LLVM  9.0.0svn
ValueTracking.h
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1 //===- llvm/Analysis/ValueTracking.h - Walk computations --------*- 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 // This file contains routines that help analyze properties that chains of
10 // computations have.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_ANALYSIS_VALUETRACKING_H
15 #define LLVM_ANALYSIS_VALUETRACKING_H
16 
17 #include "llvm/ADT/ArrayRef.h"
18 #include "llvm/ADT/Optional.h"
19 #include "llvm/ADT/SmallSet.h"
20 #include "llvm/IR/CallSite.h"
21 #include "llvm/IR/Constants.h"
22 #include "llvm/IR/Instruction.h"
23 #include "llvm/IR/Intrinsics.h"
24 #include <cassert>
25 #include <cstdint>
26 
27 namespace llvm {
28 
29 class AddOperator;
30 class APInt;
31 class AssumptionCache;
32 class DataLayout;
33 class DominatorTree;
34 class GEPOperator;
35 class IntrinsicInst;
36 class WithOverflowInst;
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.
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.
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.
242  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.
253  unsigned CharSize = 8);
254 
255  /// Represents offset+length into a ConstantDataArray.
257  /// ConstantDataArray pointer. nullptr indicates a zeroinitializer (a valid
258  /// initializer, it just doesn't fit the ConstantDataArray interface).
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.
268  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.
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.
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.
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(const Value *V,
357  const DataLayout &DL, LoopInfo *LI = nullptr,
358  unsigned MaxLookup = 6);
359 
360  /// This is a wrapper around GetUnderlyingObjects and adds support for basic
361  /// ptrtoint+arithmetic+inttoptr sequences.
363  SmallVectorImpl<Value *> &Objects,
364  const DataLayout &DL);
365 
366  /// Return true if the only users of this pointer are lifetime markers.
367  bool onlyUsedByLifetimeMarkers(const Value *V);
368 
369  /// Return true if the instruction does not have any effects besides
370  /// calculating the result and does not have undefined behavior.
371  ///
372  /// This method never returns true for an instruction that returns true for
373  /// mayHaveSideEffects; however, this method also does some other checks in
374  /// addition. It checks for undefined behavior, like dividing by zero or
375  /// loading from an invalid pointer (but not for undefined results, like a
376  /// shift with a shift amount larger than the width of the result). It checks
377  /// for malloc and alloca because speculatively executing them might cause a
378  /// memory leak. It also returns false for instructions related to control
379  /// flow, specifically terminators and PHI nodes.
380  ///
381  /// If the CtxI is specified this method performs context-sensitive analysis
382  /// and returns true if it is safe to execute the instruction immediately
383  /// before the CtxI.
384  ///
385  /// If the CtxI is NOT specified this method only looks at the instruction
386  /// itself and its operands, so if this method returns true, it is safe to
387  /// move the instruction as long as the correct dominance relationships for
388  /// the operands and users hold.
389  ///
390  /// This method can return true for instructions that read memory;
391  /// for such instructions, moving them may change the resulting value.
392  bool isSafeToSpeculativelyExecute(const Value *V,
393  const Instruction *CtxI = nullptr,
394  const DominatorTree *DT = nullptr);
395 
396  /// Returns true if the result or effects of the given instructions \p I
397  /// depend on or influence global memory.
398  /// Memory dependence arises for example if the instruction reads from
399  /// memory or may produce effects or undefined behaviour. Memory dependent
400  /// instructions generally cannot be reorderd with respect to other memory
401  /// dependent instructions or moved into non-dominated basic blocks.
402  /// Instructions which just compute a value based on the values of their
403  /// operands are not memory dependent.
404  bool mayBeMemoryDependent(const Instruction &I);
405 
406  /// Return true if it is an intrinsic that cannot be speculated but also
407  /// cannot trap.
408  bool isAssumeLikeIntrinsic(const Instruction *I);
409 
410  /// Return true if it is valid to use the assumptions provided by an
411  /// assume intrinsic, I, at the point in the control-flow identified by the
412  /// context instruction, CxtI.
413  bool isValidAssumeForContext(const Instruction *I, const Instruction *CxtI,
414  const DominatorTree *DT = nullptr);
415 
416  enum class OverflowResult {
417  /// Always overflows in the direction of signed/unsigned min value.
