cprover
boolbv_cond.cpp
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1 /*******************************************************************\
2 
3 Module:
4 
5 Author: Daniel Kroening, kroening@kroening.com
6 
7 \*******************************************************************/
8 
9 #include "boolbv.h"
10 
11 #include <util/invariant.h>
12 
14 {
15  const exprt::operandst &operands=expr.operands();
16 
17  std::size_t width=boolbv_width(expr.type());
18 
19  if(width==0)
20  return conversion_failed(expr);
21 
22  bvt bv;
23 
24  DATA_INVARIANT(operands.size() >= 2, "cond must have at least two operands");
25 
27  operands.size() % 2 == 0, "number of cond operands must be even");
28 
29  if(prop.has_set_to())
30  {
31  bool condition=true;
32  literalt previous_cond=const_literal(false);
33  literalt cond_literal=const_literal(false);
34 
35  // make it free variables
36  bv = prop.new_variables(width);
37 
38  forall_operands(it, expr)
39  {
40  if(condition)
41  {
42  cond_literal=convert(*it);
43  cond_literal=prop.land(!previous_cond, cond_literal);
44 
45  previous_cond=prop.lor(previous_cond, cond_literal);
46  }
47  else
48  {
49  const bvt &op = convert_bv(*it, bv.size());
50 
51  literalt value_literal=bv_utils.equal(bv, op);
52 
53  prop.l_set_to_true(prop.limplies(cond_literal, value_literal));
54  }
55 
56  condition=!condition;
57  }
58  }
59  else
60  {
61  bv.resize(width);
62 
63  // functional version -- go backwards
64  for(std::size_t i=expr.operands().size(); i!=0; i-=2)
65  {
66  INVARIANT(
67  i >= 2,
68  "since the number of operands is even if i is nonzero it must be "
69  "greater than two");
70  const exprt &cond=expr.operands()[i-2];
71  const exprt &value=expr.operands()[i-1];
72 
73  literalt cond_literal=convert(cond);
74 
75  const bvt &op = convert_bv(value, bv.size());
76 
77  for(std::size_t j = 0; j < bv.size(); j++)
78  bv[j] = prop.lselect(cond_literal, op[j], bv[j]);
79  }
80  }
81 
82  return bv;
83 }
boolbvt::convert_cond
virtual bvt convert_cond(const cond_exprt &)
Definition: boolbv_cond.cpp:13
propt::new_variables
virtual bvt new_variables(std::size_t width)
generates a bitvector of given width with new variables
Definition: prop.cpp:20
bvt
std::vector< literalt > bvt
Definition: literal.h:201
invariant.h
exprt
Base class for all expressions.
Definition: expr.h:54
propt::lor
virtual literalt lor(literalt a, literalt b)=0
propt::l_set_to_true
void l_set_to_true(literalt a)
Definition: prop.h:52
propt::land
virtual literalt land(literalt a, literalt b)=0
exprt::type
typet & type()
Return the type of the expression.
Definition: expr.h:82
boolbvt::conversion_failed
void conversion_failed(const exprt &expr, bvt &bv)
Definition: boolbv.h:126
DATA_INVARIANT
#define DATA_INVARIANT(CONDITION, REASON)
This condition should be used to document that assumptions that are made on goto_functions,...
Definition: invariant.h:511
propt::limplies
virtual literalt limplies(literalt a, literalt b)=0
boolbvt::boolbv_width
virtual std::size_t boolbv_width(const typet &type) const
Definition: boolbv.h:96
forall_operands
#define forall_operands(it, expr)
Definition: expr.h:18
const_literal
literalt const_literal(bool value)
Definition: literal.h:188
exprt::operandst
std::vector< exprt > operandst
Definition: expr.h:56
boolbvt::convert_bv
virtual const bvt & convert_bv(const exprt &expr, const optionalt< std::size_t > expected_width=nullopt)
Convert expression to vector of literalts, using an internal cache to speed up conversion if availabl...
Definition: boolbv.cpp:47
prop_conv_solvert::convert
literalt convert(const exprt &expr) override
Convert a Boolean expression and return the corresponding literal.
Definition: prop_conv_solver.cpp:154
cond_exprt
this is a parametric version of an if-expression: it returns the value of the first case (using the o...
Definition: std_expr.h:2950
boolbvt::bv_utils
bv_utilst bv_utils
Definition: boolbv.h:111
literalt
Definition: literal.h:26
propt::has_set_to
virtual bool has_set_to() const
Definition: prop.h:81
boolbv.h
exprt::operands
operandst & operands()
Definition: expr.h:96
INVARIANT
#define INVARIANT(CONDITION, REASON)
This macro uses the wrapper function 'invariant_violated_string'.
Definition: invariant.h:424
bv_utilst::equal
literalt equal(const bvt &op0, const bvt &op1)
Bit-blasting ID_equal and use in other encodings.
Definition: bv_utils.cpp:1105
propt::lselect
virtual literalt lselect(literalt a, literalt b, literalt c)=0
prop_conv_solvert::prop
propt & prop
Definition: prop_conv_solver.h:128