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Handle additional cases in rule_properties::check_accessor (#5821)

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* Handle additional cases in rule_properties::check_accessor

* Walk parents depth first in rule_properties::check_accessor
This commit is contained in:
Lorenzo Veronese 2022-03-07 16:49:59 +01:00 • committed by GitHub
parent 882fc31aea
commit e3568d5b47
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 72 additions and 21 deletions
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93
src/muz/base/rule_properties.cpp
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@ -210,19 +210,35 @@ bool rule_properties::check_accessor(app* n) {
SASSERT(m_dt.is_datatype(s));
if (m_dt.get_datatype_constructors(s)->size() <= 1)
return true;
func_decl* f = n->get_decl();
func_decl * c = m_dt.get_accessor_constructor(f);
func_decl* c = m_dt.get_accessor_constructor(f);
unsigned ut_size = m_rule->get_uninterpreted_tail_size();
unsigned t_size = m_rule->get_tail_size();
ptr_vector<func_decl> ctors;
// add recognizer constructor to ctors
auto add_recognizer = [&](expr* r) {
if (!m_dt.is_recognizer(r))
return;
if (n->get_arg(0) != to_app(r)->get_arg(0))
return;
auto* c2 = m_dt.get_recognizer_constructor(to_app(r)->get_decl());
if (c == c2)
return;
ctors.push_back(c2);
};
auto add_not_recognizer = [&](expr* r) {
if (m.is_not(r, r))
add_recognizer(r);
};
// t is a recognizer for n
auto is_recognizer_base = [&](expr* t) {
return m_dt.is_recognizer(t) &&
to_app(t)->get_arg(0) == n->get_arg(0) &&
m_dt.get_recognizer_constructor(to_app(t)->get_decl()) == c;
};
auto is_recognizer = [&](expr* t) {
if (m.is_and(t))
for (expr* arg : *to_app(t))
@ -231,43 +247,78 @@ bool rule_properties::check_accessor(app* n) {
return is_recognizer_base(t);
};
for (unsigned i = ut_size; i < t_size; ++i)
if (is_recognizer(m_rule->get_tail(i)))
for (unsigned i = ut_size; i < t_size; ++i) {
auto* tail = m_rule->get_tail(i);
if (is_recognizer(tail))
return true;
add_not_recognizer(tail);
}
// create parent use list for every sub-expression in the rule
obj_map<expr, ptr_vector<expr>> use_list;
for (unsigned i = ut_size; i < t_size; ++i) {
app* t = m_rule->get_tail(i);
use_list.insert_if_not_there(t, ptr_vector<expr>()).push_back(nullptr); // add marker for top-level expression.
for (expr* sub : subterms::all(expr_ref(t, m)))
for (expr* sub : subterms::all(expr_ref(t, m)))
if (is_app(sub))
for (expr* arg : *to_app(sub))
use_list.insert_if_not_there(arg, ptr_vector<expr>()).push_back(sub);
}
// walk parents of n to check that each path is guarded by a recognizer.
ptr_vector<expr> todo;
todo.push_back(n);
for (unsigned i = 0; i < todo.size(); ++i) {
expr* e = todo[i];
// walk parents of n depth first to check that each path is guarded by a recognizer.
vector<std::tuple<expr *, unsigned int, bool>> todo;
todo.push_back({n, ctors.size(), false});
while(!todo.empty()) {
auto [e, ctors_size, visited] = todo.back();
if (visited) {
todo.pop_back();
while (ctors.size() > ctors_size) ctors.pop_back();
continue;
}
std::get<2>(todo.back()) = true; // set visited
if (!use_list.contains(e))
return false;
for (expr* parent : use_list[e]) {
if (!parent)
return false; // top-level expressions are not guarded
if (is_recognizer(parent))
if (!parent) { // top-level expression
// check if n is an unguarded "else" branch
ptr_vector<func_decl> diff;
for (auto* dtc : *m_dt.get_datatype_constructors(s))
if (!ctors.contains(dtc))
diff.push_back(dtc);
// the only unguarded constructor for s is c:
// all the others are guarded and we are in an "else" branch so the accessor is safe
if (diff.size() == 1 && diff[0] == c)
continue;
return false; // the accessor is not safe
}
if (is_recognizer(parent))
continue;
if (m.is_ite(parent) && to_app(parent)->get_arg(1) == e && is_recognizer(to_app(parent)->get_arg(0)))
continue;
todo.push_back(parent);
expr *cnd, *thn, *els;
if (m.is_ite(parent, cnd, thn, els)) {
if (thn == e) {
if (is_recognizer(cnd) && els != e)
continue; // e is guarded
}
add_recognizer(cnd);
}
if (m.is_and(parent))
for (expr* arg : *to_app(parent))
add_not_recognizer(arg);
if (m.is_or(parent))
for (expr* arg : *to_app(parent)) {
add_recognizer(arg);
// if one branch is not(recognizer) then the accessor is safe
if (m.is_not(arg, arg) && is_recognizer(arg))
goto _continue;
}
todo.push_back({parent, ctors.size(), false});
_continue:;
}
}
return true;
}
void rule_properties::operator()(app* n) {