void havoc_loopst::get_modifies(
const loopt &loop,
modifiest &modifies)
{
for(loopt::const_iterator
i_it=loop.begin(); i_it!=loop.end(); i_it++)
{
const goto_programt::instructiont &instruction=**i_it;
if(instruction.is_assign())
{
const exprt &lhs=to_code_assign(instruction.code).lhs();
function_modifies.get_modifies_lhs(local_may_alias, *i_it, lhs, modifies);
}
else if(instruction.is_function_call())
{
const code_function_callt &code_function_call=
to_code_function_call(instruction.code);
const exprt &lhs=code_function_call.lhs();
// return value assignment
if(lhs.is_not_nil())
function_modifies.get_modifies_lhs(
local_may_alias, *i_it, lhs, modifies);
function_modifies(code_function_call.function(), modifies);
}
}
}
goto_programt::targett havoc_loopst::get_loop_exit(const loopt &loop)
{
assert(!loop.empty());
// find the last instruction in the loop
std::map<unsigned, goto_programt::targett> loop_map;
for(loopt::const_iterator l_it=loop.begin();
l_it!=loop.end();
l_it++)
loop_map[(*l_it)->location_number]=*l_it;
// get the one with the highest number
goto_programt::targett last=(--loop_map.end())->second;
return ++last;
}
void havoc_loopst::havoc_loop(
const goto_programt::targett loop_head,
const loopt &loop)
{
assert(!loop.empty());
// first find out what can get changed in the loop
modifiest modifies;
get_modifies(loop, modifies);
// build the havocking code
goto_programt havoc_code;
build_havoc_code(loop_head, modifies, havoc_code);
// Now havoc at the loop head. Use insert_swap to
// preserve jumps to loop head.
goto_function.body.insert_before_swap(loop_head, havoc_code);
// compute the loop exit
goto_programt::targett loop_exit=
get_loop_exit(loop);
// divert all gotos to the loop head to the loop exit
for(loopt::const_iterator
l_it=loop.begin(); l_it!=loop.end(); l_it++)
{
goto_programt::instructiont &instruction=**l_it;
if(instruction.is_goto())
{
for(goto_programt::targetst::iterator
t_it=instruction.targets.begin();
t_it!=instruction.targets.end();
t_it++)
{
if(*t_it==loop_head)
*t_it=loop_exit; // divert
}
}
}
// remove skips
remove_skip(goto_function.body);
}
void k_inductiont::get_modifies(
const loopt &loop,
modifiest &modifies)
{
for(loopt::const_iterator
i_it=loop.begin(); i_it!=loop.end(); i_it++)
{
const goto_programt::instructiont &instruction=**i_it;
if(instruction.is_assign())
{
const exprt &lhs=to_code_assign(instruction.code).lhs();
get_modifies_lhs(*i_it, lhs, modifies);
}
else if(instruction.is_function_call())
{
const exprt &lhs=to_code_function_call(instruction.code).lhs();
get_modifies_lhs(*i_it, lhs, modifies);
}
}
}