Coverage Report

Created: 2018-09-17 19:50

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/Analysis/ScalarEvolution.h
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//===- llvm/Analysis/ScalarEvolution.h - Scalar Evolution -------*- C++ -*-===//
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//
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//                     The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// The ScalarEvolution class is an LLVM pass which can be used to analyze and
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// categorize scalar expressions in loops.  It specializes in recognizing
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// general induction variables, representing them with the abstract and opaque
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// SCEV class.  Given this analysis, trip counts of loops and other important
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// properties can be obtained.
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//
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// This analysis is primarily useful for induction variable substitution and
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// strength reduction.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_SCALAREVOLUTION_H
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#define LLVM_ANALYSIS_SCALAREVOLUTION_H
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#include "llvm/ADT/APInt.h"
25
#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/DenseMap.h"
27
#include "llvm/ADT/DenseMapInfo.h"
28
#include "llvm/ADT/FoldingSet.h"
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#include "llvm/ADT/Hashing.h"
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/PointerIntPair.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/IR/ConstantRange.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/InstrTypes.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Operator.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/IR/ValueMap.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Allocator.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/Compiler.h"
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#include <algorithm>
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#include <cassert>
50
#include <cstdint>
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#include <memory>
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#include <utility>
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54
namespace llvm {
55
56
class AssumptionCache;
57
class BasicBlock;
58
class Constant;
59
class ConstantInt;
60
class DataLayout;
61
class DominatorTree;
62
class GEPOperator;
63
class Instruction;
64
class LLVMContext;
65
class raw_ostream;
66
class ScalarEvolution;
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class SCEVAddRecExpr;
68
class SCEVUnknown;
69
class StructType;
70
class TargetLibraryInfo;
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class Type;
72
class Value;
73
74
/// This class represents an analyzed expression in the program.  These are
75
/// opaque objects that the client is not allowed to do much with directly.
76
///
77
class SCEV : public FoldingSetNode {
78
  friend struct FoldingSetTrait<SCEV>;
79
80
  /// A reference to an Interned FoldingSetNodeID for this node.  The
81
  /// ScalarEvolution's BumpPtrAllocator holds the data.
82
  FoldingSetNodeIDRef FastID;
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84
  // The SCEV baseclass this node corresponds to
85
  const unsigned short SCEVType;
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87
protected:
88
  /// This field is initialized to zero and may be used in subclasses to store
89
  /// miscellaneous information.
90
  unsigned short SubclassData = 0;
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92
public:
93
  /// NoWrapFlags are bitfield indices into SubclassData.
94
  ///
95
  /// Add and Mul expressions may have no-unsigned-wrap <NUW> or
96
  /// no-signed-wrap <NSW> properties, which are derived from the IR
97
  /// operator. NSW is a misnomer that we use to mean no signed overflow or
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  /// underflow.
99
  ///
100
  /// AddRec expressions may have a no-self-wraparound <NW> property if, in
101
  /// the integer domain, abs(step) * max-iteration(loop) <=
102
  /// unsigned-max(bitwidth).  This means that the recurrence will never reach
103
  /// its start value if the step is non-zero.  Computing the same value on
104
  /// each iteration is not considered wrapping, and recurrences with step = 0
105
  /// are trivially <NW>.  <NW> is independent of the sign of step and the
106
  /// value the add recurrence starts with.
107
  ///
108
  /// Note that NUW and NSW are also valid properties of a recurrence, and
109
  /// either implies NW. For convenience, NW will be set for a recurrence
110
  /// whenever either NUW or NSW are set.
111
  enum NoWrapFlags {
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    FlagAnyWrap = 0,    // No guarantee.
113
    FlagNW = (1 << 0),  // No self-wrap.
114
    FlagNUW = (1 << 1), // No unsigned wrap.
115
    FlagNSW = (1 << 2), // No signed wrap.
116
    NoWrapMask = (1 << 3) - 1
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  };
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119
  explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy)
120
26.8M
      : FastID(ID), SCEVType(SCEVTy) {}
121
  SCEV(const SCEV &) = delete;
122
  SCEV &operator=(const SCEV &) = delete;
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124
2.42G
  unsigned getSCEVType() const { return SCEVType; }
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  /// Return the LLVM type of this SCEV expression.
127
  Type *getType() const;
128
129
  /// Return true if the expression is a constant zero.
130
  bool isZero() const;
131
132
  /// Return true if the expression is a constant one.
133
  bool isOne() const;
134
135
  /// Return true if the expression is a constant all-ones value.
136
  bool isAllOnesValue() const;
137
138
  /// Return true if the specified scev is negated, but not a constant.
139
  bool isNonConstantNegative() const;
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141
  /// Print out the internal representation of this scalar to the specified
142
  /// stream.  This should really only be used for debugging purposes.
143
  void print(raw_ostream &OS) const;
144
145
  /// This method is used for debugging.
146
  void dump() const;
147
};
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// Specialize FoldingSetTrait for SCEV to avoid needing to compute
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// temporary FoldingSetNodeID values.
151
template <> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> {
152
0
  static void Profile(const SCEV &X, FoldingSetNodeID &ID) { ID = X.FastID; }
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  static bool Equals(const SCEV &X, const FoldingSetNodeID &ID, unsigned IDHash,
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214M
                     FoldingSetNodeID &TempID) {
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214M
    return ID == X.FastID;
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214M
  }
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15.6M
  static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) {
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15.6M
    return X.FastID.ComputeHash();
161
15.6M
  }
162
};
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48.2k
inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) {
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48.2k
  S.print(OS);
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48.2k
  return OS;
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48.2k
}
168
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/// An object of this class is returned by queries that could not be answered.
170
/// For example, if you ask for the number of iterations of a linked-list
171
/// traversal loop, you will get one of these.  None of the standard SCEV
172
/// operations are valid on this class, it is just a marker.
173
struct SCEVCouldNotCompute : public SCEV {
174
  SCEVCouldNotCompute();
175
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  /// Methods for support type inquiry through isa, cast, and dyn_cast:
177
  static bool classof(const SCEV *S);
178
};
179
180
/// This class represents an assumption made using SCEV expressions which can
181
/// be checked at run-time.
182
class SCEVPredicate : public FoldingSetNode {
183
  friend struct FoldingSetTrait<SCEVPredicate>;
184
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  /// A reference to an Interned FoldingSetNodeID for this node.  The
186
  /// ScalarEvolution's BumpPtrAllocator holds the data.
187
  FoldingSetNodeIDRef FastID;
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189
public:
190
  enum SCEVPredicateKind { P_Union, P_Equal, P_Wrap };
191
192
protected:
193
  SCEVPredicateKind Kind;
194
  ~SCEVPredicate() = default;
195
164k
  SCEVPredicate(const SCEVPredicate &) = default;
196
2.64k
  SCEVPredicate &operator=(const SCEVPredicate &) = default;
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198
public:
199
  SCEVPredicate(const FoldingSetNodeIDRef ID, SCEVPredicateKind Kind);
200
201
307k
  SCEVPredicateKind getKind() const { return Kind; }
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203
  /// Returns the estimated complexity of this predicate.  This is roughly
204
  /// measured in the number of run-time checks required.
205
0
  virtual unsigned getComplexity() const { return 1; }
206
207
  /// Returns true if the predicate is always true. This means that no
208
  /// assumptions were made and nothing needs to be checked at run-time.
209
  virtual bool isAlwaysTrue() const = 0;
210
211
  /// Returns true if this predicate implies \p N.
212
  virtual bool implies(const SCEVPredicate *N) const = 0;
213
214
  /// Prints a textual representation of this predicate with an indentation of
215
  /// \p Depth.
216
  virtual void print(raw_ostream &OS, unsigned Depth = 0) const = 0;
217
218
  /// Returns the SCEV to which this predicate applies, or nullptr if this is
219
  /// a SCEVUnionPredicate.
220
  virtual const SCEV *getExpr() const = 0;
221
};
222
223
0
inline raw_ostream &operator<<(raw_ostream &OS, const SCEVPredicate &P) {
224
0
  P.print(OS);
225
0
  return OS;
226
0
}
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228
// Specialize FoldingSetTrait for SCEVPredicate to avoid needing to compute
229
// temporary FoldingSetNodeID values.
230
template <>
231
struct FoldingSetTrait<SCEVPredicate> : DefaultFoldingSetTrait<SCEVPredicate> {
232
0
  static void Profile(const SCEVPredicate &X, FoldingSetNodeID &ID) {
233
0
    ID = X.FastID;
234
0
  }
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  static bool Equals(const SCEVPredicate &X, const FoldingSetNodeID &ID,
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28.5k
                     unsigned IDHash, FoldingSetNodeID &TempID) {
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28.5k
    return ID == X.FastID;
239
28.5k
  }
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241
  static unsigned ComputeHash(const SCEVPredicate &X,
242
13.8k
                              FoldingSetNodeID &TempID) {
243
13.8k
    return X.FastID.ComputeHash();
244
13.8k
  }
245
};
246
247
/// This class represents an assumption that two SCEV expressions are equal,
248
/// and this can be checked at run-time.
249
class SCEVEqualPredicate final : public SCEVPredicate {
250
  /// We assume that LHS == RHS.
251
  const SCEV *LHS;
252
  const SCEV *RHS;
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public:
255
  SCEVEqualPredicate(const FoldingSetNodeIDRef ID, const SCEV *LHS,
256
                     const SCEV *RHS);
257
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  /// Implementation of the SCEVPredicate interface
259
  bool implies(const SCEVPredicate *N) const override;
260
  void print(raw_ostream &OS, unsigned Depth = 0) const override;
261
  bool isAlwaysTrue() const override;
262
  const SCEV *getExpr() const override;
263
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  /// Returns the left hand side of the equality.
