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 
39 namespace llvm {
40 
41 /// This class represents a range of values.
42 ///
43 class 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 
49 public:
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 largest range containing all X such that "X BinOpC C" does not
86   /// wrap (overflow).
87   ///
88   /// Example:
89   ///  typedef OverflowingBinaryOperator OBO;
90   ///  makeNoWrapRegion(Add, i8 1, OBO::NoSignedWrap) == [-128, 127)
91   ///  makeNoWrapRegion(Add, i8 1, OBO::NoUnsignedWrap) == [0, -1)
92   ///  makeNoWrapRegion(Add, i8 0, OBO::NoUnsignedWrap) == Full Set
93   static ConstantRange makeNoWrapRegion(Instruction::BinaryOps BinOp,
94                                         const APInt &C, unsigned NoWrapKind);
95 
96   /// Return the lower value for this range.
97   ///
getLower()98   const APInt &getLower() const { return Lower; }
99 
100   /// Return the upper value for this range.
101   ///
getUpper()102   const APInt &getUpper() const { return Upper; }
103 
104   /// Get the bit width of this ConstantRange.
105   ///
getBitWidth()106   uint32_t getBitWidth() const { return Lower.getBitWidth(); }
107 
108   /// Return true if this set contains all of the elements possible
109   /// for this data-type.
110   ///
111   bool isFullSet() const;
112 
113   /// Return true if this set contains no members.
114   ///
115   bool isEmptySet() const;
116 
117   /// Return true if this set wraps around the top of the range.
118   /// For example: [100, 8).
119   ///
120   bool isWrappedSet() const;
121 
122   /// Return true if this set wraps around the INT_MIN of
123   /// its bitwidth. For example: i8 [120, 140).
124   ///
125   bool isSignWrappedSet() const;
126 
127   /// Return true if the specified value is in the set.
128   ///
129   bool contains(const APInt &Val) const;
130 
131   /// Return true if the other range is a subset of this one.
132   ///
133   bool contains(const ConstantRange &CR) const;
134 
135   /// If this set contains a single element, return it, otherwise return null.
136   ///
getSingleElement()137   const APInt *getSingleElement() const {
138     if (Upper == Lower + 1)
139       return &Lower;
140     return nullptr;
141   }
142 
143   /// Return true if this set contains exactly one member.
144   ///
isSingleElement()145   bool isSingleElement() const { return getSingleElement() != nullptr; }
146 
147   /// Return the number of elements in this set.
148   ///
149   APInt getSetSize() const;
150 
151   /// Return the largest unsigned value contained in the ConstantRange.
152   ///
153   APInt getUnsignedMax() const;
154 
155   /// Return the smallest unsigned value contained in the ConstantRange.
156   ///
157   APInt getUnsignedMin() const;
158 
159   /// Return the largest signed value contained in the ConstantRange.
160   ///
161   APInt getSignedMax() const;
162 
163   /// Return the smallest signed value contained in the ConstantRange.
164   ///
165   APInt getSignedMin() const;
166 
167   /// Return true if this range is equal to another range.
168   ///
169   bool operator==(const ConstantRange &CR) const {
170     return Lower == CR.Lower && Upper == CR.Upper;
171   }
172   bool operator!=(const ConstantRange &CR) const {
173     return !operator==(CR);
174   }
175 
176   /// Subtract the specified constant from the endpoints of this constant range.
177   ConstantRange subtract(const APInt &CI) const;
178 
179   /// \brief Subtract the specified range from this range (aka relative
180   /// complement of the sets).
181   ConstantRange difference(const ConstantRange &CR) const;
182 
183   /// Return the range that results from the intersection of
184   /// this range with another range.  The resultant range is guaranteed to
185   /// include all elements contained in both input ranges, and to have the
186   /// smallest possible set size that does so.  Because there may be two
187   /// intersections with the same set size, A.intersectWith(B) might not
188   /// be equal to B.intersectWith(A).
