utils/TableGen/RegisterInfoEmitter.cpp

//===- RegisterInfoEmitter.cpp - Generate a Register File Desc. -*- 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 a description of a target
// register file for a code generator.  It uses instances of the Register,
// RegisterAliases, and RegisterClass classes to gather this information.
//
//===----------------------------------------------------------------------===//

#include "RegisterInfoEmitter.h"
#include "CodeGenTarget.h"
#include "CodeGenRegisters.h"
#include "Record.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Streams.h"
#include <set>
#include <algorithm>
using namespace llvm;

// runEnums - Print out enum values for all of the registers.
void RegisterInfoEmitter::runEnums(std::ostream &OS) {
  CodeGenTarget Target;
  const std::vector<CodeGenRegister> &Registers = Target.getRegisters();

  std::string Namespace = Registers[0].TheDef->getValueAsString("Namespace");

  EmitSourceFileHeader("Target Register Enum Values", OS);
  OS << "namespace llvm {\n\n";

  if (!Namespace.empty())
    OS << "namespace " << Namespace << " {\n";
  OS << "  enum {\n    NoRegister,\n";

  for (unsigned i = 0, e = Registers.size(); i != e; ++i)
    OS << "    " << Registers[i].getName() << ", \t// " << i+1 << "\n";
  OS << "    NUM_TARGET_REGS \t// " << Registers.size()+1 << "\n";
  OS << "  };\n";
  if (!Namespace.empty())
    OS << "}\n";
  OS << "} // End llvm namespace \n";
}

void RegisterInfoEmitter::runHeader(std::ostream &OS) {
  EmitSourceFileHeader("Register Information Header Fragment", OS);
  CodeGenTarget Target;
  const std::string &TargetName = Target.getName();
  std::string ClassName = TargetName + "GenRegisterInfo";

  OS << "#include \"llvm/Target/TargetRegisterInfo.h\"\n";
  OS << "#include <string>\n\n";

  OS << "namespace llvm {\n\n";

  OS << "struct " << ClassName << " : public TargetRegisterInfo {\n"
     << "  explicit " << ClassName
     << "(int CallFrameSetupOpcode = -1, int CallFrameDestroyOpcode = -1);\n"
     << "  virtual int getDwarfRegNumFull(unsigned RegNum, "
     << "unsigned Flavour) const;\n"
     << "  virtual int getDwarfRegNum(unsigned RegNum, bool isEH) const = 0;\n"
     << "  virtual bool needsStackRealignment(const MachineFunction &) const\n"
     << "     { return false; }\n"
     << "  unsigned getSubReg(unsigned RegNo, unsigned Index) const;\n"
     << "};\n\n";

  const std::vector<CodeGenRegisterClass> &RegisterClasses =
    Target.getRegisterClasses();

  if (!RegisterClasses.empty()) {
    OS << "namespace " << RegisterClasses[0].Namespace
       << " { // Register classes\n";

    OS << "  enum {\n";
    for (unsigned i = 0, e = RegisterClasses.size(); i != e; ++i) {
      if (i) OS << ",\n";
      OS << "    " << RegisterClasses[i].getName() << "RegClassID";
      OS << " = " << (i+1);
    }
    OS << "\n  };\n\n";

    for (unsigned i = 0, e = RegisterClasses.size(); i != e; ++i) {
      const std::string &Name = RegisterClasses[i].getName();

      // Output the register class definition.
      OS << "  struct " << Name << "Class : public TargetRegisterClass {\n"
         << "    " << Name << "Class();\n"
         << RegisterClasses[i].MethodProtos << "  };\n";