419  /// Always overflows in the direction of signed/unsigned max value.
421  /// May or may not overflow.
422  MayOverflow,
423  /// Never overflows.
425  };
426 
428  const Value *RHS,
429  const DataLayout &DL,
430  AssumptionCache *AC,
431  const Instruction *CxtI,
432  const DominatorTree *DT,
433  bool UseInstrInfo = true);
434  OverflowResult computeOverflowForSignedMul(const Value *LHS, const Value *RHS,
435  const DataLayout &DL,
436  AssumptionCache *AC,
437  const Instruction *CxtI,
438  const DominatorTree *DT,
439  bool UseInstrInfo = true);
441  const Value *RHS,
442  const DataLayout &DL,
443  AssumptionCache *AC,
444  const Instruction *CxtI,
445  const DominatorTree *DT,
446  bool UseInstrInfo = true);
447  OverflowResult computeOverflowForSignedAdd(const Value *LHS, const Value *RHS,
448  const DataLayout &DL,
449  AssumptionCache *AC = nullptr,
450  const Instruction *CxtI = nullptr,
451  const DominatorTree *DT = nullptr);
452  /// This version also leverages the sign bit of Add if known.
454  const DataLayout &DL,
455  AssumptionCache *AC = nullptr,
456  const Instruction *CxtI = nullptr,
457  const DominatorTree *DT = nullptr);
459  const DataLayout &DL,
460  AssumptionCache *AC,
461  const Instruction *CxtI,
462  const DominatorTree *DT);
463  OverflowResult computeOverflowForSignedSub(const Value *LHS, const Value *RHS,
464  const DataLayout &DL,
465  AssumptionCache *AC,
466  const Instruction *CxtI,
467  const DominatorTree *DT);
468 
469  /// Returns true if the arithmetic part of the \p WO 's result is
470  /// used only along the paths control dependent on the computation
471  /// not overflowing, \p WO being an <op>.with.overflow intrinsic.
473  const DominatorTree &DT);
474 
475 
476  /// Determine the possible constant range of an integer or vector of integer
477  /// value. This is intended as a cheap, non-recursive check.
478  ConstantRange computeConstantRange(const Value *V, bool UseInstrInfo = true);
479 
480  /// Return true if this function can prove that the instruction I will
481  /// always transfer execution to one of its successors (including the next
482  /// instruction that follows within a basic block). E.g. this is not
483  /// guaranteed for function calls that could loop infinitely.
484  ///
485  /// In other words, this function returns false for instructions that may
486  /// transfer execution or fail to transfer execution in a way that is not
487  /// captured in the CFG nor in the sequence of instructions within a basic
488  /// block.
489  ///
490  /// Undefined behavior is assumed not to happen, so e.g. division is
491  /// guaranteed to transfer execution to the following instruction even
492  /// though division by zero might cause undefined behavior.
494 
495  /// Returns true if this block does not contain a potential implicit exit.
496  /// This is equivelent to saying that all instructions within the basic block
497  /// are guaranteed to transfer execution to their successor within the basic
498  /// block. This has the same assumptions w.r.t. undefined behavior as the
499  /// instruction variant of this function.
501 
502  /// Return true if this function can prove that the instruction I
503  /// is executed for every iteration of the loop L.
504  ///
505  /// Note that this currently only considers the loop header.
507  const Loop *L);
508 
509  /// Return true if this function can prove that I is guaranteed to yield
510  /// full-poison (all bits poison) if at least one of its operands are
511  /// full-poison (all bits poison).
512  ///
513  /// The exact rules for how poison propagates through instructions have
514  /// not been settled as of 2015-07-10, so this function is conservative
515  /// and only considers poison to be propagated in uncontroversial
516  /// cases. There is no attempt to track values that may be only partially
517  /// poison.
518  bool propagatesFullPoison(const Instruction *I);
519 
520  /// Return either nullptr or an operand of I such that I will trigger
521  /// undefined behavior if I is executed and that operand has a full-poison
522  /// value (all bits poison).
524 
525  /// Return true if the given instruction must trigger undefined behavior.
526  /// when I is executed with any operands which appear in KnownPoison holding
527  /// a full-poison value at the point of execution.
