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z3/src/tactic/bv/bv_bounds_tactic.cpp
2021-02-11 13:49:47 -08:00

751 lines
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C++

/*++
Copyright (c) 2016 Microsoft Corporation
Module Name:
bv_bounds_tactic.cpp
Abstract:
Contextual bounds simplification tactic.
Author:
Nuno Lopes (nlopes) 2016-2-12
Nikolaj Bjorner (nbjorner)
--*/
#include "tactic/bv/bv_bounds_tactic.h"
#include "tactic/core/ctx_simplify_tactic.h"
#include "tactic/core/dom_simplify_tactic.h"
#include "ast/bv_decl_plugin.h"
#include "ast/ast_pp.h"
#include <climits>
static uint64_t uMaxInt(unsigned sz) {
SASSERT(sz <= 64);
return ULLONG_MAX >> (64u - sz);
}
namespace {
struct interval {
// l < h: [l, h]
// l > h: [0, h] U [l, UMAX_INT]
uint64_t l, h;
unsigned sz;
bool tight;
interval() {}
interval(uint64_t l, uint64_t h, unsigned sz, bool tight = false) : l(l), h(h), sz(sz), tight(tight) {
// canonicalize full set
if (is_wrapped() && l == h + 1) {
this->l = 0;
this->h = uMaxInt(sz);
}
SASSERT(invariant());
}
bool invariant() const {
return l <= uMaxInt(sz) && h <= uMaxInt(sz) &&
(!is_wrapped() || l != h+1);
}
bool is_full() const { return l == 0 && h == uMaxInt(sz); }
bool is_wrapped() const { return l > h; }
bool is_singleton() const { return l == h; }
bool operator==(const interval& b) const {
SASSERT(sz == b.sz);
return l == b.l && h == b.h && tight == b.tight;
}
bool operator!=(const interval& b) const { return !(*this == b); }
bool implies(const interval& b) const {
if (b.is_full())
return true;
if (is_full())
return false;
if (is_wrapped()) {
// l >= b.l >= b.h >= h
return b.is_wrapped() && h <= b.h && l >= b.l;
}
else if (b.is_wrapped()) {
// b.l > b.h >= h >= l
// h >= l >= b.l > b.h
return h <= b.h || l >= b.l;
}
else {
//
return l >= b.l && h <= b.h;
}
}
/// return false if intersection is unsat
bool intersect(const interval& b, interval& result) const {
if (is_full() || *this == b) {
result = b;
return true;
}
if (b.is_full()) {
result = *this;
return true;
}
if (is_wrapped()) {
if (b.is_wrapped()) {
if (h >= b.l) {
result = b;
} else if (b.h >= l) {
result = *this;
} else {
result = interval(std::max(l, b.l), std::min(h, b.h), sz);
}
} else {
return b.intersect(*this, result);
}
}
else if (b.is_wrapped()) {
// ... b.h ... l ... h ... b.l ..
if (h < b.l && l > b.h) {
return false;
}
// ... l ... b.l ... h ...
if (h >= b.l && l <= b.h) {
result = b;
} else if (h >= b.l) {
result = interval(b.l, h, sz);
} else {
// ... l .. b.h .. h .. b.l ...
SASSERT(l <= b.h);
result = interval(l, std::min(h, b.h), sz);
}
} else {
if (l > b.h || h < b.l)
return false;
// 0 .. l.. l' ... h ... h'
result = interval(std::max(l, b.l), std::min(h, b.h), sz, tight && b.tight);
}
return true;
}
/// return false if negation is empty
bool negate(interval& result) const {
if (!tight) {
result = interval(0, uMaxInt(sz), true);
return true;
}
if (is_full())
return false;
if (l == 0) {
result = interval(h + 1, uMaxInt(sz), sz);
} else if (uMaxInt(sz) == h) {
result = interval(0, l - 1, sz);
} else {
result = interval(h + 1, l - 1, sz);
}
return true;
}
};
#ifdef _TRACE
std::ostream& operator<<(std::ostream& o, const interval& I) {
o << "[" << I.l << ", " << I.h << "]";
return o;
}
#endif
struct undo_bound {
expr* e { nullptr };
interval b;
bool fresh { false };
undo_bound(expr* e, const interval& b, bool fresh) : e(e), b(b), fresh(fresh) {}
};
class bv_bounds_simplifier : public ctx_simplify_tactic::simplifier {
typedef obj_map<expr, interval> map;
typedef obj_map<expr, bool> expr_set;
typedef obj_map<expr, unsigned> expr_cnt;
ast_manager& m;
params_ref m_params;
bool m_propagate_eq;
