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Regex membership (#7506)
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* Make finding a word in the regex iterative

* Fixed gc problem
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@CEisenhofer
CEisenhofer authored Jan 12, 2025
1 parent 9a237d5 commit c572fc2
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Showing 5 changed files with 97 additions and 163 deletions.
7 changes: 5 additions & 2 deletions src/ast/converters/expr_inverter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -883,10 +883,13 @@ class seq_expr_inverter : public iexpr_inverter {
case OP_SEQ_IN_RE:
if (uncnstr(args[0]) && seq.re.is_ground(args[1]) && seq.is_string(args[0]->get_sort())) {
#if 1
zstring s1, s2;
zstring s1;
expr* re = args[1];
if (!rw.some_string_in_re(re, s1))
return false;
zstring s2;
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))
if (!rw.some_string_in_re(not_re, s2))
return false;

mk_fresh_uncnstr_var_for(f, r);
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156 changes: 90 additions & 66 deletions src/ast/rewriter/seq_rewriter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6152,91 +6152,115 @@ bool seq_rewriter::some_string_in_re(expr* r, zstring& s) {
// SASSERT(re().is_re(r, rs) && m_util.is_string(rs));
expr_mark visited;
unsigned_vector str;
expr_ref_vector pinned(m());

if (!some_string_in_re(pinned, visited, r, str))
if (!some_string_in_re(visited, r, str))
return false;
s = zstring(str.size(), str.data());
return true;
}

bool seq_rewriter::some_string_in_re(expr_ref_vector& pinned, expr_mark& visited, expr* r, unsigned_vector& str) {
if (visited.is_marked(r))
return false;
if (re().is_empty(r))
return false;
auto info = re().get_info(r);
if (info.nullable == l_true)
return true;
visited.mark(r);
pinned.push_back(r);
if (re().is_union(r))
return any_of(*to_app(r), [&](expr* arg) { return some_string_in_re(pinned, visited, arg, str); });

expr_ref r2 = mk_derivative(r);
struct re_eval_pos {
expr_ref e; // use reference to avoid gc
unsigned str_len;
buffer<std::pair<unsigned, unsigned>> exclude;
return append_char(pinned, visited, exclude, r2, str);
}
bool needs_derivation;
};

bool seq_rewriter::append_char(expr_ref_vector& pinned, expr_mark& visited, buffer<std::pair<unsigned, unsigned>>& exclude, expr* r, unsigned_vector& str) {
expr* c, * th, * el;
if (re().is_empty(r))
return false;
if (re().is_union(r))
return any_of(*to_app(r), [&](expr* arg) { return append_char(pinned, visited, exclude, arg, str); });
if (m().is_ite(r, c, th, el)) {
unsigned low = 0, high = zstring::unicode_max_char();
if (get_bounds(c, low, high)) {
SASSERT(low <= high);
str.push_back(low); // ASSERT: low .. high does not intersect with exclude
if (some_string_in_re(pinned, visited, th, str))
bool seq_rewriter::some_string_in_re(expr_mark& visited, expr* r, unsigned_vector& str) {
SASSERT(str.empty());
vector<re_eval_pos> todo;
todo.push_back({ expr_ref(r, m()), 0, {}, true });
while (!todo.empty()) {
re_eval_pos current = todo.back();
todo.pop_back();
r = current.e;
str.resize(current.str_len);
if (current.needs_derivation) {
SASSERT(current.exclude.empty());
// We are looking for the next character => generate derivation
if (visited.is_marked(r))
continue;
if (re().is_empty(r))
continue;
auto info = re().get_info(r);
if (info.nullable == l_true)
return true;
str.pop_back();
visited.mark(r);
if (re().is_union(r)) {
for (expr* arg : *to_app(r)) {
todo.push_back({ expr_ref(arg, m()), str.size(), {}, true });
}
continue;
}

r = mk_derivative(r);
}
if (re().is_empty(el))
return false;
exclude.push_back({ low, high });
if (append_char(pinned, visited, exclude, el, str))
return true;
exclude.pop_back();
return false;
}
// otw. we are still in the process of deciding case of the derivation to take

buffer<std::pair<unsigned, unsigned>> exclude = std::move(current.exclude);

if (is_ground(r)) {
// ensure selected character is not in exclude
unsigned ch = 'a';
bool wrapped = false;
while (true) {
bool found = false;
for (auto [l, h] : exclude) {
if (l <= ch && ch <= h) {
found = true;
ch = h + 1;
expr* c, * th, * el;
if (re().is_empty(r))
continue;
if (re().is_union(r)) {
for (expr* arg : *to_app(r)) {
todo.push_back({ expr_ref(arg, m()), str.size(), exclude, false });
}
continue;
}
if (m().is_ite(r, c, th, el)) {
unsigned low = 0, high = zstring::unicode_max_char();
bool hasBounds = get_bounds(c, low, high);
if (!re().is_empty(el)) {
exclude.push_back({ low, high });
todo.push_back({ expr_ref(el, m()), str.size(), std::move(exclude), false });
}
if (hasBounds) {
// I want this case to be processed first => push it last
// reason: current string is only pruned
SASSERT(low <= high);
str.push_back(low); // ASSERT: low .. high does not intersect with exclude
todo.push_back({ expr_ref(th, m()), str.size(), {}, true });
}
continue;
}

