java_bytecode_convert_method.cpp

/*******************************************************************\

Module: JAVA Bytecode Language Conversion

Author: Daniel Kroening, kroening@kroening.com

\*******************************************************************/

#define DEBUG

#ifdef DEBUG
#include <iostream>
#endif

#include <util/std_expr.h>
#include <util/expanding_vector.h>
#include <util/string2int.h>
#include <util/prefix.h>
#include <util/arith_tools.h>
#include <util/ieee_float.h>
#include <util/expr_util.h>

#include "java_bytecode_convert_method.h"
#include "bytecode_info.h"
#include "java_types.h"

#include <limits>

namespace {
class patternt
{
public:
  explicit inline patternt(const char *_p):p(_p)
  {
  }

  // match with '?'
  friend bool operator==(const irep_idt &what, const patternt &pattern)
  {
    for(std::size_t i=0; i<what.size(); i++)
      if(pattern.p[i]==0)
        return false;
      else if(pattern.p[i]!='?' && pattern.p[i]!=what[i])
        return false;

    return pattern.p[what.size()]==0;
  }

protected:
  const char *p;
};

class java_bytecode_convert_methodt:public messaget
{
public:
  java_bytecode_convert_methodt(
    symbol_tablet &_symbol_table,
    message_handlert &_message_handler):
    messaget(_message_handler),
    symbol_table(_symbol_table)
  {
  }

  typedef java_bytecode_parse_treet::methodt methodt;
  typedef java_bytecode_parse_treet::instructiont instructiont;
  typedef methodt::instructionst instructionst;

  void operator()(const symbolt &class_symbol, const methodt &method)
  {
    convert(class_symbol, method);
  }

protected:
  symbol_tablet &symbol_table;

  irep_idt current_method;
  typet method_return_type;

  class variablet
  {
  public:
    symbol_exprt symbol_expr;
    size_t start_pc;
    size_t length;
  };

  typedef std::vector<variablet> variablest;
  expanding_vector<variablest> variables;

  bool method_has_this;

  typedef enum instruction_sizet
  {
    INST_INDEX = 2, INST_INDEX_CONST = 3
  } instruction_sizet;

  // return corresponding reference of variable
  variablet &find_variable_for_slot(
    size_t address,
    variablest &var_list,
    instruction_sizet inst_size)
  {
    for(variablet &var : var_list)
    {
      size_t start_pc = var.start_pc;
      size_t length = var.length;
      if (address + (size_t) inst_size >= start_pc && address < start_pc + length)
        return var;
    }
    // add unnamed local variable to end of list at this index
    // with scope from 0 to INT_MAX
    // as it is at the end of the vector, it will only be taken into account
    // if no other variable is valid
    size_t list_length = var_list.size();
    var_list.resize(list_length + 1);
    var_list[list_length].start_pc = 0;
    var_list[list_length].length = std::numeric_limits<size_t>::max();
    return var_list[list_length];
  }

  // JVM local variables
  const exprt variable(const exprt &arg, char type_char, size_t address, instruction_sizet inst_size)
  {
    irep_idt number=to_constant_expr(arg).get_value();

    std::size_t number_int=safe_string2size_t(id2string(number));
    typet t=java_type_from_char(type_char);
    variablest &var_list = variables[number_int];

    // search variable in list for correct frame / address if necessary
    variablet &var =
      find_variable_for_slot(address, var_list, inst_size);

    if(var.symbol_expr.get_identifier().empty())
    {
      // an un-named local variable
      irep_idt base_name="anonlocal::"+id2string(number)+type_char;
      irep_idt identifier=id2string(current_method)+"::"+id2string(base_name);

      symbol_exprt result(identifier, t);
      result.set(ID_C_base_name, base_name);

      return result;
    }
    else
    {
      exprt result=var.symbol_expr;
      if(t!=result.type()) result=typecast_exprt(result, t);
      return result;
    }
  }

  // temporary variables
  std::list<symbol_exprt> tmp_vars;

  symbol_exprt tmp_variable(const std::string &prefix, const typet &type)
  {
    irep_idt base_name=prefix+"_tmp"+std::to_string(tmp_vars.size());
    irep_idt identifier=id2string(current_method)+"::"+id2string(base_name);

    auxiliary_symbolt tmp_symbol;
    tmp_symbol.base_name=base_name;
    tmp_symbol.is_static_lifetime=false;
    tmp_symbol.mode=ID_java;
    tmp_symbol.name=identifier;
    tmp_symbol.type=type;
    symbol_table.add(tmp_symbol);

    symbol_exprt result(identifier, type);
    result.set(ID_C_base_name, base_name);
    tmp_vars.push_back(result);

    return result;
  }

  // JVM program locations
  irep_idt label(const irep_idt &address)
  {
    return "pc"+id2string(address);
  }

  // JVM Stack
  typedef std::vector<exprt> stackt;
  stackt stack;

  exprt::operandst pop(std::size_t n)
  {
    if(stack.size()<n)
    {
      error() << "malformed bytecode (pop too high)" << eom;
      throw 0;
    }

    exprt::operandst operands;
    operands.resize(n);
    for(std::size_t i=0; i<n; i++)
      operands[i]=stack[stack.size()-n+i];

    stack.resize(stack.size()-n);
    return operands;
  }

  void push(const exprt::operandst &o)
  {
    stack.resize(stack.size()+o.size());

    for(std::size_t i=0; i<o.size(); i++)
      stack[stack.size()-o.size()+i]=o[i];
  }