      // Output the extern for the instance.
      OS << "  extern " << Name << "Class\t" << Name << "RegClass;\n";
      // Output the extern for the pointer to the instance (should remove).
      OS << "  static TargetRegisterClass * const "<< Name <<"RegisterClass = &"
         << Name << "RegClass;\n";
    }
    OS << "} // end of namespace " << TargetName << "\n\n";
  }
  OS << "} // End llvm namespace \n";
}

bool isSubRegisterClass(const CodeGenRegisterClass &RC,
                        std::set<Record*> &RegSet) {
  for (unsigned i = 0, e = RC.Elements.size(); i != e; ++i) {
    Record *Reg = RC.Elements[i];
    if (!RegSet.count(Reg))
      return false;
  }
  return true;
}

static void addSuperReg(Record *R, Record *S,
                        std::map<Record*, std::set<Record*> > &SubRegs,
                        std::map<Record*, std::set<Record*> > &SuperRegs,
                        std::map<Record*, std::set<Record*> > &Aliases) {
  if (R == S) {
    cerr << "Error: recursive sub-register relationship between"
         << " register " << getQualifiedName(R)
         << " and its sub-registers?\n";
    abort();
  }
  if (!SuperRegs[R].insert(S).second)
    return;
  SubRegs[S].insert(R);
  Aliases[R].insert(S);
  Aliases[S].insert(R);
  if (SuperRegs.count(S))
    for (std::set<Record*>::iterator I = SuperRegs[S].begin(),
           E = SuperRegs[S].end(); I != E; ++I)
      addSuperReg(R, *I, SubRegs, SuperRegs, Aliases);
}

static void addSubSuperReg(Record *R, Record *S,
                           std::map<Record*, std::set<Record*> > &SubRegs,
                           std::map<Record*, std::set<Record*> > &SuperRegs,
                           std::map<Record*, std::set<Record*> > &Aliases) {
  if (R == S) {
    cerr << "Error: recursive sub-register relationship between"
         << " register " << getQualifiedName(R)
         << " and its sub-registers?\n";
    abort();
  }

  if (!SubRegs[R].insert(S).second)
    return;
  addSuperReg(S, R, SubRegs, SuperRegs, Aliases);
  Aliases[R].insert(S);
  Aliases[S].insert(R);
  if (SubRegs.count(S))
    for (std::set<Record*>::iterator I = SubRegs[S].begin(),
           E = SubRegs[S].end(); I != E; ++I)
      addSubSuperReg(R, *I, SubRegs, SuperRegs, Aliases);
}

class RegisterSorter {
private:
  std::map<Record*, std::set<Record*> > &RegisterSubRegs;

public:
  RegisterSorter(std::map<Record*, std::set<Record*> > &RS)
    : RegisterSubRegs(RS) {};

  bool operator()(Record *RegA, Record *RegB) {
    // B is sub-register of A.
    return RegisterSubRegs.count(RegA) && RegisterSubRegs[RegA].count(RegB);
  }
};

// RegisterInfoEmitter::run - Main register file description emitter.
//
void RegisterInfoEmitter::run(std::ostream &OS) {
  CodeGenTarget Target;
  EmitSourceFileHeader("Register Information Source Fragment", OS);

  OS << "namespace llvm {\n\n";

  // Start out by emitting each of the register classes... to do this, we build
  // a set of registers which belong to a register class, this is to ensure that
  // each register is only in a single register class.
  //
  const std::vector<CodeGenRegisterClass> &RegisterClasses =
    Target.getRegisterClasses();

  // Loop over all of the register classes... emitting each one.
  OS << "namespace {     // Register classes...\n";

  // RegClassesBelongedTo - Keep track of which register classes each reg
  // belongs to.
  std::multimap<Record*, const CodeGenRegisterClass*> RegClassesBelongedTo;

  // Emit the register enum value arrays for each RegisterClass
  for (unsigned rc = 0, e = RegisterClasses.size(); rc != e; ++rc) {
    const CodeGenRegisterClass &RC = RegisterClasses[rc];

    // Give the register class a legal C name if it's anonymous.
    std::string Name = RC.TheDef->getName();