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1.81k
  const SCEV *getLHS() const { return LHS; }
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  /// Returns the right hand side of the equality.
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1.81k
  const SCEV *getRHS() const { return RHS; }
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  /// Methods for support type inquiry through isa, cast, and dyn_cast:
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8.17k
  static bool classof(const SCEVPredicate *P) {
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8.17k
    return P->getKind() == P_Equal;
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8.17k
  }
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};
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/// This class represents an assumption made on an AddRec expression. Given an
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/// affine AddRec expression {a,+,b}, we assume that it has the nssw or nusw
278
/// flags (defined below) in the first X iterations of the loop, where X is a
279
/// SCEV expression returned by getPredicatedBackedgeTakenCount).
280
///
281
/// Note that this does not imply that X is equal to the backedge taken
282
/// count. This means that if we have a nusw predicate for i32 {0,+,1} with a
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/// predicated backedge taken count of X, we only guarantee that {0,+,1} has
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/// nusw in the first X iterations. {0,+,1} may still wrap in the loop if we
285
/// have more than X iterations.
286
class SCEVWrapPredicate final : public SCEVPredicate {
287
public:
288
  /// Similar to SCEV::NoWrapFlags, but with slightly different semantics
289
  /// for FlagNUSW. The increment is considered to be signed, and a + b
290
  /// (where b is the increment) is considered to wrap if:
291
  ///    zext(a + b) != zext(a) + sext(b)
292
  ///
293
  /// If Signed is a function that takes an n-bit tuple and maps to the
294
  /// integer domain as the tuples value interpreted as twos complement,
295
  /// and Unsigned a function that takes an n-bit tuple and maps to the
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  /// integer domain as as the base two value of input tuple, then a + b
297
  /// has IncrementNUSW iff:
298
  ///
299
  /// 0 <= Unsigned(a) + Signed(b) < 2^n
300
  ///
301
  /// The IncrementNSSW flag has identical semantics with SCEV::FlagNSW.
302
  ///
303
  /// Note that the IncrementNUSW flag is not commutative: if base + inc
304
  /// has IncrementNUSW, then inc + base doesn't neccessarily have this
305
  /// property. The reason for this is that this is used for sign/zero
306
  /// extending affine AddRec SCEV expressions when a SCEVWrapPredicate is
307
  /// assumed. A {base,+,inc} expression is already non-commutative with
308
  /// regards to base and inc, since it is interpreted as:
309
  ///     (((base + inc) + inc) + inc) ...
310
  enum IncrementWrapFlags {
311
    IncrementAnyWrap = 0,     // No guarantee.
312
    IncrementNUSW = (1 << 0), // No unsigned with signed increment wrap.
313
    IncrementNSSW = (1 << 1), // No signed with signed increment wrap
314
                              // (equivalent with SCEV::NSW)
315
    IncrementNoWrapMask = (1 << 2) - 1
316
  };
317
318
  /// Convenient IncrementWrapFlags manipulation methods.
319
  LLVM_NODISCARD static SCEVWrapPredicate::IncrementWrapFlags
320
  clearFlags(SCEVWrapPredicate::IncrementWrapFlags Flags,
321
394k
             SCEVWrapPredicate::IncrementWrapFlags OffFlags) {
322
394k
    assert((Flags & IncrementNoWrapMask) == Flags && "Invalid flags value!");
323
394k
    assert((OffFlags & IncrementNoWrapMask) == OffFlags &&
324
394k
           "Invalid flags value!");
325
394k
    return (SCEVWrapPredicate::IncrementWrapFlags)(Flags & ~OffFlags);
326
394k
  }
327
328
  LLVM_NODISCARD static SCEVWrapPredicate::IncrementWrapFlags
329
0
  maskFlags(SCEVWrapPredicate::IncrementWrapFlags Flags, int Mask) {
330
0
    assert((Flags & IncrementNoWrapMask) == Flags && "Invalid flags value!");
331
0
    assert((Mask & IncrementNoWrapMask) == Mask && "Invalid mask value!");
332
0
333
0
    return (SCEVWrapPredicate::IncrementWrapFlags)(Flags & Mask);
334
0
  }
335
336
  LLVM_NODISCARD static SCEVWrapPredicate::IncrementWrapFlags
337
  setFlags(SCEVWrapPredicate::IncrementWrapFlags Flags,
338
3.58k
           SCEVWrapPredicate::IncrementWrapFlags OnFlags) {
339
3.58k
    assert((Flags & IncrementNoWrapMask) == Flags && "Invalid flags value!");
340
3.58k
    assert((OnFlags & IncrementNoWrapMask) == OnFlags &&
341
3.58k
           "Invalid flags value!");
342
3.58k
343
3.58k
    return (SCEVWrapPredicate::IncrementWrapFlags)(Flags | OnFlags);
344
3.58k
  }
345
346
  /// Returns the set of SCEVWrapPredicate no wrap flags implied by a
347
  /// SCEVAddRecExpr.
348
  LLVM_NODISCARD static SCEVWrapPredicate::IncrementWrapFlags
349
  getImpliedFlags(const SCEVAddRecExpr *AR, ScalarEvolution &SE);
350
351
private:
352
  const SCEVAddRecExpr *AR;
353
  IncrementWrapFlags Flags;
354
355
public:
356
  explicit SCEVWrapPredicate(const FoldingSetNodeIDRef ID,
357
                             const SCEVAddRecExpr *AR,
358
                             IncrementWrapFlags Flags);
359
360
  /// Returns the set assumed no overflow flags.
361
794
  IncrementWrapFlags getFlags() const { return Flags; }
362
363
  /// Implementation of the SCEVPredicate interface
364
  const SCEV *getExpr() const override;
365
  bool implies(const SCEVPredicate *N) const override;
366
  void print(raw_ostream &OS, unsigned Depth = 0) const override;
367
  bool isAlwaysTrue() const override;
368
369
  /// Methods for support type inquiry through isa, cast, and dyn_cast:
370
1.37k
  static bool classof(const SCEVPredicate *P) {
371
1.37k
    return P->getKind() == P_Wrap;
372
1.37k
  }
373
};
374
375
/// This class represents a composition of other SCEV predicates, and is the
376
/// class that most clients will interact with.  This is equivalent to a
377
/// logical "AND" of all the predicates in the union.
378
///
379
/// NB! Unlike other SCEVPredicate sub-classes this class does not live in the
380
/// ScalarEvolution::Preds folding set.  This is why the \c add function is sound.
381
class SCEVUnionPredicate final : public SCEVPredicate {
382
private:
383
  using PredicateMap =
384
      DenseMap<const SCEV *, SmallVector<const SCEVPredicate *, 4>>;
385
386
  /// Vector with references to all predicates in this union.
387
  SmallVector<const SCEVPredicate *, 16> Preds;
388
389
  /// Maps SCEVs to predicates for quick look-ups.
390
  PredicateMap SCEVToPreds;
391
392
public:
393
  SCEVUnionPredicate();
394
395
16.8k
  const SmallVectorImpl<const SCEVPredicate *> &getPredicates() const {
396
16.8k
    return Preds;
397
16.8k
  }
398
399
  /// Adds a predicate to this union.
400
  void add(const SCEVPredicate *N);
401
402
  /// Returns a reference to a vector containing all predicates which apply to
403
  /// \p Expr.
404
  ArrayRef<const SCEVPredicate *> getPredicatesForExpr(const SCEV *Expr);
405
406
  /// Implementation of the SCEVPredicate interface
407
  bool isAlwaysTrue() const override;
408
  bool implies(const SCEVPredicate *N) const override;
409
  void print(raw_ostream &OS, unsigned Depth) const override;
410
  const SCEV *getExpr() const override;
411
412
  /// We estimate the complexity of a union predicate as the size number of
413
  /// predicates in the union.
414
19.5k
  unsigned getComplexity() const override { return Preds.size(); }
415
416
  /// Methods for support type inquiry through isa, cast, and dyn_cast:
417
280k
  static bool classof(const SCEVPredicate *P) {
418
280k
    return P->getKind() == P_Union;
419
280k
  }
420
};
421
422
struct ExitLimitQuery {
423
  ExitLimitQuery(const Loop *L, BasicBlock *ExitingBlock, bool AllowPredicates)
424
      : L(L), ExitingBlock(ExitingBlock), AllowPredicates(AllowPredicates) {}
425
426
  const Loop *L;
427
  BasicBlock *ExitingBlock;
428
  bool AllowPredicates;
429
};
430
431
template <> struct DenseMapInfo<ExitLimitQuery> {
432
  static inline ExitLimitQuery getEmptyKey() {
433
    return ExitLimitQuery(nullptr, nullptr, true);
434
  }
435
436
  static inline ExitLimitQuery getTombstoneKey() {
437
    return ExitLimitQuery(nullptr, nullptr, false);
438
  }
439
440
  static unsigned getHashValue(ExitLimitQuery Val) {
441
    return hash_combine(hash_combine(Val.L, Val.ExitingBlock),
442
                        Val.AllowPredicates);
443
  }
444
445
  static bool isEqual(ExitLimitQuery LHS, ExitLimitQuery RHS) {
446
    return LHS.L == RHS.L && LHS.ExitingBlock == RHS.ExitingBlock &&
447
           LHS.AllowPredicates == RHS.AllowPredicates;
448
  }
449
};
450
451
/// The main scalar evolution driver. Because client code (intentionally)
452
/// can't do much with the SCEV objects directly, they must ask this class
453
/// for services.
454
class ScalarEvolution {
455
public:
456
  /// An enum describing the relationship between a SCEV and a loop.
457
  enum LoopDisposition {
458
    LoopVariant,   ///< The SCEV is loop-variant (unknown).
459
    LoopInvariant, ///< The SCEV is loop-invariant.
