1 //===- llvm/Analysis/ValueTracking.h - Walk computations --------*- 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 // This file contains routines that help analyze properties that chains of 11 // computations have. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_ANALYSIS_VALUETRACKING_H 16 #define LLVM_ANALYSIS_VALUETRACKING_H 17 18 #include "llvm/ADT/ArrayRef.h" 19 #include "llvm/ADT/Optional.h" 20 #include "llvm/ADT/SmallSet.h" 21 #include "llvm/IR/CallSite.h" 22 #include "llvm/IR/Constants.h" 23 #include "llvm/IR/Instruction.h" 24 #include "llvm/IR/Intrinsics.h" 25 #include <cassert> 26 #include <cstdint> 27 28 namespace llvm { 29 30 class AddOperator; 31 class APInt; 32 class AssumptionCache; 33 class DataLayout; 34 class DominatorTree; 35 class GEPOperator; 36 class IntrinsicInst; 37 struct KnownBits; 38 class Loop; 39 class LoopInfo; 40 class MDNode; 41 class OptimizationRemarkEmitter; 42 class StringRef; 43 class TargetLibraryInfo; 44 class Value; 45 46 /// Determine which bits of V are known to be either zero or one and return 47 /// them in the KnownZero/KnownOne bit sets. 48 /// 49 /// This function is defined on values with integer type, values with pointer 50 /// type, and vectors of integers. In the case 51 /// where V is a vector, the known zero and known one values are the 52 /// same width as the vector element, and the bit is set only if it is true 53 /// for all of the elements in the vector. 54 void computeKnownBits(const Value *V, KnownBits &Known, 55 const DataLayout &DL, unsigned Depth = 0, 56 AssumptionCache *AC = nullptr, 57 const Instruction *CxtI = nullptr, 58 const DominatorTree *DT = nullptr, 59 OptimizationRemarkEmitter *ORE = nullptr, 60 bool UseInstrInfo = true); 61 62 /// Returns the known bits rather than passing by reference. 63 KnownBits computeKnownBits(const Value *V, const DataLayout &DL, 64 unsigned Depth = 0, AssumptionCache *AC = nullptr, 65 const Instruction *CxtI = nullptr, 66 const DominatorTree *DT = nullptr, 67 OptimizationRemarkEmitter *ORE = nullptr, 68 bool UseInstrInfo = true); 69 70 /// Compute known bits from the range metadata. 71 /// \p KnownZero the set of bits that are known to be zero 72 /// \p KnownOne the set of bits that are known to be one 73 void computeKnownBitsFromRangeMetadata(const MDNode &Ranges, 74 KnownBits &Known); 75 76 /// Return true if LHS and RHS have no common bits set. 77 bool haveNoCommonBitsSet(const Value *LHS, const Value *RHS, 78 const DataLayout &DL, 79 AssumptionCache *AC = nullptr, 80 const Instruction *CxtI = nullptr, 81 const DominatorTree *DT = nullptr, 82 bool UseInstrInfo = true); 83 84 /// Return true if the given value is known to have exactly one bit set when 85 /// defined. For vectors return true if every element is known to be a power 86 /// of two when defined. Supports values with integer or pointer type and 87 /// vectors of integers. If 'OrZero' is set, then return true if the given 88 /// value is either a power of two or zero. 89 bool isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL, 90 bool OrZero = false, unsigned Depth = 0, 91 AssumptionCache *AC = nullptr, 92 const Instruction *CxtI = nullptr, 93 const DominatorTree *DT = nullptr, 94 bool UseInstrInfo = true); 95 96 bool isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI); 97 98 /// Return true if the given value is known to be non-zero when defined. For 99 /// vectors, return true if every element is known to be non-zero when 100 /// defined. For pointers, if the context instruction and dominator tree are 101 /// specified, perform context-sensitive analysis and return true if the 102 /// pointer couldn't possibly be null at the specified instruction. 103 /// Supports values with integer or pointer type and vectors of integers. 104 bool isKnownNonZero(const Value *V, const DataLayout &DL, unsigned Depth = 0, 105 AssumptionCache *AC = nullptr, 106 const Instruction *CxtI = nullptr, 107 const DominatorTree *DT = nullptr, 108 bool UseInstrInfo = true); 109 110 /// Return true if the two given values are negation. 