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Re-factoring and comments in bv_trailing.

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mikolas 2016-04-04 20:17:48 +01:00 • committed by Mikolas Janota
parent 248feace34
commit 9ba5bbfd33
3 changed files with 89 additions and 63 deletions
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2
src/ast/rewriter/bv_rewriter.cpp
View file

@ -2094,7 +2094,7 @@ br_status bv_rewriter::mk_eq_core(expr * lhs, expr * rhs, expr_ref & result) {
if (m_trailing) {
st = m_rm_trailing.eq_remove_trailing(lhs, rhs, result);
//m_rm_trailing.reset_cache();
m_rm_trailing.reset_cache(1 << 12);
if (st != BR_FAILED) {
TRACE("eq_remove_trailing", tout << mk_ismt2_pp(lhs, m()) << "\n=\n" << mk_ismt2_pp(rhs, m()) << "\n----->\n" << mk_ismt2_pp(result, m()) << "\n";);
return st;

132
src/ast/rewriter/bv_trailing.cpp
View file

@ -18,6 +18,8 @@
#include"bv_decl_plugin.h"
#include"ast_smt2_pp.h"
// This is not very elegant at this point, this number shouldn't be too big,
// give up analysis after TRAILING_DEPTH depth.
#define TRAILING_DEPTH 4
struct bv_trailing::imp {
@ -35,38 +37,11 @@ struct bv_trailing::imp {
{ }
virtual ~imp() {
reset_cache();
reset_cache(0);
}
ast_manager & m() const { return m_util.get_manager(); }
void cache(unsigned depth, expr * e, unsigned min, unsigned max) {
SASSERT(depth <= TRAILING_DEPTH);
m().inc_ref(e);
m_count_cache[depth].insert(e, std::make_pair(min, max));
TRACE("bv-trailing", tout << "caching@" << depth <<": " << mk_ismt2_pp(e, m()) << '[' << m_util.get_bv_size(e) << "]\n: " << min << '-' << max << "\n";);
}
bool is_cached(unsigned depth, expr * e, unsigned& min, unsigned& max) {
SASSERT(depth <= TRAILING_DEPTH);
const map::obj_map_entry * const oe = m_count_cache[depth].find_core(e);
if (oe == NULL) return false;
min = oe->get_data().m_value.first;
max = oe->get_data().m_value.second;
TRACE("bv-trailing", tout << "cached@" << depth << ": " << mk_ismt2_pp(e, m()) << '[' << m_util.get_bv_size(e) << "]\n: " << min << '-' << max << "\n";);
return true;
}
void reset_cache() {
for (unsigned i = 0; i <= TRAILING_DEPTH; ++i) {
map::iterator it = m_count_cache[i].begin();
map::iterator end = m_count_cache[i].end();
for (; it != end; ++it) m().dec_ref(it->m_key);
m_count_cache[i].reset();
}
}
br_status eq_remove_trailing(expr * e1, expr * e2, expr_ref& result) {
TRACE("bv-trailing", tout << mk_ismt2_pp(e1, m()) << "\n=\n" << mk_ismt2_pp(e2, m()) << "\n";);
SASSERT(m_util.is_bv(e1) && m_util.is_bv(e2));
@ -74,28 +49,51 @@ struct bv_trailing::imp {
unsigned max1, min1, max2, min2;
count_trailing(e1, min1, max1, TRAILING_DEPTH);
count_trailing(e2, min2, max2, TRAILING_DEPTH);
if (min1 > max2 || min2 > max1) {
if (min1 > max2 || min2 > max1) { // bounds have empty intersection
result = m().mk_false();
return BR_DONE;
}
const unsigned min = std::min(min1, min2);
if (min == 0) {
const unsigned min = std::min(min1, min2); // remove the minimum of the two lower bounds
if (min == 0) { // nothing to remove
result = m().mk_eq(e1, e2);
return BR_FAILED;
}
const unsigned sz = m_util.get_bv_size(e1);
if (min == sz) { // unlikely but we check anyhow for safety
if (min == sz) { // everything removed, unlikely but we check anyhow for safety
