dfcc_swap_and_wrap.cpp

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/*******************************************************************\
 
Module: Dynamic frame condition checking
 
Author: Remi Delmas, delmarsd@amazon.com
 
\*******************************************************************/
 
#include "dfcc_swap_and_wrap.h"
 
#include <goto-programs/remove_skip.h>
 
#include "dfcc_contract_handler.h"
#include "dfcc_instrument.h"
#include "dfcc_library.h"
#include "dfcc_utils.h"
 
dfcc_swap_and_wrapt::dfcc_swap_and_wrapt(
  goto_modelt &goto_model,
  message_handlert &message_handler,
  dfcc_libraryt &library,
  dfcc_instrumentt &instrument,
  dfcc_spec_functionst &spec_functions,
  dfcc_contract_handlert &contract_handler)
  : goto_model(goto_model),
    message_handler(message_handler),
    log(message_handler),
    library(library),
    instrument(instrument),
    spec_functions(spec_functions),
    contract_handler(contract_handler),
    ns(goto_model.symbol_table)
{
}
 
// static map
std::map<
  irep_idt,
  std::pair<irep_idt, std::pair<dfcc_contract_modet, loop_contract_configt>>>
  dfcc_swap_and_wrapt::cache;
 
void dfcc_swap_and_wrapt::swap_and_wrap(
  const dfcc_contract_modet contract_mode,
  const loop_contract_configt &loop_contract_config,
  const irep_idt &function_id,
  const irep_idt &contract_id,
  std::set<irep_idt> &function_pointer_contracts,
  bool allow_recursive_calls)
{
  auto pair = cache.insert(
    {function_id, {contract_id, {contract_mode, loop_contract_config}}});
  auto inserted = pair.second;
 
  if(!inserted)
  {
    irep_idt old_contract_id = pair.first->second.first;
    dfcc_contract_modet old_contract_mode = pair.first->second.second.first;
    loop_contract_configt old_loop_contract_config =
      pair.first->second.second.second;
 
    // different swap already performed, abort (should be unreachable)
    if(
      old_contract_id != contract_id || old_contract_mode != contract_mode ||
      old_loop_contract_config != loop_contract_config)
    {
      std::ostringstream err_msg;
      err_msg << "DFCC: multiple attempts to swap and wrap function '"
              << function_id << "':\n";
      err_msg << "- with '" << old_contract_id << "' in "
              << dfcc_contract_mode_to_string(old_contract_mode) << " "
              << old_loop_contract_config.to_string() << "\n";
      err_msg << "- with '" << contract_id << "' in "
              << dfcc_contract_mode_to_string(contract_mode) << " "
              << loop_contract_config.to_string() << "\n";
      throw invalid_input_exceptiont(err_msg.str());
    }
    // same swap already performed
    return;
  }
 
  // actually perform the translation
  switch(contract_mode)
  {
  case dfcc_contract_modet::CHECK:
  {
    check_contract(
      loop_contract_config,
      function_id,
      contract_id,
      function_pointer_contracts,
      allow_recursive_calls);
    break;
  }
  case dfcc_contract_modet::REPLACE:
  {
    replace_with_contract(function_id, contract_id, function_pointer_contracts);
    break;
  }
  }
}
 
void dfcc_swap_and_wrapt::get_swapped_functions(std::set<irep_idt> &dest) const
{
  for(const auto &it : dfcc_swap_and_wrapt::cache)
  {
    dest.insert(it.first);
  }
}

void dfcc_swap_and_wrapt::check_contract(
  const loop_contract_configt &loop_contract_config,
  const irep_idt &function_id,
  const irep_idt &contract_id,
  std::set<irep_idt> &function_pointer_contracts,
  bool allow_recursive_calls)
{
  // all code generation needs to run on functions with unmodified signatures
  const irep_idt &wrapper_id = function_id;
  const irep_idt wrapped_id =
    id2string(wrapper_id) + "_wrapped_for_contract_checking";
  dfcc_utilst::wrap_function(goto_model, wrapper_id, wrapped_id);
 
  // wrapper body
  goto_programt body;
 
  const auto &wrapper_symbol =
    dfcc_utilst::get_function_symbol(goto_model.symbol_table, wrapper_id);
 
  auto check_started = dfcc_utilst::create_static_symbol(
                         goto_model.symbol_table,
                         bool_typet(),
                         id2string(function_id),
                         "__contract_check_in_progress",
                         wrapper_symbol.location,
                         wrapper_symbol.mode,
                         wrapper_symbol.module,
                         false_exprt())
                         .symbol_expr();
 
  auto check_completed = dfcc_utilst::create_static_symbol(
                           goto_model.symbol_table,
                           bool_typet(),
                           id2string(function_id),
                           "__contract_checked_once",
                           wrapper_symbol.location,
                           wrapper_symbol.mode,
                           wrapper_symbol.module,
                           false_exprt())
                           .symbol_expr();
 
  auto check_started_goto = body.add(goto_programt::make_incomplete_goto(
    check_started, wrapper_symbol.location));
 
  // At most a single top level call to the checked function in any execution
 
  // Recursive calls within a contract check correspond to
  // `check_started && !check_completed` and are allowed.
 
