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sign_ext

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This commit is contained in:
Jakob Rath 2023-07-21 11:25:31 +02:00
parent 6dfc9dd936
commit e1bb0f5377
5 changed files with 48 additions and 20 deletions
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36
src/math/polysat/constraint_manager.cpp
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@ -643,19 +643,43 @@ namespace polysat {
pdd constraint_manager::zero_ext(pdd const& p, unsigned bit_width) { pdd constraint_manager::zero_ext(pdd const& p, unsigned bit_width) {
SASSERT(bit_width > p.power_of_2()); SASSERT(bit_width > p.power_of_2());
pdd const q = s.var(s.m_names.mk_name(p)); pdd const q = s.var(s.m_names.mk_name(p));
constraint_dedup::zext_args args = {q.var(), bit_width}; constraint_dedup::bv_ext_args const args = {false, q.var(), bit_width};
auto it = m_dedup.m_zext_expr.find_iterator(args); auto const it = m_dedup.m_bv_ext_expr.find_iterator(args);
if (it != m_dedup.m_zext_expr.end()) if (it != m_dedup.m_bv_ext_expr.end())
return s.var(it->m_value); return s.var(it->m_value);
pdd const v = s.var(s.add_var(bit_width)); pdd const v = s.var(s.add_var(bit_width));
m_dedup.m_zext_expr.insert(args, v.var()); m_dedup.m_bv_ext_expr.insert(args, v.var());
// v[|p|-1:0] = p // (1) v[|p|-1:0] = p
s.add_eq(q, extract(v, p.power_of_2() - 1, 0)); s.add_eq(q, extract(v, p.power_of_2() - 1, 0));
// v < 2^|p| // (2) v < 2^|p|
s.add_ule(q, p.manager().max_value()); s.add_ule(q, p.manager().max_value());
return v; return v;
} }
pdd constraint_manager::sign_ext(pdd const& p, unsigned bit_width) {
unsigned const p_sz = p. power_of_2();
SASSERT(bit_width > p_sz);
pdd const q = s.var(s.m_names.mk_name(p));
constraint_dedup::bv_ext_args const args = {true, q.var(), bit_width};
auto const it = m_dedup.m_bv_ext_expr.find_iterator(args);
if (it != m_dedup.m_bv_ext_expr.end())
return s.var(it->m_value);
pdd const v = s.var(s.add_var(bit_width));
m_dedup.m_bv_ext_expr.insert(args, v.var());
// (1) v[|p|-1:0] = p
s.add_eq(q, extract(v, p_sz - 1, 0));
// (2) Let h := v[bit_width-1:|p|]
pdd const h = extract(v, bit_width - 1, p_sz);
signed_constraint p_negative = s.uge(p, rational::power_of_two(p_sz - 1));
// (3) p < 2^(|p|-1) ==> h = 0
s.add_clause(p_negative, s.eq(h), false);
// (4) p >= 2^(|p|-1) ==> h = max_value
s.add_clause(~p_negative, s.eq(h, h.manager().max_value()), false);
// (5) h + 1 <= 1 (i.e., h = b000...0 or h = b111...1) ... implied by (3), (4); maybe better to just exclude h from decisions as it is basically a defined variable
s.add_ule(h + 1, 1);
return v;
}
/** unsigned quotient/remainder */ /** unsigned quotient/remainder */
std::pair<pdd, pdd> constraint_manager::div_rem_op_constraint(pdd const& a, pdd const& b) { std::pair<pdd, pdd> constraint_manager::div_rem_op_constraint(pdd const& a, pdd const& b) {
auto& m = a.manager(); auto& m = a.manager();

16
src/math/polysat/constraint_manager.h
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@ -42,15 +42,16 @@ namespace polysat {
quot_rem_expr_map m_quot_rem_expr; quot_rem_expr_map m_quot_rem_expr;
vector<std::tuple<pdd, pdd, pvar, pvar>> m_div_rem_list; vector<std::tuple<pdd, pdd, pvar, pvar>> m_div_rem_list;
using zext_args = std::pair<pvar, unsigned>; // zero_ext or sign_ext
using zext_args_eq = default_eq<zext_args>; using bv_ext_args = std::tuple<bool, pvar, unsigned>;
struct zext_args_hash { using bv_ext_args_eq = default_eq<bv_ext_args>;
unsigned operator()(zext_args const& args) const { struct bv_ext_args_hash {
return combine_hash(args.first, args.second); unsigned operator()(bv_ext_args const& args) const {
return mk_mix(std::get<0>(args), std::get<1>(args), std::get<2>(args));
} }
}; };
using zext_expr_map = map<zext_args, pvar, zext_args_hash, zext_args_eq>; using bv_ext_expr_map = map<bv_ext_args, pvar, bv_ext_args_hash, bv_ext_args_eq>;
zext_expr_map m_zext_expr; bv_ext_expr_map m_bv_ext_expr;
}; };
// Manage constraint lifetime, deduplication, and connection to boolean variables/literals. // Manage constraint lifetime, deduplication, and connection to boolean variables/literals.
@ -172,6 +173,7 @@ namespace polysat {
pdd concat(unsigned num_args, pdd const* args); pdd concat(unsigned num_args, pdd const* args);
pdd zero_ext(pdd const& p, unsigned bit_width); pdd zero_ext(pdd const& p, unsigned bit_width);
pdd sign_ext(pdd const& p, unsigned bit_width);
constraint* const* begin() const { return m_constraints.data(); } constraint* const* begin() const { return m_constraints.data(); }
constraint* const* end() const { return m_constraints.data() + m_constraints.size(); } constraint* const* end() const { return m_constraints.data() + m_constraints.size(); }

