1//===- ConstantRange.h - Represent a range ----------------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// Represent a range of possible values that may occur when the program is run
11// for an integral value.  This keeps track of a lower and upper bound for the
12// constant, which MAY wrap around the end of the numeric range.  To do this, it
13// keeps track of a [lower, upper) bound, which specifies an interval just like
14// STL iterators.  When used with boolean values, the following are important
15// ranges: :
16//
17//  [F, F) = {}     = Empty set
18//  [T, F) = {T}
19//  [F, T) = {F}
20//  [T, T) = {F, T} = Full set
21//
22// The other integral ranges use min/max values for special range values. For
23// example, for 8-bit types, it uses:
24// [0, 0)     = {}       = Empty set
25// [255, 255) = {0..255} = Full Set
26//
27// Note that ConstantRange can be used to represent either signed or
28// unsigned ranges.
29//
30//===----------------------------------------------------------------------===//
31
32#ifndef LLVM_IR_CONSTANTRANGE_H
33#define LLVM_IR_CONSTANTRANGE_H
34
35#include "llvm/ADT/APInt.h"
36#include "llvm/IR/InstrTypes.h"
37#include "llvm/Support/DataTypes.h"
38
39namespace llvm {
40
41/// This class represents a range of values.
42///
43class ConstantRange {
44  APInt Lower, Upper;
45
46  // If we have move semantics, pass APInts by value and move them into place.
47  typedef APInt APIntMoveTy;
48
49public:
50  /// Initialize a full (the default) or empty set for the specified bit width.
51  ///
52  explicit ConstantRange(uint32_t BitWidth, bool isFullSet = true);
53
54  /// Initialize a range to hold the single specified value.
55  ///
56  ConstantRange(APIntMoveTy Value);
57
58  /// @brief Initialize a range of values explicitly. This will assert out if
59  /// Lower==Upper and Lower != Min or Max value for its type. It will also
60  /// assert out if the two APInt's are not the same bit width.
61  ConstantRange(APIntMoveTy Lower, APIntMoveTy Upper);
62
63  /// Produce the smallest range such that all values that may satisfy the given
64  /// predicate with any value contained within Other is contained in the
65  /// returned range.  Formally, this returns a superset of
66  /// 'union over all y in Other . { x : icmp op x y is true }'.  If the exact
67  /// answer is not representable as a ConstantRange, the return value will be a
68  /// proper superset of the above.
69  ///
70  /// Example: Pred = ult and Other = i8 [2, 5) returns Result = [0, 4)
71  static ConstantRange makeAllowedICmpRegion(CmpInst::Predicate Pred,
72                                             const ConstantRange &Other);
73
74  /// Produce the largest range such that all values in the returned range
75  /// satisfy the given predicate with all values contained within Other.
76  /// Formally, this returns a subset of
77  /// 'intersection over all y in Other . { x : icmp op x y is true }'.  If the
78  /// exact answer is not representable as a ConstantRange, the return value
79  /// will be a proper subset of the above.
80  ///
81  /// Example: Pred = ult and Other = i8 [2, 5) returns [0, 2)
82  static ConstantRange makeSatisfyingICmpRegion(CmpInst::Predicate Pred,
83                                                const ConstantRange &Other);
84
85  /// Return the lower value for this range.
86  ///
87  const APInt &getLower() const { return Lower; }
88
89  /// Return the upper value for this range.
90  ///
91  const APInt &getUpper() const { return Upper; }
92
93  /// Get the bit width of this ConstantRange.
94  ///
95  uint32_t getBitWidth() const { return Lower.getBitWidth(); }
96
97  /// Return true if this set contains all of the elements possible
98  /// for this data-type.
99  ///
100  bool isFullSet() const;
101
102  /// Return true if this set contains no members.
103  ///
104  bool isEmptySet() const;
105
106  /// Return true if this set wraps around the top of the range.
107  /// For example: [100, 8).
108  ///
109  bool isWrappedSet() const;
110
111  /// Return true if this set wraps around the INT_MIN of
112  /// its bitwidth. For example: i8 [120, 140).
113  ///
114  bool isSignWrappedSet() const;
115
116  /// Return true if the specified value is in the set.
117  ///
118  bool contains(const APInt &Val) const;
119
120  /// Return true if the other range is a subset of this one.
121  ///
122  bool contains(const ConstantRange &CR) const;
123
124  /// If this set contains a single element, return it, otherwise return null.
125  ///
126  const APInt *getSingleElement() const {
127    if (Upper == Lower + 1)
128      return &Lower;
129    return nullptr;
130  }
131
132  /// Return true if this set contains exactly one member.
133  ///
134  bool isSingleElement() const { return getSingleElement() != nullptr; }
135
136  /// Return the number of elements in this set.
137  ///
138  APInt getSetSize() const;
139
140  /// Return the largest unsigned value contained in the ConstantRange.
141  ///
142  APInt getUnsignedMax() const;
143
144  /// Return the smallest unsigned value contained in the ConstantRange.
145  ///
146  APInt getUnsignedMin() const;
147
148  /// Return the largest signed value contained in the ConstantRange.
149  ///
150  APInt getSignedMax() const;
151
152  /// Return the smallest signed value contained in the ConstantRange.
