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tuning bit-vector operations

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2015-12-21 13:09:03 +02:00
parent 1eebab355c
commit 8e26c97782
9 changed files with 271 additions and 94 deletions
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5
src/ast/rewriter/bit_blaster/bit_blaster_tpl.h
View file

@ -121,8 +121,11 @@ public:
void mk_comp(unsigned sz, expr * const * a_bits, expr * const * b_bits, expr_ref_vector & out_bits);
void mk_carry_save_adder(unsigned sz, expr * const * a_bits, expr * const * b_bits, expr * const * c_bits, expr_ref_vector & sum_bits, expr_ref_vector & carry_bits);
void mk_const_multiplier(unsigned sz, expr * const * a_bits, expr * const * b_bits, expr_ref_vector & out_bits);
bool mk_const_multiplier(unsigned sz, expr * const * a_bits, expr * const * b_bits, expr_ref_vector & out_bits);
bool mk_const_case_multiplier(unsigned sz, expr * const * a_bits, expr * const * b_bits, expr_ref_vector & out_bits);
void mk_const_case_multiplier(bool is_a, unsigned i, unsigned sz, ptr_buffer<expr, 128>& a_bits, ptr_buffer<expr, 128>& b_bits, expr_ref_vector & out_bits);
bool is_bool_const(expr* e) const { return m().is_true(e) || m().is_false(e); }
void mk_abs(unsigned sz, expr * const * a_bits, expr_ref_vector & out_bits);
};

