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Starting to work on trailing 0 analysis.
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mikolas
Mikolas Janota
parent
493b86eca7
commit
c7f1746321
5 changed files with 330 additions and 1 deletions
282
src/ast/rewriter/bv_trailing.cpp
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282
src/ast/rewriter/bv_trailing.cpp
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/*++
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Copyright (c) 2016 Microsoft Corporation
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Module Name:
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bv_trailing.cpp
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Abstract:
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Author:
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Mikolas Janota (MikolasJanota)
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Revision History:
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--*/
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#include"bv_trailing.h"
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#include"bv_decl_plugin.h"
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#include"ast_smt2_pp.h"
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#define TRAILING_DEPTH 4
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struct bv_trailing::imp {
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typedef rational numeral;
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bv_util m_util;
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ast_manager& m_m;
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mk_extract_proc& m_mk_extract;
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imp(ast_manager& m, mk_extract_proc& mk_extract)
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: m_m(m)
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, m_util(m)
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, m_mk_extract(mk_extract)
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{ }
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virtual ~imp() { }
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ast_manager & m() const { return m_util.get_manager(); }
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br_status eq_remove_trailing(expr * e1, expr * e2, expr_ref& result) {
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TRACE("bv-trailing", tout << mk_ismt2_pp(e1, m()) << "\n=\n" << mk_ismt2_pp(e2, m()) << "\n";);
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SASSERT(m_util.is_bv(e1) && m_util.is_bv(e2));
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SASSERT(m_util.get_bv_size(e1) == m_util.get_bv_size(e2));
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unsigned max1, min1, max2, min2;
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count_trailing(e1, min1, max1, TRAILING_DEPTH);
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count_trailing(e2, min2, max2, TRAILING_DEPTH);
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if (min1 > max2 || min2 > max2) {
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result = m().mk_false();
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return BR_DONE;
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}
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const unsigned min = std::min(min1, min2);
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if (min == 0) {
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result = m().mk_eq(e1, e2);
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return BR_FAILED;
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}
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const unsigned sz = m_util.get_bv_size(e1);
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if (min == sz) { // unlikely but we check anyhow for safety
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result = m().mk_true();
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return BR_DONE;
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}
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expr_ref out1(m());
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expr_ref out2(m());
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remove_trailing(e1, min, out1, TRAILING_DEPTH);
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remove_trailing(e2, min, out2, TRAILING_DEPTH);
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result = m().mk_eq(out1, out2);
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return BR_REWRITE2;
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}
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unsigned remove_trailing_mul(app * a, unsigned n, expr_ref& result, unsigned depth) {
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SASSERT(m_util.is_bv_mul(a));
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if (depth <= 1) {
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result = a;
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return 0;
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}
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const unsigned num = a->get_num_args();
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if (!num) return 0;
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expr_ref tmp(m());
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expr * const coefficient = a->get_arg(0);
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const unsigned retv = remove_trailing(coefficient, n, tmp, depth - 1);
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SASSERT(retv <= n);
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if (retv == 0) {
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result = a;
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return 0;
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}
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expr_ref_vector new_args(m());
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numeral c_val;
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unsigned c_sz;
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if (!m_util.is_numeral(tmp, c_val, c_sz) || !c_val.is_one())
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new_args.push_back(tmp);
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const unsigned sz = m_util.get_bv_size(coefficient);
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const unsigned new_sz = sz - retv;
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if (!new_sz) {
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result = NULL;
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return retv;
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}
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SASSERT(m_util.get_bv_size(tmp) == new_sz);
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for (unsigned i = 1; i < num; i++) {
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expr * const curr = a->get_arg(i);
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new_args.push_back(m_mk_extract(new_sz - 1, 0, curr));
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}
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switch (new_args.size()) {
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case 0: result = m_util.mk_numeral(1, new_sz); break;
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case 1: result = new_args.get(0); break;
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default: result = m().mk_app(m_util.get_fid(), OP_BMUL, new_args.size(), new_args.c_ptr());
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}
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return retv;
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}
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unsigned remove_trailing_concat(app * a, unsigned n, expr_ref& result, unsigned depth) {
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SASSERT(m_util.is_concat(a));
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if (depth <= 1) {
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result = a;
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return 0;
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}
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unsigned num = a->get_num_args();
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unsigned retv = 0;
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unsigned i = num;
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expr_ref new_last(NULL, m());
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while (i && retv < n) {
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i--;
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expr * const curr = a->get_arg(i);
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const unsigned cur_rm = remove_trailing(curr, n, new_last, depth - 1);
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const unsigned curr_sz = m_util.get_bv_size(curr);
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retv += cur_rm;
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if (cur_rm < curr_sz) break;
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}
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if (retv == 0) {
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result = a;
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return 0;
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}
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if (!i) {
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SASSERT(new_last.get() == NULL);
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result = NULL;
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return retv;
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}
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expr_ref_vector new_args(m());
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for (size_t j=0; j<i;++j)
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new_args.push_back(a->get_arg(j));
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if (new_last.get()) new_args.push_back(new_last);
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result = m_util.mk_concat(new_args.size(), new_args.c_ptr());
