// Parse a logical and expression.
//
// logical-and-expr -> logical-and-expr '&&' equality-expr
// | equality-expr
Expr*
Parser::logical_and_expr()
{
Expr* e1 = equality_expr();
while (true) {
if (match_if(and_tok)) {
Expr* e2 = equality_expr();
e1 = on_and(e1, e2);
} else {
break;
}
}
return e1;
}
void arrayst::add_array_constraints(
const index_sett &index_set,
const array_equalityt &array_equality)
{
// add constraints x=y => x[i]=y[i]
for(index_sett::const_iterator
it=index_set.begin();
it!=index_set.end();
it++)
{
index_exprt index_expr1;
index_expr1.type()=ns.follow(array_equality.f1.type()).subtype();
index_expr1.array()=array_equality.f1;
index_expr1.index()=*it;
index_exprt index_expr2;
index_expr2.type()=ns.follow(array_equality.f2.type()).subtype();
index_expr2.array()=array_equality.f2;
index_expr2.index()=*it;
assert(index_expr1.type()==index_expr2.type());
equality_exprt equality_expr(index_expr1, index_expr2);
// add constraint
bvt bv;
bv.push_back(prop.lnot(array_equality.l));
bv.push_back(convert(equality_expr));
prop.lcnf(bv);
}
}
void goto_symext::replace_array_equal(exprt &expr)
{
if(expr.id()==ID_array_equal)
{
assert(expr.operands().size()==2);
// we expect two index expressions
process_array_expr(expr.op0());
process_array_expr(expr.op1());
// type checking
if(ns.follow(expr.op0().type())!=
ns.follow(expr.op1().type()))
expr=false_exprt();
else
{
equal_exprt equality_expr(expr.op0(), expr.op1());
expr.swap(equality_expr);
}
}
Forall_operands(it, expr)
replace_array_equal(*it);
}
bool simplify_exprt::simplify_index(exprt &expr)
{
bool result=true;
// extra arithmetic optimizations
const exprt &index=to_index_expr(expr).index();
const exprt &array=to_index_expr(expr).array();
if(index.id()==ID_div &&
index.operands().size()==2)
{
if(index.op0().id()==ID_mult &&
index.op0().operands().size()==2 &&
index.op0().op1()==index.op1())
{
exprt tmp=index.op0().op0();
expr.op1()=tmp;
result=false;
}
else if(index.op0().id()==ID_mult &&
index.op0().operands().size()==2 &&
index.op0().op0()==index.op1())
{
exprt tmp=index.op0().op1();
expr.op1()=tmp;
result=false;
}
}
if(array.id()==ID_lambda)
{
// simplify (lambda i: e)(x) to e[i/x]
const exprt &lambda_expr=array;
if(lambda_expr.operands().size()!=2)
return true;
if(expr.op1().type()==lambda_expr.op0().type())
{
exprt tmp=lambda_expr.op1();
replace_expr(lambda_expr.op0(), expr.op1(), tmp);
expr.swap(tmp);
return false;
}
}
else if(array.id()==ID_with)
{
// we have (a WITH [i:=e])[j]
const exprt &with_expr=array;
if(with_expr.operands().size()!=3)
return true;
if(with_expr.op1()==expr.op1())
{
// simplify (e with [i:=v])[i] to v
exprt tmp=with_expr.op2();
expr.swap(tmp);
return false;
}
else
{
// Turn (a with i:=x)[j] into (i==j)?x:a[j].
// watch out that the type of i and j might be different.
equal_exprt equality_expr(expr.op1(), with_expr.op1());
if(equality_expr.lhs().type()!=equality_expr.rhs().type())
equality_expr.rhs().make_typecast(equality_expr.lhs().type());
simplify_inequality(equality_expr);
index_exprt new_index_expr;
new_index_expr.type()=expr.type();
new_index_expr.array()=with_expr.op0();
new_index_expr.index()=expr.op1();
simplify_index(new_index_expr); // recursive call
if(equality_expr.is_true())
{
expr=with_expr.op2();
return false;
}
else if(equality_expr.is_false())
{
expr.swap(new_index_expr);
return false;
}
if_exprt if_expr(equality_expr, with_expr.op2(), new_index_expr);
simplify_if(if_expr);
expr.swap(if_expr);
return false;
}
}
else if(array.id()==ID_constant ||
array.id()==ID_array)
{
mp_integer i;
if(to_integer(expr.op1(), i))
{
}
else if(i<0 || i>=array.operands().size())
{
// out of bounds
}
else
{
// ok
exprt tmp=array.operands()[integer2size_t(i)];
expr.swap(tmp);
return false;
}
}
else if(array.id()==ID_string_constant)
{
mp_integer i;
const irep_idt &value=array.get(ID_value);
if(to_integer(expr.op1(), i))
{
}
else if(i<0 || i>value.size())
{
// out of bounds
}
else
{
// terminating zero?
