include/llvm/IR/ConstantRange.h

   1 //===- ConstantRange.h - Represent a range ----------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Represent a range of possible values that may occur when the program is run
  10 // for an integral value.  This keeps track of a lower and upper bound for the
  11 // constant, which MAY wrap around the end of the numeric range.  To do this, it
  12 // keeps track of a [lower, upper) bound, which specifies an interval just like
  13 // STL iterators.  When used with boolean values, the following are important
  14 // ranges: :
  15 //
  16 //  [F, F) = {}     = Empty set
  17 //  [T, F) = {T}
  18 //  [F, T) = {F}
  19 //  [T, T) = {F, T} = Full set
  20 //
  21 // The other integral ranges use min/max values for special range values. For
  22 // example, for 8-bit types, it uses:
  23 // [0, 0)     = {}       = Empty set
  24 // [255, 255) = {0..255} = Full Set
  25 //
  26 // Note that ConstantRange can be used to represent either signed or
  27 // unsigned ranges.
  28 //
  29 //===----------------------------------------------------------------------===//
  30
  31 #ifndef LLVM_IR_CONSTANTRANGE_H
  32 #define LLVM_IR_CONSTANTRANGE_H
  33
  34 #include "llvm/ADT/APInt.h"
  35 #include "llvm/IR/InstrTypes.h"
  36 #include "llvm/IR/Instruction.h"
  37 #include "llvm/Support/Compiler.h"
  38 #include <cstdint>
  39
  40 namespace llvm {
  41
  42 class MDNode;
  43 class raw_ostream;
  44
  45 /// This class represents a range of values.
  46 class LLVM_NODISCARD ConstantRange {
  47   APInt Lower, Upper;
  48
  49 public:
  50   /// Initialize a full (the default) or empty set for the specified bit width.
  51   explicit ConstantRange(uint32_t BitWidth, bool isFullSet = true);
  52
  53   /// Initialize a range to hold the single specified value.
  54   ConstantRange(APInt Value);
  55
  56   /// Initialize a range of values explicitly. This will assert out if
  57   /// Lower==Upper and Lower != Min or Max value for its type. It will also
  58   /// assert out if the two APInt's are not the same bit width.
  59   ConstantRange(APInt Lower, APInt Upper);
  60
  61   /// Produce the smallest range such that all values that may satisfy the given
  62   /// predicate with any value contained within Other is contained in the
  63   /// returned range.  Formally, this returns a superset of
  64   /// 'union over all y in Other . { x : icmp op x y is true }'.  If the exact
  65   /// answer is not representable as a ConstantRange, the return value will be a
  66   /// proper superset of the above.
  67   ///
  68   /// Example: Pred = ult and Other = i8 [2, 5) returns Result = [0, 4)
  69   static ConstantRange makeAllowedICmpRegion(CmpInst::Predicate Pred,
  70                                              const ConstantRange &Other);
  71
  72   /// Produce the largest range such that all values in the returned range
  73   /// satisfy the given predicate with all values contained within Other.
  74   /// Formally, this returns a subset of
  75   /// 'intersection over all y in Other . { x : icmp op x y is true }'.  If the
  76   /// exact answer is not representable as a ConstantRange, the return value
  77   /// will be a proper subset of the above.
  78   ///
  79   /// Example: Pred = ult and Other = i8 [2, 5) returns [0, 2)
  80   static ConstantRange makeSatisfyingICmpRegion(CmpInst::Predicate Pred,
  81                                                 const ConstantRange &Other);
  82
  83   /// Produce the exact range such that all values in the returned range satisfy
  84   /// the given predicate with any value contained within Other. Formally, this
  85   /// returns the exact answer when the superset of 'union over all y in Other
  86   /// is exactly same as the subset of intersection over all y in Other.
  87   /// { x : icmp op x y is true}'.
  88   ///
  89   /// Example: Pred = ult and Other = i8 3 returns [0, 3)
  90   static ConstantRange makeExactICmpRegion(CmpInst::Predicate Pred,
  91                                            const APInt &Other);
  92
  93   /// Return the largest range containing all X such that "X BinOpC Y" is
  94   /// guaranteed not to wrap (overflow) for all Y in Other.
