lib/Target/CBackend/CBackend.cpp

//===-- Writer.cpp - Library for converting LLVM code to C ----------------===//
//
// This library implements the functionality defined in llvm/Assembly/CWriter.h
//
// TODO : Recursive types.
//
//===-----------------------------------------------------------------------==//

#include "llvm/Assembly/CWriter.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Function.h"
#include "llvm/Argument.h"
#include "llvm/BasicBlock.h"
#include "llvm/iMemory.h"
#include "llvm/iTerminators.h"
#include "llvm/iPHINode.h"
#include "llvm/iOther.h"
#include "llvm/iOperators.h"
#include "llvm/SymbolTable.h"
#include "llvm/SlotCalculator.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/InstIterator.h"
#include "Support/StringExtras.h"
#include "Support/STLExtras.h"
#include <algorithm>
using std::string;
using std::map;
using std::ostream;

static std::string getConstStrValue(const Constant* CPV);


static std::string getConstArrayStrValue(const Constant* CPV) {
  std::string Result;
  
  // As a special case, print the array as a string if it is an array of
  // ubytes or an array of sbytes with positive values.
  // 
  const Type *ETy = cast<ArrayType>(CPV->getType())->getElementType();
  bool isString = (ETy == Type::SByteTy || ETy == Type::UByteTy);

  // Make sure the last character is a null char, as automatically added by C
  if (CPV->getNumOperands() == 0 ||
      !cast<Constant>(*(CPV->op_end()-1))->isNullValue())
    isString = false;
  
  if (isString) {
    Result = "\"";
    // Do not include the last character, which we know is null
    for (unsigned i = 0, e = CPV->getNumOperands()-1; i != e; ++i) {
      unsigned char C = (ETy == Type::SByteTy) ?
        (unsigned char)cast<ConstantSInt>(CPV->getOperand(i))->getValue() :
        (unsigned char)cast<ConstantUInt>(CPV->getOperand(i))->getValue();
      
      if (isprint(C)) {
        Result += C;
      } else {
        switch (C) {
        case '\n': Result += "\\n"; break;
        case '\t': Result += "\\t"; break;
        case '\r': Result += "\\r"; break;
        case '\v': Result += "\\v"; break;
        case '\a': Result += "\\a"; break;
        default:
          Result += "\\x";
          Result += ( C/16  < 10) ? ( C/16 +'0') : ( C/16 -10+'A');
          Result += ((C&15) < 10) ? ((C&15)+'0') : ((C&15)-10+'A');
          break;
        }
      }
    }
    Result += "\"";
  } else {
    Result = "{";
    if (CPV->getNumOperands()) {
      Result += " " +  getConstStrValue(cast<Constant>(CPV->getOperand(0)));
      for (unsigned i = 1; i < CPV->getNumOperands(); i++)
        Result += ", " + getConstStrValue(cast<Constant>(CPV->getOperand(i)));
    }
    Result += " }";
  }
  
  return Result;
}

static std::string getConstStrValue(const Constant* CPV) {
  switch (CPV->getType()->getPrimitiveID()) {
  case Type::BoolTyID:  return CPV == ConstantBool::False ? "0" : "1";
  case Type::SByteTyID:
  case Type::ShortTyID:
  case Type::IntTyID:   return itostr(cast<ConstantSInt>(CPV)->getValue());
  case Type::LongTyID:  return itostr(cast<ConstantSInt>(CPV)->getValue())+"ll";

  case Type::UByteTyID:
  case Type::UShortTyID:return utostr(cast<ConstantUInt>(CPV)->getValue());
  case Type::UIntTyID:  return utostr(cast<ConstantUInt>(CPV)->getValue())+"u";
  case Type::ULongTyID:return utostr(cast<ConstantUInt>(CPV)->getValue())+"ull";

  case Type::FloatTyID:
  case Type::DoubleTyID: return ftostr(cast<ConstantFP>(CPV)->getValue());

  case Type::ArrayTyID:  return getConstArrayStrValue(CPV);

  case Type::StructTyID: {
    std::string Result = "{";
    if (CPV->getNumOperands()) {
      Result += " " + getConstStrValue(cast<Constant>(CPV->getOperand(0)));
      for (unsigned i = 1; i < CPV->getNumOperands(); i++)
        Result += ", " + getConstStrValue(cast<Constant>(CPV->getOperand(i)));
    }
    return Result + " }";
  }

  default:
    cerr << "Unknown constant type: " << CPV << "\n";
    abort();
  }
}