    // Emit the register list now.
    OS << "  // " << Name << " Register Class...\n"
       << "  static const unsigned " << Name
       << "[] = {\n    ";
    for (unsigned i = 0, e = RC.Elements.size(); i != e; ++i) {
      Record *Reg = RC.Elements[i];
      OS << getQualifiedName(Reg) << ", ";

      // Keep track of which regclasses this register is in.
      RegClassesBelongedTo.insert(std::make_pair(Reg, &RC));
    }
    OS << "\n  };\n\n";
  }

  // Emit the ValueType arrays for each RegisterClass
  for (unsigned rc = 0, e = RegisterClasses.size(); rc != e; ++rc) {
    const CodeGenRegisterClass &RC = RegisterClasses[rc];

    // Give the register class a legal C name if it's anonymous.
    std::string Name = RC.TheDef->getName() + "VTs";

    // Emit the register list now.
    OS << "  // " << Name
       << " Register Class Value Types...\n"
       << "  static const MVT " << Name
       << "[] = {\n    ";
    for (unsigned i = 0, e = RC.VTs.size(); i != e; ++i)
      OS << getEnumName(RC.VTs[i]) << ", ";
    OS << "MVT::Other\n  };\n\n";
  }
  OS << "}  // end anonymous namespace\n\n";

  // Now that all of the structs have been emitted, emit the instances.
  if (!RegisterClasses.empty()) {
    OS << "namespace " << RegisterClasses[0].Namespace
       << " {   // Register class instances\n";
    for (unsigned i = 0, e = RegisterClasses.size(); i != e; ++i)
      OS << "  " << RegisterClasses[i].getName()  << "Class\t"
         << RegisterClasses[i].getName() << "RegClass;\n";

    std::map<unsigned, std::set<unsigned> > SuperClassMap;
    std::map<unsigned, std::set<unsigned> > SuperRegClassMap;
    OS << "\n";

    // Emit the sub-register classes for each RegisterClass
    for (unsigned rc = 0, e = RegisterClasses.size(); rc != e; ++rc) {
      const CodeGenRegisterClass &RC = RegisterClasses[rc];

      // Give the register class a legal C name if it's anonymous.
      std::string Name = RC.TheDef->getName();

      OS << "  // " << Name
         << " Sub-register Classess...\n"
         << "  static const TargetRegisterClass* const "
         << Name << "SubRegClasses [] = {\n    ";

      bool Empty = true;

      for (unsigned subrc = 0, subrcMax = RC.SubRegClasses.size();
            subrc != subrcMax; ++subrc) {
        unsigned rc2 = 0, e2 = RegisterClasses.size();
        for (; rc2 != e2; ++rc2) {
          const CodeGenRegisterClass &RC2 =  RegisterClasses[rc2];
          if (RC.SubRegClasses[subrc]->getName() == RC2.getName()) {
            if (!Empty)
              OS << ", ";
            OS << "&" << getQualifiedName(RC2.TheDef) << "RegClass";
            Empty = false;

            std::map<unsigned, std::set<unsigned> >::iterator SCMI =
              SuperRegClassMap.find(rc2);
            if (SCMI == SuperRegClassMap.end()) {
              SuperRegClassMap.insert(std::make_pair(rc2, std::set<unsigned>()));
              SCMI = SuperRegClassMap.find(rc2);
            }
            SCMI->second.insert(rc);
            break;
          }
        }
        if (rc2 == e2)
          throw "Register Class member '" +
            RC.SubRegClasses[subrc]->getName() +
            "' is not a valid RegisterClass!";
      }

      OS << (!Empty ? ", " : "") << "NULL";
      OS << "\n  };\n\n";
    }

    // Emit the super-register classes for each RegisterClass
    for (unsigned rc = 0, e = RegisterClasses.size(); rc != e; ++rc) {
      const CodeGenRegisterClass &RC = RegisterClasses[rc];

      // Give the register class a legal C name if it's anonymous.
      std::string Name = RC.TheDef->getName();

