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Handle additional cases in rule_properties::check_accessor (#5821)
* Handle additional cases in rule_properties::check_accessor * Walk parents depth first in rule_properties::check_accessor
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@ -210,19 +210,35 @@ bool rule_properties::check_accessor(app* n) {
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SASSERT(m_dt.is_datatype(s));
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if (m_dt.get_datatype_constructors(s)->size() <= 1)
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return true;
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func_decl* f = n->get_decl();
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func_decl * c = m_dt.get_accessor_constructor(f);
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func_decl* c = m_dt.get_accessor_constructor(f);
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unsigned ut_size = m_rule->get_uninterpreted_tail_size();
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unsigned t_size = m_rule->get_tail_size();
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ptr_vector<func_decl> ctors;
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// add recognizer constructor to ctors
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auto add_recognizer = [&](expr* r) {
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if (!m_dt.is_recognizer(r))
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return;
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if (n->get_arg(0) != to_app(r)->get_arg(0))
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return;
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auto* c2 = m_dt.get_recognizer_constructor(to_app(r)->get_decl());
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if (c == c2)
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return;
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ctors.push_back(c2);
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};
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auto add_not_recognizer = [&](expr* r) {
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if (m.is_not(r, r))
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add_recognizer(r);
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};
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// t is a recognizer for n
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auto is_recognizer_base = [&](expr* t) {
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return m_dt.is_recognizer(t) &&
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to_app(t)->get_arg(0) == n->get_arg(0) &&
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m_dt.get_recognizer_constructor(to_app(t)->get_decl()) == c;
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};
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auto is_recognizer = [&](expr* t) {
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if (m.is_and(t))
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for (expr* arg : *to_app(t))
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@ -231,43 +247,78 @@ bool rule_properties::check_accessor(app* n) {
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return is_recognizer_base(t);
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};
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for (unsigned i = ut_size; i < t_size; ++i)
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if (is_recognizer(m_rule->get_tail(i)))
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for (unsigned i = ut_size; i < t_size; ++i) {
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auto* tail = m_rule->get_tail(i);
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if (is_recognizer(tail))
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return true;
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add_not_recognizer(tail);
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}
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// create parent use list for every sub-expression in the rule
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obj_map<expr, ptr_vector<expr>> use_list;
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for (unsigned i = ut_size; i < t_size; ++i) {
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app* t = m_rule->get_tail(i);
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use_list.insert_if_not_there(t, ptr_vector<expr>()).push_back(nullptr); // add marker for top-level expression.
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for (expr* sub : subterms::all(expr_ref(t, m)))
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for (expr* sub : subterms::all(expr_ref(t, m)))
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if (is_app(sub))
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for (expr* arg : *to_app(sub))
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use_list.insert_if_not_there(arg, ptr_vector<expr>()).push_back(sub);
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}
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// walk parents of n to check that each path is guarded by a recognizer.
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ptr_vector<expr> todo;
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todo.push_back(n);
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for (unsigned i = 0; i < todo.size(); ++i) {
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expr* e = todo[i];
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// walk parents of n depth first to check that each path is guarded by a recognizer.
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vector<std::tuple<expr *, unsigned int, bool>> todo;
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todo.push_back({n, ctors.size(), false});
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while(!todo.empty()) {
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auto [e, ctors_size, visited] = todo.back();
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if (visited) {
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todo.pop_back();
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while (ctors.size() > ctors_size) ctors.pop_back();
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continue;
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}
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std::get<2>(todo.back()) = true; // set visited
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if (!use_list.contains(e))
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return false;
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for (expr* parent : use_list[e]) {
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if (!parent)
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return false; // top-level expressions are not guarded
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if (is_recognizer(parent))
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if (!parent) { // top-level expression
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// check if n is an unguarded "else" branch
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ptr_vector<func_decl> diff;
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for (auto* dtc : *m_dt.get_datatype_constructors(s))
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if (!ctors.contains(dtc))
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diff.push_back(dtc);
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// the only unguarded constructor for s is c:
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// all the others are guarded and we are in an "else" branch so the accessor is safe
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if (diff.size() == 1 && diff[0] == c)
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continue;
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return false; // the accessor is not safe
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}
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if (is_recognizer(parent))
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continue;
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if (m.is_ite(parent) && to_app(parent)->get_arg(1) == e && is_recognizer(to_app(parent)->get_arg(0)))
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continue;
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todo.push_back(parent);
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expr *cnd, *thn, *els;
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if (m.is_ite(parent, cnd, thn, els)) {
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if (thn == e) {
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if (is_recognizer(cnd) && els != e)
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continue; // e is guarded
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}
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add_recognizer(cnd);
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}
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if (m.is_and(parent))
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for (expr* arg : *to_app(parent))
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add_not_recognizer(arg);
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if (m.is_or(parent))
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for (expr* arg : *to_app(parent)) {
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add_recognizer(arg);
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// if one branch is not(recognizer) then the accessor is safe
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if (m.is_not(arg, arg) && is_recognizer(arg))
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goto _continue;
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}
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todo.push_back({parent, ctors.size(), false});
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_continue:;
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}
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}
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return true;
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}
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void rule_properties::operator()(app* n) {
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