  // Any other call occuring with `check_completed` true is forbidden.
  source_locationt sl(wrapper_symbol.location);
  sl.set_function(wrapper_symbol.name);
  sl.set_property_class("single_top_level_call");
  sl.set_comment(
    "Only a single top-level call to function " + id2string(function_id) +
    " when checking contract " + id2string(contract_id));
  body.add(goto_programt::make_assertion(not_exprt(check_completed), sl));
  body.add(goto_programt::make_assignment(
    check_started, true_exprt(), wrapper_symbol.location));
 
  const auto write_set_symbol = dfcc_utilst::create_new_parameter_symbol(
    goto_model.symbol_table,
    function_id,
    "__write_set_to_check",
    library.dfcc_type[dfcc_typet::CAR_SET_PTR]);
 
  contract_handler.add_contract_instructions(
    dfcc_contract_modet::CHECK,
    wrapper_id,
    wrapped_id,
    contract_id,
    write_set_symbol,
    body,
    function_pointer_contracts);
 
  body.add(goto_programt::make_assignment(
    check_completed, true_exprt(), wrapper_symbol.location));
  body.add(goto_programt::make_assignment(
    check_started, false_exprt(), wrapper_symbol.location));
 
  // unconditionally Jump to the end after the check
  auto goto_end_function =
    body.add(goto_programt::make_incomplete_goto(wrapper_symbol.location));
 
  // Jump to the replacement section if check already in progress
  auto contract_replacement_label =
    body.add(goto_programt::make_skip(wrapper_symbol.location));
  check_started_goto->complete_goto(contract_replacement_label);
 
  if(allow_recursive_calls)
  {
    contract_handler.add_contract_instructions(
      dfcc_contract_modet::REPLACE,
      wrapper_id,
      wrapped_id,
      contract_id,
      write_set_symbol,
      body,
      function_pointer_contracts);
  }
  else
  {
    source_locationt sl(wrapper_symbol.location);
    sl.set_function(wrapper_symbol.name);
    sl.set_property_class("no_recursive_call");
    sl.set_comment(
      "No recursive call to function " + id2string(function_id) +
      " when checking contract " + id2string(contract_id));
    body.add(goto_programt::make_assertion(false_exprt(), sl));
    body.add(
      goto_programt::make_assumption(false_exprt(), wrapper_symbol.location));
  }
 
  auto end_function_label =
    body.add(goto_programt::make_end_function(wrapper_symbol.location));
  goto_end_function->complete_goto(end_function_label);
 
  // write the body to the GOTO function
  goto_model.goto_functions.function_map.at(function_id).body.swap(body);
 
  // extend the signature of the wrapper function with the write set parameter
  dfcc_utilst::add_parameter(goto_model, write_set_symbol, function_id);
 
  goto_model.goto_functions.function_map.at(wrapper_id).make_hidden();
 
  // instrument the wrapped function
  instrument.instrument_wrapped_function(
    wrapped_id, wrapper_id, loop_contract_config, function_pointer_contracts);
 
  goto_model.goto_functions.update();
}
 
void dfcc_swap_and_wrapt::replace_with_contract(
  const irep_idt &function_id,
  const irep_idt &contract_id,
  std::set<irep_idt> &function_pointer_contracts)
{
  const irep_idt &wrapper_id = function_id;
  const irep_idt wrapped_id =
    id2string(function_id) + "_wrapped_for_replacement_with_contract";
  dfcc_utilst::wrap_function(goto_model, function_id, wrapped_id);
 
  const auto write_set_symbol = dfcc_utilst::create_new_parameter_symbol(
    goto_model.symbol_table,
    function_id,
    "__write_set_to_check",
    library.dfcc_type[dfcc_typet::CAR_SET_PTR]);
 
  goto_programt body;
 
  contract_handler.add_contract_instructions(
    dfcc_contract_modet::REPLACE,
    wrapper_id,
    wrapped_id,
    contract_id,
    write_set_symbol,
    body,
    function_pointer_contracts);
 
  body.add(goto_programt::make_end_function(
    dfcc_utilst::get_function_symbol(goto_model.symbol_table, wrapper_id)
      .location));
 
  goto_model.goto_functions.function_map.at(wrapper_id).make_hidden();
 
  // write the body to the GOTO function
  goto_model.goto_functions.function_map.at(function_id).body.swap(body);
 
  // extend the signature with the new write set parameter
  dfcc_utilst::add_parameter(goto_model, write_set_symbol, function_id);
}