460
    LoopComputable ///< The SCEV varies predictably with the loop.
461
  };
462
463
  /// An enum describing the relationship between a SCEV and a basic block.
464
  enum BlockDisposition {
465
    DoesNotDominateBlock,  ///< The SCEV does not dominate the block.
466
    DominatesBlock,        ///< The SCEV dominates the block.
467
    ProperlyDominatesBlock ///< The SCEV properly dominates the block.
468
  };
469
470
  /// Convenient NoWrapFlags manipulation that hides enum casts and is
471
  /// visible in the ScalarEvolution name space.
472
  LLVM_NODISCARD static SCEV::NoWrapFlags maskFlags(SCEV::NoWrapFlags Flags,
473
186M
                                                    int Mask) {
474
186M
    return (SCEV::NoWrapFlags)(Flags & Mask);
475
186M
  }
476
  LLVM_NODISCARD static SCEV::NoWrapFlags setFlags(SCEV::NoWrapFlags Flags,
477
74.9M
                                                   SCEV::NoWrapFlags OnFlags) {
478
74.9M
    return (SCEV::NoWrapFlags)(Flags | OnFlags);
479
74.9M
  }
480
  LLVM_NODISCARD static SCEV::NoWrapFlags
481
776k
  clearFlags(SCEV::NoWrapFlags Flags, SCEV::NoWrapFlags OffFlags) {
482
776k
    return (SCEV::NoWrapFlags)(Flags & ~OffFlags);
483
776k
  }
484
485
  ScalarEvolution(Function &F, TargetLibraryInfo &TLI, AssumptionCache &AC,
486
                  DominatorTree &DT, LoopInfo &LI);
487
  ScalarEvolution(ScalarEvolution &&Arg);
488
  ~ScalarEvolution();
489
490
38.9M
  LLVMContext &getContext() const { return F.getContext(); }
491
492
  /// Test if values of the given type are analyzable within the SCEV
493
  /// framework. This primarily includes integer types, and it can optionally
494
  /// include pointer types if the ScalarEvolution class has access to
495
  /// target-specific information.
496
  bool isSCEVable(Type *Ty) const;
497
498
  /// Return the size in bits of the specified type, for which isSCEVable must
499
  /// return true.
500
  uint64_t getTypeSizeInBits(Type *Ty) const;
501
502
  /// Return a type with the same bitwidth as the given type and which
503
  /// represents how SCEV will treat the given type, for which isSCEVable must
504
  /// return true. For pointer types, this is the pointer-sized integer type.
505
  Type *getEffectiveSCEVType(Type *Ty) const;
506
507
  // Returns a wider type among {Ty1, Ty2}.
508
  Type *getWiderType(Type *Ty1, Type *Ty2) const;
509
510
  /// Return true if the SCEV is a scAddRecExpr or it contains
511
  /// scAddRecExpr. The result will be cached in HasRecMap.
512
  bool containsAddRecurrence(const SCEV *S);
513
514
  /// Erase Value from ValueExprMap and ExprValueMap.
515
  void eraseValueFromMap(Value *V);
516
517
  /// Return a SCEV expression for the full generality of the specified
518
  /// expression.
519
  const SCEV *getSCEV(Value *V);
520
521
  const SCEV *getConstant(ConstantInt *V);
522
  const SCEV *getConstant(const APInt &Val);
523
  const SCEV *getConstant(Type *Ty, uint64_t V, bool isSigned = false);
524
  const SCEV *getTruncateExpr(const SCEV *Op, Type *Ty);
525
  const SCEV *getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth = 0);
526
  const SCEV *getSignExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth = 0);
527
  const SCEV *getAnyExtendExpr(const SCEV *Op, Type *Ty);
528
  const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
529
                         SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap,
530
                         unsigned Depth = 0);
531
  const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS,
532
                         SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap,
533
26.4M
                         unsigned Depth = 0) {
534
26.4M
    SmallVector<const SCEV *, 2> Ops = {LHS, RHS};
535
26.4M
    return getAddExpr(Ops, Flags, Depth);
536
26.4M
  }
537
  const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2,
538
                         SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap,
539
0
                         unsigned Depth = 0) {
540
0
    SmallVector<const SCEV *, 3> Ops = {Op0, Op1, Op2};
541
0
    return getAddExpr(Ops, Flags, Depth);
542
0
  }
543
  const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
544
                         SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap,
545
                         unsigned Depth = 0);
546
  const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS,
547
                         SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap,
548
22.8M
                         unsigned Depth = 0) {
549
22.8M
    SmallVector<const SCEV *, 2> Ops = {LHS, RHS};
550
22.8M
    return getMulExpr(Ops, Flags, Depth);
551
22.8M
  }
552
  const SCEV *getMulExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2,
553
                         SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap,
554
9.16k
                         unsigned Depth = 0) {
555
9.16k
    SmallVector<const SCEV *, 3> Ops = {Op0, Op1, Op2};
556
9.16k
    return getMulExpr(Ops, Flags, Depth);
557
9.16k
  }
558
  const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS);
559
  const SCEV *getUDivExactExpr(const SCEV *LHS, const SCEV *RHS);
560
  const SCEV *getURemExpr(const SCEV *LHS, const SCEV *RHS);
561
  const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step, const Loop *L,
562
                            SCEV::NoWrapFlags Flags);
563
  const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
564
                            const Loop *L, SCEV::NoWrapFlags Flags);
565
  const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands,
566
111
                            const Loop *L, SCEV::NoWrapFlags Flags) {
567
111
    SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end());
568
111
    return getAddRecExpr(NewOp, L, Flags);
569
111
  }
570
571
  /// Checks if \p SymbolicPHI can be rewritten as an AddRecExpr under some
572
  /// Predicates. If successful return these <AddRecExpr, Predicates>;
573
  /// The function is intended to be called from PSCEV (the caller will decide
574
  /// whether to actually add the predicates and carry out the rewrites).
575
  Optional<std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>>>
576
  createAddRecFromPHIWithCasts(const SCEVUnknown *SymbolicPHI);
577
578
  /// Returns an expression for a GEP
579
  ///
580
  /// \p GEP The GEP. The indices contained in the GEP itself are ignored,
581
  /// instead we use IndexExprs.
582
  /// \p IndexExprs The expressions for the indices.
583
  const SCEV *getGEPExpr(GEPOperator *GEP,
584
                         const SmallVectorImpl<const SCEV *> &IndexExprs);
585
  const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS);
586
  const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
587
  const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS);
588
  const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
589
  const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS);
590
  const SCEV *getSMinExpr(SmallVectorImpl<const SCEV *> &Operands);
591
  const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS);
592
  const SCEV *getUMinExpr(SmallVectorImpl<const SCEV *> &Operands);
593
  const SCEV *getUnknown(Value *V);
594
  const SCEV *getCouldNotCompute();
595
596
  /// Return a SCEV for the constant 0 of a specific type.
597
4.42M
  const SCEV *getZero(Type *Ty) { return getConstant(Ty, 0); }
598
599
  /// Return a SCEV for the constant 1 of a specific type.
600
1.75M
  const SCEV *getOne(Type *Ty) { return getConstant(Ty, 1); }
601
602
  /// Return an expression for sizeof AllocTy that is type IntTy
603
  const SCEV *getSizeOfExpr(Type *IntTy, Type *AllocTy);
604
605
  /// Return an expression for offsetof on the given field with type IntTy
606
  const SCEV *getOffsetOfExpr(Type *IntTy, StructType *STy, unsigned FieldNo);
607
608
  /// Return the SCEV object corresponding to -V.
609
  const SCEV *getNegativeSCEV(const SCEV *V,
610
                              SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
611
612
  /// Return the SCEV object corresponding to ~V.
613
  const SCEV *getNotSCEV(const SCEV *V);
614
615
  /// Return LHS-RHS.  Minus is represented in SCEV as A+B*-1.
616
  const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
617
                           SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap,
618
                           unsigned Depth = 0);
619
620
  /// Return a SCEV corresponding to a conversion of the input value to the
621
  /// specified type.  If the type must be extended, it is zero extended.
622
  const SCEV *getTruncateOrZeroExtend(const SCEV *V, Type *Ty);
623
624
  /// Return a SCEV corresponding to a conversion of the input value to the
625
  /// specified type.  If the type must be extended, it is sign extended.
626
  const SCEV *getTruncateOrSignExtend(const SCEV *V, Type *Ty);
627
628
  /// Return a SCEV corresponding to a conversion of the input value to the
629
  /// specified type.  If the type must be extended, it is zero extended.  The
630
  /// conversion must not be narrowing.
631
  const SCEV *getNoopOrZeroExtend(const SCEV *V, Type *Ty);
632
633
  /// Return a SCEV corresponding to a conversion of the input value to the
634
  /// specified type.  If the type must be extended, it is sign extended.  The
635
  /// conversion must not be narrowing.
636
  const SCEV *getNoopOrSignExtend(const SCEV *V, Type *Ty);
637
638
  /// Return a SCEV corresponding to a conversion of the input value to the
639
  /// specified type. If the type must be extended, it is extended with
640
  /// unspecified bits. The conversion must not be narrowing.
641
  const SCEV *getNoopOrAnyExtend(const SCEV *V, Type *Ty);
642
643
  /// Return a SCEV corresponding to a conversion of the input value to the
644
  /// specified type.  The conversion must not be widening.
645
  const SCEV *getTruncateOrNoop(const SCEV *V, Type *Ty);
646
647
  /// Promote the operands to the wider of the types using zero-extension, and
648
  /// then perform a umax operation with them.
649
  const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS, const SCEV *RHS);
650
651
  /// Promote the operands to the wider of the types using zero-extension, and
652
  /// then perform a umin operation with them.