      OS << "  // " << Name
         << " Super-register Classess...\n"
         << "  static const TargetRegisterClass* const "
         << Name << "SuperRegClasses [] = {\n    ";

      bool Empty = true;
      std::map<unsigned, std::set<unsigned> >::iterator I =
        SuperRegClassMap.find(rc);
      if (I != SuperRegClassMap.end()) {
        for (std::set<unsigned>::iterator II = I->second.begin(),
               EE = I->second.end(); II != EE; ++II) {
          const CodeGenRegisterClass &RC2 = RegisterClasses[*II];
          if (!Empty)
            OS << ", ";
          OS << "&" << getQualifiedName(RC2.TheDef) << "RegClass";
          Empty = false;
        }
      }

      OS << (!Empty ? ", " : "") << "NULL";
      OS << "\n  };\n\n";
    }

    // Emit the sub-classes array for each RegisterClass
    for (unsigned rc = 0, e = RegisterClasses.size(); rc != e; ++rc) {
      const CodeGenRegisterClass &RC = RegisterClasses[rc];

      // Give the register class a legal C name if it's anonymous.
      std::string Name = RC.TheDef->getName();

      std::set<Record*> RegSet;
      for (unsigned i = 0, e = RC.Elements.size(); i != e; ++i) {
        Record *Reg = RC.Elements[i];
        RegSet.insert(Reg);
      }

      OS << "  // " << Name
         << " Register Class sub-classes...\n"
         << "  static const TargetRegisterClass* const "
         << Name << "Subclasses [] = {\n    ";

      bool Empty = true;
      for (unsigned rc2 = 0, e2 = RegisterClasses.size(); rc2 != e2; ++rc2) {
        const CodeGenRegisterClass &RC2 = RegisterClasses[rc2];
        if (rc == rc2 || RC2.Elements.size() > RC.Elements.size() ||
            RC.SpillSize != RC2.SpillSize || !isSubRegisterClass(RC2, RegSet))
          continue;

        if (!Empty) OS << ", ";
        OS << "&" << getQualifiedName(RC2.TheDef) << "RegClass";
        Empty = false;

        std::map<unsigned, std::set<unsigned> >::iterator SCMI =
          SuperClassMap.find(rc2);
        if (SCMI == SuperClassMap.end()) {
          SuperClassMap.insert(std::make_pair(rc2, std::set<unsigned>()));
          SCMI = SuperClassMap.find(rc2);
        }
        SCMI->second.insert(rc);
      }

      OS << (!Empty ? ", " : "") << "NULL";
      OS << "\n  };\n\n";
    }

    for (unsigned rc = 0, e = RegisterClasses.size(); rc != e; ++rc) {
      const CodeGenRegisterClass &RC = RegisterClasses[rc];

      // Give the register class a legal C name if it's anonymous.
      std::string Name = RC.TheDef->getName();

      OS << "  // " << Name
         << " Register Class super-classes...\n"
         << "  static const TargetRegisterClass* const "
         << Name << "Superclasses [] = {\n    ";

      bool Empty = true;
      std::map<unsigned, std::set<unsigned> >::iterator I =
        SuperClassMap.find(rc);
      if (I != SuperClassMap.end()) {
        for (std::set<unsigned>::iterator II = I->second.begin(),
               EE = I->second.end(); II != EE; ++II) {
          const CodeGenRegisterClass &RC2 = RegisterClasses[*II];
          if (!Empty) OS << ", ";
          OS << "&" << getQualifiedName(RC2.TheDef) << "RegClass";
          Empty = false;
        }
      }

