool definition
  for (;B!=E;++B) {
    Record* T = *B;
    // Throws an exception if the value does not exist.
    ListInit* PropList = T->getValueAsListInit("properties");

    IntrusiveRefCntPtr<ToolProperties>
      ToolProps(new ToolProperties(T->getName()));

    std::for_each(PropList->begin(), PropList->end(),
                  CollectProperties(*ToolProps, OptDescs));
    TPList.push_back(ToolProps);
  }
}


/// CollectPropertiesFromOptionList - Gather information about
/// *global* option properties from the OptionList.
void CollectPropertiesFromOptionList (RecordVector::const_iterator B,
                                      RecordVector::const_iterator E,
                                      GlobalOptionDescriptions& OptDescs)
{
  // Iterate over a properties list of every Tool definition
  for (;B!=E;++B) {
    RecordVector::value_type T = *B;
    // Throws an exception if the value does not exist.
    ListInit* PropList = T->getValueAsListInit("options");

    std::for_each(PropList->begin(), PropList->end(), AddOption(OptDescs));
  }
}

/// CheckForSuperfluousOptions - Check that there are no side
/// effect-free options (specified only in the OptionList). Otherwise,
/// output a warning.
void CheckForSuperfluousOptions (const ToolPropertiesList& TPList,
                                 const GlobalOptionDescriptions& OptDescs) {
  llvm::StringSet<> nonSuperfluousOptions;

  // Add all options mentioned in the TPList to the set of
  // non-superfluous options.
  for (ToolPropertiesList::const_iterator B = TPList.begin(),
         E = TPList.end(); B != E; ++B) {
    const ToolProperties& TP = *(*B);
    for (ToolOptionDescriptions::const_iterator B = TP.OptDescs.begin(),
           E = TP.OptDescs.end(); B != E; ++B) {
      nonSuperfluousOptions.insert(B->first());
    }
  }

  // Check that all options in OptDescs belong to the set of
  // non-superfluous options.
  for (GlobalOptionDescriptions::const_iterator B = OptDescs.begin(),
         E = OptDescs.end(); B != E; ++B) {
    const GlobalOptionDescription& Val = B->second;
    if (!nonSuperfluousOptions.count(Val.Name)
        && Val.Type != OptionType::Alias)
      cerr << "Warning: option '-" << Val.Name << "' has no effect! "
        "Probable cause: this option is specified only in the OptionList.\n";
  }
}

/// EmitCaseTest1Arg - Helper function used by
/// EmitCaseConstructHandler.
bool EmitCaseTest1Arg(const std::string& TestName,
                      const DagInit& d,
                      const GlobalOptionDescriptions& OptDescs,
                      std::ostream& O) {
  checkNumberOfArguments(&d, 1);
  const std::string& OptName = InitPtrToString(d.getArg(0));
  if (TestName == "switch_on") {
    const GlobalOptionDescription& OptDesc = OptDescs.FindOption(OptName);
    if (OptDesc.Type != OptionType::Switch)
      throw OptName + ": incorrect option type!";
    O << OptDesc.GenVariableName();
    return true;
  } else if (TestName == "input_languages_contain") {
    O << "InLangs.count(\"" << OptName << "\") != 0";
    return true;
  } else if (TestName == "in_language") {
    // This works only for single-argument Tool::GenerateAction. Join
    // tools can process several files in different languages simultaneously.

    // TODO: make this work with Edge::Weight (if possible).
    O << "LangMap.GetLanguage(inFile) == \"" << OptName << '\"';
    return true;
  } else if (TestName == "not_empty") {
    if (OptName == "o") {
      O << "!OutputFilename.empty()";
      return true;
    }
    else {
      const GlobalOptionDescription& OptDesc = OptDescs.FindOption(OptName);
      if (OptDesc.Type == OptionType::Switch)
        throw OptName + ": incorrect option type!";
      O << '!' << OptDesc.GenVariableName() << ".empty()";
      return true;
    }
  }

  return false;
}

/// EmitCaseTest2Args - Helper function used by
/// EmitCaseConstructHandler.
bool EmitCaseTest2Args(const std::string& TestName,
                       const DagInit& d,
                       const char* IndentLevel,
                       const GlobalOptionDescriptions& OptDescs,
                       std::ostream& O) {
  checkNumberOfArguments(&d, 2);
  const std::string& OptName = InitPtrToString(d.getArg(0));
  const std::string& OptArg = InitPtrToString(d.getArg(1));
  const GlobalOptionDescription& OptDesc = OptDescs.FindOption(OptName);

  if (TestName == "parameter_equals") {
    if (OptDesc.Type != OptionType::Parameter
        && OptDesc.Type != OptionType::Prefix)
      throw OptName + ": incorrect option type!";
    O << OptDesc.GenVariableName() << " == \"" << OptArg << "\"";
    return true;
  }
  else if (TestName == "element_in_list") {
    if (OptDesc.Type != OptionType::ParameterList
        && OptDesc.Type != OptionType::PrefixList)
      throw OptName + ": incorrect option type!";
    const std::string& VarName = OptDesc.GenVariableName();
    O << "std::find(" << VarName << ".begin(),\n"
      << IndentLevel << Indent1 << VarName << ".end(), \""
      << OptArg << "\") != " << VarName << ".end()";
    return true;
  }

  return false;
}

// Forward declaration.
// EmitLogicalOperationTest and EmitCaseTest are mutually recursive.
void EmitCaseTest(const DagInit& d, const char* IndentLevel,
                  const GlobalOptionDescriptions& OptDescs,
                  std::ostream& O);