653
  const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS, const SCEV *RHS);
654
655
  /// Promote the operands to the wider of the types using zero-extension, and
656
  /// then perform a umin operation with them. N-ary function.
657
  const SCEV *getUMinFromMismatchedTypes(SmallVectorImpl<const SCEV *> &Ops);
658
659
  /// Transitively follow the chain of pointer-type operands until reaching a
660
  /// SCEV that does not have a single pointer operand. This returns a
661
  /// SCEVUnknown pointer for well-formed pointer-type expressions, but corner
662
  /// cases do exist.
663
  const SCEV *getPointerBase(const SCEV *V);
664
665
  /// Return a SCEV expression for the specified value at the specified scope
666
  /// in the program.  The L value specifies a loop nest to evaluate the
667
  /// expression at, where null is the top-level or a specified loop is
668
  /// immediately inside of the loop.
669
  ///
670
  /// This method can be used to compute the exit value for a variable defined
671
  /// in a loop by querying what the value will hold in the parent loop.
672
  ///
673
  /// In the case that a relevant loop exit value cannot be computed, the
674
  /// original value V is returned.
675
  const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L);
676
677
  /// This is a convenience function which does getSCEVAtScope(getSCEV(V), L).
678
  const SCEV *getSCEVAtScope(Value *V, const Loop *L);
679
680
  /// Test whether entry to the loop is protected by a conditional between LHS
681
  /// and RHS.  This is used to help avoid max expressions in loop trip
682
  /// counts, and to eliminate casts.
683
  bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
684
                                const SCEV *LHS, const SCEV *RHS);
685
686
  /// Test whether the backedge of the loop is protected by a conditional
687
  /// between LHS and RHS.  This is used to eliminate casts.
688
  bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
689
                                   const SCEV *LHS, const SCEV *RHS);
690
691
  /// Returns the maximum trip count of the loop if it is a single-exit
692
  /// loop and we can compute a small maximum for that loop.
693
  ///
694
  /// Implemented in terms of the \c getSmallConstantTripCount overload with
695
  /// the single exiting block passed to it. See that routine for details.
696
  unsigned getSmallConstantTripCount(const Loop *L);
697
698
  /// Returns the maximum trip count of this loop as a normal unsigned
699
  /// value. Returns 0 if the trip count is unknown or not constant. This
700
  /// "trip count" assumes that control exits via ExitingBlock. More
701
  /// precisely, it is the number of times that control may reach ExitingBlock
702
  /// before taking the branch. For loops with multiple exits, it may not be
703
  /// the number times that the loop header executes if the loop exits
704
  /// prematurely via another branch.
705
  unsigned getSmallConstantTripCount(const Loop *L, BasicBlock *ExitingBlock);
706
707
  /// Returns the upper bound of the loop trip count as a normal unsigned
708
  /// value.
709
  /// Returns 0 if the trip count is unknown or not constant.
710
  unsigned getSmallConstantMaxTripCount(const Loop *L);
711
712
  /// Returns the largest constant divisor of the trip count of the
713
  /// loop if it is a single-exit loop and we can compute a small maximum for
714
  /// that loop.
715
  ///
716
  /// Implemented in terms of the \c getSmallConstantTripMultiple overload with
717
  /// the single exiting block passed to it. See that routine for details.
718
  unsigned getSmallConstantTripMultiple(const Loop *L);
719
720
  /// Returns the largest constant divisor of the trip count of this loop as a
721
  /// normal unsigned value, if possible. This means that the actual trip
722
  /// count is always a multiple of the returned value (don't forget the trip
723
  /// count could very well be zero as well!). As explained in the comments
724
  /// for getSmallConstantTripCount, this assumes that control exits the loop
725
  /// via ExitingBlock.
726
  unsigned getSmallConstantTripMultiple(const Loop *L,
727
                                        BasicBlock *ExitingBlock);
728
729
  /// Get the expression for the number of loop iterations for which this loop
730
  /// is guaranteed not to exit via ExitingBlock. Otherwise return
731
  /// SCEVCouldNotCompute.
732
  const SCEV *getExitCount(const Loop *L, BasicBlock *ExitingBlock);
733
734
  /// If the specified loop has a predictable backedge-taken count, return it,
735
  /// otherwise return a SCEVCouldNotCompute object. The backedge-taken count is
736
  /// the number of times the loop header will be branched to from within the
737
  /// loop, assuming there are no abnormal exists like exception throws. This is
738
  /// one less than the trip count of the loop, since it doesn't count the first
739
  /// iteration, when the header is branched to from outside the loop.
740
  ///
741
  /// Note that it is not valid to call this method on a loop without a
742
  /// loop-invariant backedge-taken count (see
743
  /// hasLoopInvariantBackedgeTakenCount).
744
  const SCEV *getBackedgeTakenCount(const Loop *L);
745
746
  /// Similar to getBackedgeTakenCount, except it will add a set of
747
  /// SCEV predicates to Predicates that are required to be true in order for
748
  /// the answer to be correct. Predicates can be checked with run-time
749
  /// checks and can be used to perform loop versioning.
750
  const SCEV *getPredicatedBackedgeTakenCount(const Loop *L,
751
                                              SCEVUnionPredicate &Predicates);
752
753
  /// When successful, this returns a SCEVConstant that is greater than or equal
754
  /// to (i.e. a "conservative over-approximation") of the value returend by
755
  /// getBackedgeTakenCount.  If such a value cannot be computed, it returns the
756
  /// SCEVCouldNotCompute object.
757
  const SCEV *getMaxBackedgeTakenCount(const Loop *L);
758
759
  /// Return true if the backedge taken count is either the value returned by
760
  /// getMaxBackedgeTakenCount or zero.
761
  bool isBackedgeTakenCountMaxOrZero(const Loop *L);
762
763
  /// Return true if the specified loop has an analyzable loop-invariant
764
  /// backedge-taken count.
765
  bool hasLoopInvariantBackedgeTakenCount(const Loop *L);
766
767
  /// This method should be called by the client when it has changed a loop in
768
  /// a way that may effect ScalarEvolution's ability to compute a trip count,
769
  /// or if the loop is deleted.  This call is potentially expensive for large
770
  /// loop bodies.
771
  void forgetLoop(const Loop *L);
772
773
  // This method invokes forgetLoop for the outermost loop of the given loop
774
  // \p L, making ScalarEvolution forget about all this subtree. This needs to
775
  // be done whenever we make a transform that may affect the parameters of the
776
  // outer loop, such as exit counts for branches.
777
  void forgetTopmostLoop(const Loop *L);
778
779
  /// This method should be called by the client when it has changed a value
780
  /// in a way that may effect its value, or which may disconnect it from a
781
  /// def-use chain linking it to a loop.
782
  void forgetValue(Value *V);
783
784
  /// Called when the client has changed the disposition of values in
785
  /// this loop.
786
  ///
787
  /// We don't have a way to invalidate per-loop dispositions. Clear and
788
  /// recompute is simpler.
789
49.1k
  void forgetLoopDispositions(const Loop *L) { LoopDispositions.clear(); }
790
791
  /// Determine the minimum number of zero bits that S is guaranteed to end in
792
  /// (at every loop iteration).  It is, at the same time, the minimum number
793
  /// of times S is divisible by 2.  For example, given {4,+,8} it returns 2.
794
  /// If S is guaranteed to be 0, it returns the bitwidth of S.
795
  uint32_t GetMinTrailingZeros(const SCEV *S);
796
797
  /// Determine the unsigned range for a particular SCEV.
798
  /// NOTE: This returns a copy of the reference returned by getRangeRef.
799
66.8M
  ConstantRange getUnsignedRange(const SCEV *S) {
800
66.8M
    return getRangeRef(S, HINT_RANGE_UNSIGNED);
801
66.8M
  }
802
803
  /// Determine the min of the unsigned range for a particular SCEV.
804
492k
  APInt getUnsignedRangeMin(const SCEV *S) {
805
492k
    return getRangeRef(S, HINT_RANGE_UNSIGNED).getUnsignedMin();
806
492k
  }
807
808
  /// Determine the max of the unsigned range for a particular SCEV.
809
11.8M
  APInt getUnsignedRangeMax(const SCEV *S) {
810
11.8M
    return getRangeRef(S, HINT_RANGE_UNSIGNED).getUnsignedMax();
811
11.8M
  }
812
813
  /// Determine the signed range for a particular SCEV.
814
  /// NOTE: This returns a copy of the reference returned by getRangeRef.
815
73.0M
  ConstantRange getSignedRange(const SCEV *S) {
816
73.0M
    return getRangeRef(S, HINT_RANGE_SIGNED);
817
73.0M
  }
818
819
  /// Determine the min of the signed range for a particular SCEV.
820
31.1M
  APInt getSignedRangeMin(const SCEV *S) {
821
31.1M
    return getRangeRef(S, HINT_RANGE_SIGNED).getSignedMin();
822
31.1M
  }
823
824
  /// Determine the max of the signed range for a particular SCEV.
825
6.84M
  APInt getSignedRangeMax(const SCEV *S) {
826
6.84M
    return getRangeRef(S, HINT_RANGE_SIGNED).getSignedMax();
827
6.84M
  }
828
829
  /// Test if the given expression is known to be negative.
830
  bool isKnownNegative(const SCEV *S);
831
832
  /// Test if the given expression is known to be positive.
833
  bool isKnownPositive(const SCEV *S);
834
835
  /// Test if the given expression is known to be non-negative.
836
  bool isKnownNonNegative(const SCEV *S);
837
838
  /// Test if the given expression is known to be non-positive.
839
  bool isKnownNonPositive(const SCEV *S);
840
841
  /// Test if the given expression is known to be non-zero.
