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z3-z3-4.12.6.src.ast.rewriter.bit2int.cpp Maven / Gradle / Ivy
/*++
Copyright (c) 2009 Microsoft Corporation
Module Name:
bit2cpp.cpp
Abstract:
Routines for simplifying bit2int expressions.
This propagates bv2int over arithmetical symbols as much as possible,
converting arithmetic operations into bit-vector operations.
Author:
Nikolaj Bjorner (nbjorner) 2009-08-28
Revision History:
--*/
#include "ast/ast_pp.h"
#include "ast/ast_ll_pp.h"
#include "ast/for_each_ast.h"
#include "ast/rewriter/bit2int.h"
bit2int::bit2int(ast_manager & m) :
m(m), m_bv_util(m), m_rewriter(m), m_arith_util(m), m_cache(m, false), m_bit0(m) {
m_bit0 = m_bv_util.mk_numeral(0,1);
}
void bit2int::operator()(expr * n, expr_ref & result, proof_ref& p) {
flush_cache();
expr_reduce emap(*this);
for_each_ast(emap, n);
result = get_cached(n);
if (m.proofs_enabled() && n != result.get()) {
// TBD: rough
p = m.mk_rewrite(n, result);
}
TRACE("bit2int",
tout << mk_pp(n, m) << "======>\n" << result << "\n";);
}
unsigned bit2int::get_b2i_size(expr* n) {
expr* arg = nullptr;
VERIFY(m_bv_util.is_bv2int(n, arg));
return m_bv_util.get_bv_size(arg);
}
unsigned bit2int::get_numeral_bits(numeral const& k) {
numeral two(2);
numeral n(abs(k));
unsigned num_bits = 1;
n = div(n, two);
while (n.is_pos()) {
++num_bits;
n = div(n, two);
}
return num_bits;
}
void bit2int::align_size(expr* e, unsigned sz, expr_ref& result) {
unsigned sz1 = m_bv_util.get_bv_size(e);
SASSERT(sz1 <= sz);
result = m_rewriter.mk_zero_extend(sz - sz1, e);
}
void bit2int::align_sizes(expr_ref& a, expr_ref& b) {
unsigned sz1 = m_bv_util.get_bv_size(a);
unsigned sz2 = m_bv_util.get_bv_size(b);
if (sz1 > sz2) {
b = m_rewriter.mk_zero_extend(sz1 - sz2, b);
}
else if (sz2 > sz1) {
a = m_rewriter.mk_zero_extend(sz2-sz1, a);
}
}
bool bit2int::extract_bv(expr* n, unsigned& sz, bool& sign, expr_ref& bv) {
numeral k;
bool is_int;
expr* r = nullptr;
if (m_bv_util.is_bv2int(n, r)) {
bv = r;
sz = m_bv_util.get_bv_size(bv);
sign = false;
return true;
}
else if (m_arith_util.is_numeral(n, k, is_int) && is_int) {
sz = get_numeral_bits(k);
bv = m_bv_util.mk_numeral(k, m_bv_util.mk_sort(sz));
sign = k.is_neg();
return true;
}
else {
return false;
}
}
bool bit2int::mk_add(expr* e1, expr* e2, expr_ref& result) {
unsigned sz1, sz2;
bool sign1, sign2;
expr_ref tmp1(m), tmp2(m), tmp3(m);
if (extract_bv(e1, sz1, sign1, tmp1) && !sign1 &&
extract_bv(e2, sz2, sign2, tmp2) && !sign2) {
unsigned sz;
numeral k;
if (m_bv_util.is_numeral(tmp1, k, sz) && k.is_zero()) {
result = e2;
return true;
}
if (m_bv_util.is_numeral(tmp2, k, sz) && k.is_zero()) {
result = e1;
return true;
}
align_sizes(tmp1, tmp2);
tmp1 = m_rewriter.mk_zero_extend(1, tmp1);
tmp2 = m_rewriter.mk_zero_extend(1, tmp2);
SASSERT(m_bv_util.get_bv_size(tmp1) == m_bv_util.get_bv_size(tmp2));
tmp3 = m_rewriter.mk_bv_add(tmp1, tmp2);
result = m_rewriter.mk_bv2int(tmp3);
return true;
}
return false;
}
bool bit2int::mk_comp(eq_type ty, expr* e1, expr* e2, expr_ref& result) {
unsigned sz1, sz2;
bool sign1, sign2;
expr_ref tmp1(m), tmp2(m), tmp3(m);
if (extract_bv(e1, sz1, sign1, tmp1) && !sign1 &&
extract_bv(e2, sz2, sign2, tmp2) && !sign2) {
align_sizes(tmp1, tmp2);
SASSERT(m_bv_util.get_bv_size(tmp1) == m_bv_util.get_bv_size(tmp2));