111 /// Currently can recoginze Value pair: 112 /// 1: <X, Y> if X = sub (0, Y) or Y = sub (0, X) 113 /// 2: <X, Y> if X = sub (A, B) and Y = sub (B, A) 114 bool isKnownNegation(const Value *X, const Value *Y, bool NeedNSW = false); 115 116 /// Returns true if the give value is known to be non-negative. 117 bool isKnownNonNegative(const Value *V, const DataLayout &DL, 118 unsigned Depth = 0, 119 AssumptionCache *AC = nullptr, 120 const Instruction *CxtI = nullptr, 121 const DominatorTree *DT = nullptr, 122 bool UseInstrInfo = true); 123 124 /// Returns true if the given value is known be positive (i.e. non-negative 125 /// and non-zero). 126 bool isKnownPositive(const Value *V, const DataLayout &DL, unsigned Depth = 0, 127 AssumptionCache *AC = nullptr, 128 const Instruction *CxtI = nullptr, 129 const DominatorTree *DT = nullptr, 130 bool UseInstrInfo = true); 131 132 /// Returns true if the given value is known be negative (i.e. non-positive 133 /// and non-zero). 134 bool isKnownNegative(const Value *V, const DataLayout &DL, unsigned Depth = 0, 135 AssumptionCache *AC = nullptr, 136 const Instruction *CxtI = nullptr, 137 const DominatorTree *DT = nullptr, 138 bool UseInstrInfo = true); 139 140 /// Return true if the given values are known to be non-equal when defined. 141 /// Supports scalar integer types only. 142 bool isKnownNonEqual(const Value *V1, const Value *V2, const DataLayout &DL, 143 AssumptionCache *AC = nullptr, 144 const Instruction *CxtI = nullptr, 145 const DominatorTree *DT = nullptr, 146 bool UseInstrInfo = true); 147 148 /// Return true if 'V & Mask' is known to be zero. We use this predicate to 149 /// simplify operations downstream. Mask is known to be zero for bits that V 150 /// cannot have. 151 /// 152 /// This function is defined on values with integer type, values with pointer 153 /// type, and vectors of integers. In the case 154 /// where V is a vector, the mask, known zero, and known one values are the 155 /// same width as the vector element, and the bit is set only if it is true 156 /// for all of the elements in the vector. 157 bool MaskedValueIsZero(const Value *V, const APInt &Mask, 158 const DataLayout &DL, 159 unsigned Depth = 0, AssumptionCache *AC = nullptr, 160 const Instruction *CxtI = nullptr, 161 const DominatorTree *DT = nullptr, 162 bool UseInstrInfo = true); 163 164 /// Return the number of times the sign bit of the register is replicated into 165 /// the other bits. We know that at least 1 bit is always equal to the sign 166 /// bit (itself), but other cases can give us information. For example, 167 /// immediately after an "ashr X, 2", we know that the top 3 bits are all 168 /// equal to each other, so we return 3. For vectors, return the number of 169 /// sign bits for the vector element with the mininum number of known sign 170 /// bits. 171 unsigned ComputeNumSignBits(const Value *Op, const DataLayout &DL, 172 unsigned Depth = 0, AssumptionCache *AC = nullptr, 173 const Instruction *CxtI = nullptr, 174 const DominatorTree *DT = nullptr, 175 bool UseInstrInfo = true); 176 177 /// This function computes the integer multiple of Base that equals V. If 178 /// successful, it returns true and returns the multiple in Multiple. If 179 /// unsuccessful, it returns false. Also, if V can be simplified to an 180 /// integer, then the simplified V is returned in Val. Look through sext only 181 /// if LookThroughSExt=true. 182 bool ComputeMultiple(Value *V, unsigned Base, Value *&Multiple, 183 bool LookThroughSExt = false, 184 unsigned Depth = 0); 185 186 /// Map a call instruction to an intrinsic ID. Libcalls which have equivalent 187 /// intrinsics are treated as-if they were intrinsics. 188 Intrinsic::ID getIntrinsicForCallSite(ImmutableCallSite ICS, 189 const TargetLibraryInfo *TLI); 190 191 /// Return true if we can prove that the specified FP value is never equal to 192 /// -0.0. 