result = m().mk_true();
return BR_DONE;
}
expr_ref out1(m());
expr_ref out2(m());
remove_trailing(e1, min, out1, TRAILING_DEPTH);
remove_trailing(e2, min, out2, TRAILING_DEPTH);
result = m().mk_eq(out1, out2);
return BR_REWRITE2;
const unsigned rm1 = remove_trailing(e1, min, out1, TRAILING_DEPTH);
const unsigned rm2 = remove_trailing(e2, min, out2, TRAILING_DEPTH);
SASSERT(rm1 == min && rm2 == min);
const bool are_eq = m().are_equal(out1, out2);
result = are_eq ? m().mk_true() : m().mk_eq(out1, out2);
return are_eq ? BR_DONE : BR_REWRITE2;
}
// This routine needs to be implemented carefully so that whenever it
// returns a lower bound on trailing zeros min, the routine remove_trailing
// must be capable of removing at least that many zeros from the expression.
void count_trailing(expr * e, unsigned& min, unsigned& max, unsigned depth) {
SASSERT(e && m_util.is_bv(e));
if (is_cached(depth, e, min, max)) return;
count_trailing_core(e, min, max, depth);
TRACE("bv-trailing", tout << mk_ismt2_pp(e, m()) << "\n:" << min << " - " << max << "\n";);
SASSERT(min <= max);
SASSERT(max <= m_util.get_bv_size(e));
cache(depth, e, min, max); // store result into the cache
}
unsigned remove_trailing(expr * e, unsigned n, expr_ref& result, unsigned depth) {
const unsigned retv = remove_trailing_core(e, n, result, depth);
CTRACE("bv-trailing", result.get(), tout << mk_ismt2_pp(e, m()) << "\n--->\n" << mk_ismt2_pp(result.get(), m()) << "\n";);
CTRACE("bv-trailing", !result.get(), tout << mk_ismt2_pp(e, m()) << "\n---> [EMPTY]\n";);
return retv;
}
// assumes that count_trailing gives me a lower bound, which we can also remove from each summand
unsigned remove_trailing_add(app * a, unsigned n, expr_ref& result, unsigned depth) {
SASSERT(m_util.is_bv_add(a));
const unsigned num = a->get_num_args();
@ -104,7 +102,7 @@ struct bv_trailing::imp {
return 0;
}
unsigned min, max;
count_trailing(a, min, max, depth);
count_trailing(a, min, max, depth); // caching is important here
const unsigned to_rm = std::min(min, n);
if (to_rm == 0) {
result = a;
@ -177,7 +175,7 @@ struct bv_trailing::imp {
result = a;
return 0;
}
unsigned num = a->get_num_args();
const unsigned num = a->get_num_args();
unsigned retv = 0;
unsigned i = num;
expr_ref new_last(NULL, m());
@ -221,13 +219,6 @@ struct bv_trailing::imp {
return retv;
}
unsigned remove_trailing(expr * e, unsigned n, expr_ref& result, unsigned depth) {
const unsigned retv = remove_trailing_core(e, n, result, depth);
CTRACE("bv-trailing", result.get(), tout << mk_ismt2_pp(e, m()) << "\n--->\n" << mk_ismt2_pp(result.get(), m()) << "\n";);
CTRACE("bv-trailing", !result.get(), tout << mk_ismt2_pp(e, m()) << "\n---> [EMPTY]\n";);
return retv;
}
unsigned remove_trailing_core(expr * e, unsigned n, expr_ref& result, unsigned depth) {
SASSERT(m_util.is_bv(e));
if (!depth) return 0;
@ -250,16 +241,6 @@ struct bv_trailing::imp {
return 0;
}
void count_trailing(expr * e, unsigned& min, unsigned& max, unsigned depth) {
if (is_cached(depth, e, min, max))
return;
SASSERT(e && m_util.is_bv(e));
count_trailing_core(e, min, max, depth);
TRACE("bv-trailing", tout << mk_ismt2_pp(e, m()) << "\n:" << min << " - " << max << "\n";);
SASSERT(min <= max);
SASSERT(max <= m_util.get_bv_size(e));
