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 41 namespace llvm { 42 43 class MDNode; 44 class raw_ostream; 45 46 /// This class represents a range of values. 47 class LLVM_NODISCARD ConstantRange { 48 APInt Lower, Upper; 49 50 public: 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 }; 329 330 inline 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). 338 ConstantRange getConstantRangeFromMetadata(const MDNode &RangeMD); 339 340 } // end namespace llvm 341 342 #endif // LLVM_IR_CONSTANTRANGE_H 343