if (is_ground(r)) {
// ensure selected character is not in exclude
unsigned ch = 'a';
bool wrapped = false;
bool failed = false;
while (true) {
bool found = false;
for (auto [l, h] : exclude) {
if (l <= ch && ch <= h) {
found = true;
ch = h + 1;
}
}
if (!found)
break;
if (ch != zstring::unicode_max_char() + 1)
continue;
if (wrapped) {
failed = true;
break;
}
ch = 0;
wrapped = true;
}
if (!found)
break;
if (ch != zstring::unicode_max_char() + 1)
if (failed)
continue;
if (wrapped)
return false;
ch = 0;
wrapped = true;
str.push_back(ch);
todo.push_back({ expr_ref(r, m()), str.size(), {}, true });
continue;
}
str.push_back(ch);
if (some_string_in_re(pinned, visited, r, str))
return true;
str.pop_back();
return false;
}

verbose_stream() << "todo append_char " << mk_pp(r, m()) << "\n";
// TODO: select characters from m_chars[ctx.rand(m_chars.size())]);
str.push_back('a');
UNREACHABLE();
}
return false;
}


bool seq_rewriter::get_bounds(expr* e, unsigned& low, unsigned& high) {
low = 0;
high = zstring::unicode_max_char();
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4 changes: 1 addition & 3 deletions src/ast/rewriter/seq_rewriter.h
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Original file line number Diff line number Diff line change
Expand Up @@ -354,9 +354,7 @@ class seq_rewriter {
void intersect(unsigned lo, unsigned hi, svector<std::pair<unsigned, unsigned>>& ranges);

bool get_bounds(expr* e, unsigned& low, unsigned& high);
bool append_char(expr_ref_vector& pinned, expr_mark& visited, buffer<std::pair<unsigned, unsigned>>& exclude, expr* r, unsigned_vector& str);
bool some_string_in_re(expr_ref_vector& pinned, expr_mark& visited, expr* r, unsigned_vector& str);

bool some_string_in_re(expr_mark& visited, expr* r, unsigned_vector& str);

public:
seq_rewriter(ast_manager & m, params_ref const & p = params_ref()):
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90 changes: 1 addition & 89 deletions src/ast/sls/sls_seq_plugin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1847,7 +1847,7 @@ namespace sls {

{
zstring s1;
if (ctx.is_true(e) && some_string_in_re(y, s1)) {
if (ctx.is_true(e) && rw.some_string_in_re(y, s1)) {
m_str_updates.push_back({ x, s1, 1 });
return apply_update();
}
Expand Down Expand Up @@ -2001,92 +2001,4 @@ namespace sls {
choose(r2, k - 1, prefix2, result);
}
}

//
// Find some string that is a member of regex
//
bool seq_plugin::some_string_in_re(expr* _r, zstring& s) {
expr_ref r(_r, m);
seq_rewriter rw(m);
while (true) {
if (seq.re.is_empty(r))
return false;
auto info = seq.re.get_info(r);
if (info.nullable == l_true)
return true;
expr_ref r2 = rw.mk_derivative(r);
if (!append_char(r, r2, s))
return false;
r = r2;
}
}

bool seq_plugin::get_bounds(expr* e, unsigned& low, unsigned& high) {
// TODO: remove recursion (though it is probably not deep anyway)
expr* x, * y;
unsigned ch = 0;
if (m.is_and(e, x, y)) {
if (!get_bounds(x, low, high))
return false;
return get_bounds(y, low, high);
}
if (m.is_eq(e, x, y)) {
if ((is_var(x) && seq.is_const_char(y, ch)) || (is_var(y) && seq.is_const_char(x, ch))) {
if (ch < low || ch > high)
return false;
low = high = ch;
return true;
}
return false;
}
if (seq.is_char_le(e, x, y)) {
if (seq.is_const_char(x, ch)) {
low = std::max(ch, low);
return high >= low;
}
if (seq.is_const_char(y, ch)) {
high = std::min(ch, high);
return high >= low;
}
return false;
}
return false;
}

bool seq_plugin::append_char(expr* r0, expr_ref& r, zstring& s) {
expr* c, * th, * el;
if (seq.re.is_union(r)) {
auto info0 = seq.re.get_info(r0);
for (expr* r1 : *to_app(r)) {
auto info1 = seq.re.get_info(r1);
if (r0 == r1)
continue;
if (info1.min_length < info0.min_length) {
r = r1;
return append_char(r0, r, s);
}
}
expr* r2;
do {
r2 = to_app(r)->get_arg(ctx.rand(to_app(r)->get_num_args()));
} while (r2 == r0);
r = r2;
// Just take one that is not a self loop (there is always such one element)
return append_char(r0, r, s);
}
if (m.is_ite(r, c, th, el)) {
unsigned low = 0, high = UINT_MAX;
if (get_bounds(c, low, high)) {
SASSERT(low <= high);
s += zstring(low);
r = th;
return true;
}
verbose_stream() << "nyi append_char " << mk_bounded_pp(r, m) << "\n";
NOT_IMPLEMENTED_YET();
return false;
}
s += zstring(m_chars[ctx.rand(m_chars.size())]);
return true;
}
}
3 changes: 0 additions & 3 deletions src/ast/sls/sls_seq_plugin.h
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Original file line number Diff line number Diff line change
Expand Up @@ -147,9 +147,6 @@ namespace sls {
void next_char(expr* r, unsigned_vector& chars);

bool is_in_re(zstring const& s, expr* r);
bool some_string_in_re(expr* r, zstring& s);
bool get_bounds(expr* e, unsigned& low, unsigned& high);
bool append_char(expr* r0, expr_ref& r, zstring& s);

// access evaluation
bool is_seq_predicate(expr* e);
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