842
  bool isKnownNonZero(const SCEV *S);
843
844
  /// Splits SCEV expression \p S into two SCEVs. One of them is obtained from
845
  /// \p S by substitution of all AddRec sub-expression related to loop \p L
846
  /// with initial value of that SCEV. The second is obtained from \p S by
847
  /// substitution of all AddRec sub-expressions related to loop \p L with post
848
  /// increment of this AddRec in the loop \p L. In both cases all other AddRec
849
  /// sub-expressions (not related to \p L) remain the same.
850
  /// If the \p S contains non-invariant unknown SCEV the function returns
851
  /// CouldNotCompute SCEV in both values of std::pair.
852
  /// For example, for SCEV S={0, +, 1}<L1> + {0, +, 1}<L2> and loop L=L1
853
  /// the function returns pair:
854
  /// first = {0, +, 1}<L2>
855
  /// second = {1, +, 1}<L1> + {0, +, 1}<L2>
856
  /// We can see that for the first AddRec sub-expression it was replaced with
857
  /// 0 (initial value) for the first element and to {1, +, 1}<L1> (post
858
  /// increment value) for the second one. In both cases AddRec expression
859
  /// related to L2 remains the same.
860
  std::pair<const SCEV *, const SCEV *> SplitIntoInitAndPostInc(const Loop *L,
861
                                                                const SCEV *S);
862
863
  /// We'd like to check the predicate on every iteration of the most dominated
864
  /// loop between loops used in LHS and RHS.
865
  /// To do this we use the following list of steps:
866
  /// 1. Collect set S all loops on which either LHS or RHS depend.
867
  /// 2. If S is non-empty
868
  /// a. Let PD be the element of S which is dominated by all other elements.
869
  /// b. Let E(LHS) be value of LHS on entry of PD.
870
  ///    To get E(LHS), we should just take LHS and replace all AddRecs that are
871
  ///    attached to PD on with their entry values.
872
  ///    Define E(RHS) in the same way.
873
  /// c. Let B(LHS) be value of L on backedge of PD.
874
  ///    To get B(LHS), we should just take LHS and replace all AddRecs that are
875
  ///    attached to PD on with their backedge values.
876
  ///    Define B(RHS) in the same way.
877
  /// d. Note that E(LHS) and E(RHS) are automatically available on entry of PD,
878
  ///    so we can assert on that.
879
  /// e. Return true if isLoopEntryGuardedByCond(Pred, E(LHS), E(RHS)) &&
880
  ///                   isLoopBackedgeGuardedByCond(Pred, B(LHS), B(RHS))
881
  bool isKnownViaInduction(ICmpInst::Predicate Pred, const SCEV *LHS,
882
                           const SCEV *RHS);
883
884
  /// Test if the given expression is known to satisfy the condition described
885
  /// by Pred, LHS, and RHS.
886
  bool isKnownPredicate(ICmpInst::Predicate Pred, const SCEV *LHS,
887
                        const SCEV *RHS);
888
889
  /// Test if the condition described by Pred, LHS, RHS is known to be true on
890
  /// every iteration of the loop of the recurrency LHS.
891
  bool isKnownOnEveryIteration(ICmpInst::Predicate Pred,
892
                               const SCEVAddRecExpr *LHS, const SCEV *RHS);
893
894
  /// Return true if, for all loop invariant X, the predicate "LHS `Pred` X"
895
  /// is monotonically increasing or decreasing.  In the former case set
896
  /// `Increasing` to true and in the latter case set `Increasing` to false.
897
  ///
898
  /// A predicate is said to be monotonically increasing if may go from being
899
  /// false to being true as the loop iterates, but never the other way
900
  /// around.  A predicate is said to be monotonically decreasing if may go
901
  /// from being true to being false as the loop iterates, but never the other
902
  /// way around.
903
  bool isMonotonicPredicate(const SCEVAddRecExpr *LHS, ICmpInst::Predicate Pred,
904
                            bool &Increasing);
905
906
  /// Return true if the result of the predicate LHS `Pred` RHS is loop
907
  /// invariant with respect to L.  Set InvariantPred, InvariantLHS and
908
  /// InvariantLHS so that InvariantLHS `InvariantPred` InvariantRHS is the
909
  /// loop invariant form of LHS `Pred` RHS.
910
  bool isLoopInvariantPredicate(ICmpInst::Predicate Pred, const SCEV *LHS,
911
                                const SCEV *RHS, const Loop *L,
912
                                ICmpInst::Predicate &InvariantPred,
913
                                const SCEV *&InvariantLHS,
914
                                const SCEV *&InvariantRHS);
915
916
  /// Simplify LHS and RHS in a comparison with predicate Pred. Return true
917
  /// iff any changes were made. If the operands are provably equal or
918
  /// unequal, LHS and RHS are set to the same value and Pred is set to either
919
  /// ICMP_EQ or ICMP_NE.
920
  bool SimplifyICmpOperands(ICmpInst::Predicate &Pred, const SCEV *&LHS,
921
                            const SCEV *&RHS, unsigned Depth = 0);
922
923
  /// Return the "disposition" of the given SCEV with respect to the given
924
  /// loop.
925
  LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L);
926
927
  /// Return true if the value of the given SCEV is unchanging in the
928
  /// specified loop.
929
  bool isLoopInvariant(const SCEV *S, const Loop *L);
930
931
  /// Determine if the SCEV can be evaluated at loop's entry. It is true if it
932
  /// doesn't depend on a SCEVUnknown of an instruction which is dominated by
933
  /// the header of loop L.
934
  bool isAvailableAtLoopEntry(const SCEV *S, const Loop *L);
935
936
  /// Return true if the given SCEV changes value in a known way in the
937
  /// specified loop.  This property being true implies that the value is
938
  /// variant in the loop AND that we can emit an expression to compute the
939
  /// value of the expression at any particular loop iteration.
940
  bool hasComputableLoopEvolution(const SCEV *S, const Loop *L);
941
942
  /// Return the "disposition" of the given SCEV with respect to the given
943
  /// block.
944
  BlockDisposition getBlockDisposition(const SCEV *S, const BasicBlock *BB);
945
946
  /// Return true if elements that makes up the given SCEV dominate the
947
  /// specified basic block.
948
  bool dominates(const SCEV *S, const BasicBlock *BB);
949
950
  /// Return true if elements that makes up the given SCEV properly dominate
951
  /// the specified basic block.
952
  bool properlyDominates(const SCEV *S, const BasicBlock *BB);
953
954
  /// Test whether the given SCEV has Op as a direct or indirect operand.
955
  bool hasOperand(const SCEV *S, const SCEV *Op) const;
956
957
  /// Return the size of an element read or written by Inst.
958
  const SCEV *getElementSize(Instruction *Inst);
959
960
  /// Compute the array dimensions Sizes from the set of Terms extracted from
961
  /// the memory access function of this SCEVAddRecExpr (second step of
962
  /// delinearization).
963
  void findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms,
964
                           SmallVectorImpl<const SCEV *> &Sizes,
965
                           const SCEV *ElementSize);
966
967
  void print(raw_ostream &OS) const;
968
  void verify() const;
969
  bool invalidate(Function &F, const PreservedAnalyses &PA,
970
                  FunctionAnalysisManager::Invalidator &Inv);
971
972
  /// Collect parametric terms occurring in step expressions (first step of
973
  /// delinearization).
974
  void collectParametricTerms(const SCEV *Expr,
975
                              SmallVectorImpl<const SCEV *> &Terms);
976
977
  /// Return in Subscripts the access functions for each dimension in Sizes
978
  /// (third step of delinearization).
979
  void computeAccessFunctions(const SCEV *Expr,
980
                              SmallVectorImpl<const SCEV *> &Subscripts,
981
                              SmallVectorImpl<const SCEV *> &Sizes);
982
983
  /// Split this SCEVAddRecExpr into two vectors of SCEVs representing the
984
  /// subscripts and sizes of an array access.
985
  ///
986
  /// The delinearization is a 3 step process: the first two steps compute the
987
  /// sizes of each subscript and the third step computes the access functions
988
  /// for the delinearized array:
989
  ///
990
  /// 1. Find the terms in the step functions
991
  /// 2. Compute the array size
992
  /// 3. Compute the access function: divide the SCEV by the array size
993
  ///    starting with the innermost dimensions found in step 2. The Quotient
994
  ///    is the SCEV to be divided in the next step of the recursion. The
995
  ///    Remainder is the subscript of the innermost dimension. Loop over all
996
  ///    array dimensions computed in step 2.
997
  ///
998
  /// To compute a uniform array size for several memory accesses to the same
999
  /// object, one can collect in step 1 all the step terms for all the memory
1000
  /// accesses, and compute in step 2 a unique array shape. This guarantees
1001
  /// that the array shape will be the same across all memory accesses.
1002
  ///
1003
  /// FIXME: We could derive the result of steps 1 and 2 from a description of
1004
  /// the array shape given in metadata.
1005
  ///
1006
  /// Example:
1007
  ///
1008
  /// A[][n][m]
1009
  ///
1010
  /// for i
1011
  ///   for j
1012
  ///     for k
1013
  ///       A[j+k][2i][5i] =
1014
  ///
1015
  /// The initial SCEV:
1016
  ///
1017
  /// A[{{{0,+,2*m+5}_i, +, n*m}_j, +, n*m}_k]
1018
  ///
1019
  /// 1. Find the different terms in the step functions:
1020
  /// -> [2*m, 5, n*m, n*m]
1021
  ///
1022
  /// 2. Compute the array size: sort and unique them
1023
  /// -> [n*m, 2*m, 5]
1024
  /// find the GCD of all the terms = 1
1025
  /// divide by the GCD and erase constant terms
1026
  /// -> [n*m, 2*m]
1027
  /// GCD = m
1028
  /// divide by GCD -> [n, 2]
1029
  /// remove constant terms
1030
  /// -> [n]
1031
  /// size of the array is A[unknown][n][m]
1032
  ///
1033
  /// 3. Compute the access function
1034
  /// a. Divide {{{0,+,2*m+5}_i, +, n*m}_j, +, n*m}_k by the innermost size m
1035
  /// Quotient: {{{0,+,2}_i, +, n}_j, +, n}_k
1036
  /// Remainder: {{{0,+,5}_i, +, 0}_j, +, 0}_k
1037
  /// The remainder is the subscript of the innermost array dimension: [5i].
