LLVM  8.0.0svn
ValueTracking.h
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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/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 struct KnownBits;
37 class Loop;
38 class LoopInfo;
39 class MDNode;
40 class OptimizationRemarkEmitter;
41 class StringRef;
42 class TargetLibraryInfo;
43 class Value;
44 
45  /// Determine which bits of V are known to be either zero or one and return
46  /// them in the KnownZero/KnownOne bit sets.
47  ///
48  /// This function is defined on values with integer type, values with pointer
49  /// type, and vectors of integers. In the case
50  /// where V is a vector, the known zero and known one values are the
51  /// same width as the vector element, and the bit is set only if it is true
52  /// for all of the elements in the vector.
53  void computeKnownBits(const Value *V, KnownBits &Known,
54  const DataLayout &DL, unsigned Depth = 0,
55  AssumptionCache *AC = nullptr,
56  const Instruction *CxtI = nullptr,
57  const DominatorTree *DT = nullptr,
58  OptimizationRemarkEmitter *ORE = nullptr,
59  bool UseInstrInfo = true);
60 
61  /// Returns the known bits rather than passing by reference.
62  KnownBits computeKnownBits(const Value *V, const DataLayout &DL,
63  unsigned Depth = 0, AssumptionCache *AC = nullptr,
64  const Instruction *CxtI = nullptr,
65  const DominatorTree *DT = nullptr,
66  OptimizationRemarkEmitter *ORE = nullptr,
67  bool UseInstrInfo = true);
68 
69  /// Compute known bits from the range metadata.
70  /// \p KnownZero the set of bits that are known to be zero
71  /// \p KnownOne the set of bits that are known to be one
72  void computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
73  KnownBits &Known);
74 
75  /// Return true if LHS and RHS have no common bits set.
76  bool haveNoCommonBitsSet(const Value *LHS, const Value *RHS,
77  const DataLayout &DL,
78  AssumptionCache *AC = nullptr,
79  const Instruction *CxtI = nullptr,
80  const DominatorTree *DT = nullptr,
81  bool UseInstrInfo = true);
82 
83  /// Return true if the given value is known to have exactly one bit set when
84  /// defined. For vectors return true if every element is known to be a power
85  /// of two when defined. Supports values with integer or pointer type and
86  /// vectors of integers. If 'OrZero' is set, then return true if the given
87  /// value is either a power of two or zero.
88  bool isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL,
89  bool OrZero = false, unsigned Depth = 0,
90  AssumptionCache *AC = nullptr,
91  const Instruction *CxtI = nullptr,
92  const DominatorTree *DT = nullptr,
93  bool UseInstrInfo = true);
94 
95  bool isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI);
96 
97  /// Return true if the given value is known to be non-zero when defined. For
98  /// vectors, return true if every element is known to be non-zero when
99  /// defined. For pointers, if the context instruction and dominator tree are
100  /// specified, perform context-sensitive analysis and return true if the
101  /// pointer couldn't possibly be null at the specified instruction.
102  /// Supports values with integer or pointer type and vectors of integers.
103  bool isKnownNonZero(const Value *V, const DataLayout &DL, unsigned Depth = 0,
104  AssumptionCache *AC = nullptr,
105  const Instruction *CxtI = nullptr,
106  const DominatorTree *DT = nullptr,
107  bool UseInstrInfo = true);
108 
109  /// Return true if the two given values are negation.
110  /// Currently can recoginze Value pair:
111  /// 1: <X, Y> if X = sub (0, Y) or Y = sub (0, X)
112  /// 2: <X, Y> if X = sub (A, B) and Y = sub (B, A)
113  bool isKnownNegation(const Value *X, const Value *Y, bool NeedNSW = false);
114 
115  /// Returns true if the give value is known to be non-negative.
116  bool isKnownNonNegative(const Value *V, const DataLayout &DL,
117  unsigned Depth = 0,
118  AssumptionCache *AC = nullptr,
119  const Instruction *CxtI = nullptr,
120  const DominatorTree *DT = nullptr,
121  bool UseInstrInfo = true);
122 
123  /// Returns true if the given value is known be positive (i.e. non-negative
124  /// and non-zero).
125  bool isKnownPositive(const Value *V, const DataLayout &DL, unsigned Depth = 0,
126  AssumptionCache *AC = nullptr,
127  const Instruction *CxtI = nullptr,
128  const DominatorTree *DT = nullptr,
129  bool UseInstrInfo = true);
130 
131  /// Returns true if the given value is known be negative (i.e. non-positive
132  /// and non-zero).