117
src/ast/rewriter/bit_blaster/bit_blaster_tpl_def.h
View file

@ -38,7 +38,7 @@ void bit_blaster_tpl<Cfg>::checkpoint() {
template<typename Cfg>
bool bit_blaster_tpl<Cfg>::is_numeral(unsigned sz, expr * const * bits) const {
for (unsigned i = 0; i < sz; i++)
if (!m().is_true(bits[i]) && !m().is_false(bits[i]))
if (!is_bool_const(bits[i]))
return false;
return true;
}
@ -158,30 +158,24 @@ void bit_blaster_tpl<Cfg>::mk_subtracter(unsigned sz, expr * const * a_bits, exp
template<typename Cfg>
void bit_blaster_tpl<Cfg>::mk_multiplier(unsigned sz, expr * const * a_bits, expr * const * b_bits, expr_ref_vector & out_bits) {
SASSERT(sz > 0);
if (!m_use_bcm) {
numeral n_a, n_b;
if (is_numeral(sz, a_bits, n_b))
std::swap(a_bits, b_bits);
if (is_minus_one(sz, b_bits)) {
mk_neg(sz, a_bits, out_bits);
return;
}
if (is_numeral(sz, a_bits, n_a)) {
n_a *= n_b;
num2bits(n_a, sz, out_bits);
return;
}
numeral n_a, n_b;
if (is_numeral(sz, a_bits, n_b))
std::swap(a_bits, b_bits);
if (is_minus_one(sz, b_bits)) {
mk_neg(sz, a_bits, out_bits);
return;
}
else {
numeral n_a, n_b;
if (is_numeral(sz, a_bits, n_a)) {
mk_const_multiplier(sz, a_bits, b_bits, out_bits);
return;
} else if (is_numeral(sz, b_bits, n_b)) {
mk_const_multiplier(sz, b_bits, a_bits, out_bits);
return;
}
if (is_numeral(sz, a_bits, n_a)) {
n_a *= n_b;
num2bits(n_a, sz, out_bits);
return;
}
if (mk_const_multiplier(sz, a_bits, b_bits, out_bits)) {
return;
}
if (mk_const_multiplier(sz, b_bits, a_bits, out_bits)) {
return;
}
if (!m_use_wtm) {
@ -1171,13 +1165,74 @@ void bit_blaster_tpl<Cfg>::mk_carry_save_adder(unsigned sz, expr * const * a_bit
}
template<typename Cfg>
void bit_blaster_tpl<Cfg>::mk_const_multiplier(unsigned sz, expr * const * a_bits, expr * const * b_bits, expr_ref_vector & out_bits) {
DEBUG_CODE({
numeral x;
SASSERT(is_numeral(sz, a_bits, x));
SASSERT(out_bits.empty());
});
bool bit_blaster_tpl<Cfg>::mk_const_case_multiplier(unsigned sz, expr * const * a_bits, expr * const * b_bits, expr_ref_vector & out_bits) {
unsigned nb = 0;
unsigned case_size = 1;
unsigned circuit_size = sz*sz*5;
for (unsigned i = 0; case_size < circuit_size && i < sz; ++i) {
if (!is_bool_const(a_bits[i])) {
case_size *= 2;
}
if (!is_bool_const(b_bits[i])) {
case_size *= 2;
}
}
if (case_size >= circuit_size) {
return false;
}
SASSERT(out_bits.empty());
ptr_buffer<expr, 128> na_bits;
na_bits.append(sz, a_bits);
ptr_buffer<expr, 128> nb_bits;
nb_bits.append(sz, b_bits);
mk_const_case_multiplier(true, 0, sz, na_bits, nb_bits, out_bits);
return false;
}
template<typename Cfg>
void bit_blaster_tpl<Cfg>::mk_const_case_multiplier(bool is_a, unsigned i, unsigned sz, ptr_buffer<expr, 128>& a_bits, ptr_buffer<expr, 128>& b_bits, expr_ref_vector & out_bits) {
while (is_a && i < sz && is_bool_const(a_bits[i])) ++i;
if (is_a && i == sz) { is_a = false; i = 0; }
while (!is_a && i < sz && is_bool_const(b_bits[i])) ++i;
if (i < sz) {
expr_ref_vector out1(m()), out2(m());
expr_ref x(m());
x = is_a?a_bits[i]:b_bits[i];
if (is_a) a_bits[i] = m().mk_true(); else b_bits[i] = m().mk_true();
mk_const_case_multiplier(is_a, i+1, sz, a_bits, b_bits, out1);
if (is_a) a_bits[i] = m().mk_false(); else b_bits[i] = m().mk_false();
mk_const_case_multiplier(is_a, i+1, sz, a_bits, b_bits, out2);
if (is_a) a_bits[i] = x; else b_bits[i] = x;
SASSERT(out_bits.empty());
for (unsigned j = 0; j < sz; ++j) {
out_bits.push_back(m().mk_ite(x, out1[j].get(), out2[j].get()));
}
}
else {
numeral n_a, n_b;
SASSERT(i == sz && !is_a);
VERIFY(is_numeral(sz, a_bits.c_ptr(), n_a));
VERIFY(is_numeral(sz, b_bits.c_ptr(), n_b));
n_a *= n_b;
num2bits(n_a, sz, out_bits);
}
}
template<typename Cfg>
bool bit_blaster_tpl<Cfg>::mk_const_multiplier(unsigned sz, expr * const * a_bits, expr * const * b_bits, expr_ref_vector & out_bits) {
numeral n_a;
if (!is_numeral(sz, a_bits, n_a)) {
return false;
}
SASSERT(out_bits.empty());
if (mk_const_case_multiplier(sz, a_bits, b_bits, out_bits)) {
return true;
}
if (!m_use_bcm) {
return false;
}
expr_ref_vector minus_b_bits(m()), tmp(m());
mk_neg(sz, b_bits, minus_b_bits);
@ -1255,4 +1310,6 @@ void bit_blaster_tpl<Cfg>::mk_const_multiplier(unsigned sz, expr * const * a_bit
TRACE("bit_blaster_tpl_booth", for (unsigned i=0; i<out_bits.size(); i++)
tout << "Booth encoding: " << mk_pp(out_bits[i].get(), m()) << "\n"; );
return true;
}