528  bool mustTriggerUB(const Instruction *I,
529  const SmallSet<const Value *, 16>& KnownPoison);
530 
531  /// Return true if this function can prove that if PoisonI is executed
532  /// and yields a full-poison value (all bits poison), then that will
533  /// trigger undefined behavior.
534  ///
535  /// Note that this currently only considers the basic block that is
536  /// the parent of I.
537  bool programUndefinedIfFullPoison(const Instruction *PoisonI);
538 
539  /// Specific patterns of select instructions we can match.
542  SPF_SMIN, /// Signed minimum
543  SPF_UMIN, /// Unsigned minimum
544  SPF_SMAX, /// Signed maximum
545  SPF_UMAX, /// Unsigned maximum
546  SPF_FMINNUM, /// Floating point minnum
547  SPF_FMAXNUM, /// Floating point maxnum
548  SPF_ABS, /// Absolute value
549  SPF_NABS /// Negated absolute value
550  };
551 
552  /// Behavior when a floating point min/max is given one NaN and one
553  /// non-NaN as input.
555  SPNB_NA = 0, /// NaN behavior not applicable.
556  SPNB_RETURNS_NAN, /// Given one NaN input, returns the NaN.
557  SPNB_RETURNS_OTHER, /// Given one NaN input, returns the non-NaN.
558  SPNB_RETURNS_ANY /// Given one NaN input, can return either (or
559  /// it has been determined that no operands can
560  /// be NaN).
561  };
562 
565  SelectPatternNaNBehavior NaNBehavior; /// Only applicable if Flavor is
566  /// SPF_FMINNUM or SPF_FMAXNUM.
567  bool Ordered; /// When implementing this min/max pattern as
568  /// fcmp; select, does the fcmp have to be
569  /// ordered?
570 
571  /// Return true if \p SPF is a min or a max pattern.
572  static bool isMinOrMax(SelectPatternFlavor SPF) {
573  return SPF != SPF_UNKNOWN && SPF != SPF_ABS && SPF != SPF_NABS;
574  }
575  };
576 
577  /// Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind
578  /// and providing the out parameter results if we successfully match.
579  ///
580  /// For ABS/NABS, LHS will be set to the input to the abs idiom. RHS will be
581  /// the negation instruction from the idiom.
582  ///
583  /// If CastOp is not nullptr, also match MIN/MAX idioms where the type does
584  /// not match that of the original select. If this is the case, the cast
585  /// operation (one of Trunc,SExt,Zext) that must be done to transform the
586  /// type of LHS and RHS into the type of V is returned in CastOp.
587  ///
588  /// For example:
589  /// %1 = icmp slt i32 %a, i32 4
590  /// %2 = sext i32 %a to i64
591  /// %3 = select i1 %1, i64 %2, i64 4
592  ///
593  /// -> LHS = %a, RHS = i32 4, *CastOp = Instruction::SExt
594  ///
596  Instruction::CastOps *CastOp = nullptr,
597  unsigned Depth = 0);
598  inline SelectPatternResult
599  matchSelectPattern(const Value *V, const Value *&LHS, const Value *&RHS,
600  Instruction::CastOps *CastOp = nullptr) {
601  Value *L = const_cast<Value*>(LHS);
602  Value *R = const_cast<Value*>(RHS);
603  auto Result = matchSelectPattern(const_cast<Value*>(V), L, R);
604  LHS = L;
605  RHS = R;
606  return Result;
607  }
608 
609  /// Determine the pattern that a select with the given compare as its
610  /// predicate and given values as its true/false operands would match.
612  CmpInst *CmpI, Value *TrueVal, Value *FalseVal, Value *&LHS, Value *&RHS,
613  Instruction::CastOps *CastOp = nullptr, unsigned Depth = 0);
614 
615  /// Return the canonical comparison predicate for the specified
616  /// minimum/maximum flavor.
618  bool Ordered = false);
619 
620  /// Return the inverse minimum/maximum flavor of the specified flavor.
621  /// For example, signed minimum is the inverse of signed maximum.
623 
624  /// Return the canonical inverse comparison predicate for the specified
625  /// minimum/maximum flavor.