  95   ///
  96   /// NB! The returned set does *not* contain **all** possible values of X for
  97   /// which "X BinOpC Y" does not wrap -- some viable values of X may be
  98   /// missing, so you cannot use this to constrain X's range.  E.g. in the
  99   /// fourth example, "(-2) + 1" is both nsw and nuw (so the "X" could be -2),
 100   /// but (-2) is not in the set returned.
 101   ///
 102   /// Examples:
 103   ///  typedef OverflowingBinaryOperator OBO;
 104   ///  #define MGNR makeGuaranteedNoWrapRegion
 105   ///  MGNR(Add, [i8 1, 2), OBO::NoSignedWrap) == [-128, 127)
 106   ///  MGNR(Add, [i8 1, 2), OBO::NoUnsignedWrap) == [0, -1)
 107   ///  MGNR(Add, [i8 0, 1), OBO::NoUnsignedWrap) == Full Set
 108   ///  MGNR(Add, [i8 1, 2), OBO::NoUnsignedWrap | OBO::NoSignedWrap)
 109   ///    == [0,INT_MAX)
 110   ///  MGNR(Add, [i8 -1, 6), OBO::NoSignedWrap) == [INT_MIN+1, INT_MAX-4)
 111   ///  MGNR(Sub, [i8 1, 2), OBO::NoSignedWrap) == [-127, 128)
 112   ///  MGNR(Sub, [i8 1, 2), OBO::NoUnsignedWrap) == [1, 0)
 113   ///  MGNR(Sub, [i8 1, 2), OBO::NoUnsignedWrap | OBO::NoSignedWrap)
 114   ///    == [1,INT_MAX)
 115   static ConstantRange makeGuaranteedNoWrapRegion(Instruction::BinaryOps BinOp,
 116                                                   const ConstantRange &Other,
 117                                                   unsigned NoWrapKind);
 118
 119   /// Set up \p Pred and \p RHS such that
 120   /// ConstantRange::makeExactICmpRegion(Pred, RHS) == *this.  Return true if
 121   /// successful.
 122   bool getEquivalentICmp(CmpInst::Predicate &Pred, APInt &RHS) const;
 123
 124   /// Return the lower value for this range.
 125   const APInt &getLower() const { return Lower; }
 126
 127   /// Return the upper value for this range.
 128   const APInt &getUpper() const { return Upper; }
 129
 130   /// Get the bit width of this ConstantRange.
 131   uint32_t getBitWidth() const { return Lower.getBitWidth(); }
 132
 133   /// Return true if this set contains all of the elements possible
 134   /// for this data-type.
 135   bool isFullSet() const;
 136
 137   /// Return true if this set contains no members.
 138   bool isEmptySet() const;
 139
 140   /// Return true if this set wraps around the top of the range.
 141   /// For example: [100, 8).
 142   bool isWrappedSet() const;
 143
 144   /// Return true if this set wraps around the INT_MIN of
 145   /// its bitwidth. For example: i8 [120, 140).
 146   bool isSignWrappedSet() const;
 147
 148   /// Return true if the specified value is in the set.
 149   bool contains(const APInt &Val) const;
 150
 151   /// Return true if the other range is a subset of this one.
 152   bool contains(const ConstantRange &CR) const;
 153
 154   /// If this set contains a single element, return it, otherwise return null.
 155   const APInt *getSingleElement() const {
 156     if (Upper == Lower + 1)
 157       return &Lower;
 158     return nullptr;
 159   }
 160
 161   /// If this set contains all but a single element, return it, otherwise return
 162   /// null.
 163   const APInt *getSingleMissingElement() const {
 164     if (Lower == Upper + 1)
 165       return &Upper;
 166     return nullptr;
 167   }
 168
 169   /// Return true if this set contains exactly one member.
 170   bool isSingleElement() const { return getSingleElement() != nullptr; }
 171
 172   /// Return the number of elements in this set.