1038
  ///
1039
  /// b. Divide Quotient: {{{0,+,2}_i, +, n}_j, +, n}_k by next outer size n
1040
  /// Quotient: {{{0,+,0}_i, +, 1}_j, +, 1}_k
1041
  /// Remainder: {{{0,+,2}_i, +, 0}_j, +, 0}_k
1042
  /// The Remainder is the subscript of the next array dimension: [2i].
1043
  ///
1044
  /// The subscript of the outermost dimension is the Quotient: [j+k].
1045
  ///
1046
  /// Overall, we have: A[][n][m], and the access function: A[j+k][2i][5i].
1047
  void delinearize(const SCEV *Expr, SmallVectorImpl<const SCEV *> &Subscripts,
1048
                   SmallVectorImpl<const SCEV *> &Sizes,
1049
                   const SCEV *ElementSize);
1050
1051
  /// Return the DataLayout associated with the module this SCEV instance is
1052
  /// operating on.
1053
116M
  const DataLayout &getDataLayout() const {
1054
116M
    return F.getParent()->getDataLayout();
1055
116M
  }
1056
1057
  const SCEVPredicate *getEqualPredicate(const SCEV *LHS, const SCEV *RHS);
1058
1059
  const SCEVPredicate *
1060
  getWrapPredicate(const SCEVAddRecExpr *AR,
1061
                   SCEVWrapPredicate::IncrementWrapFlags AddedFlags);
1062
1063
  /// Re-writes the SCEV according to the Predicates in \p A.
1064
  const SCEV *rewriteUsingPredicate(const SCEV *S, const Loop *L,
1065
                                    SCEVUnionPredicate &A);
1066
  /// Tries to convert the \p S expression to an AddRec expression,
1067
  /// adding additional predicates to \p Preds as required.
1068
  const SCEVAddRecExpr *convertSCEVToAddRecWithPredicates(
1069
      const SCEV *S, const Loop *L,
1070
      SmallPtrSetImpl<const SCEVPredicate *> &Preds);
1071
1072
private:
1073
  /// A CallbackVH to arrange for ScalarEvolution to be notified whenever a
1074
  /// Value is deleted.
1075
  class SCEVCallbackVH final : public CallbackVH {
1076
    ScalarEvolution *SE;
1077
1078
    void deleted() override;
1079
    void allUsesReplacedWith(Value *New) override;
1080
1081
  public:
1082
    SCEVCallbackVH(Value *V, ScalarEvolution *SE = nullptr);
1083
  };
1084
1085
  friend class SCEVCallbackVH;
1086
  friend class SCEVExpander;
1087
  friend class SCEVUnknown;
1088
1089
  /// The function we are analyzing.
1090
  Function &F;
1091
1092
  /// Does the module have any calls to the llvm.experimental.guard intrinsic
1093
  /// at all?  If this is false, we avoid doing work that will only help if
1094
  /// thare are guards present in the IR.
1095
  bool HasGuards;
1096
1097
  /// The target library information for the target we are targeting.
1098
  TargetLibraryInfo &TLI;
1099
1100
  /// The tracker for \@llvm.assume intrinsics in this function.
1101
  AssumptionCache &AC;
1102
1103
  /// The dominator tree.
1104
  DominatorTree &DT;
1105
1106
  /// The loop information for the function we are currently analyzing.
1107
  LoopInfo &LI;
1108
1109
  /// This SCEV is used to represent unknown trip counts and things.
1110
  std::unique_ptr<SCEVCouldNotCompute> CouldNotCompute;
1111
1112
  /// The type for HasRecMap.
1113
  using HasRecMapType = DenseMap<const SCEV *, bool>;
1114
1115
  /// This is a cache to record whether a SCEV contains any scAddRecExpr.
1116
  HasRecMapType HasRecMap;
1117
1118
  /// The type for ExprValueMap.
1119
  using ValueOffsetPair = std::pair<Value *, ConstantInt *>;
1120
  using ExprValueMapType = DenseMap<const SCEV *, SetVector<ValueOffsetPair>>;
1121
1122
  /// ExprValueMap -- This map records the original values from which
1123
  /// the SCEV expr is generated from.
1124
  ///
1125
  /// We want to represent the mapping as SCEV -> ValueOffsetPair instead
1126
  /// of SCEV -> Value:
1127
  /// Suppose we know S1 expands to V1, and
1128
  ///  S1 = S2 + C_a
1129
  ///  S3 = S2 + C_b
1130
  /// where C_a and C_b are different SCEVConstants. Then we'd like to
1131
  /// expand S3 as V1 - C_a + C_b instead of expanding S2 literally.
1132
  /// It is helpful when S2 is a complex SCEV expr.
1133
  ///
1134
  /// In order to do that, we represent ExprValueMap as a mapping from
1135
  /// SCEV to ValueOffsetPair. We will save both S1->{V1, 0} and
1136
  /// S2->{V1, C_a} into the map when we create SCEV for V1. When S3
1137
  /// is expanded, it will first expand S2 to V1 - C_a because of
1138
  /// S2->{V1, C_a} in the map, then expand S3 to V1 - C_a + C_b.
1139
  ///
1140
  /// Note: S->{V, Offset} in the ExprValueMap means S can be expanded
1141
  /// to V - Offset.
1142
  ExprValueMapType ExprValueMap;
1143
1144
  /// The type for ValueExprMap.
1145
  using ValueExprMapType =
1146
      DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *>>;
1147
1148
  /// This is a cache of the values we have analyzed so far.
1149
  ValueExprMapType ValueExprMap;
1150
1151
  /// Mark predicate values currently being processed by isImpliedCond.
1152
  SmallPtrSet<Value *, 6> PendingLoopPredicates;
1153
1154
  /// Mark SCEVUnknown Phis currently being processed by getRangeRef.
1155
  SmallPtrSet<const PHINode *, 6> PendingPhiRanges;
1156
1157
  // Mark SCEVUnknown Phis currently being processed by isImpliedViaMerge.
1158
  SmallPtrSet<const PHINode *, 6> PendingMerges;
1159
1160
  /// Set to true by isLoopBackedgeGuardedByCond when we're walking the set of
1161
  /// conditions dominating the backedge of a loop.
1162
  bool WalkingBEDominatingConds = false;
1163
1164
  /// Set to true by isKnownPredicateViaSplitting when we're trying to prove a
1165
  /// predicate by splitting it into a set of independent predicates.
1166
  bool ProvingSplitPredicate = false;
1167
1168
  /// Memoized values for the GetMinTrailingZeros
1169
  DenseMap<const SCEV *, uint32_t> MinTrailingZerosCache;
1170
1171
  /// Return the Value set from which the SCEV expr is generated.
1172
  SetVector<ValueOffsetPair> *getSCEVValues(const SCEV *S);
1173
1174
  /// Private helper method for the GetMinTrailingZeros method
1175
  uint32_t GetMinTrailingZerosImpl(const SCEV *S);
1176
1177
  /// Information about the number of loop iterations for which a loop exit's
1178
  /// branch condition evaluates to the not-taken path.  This is a temporary
1179
  /// pair of exact and max expressions that are eventually summarized in
1180
  /// ExitNotTakenInfo and BackedgeTakenInfo.
1181
  struct ExitLimit {
1182
    const SCEV *ExactNotTaken; // The exit is not taken exactly this many times
1183
    const SCEV *MaxNotTaken; // The exit is not taken at most this many times
1184
1185
    // Not taken either exactly MaxNotTaken or zero times
1186
    bool MaxOrZero = false;
1187
1188
    /// A set of predicate guards for this ExitLimit. The result is only valid
1189
    /// if all of the predicates in \c Predicates evaluate to 'true' at
1190
    /// run-time.
1191
    SmallPtrSet<const SCEVPredicate *, 4> Predicates;
1192
1193
141
    void addPredicate(const SCEVPredicate *P) {
1194
141
      assert(!isa<SCEVUnionPredicate>(P) && "Only add leaf predicates here!");
1195
141
      Predicates.insert(P);
1196
141
    }
1197
1198
    /*implicit*/ ExitLimit(const SCEV *E);
1199
1200
    ExitLimit(
1201
        const SCEV *E, const SCEV *M, bool MaxOrZero,
1202
        ArrayRef<const SmallPtrSetImpl<const SCEVPredicate *> *> PredSetList);
1203
1204
    ExitLimit(const SCEV *E, const SCEV *M, bool MaxOrZero,
1205
              const SmallPtrSetImpl<const SCEVPredicate *> &PredSet);
1206
1207
    ExitLimit(const SCEV *E, const SCEV *M, bool MaxOrZero);
1208
1209
    /// Test whether this ExitLimit contains any computed information, or
1210
    /// whether it's all SCEVCouldNotCompute values.
1211
949k
    bool hasAnyInfo() const {
1212
949k
      return !isa<SCEVCouldNotCompute>(ExactNotTaken) ||
1213
949k
             
!isa<SCEVCouldNotCompute>(MaxNotTaken)651k
;
1214
949k
    }
1215
1216
    bool hasOperand(const SCEV *S) const;
1217
1218
    /// Test whether this ExitLimit contains all information.
1219
868k
    bool hasFullInfo() const {
1220
868k
      return !isa<SCEVCouldNotCompute>(ExactNotTaken);
1221
868k
    }
1222
  };
1223
1224
  /// Information about the number of times a particular loop exit may be
1225
  /// reached before exiting the loop.