      OS << (!Empty ? ", " : "") << "NULL";
      OS << "\n  };\n\n";
    }


    for (unsigned i = 0, e = RegisterClasses.size(); i != e; ++i) {
      const CodeGenRegisterClass &RC = RegisterClasses[i];
      OS << RC.MethodBodies << "\n";
      OS << RC.getName() << "Class::" << RC.getName()
         << "Class()  : TargetRegisterClass("
         << RC.getName() + "RegClassID" << ", "
         << RC.getName() + "VTs" << ", "
         << RC.getName() + "Subclasses" << ", "
         << RC.getName() + "Superclasses" << ", "
         << RC.getName() + "SubRegClasses" << ", "
         << RC.getName() + "SuperRegClasses" << ", "
         << RC.SpillSize/8 << ", "
         << RC.SpillAlignment/8 << ", "
         << RC.CopyCost << ", "
         << RC.getName() << ", " << RC.getName() << " + " << RC.Elements.size()
         << ") {}\n";
    }

    OS << "}\n";
  }

  OS << "\nnamespace {\n";
  OS << "  const TargetRegisterClass* const RegisterClasses[] = {\n";
  for (unsigned i = 0, e = RegisterClasses.size(); i != e; ++i)
    OS << "    &" << getQualifiedName(RegisterClasses[i].TheDef)
       << "RegClass,\n";
  OS << "  };\n";

  // Emit register sub-registers / super-registers, aliases...
  std::map<Record*, std::set<Record*> > RegisterSubRegs;
  std::map<Record*, std::set<Record*> > RegisterSuperRegs;
  std::map<Record*, std::set<Record*> > RegisterAliases;
  std::map<Record*, std::vector<std::pair<int, Record*> > > SubRegVectors;
  std::map<Record*, std::vector<int> > DwarfRegNums;

  const std::vector<CodeGenRegister> &Regs = Target.getRegisters();

  for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
    Record *R = Regs[i].TheDef;
    std::vector<Record*> LI = Regs[i].TheDef->getValueAsListOfDefs("Aliases");
    // Add information that R aliases all of the elements in the list... and
    // that everything in the list aliases R.
    for (unsigned j = 0, e = LI.size(); j != e; ++j) {
      Record *Reg = LI[j];
      if (RegisterAliases[R].count(Reg))
        cerr << "Warning: register alias between " << getQualifiedName(R)
             << " and " << getQualifiedName(Reg)
             << " specified multiple times!\n";
      RegisterAliases[R].insert(Reg);

      if (RegisterAliases[Reg].count(R))
        cerr << "Warning: register alias between " << getQualifiedName(R)
             << " and " << getQualifiedName(Reg)
             << " specified multiple times!\n";
      RegisterAliases[Reg].insert(R);
    }
  }

  // Process sub-register sets.
  for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
    Record *R = Regs[i].TheDef;
    std::vector<Record*> LI = Regs[i].TheDef->getValueAsListOfDefs("SubRegs");
    // Process sub-register set and add aliases information.
    for (unsigned j = 0, e = LI.size(); j != e; ++j) {
      Record *SubReg = LI[j];
      if (RegisterSubRegs[R].count(SubReg))
        cerr << "Warning: register " << getQualifiedName(SubReg)
             << " specified as a sub-register of " << getQualifiedName(R)
             << " multiple times!\n";
      addSubSuperReg(R, SubReg, RegisterSubRegs, RegisterSuperRegs,
                     RegisterAliases);
    }
  }

  // Print the SubregHashTable, a simple quadratically probed
  // hash table for determining if a register is a subregister
  // of another register.
  unsigned NumSubRegs = 0;
  std::map<Record*, unsigned> RegNo;
  for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
    RegNo[Regs[i].TheDef] = i;
    NumSubRegs += RegisterSubRegs[Regs[i].TheDef].size();
  }

  unsigned SubregHashTableSize = NextPowerOf2(2 * NumSubRegs);
  unsigned* SubregHashTable = new unsigned[2 * SubregHashTableSize];
  std::fill(SubregHashTable, SubregHashTable + 2 * SubregHashTableSize, ~0U);

  for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
    Record* R = Regs[i].TheDef;
    for (std::set<Record*>::iterator I = RegisterSubRegs[R].begin(),
         E = RegisterSubRegs[R].end(); I != E; ++I) {
      Record* RJ = *I;
      // We have to increase the indices of both registers by one when
      // computing the hash because, in the generated code, there
      // will be an extra empty slot at register 0.
      size_t index = ((i+1) + (RegNo[RJ]+1) * 37) & (SubregHashTableSize-1);
      unsigned ProbeAmt = 2;
      while (SubregHashTable[index*2] != ~0U &&
             SubregHashTable[index*2+1] != ~0U) {
        index = (index + ProbeAmt) & (SubregHashTableSize-1);
        ProbeAmt += 2;
      }