/// EmitLogicalOperationTest - Helper function used by
/// EmitCaseConstructHandler.
void EmitLogicalOperationTest(const DagInit& d, const char* LogicOp,
                              const char* IndentLevel,
                              const GlobalOptionDescriptions& OptDescs,
                              std::ostream& O) {
  O << '(';
  for (unsigned j = 0, NumArgs = d.getNumArgs(); j < NumArgs; ++j) {
    const DagInit& InnerTest = InitPtrToDag(d.getArg(j));
    EmitCaseTest(InnerTest, IndentLevel, OptDescs, O);
    if (j != NumArgs - 1)
      O << ")\n" << IndentLevel << Indent1 << ' ' << LogicOp << " (";
    else
      O << ')';
  }
}

/// EmitCaseTest - Helper function used by EmitCaseConstructHandler.
void EmitCaseTest(const DagInit& d, const char* IndentLevel,
                  const GlobalOptionDescriptions& OptDescs,
                  std::ostream& O) {
  const std::string& TestName = d.getOperator()->getAsString();

  if (TestName == "and")
    EmitLogicalOperationTest(d, "&&", IndentLevel, OptDescs, O);
  else if (TestName == "or")
    EmitLogicalOperationTest(d, "||", IndentLevel, OptDescs, O);
  else if (EmitCaseTest1Arg(TestName, d, OptDescs, O))
    return;
  else if (EmitCaseTest2Args(TestName, d, IndentLevel, OptDescs, O))
    return;
  else
    throw TestName + ": unknown edge property!";
}

// Emit code that handles the 'case' construct.
// Takes a function object that should emit code for every case clause.
// Callback's type is
// void F(Init* Statement, const char* IndentLevel, std::ostream& O).
template <typename F>
void EmitCaseConstructHandler(const DagInit* d, const char* IndentLevel,
                              F Callback, bool EmitElseIf,
                              const GlobalOptionDescriptions& OptDescs,
                              std::ostream& O) {
  assert(d->getOperator()->getAsString() == "case");

  unsigned numArgs = d->getNumArgs();
  if (d->getNumArgs() < 2)
    throw "There should be at least one clause in the 'case' expression:\n"
      + d->getAsString();

  for (unsigned i = 0; i != numArgs; ++i) {
    const DagInit& Test = InitPtrToDag(d->getArg(i));

    // Emit the test.
    if (Test.getOperator()->getAsString() == "default") {
      if (i+2 != numArgs)
        throw std::string("The 'default' clause should be the last in the"
                          "'case' construct!");
      O << IndentLevel << "else {\n";
    }
    else {
      O << IndentLevel << ((i != 0 && EmitElseIf) ? "else if (" : "if (");
      EmitCaseTest(Test, IndentLevel, OptDescs, O);
      O << ") {\n";
    }

    // Emit the corresponding statement.
    ++i;
    if (i == numArgs)
      throw "Case construct handler: no corresponding action "
        "found for the test " + Test.getAsString() + '!';

    Init* arg = d->getArg(i);
    if (dynamic_cast<DagInit*>(arg)
        && static_cast<DagInit*>(arg)->getOperator()->getAsString() == "case") {
      EmitCaseConstructHandler(static_cast<DagInit*>(arg),
                               (std::string(IndentLevel) + Indent1).c_str(),
                               Callback, EmitElseIf, OptDescs, O);
    }
    else {
      Callback(arg, IndentLevel, O);
    }
    O << IndentLevel << "}\n";
  }
}

/// EmitForwardOptionPropertyHandlingCode - Helper function used to
/// implement EmitOptionPropertyHandlingCode(). Emits code for
/// handling the (forward) and (forward_as) option properties.
void EmitForwardOptionPropertyHandlingCode (const ToolOptionDescription& D,
                                            const std::string& NewName,
                                            std::ostream& O) {
  const std::string& Name = NewName.empty()
    ? ("-" + D.Name)
    : NewName;

  switch (D.Type) {
  case OptionType::Switch:
    O << Indent3 << "vec.push_back(\"" << Name << "\");\n";
    break;
  case OptionType::Parameter:
    O << Indent3 << "vec.push_back(\"" << Name << "\");\n";
    O << Indent3 << "vec.push_back(" << D.GenVariableName() << ");\n";
    break;
  case OptionType::Prefix:
    O << Indent3 << "vec.push_back(\"" << Name << "\" + "
      << D.GenVariableName() << ");\n";
    break;
  case OptionType::PrefixList:
    O << Indent3 << "for (" << D.GenTypeDeclaration()
      << "::iterator B = " << D.GenVariableName() << ".begin(),\n"
      << Indent3 << "E = " << D.GenVariableName() << ".end(); B != E; ++B)\n"
      << Indent4 << "vec.push_back(\"" << Name << "\" + "
      << "*B);\n";
    break;
  case OptionType::ParameterList:
    O << Indent3 << "for (" << D.GenTypeDeclaration()
      << "::iterator B = " << D.GenVariableName() << ".begin(),\n"
      << Indent3 << "E = " << D.GenVariableName()
      << ".end() ; B != E; ++B) {\n"
      << Indent4 << "vec.push_back(\"" << Name << "\");\n"
      << Indent4 << "vec.push_back(*B);\n"
      << Indent3 << "}\n";
    break;
  case OptionType::Alias:
  default:
    throw std::string("Aliases are not allowed in tool option descriptions!");
  }
}