  // conversion
  void convert(const symbolt &class_symbol, const methodt &);
  void convert(const instructiont &);

  codet convert_instructions(
    const instructionst &, const code_typet &);

  const bytecode_infot &get_bytecode_info(const irep_idt &statement);
};
}

namespace {

const size_t SLOTS_PER_INTEGER(1u);
const size_t INTEGER_WIDTH(64u);
size_t count_slots(const size_t value, const code_typet::parametert &param)
{
  const std::size_t width(param.type().get_unsigned_int(ID_width));
  return value + SLOTS_PER_INTEGER + width / INTEGER_WIDTH;
}

size_t get_variable_slots(const code_typet::parametert &param)
{
  return count_slots(0, param);
}

bool is_constructor(const class_typet::methodt &method)
{
  const std::string &name(id2string(method.get_name()));
  const std::string::size_type &npos(std::string::npos);
  return npos != name.find("<init>") || npos != name.find("<clinit>");
}

void cast_if_necessary(binary_relation_exprt &condition)
{
  exprt &lhs(condition.lhs());
  exprt &rhs(condition.rhs());
  const typet &lhs_type(lhs.type());
  if(lhs_type == rhs.type()) return;
  rhs = typecast_exprt(rhs, lhs_type);
}
}

/*******************************************************************\

Function: java_bytecode_convert_methodt::convert

  Inputs:

 Outputs:

 Purpose:

\*******************************************************************/

void java_bytecode_convert_methodt::convert(
  const symbolt &class_symbol,
  const methodt &m)
{
  //const class_typet &class_type=to_class_type(class_symbol.type);

  typet member_type=java_type_from_string(m.signature);

  assert(member_type.id()==ID_code);

  const irep_idt method_identifier=
    id2string(class_symbol.name)+"."+id2string(m.name)+":"+m.signature;

  code_typet &code_type=to_code_type(member_type);
  method_return_type=code_type.return_type();
  code_typet::parameterst &parameters=code_type.parameters();

  // do we need to add 'this' as a parameter?
  if(!m.is_static)
  {
    code_typet::parametert this_p;
    const reference_typet object_ref_type(
      symbol_typet(class_symbol.name));
    this_p.type()=object_ref_type;
    this_p.set_this();
    parameters.insert(parameters.begin(), this_p);
  }

  variables.clear();

  // Do the parameters and locals in the variable table, which is available when
  // compiled with -g or for methods with many local variables in the latter
  // case, different variables can have the same index, depending on the
  // context.
  //
  // to calculate which variable to use, one uses the address of the instruction
  // that uses the variable, the size of the instruction and the start_pc /
  // length values in the local variable table
  for(const auto & v : m.local_variable_table)
  {
    typet t=java_type_from_string(v.signature);
    std::ostringstream id_oss;
    id_oss << method_identifier << "::" << v.start_pc << "::" << v.name;
    irep_idt identifier(id_oss.str());
    symbol_exprt result(identifier, t);
    result.set(ID_C_base_name, v.name);
    size_t number_index_entries = variables[v.index].size();
    variables[v.index].resize(number_index_entries + 1);
    variables[v.index][number_index_entries].symbol_expr = result;
    variables[v.index][number_index_entries].start_pc = v.start_pc;
    variables[v.index][number_index_entries].length = v.length;
  }

  // set up variables array
  for(std::size_t i=0, param_index=0;
      i < parameters.size(); ++i)
  {
    variables[param_index].resize(1);
    param_index+=get_variable_slots(parameters[i]);
  }

  // assign names to parameters
  for(std::size_t i=0, param_index=0;
      i < parameters.size(); ++i)
  {
    irep_idt base_name, identifier;

    if(i==0 && parameters[i].get_this())
    {
      base_name="this";
      identifier=id2string(method_identifier)+"::"+id2string(base_name);
      parameters[i].set_base_name(base_name);
      parameters[i].set_identifier(identifier);
    }
    else
    {
      // in the variable table?
      base_name=variables[param_index][0].symbol_expr.get(ID_C_base_name);
      identifier=variables[param_index][0].symbol_expr.get(ID_identifier);

      if(base_name.empty())
      {
        const typet &type=parameters[i].type();
        char suffix=java_char_from_type(type);
        base_name="arg"+std::to_string(param_index)+suffix;
        identifier=id2string(method_identifier)+"::"+id2string(base_name);
      }

      parameters[i].set_base_name(base_name);
      parameters[i].set_identifier(identifier);
    }

    // add to symbol table
    parameter_symbolt parameter_symbol;
    parameter_symbol.base_name=base_name;
    parameter_symbol.mode=ID_java;
    parameter_symbol.name=identifier;
    parameter_symbol.type=parameters[i].type();
    symbol_table.add(parameter_symbol);

    // add as a JVM variable
    std::size_t slots=get_variable_slots(parameters[i]);
    variables[param_index][0].symbol_expr=parameter_symbol.symbol_expr();
    variables[param_index][0].start_pc=0;
    variables[param_index][0].length = std::numeric_limits<size_t>::max();
    param_index+=slots;
  }

  const bool is_virtual=!m.is_static && !m.is_final;

  #if 0
  class_type.methods().push_back(class_typet::methodt());
  class_typet::methodt &method=class_type.methods().back();
  #else
  class_typet::methodt method;
  #endif

  method.set_base_name(m.base_name);
  method.set_name(method_identifier);

  method.set(ID_abstract, m.is_abstract);
  method.set(ID_is_virtual, is_virtual);

  if(is_constructor(method))
    method.set(ID_constructor, true);

  method.type()=member_type;