133  bool isKnownNegative(const Value *V, const DataLayout &DL, unsigned Depth = 0,
134  AssumptionCache *AC = nullptr,
135  const Instruction *CxtI = nullptr,
136  const DominatorTree *DT = nullptr,
137  bool UseInstrInfo = true);
138 
139  /// Return true if the given values are known to be non-equal when defined.
140  /// Supports scalar integer types only.
141  bool isKnownNonEqual(const Value *V1, const Value *V2, const DataLayout &DL,
142  AssumptionCache *AC = nullptr,
143  const Instruction *CxtI = nullptr,
144  const DominatorTree *DT = nullptr,
145  bool UseInstrInfo = true);
146 
147  /// Return true if 'V & Mask' is known to be zero. We use this predicate to
148  /// simplify operations downstream. Mask is known to be zero for bits that V
149  /// cannot have.
150  ///
151  /// This function is defined on values with integer type, values with pointer
152  /// type, and vectors of integers. In the case
153  /// where V is a vector, the mask, known zero, and known one values are the
154  /// same width as the vector element, and the bit is set only if it is true
155  /// for all of the elements in the vector.
156  bool MaskedValueIsZero(const Value *V, const APInt &Mask,
157  const DataLayout &DL,
158  unsigned Depth = 0, AssumptionCache *AC = nullptr,
159  const Instruction *CxtI = nullptr,
160  const DominatorTree *DT = nullptr,
161  bool UseInstrInfo = true);
162 
163  /// Return the number of times the sign bit of the register is replicated into
164  /// the other bits. We know that at least 1 bit is always equal to the sign
165  /// bit (itself), but other cases can give us information. For example,
166  /// immediately after an "ashr X, 2", we know that the top 3 bits are all
167  /// equal to each other, so we return 3. For vectors, return the number of
168  /// sign bits for the vector element with the mininum number of known sign
169  /// bits.
170  unsigned ComputeNumSignBits(const Value *Op, const DataLayout &DL,
171  unsigned Depth = 0, AssumptionCache *AC = nullptr,
172  const Instruction *CxtI = nullptr,
173  const DominatorTree *DT = nullptr,
174  bool UseInstrInfo = true);
175 
176  /// This function computes the integer multiple of Base that equals V. If
177  /// successful, it returns true and returns the multiple in Multiple. If
178  /// unsuccessful, it returns false. Also, if V can be simplified to an
179  /// integer, then the simplified V is returned in Val. Look through sext only
180  /// if LookThroughSExt=true.
181  bool ComputeMultiple(Value *V, unsigned Base, Value *&Multiple,
182  bool LookThroughSExt = false,
183  unsigned Depth = 0);
184 
185  /// Map a call instruction to an intrinsic ID. Libcalls which have equivalent
186  /// intrinsics are treated as-if they were intrinsics.
187  Intrinsic::ID getIntrinsicForCallSite(ImmutableCallSite ICS,
188  const TargetLibraryInfo *TLI);
189 
190  /// Return true if we can prove that the specified FP value is never equal to
191  /// -0.0.
192  bool CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI,
193  unsigned Depth = 0);
194 
195  /// Return true if we can prove that the specified FP value is either NaN or
196  /// never less than -0.0.
197  ///
198  /// NaN --> true
199  /// +0 --> true
200  /// -0 --> true
201  /// x > +0 --> true
202  /// x < -0 --> false
203  bool CannotBeOrderedLessThanZero(const Value *V, const TargetLibraryInfo *TLI);
204 
205  /// Return true if the floating-point scalar value is not a NaN or if the
206  /// floating-point vector value has no NaN elements. Return false if a value
207  /// could ever be NaN.
208  bool isKnownNeverNaN(const Value *V, const TargetLibraryInfo *TLI,
209  unsigned Depth = 0);
210 
211  /// Return true if we can prove that the specified FP value's sign bit is 0.
212  ///
213  /// NaN --> true/false (depending on the NaN's sign bit)
214  /// +0 --> true
215  /// -0 --> false
216  /// x > +0 --> true
217  /// x < -0 --> false
218  bool SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI);
219 
220  /// If the specified value can be set by repeating the same byte in memory,
221  /// return the i8 value that it is represented with. This is true for all i8
222  /// values obviously, but is also true for i32 0, i32 -1, i16 0xF0F0, double
223  /// 0.0 etc. If the value can't be handled with a repeated byte store (e.g.