193 bool CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI, 194 unsigned Depth = 0); 195 196 /// Return true if we can prove that the specified FP value is either NaN or 197 /// never less than -0.0. 198 /// 199 /// NaN --> true 200 /// +0 --> true 201 /// -0 --> true 202 /// x > +0 --> true 203 /// x < -0 --> false 204 bool CannotBeOrderedLessThanZero(const Value *V, const TargetLibraryInfo *TLI); 205 206 /// Return true if the floating-point scalar value is not a NaN or if the 207 /// floating-point vector value has no NaN elements. Return false if a value 208 /// could ever be NaN. 209 bool isKnownNeverNaN(const Value *V, const TargetLibraryInfo *TLI, 210 unsigned Depth = 0); 211 212 /// Return true if we can prove that the specified FP value's sign bit is 0. 213 /// 214 /// NaN --> true/false (depending on the NaN's sign bit) 215 /// +0 --> true 216 /// -0 --> false 217 /// x > +0 --> true 218 /// x < -0 --> false 219 bool SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI); 220 221 /// If the specified value can be set by repeating the same byte in memory, 222 /// return the i8 value that it is represented with. This is true for all i8 223 /// values obviously, but is also true for i32 0, i32 -1, i16 0xF0F0, double 224 /// 0.0 etc. If the value can't be handled with a repeated byte store (e.g. 225 /// i16 0x1234), return null. If the value is entirely undef and padding, 226 /// return undef. 227 Value *isBytewiseValue(Value *V); 228 229 /// Given an aggregrate and an sequence of indices, see if the scalar value 230 /// indexed is already around as a register, for example if it were inserted 231 /// directly into the aggregrate. 232 /// 233 /// If InsertBefore is not null, this function will duplicate (modified) 234 /// insertvalues when a part of a nested struct is extracted. 235 Value *FindInsertedValue(Value *V, 236 ArrayRef<unsigned> idx_range, 237 Instruction *InsertBefore = nullptr); 238 239 /// Analyze the specified pointer to see if it can be expressed as a base 240 /// pointer plus a constant offset. Return the base and offset to the caller. 241 Value *GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset, 242 const DataLayout &DL); GetPointerBaseWithConstantOffset(const Value * Ptr,int64_t & Offset,const DataLayout & DL)243 inline const Value *GetPointerBaseWithConstantOffset(const Value *Ptr, 244 int64_t &Offset, 245 const DataLayout &DL) { 246 return GetPointerBaseWithConstantOffset(const_cast<Value *>(Ptr), Offset, 247 DL); 248 } 249 250 /// Returns true if the GEP is based on a pointer to a string (array of 251 // \p CharSize integers) and is indexing into this string. 252 bool isGEPBasedOnPointerToString(const GEPOperator *GEP, 253 unsigned CharSize = 8); 254 255 /// Represents offset+length into a ConstantDataArray. 256 struct ConstantDataArraySlice { 257 /// ConstantDataArray pointer. nullptr indicates a zeroinitializer (a valid 258 /// initializer, it just doesn't fit the ConstantDataArray interface). 259 const ConstantDataArray *Array; 260 261 /// Slice starts at this Offset. 262 uint64_t Offset; 263 264 /// Length of the slice. 265 uint64_t Length; 266 267 /// Moves the Offset and adjusts Length accordingly. moveConstantDataArraySlice268 void move(uint64_t Delta) { 269 assert(Delta < Length); 270 Offset += Delta; 271 Length -= Delta; 272 } 273 274 /// Convenience accessor for elements in the slice. 275 uint64_t operator[](unsigned I) const { 276 return Array==nullptr ? 0 : Array->getElementAsInteger(I + Offset); 277 } 278 }; 279 280 /// Returns true if the value \p V is a pointer into a ConstantDataArray. 281 /// If successful \p Slice will point to a ConstantDataArray info object 282 /// with an appropriate offset. 