1226
  struct ExitNotTakenInfo {
1227
    PoisoningVH<BasicBlock> ExitingBlock;
1228
    const SCEV *ExactNotTaken;
1229
    std::unique_ptr<SCEVUnionPredicate> Predicate;
1230
1231
    explicit ExitNotTakenInfo(PoisoningVH<BasicBlock> ExitingBlock,
1232
                              const SCEV *ExactNotTaken,
1233
                              std::unique_ptr<SCEVUnionPredicate> Predicate)
1234
        : ExitingBlock(ExitingBlock), ExactNotTaken(ExactNotTaken),
1235
390k
          Predicate(std::move(Predicate)) {}
1236
1237
7.03M
    bool hasAlwaysTruePredicate() const {
1238
7.03M
      return !Predicate || 
Predicate->isAlwaysTrue()223
;
1239
7.03M
    }
1240
  };
1241
1242
  /// Information about the backedge-taken count of a loop. This currently
1243
  /// includes an exact count and a maximum count.
1244
  ///
1245
  class BackedgeTakenInfo {
1246
    /// A list of computable exits and their not-taken counts.  Loops almost
1247
    /// never have more than one computable exit.
1248
    SmallVector<ExitNotTakenInfo, 1> ExitNotTaken;
1249
1250
    /// The pointer part of \c MaxAndComplete is an expression indicating the
1251
    /// least maximum backedge-taken count of the loop that is known, or a
1252
    /// SCEVCouldNotCompute. This expression is only valid if the predicates
1253
    /// associated with all loop exits are true.
1254
    ///
1255
    /// The integer part of \c MaxAndComplete is a boolean indicating if \c
1256
    /// ExitNotTaken has an element for every exiting block in the loop.
1257
    PointerIntPair<const SCEV *, 1> MaxAndComplete;
1258
1259
    /// True iff the backedge is taken either exactly Max or zero times.
1260
    bool MaxOrZero = false;
1261
1262
    /// \name Helper projection functions on \c MaxAndComplete.
1263
    /// @{
1264
1.26M
    bool isComplete() const { return MaxAndComplete.getInt(); }
1265
128M
    const SCEV *getMax() const { return MaxAndComplete.getPointer(); }
1266
    /// @}
1267
1268
  public:
1269
11.4M
    BackedgeTakenInfo() : MaxAndComplete(nullptr, 0) {}
1270
12.3M
    BackedgeTakenInfo(BackedgeTakenInfo &&) = default;
1271
790k
    BackedgeTakenInfo &operator=(BackedgeTakenInfo &&) = default;
1272
1273
    using EdgeExitInfo = std::pair<BasicBlock *, ExitLimit>;
1274
1275
    /// Initialize BackedgeTakenInfo from a list of exact exit counts.
1276
    BackedgeTakenInfo(SmallVectorImpl<EdgeExitInfo> &&ExitCounts, bool Complete,
1277
                      const SCEV *MaxCount, bool MaxOrZero);
1278
1279
    /// Test whether this BackedgeTakenInfo contains any computed information,
1280
    /// or whether it's all SCEVCouldNotCompute values.
1281
719k
    bool hasAnyInfo() const {
1282
719k
      return !ExitNotTaken.empty() || 
!isa<SCEVCouldNotCompute>(getMax())330k
;
1283
719k
    }
1284
1285
    /// Test whether this BackedgeTakenInfo contains complete information.
1286
168k
    bool hasFullInfo() const { return isComplete(); }
1287
1288
    /// Return an expression indicating the exact *backedge-taken*
1289
    /// count of the loop if it is known or SCEVCouldNotCompute
1290
    /// otherwise.  If execution makes it to the backedge on every
1291
    /// iteration (i.e. there are no abnormal exists like exception
1292
    /// throws and thread exits) then this is the number of times the
1293
    /// loop header will execute minus one.
1294
    ///
1295
    /// If the SCEV predicate associated with the answer can be different
1296
    /// from AlwaysTrue, we must add a (non null) Predicates argument.
1297
    /// The SCEV predicate associated with the answer will be added to
1298
    /// Predicates. A run-time check needs to be emitted for the SCEV
1299
    /// predicate in order for the answer to be valid.
1300
    ///
1301
    /// Note that we should always know if we need to pass a predicate
1302
    /// argument or not from the way the ExitCounts vector was computed.
1303
    /// If we allowed SCEV predicates to be generated when populating this
1304
    /// vector, this information can contain them and therefore a
1305
    /// SCEVPredicate argument should be added to getExact.
1306
    const SCEV *getExact(const Loop *L, ScalarEvolution *SE,
1307
                         SCEVUnionPredicate *Predicates = nullptr) const;
1308
1309
    /// Return the number of times this loop exit may fall through to the back
1310
    /// edge, or SCEVCouldNotCompute. The loop is guaranteed not to exit via
1311
    /// this block before this number of iterations, but may exit via another
1312
    /// block.
1313
    const SCEV *getExact(BasicBlock *ExitingBlock, ScalarEvolution *SE) const;
1314
1315
    /// Get the max backedge taken count for the loop.
1316
    const SCEV *getMax(ScalarEvolution *SE) const;
1317
1318
    /// Return true if the number of times this backedge is taken is either the
1319
    /// value returned by getMax or zero.
1320
    bool isMaxOrZero(ScalarEvolution *SE) const;
1321
1322
    /// Return true if any backedge taken count expressions refer to the given
1323
    /// subexpression.
1324
    bool hasOperand(const SCEV *S, ScalarEvolution *SE) const;
1325
1326
    /// Invalidate this result and free associated memory.
1327
    void clear();
1328
  };
1329
1330
  /// Cache the backedge-taken count of the loops for this function as they
1331
  /// are computed.
1332
  DenseMap<const Loop *, BackedgeTakenInfo> BackedgeTakenCounts;
1333
1334
  /// Cache the predicated backedge-taken count of the loops for this
1335
  /// function as they are computed.
1336
  DenseMap<const Loop *, BackedgeTakenInfo> PredicatedBackedgeTakenCounts;
1337
1338
  /// This map contains entries for all of the PHI instructions that we
1339
  /// attempt to compute constant evolutions for.  This allows us to avoid
1340
  /// potentially expensive recomputation of these properties.  An instruction
1341
  /// maps to null if we are unable to compute its exit value.
1342
  DenseMap<PHINode *, Constant *> ConstantEvolutionLoopExitValue;
1343
1344
  /// This map contains entries for all the expressions that we attempt to
1345
  /// compute getSCEVAtScope information for, which can be expensive in
1346
  /// extreme cases.
1347
  DenseMap<const SCEV *, SmallVector<std::pair<const Loop *, const SCEV *>, 2>>
1348
      ValuesAtScopes;
1349
1350
  /// Memoized computeLoopDisposition results.
1351
  DenseMap<const SCEV *,
1352
           SmallVector<PointerIntPair<const Loop *, 2, LoopDisposition>, 2>>
1353
      LoopDispositions;
1354
1355
  struct LoopProperties {
1356
    /// Set to true if the loop contains no instruction that can have side
1357
    /// effects (i.e. via throwing an exception, volatile or atomic access).
1358
    bool HasNoAbnormalExits;
1359
1360
    /// Set to true if the loop contains no instruction that can abnormally exit
1361
    /// the loop (i.e. via throwing an exception, by terminating the thread
1362
    /// cleanly or by infinite looping in a called function).  Strictly
1363
    /// speaking, the last one is not leaving the loop, but is identical to
1364
    /// leaving the loop for reasoning about undefined behavior.
1365
    bool HasNoSideEffects;
1366
  };
1367
1368
  /// Cache for \c getLoopProperties.
1369
  DenseMap<const Loop *, LoopProperties> LoopPropertiesCache;
1370
1371
  /// Return a \c LoopProperties instance for \p L, creating one if necessary.
1372
  LoopProperties getLoopProperties(const Loop *L);
1373
1374
793
  bool loopHasNoSideEffects(const Loop *L) {
1375
793
    return getLoopProperties(L).HasNoSideEffects;
1376
793
  }
1377
1378
745k
  bool loopHasNoAbnormalExits(const Loop *L) {
1379
745k
    return getLoopProperties(L).HasNoAbnormalExits;
1380
745k
  }
1381
1382
  /// Compute a LoopDisposition value.
1383
  LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L);
1384
1385
  /// Memoized computeBlockDisposition results.
1386
  DenseMap<
1387
      const SCEV *,
1388
      SmallVector<PointerIntPair<const BasicBlock *, 2, BlockDisposition>, 2>>
1389
      BlockDispositions;
1390
1391
  /// Compute a BlockDisposition value.
1392
  BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB);
1393
1394
  /// Memoized results from getRange
1395
  DenseMap<const SCEV *, ConstantRange> UnsignedRanges;
1396
1397
  /// Memoized results from getRange
1398
  DenseMap<const SCEV *, ConstantRange> SignedRanges;
1399
1400
  /// Used to parameterize getRange
1401
  enum RangeSignHint { HINT_RANGE_UNSIGNED, HINT_RANGE_SIGNED };
1402
1403
  /// Set the memoized range for the given SCEV.
1404
  const ConstantRange &setRange(const SCEV *S, RangeSignHint Hint,
1405
25.7M
                                ConstantRange CR) {
1406
25.7M
    DenseMap<const SCEV *, ConstantRange> &Cache =
1407
25.7M
        Hint == HINT_RANGE_UNSIGNED ? 
UnsignedRanges11.9M
:
SignedRanges13.8M
;
1408
25.7M
1409
25.7M
    auto Pair = Cache.try_emplace(S, std::move(CR));
1410
25.7M
    if (!Pair.second)
1411
203k
      Pair.first->second = std::move(CR);
1412
25.7M
    return Pair.first->second;
1413
25.7M
  }
1414
1415
  /// Determine the range for a particular SCEV.