224  /// i16 0x1234), return null. If the value is entirely undef and padding,
225  /// return undef.
226  Value *isBytewiseValue(Value *V);
227 
228  /// Given an aggregrate and an sequence of indices, see if the scalar value
229  /// indexed is already around as a register, for example if it were inserted
230  /// directly into the aggregrate.
231  ///
232  /// If InsertBefore is not null, this function will duplicate (modified)
233  /// insertvalues when a part of a nested struct is extracted.
234  Value *FindInsertedValue(Value *V,
235  ArrayRef<unsigned> idx_range,
236  Instruction *InsertBefore = nullptr);
237 
238  /// Analyze the specified pointer to see if it can be expressed as a base
239  /// pointer plus a constant offset. Return the base and offset to the caller.
240  Value *GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
241  const DataLayout &DL);
242  inline const Value *GetPointerBaseWithConstantOffset(const Value *Ptr,
243  int64_t &Offset,
244  const DataLayout &DL) {
245  return GetPointerBaseWithConstantOffset(const_cast<Value *>(Ptr), Offset,
246  DL);
247  }
248 
249  /// Returns true if the GEP is based on a pointer to a string (array of
250  // \p CharSize integers) and is indexing into this string.
252  unsigned CharSize = 8);
253 
254  /// Represents offset+length into a ConstantDataArray.
256  /// ConstantDataArray pointer. nullptr indicates a zeroinitializer (a valid
257  /// initializer, it just doesn't fit the ConstantDataArray interface).
259 
260  /// Slice starts at this Offset.
261  uint64_t Offset;
262 
263  /// Length of the slice.
264  uint64_t Length;
265 
266  /// Moves the Offset and adjusts Length accordingly.
267  void move(uint64_t Delta) {
268  assert(Delta < Length);
269  Offset += Delta;
270  Length -= Delta;
271  }
272 
273  /// Convenience accessor for elements in the slice.
274  uint64_t operator[](unsigned I) const {
275  return Array==nullptr ? 0 : Array->getElementAsInteger(I + Offset);
276  }
277  };
278 
279  /// Returns true if the value \p V is a pointer into a ConstantDataArray.
280  /// If successful \p Slice will point to a ConstantDataArray info object
281  /// with an appropriate offset.
283  unsigned ElementSize, uint64_t Offset = 0);
284 
285  /// This function computes the length of a null-terminated C string pointed to
286  /// by V. If successful, it returns true and returns the string in Str. If
287  /// unsuccessful, it returns false. This does not include the trailing null
288  /// character by default. If TrimAtNul is set to false, then this returns any
289  /// trailing null characters as well as any other characters that come after
290  /// it.
291  bool getConstantStringInfo(const Value *V, StringRef &Str,
292  uint64_t Offset = 0, bool TrimAtNul = true);
293 
294  /// If we can compute the length of the string pointed to by the specified
295  /// pointer, return 'len+1'. If we can't, return 0.
296  uint64_t GetStringLength(const Value *V, unsigned CharSize = 8);
297 
298  /// This function returns call pointer argument that is considered the same by
299  /// aliasing rules. You CAN'T use it to replace one value with another.
302  return const_cast<Value *>(
304  }
305 
306  // {launder,strip}.invariant.group returns pointer that aliases its argument,
307  // and it only captures pointer by returning it.
308  // These intrinsics are not marked as nocapture, because returning is
309  // considered as capture. The arguments are not marked as returned neither,
310  // because it would make it useless.
312  ImmutableCallSite CS);
313 
314  /// This method strips off any GEP address adjustments and pointer casts from
315  /// the specified value, returning the original object being addressed. Note
316  /// that the returned value has pointer type if the specified value does. If
317  /// the MaxLookup value is non-zero, it limits the number of instructions to
318  /// be stripped off.
319  Value *GetUnderlyingObject(Value *V, const DataLayout &DL,
320  unsigned MaxLookup = 6);
321  inline const Value *GetUnderlyingObject(const Value *V, const DataLayout &DL,
322  unsigned MaxLookup = 6) {
323  return GetUnderlyingObject(const_cast<Value *>(V), DL, MaxLookup);
324  }
325 
326  /// This method is similar to GetUnderlyingObject except that it can
327  /// look through phi and select instructions and return multiple objects.