  // we add the symbol for the method

  symbolt method_symbol;

  method_symbol.name=method.get_name();
  method_symbol.base_name=method.get_base_name();
  method_symbol.mode=ID_java;
  method_symbol.name=method.get_name();
  method_symbol.base_name=method.get_base_name();

  if(method.get_base_name()=="<init>")
    method_symbol.pretty_name=id2string(class_symbol.pretty_name)+"."+
                              id2string(class_symbol.base_name)+"()";
  else
    method_symbol.pretty_name=id2string(class_symbol.pretty_name)+"."+
                              id2string(method.get_base_name())+"()";

  method_symbol.type=member_type;
  current_method=method_symbol.name;
  method_has_this=code_type.has_this();

  tmp_vars.clear();
  method_symbol.value=convert_instructions(m.instructions, code_type);

  // do we have the method symbol already?
  const auto s_it=symbol_table.symbols.find(method.get_name());
  if(s_it!=symbol_table.symbols.end())
    symbol_table.symbols.erase(s_it); // erase, we stubbed it

  symbol_table.add(method_symbol);
}

/*******************************************************************\

Function: java_bytecode_convert_methodt::get_bytecode_info

  Inputs:

 Outputs:

 Purpose:

\*******************************************************************/

const bytecode_infot &java_bytecode_convert_methodt::get_bytecode_info(
  const irep_idt &statement)
{
  for(const bytecode_infot *p=bytecode_info; p->mnemonic!=0; p++)
    if(statement==p->mnemonic) return *p;

  error() << "failed to find bytecode mnemonic `"
          << statement << '\'' << eom;
  throw 0;
}

namespace {

irep_idt get_if_cmp_operator(const irep_idt &stmt)
{
  if(stmt == patternt("if_?cmplt")) return ID_lt;
  if(stmt == patternt("if_?cmple")) return ID_le;
  if(stmt == patternt("if_?cmpgt")) return ID_gt;
  if(stmt == patternt("if_?cmpge")) return ID_ge;
  if(stmt == patternt("if_?cmpeq")) return ID_equal;
  if(stmt == patternt("if_?cmpne")) return ID_notequal;

  throw "Unhandled java comparison instruction";
}

constant_exprt as_number(const mp_integer value, const typet &type)
{
  const std::size_t java_int_width(type.get_unsigned_int(ID_width));
  const std::string significant_bits(integer2string(value, 2));
  std::string binary_width(java_int_width - significant_bits.length(), '0');
  return constant_exprt(binary_width += significant_bits, type);
}

member_exprt to_member(const exprt &pointer, const exprt &fieldref)
{
  symbol_typet class_type(fieldref.get(ID_class));

  exprt pointer2=
    typecast_exprt(pointer, pointer_typet(class_type));

  const dereference_exprt obj_deref(pointer2, class_type);

  return member_exprt(
    obj_deref, fieldref.get(ID_component_name), fieldref.type());
}
}

/*******************************************************************\

Function: java_bytecode_convert_methodt::convert_instructions

  Inputs:

 Outputs:

 Purpose:

\*******************************************************************/

static unsigned get_bytecode_type_width(const typet& ty)
{
  if(ty.id()==ID_pointer)
    return 32;
  return ty.get_unsigned_int(ID_width);
}

codet java_bytecode_convert_methodt::convert_instructions(
  const instructionst &instructions,
  const code_typet &method_type)
{
  // Run a worklist algorithm, assuming that the bytecode has not
  // been tampered with. See "Leroy, X. (2003). Java bytecode
  // verification: algorithms and formalizations. Journal of Automated
  // Reasoning, 30(3-4), 235-269." for a more complete treatment.

  // first pass: get targets and map addresses to instructions

  struct converted_instructiont
  {
    converted_instructiont(
      const instructionst::const_iterator &it,
      const codet &_code):source(it), code(_code), done(false)
    {
    }

    instructionst::const_iterator source;
    std::list<unsigned> successors;
    std::set<unsigned> predecessors;
    codet code;
    stackt stack;
    bool done;
  };

  typedef std::map<unsigned, converted_instructiont> address_mapt;
  address_mapt address_map;
  std::set<unsigned> targets;

  for(instructionst::const_iterator
      i_it=instructions.begin();
      i_it!=instructions.end();
      i_it++)
  {
    std::pair<address_mapt::iterator, bool> a_entry=
      address_map.insert(std::make_pair(
          i_it->address,
          converted_instructiont(i_it, code_skipt())));
    assert(a_entry.second);
    // addresses are strictly increasing, hence we must have inserted
    // a new maximal key
    assert(a_entry.first==--address_map.end());

    if(i_it->statement!="goto" &&
       i_it->statement!="return" &&
       !(i_it->statement==patternt("?return")) &&
       i_it->statement!="athrow" &&
       i_it->statement!="jsr" &&
       i_it->statement!="jsr_w" &&
       i_it->statement!="ret")
    {
      instructionst::const_iterator next=i_it;
      if(++next!=instructions.end())
        a_entry.first->second.successors.push_back(next->address);
    }

    if(i_it->statement=="goto" ||
       i_it->statement==patternt("if_?cmp??") ||
       i_it->statement==patternt("if??") ||
       i_it->statement=="ifnonnull" ||
       i_it->statement=="ifnull" ||
       i_it->statement=="jsr" ||
       i_it->statement=="jsr_w")
    {
      assert(!i_it->args.empty());

      const unsigned target=safe_string2unsigned(
        id2string(to_constant_expr(i_it->args[0]).get_value()));
      targets.insert(target);

      a_entry.first->second.successors.push_back(target);
    }
    else if(i_it->statement=="tableswitch" ||
            i_it->statement=="lookupswitch")
    {
      bool is_label=true;
      for(instructiont::argst::const_iterator
          a_it=i_it->args.begin();
          a_it!=i_it->args.end();
          a_it++, is_label=!is_label)
      {
        if(is_label)
        {
          const unsigned target=safe_string2unsigned(
            id2string(to_constant_expr(*a_it).get_value()));
          targets.insert(target);
          a_entry.first->second.successors.push_back(target);
        }
      }
    }
  }