// Pass the Type* variable and and the variable name and this prints out the 
// variable declaration.
//
static string calcTypeNameVar(const Type *Ty,
                              map<const Type *, string> &TypeNames, 
                              const string &NameSoFar, bool ignoreName = false){
  if (Ty->isPrimitiveType())
    switch (Ty->getPrimitiveID()) {
    case Type::VoidTyID:   return "void " + NameSoFar;
    case Type::BoolTyID:   return "bool " + NameSoFar;
    case Type::UByteTyID:  return "unsigned char " + NameSoFar;
    case Type::SByteTyID:  return "signed char " + NameSoFar;
    case Type::UShortTyID: return "unsigned short " + NameSoFar;
    case Type::ShortTyID:  return "short " + NameSoFar;
    case Type::UIntTyID:   return "unsigned " + NameSoFar;
    case Type::IntTyID:    return "int " + NameSoFar;
    case Type::ULongTyID:  return "unsigned long long " + NameSoFar;
    case Type::LongTyID:   return "signed long long " + NameSoFar;
    case Type::FloatTyID:  return "float " + NameSoFar;
    case Type::DoubleTyID: return "double " + NameSoFar;
    default :
      cerr << "Unknown primitive type: " << Ty << "\n";
      abort();
    }
  
  // Check to see if the type is named.
  if (!ignoreName) {
    map<const Type *, string>::iterator I = TypeNames.find(Ty);
    if (I != TypeNames.end())
      return I->second + " " + NameSoFar;
  }  

  string Result;
  switch (Ty->getPrimitiveID()) {
  case Type::FunctionTyID: {
    const FunctionType *MTy = cast<FunctionType>(Ty);
    Result += calcTypeNameVar(MTy->getReturnType(), TypeNames, "");
    Result += " " + NameSoFar + " (";
    for (FunctionType::ParamTypes::const_iterator
           I = MTy->getParamTypes().begin(),
           E = MTy->getParamTypes().end(); I != E; ++I) {
      if (I != MTy->getParamTypes().begin())
        Result += ", ";
      Result += calcTypeNameVar(*I, TypeNames, "");
    }
    if (MTy->isVarArg()) {
      if (!MTy->getParamTypes().empty()) 
	Result += ", ";
      Result += "...";
    }
    return Result + ")";
  }
  case Type::StructTyID: {
    const StructType *STy = cast<const StructType>(Ty);
    Result = NameSoFar + " {\n";
    unsigned indx = 0;
    for (StructType::ElementTypes::const_iterator
           I = STy->getElementTypes().begin(),
           E = STy->getElementTypes().end(); I != E; ++I) {
      Result += "  " +calcTypeNameVar(*I, TypeNames, "field" + utostr(indx++));
      Result += ";\n";
    }
    return Result + "}";
  }  

  case Type::PointerTyID:
    return calcTypeNameVar(cast<const PointerType>(Ty)->getElementType(), 
                           TypeNames, "*" + NameSoFar);
  
  case Type::ArrayTyID: {
    const ArrayType *ATy = cast<const ArrayType>(Ty);
    int NumElements = ATy->getNumElements();
    return calcTypeNameVar(ATy->getElementType(), TypeNames, 
                           NameSoFar + "[" + itostr(NumElements) + "]");
  }
  default:
    assert(0 && "Unhandled case in getTypeProps!");
    abort();
  }