switch(ty) {
case lt:
tmp3 = m_rewriter.mk_ule(tmp2, tmp1);
result = m.mk_not(tmp3);
break;
case le:
result = m_rewriter.mk_ule(tmp1, tmp2);
break;
case eq:
result = m.mk_eq(tmp1, tmp2);
break;
}
return true;
}
return false;
}
bool bit2int::mk_mul(expr* e1, expr* e2, expr_ref& result) {
unsigned sz1, sz2;
bool sign1, sign2;
expr_ref tmp1(m), tmp2(m);
expr_ref tmp3(m);
if (extract_bv(e1, sz1, sign1, tmp1) &&
extract_bv(e2, sz2, sign2, tmp2)) {
align_sizes(tmp1, tmp2);
tmp1 = m_rewriter.mk_zero_extend(m_bv_util.get_bv_size(tmp1), tmp1);
tmp2 = m_rewriter.mk_zero_extend(m_bv_util.get_bv_size(tmp2), tmp2);
SASSERT(m_bv_util.get_bv_size(tmp1) == m_bv_util.get_bv_size(tmp2));
tmp3 = m_rewriter.mk_bv_mul(tmp1, tmp2);
result = m_rewriter.mk_bv2int(tmp3);
if (sign1 != sign2) {
result = m_arith_util.mk_uminus(result);
}
return true;
}
return false;
}
bool bit2int::is_bv_poly(expr* n, expr_ref& pos, expr_ref& neg) {
ptr_vector todo;
expr_ref tmp(m);
numeral k;
bool is_int;
todo.push_back(n);
neg = pos = m_rewriter.mk_bv2int(m_bit0);
while (!todo.empty()) {
n = todo.back();
todo.pop_back();
expr* arg1 = nullptr, *arg2 = nullptr;
if (m_bv_util.is_bv2int(n)) {
VERIFY(mk_add(n, pos, pos));
}
else if (m_arith_util.is_numeral(n, k, is_int) && is_int) {
if (k.is_nonneg()) {
VERIFY(mk_add(n, pos, pos));
}
else {
tmp = m_arith_util.mk_numeral(-k, true);
VERIFY(mk_add(tmp, neg, neg));
}
}
else if (m_arith_util.is_add(n)) {
for (expr* arg : *to_app(n)) {
todo.push_back(arg);
}
}
else if (m_arith_util.is_mul(n, arg1, arg2) &&
m_arith_util.is_numeral(arg1, k, is_int) && is_int && k.is_minus_one() &&
m_bv_util.is_bv2int(arg2)) {
VERIFY(mk_add(arg2, neg, neg));
}
else if (m_arith_util.is_mul(n, arg1, arg2) &&
m_arith_util.is_numeral(arg2, k, is_int) && is_int && k.is_minus_one() &&
m_bv_util.is_bv2int(arg1)) {
VERIFY(mk_add(arg1, neg, neg));
}
else if (m_arith_util.is_uminus(n, arg1) &&
m_bv_util.is_bv2int(arg1)) {
VERIFY(mk_add(arg1, neg, neg));
}
else {
TRACE("bit2int", tout << "Not a poly: " << mk_pp(n, m) << "\n";);
return false;
}
}
return true;
}
void bit2int::visit(quantifier* q) {
expr_ref result(m);
result = get_cached(q->get_expr());
result = m.update_quantifier(q, result);
cache_result(q, result);
}
void bit2int::visit(app* n) {
func_decl* f = n->get_decl();
unsigned num_args = n->get_num_args();
m_args.reset();
for (expr* arg : *n) {
m_args.push_back(get_cached(arg));
}
expr* const* args = m_args.data();
bool has_b2i =
m_arith_util.is_le(n) || m_arith_util.is_ge(n) || m_arith_util.is_gt(n) ||
m_arith_util.is_lt(n) || m.is_eq(n);
expr_ref result(m);
for (unsigned i = 0; !has_b2i && i < num_args; ++i) {
has_b2i = m_bv_util.is_bv2int(args[i]);
}
if (!has_b2i) {
result = m.mk_app(f, num_args, args);
cache_result(n, result);
return;
}
//
// bv2int(x) + bv2int(y) -> bv2int(pad(x) + pad(y))
// bv2int(x) + k -> bv2int(pad(x) + pad(k))
// bv2int(x) * bv2int(y) -> bv2int(pad(x) * pad(y))
// bv2int(x) * k -> sign(k)*bv2int(pad(x) * pad(k))
// bv2int(x) - bv2int(y) <= z -> bv2int(x) <= bv2int(y) + z
// bv2int(x) <= z - bv2int(y) -> bv2int(x) + bv2int(y) <= z
//
expr* e1 = nullptr, *e2 = nullptr;
expr_ref tmp1(m), tmp2(m);
expr_ref tmp3(m);
expr_ref pos1(m), neg1(m);
expr_ref pos2(m), neg2(m);
expr_ref e2bv(m);
bool sign2;
numeral k;
unsigned sz2;
if (num_args >= 2) {