 173   APInt getSetSize() const;
 174
 175   /// Compare set size of this range with the range CR.
 176   bool isSizeStrictlySmallerThan(const ConstantRange &CR) const;
 177
 178   // Compare set size of this range with Value.
 179   bool isSizeLargerThan(uint64_t MaxSize) const;
 180
 181   /// Return the largest unsigned value contained in the ConstantRange.
 182   APInt getUnsignedMax() const;
 183
 184   /// Return the smallest unsigned value contained in the ConstantRange.
 185   APInt getUnsignedMin() const;
 186
 187   /// Return the largest signed value contained in the ConstantRange.
 188   APInt getSignedMax() const;
 189
 190   /// Return the smallest signed value contained in the ConstantRange.
 191   APInt getSignedMin() const;
 192
 193   /// Return true if this range is equal to another range.
 194   bool operator==(const ConstantRange &CR) const {
 195     return Lower == CR.Lower && Upper == CR.Upper;
 196   }
 197   bool operator!=(const ConstantRange &CR) const {
 198     return !operator==(CR);
 199   }
 200
 201   /// Subtract the specified constant from the endpoints of this constant range.
 202   ConstantRange subtract(const APInt &CI) const;
 203
 204   /// Subtract the specified range from this range (aka relative complement of
 205   /// the sets).
 206   ConstantRange difference(const ConstantRange &CR) const;
 207
 208   /// Return the range that results from the intersection of
 209   /// this range with another range.  The resultant range is guaranteed to
 210   /// include all elements contained in both input ranges, and to have the
 211   /// smallest possible set size that does so.  Because there may be two
 212   /// intersections with the same set size, A.intersectWith(B) might not
 213   /// be equal to B.intersectWith(A).
 214   ConstantRange intersectWith(const ConstantRange &CR) const;
 215
 216   /// Return the range that results from the union of this range
 217   /// with another range.  The resultant range is guaranteed to include the
 218   /// elements of both sets, but may contain more.  For example, [3, 9) union
 219   /// [12,15) is [3, 15), which includes 9, 10, and 11, which were not included
 220   /// in either set before.
 221   ConstantRange unionWith(const ConstantRange &CR) const;
 222
 223   /// Return a new range representing the possible values resulting
 224   /// from an application of the specified cast operator to this range. \p
 225   /// BitWidth is the target bitwidth of the cast.  For casts which don't
 226   /// change bitwidth, it must be the same as the source bitwidth.  For casts
 227   /// which do change bitwidth, the bitwidth must be consistent with the
 228   /// requested cast and source bitwidth.
 229   ConstantRange castOp(Instruction::CastOps CastOp,
 230                        uint32_t BitWidth) const;
 231
 232   /// Return a new range in the specified integer type, which must
 233   /// be strictly larger than the current type.  The returned range will
 234   /// correspond to the possible range of values if the source range had been
 235   /// zero extended to BitWidth.
 236   ConstantRange zeroExtend(uint32_t BitWidth) const;
 237
 238   /// Return a new range in the specified integer type, which must
 239   /// be strictly larger than the current type.  The returned range will
 240   /// correspond to the possible range of values if the source range had been
 241   /// sign extended to BitWidth.
 242   ConstantRange signExtend(uint32_t BitWidth) const;
 243
 244   /// Return a new range in the specified integer type, which must be
 245   /// strictly smaller than the current type.  The returned range will
 246   /// correspond to the possible range of values if the source range had been
 247   /// truncated to the specified type.
 248   ConstantRange truncate(uint32_t BitWidth) const;
 249
 250   /// Make this range have the bit width given by \p BitWidth. The
 251   /// value is zero extended, truncated, or left alone to make it that width.
 252   ConstantRange zextOrTrunc(uint32_t BitWidth) const;
 253
 254   /// Make this range have the bit width given by \p BitWidth. The
 255   /// value is sign extended, truncated, or left alone to make it that width.