bv_util m_bv;
vector<undo_bound> m_scopes;
map m_bound;
svector<expr_set*> m_expr_vars;
svector<expr_cnt*> m_bound_exprs;
bool is_number(expr *e, uint64_t& n, unsigned& sz) const {
rational r;
if (m_bv.is_numeral(e, r, sz) && sz <= 64) {
n = r.get_uint64();
return true;
}
return false;
}
bool is_bound(expr *e, expr*& v, interval& b) const {
uint64_t n;
expr *lhs = nullptr, *rhs = nullptr;
unsigned sz;
if (m_bv.is_bv_ule(e, lhs, rhs)) {
if (is_number(lhs, n, sz)) { // C ule x <=> x uge C
if (m_bv.is_numeral(rhs))
return false;
b = interval(n, uMaxInt(sz), sz, true);
v = rhs;
return true;
}
if (is_number(rhs, n, sz)) { // x ule C
b = interval(0, n, sz, true);
v = lhs;
return true;
}
}
else if (m_bv.is_bv_sle(e, lhs, rhs)) {
if (is_number(lhs, n, sz)) { // C sle x <=> x sge C
if (m_bv.is_numeral(rhs))
return false;
b = interval(n, (1ull << (sz-1)) - 1, sz, true);
v = rhs;
return true;
}
if (is_number(rhs, n, sz)) { // x sle C
b = interval(1ull << (sz-1), n, sz, true);
v = lhs;
return true;
}
} else if (m.is_eq(e, lhs, rhs)) {
if (is_number(lhs, n, sz)) {
if (m_bv.is_numeral(rhs))
return false;
b = interval(n, n, sz, true);
v = rhs;
return true;
}
if (is_number(rhs, n, sz)) {
b = interval(n, n, sz, true);
v = lhs;
return true;
}
}
return false;
}
public:
bv_bounds_simplifier(ast_manager& m, params_ref const& p) : m(m), m_params(p), m_bv(m) {
updt_params(p);
}
void updt_params(params_ref const & p) override {
m_propagate_eq = p.get_bool("propagate_eq", false);
}
static void get_param_descrs(param_descrs& r) {
r.insert("propagate-eq", CPK_BOOL, "(default: false) propagate equalities from inequalities");
}
~bv_bounds_simplifier() override {
for (auto* v : m_expr_vars) dealloc(v);
for (auto* b : m_bound_exprs) dealloc(b);
}
bool assert_expr(expr * t, bool sign) override {
TRACE("bv", tout << expr_ref(t, m) << "\n";);
while (m.is_not(t, t)) {
sign = !sign;
}
interval b;
expr* t1;
if (is_bound(t, t1, b)) {
SASSERT(!m_bv.is_numeral(t1));
if (sign) {
if (!b.negate(b)) {
return false;
}
}
TRACE("bv", tout << (sign?"(not ":"") << mk_pp(t, m) << (sign ? ")" : "") << ": " << mk_pp(t1, m) << " in " << b << "\n";);
map::obj_map_entry* e = m_bound.find_core(t1);
if (e) {
interval& old = e->get_data().m_value;
interval intr;
if (!old.intersect(b, intr))
return false;
if (old == intr)
return true;
m_scopes.insert(undo_bound(t1, old, false));
old = intr;
} else {
m_bound.insert(t1, b);
m_scopes.insert(undo_bound(t1, interval(), true));
}
}
return true;
}
bool simplify(expr* t, expr_ref& result) override {
expr* t1;
interval b;
if (m_bound.find(t, b) && b.is_singleton()) {
result = m_bv.mk_numeral(b.l, m_bv.get_bv_size(t));
return true;
}
if (!m.is_bool(t))
return false;
bool sign = false;
while (m.is_not(t, t)) {
sign = !sign;
}
if (!is_bound(t, t1, b))
return false;
if (sign && b.tight) {
sign = false;
if (!b.negate(b)) {
result = m.mk_false();
return true;
}
}
interval ctx, intr;
result = nullptr;
if (b.is_full() && b.tight) {
result = m.mk_true();
} else if (m_bound.find(t1, ctx)) {
if (ctx.implies(b)) {
result = m.mk_true();
}
else if (!b.intersect(ctx, intr)) {
result = m.mk_false();
}
else if (m_propagate_eq && intr.is_singleton()) {
result = m.mk_eq(t1, m_bv.mk_numeral(rational(intr.l, rational::ui64()), t1->get_sort()));
}
}
CTRACE("bv", result != 0, tout << mk_pp(t, m) << " " << b << " (ctx: " << ctx << ") (intr: " << intr << "): " << result << "\n";);
if (sign && result != 0)
result = m.mk_not(result);
return result != 0;
}
// check if t contains v
ptr_vector<expr> todo;
bool contains(expr* t, expr* v) {
ast_fast_mark1 mark;
todo.push_back(t);
while (!todo.empty()) {
t = todo.back();
todo.pop_back();