cache(depth, e, min, max); // store result into the cache
}
void count_trailing_concat(app * a, unsigned& min, unsigned& max, unsigned depth) {
if (depth <= 1) {
@ -352,6 +333,35 @@ struct bv_trailing::imp {
max = m_util.get_bv_size(e);
}
}
void cache(unsigned depth, expr * e, unsigned min, unsigned max) {
SASSERT(depth <= TRAILING_DEPTH);
m().inc_ref(e);
m_count_cache[depth].insert(e, std::make_pair(min, max));
TRACE("bv-trailing", tout << "caching@" << depth <<": " << mk_ismt2_pp(e, m()) << '[' << m_util.get_bv_size(e) << "]\n: " << min << '-' << max << "\n";);
}
bool is_cached(unsigned depth, expr * e, unsigned& min, unsigned& max) {
SASSERT(depth <= TRAILING_DEPTH);
const map::obj_map_entry * const oe = m_count_cache[depth].find_core(e);
if (oe == NULL) return false;
min = oe->get_data().m_value.first;
max = oe->get_data().m_value.second;
TRACE("bv-trailing", tout << "cached@" << depth << ": " << mk_ismt2_pp(e, m()) << '[' << m_util.get_bv_size(e) << "]\n: " << min << '-' << max << "\n";);
return true;
}
void reset_cache(unsigned condition) {
for (unsigned i = 0; i <= TRAILING_DEPTH; ++i) {
if (m_count_cache[i].size() < condition) continue;
map::iterator it = m_count_cache[i].begin();
map::iterator end = m_count_cache[i].end();
for (; it != end; ++it) m().dec_ref(it->m_key);
m_count_cache[i].reset();
}
}
};
bv_trailing::bv_trailing(mk_extract_proc& mk_extract) {
@ -366,10 +376,14 @@ br_status bv_trailing::eq_remove_trailing(expr * e1, expr * e2, expr_ref& resul
return m_imp->eq_remove_trailing(e1, e2, result);
}
unsigned bv_trailing::remove_trailing(expr * e, unsigned n, expr_ref& result, unsigned depth) {
return m_imp->remove_trailing(e, n, result, depth);
void bv_trailing::count_trailing(expr * e, unsigned& min, unsigned& max) {
m_imp->count_trailing(e, min, max, TRAILING_DEPTH);
}
void bv_trailing::reset_cache() {
m_imp->reset_cache();
unsigned bv_trailing::remove_trailing(expr * e, unsigned n, expr_ref& result) {
return m_imp->remove_trailing(e, n, result, TRAILING_DEPTH);
}
void bv_trailing::reset_cache(unsigned condition) {
m_imp->reset_cache(condition);
}

18
src/ast/rewriter/bv_trailing.h
View file

@ -7,6 +7,8 @@
Abstract:
A utility to count trailing zeros of an expression. Treats 2x and x++0 equivalently.
Author:
@ -23,10 +25,20 @@ class bv_trailing {
public:
bv_trailing(mk_extract_proc& ep);
virtual ~bv_trailing();
void count_trailing(expr * e, unsigned& min, unsigned& max, unsigned depth);
public:
// Remove trailing zeros from both sides of an equality (might give False).
br_status eq_remove_trailing(expr * e1, expr * e2, expr_ref& result);
unsigned remove_trailing(expr * e, unsigned n, expr_ref& result, unsigned depth);
void reset_cache();
// Gives a lower and upper bound on trailing zeros in e.
void count_trailing(expr * e, unsigned& min, unsigned& max);
// Attempts removing n trailing zeros from e. Returns how many were successfully removed.
// We're assuming that it can remove at least as many zeros as min returned by count_training.
// Removing the bit-width of e, sets result to NULL.
unsigned remove_trailing(expr * e, unsigned n, expr_ref& result);
// Reset cache(s) if it exceeded size condition.
void reset_cache(unsigned condition);
protected:
struct imp;
imp * m_imp;