// ToolOptionHasInterestingProperties - A helper function used by
// EmitOptionPropertyHandlingCode() that tells us whether we should
// emit any property handling code at all.
bool ToolOptionHasInterestingProperties(const ToolOptionDescription& D) {
  bool ret = false;
  for (OptionPropertyList::const_iterator B = D.Props.begin(),
         E = D.Props.end(); B != E; ++B) {
      const OptionProperty& OptProp = *B;
      if (OptProp.first == OptionPropertyType::AppendCmd
          || OptProp.first == OptionPropertyType::ForwardAs)
        ret = true;
    }
  if (D.isForward() || D.isUnpackValues())
    ret = true;
  return ret;
}

/// EmitOptionPropertyHandlingCode - Helper function used by
/// EmitGenerateActionMethod(). Emits code that handles option
/// properties.
void EmitOptionPropertyHandlingCode (const ToolOptionDescription& D,
                                     std::ostream& O)
{
  if (!ToolOptionHasInterestingProperties(D))
    return;
  // Start of the if-clause.
  O << Indent2 << "if (";
  if (D.Type == OptionType::Switch)
    O << D.GenVariableName();
  else
    O << '!' << D.GenVariableName() << ".empty()";

  O <<") {\n";

  // Handle option properties that take an argument.
  for (OptionPropertyList::const_iterator B = D.Props.begin(),
        E = D.Props.end(); B!=E; ++B) {
    const OptionProperty& val = *B;

    switch (val.first) {
      // (append_cmd cmd) property
    case OptionPropertyType::AppendCmd:
      O << Indent3 << "vec.push_back(\"" << val.second << "\");\n";
      break;
      // (forward_as) property
    case OptionPropertyType::ForwardAs:
      EmitForwardOptionPropertyHandlingCode(D, val.second, O);
      break;
      // Other properties with argument
    default:
      break;
    }
  }

  // Handle flags

  // (forward) property
  if (D.isForward())
    EmitForwardOptionPropertyHandlingCode(D, "", O);

  // (unpack_values) property
  if (D.isUnpackValues()) {
    if (IsListOptionType(D.Type)) {
      O << Indent3 << "for (" << D.GenTypeDeclaration()
        << "::iterator B = " << D.GenVariableName() << ".begin(),\n"
        << Indent3 << "E = " << D.GenVariableName()
        << ".end(); B != E; ++B)\n"
        << Indent4 << "llvm::SplitString(*B, vec, \",\");\n";
    }
    else if (D.Type == OptionType::Prefix || D.Type == OptionType::Parameter){
      O << Indent3 << "llvm::SplitString("
        << D.GenVariableName() << ", vec, \",\");\n";
    }
    else {
      throw std::string("Switches can't have unpack_values property!");
    }
  }

  // End of the if-clause.
  O << Indent2 << "}\n";
}

/// SubstituteSpecialCommands - Perform string substitution for $CALL
/// and $ENV. Helper function used by EmitCmdLineVecFill().
std::string SubstituteSpecialCommands(const std::string& cmd) {
  size_t cparen = cmd.find(")");
  std::string ret;

  if (cmd.find("$CALL(") == 0) {
    if (cmd.size() == 6)
      throw std::string("$CALL invocation: empty argument list!");

    ret += "hooks::";
    ret += std::string(cmd.begin() + 6, cmd.begin() + cparen);
    ret += "()";
  }
  else if (cmd.find("$ENV(") == 0) {
    if (cmd.size() == 5)
      throw std::string("$ENV invocation: empty argument list!");

    ret += "std::getenv(\"";
    ret += std::string(cmd.begin() + 5, cmd.begin() + cparen);
    ret += "\")";
  }
  else {
    throw "Unknown special command: " + cmd;
  }

  if (cmd.begin() + cparen + 1 != cmd.end()) {
    ret += " + std::string(\"";
    ret += (cmd.c_str() + cparen + 1);
    ret += "\")";
  }

  return ret;
}

/// EmitCmdLineVecFill - Emit code that fills in the command line
/// vector. Helper function used by EmitGenerateActionMethod().
void EmitCmdLineVecFill(const Init* CmdLine, const std::string& ToolName,
                        bool Version, const char* IndentLevel,
                        std::ostream& O) {
  StrVector StrVec;
  SplitString(InitPtrToString(CmdLine), StrVec);
  if (StrVec.empty())
    throw "Tool " + ToolName + " has empty command line!";