e1 = args[0];
e2 = args[1];
}
if (m_arith_util.is_add(n) && num_args >= 1) {
result = e1;
for (unsigned i = 1; i < num_args; ++i) {
e1 = result;
e2 = args[i];
if (!mk_add(e1, e2, result)) {
result = m.mk_app(f, num_args, args);
cache_result(n, result);
return;
}
}
cache_result(n, result);
}
else if (m_arith_util.is_mul(n) && num_args >= 1) {
result = e1;
for (unsigned i = 1; i < num_args; ++i) {
e1 = result;
e2 = args[i];
if (!mk_mul(e1, e2, result)) {
result = m.mk_app(f, num_args, args);
cache_result(n, result);
return;
}
}
cache_result(n, result);
}
else if (m.is_eq(n) &&
is_bv_poly(e1, pos1, neg1) &&
is_bv_poly(e2, pos2, neg2) &&
mk_add(pos1, neg2, tmp1) &&
mk_add(neg1, pos2, tmp2) &&
mk_comp(eq, tmp1, tmp2, result)) {
cache_result(n, result);
}
else if (m_arith_util.is_le(n) &&
is_bv_poly(e1, pos1, neg1) &&
is_bv_poly(e2, pos2, neg2) &&
mk_add(pos1, neg2, tmp1) &&
mk_add(neg1, pos2, tmp2) &&
mk_comp(le, tmp1, tmp2, result)) {
cache_result(n, result);
}
else if (m_arith_util.is_lt(n) &&
is_bv_poly(e1, pos1, neg1) &&
is_bv_poly(e2, pos2, neg2) &&
mk_add(pos1, neg2, tmp1) &&
mk_add(neg1, pos2, tmp2) &&
mk_comp(lt, tmp1, tmp2, result)) {
cache_result(n, result);
}
else if (m_arith_util.is_ge(n) &&
is_bv_poly(e1, pos1, neg1) &&
is_bv_poly(e2, pos2, neg2) &&
mk_add(pos1, neg2, tmp1) &&
mk_add(neg1, pos2, tmp2) &&
mk_comp(le, tmp2, tmp1, result)) {
cache_result(n, result);
}
else if (m_arith_util.is_gt(n) &&
is_bv_poly(e1, pos1, neg1) &&
is_bv_poly(e2, pos2, neg2) &&
mk_add(pos1, neg2, tmp1) &&
mk_add(neg1, pos2, tmp2) &&
mk_comp(lt, tmp2, tmp1, result)) {
cache_result(n, result);
}
else if (m_arith_util.is_mod(n) &&
is_bv_poly(e1, pos1, neg1) &&
extract_bv(e2, sz2, sign2, e2bv) && !sign2) {
//
// (pos1 - neg1) mod e2 = (pos1 + (e2 - (neg1 mod e2))) mod e2
//
unsigned sz_p, sz_n, sz;
bool sign_p, sign_n;
expr_ref tmp_p(m), tmp_n(m);
VERIFY(extract_bv(pos1, sz_p, sign_p, tmp_p));
VERIFY(extract_bv(neg1, sz_n, sign_n, tmp_n));
SASSERT(!sign_p && !sign_n);
// pos1 mod e2
if (m_bv_util.is_numeral(tmp_n, k, sz) && k.is_zero()) {
tmp1 = tmp_p;
tmp2 = e2bv;
align_sizes(tmp1, tmp2);
tmp3 = m_rewriter.mk_bv_urem(tmp1, tmp2);
result = m_rewriter.mk_bv2int(tmp3);
cache_result(n, result);
return;
}
// neg1 mod e2;
tmp1 = tmp_n;
tmp2 = e2bv;
align_sizes(tmp1, tmp2);
tmp3 = m_rewriter.mk_bv_urem(tmp1, tmp2);
// e2 - (neg1 mod e2)
tmp1 = e2bv;
tmp2 = tmp3;
align_sizes(tmp1, tmp2);
tmp3 = m_rewriter.mk_bv_sub(tmp1, tmp2);
// pos1 + (e2 - (neg1 mod e2))
tmp1 = tmp_p;
tmp2 = tmp3;
align_sizes(tmp1, tmp2);
tmp_p = m_rewriter.mk_zero_extend(1, tmp1);
tmp_n = m_rewriter.mk_zero_extend(1, tmp2);
tmp1 = m_rewriter.mk_bv_add(tmp_p, tmp_n);
// (pos1 + (e2 - (neg1 mod e2))) mod e2
tmp2 = e2bv;
align_sizes(tmp1, tmp2);
tmp3 = m_rewriter.mk_bv_urem(tmp1, tmp2);
result = m_rewriter.mk_bv2int(tmp3);
cache_result(n, result);
}
else {
result = m.mk_app(f, num_args, args);
cache_result(n, result);
}
}
expr * bit2int::get_cached(expr * n) const {
expr* r = nullptr;
proof* p = nullptr;
const_cast(this)->m_cache.get(n, r, p);
CTRACE("bit2int", !r, tout << mk_pp(n, m) << "\n";);
return r;
}
void bit2int::cache_result(expr * n, expr * r) {
TRACE("bit2int_verbose", tout << "caching:\n" << mk_pp(n, m) <<
"======>\n" << mk_ll_pp(r, m) << "\n";);
m_cache.insert(n, r, nullptr);
}