283 bool getConstantDataArrayInfo(const Value *V, ConstantDataArraySlice &Slice, 284 unsigned ElementSize, uint64_t Offset = 0); 285 286 /// This function computes the length of a null-terminated C string pointed to 287 /// by V. If successful, it returns true and returns the string in Str. If 288 /// unsuccessful, it returns false. This does not include the trailing null 289 /// character by default. If TrimAtNul is set to false, then this returns any 290 /// trailing null characters as well as any other characters that come after 291 /// it. 292 bool getConstantStringInfo(const Value *V, StringRef &Str, 293 uint64_t Offset = 0, bool TrimAtNul = true); 294 295 /// If we can compute the length of the string pointed to by the specified 296 /// pointer, return 'len+1'. If we can't, return 0. 297 uint64_t GetStringLength(const Value *V, unsigned CharSize = 8); 298 299 /// This function returns call pointer argument that is considered the same by 300 /// aliasing rules. You CAN'T use it to replace one value with another. 301 const Value *getArgumentAliasingToReturnedPointer(const CallBase *Call); getArgumentAliasingToReturnedPointer(CallBase * Call)302 inline Value *getArgumentAliasingToReturnedPointer(CallBase *Call) { 303 return const_cast<Value *>(getArgumentAliasingToReturnedPointer( 304 const_cast<const CallBase *>(Call))); 305 } 306 307 // {launder,strip}.invariant.group returns pointer that aliases its argument, 308 // and it only captures pointer by returning it. 309 // These intrinsics are not marked as nocapture, because returning is 310 // considered as capture. The arguments are not marked as returned neither, 311 // because it would make it useless. 312 bool isIntrinsicReturningPointerAliasingArgumentWithoutCapturing( 313 const CallBase *Call); 314 315 /// This method strips off any GEP address adjustments and pointer casts from 316 /// the specified value, returning the original object being addressed. Note 317 /// that the returned value has pointer type if the specified value does. If 318 /// the MaxLookup value is non-zero, it limits the number of instructions to 319 /// be stripped off. 320 Value *GetUnderlyingObject(Value *V, const DataLayout &DL, 321 unsigned MaxLookup = 6); 322 inline const Value *GetUnderlyingObject(const Value *V, const DataLayout &DL, 323 unsigned MaxLookup = 6) { 324 return GetUnderlyingObject(const_cast<Value *>(V), DL, MaxLookup); 325 } 326 327 /// This method is similar to GetUnderlyingObject except that it can 328 /// look through phi and select instructions and return multiple objects. 329 /// 330 /// If LoopInfo is passed, loop phis are further analyzed. If a pointer 331 /// accesses different objects in each iteration, we don't look through the 332 /// phi node. E.g. consider this loop nest: 333 /// 334 /// int **A; 335 /// for (i) 336 /// for (j) { 337 /// A[i][j] = A[i-1][j] * B[j] 338 /// } 339 /// 340 /// This is transformed by Load-PRE to stash away A[i] for the next iteration 341 /// of the outer loop: 342 /// 343 /// Curr = A[0]; // Prev_0 344 /// for (i: 1..N) { 345 /// Prev = Curr; // Prev = PHI (Prev_0, Curr) 346 /// Curr = A[i]; 347 /// for (j: 0..N) { 348 /// Curr[j] = Prev[j] * B[j] 349 /// } 350 /// } 351 /// 352 /// Since A[i] and A[i-1] are independent pointers, getUnderlyingObjects 353 /// should not assume that Curr and Prev share the same underlying object thus 354 /// it shouldn't look through the phi above. 355 void GetUnderlyingObjects(Value *V, SmallVectorImpl<Value *> &Objects, 356 const DataLayout &DL, LoopInfo *LI = nullptr, 357 unsigned MaxLookup = 6); 358 359 /// This is a wrapper around GetUnderlyingObjects and adds support for basic 360 /// ptrtoint+arithmetic+inttoptr sequences. 361 bool getUnderlyingObjectsForCodeGen(const Value *V, 362 SmallVectorImpl<Value *> &Objects, 363 const DataLayout &DL); 364 365 /// Return true if the only users of this pointer are lifetime markers. 366 bool onlyUsedByLifetimeMarkers(const Value *V); 367 368 /// Return true if the instruction does not have any effects besides 369 /// calculating the result and does not have undefined behavior. 