  StrVector::const_iterator I = StrVec.begin();
  ++I;
  for (StrVector::const_iterator E = StrVec.end(); I != E; ++I) {
    const std::string& cmd = *I;
    O << IndentLevel;
    if (cmd.at(0) == '$') {
      if (cmd == "$INFILE") {
        if (Version)
          O << "for (PathVector::const_iterator B = inFiles.begin()"
            << ", E = inFiles.end();\n"
            << IndentLevel << "B != E; ++B)\n"
            << IndentLevel << Indent1 << "vec.push_back(B->toString());\n";
        else
          O << "vec.push_back(inFile.toString());\n";
      }
      else if (cmd == "$OUTFILE") {
        O << "vec.push_back(outFile.toString());\n";
      }
      else {
        O << "vec.push_back(" << SubstituteSpecialCommands(cmd);
        O << ");\n";
      }
    }
    else {
      O << "vec.push_back(\"" << cmd << "\");\n";
    }
  }
  O << IndentLevel << "cmd = "
    << ((StrVec[0][0] == '$') ? SubstituteSpecialCommands(StrVec[0])
        : "\"" + StrVec[0] + "\"")
    << ";\n";
}

/// EmitCmdLineVecFillCallback - A function object wrapper around
/// EmitCmdLineVecFill(). Used by EmitGenerateActionMethod() as an
/// argument to EmitCaseConstructHandler().
class EmitCmdLineVecFillCallback {
  bool Version;
  const std::string& ToolName;
 public:
  EmitCmdLineVecFillCallback(bool Ver, const std::string& TN)
    : Version(Ver), ToolName(TN) {}

  void operator()(const Init* Statement, const char* IndentLevel,
                  std::ostream& O) const
  {
    EmitCmdLineVecFill(Statement, ToolName, Version,
                       (std::string(IndentLevel) + Indent1).c_str(), O);
  }
};

// EmitGenerateActionMethod - Emit one of two versions of the
// Tool::GenerateAction() method.
void EmitGenerateActionMethod (const ToolProperties& P,
                               const GlobalOptionDescriptions& OptDescs,
                               bool Version, std::ostream& O) {
  if (Version)
    O << Indent1 << "Action GenerateAction(const PathVector& inFiles,\n";
  else
    O << Indent1 << "Action GenerateAction(const sys::Path& inFile,\n";

  O << Indent2 << "const sys::Path& outFile,\n"
    << Indent2 << "const InputLanguagesSet& InLangs,\n"
    << Indent2 << "const LanguageMap& LangMap) const\n"
    << Indent1 << "{\n"
    << Indent2 << "const char* cmd;\n"
    << Indent2 << "std::vector<std::string> vec;\n";

  // cmd_line is either a string or a 'case' construct.
  if (typeid(*P.CmdLine) == typeid(StringInit))
    EmitCmdLineVecFill(P.CmdLine, P.Name, Version, Indent2, O);
  else
    EmitCaseConstructHandler(&InitPtrToDag(P.CmdLine), Indent2,
                             EmitCmdLineVecFillCallback(Version, P.Name),
                             true, OptDescs, O);

  // For every understood option, emit handling code.
  for (ToolOptionDescriptions::const_iterator B = P.OptDescs.begin(),
        E = P.OptDescs.end(); B != E; ++B) {
    const ToolOptionDescription& val = B->second;
    EmitOptionPropertyHandlingCode(val, O);
  }

  // Handle the Sink property.
  if (P.isSink()) {
    O << Indent2 << "if (!" << SinkOptionName << ".empty()) {\n"
      << Indent3 << "vec.insert(vec.end(), "
      << SinkOptionName << ".begin(), " << SinkOptionName << ".end());\n"
      << Indent2 << "}\n";
  }

  O << Indent2 << "return Action(cmd, vec);\n"
    << Indent1 << "}\n\n";
}

/// EmitGenerateActionMethods - Emit two GenerateAction() methods for
/// a given Tool class.
void EmitGenerateActionMethods (const ToolProperties& P,
                                const GlobalOptionDescriptions& OptDescs,
                                std::ostream& O) {
  if (!P.isJoin())
    O << Indent1 << "Action GenerateAction(const PathVector& inFiles,\n"
      << Indent2 << "const llvm::sys::Path& outFile,\n"
      << Indent2 << "const InputLanguagesSet& InLangs,\n"
      << Indent2 << "const LanguageMap& LangMap) const\n"
      << Indent1 << "{\n"
      << Indent2 << "throw std::runtime_error(\"" << P.Name
      << " is not a Join tool!\");\n"
      << Indent1 << "}\n\n";
  else
    EmitGenerateActionMethod(P, OptDescs, true, O);

  EmitGenerateActionMethod(P, OptDescs, false, O);
}

/// EmitIsLastMethod - Emit the IsLast() method for a given Tool
/// class.
void EmitIsLastMethod (const ToolProperties& P, std::ostream& O) {
  O << Indent1 << "bool IsLast() const {\n"
    << Indent2 << "bool last = false;\n";

  for (ToolOptionDescriptions::const_iterator B = P.OptDescs.begin(),
        E = P.OptDescs.end(); B != E; ++B) {
    const ToolOptionDescription& val = B->second;

    if (val.isStopCompilation())
      O << Indent2
        << "if (" << val.GenVariableName()
        << ")\n" << Indent3 << "last = true;\n";
  }

