cprover
boolbv_byte_update.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 <iostream>
12 #include <cassert>
13 
14 #include <util/arith_tools.h>
15 #include <util/byte_operators.h>
16 
17 #include "bv_endianness_map.h"
18 
20 {
21  if(expr.operands().size()!=3)
22  throw "byte_update takes three operands";
23 
24  const exprt &op=expr.op0();
25  const exprt &offset_expr=expr.offset();
26  const exprt &value=expr.value();
27 
29  expr.id() == ID_byte_update_little_endian ||
30  expr.id() == ID_byte_update_big_endian);
31  const bool little_endian = expr.id() == ID_byte_update_little_endian;
32 
33  bvt bv=convert_bv(op);
34 
35  const bvt &value_bv=convert_bv(value);
36  std::size_t update_width=value_bv.size();
37  std::size_t byte_width=8;
38 
39  if(update_width>bv.size())
40  update_width=bv.size();
41 
42  // see if the byte number is constant
43 
44  mp_integer index;
45  if(!to_integer(offset_expr, index))
46  {
47  // yes!
48  mp_integer offset=index*8;
49 
50  if(offset+update_width>mp_integer(bv.size()) || offset<0)
51  {
52  // out of bounds
53  }
54  else
55  {
56  if(little_endian)
57  {
58  for(std::size_t i=0; i<update_width; i++)
59  bv[integer2size_t(offset+i)]=value_bv[i];
60  }
61  else
62  {
63  bv_endianness_mapt map_op(op.type(), false, ns, boolbv_width);
64  bv_endianness_mapt map_value(value.type(), false, ns, boolbv_width);
65 
66  std::size_t offset_i=integer2unsigned(offset);
67 
68  for(std::size_t i=0; i<update_width; i++)
69  {
70  size_t index_op=map_op.map_bit(offset_i+i);
71  size_t index_value=map_value.map_bit(i);
72 
73  assert(index_op<bv.size());
74  assert(index_value<value_bv.size());
75 
76  bv[index_op]=value_bv[index_value];
77  }
78  }
79  }
80 
81  return bv;
82  }
83 
84  // byte_update with variable index
85  for(std::size_t offset=0; offset<bv.size(); offset+=byte_width)
86  {
87  // index condition
89  equality.lhs()=offset_expr;
90  equality.rhs()=from_integer(offset/byte_width, offset_expr.type());
91  literalt equal=convert(equality);
92 
93  bv_endianness_mapt map_op(op.type(), little_endian, ns, boolbv_width);
94  bv_endianness_mapt map_value(value.type(), little_endian, ns, boolbv_width);
95 
96  for(std::size_t bit=0; bit<update_width; bit++)
97  if(offset+bit<bv.size())
98  {
99  std::size_t bv_o=map_op.map_bit(offset+bit);
100  std::size_t value_bv_o=map_value.map_bit(bit);
101 
102  bv[bv_o]=prop.lselect(equal, value_bv[value_bv_o], bv[bv_o]);
103  }
104  }
105 
106  return bv;
107 }
BigInt mp_integer
Definition: mp_arith.h:22
literalt convert(const exprt &expr) override
Definition: prop_conv.cpp:162
exprt & op0()
Definition: expr.h:72
boolbv_widtht boolbv_width
Definition: boolbv.h:90
typet & type()
Definition: expr.h:56
equality
Definition: std_expr.h:1354
const irep_idt & id() const
Definition: irep.h:259
Expression classes for byte-level operators.
virtual const bvt & convert_bv(const exprt &expr)
Definition: boolbv.cpp:116
#define PRECONDITION(CONDITION)
Definition: invariant.h:242
const namespacet & ns
Map bytes according to the configured endianness.
unsigned integer2unsigned(const mp_integer &n)
Definition: mp_arith.cpp:203
virtual bvt convert_byte_update(const byte_update_exprt &expr)
virtual literalt equality(const exprt &e1, const exprt &e2)
Definition: equality.cpp:17
Base class for all expressions.
Definition: expr.h:42
TO_BE_DOCUMENTED.
bool to_integer(const exprt &expr, mp_integer &int_value)
Definition: arith_tools.cpp:17
size_t map_bit(size_t bit) const
virtual literalt lselect(literalt a, literalt b, literalt c)=0
std::size_t integer2size_t(const mp_integer &n)
Definition: mp_arith.cpp:195
operandst & operands()
Definition: expr.h:66
constant_exprt from_integer(const mp_integer &int_value, const typet &type)
std::vector< literalt > bvt
Definition: literal.h:200