  for(address_mapt::iterator
      it=address_map.begin();
      it!=address_map.end();
      ++it)
  {
    for(unsigned s : it->second.successors)
    {
      address_mapt::iterator a_it=address_map.find(s);
      assert(a_it!=address_map.end());

      a_it->second.predecessors.insert(it->first);
    }
  }

  std::set<unsigned> working_set;
  if(!instructions.empty())
    working_set.insert(instructions.front().address);

  while(!working_set.empty())
  {
    std::set<unsigned>::iterator cur=working_set.begin();
    address_mapt::iterator a_it=address_map.find(*cur);
    assert(a_it!=address_map.end());
    working_set.erase(cur);

    if(a_it->second.done) continue;
    working_set.insert(a_it->second.successors.begin(),
                       a_it->second.successors.end());

    instructionst::const_iterator i_it=a_it->second.source;
    stack.swap(a_it->second.stack);
    a_it->second.stack.clear();
    codet &c=a_it->second.code;

    assert(stack.empty() ||
           a_it->second.predecessors.size()<=1 ||
           has_prefix(stack.front().get_string(ID_C_base_name),
                      "$stack"));

    irep_idt statement=i_it->statement;
    exprt arg0=i_it->args.size()>=1?i_it->args[0]:nil_exprt();
    exprt arg1=i_it->args.size()>=2?i_it->args[1]:nil_exprt();

    const bytecode_infot &bytecode_info=get_bytecode_info(statement);

    // deal with _idx suffixes
    if(statement.size()>=2 &&
       statement[statement.size()-2]=='_' &&
       isdigit(statement[statement.size()-1]))
    {
      arg0=constant_exprt(
        std::string(id2string(statement), statement.size()-1, 1),
        integer_typet());
      statement=std::string(id2string(statement), 0, statement.size()-2);
    }

    exprt::operandst op=pop(bytecode_info.pop);
    exprt::operandst results;
    results.resize(bytecode_info.push, nil_exprt());

    if(statement=="aconst_null")
    {
      assert(results.size()==1);
      results[0]=gen_zero(java_reference_type(void_typet()));
    }
    else if(statement=="athrow")
    {
      assert(op.size()==1 && results.size()==1);
      side_effect_expr_throwt throw_expr;
      throw_expr.add_source_location()=i_it->source_location;
      throw_expr.copy_to_operands(op[0]);
      c=code_expressiont(throw_expr);
      results[0]=op[0];
    }
    else if(statement=="checkcast")
    {
      // checkcast throws an exception in case a cast of object
      // on stack to given type fails.
      // The stack isn't modified.
      assert(op.size()==1 && results.size()==1);
      results[0]=op[0];
    }
    else if(statement=="invokedynamic")
    {
      // not used in Java
      code_typet &code_type=to_code_type(arg0.type());
      const code_typet::parameterst &parameters(code_type.parameters());

      pop(parameters.size());

      const typet &return_type=code_type.return_type();

      if(return_type.id()!=ID_empty)
      {
        results.resize(1);
        results[0]=nil_exprt();
      }
    }
    else if(statement=="invokeinterface" ||
            statement=="invokespecial" ||
            statement=="invokevirtual" ||
            statement=="invokestatic")
    {
      const bool use_this(statement != "invokestatic");
      const bool is_virtual(
        statement == "invokevirtual" || statement == "invokeinterface");

      code_typet &code_type=to_code_type(arg0.type());
      code_typet::parameterst &parameters(code_type.parameters());

      if(use_this)
      {
        if(parameters.empty() || !parameters[0].get_this())
        {
          const empty_typet empty;
          pointer_typet object_ref_type(empty);
          code_typet::parametert this_p(object_ref_type);
          this_p.set_this();
          this_p.set_base_name("this");
          parameters.insert(parameters.begin(), this_p);
        }
      }

      code_function_callt call;
      call.add_source_location()=i_it->source_location;
      call.arguments() = pop(parameters.size());

      // double-check a bit
      if(use_this)
      {
        const exprt &this_arg=call.arguments().front();
        assert(this_arg.type().id()==ID_pointer);
      }

      // do some type adjustment for the arguments,
      // as Java promotes arguments

      for(std::size_t i=0; i<parameters.size(); i++)
      {
        const typet &type=parameters[i].type();
        if(type==java_boolean_type() ||
           type==java_char_type() ||
           type==java_byte_type() ||
           type==java_short_type())
        {
          assert(i<call.arguments().size());
          call.arguments()[i].make_typecast(type);
        }
      }

      // do some type adjustment for return values

      const typet &return_type=code_type.return_type();

      if(return_type.id()!=ID_empty)
      {
        // return types are promoted in Java
        call.lhs()=tmp_variable("return", return_type);
        exprt promoted=java_bytecode_promotion(call.lhs());
        results.resize(1);
        results[0]=promoted;
      }

      assert(arg0.id()==ID_virtual_function);