328  ///
329  /// If LoopInfo is passed, loop phis are further analyzed. If a pointer
330  /// accesses different objects in each iteration, we don't look through the
331  /// phi node. E.g. consider this loop nest:
332  ///
333  /// int **A;
334  /// for (i)
335  /// for (j) {
336  /// A[i][j] = A[i-1][j] * B[j]
337  /// }
338  ///
339  /// This is transformed by Load-PRE to stash away A[i] for the next iteration
340  /// of the outer loop:
341  ///
342  /// Curr = A[0]; // Prev_0
343  /// for (i: 1..N) {
344  /// Prev = Curr; // Prev = PHI (Prev_0, Curr)
345  /// Curr = A[i];
346  /// for (j: 0..N) {
347  /// Curr[j] = Prev[j] * B[j]
348  /// }
349  /// }
350  ///
351  /// Since A[i] and A[i-1] are independent pointers, getUnderlyingObjects
352  /// should not assume that Curr and Prev share the same underlying object thus
353  /// it shouldn't look through the phi above.
355  const DataLayout &DL, LoopInfo *LI = nullptr,
356  unsigned MaxLookup = 6);
357 
358  /// This is a wrapper around GetUnderlyingObjects and adds support for basic
359  /// ptrtoint+arithmetic+inttoptr sequences.
361  SmallVectorImpl<Value *> &Objects,
362  const DataLayout &DL);
363 
364  /// Return true if the only users of this pointer are lifetime markers.
365  bool onlyUsedByLifetimeMarkers(const Value *V);
366 
367  /// Return true if the instruction does not have any effects besides
368  /// calculating the result and does not have undefined behavior.
369  ///
370  /// This method never returns true for an instruction that returns true for
371  /// mayHaveSideEffects; however, this method also does some other checks in
372  /// addition. It checks for undefined behavior, like dividing by zero or
373  /// loading from an invalid pointer (but not for undefined results, like a
374  /// shift with a shift amount larger than the width of the result). It checks
375  /// for malloc and alloca because speculatively executing them might cause a
376  /// memory leak. It also returns false for instructions related to control
377  /// flow, specifically terminators and PHI nodes.
378  ///
379  /// If the CtxI is specified this method performs context-sensitive analysis
380  /// and returns true if it is safe to execute the instruction immediately
381  /// before the CtxI.
382  ///
383  /// If the CtxI is NOT specified this method only looks at the instruction
384  /// itself and its operands, so if this method returns true, it is safe to
385  /// move the instruction as long as the correct dominance relationships for
386  /// the operands and users hold.
387  ///
388  /// This method can return true for instructions that read memory;
389  /// for such instructions, moving them may change the resulting value.
390  bool isSafeToSpeculativelyExecute(const Value *V,
391  const Instruction *CtxI = nullptr,
392  const DominatorTree *DT = nullptr);
393 
394  /// Returns true if the result or effects of the given instructions \p I
395  /// depend on or influence global memory.
396  /// Memory dependence arises for example if the instruction reads from
397  /// memory or may produce effects or undefined behaviour. Memory dependent
398  /// instructions generally cannot be reorderd with respect to other memory
399  /// dependent instructions or moved into non-dominated basic blocks.
400  /// Instructions which just compute a value based on the values of their
401  /// operands are not memory dependent.
402  bool mayBeMemoryDependent(const Instruction &I);
403 
404  /// Return true if it is an intrinsic that cannot be speculated but also
405  /// cannot trap.
406  bool isAssumeLikeIntrinsic(const Instruction *I);
407 
408  /// Return true if it is valid to use the assumptions provided by an
409  /// assume intrinsic, I, at the point in the control-flow identified by the
410  /// context instruction, CxtI.
411  bool isValidAssumeForContext(const Instruction *I, const Instruction *CxtI,
412  const DominatorTree *DT = nullptr);
413 
415 
417  const Value *RHS,
418  const DataLayout &DL,
419  AssumptionCache *AC,
420  const Instruction *CxtI,
421  const DominatorTree *DT,
422  bool UseInstrInfo = true);
423  OverflowResult computeOverflowForSignedMul(const Value *LHS, const Value *RHS,
424  const DataLayout &DL,
425  AssumptionCache *AC,
426  const Instruction *CxtI,
427  const DominatorTree *DT,
428  bool UseInstrInfo = true);
430  const Value *RHS,
431  const DataLayout &DL,
432  AssumptionCache *AC,
433  const Instruction *CxtI,
434  const DominatorTree *DT,
435  bool UseInstrInfo = true);
436  OverflowResult computeOverflowForSignedAdd(const Value *LHS, const Value *RHS,
437  const DataLayout &DL,
438  AssumptionCache *AC = nullptr,
439  const Instruction *CxtI = nullptr,
440  const DominatorTree *DT = nullptr);
441  /// This version also leverages the sign bit of Add if known.