if (mark.is_marked(t)) {
continue;
}
if (t == v) {
todo.reset();
return true;
}
mark.mark(t);
if (!is_app(t)) {
continue;
}
app* a = to_app(t);
todo.append(a->get_num_args(), a->get_args());
}
return false;
}
bool contains_bound(expr* t) {
ast_fast_mark1 mark1;
ast_fast_mark2 mark2;
todo.push_back(t);
while (!todo.empty()) {
t = todo.back();
todo.pop_back();
if (mark1.is_marked(t)) {
continue;
}
mark1.mark(t);
if (!is_app(t)) {
continue;
}
interval b;
expr* e;
if (is_bound(t, e, b)) {
if (mark2.is_marked(e)) {
todo.reset();
return true;
}
mark2.mark(e);
if (m_bound.contains(e)) {
todo.reset();
return true;
}
}
app* a = to_app(t);
todo.append(a->get_num_args(), a->get_args());
}
return false;
}
bool may_simplify(expr* t) override {
if (m_bv.is_numeral(t))
return false;
while (m.is_not(t, t));
for (auto & v : m_bound) {
if (contains(t, v.m_key)) return true;
}
expr* t1;
interval b;
// skip common case: single bound constraint without any context for simplification
if (is_bound(t, t1, b)) {
return b.is_full() || m_bound.contains(t1);
}
if (contains_bound(t)) {
return true;
}
return false;
}
void pop(unsigned num_scopes) override {
TRACE("bv", tout << "pop: " << num_scopes << "\n";);
if (m_scopes.empty())
return;
unsigned target = m_scopes.size() - num_scopes;
if (target == 0) {
m_bound.reset();
m_scopes.reset();
return;
}
for (unsigned i = m_scopes.size()-1; i >= target; --i) {
undo_bound& undo = m_scopes[i];
SASSERT(m_bound.contains(undo.e));
if (undo.fresh) {
m_bound.erase(undo.e);
} else {
m_bound.insert(undo.e, undo.b);
}
}
m_scopes.shrink(target);
}
simplifier * translate(ast_manager & m) override {
return alloc(bv_bounds_simplifier, m, m_params);
}
unsigned scope_level() const override {
return m_scopes.size();
}
};
class dom_bv_bounds_simplifier : public dom_simplifier {
typedef obj_map<expr, interval> map;
typedef obj_map<expr, bool> expr_set;
typedef obj_map<expr, unsigned> expr_cnt;
ast_manager& m;
params_ref m_params;
bool m_propagate_eq;
bv_util m_bv;
vector<undo_bound> m_scopes;
map m_bound;
svector<expr_set*> m_expr_vars;
svector<expr_cnt*> m_bound_exprs;
bool is_number(expr *e, uint64_t& n, unsigned& sz) const {
rational r;
if (m_bv.is_numeral(e, r, sz) && sz <= 64) {
n = r.get_uint64();
return true;
}
return false;
}
bool is_bound(expr *e, expr*& v, interval& b) const {
uint64_t n;
expr *lhs = nullptr, *rhs = nullptr;
unsigned sz = 0;
if (m_bv.is_bv_ule(e, lhs, rhs)) {
if (is_number(lhs, n, sz)) { // C ule x <=> x uge C
if (m_bv.is_numeral(rhs))
return false;
b = interval(n, uMaxInt(sz), sz, true);
v = rhs;
return true;
}
if (is_number(rhs, n, sz)) { // x ule C
b = interval(0, n, sz, true);
v = lhs;
return true;
}
}
else if (m_bv.is_bv_sle(e, lhs, rhs)) {
if (is_number(lhs, n, sz)) { // C sle x <=> x sge C
if (m_bv.is_numeral(rhs))
return false;
b = interval(n, (1ull << (sz-1)) - 1, sz, true);
v = rhs;
return true;
}
if (is_number(rhs, n, sz)) { // x sle C
b = interval(1ull << (sz-1), n, sz, true);
v = lhs;
return true;
}
} else if (m.is_eq(e, lhs, rhs)) {
if (is_number(lhs, n, sz)) {
if (m_bv.is_numeral(rhs))
return false;
b = interval(n, n, sz, true);
v = rhs;
return true;
}
if (is_number(rhs, n, sz)) {
b = interval(n, n, sz, true);
v = lhs;
return true;
}
}
return false;
}
public:
dom_bv_bounds_simplifier(ast_manager& m, params_ref const& p) : m(m), m_params(p), m_bv(m) {
updt_params(p);
}
virtual void updt_params(params_ref const & p) {
m_propagate_eq = p.get_bool("propagate_eq", false);
}
static void get_param_descrs(param_descrs& r) {
r.insert("propagate-eq", CPK_BOOL, "(default: false) propagate equalities from inequalities");
}
~dom_bv_bounds_simplifier() override {