      // does the function symbol exist?
      irep_idt id=arg0.get(ID_identifier);
      if(symbol_table.symbols.find(id)==symbol_table.symbols.end())
      {
        // no, create stub
        symbolt symbol;
        symbol.name=id;
        symbol.base_name=arg0.get(ID_C_base_name);
        symbol.type=arg0.type();
        symbol.value.make_nil();
        symbol.mode=ID_java;
        symbol_table.add(symbol);
      }

      if(is_virtual)
      {
        // dynamic binding
        assert(use_this);
        assert(!call.arguments().empty());
        call.function()=arg0;
      }
      else
      {
        // static binding
        call.function()=symbol_exprt(arg0.get(ID_identifier), arg0.type());
      }

      call.function().add_source_location()=i_it->source_location;
      c = call;
    }
    else if(statement=="return")
    {
      assert(op.empty() && results.empty());
      c=code_returnt();
    }
    else if(statement==patternt("?return"))
    {
      // Return types are promoted in java, so this might need
      // conversion.
      assert(op.size()==1 && results.empty());
      exprt r=op[0];
      if(r.type()!=method_return_type) r=typecast_exprt(r, method_return_type);
      c=code_returnt(r);
    }
    else if(statement==patternt("?astore"))
    {
      assert(op.size()==3 && results.empty());

      char type_char=statement[0];

      exprt pointer=
        typecast_exprt(op[0], java_array_type(type_char));

      const dereference_exprt deref(pointer, pointer.type().subtype());

      const member_exprt data_ptr(
        deref, "data", pointer_typet(java_type_from_char(type_char)));

      plus_exprt data_plus_offset(data_ptr, op[1], data_ptr.type());
      typet element_type=data_ptr.type().subtype();
      const dereference_exprt element(data_plus_offset, element_type);

      c=code_assignt(element, op[2]);
    }
    else if(statement==patternt("?store"))
    {
      // store value into some local variable
      assert(op.size()==1 && results.empty());

      exprt var=variable(arg0, statement[0], i_it->address, INST_INDEX);

      const bool is_array('a' == statement[0]);

      if(is_array)
        var.type()=op[0].type();

      c=code_assignt(var, op[0]);
    }
    else if(statement==patternt("?aload"))
    {
      assert(op.size() == 2 && results.size() == 1);

      char type_char=statement[0];

      exprt pointer=
        typecast_exprt(op[0], java_array_type(type_char));

      const dereference_exprt deref(pointer, pointer.type().subtype());

      const member_exprt data_ptr(
        deref, "data", pointer_typet(java_type_from_char(type_char)));

      plus_exprt data_plus_offset(data_ptr, op[1], data_ptr.type());
      typet element_type=data_ptr.type().subtype();
      dereference_exprt element(data_plus_offset, element_type);

      results[0]=java_bytecode_promotion(element);
    }
    else if(statement==patternt("?load"))
    {
      // load a value from a local variable
      results[0]=variable(arg0, statement[0], i_it->address, INST_INDEX);
    }
    else if(statement=="ldc" || statement=="ldc_w" ||
            statement=="ldc2" || statement=="ldc2_w")
    {
      assert(op.empty() && results.size()==1);

      // 1) Pushing a String causes a reference to a java.lang.String object
      // to be constructed and pushed onto the operand stack.

      // 2) Pushing an int or a float causes a primitive value to be pushed
      // onto the stack.

      // 3) Pushing a Class constant causes a reference to a java.lang.Class
      // to be pushed onto the operand stack

      if(arg0.id()==ID_java_string_literal)
      {
        // these need to be references to java.lang.String
        results[0]=arg0;
        symbol_typet string_type("java::java.lang.String");
        results[0].type()=pointer_typet(string_type);
      }
      else if(arg0.id()==ID_type)
      {
        irep_idt class_id=arg0.type().get(ID_identifier);
        symbol_typet java_lang_Class("java::java.lang.Class");
        symbol_exprt symbol_expr(id2string(class_id)+"@class_model", java_lang_Class);
        address_of_exprt address_of_expr(symbol_expr);
        results[0]=address_of_expr;
      }
      else if(arg0.id()==ID_constant)
      {
        results[0]=arg0;
      }
      else
      {
        error() << "unexpected ldc argument" << eom;
        throw 0;
      }

    }
    else if(statement=="goto" || statement=="goto_w")
    {
      assert(op.empty() && results.empty());
      irep_idt number=to_constant_expr(arg0).get_value();
      code_gotot code_goto(label(number));
      c=code_goto;
    }
    else if(statement=="iconst_m1")
    {
      assert(results.size()==1);
      results[0]=from_integer(-1, java_int_type());
    }
    else if(statement==patternt("?const"))
    {
      assert(results.size() == 1);

      const char type_char=statement[0];
      const bool is_double('d' == type_char);
      const bool is_float('f' == type_char);

      if(is_double || is_float)
      {
        const ieee_float_spect spec(
            is_float ?
                ieee_float_spect::single_precision() :
                ieee_float_spect::double_precision());

        ieee_floatt value(spec);
        const typet &arg_type(arg0.type());
        if(ID_integer == arg_type.id())
          value.from_integer(arg0.get_int(ID_value));
        else
          value.from_expr(to_constant_expr(arg0));

        results[0] = value.to_expr();
      }
      else
      {
        const unsigned int value(arg0.get_unsigned_int(ID_value));
        const typet type=java_type_from_char(statement[0]);
        results[0] = as_number(value, type);
      }
    }
    else if(statement==patternt("?ipush"))
    {
      assert(results.size()==1);
      results[0]=typecast_exprt(arg0, java_int_type());
    }
    else if(statement==patternt("if_?cmp??"))
    {
      irep_idt number=to_constant_expr(arg0).get_value();
      assert(op.size()==2 && results.empty());

      code_ifthenelset code_branch;
      const irep_idt cmp_op=get_if_cmp_operator(statement);

      binary_relation_exprt condition(op[0], cmp_op, op[1]);

      cast_if_necessary(condition);
      code_branch.cond()=condition;
      code_branch.then_case()=code_gotot(label(number));
      code_branch.then_case().add_source_location()=i_it->source_location;
      code_branch.add_source_location()=i_it->source_location;

      c=code_branch;
    }
    else if(statement==patternt("if??"))
    {
      const irep_idt id=
        statement=="ifeq"?ID_equal:
        statement=="ifne"?ID_notequal:
        statement=="iflt"?ID_lt:
        statement=="ifge"?ID_ge:
        statement=="ifgt"?ID_gt:
        statement=="ifle"?ID_le:
        (assert(false), "");