627 
628  /// Return true if RHS is known to be implied true by LHS. Return false if
629  /// RHS is known to be implied false by LHS. Otherwise, return None if no
630  /// implication can be made.
631  /// A & B must be i1 (boolean) values or a vector of such values. Note that
632  /// the truth table for implication is the same as <=u on i1 values (but not
633  /// <=s!). The truth table for both is:
634  /// | T | F (B)
635  /// T | T | F
636  /// F | T | T
637  /// (A)
638  Optional<bool> isImpliedCondition(const Value *LHS, const Value *RHS,
639  const DataLayout &DL, bool LHSIsTrue = true,
640  unsigned Depth = 0);
641 
642  /// Return the boolean condition value in the context of the given instruction
643  /// if it is known based on dominating conditions.
645  const Instruction *ContextI,
646  const DataLayout &DL);
647 } // end namespace llvm
648 
649 #endif // LLVM_ANALYSIS_VALUETRACKING_H
const Value * getGuaranteedNonFullPoisonOp(const Instruction *I)
Return either nullptr or an operand of I such that I will trigger undefined behavior if I is executed...
bool isKnownPositive(const Value *V, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Returns true if the given value is known be positive (i.e.
void computeKnownBits(const Value *V, KnownBits &Known, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, OptimizationRemarkEmitter *ORE=nullptr, bool UseInstrInfo=true)
Determine which bits of V are known to be either zero or one and return them in the KnownZero/KnownOn...
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:110
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:722
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
bool isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI)
Unsigned minimum.
This class represents lattice values for constants.
Definition: AllocatorList.h:23
Value * isBytewiseValue(Value *V)
If the specified value can be set by repeating the same byte in memory, return the i8 value that it i...
Represents an op.with.overflow intrinsic.
Optional< bool > isImpliedByDomCondition(const Value *Cond, const Instruction *ContextI, const DataLayout &DL)
Return the boolean condition value in the context of the given instruction if it is known based on do...
bool isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(const CallBase *Call)
A cache of @llvm.assume calls within a function.
Always overflows in the direction of signed/unsigned min value.
bool isValidAssumeForContext(const Instruction *I, const Instruction *CxtI, const DominatorTree *DT=nullptr)
Return true if it is valid to use the assumptions provided by an assume intrinsic, I, at the point in the control-flow identified by the context instruction, CxtI.
SelectPatternFlavor getInverseMinMaxFlavor(SelectPatternFlavor SPF)
Return the inverse minimum/maximum flavor of the specified flavor.
Base class for all callable instructions (InvokeInst and CallInst) Holds everything related to callin...
Definition: InstrTypes.h:1100
ConstantRange computeConstantRange(const Value *V, bool UseInstrInfo=true)
Determine the possible constant range of an integer or vector of integer value.
Hexagon Common GEP
bool isGEPBasedOnPointerToString(const GEPOperator *GEP, unsigned CharSize=8)
Returns true if the GEP is based on a pointer to a string (array of.
uint64_t Offset
Slice starts at this Offset.
bool Ordered
Only applicable if Flavor is SPF_FMINNUM or SPF_FMAXNUM.
bool propagatesFullPoison(const Instruction *I)
Return true if this function can prove that I is guaranteed to yield full-poison (all bits poison) if...
Signed maximum.
Intrinsic::ID getIntrinsicForCallSite(ImmutableCallSite ICS, const TargetLibraryInfo *TLI)
Map a call instruction to an intrinsic ID.
static GCMetadataPrinterRegistry::Add< OcamlGCMetadataPrinter > Y("ocaml", "ocaml 3.10-compatible collector")
bool isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL, bool OrZero=false, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Return true if the given value is known to have exactly one bit set when defined. ...
Absolute value.
OverflowResult computeOverflowForUnsignedAdd(const Value *LHS, const Value *RHS, const DataLayout &DL, AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT, bool UseInstrInfo=true)
NaN behavior not applicable.
bool MaskedValueIsZero(const Value *V, const APInt &Mask, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Return true if &#39;V & Mask&#39; is known to be zero.
bool programUndefinedIfFullPoison(const Instruction *PoisonI)
Return true if this function can prove that if PoisonI is executed and yields a full-poison value (al...
uint64_t operator[](unsigned I) const
Convenience accessor for elements in the slice.
bool isOverflowIntrinsicNoWrap(const WithOverflowInst *WO, const DominatorTree &DT)
Returns true if the arithmetic part of the WO &#39;s result is used only along the paths control dependen...
const ConstantDataArray * Array
ConstantDataArray pointer.