      SubregHashTable[index*2] = i;
      SubregHashTable[index*2+1] = RegNo[RJ];
    }
  }

  if (SubregHashTableSize) {
    std::string Namespace = Regs[0].TheDef->getValueAsString("Namespace");

    OS << "\n\n  unsigned SubregHashTable[] = {";
    for (unsigned i = 0; i < SubregHashTableSize - 1; ++i) {
      if (SubregHashTable[2*i] != ~0U) {
        OS << getQualifiedName(Regs[SubregHashTable[2*i]].TheDef) << ", "
           << getQualifiedName(Regs[SubregHashTable[2*i+1]].TheDef) << ", ";
      } else {
        OS << Namespace << "::NoRegister, " << Namespace << "::NoRegister, ";
      }
    }

    unsigned Idx = SubregHashTableSize*2-2;
    if (SubregHashTable[Idx] != ~0U) {
      OS << getQualifiedName(Regs[SubregHashTable[Idx]].TheDef) << ", "
         << getQualifiedName(Regs[SubregHashTable[Idx+1]].TheDef) << "};\n";
    } else {
      OS << Namespace << "::NoRegister, " << Namespace << "::NoRegister};\n";
    }

    OS << "  unsigned SubregHashTableSize = "
       << SubregHashTableSize << ";\n";
  } else {
    OS << "\n\n  unsigned SubregHashTable[] = { ~0U, ~0U };\n"
       << "  unsigned SubregHashTableSize = 1;\n";
  }

  free(SubregHashTable);

  if (!RegisterAliases.empty())
    OS << "\n\n  // Register Alias Sets...\n";

  // Emit the empty alias list
  OS << "  const unsigned Empty_AliasSet[] = { 0 };\n";
  // Loop over all of the registers which have aliases, emitting the alias list
  // to memory.
  for (std::map<Record*, std::set<Record*> >::iterator
         I = RegisterAliases.begin(), E = RegisterAliases.end(); I != E; ++I) {
    OS << "  const unsigned " << I->first->getName() << "_AliasSet[] = { ";
    for (std::set<Record*>::iterator ASI = I->second.begin(),
           E = I->second.end(); ASI != E; ++ASI)
      OS << getQualifiedName(*ASI) << ", ";
    OS << "0 };\n";
  }

  if (!RegisterSubRegs.empty())
    OS << "\n\n  // Register Sub-registers Sets...\n";

  // Emit the empty sub-registers list
  OS << "  const unsigned Empty_SubRegsSet[] = { 0 };\n";
  // Loop over all of the registers which have sub-registers, emitting the
  // sub-registers list to memory.
  for (std::map<Record*, std::set<Record*> >::iterator
         I = RegisterSubRegs.begin(), E = RegisterSubRegs.end(); I != E; ++I) {
    OS << "  const unsigned " << I->first->getName() << "_SubRegsSet[] = { ";
    std::vector<Record*> SubRegsVector;
    for (std::set<Record*>::iterator ASI = I->second.begin(),
           E = I->second.end(); ASI != E; ++ASI)
      SubRegsVector.push_back(*ASI);
    RegisterSorter RS(RegisterSubRegs);
    std::stable_sort(SubRegsVector.begin(), SubRegsVector.end(), RS);
    for (unsigned i = 0, e = SubRegsVector.size(); i != e; ++i)
      OS << getQualifiedName(SubRegsVector[i]) << ", ";
    OS << "0 };\n";
  }

  if (!RegisterSuperRegs.empty())
    OS << "\n\n  // Register Super-registers Sets...\n";