      irep_idt number=to_constant_expr(arg0).get_value();
      assert(op.size()==1 && results.empty());

      code_ifthenelset code_branch;
      code_branch.cond()=binary_relation_exprt(op[0], id, gen_zero(op[0].type()));
      code_branch.cond().add_source_location()=i_it->source_location;
      code_branch.then_case()=code_gotot(label(number));
      code_branch.then_case().add_source_location()=i_it->source_location;
      code_branch.add_source_location()=i_it->source_location;

      c=code_branch;
    }
    else if(statement==patternt("ifnonnull"))
    {
      irep_idt number=to_constant_expr(arg0).get_value();
      assert(op.size()==1 && results.empty());
      code_ifthenelset code_branch;
      const typecast_exprt lhs(op[0], pointer_typet());
      const exprt rhs(gen_zero(lhs.type()));
      code_branch.cond()=binary_relation_exprt(lhs, ID_notequal, rhs);
      code_branch.then_case()=code_gotot(label(number));
      code_branch.then_case().add_source_location()=i_it->source_location;
      code_branch.add_source_location()=i_it->source_location;

      c=code_branch;
    }
    else if(statement==patternt("ifnull"))
    {
      assert(op.size()==1 && results.empty());
      irep_idt number=to_constant_expr(arg0).get_value();
      code_ifthenelset code_branch;
      const typecast_exprt lhs(op[0], pointer_typet(empty_typet()));
      const exprt rhs(gen_zero(lhs.type()));
      code_branch.cond()=binary_relation_exprt(lhs, ID_equal, rhs);
      code_branch.then_case()=code_gotot(label(number));
      code_branch.then_case().add_source_location()=i_it->source_location;
      code_branch.add_source_location()=i_it->source_location;

      c=code_branch;
    }
    else if(statement=="iinc")
    {
      code_assignt code_assign;
      code_assign.lhs()=variable(arg0, 'i', i_it->address, INST_INDEX_CONST);
      code_assign.rhs()=plus_exprt(
                                   variable(arg0, 'i', i_it->address, INST_INDEX_CONST),
                          typecast_exprt(arg1, java_int_type()));
      c=code_assign;
    }
    else if(statement==patternt("?xor"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=bitxor_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?or"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=bitor_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?and"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=bitand_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?shl"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=shl_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?shr"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=ashr_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?ushr"))
    {
      assert(op.size()==2 && results.size()==1);
      const typet type=java_type_from_char(statement[0]);

      const std::size_t width=type.get_size_t(ID_width);
      typet target=unsignedbv_typet(width);

      const typecast_exprt lhs(op[0], target);
      const typecast_exprt rhs(op[1], target);

      results[0]=lshr_exprt(lhs, rhs);
    }
    else if(statement==patternt("?add"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=plus_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?sub"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=minus_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?div"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=div_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?mul"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=mult_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?neg"))
    {
      assert(op.size()==1 && results.size()==1);
      results[0]=unary_minus_exprt(op[0], op[0].type());
    }
    else if(statement==patternt("?rem"))
    {
      assert(op.size()==2 && results.size()==1);
      if(statement=="frem" || statement=="drem")
        results[0]=rem_exprt(op[0], op[1]);
      else
        results[0]=mod_exprt(op[0], op[1]);
    }
    else if(statement==patternt("?cmp"))
    {
      assert(op.size() == 2 && results.size() == 1);

      // The integer result on the stack is:
      //  0 if op[0] equals op[1]
      // -1 if op[0] is less than op[1]
      //  1 if op[0] is greater than op[1]

      const typet t=java_int_type();

      results[0]=
        if_exprt(binary_relation_exprt(op[0], ID_equal, op[1]), gen_zero(t),
        if_exprt(binary_relation_exprt(op[0], ID_gt, op[1]), from_integer(1, t),
        from_integer(-1, t)));
    }
    else if(statement==patternt("?cmp?"))
    {
      assert(op.size()==2 && results.size()==1);
      const floatbv_typet type(to_floatbv_type(java_type_from_char(statement[0])));
      const ieee_float_spect spec(type);
      const ieee_floatt nan(ieee_floatt::NaN(spec));
      const constant_exprt nan_expr(nan.to_expr());
      const int nan_value(statement[4] == 'l' ? -1 : 1);
      const typet result_type(java_int_type());
      const exprt nan_result(from_integer(nan_value, result_type));

      // (value1 == NaN || value2 == NaN) ? nan_value : value1  < value2 ? -1 : value2 < value1  1 ? 1 : 0;
      // (value1 == NaN || value2 == NaN) ? nan_value : value1 == value2 ? 0  : value1 < value2 -1 ? 1 : 0;

      results[0]=
        if_exprt(or_exprt(ieee_float_equal_exprt(nan_expr, op[0]), ieee_float_equal_exprt(nan_expr, op[1])), nan_result,
        if_exprt(ieee_float_equal_exprt(op[0], op[1]), gen_zero(result_type),
        if_exprt(binary_relation_exprt(op[0], ID_lt, op[1]), from_integer(-1, result_type), from_integer(1, result_type))));
    }
    else if(statement==patternt("?cmpl"))
    {
      assert(op.size()==2 && results.size()==1);
      results[0]=binary_relation_exprt(op[0], ID_lt, op[1]);
    }
    else if(statement=="dup")
    {
      assert(op.size()==1 && results.size()==2);
      results[0]=results[1]=op[0];
    }
    else if(statement=="dup_x1")
    {
      assert(op.size()==2 && results.size()==3);
      results[0]=op[1];
      results[1]=op[0];
      results[2]=op[1];
    }
    else if(statement=="dup_x2")
    {
      assert(op.size()==3 && results.size()==4);
      results[0]=op[2];
      results[1]=op[0];
      results[2]=op[1];
      results[3]=op[2];
    }
    // dup2* behaviour depends on the size of the operands on the
    // stack
    else if(statement=="dup2")
    {
      assert(!stack.empty() && results.empty());