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return retv;
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}
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unsigned remove_trailing(size_t max_rm, numeral& a) {
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numeral two(2);
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unsigned retv = 0;
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while (max_rm && a.is_even()) {
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div(a, two, a);
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++retv;
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--max_rm;
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}
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return retv;
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}
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unsigned remove_trailing(expr * e, unsigned n, expr_ref& result, unsigned depth) {
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const unsigned retv = remove_trailing_core(e, n, result, depth);
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TRACE("bv-trailing", tout << mk_ismt2_pp(e, m()) << "\n" <<
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"--->" << mk_ismt2_pp(result.get(), m()) << "\n";);
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return retv;
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}
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unsigned remove_trailing_core(expr * e, unsigned n, expr_ref& result, unsigned depth) {
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SASSERT(m_util.is_bv(e));
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if (!depth) return 0;
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if (n == 0) return 0;
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unsigned sz;
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unsigned retv = 0;
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numeral e_val;
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if (m_util.is_numeral(e, e_val, sz)) {
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retv = remove_trailing(n, e_val);
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const unsigned new_sz = sz - retv;
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result = new_sz ? (retv ? m_util.mk_numeral(e_val, new_sz) : e) : NULL;
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return retv;
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}
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if (m_util.is_bv_mul(e))
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return remove_trailing_mul(to_app(e), n, result, depth);
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if (m_util.is_concat(e))
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return remove_trailing_concat(to_app(e), n, result, depth);
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return 0;
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}
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void count_trailing(expr * e, unsigned& min, unsigned& max, unsigned depth) {
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SASSERT(e && m_util.is_bv(e));
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count_trailing_core(e, min, max, depth);
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TRACE("bv-trailing", tout << mk_ismt2_pp(e, m()) << "\n:" << min << " - " << max << "\n";);
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SASSERT(min <= max);
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SASSERT(max <= m_util.get_bv_size(e));
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}
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void count_trailing_concat(app * a, unsigned& min, unsigned& max, unsigned depth) {
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if (depth <= 1) {
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min = 0;
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max = m_util.get_bv_size(a);
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}
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max = min = 0; // treat empty concat as the empty string
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unsigned num = a->get_num_args();
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bool update_min = true;
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bool update_max = true;
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unsigned tmp_min, tmp_max;
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while (num-- && update_max) {
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expr * const curr = a->get_arg(num);
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const unsigned curr_sz = m_util.get_bv_size(curr);
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count_trailing(curr, tmp_min, tmp_max, depth - 1);
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SASSERT(curr_sz != tmp_min || curr_sz == tmp_max);
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max += tmp_max;
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if (update_min) min += tmp_min;
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// continue updating only if eaten away completely
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update_min &= curr_sz == tmp_min;
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update_max &= curr_sz == tmp_max;
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}
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}
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void count_trailing_mul(app * a, unsigned& min, unsigned& max, unsigned depth) {
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if (depth <= 1) {
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min = 0;
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max = m_util.get_bv_size(a);
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}
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const unsigned num = a->get_num_args();
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if (!num) {
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max = min = 0; // treat empty multiplication as 1
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return;
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}
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// assume that numerals are pushed in the front, count only for the first element
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expr * const curr = a->get_arg(0);
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unsigned tmp_max;
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count_trailing(curr, min, tmp_max, depth - 1);
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max = num == 1 ? tmp_max : m_util.get_bv_size(a);
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return;
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}
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void count_trailing_core(expr * e, unsigned& min, unsigned& max, unsigned depth) {
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if (!depth) {
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min = 0;
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max = m_util.get_bv_size(e);
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return;
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}
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unsigned sz;
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numeral e_val;
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if (m_util.is_numeral(e, e_val, sz)) {
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min = max = 0;
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numeral two(2);
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while (sz-- && e_val.is_even()) {
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++max;
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++min;
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div(e_val, two, e_val);
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}
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return;
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}
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if (m_util.is_bv_mul(e)) count_trailing_mul(to_app(e), min, max, depth);
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else if (m_util.is_concat(e)) count_trailing_concat(to_app(e), min, max, depth);
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else {
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min = 0;
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max = m_util.get_bv_size(e);
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}
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}
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};
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bv_trailing::bv_trailing(ast_manager& m, mk_extract_proc& mk_extract) {
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m_imp = alloc(imp, m, mk_extract);
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}
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bv_trailing::~bv_trailing() {
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if (m_imp) dealloc(m_imp);
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}
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void bv_trailing::count_trailing(expr * e, unsigned& min, unsigned& max, unsigned depth) {
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m_imp->count_trailing(e, min, max, depth);
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}
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br_status bv_trailing::eq_remove_trailing(expr * e1, expr * e2, expr_ref& result) {
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return m_imp->eq_remove_trailing(e1, e2, result);
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}
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unsigned bv_trailing::remove_trailing(expr * e, unsigned n, expr_ref& result, unsigned depth) {
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return m_imp->remove_trailing(e, n, result, depth);
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}
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