  return Result;
}

namespace {
  class CWriter : public InstVisitor<CWriter> {
    ostream& Out; 
    SlotCalculator &Table;
    const Module *TheModule;
    map<const Type *, string> TypeNames;
  public:
    inline CWriter(ostream &o, SlotCalculator &Tab, const Module *M)
      : Out(o), Table(Tab), TheModule(M) {
    }
    
    inline void write(Module *M) { printModule(M); }

    ostream& printType(const Type *Ty, const string &VariableName = "") {
      return Out << calcTypeNameVar(Ty, TypeNames, VariableName);
    }

    void writeOperand(const Value *Operand);
    void writeOperandInternal(const Value *Operand);

    string getValueName(const Value *V);

  private :
    void printModule(Module *M);
    void printSymbolTable(const SymbolTable &ST);
    void printGlobal(const GlobalVariable *GV);
    void printFunctionSignature(const Function *F);
    void printFunctionDecl(const Function *F); // Print just the forward decl
    
    void printFunction(Function *);

    // isInlinableInst - Attempt to inline instructions into their uses to build
    // trees as much as possible.  To do this, we have to consistently decide
    // what is acceptable to inline, so that variable declarations don't get
    // printed and an extra copy of the expr is not emitted.
    //
    static bool isInlinableInst(Instruction *I) {
      // Must be an expression, must be used exactly once.  If it is dead, we
      // emit it inline where it would go.
      if (I->getType() == Type::VoidTy || I->use_size() != 1 ||
          isa<TerminatorInst>(I) || isa<CallInst>(I) || isa<PHINode>(I))
        return false;

      // Only inline instruction it it's use is in the same BB as the inst.
      return I->getParent() == cast<Instruction>(I->use_back())->getParent();
    }

    // Instruction visitation functions
    friend class InstVisitor<CWriter>;

    void visitReturnInst(ReturnInst *I);
    void visitBranchInst(BranchInst *I);

    void visitPHINode(PHINode *I) {}
    void visitNot(GenericUnaryInst *I);
    void visitBinaryOperator(Instruction *I);

    void visitCastInst(CastInst *I);
    void visitCallInst(CallInst *I);
    void visitShiftInst(ShiftInst *I) { visitBinaryOperator(I); }

    void visitMallocInst(MallocInst *I);
    void visitAllocaInst(AllocaInst *I);
    void visitFreeInst(FreeInst   *I);
    void visitLoadInst(LoadInst   *I);
    void visitStoreInst(StoreInst  *I);
    void visitGetElementPtrInst(GetElementPtrInst *I);

    void visitInstruction(Instruction *I) {
      cerr << "C Writer does not know about " << I;
      abort();
    }

    void outputLValue(Instruction *I) {
      Out << "  " << getValueName(I) << " = ";
    }
    void printBranchToBlock(BasicBlock *CurBlock, BasicBlock *SuccBlock,
                            unsigned Indent);
    void printIndexingExpr(MemAccessInst *MAI);
  };
}

// We dont want identifier names with ., space, -  in them. 
// So we replace them with _
static string makeNameProper(string x) {
  string tmp;
  for (string::iterator sI = x.begin(), sEnd = x.end(); sI != sEnd; sI++)
    switch (*sI) {
    case '.': tmp += "d_"; break;
    case ' ': tmp += "s_"; break;
    case '-': tmp += "D_"; break;
    case '_': tmp += "__"; break;
    default:  tmp += *sI;
    }

  return tmp;
}

string CWriter::getValueName(const Value *V) {
  if (V->hasName()) {             // Print out the label if it exists...
    if (isa<GlobalValue>(V))  // Do not mangle globals...
      return makeNameProper(V->getName());

    return "l" + utostr(V->getType()->getUniqueID()) + "_" +
           makeNameProper(V->getName());      
  }

  int Slot = Table.getValSlot(V);
  assert(Slot >= 0 && "Invalid value!");
  return "ltmp_" + itostr(Slot) + "_" + utostr(V->getType()->getUniqueID());
}