      if(get_bytecode_type_width(stack.back().type())==32)
        op=pop(2);
      else
        op=pop(1);

      results.insert(results.end(), op.begin(), op.end());
      results.insert(results.end(), op.begin(), op.end());
    }
    else if(statement=="dup2_x1")
    {
      assert(!stack.empty() && results.empty());

      if(get_bytecode_type_width(stack.back().type())==32)
        op=pop(3);
      else
        op=pop(2);

      results.insert(results.end(), op.begin()+1, op.end());
      results.insert(results.end(), op.begin(), op.end());
    }
    else if(statement=="dup2_x2")
    {
      assert(!stack.empty() && results.empty());

      if(get_bytecode_type_width(stack.back().type())==32)
        op=pop(2);
      else
        op=pop(1);

      assert(!stack.empty());
      exprt::operandst op2;

      if(get_bytecode_type_width(stack.back().type())==32)
        op2=pop(2);
      else
        op2=pop(1);

      results.insert(results.end(), op.begin(), op.end());
      results.insert(results.end(), op2.begin(), op2.end());
      results.insert(results.end(), op.begin(), op.end());
    }
    else if(statement=="dconst")
    {
      assert(op.empty() && results.size()==1);
    }
    else if(statement=="fconst")
    {
      assert(op.empty() && results.size()==1);
    }
    else if(statement=="getfield")
    {
      assert(op.size()==1 && results.size()==1);
      results[0]=java_bytecode_promotion(to_member(op[0], arg0));
    }
    else if(statement=="getstatic")
    {
      assert(op.empty() && results.size()==1);
      symbol_exprt symbol_expr(arg0.type());
      symbol_expr.set_identifier(arg0.get_string(ID_class)+"."+arg0.get_string(ID_component_name));
      results[0]=java_bytecode_promotion(symbol_expr);
    }
    else if(statement=="putfield")
    {
      assert(op.size()==2 && results.size()==0);
      c = code_assignt(to_member(op[0], arg0), op[1]);
    }
    else if(statement=="putstatic")
    {
      assert(op.size()==1 && results.empty());
      symbol_exprt symbol_expr(arg0.type());
      symbol_expr.set_identifier(arg0.get_string(ID_class)+"."+arg0.get_string(ID_component_name));
      c=code_assignt(symbol_expr, op[0]);
    }
    else if(statement==patternt("?2?")) // i2c etc.
    {
      assert(op.size()==1 && results.size()==1);
      results[0]=typecast_exprt(op[0], java_type_from_char(statement[2]));
    }
    else if(statement=="new")
    {
      // use temporary since the stack symbol might get duplicated
      assert(op.empty() && results.size()==1);
      const pointer_typet ref_type(arg0.type());
      exprt java_new_expr=side_effect_exprt(ID_java_new, ref_type);

      if(!i_it->source_location.get_line().empty())
        java_new_expr.add_source_location()=i_it->source_location;

      const exprt tmp=tmp_variable("new", ref_type);
      c=code_assignt(tmp, java_new_expr);
      results[0]=tmp;
    }
    else if(statement=="newarray" ||
            statement=="anewarray")
    {
      // the op is the array size
      assert(op.size()==1 && results.size()==1);

      char element_type;

      if(statement=="newarray")
      {
        irep_idt id=arg0.type().id();

        if(id==ID_bool)
          element_type='z';
        else if(id==ID_char)
          element_type='c';
        else if(id==ID_float)
          element_type='f';
        else if(id==ID_double)
          element_type='d';
        else if(id==ID_byte)
          element_type='b';
        else if(id==ID_short)
          element_type='s';
        else if(id==ID_int)
          element_type='i';
        else if(id==ID_long)
          element_type='j';
        else
          element_type='?';
      }
      else
        element_type='a';

      const pointer_typet ref_type=java_array_type(element_type);

      side_effect_exprt java_new_array(ID_java_new_array, ref_type);
      java_new_array.copy_to_operands(op[0]);

      if(!i_it->source_location.get_line().empty())
        java_new_array.add_source_location()=i_it->source_location;

      const exprt tmp=tmp_variable("newarray", ref_type);
      c=code_assignt(tmp, java_new_array);
      results[0]=tmp;
    }
    else if(statement=="multianewarray")
    {
      // The first argument is the type, the second argument is the dimension.
      // The size of each dimension is on the stack.
      irep_idt number=to_constant_expr(arg1).get_value();
      std::size_t dimension=safe_string2size_t(id2string(number));

      op=pop(dimension);
      assert(results.size()==1);

      // arg0.type()
      const pointer_typet ref_type=java_array_type('a');

      side_effect_exprt java_new_array(ID_java_new_array, ref_type);
      java_new_array.operands()=op;

      if(!i_it->source_location.get_line().empty())
        java_new_array.add_source_location()=i_it->source_location;

      const exprt tmp=tmp_variable("newarray", ref_type);
      c=code_assignt(tmp, java_new_array);
      results[0]=tmp;
    }
    else if(statement=="arraylength")
    {
      assert(op.size()==1 && results.size()==1);

      exprt pointer=
        typecast_exprt(op[0], java_array_type(statement[0]));

      const dereference_exprt array(pointer, pointer.type().subtype());
      assert(pointer.type().subtype().id()==ID_symbol);

      const member_exprt length(array, "length", java_int_type());

      results[0]=length;
    }
    else if(statement=="tableswitch" ||
            statement=="lookupswitch")
    {
      assert(op.size()==1 && results.size()==0);