370 /// 371 /// This method never returns true for an instruction that returns true for 372 /// mayHaveSideEffects; however, this method also does some other checks in 373 /// addition. It checks for undefined behavior, like dividing by zero or 374 /// loading from an invalid pointer (but not for undefined results, like a 375 /// shift with a shift amount larger than the width of the result). It checks 376 /// for malloc and alloca because speculatively executing them might cause a 377 /// memory leak. It also returns false for instructions related to control 378 /// flow, specifically terminators and PHI nodes. 379 /// 380 /// If the CtxI is specified this method performs context-sensitive analysis 381 /// and returns true if it is safe to execute the instruction immediately 382 /// before the CtxI. 383 /// 384 /// If the CtxI is NOT specified this method only looks at the instruction 385 /// itself and its operands, so if this method returns true, it is safe to 386 /// move the instruction as long as the correct dominance relationships for 387 /// the operands and users hold. 388 /// 389 /// This method can return true for instructions that read memory; 390 /// for such instructions, moving them may change the resulting value. 391 bool isSafeToSpeculativelyExecute(const Value *V, 392 const Instruction *CtxI = nullptr, 393 const DominatorTree *DT = nullptr); 394 395 /// Returns true if the result or effects of the given instructions \p I 396 /// depend on or influence global memory. 397 /// Memory dependence arises for example if the instruction reads from 398 /// memory or may produce effects or undefined behaviour. Memory dependent 399 /// instructions generally cannot be reorderd with respect to other memory 400 /// dependent instructions or moved into non-dominated basic blocks. 401 /// Instructions which just compute a value based on the values of their 402 /// operands are not memory dependent. 403 bool mayBeMemoryDependent(const Instruction &I); 404 405 /// Return true if it is an intrinsic that cannot be speculated but also 406 /// cannot trap. 407 bool isAssumeLikeIntrinsic(const Instruction *I); 408 409 /// Return true if it is valid to use the assumptions provided by an 410 /// assume intrinsic, I, at the point in the control-flow identified by the 411 /// context instruction, CxtI. 412 bool isValidAssumeForContext(const Instruction *I, const Instruction *CxtI, 413 const DominatorTree *DT = nullptr); 414 415 enum class OverflowResult { AlwaysOverflows, MayOverflow, NeverOverflows }; 416 417 OverflowResult computeOverflowForUnsignedMul(const Value *LHS, 418 const Value *RHS, 419 const DataLayout &DL, 420 AssumptionCache *AC, 421 const Instruction *CxtI, 422 const DominatorTree *DT, 423 bool UseInstrInfo = true); 424 OverflowResult computeOverflowForSignedMul(const Value *LHS, const Value *RHS, 425 const DataLayout &DL, 426 AssumptionCache *AC, 427 const Instruction *CxtI, 428 const DominatorTree *DT, 429 bool UseInstrInfo = true); 430 OverflowResult computeOverflowForUnsignedAdd(const Value *LHS, 431 const Value *RHS, 432 const DataLayout &DL, 433 AssumptionCache *AC, 434 const Instruction *CxtI, 435 const DominatorTree *DT, 436 bool UseInstrInfo = true); 437 OverflowResult computeOverflowForSignedAdd(const Value *LHS, const Value *RHS, 438 const DataLayout &DL, 439 AssumptionCache *AC = nullptr, 440 const Instruction *CxtI = nullptr, 441 const DominatorTree *DT = nullptr); 442 /// This version also leverages the sign bit of Add if known. 