for (unsigned i = 0, e = m_expr_vars.size(); i < e; ++i) {
dealloc(m_expr_vars[i]);
}
for (unsigned i = 0, e = m_bound_exprs.size(); i < e; ++i) {
dealloc(m_bound_exprs[i]);
}
}
bool assert_expr(expr * t, bool sign) override {
while (m.is_not(t, t)) {
sign = !sign;
}
interval b;
expr* t1;
if (is_bound(t, t1, b)) {
SASSERT(!m_bv.is_numeral(t1));
if (sign)
VERIFY(b.negate(b));
TRACE("bv", tout << (sign?"(not ":"") << mk_pp(t, m) << (sign ? ")" : "") << ": " << mk_pp(t1, m) << " in " << b << "\n";);
map::obj_map_entry* e = m_bound.find_core(t1);
if (e) {
interval& old = e->get_data().m_value;
interval intr;
if (!old.intersect(b, intr))
return false;
if (old == intr)
return true;
m_scopes.push_back(undo_bound(t1, old, false));
old = intr;
} else {
m_bound.insert(t1, b);
m_scopes.push_back(undo_bound(t1, interval(), true));
}
}
return true;
}
void operator()(expr_ref& r) override {
expr* t1, * t = r;
interval b;
if (m_bound.find(t, b) && b.is_singleton()) {
r = m_bv.mk_numeral(b.l, m_bv.get_bv_size(t));
return;
}
if (!m.is_bool(t))
return;
bool sign = false;
while (m.is_not(t, t)) {
sign = !sign;
}
if (!is_bound(t, t1, b))
return;
if (sign && b.tight) {
sign = false;
if (!b.negate(b)) {
r = m.mk_false();
return;
}
}
interval ctx, intr;
bool was_updated = true;
if (b.is_full() && b.tight) {
r = m.mk_true();
}
else if (m_bound.find(t1, ctx)) {
if (ctx.implies(b)) {
r = m.mk_true();
}
else if (!b.intersect(ctx, intr)) {
r = m.mk_false();
}
else if (m_propagate_eq && intr.is_singleton()) {
r = m.mk_eq(t1, m_bv.mk_numeral(rational(intr.l, rational::ui64()),
t1->get_sort()));
}
else {
was_updated = false;
}
}
else {
was_updated = false;
}
TRACE("bv", tout << mk_pp(t, m) << " " << b << " (ctx: " << ctx << ") (intr: " << intr << "): " << r << "\n";);
if (sign && was_updated)
r = m.mk_not(r);
}
// check if t contains v
ptr_vector<expr> todo;
bool contains(expr* t, expr* v) {
ast_fast_mark1 mark;
todo.push_back(t);
while (!todo.empty()) {
t = todo.back();
todo.pop_back();
if (mark.is_marked(t)) {
continue;
}
if (t == v) {
todo.reset();
return true;
}
mark.mark(t);
if (!is_app(t)) {
continue;
}
app* a = to_app(t);
todo.append(a->get_num_args(), a->get_args());
}
return false;
}
bool contains_bound(expr* t) {
ast_fast_mark1 mark1;
ast_fast_mark2 mark2;
todo.push_back(t);
while (!todo.empty()) {
t = todo.back();
todo.pop_back();
if (mark1.is_marked(t)) {
continue;
}
mark1.mark(t);
if (!is_app(t)) {
continue;
}
interval b;
expr* e;
if (is_bound(t, e, b)) {
if (mark2.is_marked(e)) {
todo.reset();
return true;
}
mark2.mark(e);
if (m_bound.contains(e)) {
todo.reset();
return true;
}
}
app* a = to_app(t);
todo.append(a->get_num_args(), a->get_args());
}
return false;
}
void pop(unsigned num_scopes) override {
TRACE("bv", tout << "pop: " << num_scopes << "\n";);
if (m_scopes.empty())
return;
unsigned target = m_scopes.size() - num_scopes;
if (target == 0) {
m_bound.reset();
m_scopes.reset();
return;
}
for (unsigned i = m_scopes.size()-1; i >= target; --i) {
undo_bound& undo = m_scopes[i];
SASSERT(m_bound.contains(undo.e));
if (undo.fresh) {
m_bound.erase(undo.e);
} else {
m_bound.insert(undo.e, undo.b);
}
}
m_scopes.shrink(target);
}
dom_simplifier * translate(ast_manager & m) override {
return alloc(dom_bv_bounds_simplifier, m, m_params);
}
unsigned scope_level() const override {
return m_scopes.size();
}
};
}
tactic * mk_bv_bounds_tactic(ast_manager & m, params_ref const & p) {
return clean(alloc(ctx_simplify_tactic, m, alloc(bv_bounds_simplifier, m, p), p));
}
tactic * mk_dom_bv_bounds_tactic(ast_manager & m, params_ref const & p) {
return clean(alloc(dom_simplify_tactic, m, alloc(dom_bv_bounds_simplifier, m, p), p));
}