May or may not overflow.
Value * GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset, const DataLayout &DL)
Analyze the specified pointer to see if it can be expressed as a base pointer plus a constant offset...
SelectPatternResult matchDecomposedSelectPattern(CmpInst *CmpI, Value *TrueVal, Value *FalseVal, Value *&LHS, Value *&RHS, Instruction::CastOps *CastOp=nullptr, unsigned Depth=0)
Determine the pattern that a select with the given compare as its predicate and given values as its t...
OverflowResult computeOverflowForSignedMul(const Value *LHS, const Value *RHS, const DataLayout &DL, AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT, bool UseInstrInfo=true)
bool isKnownNonNegative(const Value *V, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Returns true if the give value is known to be non-negative.
uint64_t GetStringLength(const Value *V, unsigned CharSize=8)
If we can compute the length of the string pointed to by the specified pointer, return &#39;len+1&#39;...
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:144
bool CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI, unsigned Depth=0)
Return true if we can prove that the specified FP value is never equal to -0.0.
bool getConstantDataArrayInfo(const Value *V, ConstantDataArraySlice &Slice, unsigned ElementSize, uint64_t Offset=0)
Returns true if the value V is a pointer into a ConstantDataArray.
unsigned ComputeNumSignBits(const Value *Op, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Return the number of times the sign bit of the register is replicated into the other bits...
bool isGuaranteedToTransferExecutionToSuccessor(const Instruction *I)
Return true if this function can prove that the instruction I will always transfer execution to one o...
void GetUnderlyingObjects(const Value *V, SmallVectorImpl< const Value *> &Objects, const DataLayout &DL, LoopInfo *LI=nullptr, unsigned MaxLookup=6)
This method is similar to GetUnderlyingObject except that it can look through phi and select instruct...
OverflowResult computeOverflowForSignedAdd(const Value *LHS, const Value *RHS, const DataLayout &DL, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr)
bool isKnownNegation(const Value *X, const Value *Y, bool NeedNSW=false)
Return true if the two given values are negation.
An array constant whose element type is a simple 1/2/4/8-byte integer or float/double, and whose elements are just simple data values (i.e.
Definition: Constants.h:689
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
SmallSet - This maintains a set of unique values, optimizing for the case when the set is small (less...
Definition: SmallSet.h:134
This file contains the declarations for the subclasses of Constant, which represent the different fla...
bool onlyUsedByLifetimeMarkers(const Value *V)
Return true if the only users of this pointer are lifetime markers.
bool getUnderlyingObjectsForCodeGen(const Value *V, SmallVectorImpl< Value *> &Objects, const DataLayout &DL)
This is a wrapper around GetUnderlyingObjects and adds support for basic ptrtoint+arithmetic+inttoptr...
bool mustTriggerUB(const Instruction *I, const SmallSet< const Value *, 16 > &KnownPoison)
Return true if the given instruction must trigger undefined behavior.
Predicate
This enumeration lists the possible predicates for CmpInst subclasses.
Definition: InstrTypes.h:732
CmpInst::Predicate getMinMaxPred(SelectPatternFlavor SPF, bool Ordered=false)
Return the canonical comparison predicate for the specified minimum/maximum flavor.
SelectPatternNaNBehavior
Behavior when a floating point min/max is given one NaN and one non-NaN as input. ...
Represents offset+length into a ConstantDataArray.
CmpInst::Predicate getInverseMinMaxPred(SelectPatternFlavor SPF)
Return the canonical inverse comparison predicate for the specified minimum/maximum flavor...
bool isAssumeLikeIntrinsic(const Instruction *I)
Return true if it is an intrinsic that cannot be speculated but also cannot trap. ...
Value * GetUnderlyingObject(Value *V, const DataLayout &DL, unsigned MaxLookup=6)
This method strips off any GEP address adjustments and pointer casts from the specified value...
const Value * getArgumentAliasingToReturnedPointer(const CallBase *Call)
This function returns call pointer argument that is considered the same by aliasing rules...