 256   ConstantRange sextOrTrunc(uint32_t BitWidth) const;
 257
 258   /// Return a new range representing the possible values resulting
 259   /// from an application of the specified binary operator to an left hand side
 260   /// of this range and a right hand side of \p Other.
 261   ConstantRange binaryOp(Instruction::BinaryOps BinOp,
 262                          const ConstantRange &Other) const;
 263
 264   /// Return a new range representing the possible values resulting
 265   /// from an addition of a value in this range and a value in \p Other.
 266   ConstantRange add(const ConstantRange &Other) const;
 267
 268   /// Return a new range representing the possible values resulting from a
 269   /// known NSW addition of a value in this range and \p Other constant.
 270   ConstantRange addWithNoSignedWrap(const APInt &Other) const;
 271
 272   /// Return a new range representing the possible values resulting
 273   /// from a subtraction of a value in this range and a value in \p Other.
 274   ConstantRange sub(const ConstantRange &Other) const;
 275
 276   /// Return a new range representing the possible values resulting
 277   /// from a multiplication of a value in this range and a value in \p Other,
 278   /// treating both this and \p Other as unsigned ranges.
 279   ConstantRange multiply(const ConstantRange &Other) const;
 280
 281   /// Return a new range representing the possible values resulting
 282   /// from a signed maximum of a value in this range and a value in \p Other.
 283   ConstantRange smax(const ConstantRange &Other) const;
 284
 285   /// Return a new range representing the possible values resulting
 286   /// from an unsigned maximum of a value in this range and a value in \p Other.
 287   ConstantRange umax(const ConstantRange &Other) const;
 288
 289   /// Return a new range representing the possible values resulting
 290   /// from a signed minimum of a value in this range and a value in \p Other.
 291   ConstantRange smin(const ConstantRange &Other) const;
 292
 293   /// Return a new range representing the possible values resulting
 294   /// from an unsigned minimum of a value in this range and a value in \p Other.
 295   ConstantRange umin(const ConstantRange &Other) const;
 296
 297   /// Return a new range representing the possible values resulting
 298   /// from an unsigned division of a value in this range and a value in
 299   /// \p Other.
 300   ConstantRange udiv(const ConstantRange &Other) const;
 301
 302   /// Return a new range representing the possible values resulting
 303   /// from a binary-and of a value in this range by a value in \p Other.
 304   ConstantRange binaryAnd(const ConstantRange &Other) const;
 305
 306   /// Return a new range representing the possible values resulting
 307   /// from a binary-or of a value in this range by a value in \p Other.
 308   ConstantRange binaryOr(const ConstantRange &Other) const;
 309
 310   /// Return a new range representing the possible values resulting
 311   /// from a left shift of a value in this range by a value in \p Other.
 312   /// TODO: This isn't fully implemented yet.
 313   ConstantRange shl(const ConstantRange &Other) const;
 314
 315   /// Return a new range representing the possible values resulting from a
 316   /// logical right shift of a value in this range and a value in \p Other.
 317   ConstantRange lshr(const ConstantRange &Other) const;
 318
 319   /// Return a new range representing the possible values resulting from a
 320   /// arithmetic right shift of a value in this range and a value in \p Other.
 321   ConstantRange ashr(const ConstantRange &Other) const;
 322
 323   /// Return a new range that is the logical not of the current set.
 324   ConstantRange inverse() const;
 325
 326   /// Print out the bounds to a stream.
 327   void print(raw_ostream &OS) const;
 328
 329   /// Allow printing from a debugger easily.
 330   void dump() const;
 331 };
 332
 333 inline raw_ostream &operator<<(raw_ostream &OS, const ConstantRange &CR) {
 334   CR.print(OS);
 335   return OS;
 336 }
 337
 338 /// Parse out a conservative ConstantRange from !range metadata.
 339 ///
 340 /// E.g. if RangeMD is !{i32 0, i32 10, i32 15, i32 20} then return [0, 20).
 341 ConstantRange getConstantRangeFromMetadata(const MDNode &RangeMD);
 342
 343 } // end namespace llvm
 344
 345 #endif // LLVM_IR_CONSTANTRANGE_H