443 OverflowResult computeOverflowForSignedAdd(const AddOperator *Add, 444 const DataLayout &DL, 445 AssumptionCache *AC = nullptr, 446 const Instruction *CxtI = nullptr, 447 const DominatorTree *DT = nullptr); 448 OverflowResult computeOverflowForUnsignedSub(const Value *LHS, const Value *RHS, 449 const DataLayout &DL, 450 AssumptionCache *AC, 451 const Instruction *CxtI, 452 const DominatorTree *DT); 453 OverflowResult computeOverflowForSignedSub(const Value *LHS, const Value *RHS, 454 const DataLayout &DL, 455 AssumptionCache *AC, 456 const Instruction *CxtI, 457 const DominatorTree *DT); 458 459 /// Returns true if the arithmetic part of the \p II 's result is 460 /// used only along the paths control dependent on the computation 461 /// not overflowing, \p II being an <op>.with.overflow intrinsic. 462 bool isOverflowIntrinsicNoWrap(const IntrinsicInst *II, 463 const DominatorTree &DT); 464 465 /// Return true if this function can prove that the instruction I will 466 /// always transfer execution to one of its successors (including the next 467 /// instruction that follows within a basic block). E.g. this is not 468 /// guaranteed for function calls that could loop infinitely. 469 /// 470 /// In other words, this function returns false for instructions that may 471 /// transfer execution or fail to transfer execution in a way that is not 472 /// captured in the CFG nor in the sequence of instructions within a basic 473 /// block. 474 /// 475 /// Undefined behavior is assumed not to happen, so e.g. division is 476 /// guaranteed to transfer execution to the following instruction even 477 /// though division by zero might cause undefined behavior. 478 bool isGuaranteedToTransferExecutionToSuccessor(const Instruction *I); 479 480 /// Returns true if this block does not contain a potential implicit exit. 481 /// This is equivelent to saying that all instructions within the basic block 482 /// are guaranteed to transfer execution to their successor within the basic 483 /// block. This has the same assumptions w.r.t. undefined behavior as the 484 /// instruction variant of this function. 485 bool isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB); 486 487 /// Return true if this function can prove that the instruction I 488 /// is executed for every iteration of the loop L. 489 /// 490 /// Note that this currently only considers the loop header. 491 bool isGuaranteedToExecuteForEveryIteration(const Instruction *I, 492 const Loop *L); 493 494 /// Return true if this function can prove that I is guaranteed to yield 495 /// full-poison (all bits poison) if at least one of its operands are 496 /// full-poison (all bits poison). 497 /// 498 /// The exact rules for how poison propagates through instructions have 499 /// not been settled as of 2015-07-10, so this function is conservative 500 /// and only considers poison to be propagated in uncontroversial 501 /// cases. There is no attempt to track values that may be only partially 502 /// poison. 503 bool propagatesFullPoison(const Instruction *I); 504 505 /// Return either nullptr or an operand of I such that I will trigger 506 /// undefined behavior if I is executed and that operand has a full-poison 507 /// value (all bits poison). 508 const Value *getGuaranteedNonFullPoisonOp(const Instruction *I); 509 510 /// Return true if the given instruction must trigger undefined behavior. 511 /// when I is executed with any operands which appear in KnownPoison holding 512 /// a full-poison value at the point of execution. 513 bool mustTriggerUB(const Instruction *I, 514 const SmallSet<const Value *, 16>& KnownPoison); 515 516 /// Return true if this function can prove that if PoisonI is executed 517 /// and yields a full-poison value (all bits poison), then that will 518 /// trigger undefined behavior. 519 /// 520 /// Note that this currently only considers the basic block that is 521 /// the parent of I. 522 bool programUndefinedIfFullPoison(const Instruction *PoisonI); 523 524 /// Specific patterns of select instructions we can match. 525 enum SelectPatternFlavor { 526 SPF_UNKNOWN = 0, 527 SPF_SMIN, /// Signed minimum 528 SPF_UMIN, /// Unsigned minimum 529 SPF_SMAX, /// Signed maximum 530 SPF_UMAX, /// Unsigned maximum 531 SPF_FMINNUM, /// Floating point minnum 532 SPF_FMAXNUM, /// Floating point maxnum 533 SPF_ABS, /// Absolute value 534 SPF_NABS /// Negated absolute value 535 }; 536 537 /// Behavior when a floating point min/max is given one NaN and one 538 /// non-NaN as input. 