void CWriter::writeOperandInternal(const Value *Operand) {
  if (Operand->hasName()) {   
    Out << getValueName(Operand);
  } else if (const Constant *CPV = dyn_cast<const Constant>(Operand)) {
    if (isa<ConstantPointerNull>(CPV)) {
      Out << "((";
      printType(CPV->getType(), "");
      Out << ")NULL)";
    } else
      Out << getConstStrValue(CPV); 
  } else {
    int Slot = Table.getValSlot(Operand);
    assert(Slot >= 0 && "Malformed LLVM!");
    Out << "ltmp_" << Slot << "_" << Operand->getType()->getUniqueID();
  }
}

void CWriter::writeOperand(const Value *Operand) {
  if (Instruction *I = dyn_cast<Instruction>(Operand))
    if (isInlinableInst(I)) {
      // Should we inline this instruction to build a tree?
      Out << "(";
      visit(I);
      Out << ")";    
      return;
    }

  if (isa<GlobalVariable>(Operand))
    Out << "(&";  // Global variables are references as their addresses by llvm

  writeOperandInternal(Operand);

  if (isa<GlobalVariable>(Operand))
    Out << ")";
}

void CWriter::printModule(Module *M) {
  // printing stdlib inclusion
  // Out << "#include <stdlib.h>\n";

  // get declaration for alloca
  Out << "/* Provide Declarations */\n"
      << "#include <alloca.h>\n\n"

    // Provide a definition for null if one does not already exist.
      << "#ifndef NULL\n#define NULL 0\n#endif\n\n"
      << "typedef unsigned char bool;\n"

      << "\n\n/* Global Symbols */\n";

  // Loop over the symbol table, emitting all named constants...
  if (M->hasSymbolTable())
    printSymbolTable(*M->getSymbolTable());

  Out << "\n\n/* Global Data */\n";
  for (Module::const_giterator I = M->gbegin(), E = M->gend(); I != E; ++I) {
    GlobalVariable *GV = *I;
    if (GV->hasInternalLinkage()) Out << "static ";
    printType(GV->getType()->getElementType(), getValueName(GV));

    if (GV->hasInitializer()) {
      Out << " = " ;
      writeOperand(GV->getInitializer());
    }
    Out << ";\n";
  }

  // First output all the declarations of the functions as C requires Functions 
  // be declared before they are used.
  //
  Out << "\n\n/* Function Declarations */\n";
  for_each(M->begin(), M->end(), bind_obj(this, &CWriter::printFunctionDecl));
  
  // Output all of the functions...
  Out << "\n\n/* Function Bodies */\n";
  for_each(M->begin(), M->end(), bind_obj(this, &CWriter::printFunction));
}


// printSymbolTable - Run through symbol table looking for named constants
// if a named constant is found, emit it's declaration...
// Assuming that symbol table has only types and constants.
void CWriter::printSymbolTable(const SymbolTable &ST) {
  for (SymbolTable::const_iterator TI = ST.begin(); TI != ST.end(); ++TI) {
    SymbolTable::type_const_iterator I = ST.type_begin(TI->first);
    SymbolTable::type_const_iterator End = ST.type_end(TI->first);
    
    for (; I != End; ++I)
      if (const Type *Ty = dyn_cast<const StructType>(I->second)) {
	string Name = "struct l_" + I->first;
        Out << Name << ";\n";

        TypeNames.insert(std::make_pair(Ty, Name));
      }
  }

  Out << "\n";

  for (SymbolTable::const_iterator TI = ST.begin(); TI != ST.end(); ++TI) {
    SymbolTable::type_const_iterator I = ST.type_begin(TI->first);
    SymbolTable::type_const_iterator End = ST.type_end(TI->first);
    
    for (; I != End; ++I) {
      const Value *V = I->second;
      if (const Type *Ty = dyn_cast<const Type>(V)) {
	string Name = "l_" + I->first;
        if (isa<StructType>(Ty))
          Name = "struct " + Name;
        else
          Out << "typedef ";