189   ///
190   ConstantRange intersectWith(const ConstantRange &CR) const;
191 
192   /// Return the range that results from the union of this range
193   /// with another range.  The resultant range is guaranteed to include the
194   /// elements of both sets, but may contain more.  For example, [3, 9) union
195   /// [12,15) is [3, 15), which includes 9, 10, and 11, which were not included
196   /// in either set before.
197   ///
198   ConstantRange unionWith(const ConstantRange &CR) const;
199 
200   /// Return a new range in the specified integer type, which must
201   /// be strictly larger than the current type.  The returned range will
202   /// correspond to the possible range of values if the source range had been
203   /// zero extended to BitWidth.
204   ConstantRange zeroExtend(uint32_t BitWidth) const;
205 
206   /// Return a new range in the specified integer type, which must
207   /// be strictly larger than the current type.  The returned range will
208   /// correspond to the possible range of values if the source range had been
209   /// sign extended to BitWidth.
210   ConstantRange signExtend(uint32_t BitWidth) const;
211 
212   /// Return a new range in the specified integer type, which must be
213   /// strictly smaller than the current type.  The returned range will
214   /// correspond to the possible range of values if the source range had been
215   /// truncated to the specified type.
216   ConstantRange truncate(uint32_t BitWidth) const;
217 
218   /// Make this range have the bit width given by \p BitWidth. The
219   /// value is zero extended, truncated, or left alone to make it that width.
220   ConstantRange zextOrTrunc(uint32_t BitWidth) const;
221 
222   /// Make this range have the bit width given by \p BitWidth. The
223   /// value is sign extended, truncated, or left alone to make it that width.
224   ConstantRange sextOrTrunc(uint32_t BitWidth) const;
225 
226   /// Return a new range representing the possible values resulting
227   /// from an addition of a value in this range and a value in \p Other.
228   ConstantRange add(const ConstantRange &Other) const;
229 
230   /// Return a new range representing the possible values resulting
231   /// from a subtraction of a value in this range and a value in \p Other.
232   ConstantRange sub(const ConstantRange &Other) const;
233 
234   /// Return a new range representing the possible values resulting
235   /// from a multiplication of a value in this range and a value in \p Other,
236   /// treating both this and \p Other as unsigned ranges.
237   ConstantRange multiply(const ConstantRange &Other) const;
238 
239   /// Return a new range representing the possible values resulting
240   /// from a signed maximum of a value in this range and a value in \p Other.
241   ConstantRange smax(const ConstantRange &Other) const;
242 
243   /// Return a new range representing the possible values resulting
244   /// from an unsigned maximum of a value in this range and a value in \p Other.
245   ConstantRange umax(const ConstantRange &Other) const;
246 
247   /// Return a new range representing the possible values resulting
248   /// from an unsigned division of a value in this range and a value in
249   /// \p Other.
250   ConstantRange udiv(const ConstantRange &Other) const;
251 
252   /// Return a new range representing the possible values resulting
253   /// from a binary-and of a value in this range by a value in \p Other.
254   ConstantRange binaryAnd(const ConstantRange &Other) const;
255 
256   /// Return a new range representing the possible values resulting
257   /// from a binary-or of a value in this range by a value in \p Other.
258   ConstantRange binaryOr(const ConstantRange &Other) const;
259 
260   /// Return a new range representing the possible values resulting
261   /// from a left shift of a value in this range by a value in \p Other.
262   /// TODO: This isn't fully implemented yet.
263   ConstantRange shl(const ConstantRange &Other) const;
264 
265   /// Return a new range representing the possible values resulting from a
266   /// logical right shift of a value in this range and a value in \p Other.
267   ConstantRange lshr(const ConstantRange &Other) const;
268 
269   /// Return a new range that is the logical not of the current set.
270   ///
271   ConstantRange inverse() const;
272 
273   /// Print out the bounds to a stream.
274   ///
275   void print(raw_ostream &OS) const;
276 
277   /// Allow printing from a debugger easily.
278   ///
279   void dump() const;
280 };
281 
282 inline raw_ostream &operator<<(raw_ostream &OS, const ConstantRange &CR) {
283   CR.print(OS);
284   return OS;
285 }
286 
287 } // End llvm namespace
288 
289 #endif
290