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/IR/Instruction.h"
38#include "llvm/Support/Compiler.h"
39#include <cstdint>
40
41namespace llvm {
42
43class MDNode;
44class raw_ostream;
45
46/// This class represents a range of values.
47class LLVM_NODISCARD ConstantRange {
48  APInt Lower, Upper;
49
50public:
51  /// Initialize a full (the default) or empty set for the specified bit width.
52  explicit ConstantRange(uint32_t BitWidth, bool isFullSet = true);
53
54  /// Initialize a range to hold the single specified value.
55  ConstantRange(APInt Value);
56
57  /// @brief Initialize a range of values explicitly. This will assert out if
58  /// Lower==Upper and Lower != Min or Max value for its type. It will also
59  /// assert out if the two APInt's are not the same bit width.
60  ConstantRange(APInt Lower, APInt Upper);
61
62  /// Produce the smallest range such that all values that may satisfy the given
63  /// predicate with any value contained within Other is contained in the
64  /// returned range.  Formally, this returns a superset of
65  /// 'union over all y in Other . { x : icmp op x y is true }'.  If the exact
66  /// answer is not representable as a ConstantRange, the return value will be a
67  /// proper superset of the above.
68  ///
69  /// Example: Pred = ult and Other = i8 [2, 5) returns Result = [0, 4)
70  static ConstantRange makeAllowedICmpRegion(CmpInst::Predicate Pred,
71                                             const ConstantRange &Other);
72
73  /// Produce the largest range such that all values in the returned range
74  /// satisfy the given predicate with all values contained within Other.
75  /// Formally, this returns a subset of
76  /// 'intersection over all y in Other . { x : icmp op x y is true }'.  If the
77  /// exact answer is not representable as a ConstantRange, the return value
78  /// will be a proper subset of the above.
79  ///
80  /// Example: Pred = ult and Other = i8 [2, 5) returns [0, 2)
81  static ConstantRange makeSatisfyingICmpRegion(CmpInst::Predicate Pred,
82                                                const ConstantRange &Other);
83
84  /// Produce the exact range such that all values in the returned range satisfy
85  /// the given predicate with any value contained within Other. Formally, this
86  /// returns the exact answer when the superset of 'union over all y in Other
87  /// is exactly same as the subset of intersection over all y in Other.
88  /// { x : icmp op x y is true}'.
89  ///
90  /// Example: Pred = ult and Other = i8 3 returns [0, 3)
91  static ConstantRange makeExactICmpRegion(CmpInst::Predicate Pred,
92                                           const APInt &Other);
93
94  /// Return the largest range containing all X such that "X BinOpC Y" is
95  /// guaranteed not to wrap (overflow) for all Y in Other.
96  ///
97  /// NB! The returned set does *not* contain **all** possible values of X for
98  /// which "X BinOpC Y" does not wrap -- some viable values of X may be
99  /// missing, so you cannot use this to constrain X's range.  E.g. in the
100  /// fourth example, "(-2) + 1" is both nsw and nuw (so the "X" could be -2),
101  /// but (-2) is not in the set returned.
102  ///
103  /// Examples:
104  ///  typedef OverflowingBinaryOperator OBO;
105  ///  #define MGNR makeGuaranteedNoWrapRegion
106  ///  MGNR(Add, [i8 1, 2), OBO::NoSignedWrap) == [-128, 127)
107  ///  MGNR(Add, [i8 1, 2), OBO::NoUnsignedWrap) == [0, -1)
108  ///  MGNR(Add, [i8 0, 1), OBO::NoUnsignedWrap) == Full Set
109  ///  MGNR(Add, [i8 1, 2), OBO::NoUnsignedWrap | OBO::NoSignedWrap)
110  ///    == [0,INT_MAX)
111  ///  MGNR(Add, [i8 -1, 6), OBO::NoSignedWrap) == [INT_MIN+1, INT_MAX-4)
112  ///  MGNR(Sub, [i8 1, 2), OBO::NoSignedWrap) == [-127, 128)
113  ///  MGNR(Sub, [i8 1, 2), OBO::NoUnsignedWrap) == [1, 0)
114  ///  MGNR(Sub, [i8 1, 2), OBO::NoUnsignedWrap | OBO::NoSignedWrap)
115  ///    == [1,INT_MAX)
116  static ConstantRange makeGuaranteedNoWrapRegion(Instruction::BinaryOps BinOp,
117                                                  const ConstantRange &Other,
118                                                  unsigned NoWrapKind);
119
120  /// Set up \p Pred and \p RHS such that
121  /// ConstantRange::makeExactICmpRegion(Pred, RHS) == *this.  Return true if
122  /// successful.