443  const DataLayout &DL,
444  AssumptionCache *AC = nullptr,
445  const Instruction *CxtI = nullptr,
446  const DominatorTree *DT = nullptr);
448  const DataLayout &DL,
449  AssumptionCache *AC,
450  const Instruction *CxtI,
451  const DominatorTree *DT);
452  OverflowResult computeOverflowForSignedSub(const Value *LHS, const Value *RHS,
453  const DataLayout &DL,
454  AssumptionCache *AC,
455  const Instruction *CxtI,
456  const DominatorTree *DT);
457 
458  /// Returns true if the arithmetic part of the \p II 's result is
459  /// used only along the paths control dependent on the computation
460  /// not overflowing, \p II being an <op>.with.overflow intrinsic.
462  const DominatorTree &DT);
463 
464  /// Return true if this function can prove that the instruction I will
465  /// always transfer execution to one of its successors (including the next
466  /// instruction that follows within a basic block). E.g. this is not
467  /// guaranteed for function calls that could loop infinitely.
468  ///
469  /// In other words, this function returns false for instructions that may
470  /// transfer execution or fail to transfer execution in a way that is not
471  /// captured in the CFG nor in the sequence of instructions within a basic
472  /// block.
473  ///
474  /// Undefined behavior is assumed not to happen, so e.g. division is
475  /// guaranteed to transfer execution to the following instruction even
476  /// though division by zero might cause undefined behavior.
478 
479  /// Returns true if this block does not contain a potential implicit exit.
480  /// This is equivelent to saying that all instructions within the basic block
481  /// are guaranteed to transfer execution to their successor within the basic
482  /// block. This has the same assumptions w.r.t. undefined behavior as the
483  /// instruction variant of this function.
485 
486  /// Return true if this function can prove that the instruction I
487  /// is executed for every iteration of the loop L.
488  ///
489  /// Note that this currently only considers the loop header.
491  const Loop *L);
492 
493  /// Return true if this function can prove that I is guaranteed to yield
494  /// full-poison (all bits poison) if at least one of its operands are
495  /// full-poison (all bits poison).
496  ///
497  /// The exact rules for how poison propagates through instructions have
498  /// not been settled as of 2015-07-10, so this function is conservative
499  /// and only considers poison to be propagated in uncontroversial
500  /// cases. There is no attempt to track values that may be only partially
501  /// poison.
502  bool propagatesFullPoison(const Instruction *I);
503 
504  /// Return either nullptr or an operand of I such that I will trigger
505  /// undefined behavior if I is executed and that operand has a full-poison
506  /// value (all bits poison).
508 
509  /// Return true if this function can prove that if PoisonI is executed
510  /// and yields a full-poison value (all bits poison), then that will
511  /// trigger undefined behavior.
512  ///
513  /// Note that this currently only considers the basic block that is
514  /// the parent of I.
515  bool programUndefinedIfFullPoison(const Instruction *PoisonI);
516 
517  /// Specific patterns of select instructions we can match.
520  SPF_SMIN, /// Signed minimum
521  SPF_UMIN, /// Unsigned minimum
522  SPF_SMAX, /// Signed maximum
523  SPF_UMAX, /// Unsigned maximum
524  SPF_FMINNUM, /// Floating point minnum
525  SPF_FMAXNUM, /// Floating point maxnum
526  SPF_ABS, /// Absolute value
527  SPF_NABS /// Negated absolute value
528  };
529 
530  /// Behavior when a floating point min/max is given one NaN and one
531  /// non-NaN as input.
533  SPNB_NA = 0, /// NaN behavior not applicable.
534  SPNB_RETURNS_NAN, /// Given one NaN input, returns the NaN.
535  SPNB_RETURNS_OTHER, /// Given one NaN input, returns the non-NaN.
536  SPNB_RETURNS_ANY /// Given one NaN input, can return either (or
537  /// it has been determined that no operands can
538  /// be NaN).