	Out << calcTypeNameVar(Ty, TypeNames, Name, true) << ";\n";
      }
    }
  }
}


// printFunctionDecl - Print function declaration
//
void CWriter::printFunctionDecl(const Function *F) {
  printFunctionSignature(F);
  Out << ";\n";
}

void CWriter::printFunctionSignature(const Function *F) {
  if (F->hasInternalLinkage()) Out << "static ";
  
  // Loop over the arguments, printing them...
  const FunctionType *FT = cast<FunctionType>(F->getFunctionType());
  
  // Print out the return type and name...
  printType(F->getReturnType());
  Out << getValueName(F) << "(";
    
  if (!F->isExternal()) {
    if (!F->getArgumentList().empty()) {
      printType(F->getArgumentList().front()->getType(),
                getValueName(F->getArgumentList().front()));

      for (Function::ArgumentListType::const_iterator
             I = F->getArgumentList().begin()+1,
             E = F->getArgumentList().end(); I != E; ++I) {
        Out << ", ";
        printType((*I)->getType(), getValueName(*I));
      }
    }
  } else {
    // Loop over the arguments, printing them...
    for (FunctionType::ParamTypes::const_iterator I = 
	   FT->getParamTypes().begin(),
	   E = FT->getParamTypes().end(); I != E; ++I) {
      if (I != FT->getParamTypes().begin()) Out << ", ";
      printType(*I);
    }
  }

  // Finish printing arguments...
  if (FT->isVarArg()) {
    if (FT->getParamTypes().size()) Out << ", ";
    Out << "...";  // Output varargs portion of signature!
  }
  Out << ")";
}


void CWriter::printFunction(Function *F) {
  if (F->isExternal()) return;

  Table.incorporateFunction(F);

  printFunctionSignature(F);
  Out << " {\n";

  // print local variable information for the function
  for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
    if ((*I)->getType() != Type::VoidTy && !isInlinableInst(*I)) {
      Out << "  ";
      printType((*I)->getType(), getValueName(*I));
      Out << ";\n";
    }
 
  // print the basic blocks
  for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
    BasicBlock *BB = *I, *Prev = I != F->begin() ? *(I-1) : 0;

    // Don't print the label for the basic block if there are no uses, or if the
    // only terminator use is the precessor basic block's terminator.  We have
    // to scan the use list because PHI nodes use basic blocks too but do not
    // require a label to be generated.
    //
    bool NeedsLabel = false;
    for (Value::use_iterator UI = BB->use_begin(), UE = BB->use_end();
         UI != UE; ++UI)
      if (TerminatorInst *TI = dyn_cast<TerminatorInst>(*UI))
        if (TI != Prev->getTerminator()) {
          NeedsLabel = true;
          break;        
        }

    if (NeedsLabel) Out << getValueName(BB) << ":\n";

    // Output all of the instructions in the basic block...
    for (BasicBlock::iterator II = BB->begin(), E = BB->end()-1;
         II != E; ++II) {
      if (!isInlinableInst(*II) && !isa<PHINode>(*II)) {
        Instruction *I = *II;
        if (I->getType() != Type::VoidTy)
          outputLValue(I);
        else
          Out << "  ";
        visit(I);
        Out << ";\n";
      }
    }

    // Don't emit prefix or suffix for the terminator...
    visit(BB->getTerminator());
  }
  
  Out << "}\n\n";
  Table.purgeFunction();
}

// Specific Instruction type classes... note that all of the casts are
// neccesary because we use the instruction classes as opaque types...
//
void CWriter::visitReturnInst(ReturnInst *I) {
  // Don't output a void return if this is the last basic block in the function
  if (I->getNumOperands() == 0 && 
      *(I->getParent()->getParent()->end()-1) == I->getParent())
    return;