  // Emit the empty super-registers list
  OS << "  const unsigned Empty_SuperRegsSet[] = { 0 };\n";
  // Loop over all of the registers which have super-registers, emitting the
  // super-registers list to memory.
  for (std::map<Record*, std::set<Record*> >::iterator
         I = RegisterSuperRegs.begin(), E = RegisterSuperRegs.end(); I != E; ++I) {
    OS << "  const unsigned " << I->first->getName() << "_SuperRegsSet[] = { ";

    std::vector<Record*> SuperRegsVector;
    for (std::set<Record*>::iterator ASI = I->second.begin(),
           E = I->second.end(); ASI != E; ++ASI)
      SuperRegsVector.push_back(*ASI);
    RegisterSorter RS(RegisterSubRegs);
    std::stable_sort(SuperRegsVector.begin(), SuperRegsVector.end(), RS);
    for (unsigned i = 0, e = SuperRegsVector.size(); i != e; ++i)
      OS << getQualifiedName(SuperRegsVector[i]) << ", ";
    OS << "0 };\n";
  }

  OS<<"\n  const TargetRegisterDesc RegisterDescriptors[] = { // Descriptors\n";
  OS << "    { \"NOREG\",\t\"NOREG\",\t0,\t0,\t0 },\n";

  // Now that register alias and sub-registers sets have been emitted, emit the
  // register descriptors now.
  const std::vector<CodeGenRegister> &Registers = Target.getRegisters();
  for (unsigned i = 0, e = Registers.size(); i != e; ++i) {
    const CodeGenRegister &Reg = Registers[i];
    OS << "    { \"";
    if (!Reg.TheDef->getValueAsString("AsmName").empty())
      OS << Reg.TheDef->getValueAsString("AsmName");
    else
      OS << Reg.getName();
    OS << "\",\t\"";
    if (!Reg.TheDef->getValueAsString("Name").empty()) {
      OS << Reg.TheDef->getValueAsString("Name");
    } else {
      // Default to "name".
      if (!Reg.TheDef->getValueAsString("AsmName").empty())
        OS << Reg.TheDef->getValueAsString("AsmName");
      else
        OS << Reg.getName();
    }
    OS << "\",\t";
    if (RegisterAliases.count(Reg.TheDef))
      OS << Reg.getName() << "_AliasSet,\t";
    else
      OS << "Empty_AliasSet,\t";
    if (RegisterSubRegs.count(Reg.TheDef))
      OS << Reg.getName() << "_SubRegsSet,\t";
    else
      OS << "Empty_SubRegsSet,\t";
    if (RegisterSuperRegs.count(Reg.TheDef))
      OS << Reg.getName() << "_SuperRegsSet },\n";
    else
      OS << "Empty_SuperRegsSet },\n";
  }
  OS << "  };\n";      // End of register descriptors...
  OS << "}\n\n";       // End of anonymous namespace...

  std::string ClassName = Target.getName() + "GenRegisterInfo";

  // Calculate the mapping of subregister+index pairs to physical registers.
  std::vector<Record*> SubRegs = Records.getAllDerivedDefinitions("SubRegSet");
  for (unsigned i = 0, e = SubRegs.size(); i != e; ++i) {
    int subRegIndex = SubRegs[i]->getValueAsInt("index");
    std::vector<Record*> From = SubRegs[i]->getValueAsListOfDefs("From");
    std::vector<Record*> To   = SubRegs[i]->getValueAsListOfDefs("To");

    if (From.size() != To.size()) {
      cerr << "Error: register list and sub-register list not of equal length"
           << " in SubRegSet\n";
      exit(1);
    }

    // For each entry in from/to vectors, insert the to register at index
    for (unsigned ii = 0, ee = From.size(); ii != ee; ++ii)
      SubRegVectors[From[ii]].push_back(std::make_pair(subRegIndex, To[ii]));
  }