  O << Indent2 << "return last;\n"
    << Indent1 <<  "}\n\n";
}

/// EmitInOutLanguageMethods - Emit the [Input,Output]Language()
/// methods for a given Tool class.
void EmitInOutLanguageMethods (const ToolProperties& P, std::ostream& O) {
  O << Indent1 << "const char** InputLanguages() const {\n"
    << Indent2 << "return InputLanguages_;\n"
    << Indent1 << "}\n\n";

  O << Indent1 << "const char* OutputLanguage() const {\n"
    << Indent2 << "return \"" << P.OutLanguage << "\";\n"
    << Indent1 << "}\n\n";
}

/// EmitOutputSuffixMethod - Emit the OutputSuffix() method for a
/// given Tool class.
void EmitOutputSuffixMethod (const ToolProperties& P, std::ostream& O) {
  O << Indent1 << "const char* OutputSuffix() const {\n"
    << Indent2 << "const char* ret = \"" << P.OutputSuffix << "\";\n";

  for (ToolOptionDescriptions::const_iterator B = P.OptDescs.begin(),
         E = P.OptDescs.end(); B != E; ++B) {
    const ToolOptionDescription& OptDesc = B->second;
    for (OptionPropertyList::const_iterator B = OptDesc.Props.begin(),
           E = OptDesc.Props.end(); B != E; ++B) {
      const OptionProperty& OptProp = *B;
      if (OptProp.first == OptionPropertyType::OutputSuffix) {
        O << Indent2 << "if (" << OptDesc.GenVariableName() << ")\n"
          << Indent3 << "ret = \"" << OptProp.second << "\";\n";
      }
    }
  }

  O << Indent2 << "return ret;\n"
    << Indent1 << "}\n\n";
}

/// EmitNameMethod - Emit the Name() method for a given Tool class.
void EmitNameMethod (const ToolProperties& P, std::ostream& O) {
  O << Indent1 << "const char* Name() const {\n"
    << Indent2 << "return \"" << P.Name << "\";\n"
    << Indent1 << "}\n\n";
}

/// EmitIsJoinMethod - Emit the IsJoin() method for a given Tool
/// class.
void EmitIsJoinMethod (const ToolProperties& P, std::ostream& O) {
  O << Indent1 << "bool IsJoin() const {\n";
  if (P.isJoin())
    O << Indent2 << "return true;\n";
  else
    O << Indent2 << "return false;\n";
  O << Indent1 << "}\n\n";
}

/// EmitStaticMemberDefinitions - Emit static member definitions for a
/// given Tool class.
void EmitStaticMemberDefinitions(const ToolProperties& P, std::ostream& O) {
  O << "const char* " << P.Name << "::InputLanguages_[] = {";
  for (StrVector::const_iterator B = P.InLanguage.begin(),
         E = P.InLanguage.end(); B != E; ++B)
    O << '\"' << *B << "\", ";
  O << "0};\n\n";
}

/// EmitToolClassDefinition - Emit a Tool class definition.
void EmitToolClassDefinition (const ToolProperties& P,
                              const GlobalOptionDescriptions& OptDescs,
                              std::ostream& O) {
  if (P.Name == "root")
    return;

  // Header
  O << "class " << P.Name << " : public ";
  if (P.isJoin())
    O << "JoinTool";
  else
    O << "Tool";

  O << "{\nprivate:\n"
    << Indent1 << "static const char* InputLanguages_[];\n\n";

  O << "public:\n";
  EmitNameMethod(P, O);
  EmitInOutLanguageMethods(P, O);
  EmitOutputSuffixMethod(P, O);
  EmitIsJoinMethod(P, O);
  EmitGenerateActionMethods(P, OptDescs, O);
  EmitIsLastMethod(P, O);

  // Close class definition
  O << "};\n";

  EmitStaticMemberDefinitions(P, O);

}

/// EmitOptionDescriptions - Iterate over a list of option
/// descriptions and emit registration code.
void EmitOptionDescriptions (const GlobalOptionDescriptions& descs,
                             std::ostream& O)
{
  std::vector<GlobalOptionDescription> Aliases;

  // Emit static cl::Option variables.
  for (GlobalOptionDescriptions::const_iterator B = descs.begin(),
         E = descs.end(); B!=E; ++B) {
    const GlobalOptionDescription& val = B->second;

    if (val.Type == OptionType::Alias) {
      Aliases.push_back(val);
      continue;
    }

    O << val.GenTypeDeclaration() << ' '
      << val.GenVariableName()
      << "(\"" << val.Name << '\"';

    if (val.Type == OptionType::Prefix || val.Type == OptionType::PrefixList)
      O << ", cl::Prefix";

    if (val.isRequired()) {
      switch (val.Type) {
      case OptionType::PrefixList:
      case OptionType::ParameterList:
        O << ", cl::OneOrMore";
        break;
      default:
        O << ", cl::Required";
      }
    }

    if (!val.Help.empty())
      O << ", cl::desc(\"" << val.Help << "\")";