  Out << "  return";
  if (I->getNumOperands()) {
    Out << " ";
    writeOperand(I->getOperand(0));
  }
  Out << ";\n";
}

// Return true if BB1 immediately preceeds BB2.
static bool BBFollowsBB(BasicBlock *BB1, BasicBlock *BB2) {
  Function *F = BB1->getParent();
  Function::iterator I = find(F->begin(), F->end(), BB1);
  assert(I != F->end() && "BB not in function!");
  return *(I+1) == BB2;  
}

static bool isGotoCodeNeccessary(BasicBlock *From, BasicBlock *To) {
  // If PHI nodes need copies, we need the copy code...
  if (isa<PHINode>(To->front()) ||
      !BBFollowsBB(From, To))      // Not directly successor, need goto
    return true;

  // Otherwise we don't need the code.
  return false;
}

void CWriter::printBranchToBlock(BasicBlock *CurBB, BasicBlock *Succ,
                                           unsigned Indent) {
  for (BasicBlock::iterator I = Succ->begin();
       PHINode *PN = dyn_cast<PHINode>(*I); ++I) {
    //  now we have to do the printing
    Out << string(Indent, ' ');
    outputLValue(PN);
    writeOperand(PN->getIncomingValue(PN->getBasicBlockIndex(CurBB)));
    Out << ";   /* for PHI node */\n";
  }

  if (!BBFollowsBB(CurBB, Succ)) {
    Out << string(Indent, ' ') << "  goto ";
    writeOperand(Succ);
    Out << ";\n";
  }
}

// Brach instruction printing - Avoid printing out a brach to a basic block that
// immediately succeeds the current one.
//
void CWriter::visitBranchInst(BranchInst *I) {
  if (I->isConditional()) {
    if (isGotoCodeNeccessary(I->getParent(), I->getSuccessor(0))) {
      Out << "  if (";
      writeOperand(I->getCondition());
      Out << ") {\n";
      
      printBranchToBlock(I->getParent(), I->getSuccessor(0), 2);
      
      if (isGotoCodeNeccessary(I->getParent(), I->getSuccessor(1))) {
        Out << "  } else {\n";
        printBranchToBlock(I->getParent(), I->getSuccessor(1), 2);
      }
    } else {
      // First goto not neccesary, assume second one is...
      Out << "  if (!";
      writeOperand(I->getCondition());
      Out << ") {\n";

      printBranchToBlock(I->getParent(), I->getSuccessor(1), 2);
    }

    Out << "  }\n";
  } else {
    printBranchToBlock(I->getParent(), I->getSuccessor(0), 0);
  }
  Out << "\n";
}


void CWriter::visitNot(GenericUnaryInst *I) {
  Out << "~";
  writeOperand(I->getOperand(0));
}

void CWriter::visitBinaryOperator(Instruction *I) {
  // binary instructions, shift instructions, setCond instructions.
  if (isa<PointerType>(I->getType())) {
    Out << "(";
    printType(I->getType());
    Out << ")";
  }
      
  if (isa<PointerType>(I->getType())) Out << "(long long)";
  writeOperand(I->getOperand(0));

  switch (I->getOpcode()) {
  case Instruction::Add: Out << " + "; break;
  case Instruction::Sub: Out << " - "; break;
  case Instruction::Mul: Out << "*"; break;
  case Instruction::Div: Out << "/"; break;
  case Instruction::Rem: Out << "%"; break;
  case Instruction::And: Out << " & "; break;
  case Instruction::Or: Out << " | "; break;
  case Instruction::Xor: Out << " ^ "; break;
  case Instruction::SetEQ: Out << " == "; break;
  case Instruction::SetNE: Out << " != "; break;
  case Instruction::SetLE: Out << " <= "; break;
  case Instruction::SetGE: Out << " >= "; break;
  case Instruction::SetLT: Out << " < "; break;
  case Instruction::SetGT: Out << " > "; break;
  case Instruction::Shl : Out << " << "; break;
  case Instruction::Shr : Out << " >> "; break;
  default: cerr << "Invalid operator type!" << I; abort();
  }

