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more rewrite rules

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This commit is contained in:
Nikolaj Bjorner 2021-02-17 17:31:46 -08:00
parent bcad4d9435
commit e63dc7efc2
5 changed files with 150 additions and 39 deletions
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126
src/ast/rewriter/seq_rewriter.cpp
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@ -966,7 +966,6 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
bool constantBase = str().is_string(a, s);
bool constantPos = m_autil.is_numeral(b, pos);
bool constantLen = m_autil.is_numeral(c, len);
bool lengthPos = str().is_length(b) || m_autil.is_add(b);
sort* a_sort = a->get_sort();
sign sg;
@ -988,6 +987,12 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
return BR_DONE;
}
unsigned len_a;
if (constantPos && max_length(a, len_a) && rational(len_a) <= pos) {
result = str().mk_empty(a_sort);
return BR_DONE;
}
constantPos &= pos.is_unsigned();
constantLen &= len.is_unsigned();
@ -1013,20 +1018,21 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
return BR_DONE;
}
auto reassemble = [&](rational const& p, expr_ref_vector const& xs) {
expr_ref r(m_autil.mk_int(p), m());
for (expr* e : xs)
r = m_autil.mk_add(r, str().mk_length(e));
return r;
};
// extract(a + b + c, len(a + b), s) -> extract(c, 0, s)
// extract(a + b + c, len(a) + len(b), s) -> extract(c, 0, s)
if (lengthPos) {
m_lhs.reset();
expr_ref_vector lens(m());
str().get_concat(a, m_lhs);
TRACE("seq", tout << m_lhs << " " << pos << " " << lens << "\n";);
if (!get_lengths(b, lens, pos) || pos.is_neg()) {
return BR_FAILED;
}
expr_ref_vector lens(m());
if (get_lengths(b, lens, pos) && pos >= 0) {
unsigned i = 0;
for (; i < m_lhs.size(); ++i) {
expr* lhs = m_lhs.get(i);
for (; i < as.size(); ++i) {
expr* lhs = as.get(i);
if (lens.contains(lhs)) {
lens.erase(lhs);
}
@ -1037,32 +1043,54 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
break;
}
}
if (i == 0) return BR_FAILED;
expr_ref t1(m()), t2(m());
t1 = str().mk_concat(m_lhs.size() - i, m_lhs.c_ptr() + i, a->get_sort());
t2 = m_autil.mk_int(pos);
for (expr* rhs : lens) {
t2 = m_autil.mk_add(t2, str().mk_length(rhs));
if (i != 0) {
expr_ref t1(m());
t1 = str().mk_concat(as.size() - i, as.c_ptr() + i, a->get_sort());
expr_ref t2 = reassemble(pos, lens);
result = str().mk_substr(t1, t2, c);
TRACE("seq", tout << result << "\n";);
return BR_REWRITE2;
}
result = str().mk_substr(t1, t2, c);
TRACE("seq", tout << result << "\n";);
return BR_REWRITE2;
}
if (!constantPos) {
return BR_FAILED;
}
unsigned _pos = pos.get_unsigned();
// (extract s 0 (len s)) = s
expr* a2 = nullptr;
if (_pos == 0 && str().is_length(c, a2)) {
m_lhs.reset();
str().get_concat(a, m_lhs);
if (!m_lhs.empty() && m_lhs.get(0) == a2) {
result = a2;
// extract(a + b + c, 0, len(a) + len(b)) -> c
if (pos.is_zero()) {
lens.reset();
if (!get_lengths(c, lens, pos) || pos.is_neg())
return BR_FAILED;
unsigned i = 0;
for (; i < as.size(); ++i) {
expr* lhs = as.get(i);
if (lens.contains(lhs)) {
lens.erase(lhs);
}
else if (str().is_unit(lhs) && pos.is_pos()) {
pos -= rational(1);
}
else {
break;
}
}
if (i == as.size()) {
result = a;
return BR_DONE;
}
else if (i != 0) {
expr_ref t1(m()), t2(m());
t1 = str().mk_concat(as.size() - i, as.c_ptr() + i, a->get_sort());
t2 = reassemble(pos, lens);
result = str().mk_substr(t1, b, t2);
as[i] = result;
result = str().mk_concat(i + 1, as.c_ptr(), a->get_sort());
TRACE("seq", tout << result << "\n";);
return BR_REWRITE2;
}
}
expr* a1 = nullptr, *b1 = nullptr, *c1 = nullptr;
@ -1123,16 +1151,23 @@ br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& resu
}
bool seq_rewriter::get_lengths(expr* e, expr_ref_vector& lens, rational& pos) {
expr* arg = nullptr;
expr* arg = nullptr, *e1 = nullptr, *e2 = nullptr;
rational pos1;
if (m_autil.is_add(e)) {
for (expr* arg1 : *to_app(e)) {
if (!get_lengths(arg1, lens, pos)) return false;
if (!get_lengths(arg1, lens, pos))
return false;
}
}
else if (str().is_length(e, arg)) {
lens.push_back(arg);
}
else if (m_autil.is_mul(e, e1, e2) && m_autil.is_numeral(e1, pos1) && str().is_length(e2, arg) && pos1 <= 10) {
while (pos1 > 0) {
lens.push_back(arg);
pos1 -= rational(1);
}
}
else if (m_autil.is_numeral(e, pos1)) {
pos += pos1;
}
@ -4496,6 +4531,37 @@ bool seq_rewriter::min_length(expr_ref_vector const& es, unsigned& len) {
return bounded;
}
bool seq_rewriter::max_length(expr* e, unsigned& len) {
if (str().is_unit(e)) {
len = 1;
return true;
}
if (str().is_at(e)) {
len = 1;
return true;
}
zstring s;
if (str().is_string(e, s)) {
len = s.length();
return true;
}
if (str().is_empty(e)) {
len = 0;
return true;
}
if (str().is_concat(e)) {
unsigned l = 0;
len = 0;
for (expr* arg : *to_app(e)) {
if (!max_length(arg, l))
return false;
len += l;
}
return true;
}
return false;
}
bool seq_rewriter::is_string(unsigned n, expr* const* es, zstring& s) const {
zstring s1;
expr* e;