  // Emit the subregister + index mapping function based on the information
  // calculated above.
  OS << "unsigned " << ClassName
     << "::getSubReg(unsigned RegNo, unsigned Index) const {\n"
     << "  switch (RegNo) {\n"
     << "  default: abort(); break;\n";
  for (std::map<Record*, std::vector<std::pair<int, Record*> > >::iterator
        I = SubRegVectors.begin(), E = SubRegVectors.end(); I != E; ++I) {
    OS << "  case " << getQualifiedName(I->first) << ":\n";
    OS << "    switch (Index) {\n";
    OS << "    default: abort(); break;\n";
    for (unsigned i = 0, e = I->second.size(); i != e; ++i)
      OS << "    case " << (I->second)[i].first << ": return "
         << getQualifiedName((I->second)[i].second) << ";\n";
    OS << "    }; break;\n";
  }
  OS << "  };\n";
  OS << "  return 0;\n";
  OS << "}\n\n";

  // Emit the constructor of the class...
  OS << ClassName << "::" << ClassName
     << "(int CallFrameSetupOpcode, int CallFrameDestroyOpcode)\n"
     << "  : TargetRegisterInfo(RegisterDescriptors, " << Registers.size()+1
     << ", RegisterClasses, RegisterClasses+" << RegisterClasses.size() <<",\n "
     << "                 CallFrameSetupOpcode, CallFrameDestroyOpcode) {\n"
     << "  this->SubregHash = SubregHashTable;\n"
     << "  this->SubregHashSize = SubregHashTableSize;\n"
     << "}\n\n";

  // Collect all information about dwarf register numbers

  // First, just pull all provided information to the map
  unsigned maxLength = 0;
  for (unsigned i = 0, e = Registers.size(); i != e; ++i) {
    Record *Reg = Registers[i].TheDef;
    std::vector<int> RegNums = Reg->getValueAsListOfInts("DwarfNumbers");
    maxLength = std::max((size_t)maxLength, RegNums.size());
    if (DwarfRegNums.count(Reg))
      cerr << "Warning: DWARF numbers for register " << getQualifiedName(Reg)
           << "specified multiple times\n";
    DwarfRegNums[Reg] = RegNums;
  }

  // Now we know maximal length of number list. Append -1's, where needed
  for (std::map<Record*, std::vector<int> >::iterator
        I = DwarfRegNums.begin(), E = DwarfRegNums.end(); I != E; ++I)
    for (unsigned i = I->second.size(), e = maxLength; i != e; ++i)
      I->second.push_back(-1);

  // Emit information about the dwarf register numbers.
  OS << "int " << ClassName << "::getDwarfRegNumFull(unsigned RegNum, "
     << "unsigned Flavour) const {\n"
     << "  switch (Flavour) {\n"
     << "  default:\n"
     << "    assert(0 && \"Unknown DWARF flavour\");\n"
     << "    return -1;\n";

  for (unsigned i = 0, e = maxLength; i != e; ++i) {
    OS << "  case " << i << ":\n"
       << "    switch (RegNum) {\n"
       << "    default:\n"
       << "      assert(0 && \"Invalid RegNum\");\n"
       << "      return -1;\n";

    for (std::map<Record*, std::vector<int> >::iterator
           I = DwarfRegNums.begin(), E = DwarfRegNums.end(); I != E; ++I) {
      int RegNo = I->second[i];
      if (RegNo != -2)
        OS << "    case " << getQualifiedName(I->first) << ":\n"
           << "      return " << RegNo << ";\n";
      else
        OS << "    case " << getQualifiedName(I->first) << ":\n"
           << "      assert(0 && \"Invalid register for this mode\");\n"
           << "      return -1;\n";
    }
    OS << "    };\n";
  }

  OS << "  };\n}\n\n";

  OS << "} // End llvm namespace \n";
}