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sketch expr_inverter approach for eliminating unconstrained regex containment.

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Nikolaj Bjorner 2025-01-07 16:53:28 -08:00
parent c7dfb619a2
commit 2dd4faf598
3 changed files with 134 additions and 27 deletions
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46
src/ast/converters/expr_inverter.cpp
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@ -881,36 +881,28 @@ public:
}
return false;
case OP_SEQ_IN_RE:
if (uncnstr(args[0]) && seq.re.is_ground(args[1])) {
if (uncnstr(args[0]) && seq.re.is_ground(args[1]) && seq.is_string(args[0]->get_sort())) {
#if 0
//
// requires auxiliary functions
// is_empty
// find_member
expr* r = args[1];
expr_ref not_r(seq.re.mk_complement(r), m);
lbool emp_r = rw.is_empty(r);
if (emp_r == l_undef)
// some_string_in_re.
// A preliminary implementation exists in sls_seq_plugin.cpp
// it should be moved to seq_rewriter and made agnostic to m_chars.
// maybe use backtracking for better covereage: when some_string_in_re
// fails it doesn't necessarily mean that the regex is empty.
//
zstring s1, s2;
expr* re = args[1];
expr_ref not_re(seq.re.mk_complement(re), m);
if (!rw.some_string_in_re(re, s1) || !rw.some_string_in_re(not_re, s2))
return false;
if (emp_r == l_true) {
r = m.mk_false();
return true;
}
lbool emp_not_r = rw.is_empty(not_r);
if (emp_not_r == l_true) {
r = m.mk_true();
return true;
}
if (emp_not_r == l_false) {
mk_fresh_uncnstr_var_for(f, r);
expr_ref witness1 = rw.find_member(r);
expr_ref witness2 = rw.find_member(not_r);
if (!witness1 || !witness2)
return false;
if (m_mc)
add_def(args[0], m.mk_ite(r, witness1, witness2));
return true;
}
mk_fresh_uncnstr_var_for(f, r);
expr_ref witness1 = expr_ref(seq.str.mk_string(s1), m);
expr_ref witness2 = expr_ref(seq.str.mk_string(s2), m);
if (m_mc)
add_def(args[0], m.mk_ite(r, witness1, witness2));
return true;
#endif
}
return false;