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/********************* */
/*! \file bv_to_bool.h
** \verbatim
** Original author: Liana Hadarean
** Major contributors: None.
** Minor contributors (to current version): None.
** This file is part of the CVC4 project.
** Copyright (c) 2009-2013 New York University and The University of Iowa
** See the file COPYING in the top-level source directory for licensing
** information.\endverbatim
**
** \brief Preprocessing pass that lifts bit-vectors of size 1 to booleans.
**
** Preprocessing pass that lifts bit-vectors of size 1 to booleans.
**/
#include "util/node_visitor.h"
#include "theory/bv/bv_to_bool.h"
using namespace std;
using namespace CVC4;
using namespace CVC4::theory;
using namespace CVC4::theory::bv;
void BvToBoolVisitor::addToCache(TNode bv_term, Node bool_term) {
Assert (!hasCache(bv_term));
Assert (bool_term.getType().isBoolean());
d_cache[bv_term] = bool_term;
}
Node BvToBoolVisitor::getCache(TNode bv_term) const {
Assert (hasCache(bv_term));
return d_cache.find(bv_term)->second;
}
bool BvToBoolVisitor::hasCache(TNode bv_term) const {
Assert (bv_term.getType().isBitVector());
return d_cache.find(bv_term) != d_cache.end();
}
void BvToBoolVisitor::start(TNode node) {}
bool BvToBoolVisitor::alreadyVisited(TNode current, TNode parent) {
return d_visited.find(current) != d_visited.end();
}
bool BvToBoolVisitor::isConvertibleToBool(TNode current) {
TypeNode type = current.getType();
if (current.getNumChildren() == 0 && type.isBitVector()) {
return type.getBitVectorSize() == 1;
}
if (current.getKind() == kind::NOT) {
current = current[0];
}
Kind kind = current.getKind();
// checking bit-vector kinds
if (kind == kind::BITVECTOR_OR ||
kind == kind::BITVECTOR_AND ||
kind == kind::BITVECTOR_XOR ||
kind == kind::BITVECTOR_NOT ||
// kind == kind::BITVECTOR_PLUS ||
// kind == kind::BITVECTOR_SUB ||
// kind == kind::BITVECTOR_NEG ||
kind == kind::BITVECTOR_ULT ||
kind == kind::BITVECTOR_ULE ||
kind == kind::EQUAL) {
return current[0].getType().getBitVectorSize() == 1;
}
if (kind == kind::ITE &&
type.isBitVector()) {
return type.getBitVectorSize() == 1;
}
return false;
}
Node BvToBoolVisitor::convertToBool(TNode current) {
Kind kind = current.getKind();
if (kind == kind::BITVECTOR_ULT) {
TNode a = getCache(current[0]);
TNode b = getCache(current[1]);
Node a_eq_0 = utils::mkNode(kind::EQUAL, a, d_zero);
Node b_eq_1 = utils::mkNode(kind::EQUAL, b, d_one);
Node new_current = utils::mkNode(kind::AND, a_eq_0, b_eq_1);
return new_current;
}
if (kind == kind::BITVECTOR_ULE) {
TNode a = getCache(current[0]);
TNode b = getCache(current[1]);
Node a_eq_0 = utils::mkNode(kind::EQUAL, a, d_zero);
Node b_eq_1 = utils::mkNode(kind::EQUAL, b, d_one);
Node a_lt_b = utils::mkNode(kind::AND, a_eq_0, b_eq_1);
Node a_eq_b = utils::mkNode(kind::EQUAL, a, b);
Node new_current = utils::mkNode(kind::OR, a_lt_b, a_eq_b);
return new_current;
}
Kind new_kind;
switch (kind) {
case kind::BITVECTOR_OR :
new_kind = kind::OR;
case kind::BITVECTOR_AND:
new_kind = kind::AND;
case kind::BITVECTOR_XOR:
new_kind = kind::XOR;
case kind::BITVECTOR_NOT:
new_kind = kind::NOT;
case kind::BITVECTOR_ULT:
default:
Unreachable();
}
NodeBuilder<> builder(new_kind);
for (unsigned i = 0; i < current.getNumChildren(); ++i) {
builder << getCache(current[i]);
}
return builder;
}
void BvToBoolVisitor::visit(TNode current, TNode parent) {
Assert (!alreadyVisited(current, parent));
d_visited.insert(current);
if (current.getNumChildren() == 0 &&
isConvertibleToBool(current)) {
Node bool_current;
if (current.getKind() == kind::CONST_BITVECTOR) {
bool_current = current == d_one? utils::mkTrue() : utils::mkFalse();
} else {
bool_current = utils::mkNode(kind::EQUAL, current, d_one);
}
addToCache(current, bool_current);
return;
}
// if it has more than one child
if (isConvertibleToBool(current)) {
Node bool_current = convertToBool(current);
addToCache(current, bool_current);
} else {
NodeBuilder<> builder(current.getKind());
for (unsigned i = 0; i < current.getNumChildren(); ++i) {
Node converted = getCache(current[i]);
if (converted.getType() == current[i].getType()) {
builder << converted;
} else {
builder << current[i];
}
}
Node result = builder;
addToCache(current, result);
}
}
BvToBoolVisitor::return_type BvToBoolVisitor::done(TNode node) {
Assert (hasCache(node));
return getCache(node);
}
Node BvToBoolPreprocessor::liftBoolToBV(TNode assertion) {
Node result = NodeVisitor<BvToBoolVisitor>::run(d_visitor, assertion);
return result;
}
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