123  bool getEquivalentICmp(CmpInst::Predicate &Pred, APInt &RHS) const;
124
125  /// Return the lower value for this range.
126  const APInt &getLower() const { return Lower; }
127
128  /// Return the upper value for this range.
129  const APInt &getUpper() const { return Upper; }
130
131  /// Get the bit width of this ConstantRange.
132  uint32_t getBitWidth() const { return Lower.getBitWidth(); }
133
134  /// Return true if this set contains all of the elements possible
135  /// for this data-type.
136  bool isFullSet() const;
137
138  /// Return true if this set contains no members.
139  bool isEmptySet() const;
140
141  /// Return true if this set wraps around the top of the range.
142  /// For example: [100, 8).
143  bool isWrappedSet() const;
144
145  /// Return true if this set wraps around the INT_MIN of
146  /// its bitwidth. For example: i8 [120, 140).
147  bool isSignWrappedSet() const;
148
149  /// Return true if the specified value is in the set.
150  bool contains(const APInt &Val) const;
151
152  /// Return true if the other range is a subset of this one.
153  bool contains(const ConstantRange &CR) const;
154
155  /// If this set contains a single element, return it, otherwise return null.
156  const APInt *getSingleElement() const {
157    if (Upper == Lower + 1)
158      return &Lower;
159    return nullptr;
160  }
161
162  /// If this set contains all but a single element, return it, otherwise return
163  /// null.
164  const APInt *getSingleMissingElement() const {
165    if (Lower == Upper + 1)
166      return &Upper;
167    return nullptr;
168  }
169
170  /// Return true if this set contains exactly one member.
171  bool isSingleElement() const { return getSingleElement() != nullptr; }
172
173  /// Return the number of elements in this set.
174  APInt getSetSize() const;
175
176  /// Compare set size of this range with the range CR.
177  bool isSizeStrictlySmallerThan(const ConstantRange &CR) const;
178
179  // Compare set size of this range with Value.
180  bool isSizeLargerThan(uint64_t MaxSize) const;
181
182  /// Return the largest unsigned value contained in the ConstantRange.
183  APInt getUnsignedMax() const;
184
185  /// Return the smallest unsigned value contained in the ConstantRange.
186  APInt getUnsignedMin() const;
187
188  /// Return the largest signed value contained in the ConstantRange.
189  APInt getSignedMax() const;
190
191  /// Return the smallest signed value contained in the ConstantRange.
192  APInt getSignedMin() const;
193
194  /// Return true if this range is equal to another range.
195  bool operator==(const ConstantRange &CR) const {
196    return Lower == CR.Lower && Upper == CR.Upper;
197  }
198  bool operator!=(const ConstantRange &CR) const {
199    return !operator==(CR);
200  }
201
202  /// Subtract the specified constant from the endpoints of this constant range.
203  ConstantRange subtract(const APInt &CI) const;
204
205  /// Subtract the specified range from this range (aka relative complement of
206  /// the sets).
207  ConstantRange difference(const ConstantRange &CR) const;
208
209  /// Return the range that results from the intersection of
210  /// this range with another range.  The resultant range is guaranteed to
211  /// include all elements contained in both input ranges, and to have the
212  /// smallest possible set size that does so.  Because there may be two
213  /// intersections with the same set size, A.intersectWith(B) might not
214  /// be equal to B.intersectWith(A).
215  ConstantRange intersectWith(const ConstantRange &CR) const;
216
217  /// Return the range that results from the union of this range
218  /// with another range.  The resultant range is guaranteed to include the
219  /// elements of both sets, but may contain more.  For example, [3, 9) union
220  /// [12,15) is [3, 15), which includes 9, 10, and 11, which were not included
221  /// in either set before.
222  ConstantRange unionWith(const ConstantRange &CR) const;
223
224  /// Return a new range representing the possible values resulting
225  /// from an application of the specified cast operator to this range. \p
226  /// BitWidth is the target bitwidth of the cast.  For casts which don't
227  /// change bitwidth, it must be the same as the source bitwidth.  For casts
228  /// which do change bitwidth, the bitwidth must be consistent with the
229  /// requested cast and source bitwidth.
230  ConstantRange castOp(Instruction::CastOps CastOp,
231                       uint32_t BitWidth) const;
232
233  /// Return a new range in the specified integer type, which must
234  /// be strictly larger than the current type.  The returned range will
235  /// correspond to the possible range of values if the source range had been
236  /// zero extended to BitWidth.