char v=(i==value.size())?0:value[integer2size_t(i)];
exprt tmp=from_integer(v, expr.type());
expr.swap(tmp);
return false;
}
}
else if(array.id()==ID_array_of)
{
if(array.operands().size()==1)
{
exprt tmp=array.op0();
expr.swap(tmp);
return false;
}
}
else if(array.id()=="array-list")
{
// These are index/value pairs, alternating.
for(size_t i=0; i<array.operands().size()/2; i++)
{
exprt tmp_index=array.operands()[i*2];
tmp_index.make_typecast(index.type());
simplify(tmp_index);
if(tmp_index==index)
{
exprt tmp=array.operands()[i*2+1];
expr.swap(tmp);
return false;
}
}
}
else if(array.id()==ID_byte_extract_little_endian ||
array.id()==ID_byte_extract_big_endian)
{
const typet &array_type=ns.follow(array.type());
if(array_type.id()==ID_array)
{
// This rewrites byte_extract(s, o, array_type)[i]
// to byte_extract(s, o+offset, sub_type)
mp_integer sub_size=pointer_offset_size(array_type.subtype(), ns);
if(sub_size==-1)
return true;
// add offset to index
mult_exprt offset(from_integer(sub_size, array.op1().type()), index);
plus_exprt final_offset(array.op1(), offset);
simplify_node(final_offset);
exprt result(array.id(), expr.type());
result.copy_to_operands(array.op0(), final_offset);
expr.swap(result);
simplify_rec(expr);
return false;
}
}
else if(array.id()==ID_if)
{
const if_exprt &if_expr=to_if_expr(array);
exprt cond=if_expr.cond();
index_exprt idx_false=to_index_expr(expr);
idx_false.array()=if_expr.false_case();
to_index_expr(expr).array()=if_expr.true_case();
expr=if_exprt(cond, expr, idx_false, expr.type());
simplify_rec(expr);
return false;
}
return result;
}
void arrayst::add_array_constraints_with(
const index_sett &index_set,
const with_exprt &expr)
{
// we got x=(y with [i:=v])
// add constaint x[i]=v
const exprt &index=expr.where();
const exprt &value=expr.new_value();
{
index_exprt index_expr;
index_expr.type()=ns.follow(expr.type()).subtype();
index_expr.array()=expr;
index_expr.index()=index;
if(index_expr.type()!=value.type())
{
std::cout << expr.pretty() << std::endl;
assert(false);
}
set_to_true(equality_exprt(index_expr, value));
}
// use other array index applications for "else" case
// add constraint x[I]=y[I] for I!=i
for(index_sett::const_iterator
it=index_set.begin();
it!=index_set.end();
it++)
{
exprt other_index=*it;
if(other_index!=index)
{
// we first build the guard
if(other_index.type()!=index.type())
other_index.make_typecast(index.type());
literalt guard_lit=convert(equality_exprt(index, other_index));
if(guard_lit!=const_literal(true))
{
index_exprt index_expr1;
index_expr1.type()=ns.follow(expr.type()).subtype();
index_expr1.array()=expr;
index_expr1.index()=other_index;
index_exprt index_expr2;
index_expr2.type()=ns.follow(expr.type()).subtype();
index_expr2.array()=expr.op0();
index_expr2.index()=other_index;
assert(index_expr1.type()==index_expr2.type());
equality_exprt equality_expr(index_expr1, index_expr2);
literalt equality_lit=convert(equality_expr);
// add constraint
bvt bv;
bv.reserve(2);
bv.push_back(equality_lit);
bv.push_back(guard_lit);
prop.lcnf(bv);
}
}
}
}