    O << ");\n";
  }

  // Emit the aliases (they should go after all the 'proper' options).
  for (std::vector<GlobalOptionDescription>::const_iterator
         B = Aliases.begin(), E = Aliases.end(); B != E; ++B) {
    const GlobalOptionDescription& val = *B;

    O << val.GenTypeDeclaration() << ' '
      << val.GenVariableName()
      << "(\"" << val.Name << '\"';

    GlobalOptionDescriptions::container_type
      ::const_iterator F = descs.Descriptions.find(val.Help);
    if (F != descs.Descriptions.end())
      O << ", cl::aliasopt(" << F->second.GenVariableName() << ")";
    else
      throw val.Name + ": alias to an unknown option!";

    O << ", cl::desc(\"" << "An alias for -" + val.Help  << "\"));\n";
  }

  // Emit the sink option.
  if (descs.HasSink)
    O << "cl::list<std::string> " << SinkOptionName << "(cl::Sink);\n";

  O << '\n';
}

/// EmitPopulateLanguageMap - Emit the PopulateLanguageMap() function.
void EmitPopulateLanguageMap (const RecordKeeper& Records, std::ostream& O)
{
  // Get the relevant field out of RecordKeeper
  Record* LangMapRecord = Records.getDef("LanguageMap");
  if (!LangMapRecord)
    throw std::string("Language map definition not found!");

  ListInit* LangsToSuffixesList = LangMapRecord->getValueAsListInit("map");
  if (!LangsToSuffixesList)
    throw std::string("Error in the language map definition!");

  // Generate code
  O << "namespace {\n\n";
  O << "void PopulateLanguageMapLocal(LanguageMap& langMap) {\n";

  for (unsigned i = 0; i < LangsToSuffixesList->size(); ++i) {
    Record* LangToSuffixes = LangsToSuffixesList->getElementAsRecord(i);

    const std::string& Lang = LangToSuffixes->getValueAsString("lang");
    const ListInit* Suffixes = LangToSuffixes->getValueAsListInit("suffixes");

    for (unsigned i = 0; i < Suffixes->size(); ++i)
      O << Indent1 << "langMap[\""
        << InitPtrToString(Suffixes->getElement(i))
        << "\"] = \"" << Lang << "\";\n";
  }

  O << "}\n\n}\n\n";
}

/// FillInToolToLang - Fills in two tables that map tool names to
/// (input, output) languages.  Used by the typechecker.
void FillInToolToLang (const ToolPropertiesList& TPList,
                       StringMap<StringSet<> >& ToolToInLang,
                       StringMap<std::string>& ToolToOutLang) {
  for (ToolPropertiesList::const_iterator B = TPList.begin(), E = TPList.end();
       B != E; ++B) {
    const ToolProperties& P = *(*B);
    for (StrVector::const_iterator B = P.InLanguage.begin(),
           E = P.InLanguage.end(); B != E; ++B)
      ToolToInLang[P.Name].insert(*B);
    ToolToOutLang[P.Name] = P.OutLanguage;
  }
}

/// TypecheckGraph - Check that names for output and input languages
/// on all edges do match.
// TOFIX: It would be nice if this function also checked for cycles
// and multiple default edges in the graph (better error
// reporting). Unfortunately, it is awkward to do right now because
// our intermediate representation is not sufficiently
// sophisticated. Algorithms like these require a real graph instead of
// an AST.
void TypecheckGraph (Record* CompilationGraph,
                     const ToolPropertiesList& TPList) {
  StringMap<StringSet<> > ToolToInLang;
  StringMap<std::string> ToolToOutLang;

  FillInToolToLang(TPList, ToolToInLang, ToolToOutLang);
  ListInit* edges = CompilationGraph->getValueAsListInit("edges");
  StringMap<std::string>::iterator IAE = ToolToOutLang.end();
  StringMap<StringSet<> >::iterator IBE = ToolToInLang.end();

  for (unsigned i = 0; i < edges->size(); ++i) {
    Record* Edge = edges->getElementAsRecord(i);
    Record* A = Edge->getValueAsDef("a");
    Record* B = Edge->getValueAsDef("b");
    StringMap<std::string>::iterator IA = ToolToOutLang.find(A->getName());
    StringMap<StringSet<> >::iterator IB = ToolToInLang.find(B->getName());
    if (IA == IAE)
      throw A->getName() + ": no such tool!";
    if (IB == IBE)
      throw B->getName() + ": no such tool!";
    if (A->getName() != "root" && IB->second.count(IA->second) == 0)
      throw "Edge " + A->getName() + "->" + B->getName()
        + ": output->input language mismatch";
    if (B->getName() == "root")
      throw std::string("Edges back to the root are not allowed!");
  }
}