237  ConstantRange zeroExtend(uint32_t BitWidth) const;
238
239  /// Return a new range in the specified integer type, which must
240  /// be strictly larger than the current type.  The returned range will
241  /// correspond to the possible range of values if the source range had been
242  /// sign extended to BitWidth.
243  ConstantRange signExtend(uint32_t BitWidth) const;
244
245  /// Return a new range in the specified integer type, which must be
246  /// strictly smaller than the current type.  The returned range will
247  /// correspond to the possible range of values if the source range had been
248  /// truncated to the specified type.
249  ConstantRange truncate(uint32_t BitWidth) const;
250
251  /// Make this range have the bit width given by \p BitWidth. The
252  /// value is zero extended, truncated, or left alone to make it that width.
253  ConstantRange zextOrTrunc(uint32_t BitWidth) const;
254
255  /// Make this range have the bit width given by \p BitWidth. The
256  /// value is sign extended, truncated, or left alone to make it that width.
257  ConstantRange sextOrTrunc(uint32_t BitWidth) const;
258
259  /// Return a new range representing the possible values resulting
260  /// from an application of the specified binary operator to an left hand side
261  /// of this range and a right hand side of \p Other.
262  ConstantRange binaryOp(Instruction::BinaryOps BinOp,
263                         const ConstantRange &Other) const;
264
265  /// Return a new range representing the possible values resulting
266  /// from an addition of a value in this range and a value in \p Other.
267  ConstantRange add(const ConstantRange &Other) const;
268
269  /// Return a new range representing the possible values resulting from a
270  /// known NSW addition of a value in this range and \p Other constant.
271  ConstantRange addWithNoSignedWrap(const APInt &Other) const;
272
273  /// Return a new range representing the possible values resulting
274  /// from a subtraction of a value in this range and a value in \p Other.
275  ConstantRange sub(const ConstantRange &Other) const;
276
277  /// Return a new range representing the possible values resulting
278  /// from a multiplication of a value in this range and a value in \p Other,
279  /// treating both this and \p Other as unsigned ranges.
280  ConstantRange multiply(const ConstantRange &Other) const;
281
282  /// Return a new range representing the possible values resulting
283  /// from a signed maximum of a value in this range and a value in \p Other.
284  ConstantRange smax(const ConstantRange &Other) const;
285
286  /// Return a new range representing the possible values resulting
287  /// from an unsigned maximum of a value in this range and a value in \p Other.
288  ConstantRange umax(const ConstantRange &Other) const;
289
290  /// Return a new range representing the possible values resulting
291  /// from a signed minimum of a value in this range and a value in \p Other.
292  ConstantRange smin(const ConstantRange &Other) const;
293
294  /// Return a new range representing the possible values resulting
295  /// from an unsigned minimum of a value in this range and a value in \p Other.
296  ConstantRange umin(const ConstantRange &Other) const;
297
298  /// Return a new range representing the possible values resulting
299  /// from an unsigned division of a value in this range and a value in
300  /// \p Other.
301  ConstantRange udiv(const ConstantRange &Other) const;
302
303  /// Return a new range representing the possible values resulting
304  /// from a binary-and of a value in this range by a value in \p Other.
305  ConstantRange binaryAnd(const ConstantRange &Other) const;
306
307  /// Return a new range representing the possible values resulting
308  /// from a binary-or of a value in this range by a value in \p Other.
309  ConstantRange binaryOr(const ConstantRange &Other) const;
310
311  /// Return a new range representing the possible values resulting
312  /// from a left shift of a value in this range by a value in \p Other.
313  /// TODO: This isn't fully implemented yet.
314  ConstantRange shl(const ConstantRange &Other) const;
315
316  /// Return a new range representing the possible values resulting from a
317  /// logical right shift of a value in this range and a value in \p Other.
318  ConstantRange lshr(const ConstantRange &Other) const;
319
320  /// Return a new range that is the logical not of the current set.
321  ConstantRange inverse() const;
322
323  /// Print out the bounds to a stream.
324  void print(raw_ostream &OS) const;
325
326  /// Allow printing from a debugger easily.
327  void dump() const;
328};
329
330inline raw_ostream &operator<<(raw_ostream &OS, const ConstantRange &CR) {
331  CR.print(OS);
332  return OS;
333}
334
335/// Parse out a conservative ConstantRange from !range metadata.
336///
337/// E.g. if RangeMD is !{i32 0, i32 10, i32 15, i32 20} then return [0, 20).
338ConstantRange getConstantRangeFromMetadata(const MDNode &RangeMD);
339
340} // end namespace llvm
341
342#endif // LLVM_IR_CONSTANTRANGE_H
343