      // we turn into switch-case
      code_switcht code_switch;
      code_switch.add_source_location()=i_it->source_location;
      code_switch.value()=op[0];
      code_blockt code_block;
      code_block.add_source_location()=i_it->source_location;

      bool is_label=true;
      for(instructiont::argst::const_iterator
          a_it=i_it->args.begin();
          a_it!=i_it->args.end();
          a_it++, is_label=!is_label)
      {
        if(is_label)
        {
          code_switch_caset code_case;
          code_case.add_source_location()=i_it->source_location;

          irep_idt number=to_constant_expr(*a_it).get_value();
          code_case.code()=code_gotot(label(number));
          code_case.code().add_source_location()=i_it->source_location;

          if(a_it==i_it->args.begin())
            code_case.set_default();
          else
          {
            instructiont::argst::const_iterator prev=a_it;
            prev--;
            code_case.case_op()=typecast_exprt(*prev, op[0].type());
            code_case.case_op().add_source_location()=i_it->source_location;
          }

          code_block.add(code_case);
        }
      }

      code_switch.body()=code_block;
      c=code_switch;
    }
    else if(statement=="pop" || statement=="pop2")
    {
      // these are skips
      c=code_skipt();

      // pop2 removes two single-word items from the stack (e.g. two
      // integers, or an integer and an object reference) or one
      // two-word item (i.e. a double or a long).
      // http://cs.au.dk/~mis/dOvs/jvmspec/ref-pop2.html
      if(statement=="pop2" &&
         get_bytecode_type_width(op[0].type())==32)
        pop(1);
    }
    else if(statement=="instanceof")
    {
      assert(op.size()==1 && results.size()==1);

      results[0]=
        binary_predicate_exprt(op[0], "java_instanceof", arg0);
    }
    else if(statement=="monitorenter")
    {
      // becomes a function call
      code_typet type;
      type.return_type()=void_typet();
      type.parameters().resize(1);
      type.parameters()[0].type()=reference_typet(void_typet());
      code_function_callt call;
      call.function()=symbol_exprt("java::monitorenter", type);
      call.lhs().make_nil();
      call.arguments().push_back(op[0]);
      call.add_source_location()=i_it->source_location;
      c=call;
    }
    else if(statement=="monitorexit")
    {
      // becomes a function call
      code_typet type;
      type.return_type()=void_typet();
      type.parameters().resize(1);
      type.parameters()[0].type()=reference_typet(void_typet());
      code_function_callt call;
      call.function()=symbol_exprt("java::monitorexit", type);
      call.lhs().make_nil();
      call.arguments().push_back(op[0]);
      call.add_source_location()=i_it->source_location;
      c=call;
    }
    else
    {
      c=codet(statement);
      c.operands()=op;
    }

    if(!i_it->source_location.get_line().empty())
      c.add_source_location()=i_it->source_location;

    push(results);

    a_it->second.done=true;
    for(std::list<unsigned>::iterator
        it=a_it->second.successors.begin();
        it!=a_it->second.successors.end();
        ++it)
    {
      address_mapt::iterator a_it2=address_map.find(*it);
      assert(a_it2!=address_map.end());

      if(!stack.empty() && a_it2->second.predecessors.size()>1)
      {
        // copy into temporaries
        code_blockt more_code;

        // introduce temporaries when successor is seen for the first
        // time
        if(a_it2->second.stack.empty())
        {
          for(stackt::iterator s_it=stack.begin();
              s_it!=stack.end();
              ++s_it)
          {
            symbol_exprt lhs=tmp_variable("$stack", s_it->type());
            code_assignt a(lhs, *s_it);
            more_code.copy_to_operands(a);

            s_it->swap(lhs);
          }
        }
        else
        {
          assert(a_it2->second.stack.size()==stack.size());
          stackt::const_iterator os_it=a_it2->second.stack.begin();
          for(stackt::iterator s_it=stack.begin();
              s_it!=stack.end();
              ++s_it)
          {
            assert(has_prefix(os_it->get_string(ID_C_base_name),
                              "$stack"));
            symbol_exprt lhs=to_symbol_expr(*os_it);
            code_assignt a(lhs, *s_it);
            more_code.copy_to_operands(a);

            s_it->swap(lhs);
            ++os_it;
          }
        }

        if(results.empty())
        {
          more_code.copy_to_operands(c);
          c.swap(more_code);
        }
        else
        {
          c.make_block();
          forall_operands(o_it, more_code)
            c.copy_to_operands(*o_it);
        }
      }

      a_it2->second.stack=stack;
    }
  }

  // TODO: add exception handlers from exception table
  // review successor computation of athrow!
  code_blockt code;

  // temporaries
  for(const auto & var : tmp_vars)
  {
    code.add(code_declt(var));
  }

  for(const auto & it : address_map)
  {
    const unsigned address=it.first;
    assert(it.first==it.second.source->address);
    const codet &c=it.second.code;

    if(targets.find(address)!=targets.end())
      code.add(code_labelt(label(std::to_string(address)), c));
    else if(c.get_statement()!=ID_skip)
      code.add(c);
  }

  return code;
}

/*******************************************************************\

Function: java_bytecode_convert_method

  Inputs:

 Outputs:

 Purpose:

\*******************************************************************/

void java_bytecode_convert_method(
  const symbolt &class_symbol,
  const java_bytecode_parse_treet::methodt &method,
  symbol_tablet &symbol_table,
  message_handlert &message_handler)
{
  java_bytecode_convert_methodt java_bytecode_convert_method(
    symbol_table, message_handler);

  java_bytecode_convert_method(class_symbol, method);
}