539  };
540 
543  SelectPatternNaNBehavior NaNBehavior; /// Only applicable if Flavor is
544  /// SPF_FMINNUM or SPF_FMAXNUM.
545  bool Ordered; /// When implementing this min/max pattern as
546  /// fcmp; select, does the fcmp have to be
547  /// ordered?
548 
549  /// Return true if \p SPF is a min or a max pattern.
550  static bool isMinOrMax(SelectPatternFlavor SPF) {
551  return SPF != SPF_UNKNOWN && SPF != SPF_ABS && SPF != SPF_NABS;
552  }
553  };
554 
555  /// Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind
556  /// and providing the out parameter results if we successfully match.
557  ///
558  /// For ABS/NABS, LHS will be set to the input to the abs idiom. RHS will be
559  /// the negation instruction from the idiom.
560  ///
561  /// If CastOp is not nullptr, also match MIN/MAX idioms where the type does
562  /// not match that of the original select. If this is the case, the cast
563  /// operation (one of Trunc,SExt,Zext) that must be done to transform the
564  /// type of LHS and RHS into the type of V is returned in CastOp.
565  ///
566  /// For example:
567  /// %1 = icmp slt i32 %a, i32 4
568  /// %2 = sext i32 %a to i64
569  /// %3 = select i1 %1, i64 %2, i64 4
570  ///
571  /// -> LHS = %a, RHS = i32 4, *CastOp = Instruction::SExt
572  ///
574  Instruction::CastOps *CastOp = nullptr,
575  unsigned Depth = 0);
576  inline SelectPatternResult
577  matchSelectPattern(const Value *V, const Value *&LHS, const Value *&RHS,
578  Instruction::CastOps *CastOp = nullptr) {
579  Value *L = const_cast<Value*>(LHS);
580  Value *R = const_cast<Value*>(RHS);
581  auto Result = matchSelectPattern(const_cast<Value*>(V), L, R);
582  LHS = L;
583  RHS = R;
584  return Result;
585  }
586 
587  /// Return the canonical comparison predicate for the specified
588  /// minimum/maximum flavor.
590  bool Ordered = false);
591 
592  /// Return the inverse minimum/maximum flavor of the specified flavor.
593  /// For example, signed minimum is the inverse of signed maximum.
595 
596  /// Return the canonical inverse comparison predicate for the specified
597  /// minimum/maximum flavor.
599 
600  /// Return true if RHS is known to be implied true by LHS. Return false if
601  /// RHS is known to be implied false by LHS. Otherwise, return None if no
602  /// implication can be made.
603  /// A & B must be i1 (boolean) values or a vector of such values. Note that
604  /// the truth table for implication is the same as <=u on i1 values (but not
605  /// <=s!). The truth table for both is:
606  /// | T | F (B)
607  /// T | T | F
608  /// F | T | T
609  /// (A)
610  Optional<bool> isImpliedCondition(const Value *LHS, const Value *RHS,
611  const DataLayout &DL, bool LHSIsTrue = true,
612  unsigned Depth = 0);
613 } // end namespace llvm
614 
615 #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:111
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
bool isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI)
Unsigned minimum.
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
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...
A cache of @llvm.assume calls within a function.
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.
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.
const ConstantDataArray * Array
ConstantDataArray pointer.
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...
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:145
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...
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:686
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
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 isOverflowIntrinsicNoWrap(const IntrinsicInst *II, const DominatorTree &DT)
Returns true if the arithmetic part of the II &#39;s result is used only along the paths control dependen...
Predicate
This enumeration lists the possible predicates for CmpInst subclasses.
Definition: InstrTypes.h:685
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...
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:2628
uint64_t Length
Length of the slice.
SelectPatternFlavor
Specific patterns of select instructions we can match.
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.
const Value * getArgumentAliasingToReturnedPointer(ImmutableCallSite CS)
This function returns call pointer argument that is considered the same by aliasing rules...
bool mayBeMemoryDependent(const Instruction &I)
Returns true if the result or effects of the given instructions I depend on or influence global memor...
bool isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(ImmutableCallSite CS)
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:459
Establish a view to a call site for examination.
Definition: CallSite.h:714
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.
void GetUnderlyingObjects(Value *V, SmallVectorImpl< 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...
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:73
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:81
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
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)
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:44