539 enum SelectPatternNaNBehavior { 540 SPNB_NA = 0, /// NaN behavior not applicable. 541 SPNB_RETURNS_NAN, /// Given one NaN input, returns the NaN. 542 SPNB_RETURNS_OTHER, /// Given one NaN input, returns the non-NaN. 543 SPNB_RETURNS_ANY /// Given one NaN input, can return either (or 544 /// it has been determined that no operands can 545 /// be NaN). 546 }; 547 548 struct SelectPatternResult { 549 SelectPatternFlavor Flavor; 550 SelectPatternNaNBehavior NaNBehavior; /// Only applicable if Flavor is 551 /// SPF_FMINNUM or SPF_FMAXNUM. 552 bool Ordered; /// When implementing this min/max pattern as 553 /// fcmp; select, does the fcmp have to be 554 /// ordered? 555 556 /// Return true if \p SPF is a min or a max pattern. isMinOrMaxSelectPatternResult557 static bool isMinOrMax(SelectPatternFlavor SPF) { 558 return SPF != SPF_UNKNOWN && SPF != SPF_ABS && SPF != SPF_NABS; 559 } 560 }; 561 562 /// Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind 563 /// and providing the out parameter results if we successfully match. 564 /// 565 /// For ABS/NABS, LHS will be set to the input to the abs idiom. RHS will be 566 /// the negation instruction from the idiom. 567 /// 568 /// If CastOp is not nullptr, also match MIN/MAX idioms where the type does 569 /// not match that of the original select. If this is the case, the cast 570 /// operation (one of Trunc,SExt,Zext) that must be done to transform the 571 /// type of LHS and RHS into the type of V is returned in CastOp. 572 /// 573 /// For example: 574 /// %1 = icmp slt i32 %a, i32 4 575 /// %2 = sext i32 %a to i64 576 /// %3 = select i1 %1, i64 %2, i64 4 577 /// 578 /// -> LHS = %a, RHS = i32 4, *CastOp = Instruction::SExt 579 /// 580 SelectPatternResult matchSelectPattern(Value *V, Value *&LHS, Value *&RHS, 581 Instruction::CastOps *CastOp = nullptr, 582 unsigned Depth = 0); 583 inline SelectPatternResult 584 matchSelectPattern(const Value *V, const Value *&LHS, const Value *&RHS, 585 Instruction::CastOps *CastOp = nullptr) { 586 Value *L = const_cast<Value*>(LHS); 587 Value *R = const_cast<Value*>(RHS); 588 auto Result = matchSelectPattern(const_cast<Value*>(V), L, R); 589 LHS = L; 590 RHS = R; 591 return Result; 592 } 593 594 /// Return the canonical comparison predicate for the specified 595 /// minimum/maximum flavor. 596 CmpInst::Predicate getMinMaxPred(SelectPatternFlavor SPF, 597 bool Ordered = false); 598 599 /// Return the inverse minimum/maximum flavor of the specified flavor. 600 /// For example, signed minimum is the inverse of signed maximum. 601 SelectPatternFlavor getInverseMinMaxFlavor(SelectPatternFlavor SPF); 602 603 /// Return the canonical inverse comparison predicate for the specified 604 /// minimum/maximum flavor. 605 CmpInst::Predicate getInverseMinMaxPred(SelectPatternFlavor SPF); 606 607 /// Return true if RHS is known to be implied true by LHS. Return false if 608 /// RHS is known to be implied false by LHS. Otherwise, return None if no 609 /// implication can be made. 610 /// A & B must be i1 (boolean) values or a vector of such values. Note that 611 /// the truth table for implication is the same as <=u on i1 values (but not 612 /// <=s!). The truth table for both is: 613 /// | T | F (B) 614 /// T | T | F 615 /// F | T | T 616 /// (A) 617 Optional<bool> isImpliedCondition(const Value *LHS, const Value *RHS, 618 const DataLayout &DL, bool LHSIsTrue = true, 619 unsigned Depth = 0); 620 621 /// Return the boolean condition value in the context of the given instruction 622 /// if it is known based on dominating conditions. 623 Optional<bool> isImpliedByDomCondition(const Value *Cond, 624 const Instruction *ContextI, 625 const DataLayout &DL); 626 } // end namespace llvm 627 628 #endif // LLVM_ANALYSIS_VALUETRACKING_H 629