3
src/math/polysat/solver.h
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@ -421,6 +421,9 @@ namespace polysat {
/** Create expression for zero-extension of p */ /** Create expression for zero-extension of p */
pdd zero_ext(pdd const& p, unsigned bit_width) { return m_constraints.zero_ext(p, bit_width); } pdd zero_ext(pdd const& p, unsigned bit_width) { return m_constraints.zero_ext(p, bit_width); }
/** Create expression for signed-extension of p */
pdd sign_ext(pdd const& p, unsigned bit_width) { return m_constraints.sign_ext(p, bit_width); }
/** /**
* Create terms for unsigned quot-rem * Create terms for unsigned quot-rem
* *

11
src/sat/smt/bv_polysat.cpp
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@ -93,8 +93,8 @@ namespace bv {
case OP_EXTRACT: polysat_extract(a); break; case OP_EXTRACT: polysat_extract(a); break;
case OP_CONCAT: polysat_concat(a); break; case OP_CONCAT: polysat_concat(a); break;
case OP_ZERO_EXT: polysat_zero_ext(a); break; case OP_ZERO_EXT: polysat_par_unary(a, [&](pdd const& p, unsigned sz) { return m_polysat.zero_ext(p, sz); }); break;
case OP_SIGN_EXT: case OP_SIGN_EXT: polysat_par_unary(a, [&](pdd const& p, unsigned sz) { return m_polysat.sign_ext(p, sz); }); break;
// polysat::solver should also support at least: // polysat::solver should also support at least:
case OP_BREDAND: // x == 2^K - 1 case OP_BREDAND: // x == 2^K - 1
@ -197,11 +197,10 @@ namespace bv {
polysat_set(e, p); polysat_set(e, p);
} }
void solver::polysat_zero_ext(app* e) { void solver::polysat_par_unary(app* e, std::function<polysat::pdd(polysat::pdd,unsigned)> const& fn) {
pdd const arg = expr2pdd(e->get_arg(0)); pdd const p = expr2pdd(e->get_arg(0));
unsigned const sz = e->get_parameter(0).get_int(); unsigned const sz = e->get_parameter(0).get_int();
pdd const p = m_polysat.zero_ext(p, sz); polysat_set(e, fn(p, sz));
polysat_set(e, p);
} }
void solver::polysat_binary(app* e, std::function<polysat::pdd(polysat::pdd, polysat::pdd)> const& fn) { void solver::polysat_binary(app* e, std::function<polysat::pdd(polysat::pdd, polysat::pdd)> const& fn) {

2
src/sat/smt/bv_solver.h
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@ -325,9 +325,9 @@ namespace bv {
void polysat_pop(unsigned n); void polysat_pop(unsigned n);
void polysat_unary(app* e, std::function<polysat::pdd(polysat::pdd)> const& fn); void polysat_unary(app* e, std::function<polysat::pdd(polysat::pdd)> const& fn);
void polysat_binary(app* e, std::function<polysat::pdd(polysat::pdd, polysat::pdd)> const& fn); void polysat_binary(app* e, std::function<polysat::pdd(polysat::pdd, polysat::pdd)> const& fn);
void polysat_par_unary(app* e, std::function<polysat::pdd(polysat::pdd,unsigned)> const& fn);
void polysat_extract(app* e); void polysat_extract(app* e);
void polysat_concat(app* e); void polysat_concat(app* e);
void polysat_zero_ext(app* e);
polysat::pdd expr2pdd(expr* e); polysat::pdd expr2pdd(expr* e);
void polysat_set(euf::theory_var v, polysat::pdd const& p); void polysat_set(euf::theory_var v, polysat::pdd const& p);
polysat::pdd var2pdd(euf::theory_var v); polysat::pdd var2pdd(euf::theory_var v);