/// IncDecWeight - Helper function passed to EmitCaseConstructHandler()
/// by EmitEdgeClass().
void IncDecWeight (const Init* i, const char* IndentLevel,
                   std::ostream& O) {
  const DagInit& d = InitPtrToDag(i);
  const std::string& OpName = d.getOperator()->getAsString();

  if (OpName == "inc_weight")
    O << IndentLevel << Indent1 << "ret += ";
  else if (OpName == "dec_weight")
    O << IndentLevel << Indent1 << "ret -= ";
  else
    throw "Unknown operator in edge properties list: " + OpName + '!';

  if (d.getNumArgs() > 0)
    O << InitPtrToInt(d.getArg(0)) << ";\n";
  else
    O << "2;\n";

}

/// EmitEdgeClass - Emit a single Edge# class.
void EmitEdgeClass (unsigned N, const std::string& Target,
                    DagInit* Case, const GlobalOptionDescriptions& OptDescs,
                    std::ostream& O) {

  // Class constructor.
  O << "class Edge" << N << ": public Edge {\n"
    << "public:\n"
    << Indent1 << "Edge" << N << "() : Edge(\"" << Target
    << "\") {}\n\n"

  // Function Weight().
    << Indent1 << "unsigned Weight(const InputLanguagesSet& InLangs) const {\n"
    << Indent2 << "unsigned ret = 0;\n";

  // Handle the 'case' construct.
  EmitCaseConstructHandler(Case, Indent2, IncDecWeight, false, OptDescs, O);

  O << Indent2 << "return ret;\n"
    << Indent1 << "};\n\n};\n\n";
}

/// EmitEdgeClasses - Emit Edge* classes that represent graph edges.
void EmitEdgeClasses (Record* CompilationGraph,
                      const GlobalOptionDescriptions& OptDescs,
                      std::ostream& O) {
  ListInit* edges = CompilationGraph->getValueAsListInit("edges");

  for (unsigned i = 0; i < edges->size(); ++i) {
    Record* Edge = edges->getElementAsRecord(i);
    Record* B = Edge->getValueAsDef("b");
    DagInit* Weight = Edge->getValueAsDag("weight");

    if (isDagEmpty(Weight))
      continue;

    EmitEdgeClass(i, B->getName(), Weight, OptDescs, O);
  }
}

/// EmitPopulateCompilationGraph - Emit the PopulateCompilationGraph()
/// function.
void EmitPopulateCompilationGraph (Record* CompilationGraph,
                                   std::ostream& O)
{
  ListInit* edges = CompilationGraph->getValueAsListInit("edges");

  // Generate code
  O << "namespace {\n\n";
  O << "void PopulateCompilationGraphLocal(CompilationGraph& G) {\n";

  // Insert vertices

  RecordVector Tools = Records.getAllDerivedDefinitions("Tool");
  if (Tools.empty())
    throw std::string("No tool definitions found!");

  for (RecordVector::iterator B = Tools.begin(), E = Tools.end(); B != E; ++B) {
    const std::string& Name = (*B)->getName();
    if (Name != "root")
      O << Indent1 << "G.insertNode(new "
        << Name << "());\n";
  }

  O << '\n';

  // Insert edges
  for (unsigned i = 0; i < edges->size(); ++i) {
    Record* Edge = edges->getElementAsRecord(i);
    Record* A = Edge->getValueAsDef("a");
    Record* B = Edge->getValueAsDef("b");
    DagInit* Weight = Edge->getValueAsDag("weight");

    O << Indent1 << "G.insertEdge(\"" << A->getName() << "\", ";

    if (isDagEmpty(Weight))
      O << "new SimpleEdge(\"" << B->getName() << "\")";
    else
      O << "new Edge" << i << "()";

    O << ");\n";
  }

  O << "}\n\n}\n\n";
}

/// ExtractHookNames - Extract the hook names from all instances of
/// $CALL(HookName) in the provided command line string. Helper
/// function used by FillInHookNames().
void ExtractHookNames(const Init* CmdLine, StrVector& HookNames) {
  StrVector cmds;
  llvm::SplitString(InitPtrToString(CmdLine), cmds);
  for (StrVector::const_iterator B = cmds.begin(), E = cmds.end();
       B != E; ++B) {
    const std::string& cmd = *B;
    if (cmd.find("$CALL(") == 0) {
      if (cmd.size() == 6)
        throw std::string("$CALL invocation: empty argument list!");
      HookNames.push_back(std::string(cmd.begin() + 6,
                                      cmd.begin() + cmd.find(")")));
    }
  }
}

/// ExtractHookNamesFromCaseConstruct - Extract hook names from the
/// 'case' expression, handle nesting. Helper function used by
/// FillInHookNames().
void ExtractHookNamesFromCaseConstruct(Init* Case, StrVector& HookNames) {
  const DagInit& d = InitPtrToDag(Case);
  bool even = false;
  for (DagInit::const_arg_iterator B = d.arg_begin(), E = d.arg_end();
       B != E; ++B) {
    Init* arg = *B;
    if (even && dynamic_cast<DagInit*>(arg)
        && static_cast<DagInit*>(arg)->getOperator()->getAsString() == "case")
      ExtractHookNamesFromCaseConstruct(arg, HookNames);
    else if (even)
      ExtractHookNames(arg, HookNames);
    even = !even;
  }
}