Value * FindInsertedValue(Value *V, ArrayRef< unsigned > idx_range, Instruction *InsertBefore=nullptr)
Given an aggregrate and an sequence of indices, see if the scalar value indexed is already around as ...
Floating point maxnum.
Given one NaN input, returns the non-NaN.
SelectPatternFlavor Flavor
Unsigned maximum.
uint64_t getElementAsInteger(unsigned i) const
If this is a sequential container of integers (of any size), return the specified element in the low ...
Definition: Constants.cpp:2670
uint64_t Length
Length of the slice.
SelectPatternFlavor
Specific patterns of select instructions we can match.
This class represents a range of values.
Definition: ConstantRange.h:47
Floating point minnum.
SelectPatternNaNBehavior NaNBehavior
void computeKnownBitsFromRangeMetadata(const MDNode &Ranges, KnownBits &Known)
Compute known bits from the range metadata.
bool isKnownNonZero(const Value *V, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Return true if the given value is known to be non-zero when defined.
Always overflows in the direction of signed/unsigned max value.
bool mayBeMemoryDependent(const Instruction &I)
Returns true if the result or effects of the given instructions I depend on or influence global memor...
OverflowResult
bool isKnownNegative(const Value *V, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Returns true if the given value is known be negative (i.e.
static bool isMinOrMax(SelectPatternFlavor SPF)
When implementing this min/max pattern as fcmp; select, does the fcmp have to be ordered?
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:467
bool isKnownNonEqual(const Value *V1, const Value *V2, const DataLayout &DL, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Return true if the given values are known to be non-equal when defined.
#define I(x, y, z)
Definition: MD5.cpp:58
bool haveNoCommonBitsSet(const Value *LHS, const Value *RHS, const DataLayout &DL, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Return true if LHS and RHS have no common bits set.
bool SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI)
Return true if we can prove that the specified FP value&#39;s sign bit is 0.
bool ComputeMultiple(Value *V, unsigned Base, Value *&Multiple, bool LookThroughSExt=false, unsigned Depth=0)
This function computes the integer multiple of Base that equals V.
bool isGuaranteedToExecuteForEveryIteration(const Instruction *I, const Loop *L)
Return true if this function can prove that the instruction I is executed for every iteration of the ...
bool isKnownNeverNaN(const Value *V, const TargetLibraryInfo *TLI, unsigned Depth=0)
Return true if the floating-point scalar value is not a NaN or if the floating-point vector value has...
Signed minimum.
Optional< bool > isImpliedCondition(const Value *LHS, const Value *RHS, const DataLayout &DL, bool LHSIsTrue=true, unsigned Depth=0)
Return true if RHS is known to be implied true by LHS.
bool getConstantStringInfo(const Value *V, StringRef &Str, uint64_t Offset=0, bool TrimAtNul=true)
This function computes the length of a null-terminated C string pointed to by V.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Given one NaN input, returns the NaN.
bool isSafeToSpeculativelyExecute(const Value *V, const Instruction *CtxI=nullptr, const DominatorTree *DT=nullptr)
Return true if the instruction does not have any effects besides calculating the result and does not ...
LLVM Value Representation.
Definition: Value.h:72
SelectPatternResult matchSelectPattern(Value *V, Value *&LHS, Value *&RHS, Instruction::CastOps *CastOp=nullptr, unsigned Depth=0)
Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind and providing the out param...
std::underlying_type< E >::type Mask()
Get a bitmask with 1s in all places up to the high-order bit of E&#39;s largest value.
Definition: BitmaskEnum.h:80
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
void move(uint64_t Delta)
Moves the Offset and adjusts Length accordingly.
OverflowResult computeOverflowForUnsignedMul(const Value *LHS, const Value *RHS, const DataLayout &DL, AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT, bool UseInstrInfo=true)
bool CannotBeOrderedLessThanZero(const Value *V, const TargetLibraryInfo *TLI)
Return true if we can prove that the specified FP value is either NaN or never less than -0...
OverflowResult computeOverflowForSignedSub(const Value *LHS, const Value *RHS, const DataLayout &DL, AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT)
OverflowResult computeOverflowForUnsignedSub(const Value *LHS, const Value *RHS, const DataLayout &DL, AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT)