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https://github.com/Z3Prover/z3
synced 2025-04-08 02:15:19 +00:00
throttel extract/ite rewriting to avoid perf-bug exposed in example from Lucas Cordeiro and Alessandro Trindade
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
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@ -779,11 +779,14 @@ br_status bv_rewriter::mk_extract(unsigned high, unsigned low, expr * arg, expr_
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}
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}
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if (m().is_ite(arg)) {
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result = m().mk_ite(to_app(arg)->get_arg(0),
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m_mk_extract(high, low, to_app(arg)->get_arg(1)),
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m_mk_extract(high, low, to_app(arg)->get_arg(2)));
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return BR_REWRITE2;
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expr* c = nullptr, *t = nullptr, *e = nullptr;
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if (m().is_ite(arg, c, t, e)) {
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if ((t->get_ref_count() == 1 && e->get_ref_count() == 1) ||
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(!m().is_ite(t) && !m().is_ite(e))) {
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//std::cout << "n-ite\n";
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result = m().mk_ite(c, m_mk_extract(high, low, t), m_mk_extract(high, low, e));
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return BR_REWRITE2;
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}
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}
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return BR_FAILED;
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@ -387,8 +387,9 @@ eautomaton* re2automaton::seq2aut(expr* e) {
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br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result) {
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SASSERT(f->get_family_id() == get_fid());
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br_status st = BR_FAILED;
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switch(f->get_decl_kind()) {
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case OP_SEQ_UNIT:
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SASSERT(num_args == 1);
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return mk_seq_unit(args[0], result);
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@ -448,7 +449,8 @@ br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * con
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return mk_seq_length(args[0], result);
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case OP_SEQ_EXTRACT:
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SASSERT(num_args == 3);
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return mk_seq_extract(args[0], args[1], args[2], result);
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st = mk_seq_extract(args[0], args[1], args[2], result);
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break;
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case OP_SEQ_CONTAINS:
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SASSERT(num_args == 2);
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return mk_seq_contains(args[0], args[1], result);
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@ -499,7 +501,8 @@ br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * con
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case _OP_STRING_STRIDOF:
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UNREACHABLE();
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}
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return BR_FAILED;
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TRACE("seq", tout << result << "\n";);
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return st;
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}
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/*
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@ -607,6 +610,7 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
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bool constantPos = m_autil.is_numeral(b, pos);
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bool constantLen = m_autil.is_numeral(c, len);
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// case 1: pos<0 or len<=0
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// rewrite to ""
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if ( (constantPos && pos.is_neg()) || (constantLen && !len.is_pos()) ) {
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@ -615,7 +619,7 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
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}
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// case 1.1: pos >= length(base)
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// rewrite to ""
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if (constantBase && constantPos && pos >= rational(s.length())) {
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if (constantPos && constantBase && pos >= rational(s.length())) {
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result = m_util.str.mk_empty(m().get_sort(a));
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return BR_DONE;
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}
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@ -623,52 +627,74 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
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constantPos &= pos.is_unsigned();
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constantLen &= len.is_unsigned();
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if (constantBase && constantPos && constantLen) {
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if (pos.get_unsigned() + len.get_unsigned() >= s.length()) {
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// case 2: pos+len goes past the end of the string
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unsigned _len = s.length() - pos.get_unsigned() + 1;
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result = m_util.str.mk_string(s.extract(pos.get_unsigned(), _len));
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} else {
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// case 3: pos+len still within string
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result = m_util.str.mk_string(s.extract(pos.get_unsigned(), len.get_unsigned()));
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}
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return BR_DONE;
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}
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if (constantPos && constantLen) {
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if (constantPos && constantLen && constantBase) {
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unsigned _pos = pos.get_unsigned();
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unsigned _len = len.get_unsigned();
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SASSERT(_len > 0);
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expr_ref_vector as(m()), bs(m());
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m_util.str.get_concat(a, as);
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if (as.empty()) {
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result = a;
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return BR_DONE;
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}
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for (unsigned i = 0; i < as.size() && _len > 0; ++i) {
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if (m_util.str.is_unit(as[i].get())) {
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if (_pos == 0) {
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bs.push_back(as[i].get());
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--_len;
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}
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else {
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--_pos;
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}
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}
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else {
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return BR_FAILED;
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}
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}
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if (bs.empty()) {
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result = m_util.str.mk_empty(m().get_sort(a));
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}
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else {
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result = m_util.str.mk_concat(bs);
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if (_pos + _len >= s.length()) {
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// case 2: pos+len goes past the end of the string
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unsigned _len = s.length() - _pos + 1;
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result = m_util.str.mk_string(s.extract(_pos, _len));
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} else {
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// case 3: pos+len still within string
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result = m_util.str.mk_string(s.extract(_pos, _len));
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}
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return BR_DONE;
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}
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return BR_FAILED;
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expr_ref_vector as(m()), bs(m());
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m_util.str.get_concat_units(a, as);
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if (as.empty()) {
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result = m_util.str.mk_empty(m().get_sort(a));
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return BR_DONE;
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}
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if (!constantPos) {
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return BR_FAILED;
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}
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unsigned _pos = pos.get_unsigned();
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// (extract s 0 (len s)) = s
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expr* a2 = nullptr;
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if (_pos == 0 && m_util.str.is_length(c, a2) && a == a2) {
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result = a;
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return BR_DONE;
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}
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unsigned offset = 0;
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for (; offset < as.size() && m_util.str.is_unit(as.get(offset)) && offset < _pos; ++offset) {};
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if (offset == 0 && _pos > 0) {
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return BR_FAILED;
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}
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if (_pos == 0 && !constantLen) {
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return BR_FAILED;
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}
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// (extract (++ (unit x) (unit y)) 3 c) = empty
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if (offset == as.size()) {
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result = m_util.str.mk_empty(m().get_sort(a));
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return BR_DONE;
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}
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SASSERT(offset != 0 || _pos == 0);
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if (constantLen && _pos == offset) {
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unsigned _len = len.get_unsigned();
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// (extract (++ (unit a) (unit b) (unit c) x) 1 2) = (++ (unit b) (unit c))
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unsigned i = offset;
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for (; i < as.size() && m_util.str.is_unit(as.get(i)) && i - offset < _len; ++i);
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if (i - offset == _len) {
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result = m_util.str.mk_concat(_len, as.c_ptr() + offset);
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return BR_DONE;
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}
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}
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if (offset == 0) {
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return BR_FAILED;
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}
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expr_ref len1(m()), pos1(m());
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pos1 = m_autil.mk_sub(b, m_autil.mk_int(offset));
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len1 = m_autil.mk_sub(c, m_autil.mk_int(offset));
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result = m_util.str.mk_concat(as.size() - offset, as.c_ptr() + offset);
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result = m_util.str.mk_substr(result, pos1, len1);
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return BR_REWRITE3;
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}
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bool seq_rewriter::cannot_contain_suffix(expr* a, expr* b) {
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@ -2396,6 +2396,7 @@ bool theory_seq::is_var(expr* a) const {
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!m_util.str.is_string(a) &&
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!m_util.str.is_unit(a) &&
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!m_util.str.is_itos(a) &&
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!m_util.str.is_extract(a) &&
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!m.is_ite(a);
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}
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