/// FillInHookNames - Actually extract the hook names from all command
/// line strings. Helper function used by EmitHookDeclarations().
void FillInHookNames(const ToolPropertiesList& TPList,
                     StrVector& HookNames) {
  // For all command lines:
  for (ToolPropertiesList::const_iterator B = TPList.begin(),
         E = TPList.end(); B != E; ++B) {
    const ToolProperties& P = *(*B);
    if (!P.CmdLine)
      continue;
    if (dynamic_cast<StringInit*>(P.CmdLine))
      // This is a string.
      ExtractHookNames(P.CmdLine, HookNames);
    else
      // This is a 'case' construct.
      ExtractHookNamesFromCaseConstruct(P.CmdLine, HookNames);
  }
}

/// EmitHookDeclarations - Parse CmdLine fields of all the tool
/// property records and emit hook function declaration for each
/// instance of $CALL(HookName).
void EmitHookDeclarations(const ToolPropertiesList& ToolProps,
                          std::ostream& O) {
  StrVector HookNames;
  FillInHookNames(ToolProps, HookNames);
  if (HookNames.empty())
    return;
  std::sort(HookNames.begin(), HookNames.end());
  StrVector::const_iterator E = std::unique(HookNames.begin(), HookNames.end());

  O << "namespace hooks {\n";
  for (StrVector::const_iterator B = HookNames.begin(); B != E; ++B)
    O << Indent1 << "std::string " << *B << "();\n";

  O << "}\n\n";
}

/// EmitRegisterPlugin - Emit code to register this plugin.
void EmitRegisterPlugin(std::ostream& O) {
  O << "namespace {\n\n"
    << "struct Plugin : public llvmc::BasePlugin {\n"
    << Indent1 << "void PopulateLanguageMap(LanguageMap& langMap) const\n"
    << Indent1 << "{ PopulateLanguageMapLocal(langMap); }\n\n"
    << Indent1
    << "void PopulateCompilationGraph(CompilationGraph& graph) const\n"
    << Indent1 << "{ PopulateCompilationGraphLocal(graph); }\n"
    << "};\n\n"

    << "static llvmc::RegisterPlugin<Plugin> RP;\n\n}\n\n";
}

/// EmitInclude - Emit necessary #include directives.
void EmitIncludes(std::ostream& O) {
  O << "#include \"llvm/CompilerDriver/CompilationGraph.h\"\n"
    << "#include \"llvm/CompilerDriver/Plugin.h\"\n"
    << "#include \"llvm/CompilerDriver/Tool.h\"\n\n"

    << "#include \"llvm/ADT/StringExtras.h\"\n"
    << "#include \"llvm/Support/CommandLine.h\"\n\n"

    << "#include <cstdlib>\n"
    << "#include <stdexcept>\n\n"

    << "using namespace llvm;\n"
    << "using namespace llvmc;\n\n"

    << "extern cl::opt<std::string> OutputFilename;\n\n";
}

// End of anonymous namespace
}

/// run - The back-end entry point.
void LLVMCConfigurationEmitter::run (std::ostream &O) {
  try {

  // Emit file header.
  EmitSourceFileHeader("LLVMC Configuration Library", O);
  EmitIncludes(O);

  // Get a list of all defined Tools.
  RecordVector Tools = Records.getAllDerivedDefinitions("Tool");
  if (Tools.empty())
    throw std::string("No tool definitions found!");

  // Gather information from the Tool description dags.
  ToolPropertiesList tool_props;
  GlobalOptionDescriptions opt_descs;
  CollectToolProperties(Tools.begin(), Tools.end(), tool_props, opt_descs);

  RecordVector OptionLists = Records.getAllDerivedDefinitions("OptionList");
  CollectPropertiesFromOptionList(OptionLists.begin(), OptionLists.end(),
                                  opt_descs);

  // Check that there are no options without side effects (specified
  // only in the OptionList).
  CheckForSuperfluousOptions(tool_props, opt_descs);

  // Emit global option registration code.
  EmitOptionDescriptions(opt_descs, O);

  // Emit hook declarations.
  EmitHookDeclarations(tool_props, O);

  // Emit PopulateLanguageMap() function
  // (a language map maps from file extensions to language names).
  EmitPopulateLanguageMap(Records, O);

  // Emit Tool classes.
  for (ToolPropertiesList::const_iterator B = tool_props.begin(),
         E = tool_props.end(); B!=E; ++B)
    EmitToolClassDefinition(*(*B), opt_descs, O);

  Record* CompilationGraphRecord = Records.getDef("CompilationGraph");
  if (!CompilationGraphRecord)
    throw std::string("Compilation graph description not found!");

  // Typecheck the compilation graph.
  TypecheckGraph(CompilationGraphRecord, tool_props);

  // Emit Edge# classes.
  EmitEdgeClasses(CompilationGraphRecord, opt_descs, O);

  // Emit PopulateCompilationGraph() function.
  EmitPopulateCompilationGraph(CompilationGraphRecord, O);

  // Emit code for plugin registration.
  EmitRegisterPlugin(O);

  // EOF
  } catch (std::exception& Error) {
    throw Error.what() + std::string(" - usually this means a syntax error.");
  }
}