153  ///
154  APInt getSignedMin() const;
155
156  /// Return true if this range is equal to another range.
157  ///
158  bool operator==(const ConstantRange &CR) const {
159    return Lower == CR.Lower && Upper == CR.Upper;
160  }
161  bool operator!=(const ConstantRange &CR) const {
162    return !operator==(CR);
163  }
164
165  /// Subtract the specified constant from the endpoints of this constant range.
166  ConstantRange subtract(const APInt &CI) const;
167
168  /// \brief Subtract the specified range from this range (aka relative
169  /// complement of the sets).
170  ConstantRange difference(const ConstantRange &CR) const;
171
172  /// Return the range that results from the intersection of
173  /// this range with another range.  The resultant range is guaranteed to
174  /// include all elements contained in both input ranges, and to have the
175  /// smallest possible set size that does so.  Because there may be two
176  /// intersections with the same set size, A.intersectWith(B) might not
177  /// be equal to B.intersectWith(A).
178  ///
179  ConstantRange intersectWith(const ConstantRange &CR) const;
180
181  /// Return the range that results from the union of this range
182  /// with another range.  The resultant range is guaranteed to include the
183  /// elements of both sets, but may contain more.  For example, [3, 9) union
184  /// [12,15) is [3, 15), which includes 9, 10, and 11, which were not included
185  /// in either set before.
186  ///
187  ConstantRange unionWith(const ConstantRange &CR) const;
188
189  /// Return a new range in the specified integer type, which must
190  /// be strictly larger than the current type.  The returned range will
191  /// correspond to the possible range of values if the source range had been
192  /// zero extended to BitWidth.
193  ConstantRange zeroExtend(uint32_t BitWidth) const;
194
195  /// Return a new range in the specified integer type, which must
196  /// be strictly larger than the current type.  The returned range will
197  /// correspond to the possible range of values if the source range had been
198  /// sign extended to BitWidth.
199  ConstantRange signExtend(uint32_t BitWidth) const;
200
201  /// Return a new range in the specified integer type, which must be
202  /// strictly smaller than the current type.  The returned range will
203  /// correspond to the possible range of values if the source range had been
204  /// truncated to the specified type.
205  ConstantRange truncate(uint32_t BitWidth) const;
206
207  /// Make this range have the bit width given by \p BitWidth. The
208  /// value is zero extended, truncated, or left alone to make it that width.
209  ConstantRange zextOrTrunc(uint32_t BitWidth) const;
210
211  /// Make this range have the bit width given by \p BitWidth. The
212  /// value is sign extended, truncated, or left alone to make it that width.
213  ConstantRange sextOrTrunc(uint32_t BitWidth) const;
214
215  /// Return a new range representing the possible values resulting
216  /// from an addition of a value in this range and a value in \p Other.
217  ConstantRange add(const ConstantRange &Other) const;
218
219  /// Return a new range representing the possible values resulting
220  /// from a subtraction of a value in this range and a value in \p Other.
221  ConstantRange sub(const ConstantRange &Other) const;
222
223  /// Return a new range representing the possible values resulting
224  /// from a multiplication of a value in this range and a value in \p Other,
225  /// treating both this and \p Other as unsigned ranges.
226  ConstantRange multiply(const ConstantRange &Other) const;
227
228  /// Return a new range representing the possible values resulting
229  /// from a signed maximum of a value in this range and a value in \p Other.
230  ConstantRange smax(const ConstantRange &Other) const;
231
232  /// Return a new range representing the possible values resulting
233  /// from an unsigned maximum of a value in this range and a value in \p Other.
234  ConstantRange umax(const ConstantRange &Other) const;
235
236  /// Return a new range representing the possible values resulting
237  /// from an unsigned division of a value in this range and a value in
238  /// \p Other.
239  ConstantRange udiv(const ConstantRange &Other) const;
240
241  /// Return a new range representing the possible values resulting
242  /// from a binary-and of a value in this range by a value in \p Other.
243  ConstantRange binaryAnd(const ConstantRange &Other) const;
244
245  /// Return a new range representing the possible values resulting
246  /// from a binary-or of a value in this range by a value in \p Other.
247  ConstantRange binaryOr(const ConstantRange &Other) const;
248
249  /// Return a new range representing the possible values resulting
250  /// from a left shift of a value in this range by a value in \p Other.
251  /// TODO: This isn't fully implemented yet.
252  ConstantRange shl(const ConstantRange &Other) const;
253
254  /// Return a new range representing the possible values resulting from a
255  /// logical right shift of a value in this range and a value in \p Other.
256  ConstantRange lshr(const ConstantRange &Other) const;
257
258  /// Return a new range that is the logical not of the current set.
259  ///
260  ConstantRange inverse() const;
261
262  /// Print out the bounds to a stream.
263  ///
264  void print(raw_ostream &OS) const;
265
266  /// Allow printing from a debugger easily.
267  ///
268  void dump() const;
269};
270
271inline raw_ostream &operator<<(raw_ostream &OS, const ConstantRange &CR) {
272  CR.print(OS);
273  return OS;
274}
275
276} // End llvm namespace
277
278#endif
279