  if (isa<PointerType>(I->getType())) Out << "(long long)";
  writeOperand(I->getOperand(1));
}

void CWriter::visitCastInst(CastInst *I) {
  Out << "(";
  printType(I->getType());
  Out << ")";
  writeOperand(I->getOperand(0));
}

void CWriter::visitCallInst(CallInst *I) {
  const PointerType  *PTy   = cast<PointerType>(I->getCalledValue()->getType());
  const FunctionType *FTy   = cast<FunctionType>(PTy->getElementType());
  const Type         *RetTy = FTy->getReturnType();
  
  Out << getValueName(I->getOperand(0)) << "(";

  if (I->getNumOperands() > 1) {
    writeOperand(I->getOperand(1));

    for (unsigned op = 2, Eop = I->getNumOperands(); op != Eop; ++op) {
      Out << ", ";
      writeOperand(I->getOperand(op));
    }
  }
  Out << ")";
}  

void CWriter::visitMallocInst(MallocInst *I) {
  Out << "(";
  printType(I->getType());
  Out << ")malloc(sizeof(";
  printType(I->getType()->getElementType());
  Out << ")";

  if (I->isArrayAllocation()) {
    Out << " * " ;
    writeOperand(I->getOperand(0));
  }
  Out << ")";
}

void CWriter::visitAllocaInst(AllocaInst *I) {
  Out << "(";
  printType(I->getType());
  Out << ") alloca(sizeof(";
  printType(I->getType()->getElementType());
  Out << ")";
  if (I->isArrayAllocation()) {
    Out << " * " ;
    writeOperand(I->getOperand(0));
  }
  Out << ")";
}

void CWriter::visitFreeInst(FreeInst *I) {
  Out << "free(";
  writeOperand(I->getOperand(0));
  Out << ")";
}

void CWriter::printIndexingExpr(MemAccessInst *MAI) {
  MemAccessInst::op_iterator I = MAI->idx_begin(), E = MAI->idx_end();
  if (I == E) {
    // If accessing a global value with no indexing, avoid *(&GV) syndrome
    if (GlobalValue *V = dyn_cast<GlobalValue>(MAI->getPointerOperand())) {
      writeOperandInternal(V);
      return;
    }

    Out << "*";  // Implicit zero first argument: '*x' is equivalent to 'x[0]'
  }

  writeOperand(MAI->getPointerOperand());

  if (I == E) return;

  // Print out the -> operator if possible...
  Constant *CI = dyn_cast<Constant>(*I);
  if (CI && CI->isNullValue() && I+1 != E &&
      (*(I+1))->getType() == Type::UByteTy) {
    Out << "->field" << cast<ConstantUInt>(*(I+1))->getValue();
    I += 2;
  }
    
  for (; I != E; ++I)
    if ((*I)->getType() == Type::UIntTy) {
      Out << "[";
      writeOperand(*I);
      Out << "]";
    } else {
      Out << ".field" << cast<ConstantUInt>(*I)->getValue();
    }
}

void CWriter::visitLoadInst(LoadInst *I) {
  printIndexingExpr(I);
}

void CWriter::visitStoreInst(StoreInst *I) {
  printIndexingExpr(I);
  Out << " = ";
  writeOperand(I->getOperand(0));
}

void CWriter::visitGetElementPtrInst(GetElementPtrInst *I) {
  Out << "&";
  printIndexingExpr(I);
}

//===----------------------------------------------------------------------===//
//                       External Interface declaration
//===----------------------------------------------------------------------===//

void WriteToC(const Module *M, ostream &Out) {
  assert(M && "You can't write a null module!!");
  SlotCalculator SlotTable(M, false);
  CWriter W(Out, SlotTable, M);
  W.write((Module*)M);
  Out.flush();
}