1416
  /// NOTE: This returns a reference to an entry in a cache. It must be
1417
  /// copied if its needed for longer.
1418
  const ConstantRange &getRangeRef(const SCEV *S, RangeSignHint Hint);
1419
1420
  /// Determines the range for the affine SCEVAddRecExpr {\p Start,+,\p Stop}.
1421
  /// Helper for \c getRange.
1422
  ConstantRange getRangeForAffineAR(const SCEV *Start, const SCEV *Stop,
1423
                                    const SCEV *MaxBECount, unsigned BitWidth);
1424
1425
  /// Try to compute a range for the affine SCEVAddRecExpr {\p Start,+,\p
1426
  /// Stop} by "factoring out" a ternary expression from the add recurrence.
1427
  /// Helper called by \c getRange.
1428
  ConstantRange getRangeViaFactoring(const SCEV *Start, const SCEV *Stop,
1429
                                     const SCEV *MaxBECount, unsigned BitWidth);
1430
1431
  /// We know that there is no SCEV for the specified value.  Analyze the
1432
  /// expression.
1433
  const SCEV *createSCEV(Value *V);
1434
1435
  /// Provide the special handling we need to analyze PHI SCEVs.
1436
  const SCEV *createNodeForPHI(PHINode *PN);
1437
1438
  /// Helper function called from createNodeForPHI.
1439
  const SCEV *createAddRecFromPHI(PHINode *PN);
1440
1441
  /// A helper function for createAddRecFromPHI to handle simple cases.
1442
  const SCEV *createSimpleAffineAddRec(PHINode *PN, Value *BEValueV,
1443
                                            Value *StartValueV);
1444
1445
  /// Helper function called from createNodeForPHI.
1446
  const SCEV *createNodeFromSelectLikePHI(PHINode *PN);
1447
1448
  /// Provide special handling for a select-like instruction (currently this
1449
  /// is either a select instruction or a phi node).  \p I is the instruction
1450
  /// being processed, and it is assumed equivalent to "Cond ? TrueVal :
1451
  /// FalseVal".
1452
  const SCEV *createNodeForSelectOrPHI(Instruction *I, Value *Cond,
1453
                                       Value *TrueVal, Value *FalseVal);
1454
1455
  /// Provide the special handling we need to analyze GEP SCEVs.
1456
  const SCEV *createNodeForGEP(GEPOperator *GEP);
1457
1458
  /// Implementation code for getSCEVAtScope; called at most once for each
1459
  /// SCEV+Loop pair.
1460
  const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L);
1461
1462
  /// This looks up computed SCEV values for all instructions that depend on
1463
  /// the given instruction and removes them from the ValueExprMap map if they
1464
  /// reference SymName. This is used during PHI resolution.
1465
  void forgetSymbolicName(Instruction *I, const SCEV *SymName);
1466
1467
  /// Return the BackedgeTakenInfo for the given loop, lazily computing new
1468
  /// values if the loop hasn't been analyzed yet. The returned result is
1469
  /// guaranteed not to be predicated.
1470
  const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L);
1471
1472
  /// Similar to getBackedgeTakenInfo, but will add predicates as required
1473
  /// with the purpose of returning complete information.
1474
  const BackedgeTakenInfo &getPredicatedBackedgeTakenInfo(const Loop *L);
1475
1476
  /// Compute the number of times the specified loop will iterate.
1477
  /// If AllowPredicates is set, we will create new SCEV predicates as
1478
  /// necessary in order to return an exact answer.
1479
  BackedgeTakenInfo computeBackedgeTakenCount(const Loop *L,
1480
                                              bool AllowPredicates = false);
1481
1482
  /// Compute the number of times the backedge of the specified loop will
1483
  /// execute if it exits via the specified block. If AllowPredicates is set,
1484
  /// this call will try to use a minimal set of SCEV predicates in order to
1485
  /// return an exact answer.
1486
  ExitLimit computeExitLimit(const Loop *L, BasicBlock *ExitingBlock,
1487
                             bool AllowPredicates = false);
1488
1489
  /// Compute the number of times the backedge of the specified loop will
1490
  /// execute if its exit condition were a conditional branch of ExitCond.
1491
  ///
1492
  /// \p ControlsExit is true if ExitCond directly controls the exit
1493
  /// branch. In this case, we can assume that the loop exits only if the
1494
  /// condition is true and can infer that failing to meet the condition prior
1495
  /// to integer wraparound results in undefined behavior.
1496
  ///
1497
  /// If \p AllowPredicates is set, this call will try to use a minimal set of
1498
  /// SCEV predicates in order to return an exact answer.
1499
  ExitLimit computeExitLimitFromCond(const Loop *L, Value *ExitCond,
1500
                                     bool ExitIfTrue, bool ControlsExit,
1501
                                     bool AllowPredicates = false);
1502
1503
  // Helper functions for computeExitLimitFromCond to avoid exponential time
1504
  // complexity.
1505
1506
  class ExitLimitCache {
1507
    // It may look like we need key on the whole (L, ExitIfTrue, ControlsExit,
1508
    // AllowPredicates) tuple, but recursive calls to
1509
    // computeExitLimitFromCondCached from computeExitLimitFromCondImpl only
1510
    // vary the in \c ExitCond and \c ControlsExit parameters.  We remember the
1511
    // initial values of the other values to assert our assumption.
1512
    SmallDenseMap<PointerIntPair<Value *, 1>, ExitLimit> TripCountMap;
1513
1514
    const Loop *L;
1515
    bool ExitIfTrue;
1516
    bool AllowPredicates;
1517
1518
  public:
1519
    ExitLimitCache(const Loop *L, bool ExitIfTrue, bool AllowPredicates)
1520
867k
        : L(L), ExitIfTrue(ExitIfTrue), AllowPredicates(AllowPredicates) {}
1521
1522
    Optional<ExitLimit> find(const Loop *L, Value *ExitCond, bool ExitIfTrue,
1523
                             bool ControlsExit, bool AllowPredicates);
1524
1525
    void insert(const Loop *L, Value *ExitCond, bool ExitIfTrue,
1526
                bool ControlsExit, bool AllowPredicates, const ExitLimit &EL);
1527
  };
1528
1529
  using ExitLimitCacheTy = ExitLimitCache;
1530
1531
  ExitLimit computeExitLimitFromCondCached(ExitLimitCacheTy &Cache,
1532
                                           const Loop *L, Value *ExitCond,
1533
                                           bool ExitIfTrue,
1534
                                           bool ControlsExit,
1535
                                           bool AllowPredicates);
1536
  ExitLimit computeExitLimitFromCondImpl(ExitLimitCacheTy &Cache, const Loop *L,
1537
                                         Value *ExitCond, bool ExitIfTrue,
1538
                                         bool ControlsExit,
1539
                                         bool AllowPredicates);
1540
1541
  /// Compute the number of times the backedge of the specified loop will
1542
  /// execute if its exit condition were a conditional branch of the ICmpInst
1543
  /// ExitCond and ExitIfTrue. If AllowPredicates is set, this call will try
1544
  /// to use a minimal set of SCEV predicates in order to return an exact
1545
  /// answer.
1546
  ExitLimit computeExitLimitFromICmp(const Loop *L, ICmpInst *ExitCond,
1547
                                     bool ExitIfTrue,
1548
                                     bool IsSubExpr,
1549
                                     bool AllowPredicates = false);
1550
1551
  /// Compute the number of times the backedge of the specified loop will
1552
  /// execute if its exit condition were a switch with a single exiting case
1553
  /// to ExitingBB.
1554
  ExitLimit computeExitLimitFromSingleExitSwitch(const Loop *L,
1555
                                                 SwitchInst *Switch,
1556
                                                 BasicBlock *ExitingBB,
1557
                                                 bool IsSubExpr);
1558
1559
  /// Given an exit condition of 'icmp op load X, cst', try to see if we can
1560
  /// compute the backedge-taken count.
1561
  ExitLimit computeLoadConstantCompareExitLimit(LoadInst *LI, Constant *RHS,
1562
                                                const Loop *L,
1563
                                                ICmpInst::Predicate p);
1564
1565
  /// Compute the exit limit of a loop that is controlled by a
1566
  /// "(IV >> 1) != 0" type comparison.  We cannot compute the exact trip
1567
  /// count in these cases (since SCEV has no way of expressing them), but we
1568
  /// can still sometimes compute an upper bound.
1569
  ///
1570
  /// Return an ExitLimit for a loop whose backedge is guarded by `LHS Pred
1571
  /// RHS`.
1572
  ExitLimit computeShiftCompareExitLimit(Value *LHS, Value *RHS, const Loop *L,
1573
                                         ICmpInst::Predicate Pred);
1574
1575
  /// If the loop is known to execute a constant number of times (the
1576
  /// condition evolves only from constants), try to evaluate a few iterations
1577
  /// of the loop until we get the exit condition gets a value of ExitWhen
1578
  /// (true or false).  If we cannot evaluate the exit count of the loop,
1579
  /// return CouldNotCompute.
1580
  const SCEV *computeExitCountExhaustively(const Loop *L, Value *Cond,
1581
                                           bool ExitWhen);
1582
1583
  /// Return the number of times an exit condition comparing the specified
1584
  /// value to zero will execute.  If not computable, return CouldNotCompute.
1585
  /// If AllowPredicates is set, this call will try to use a minimal set of
1586
  /// SCEV predicates in order to return an exact answer.
1587
  ExitLimit howFarToZero(const SCEV *V, const Loop *L, bool IsSubExpr,
1588
                         bool AllowPredicates = false);
1589
1590
  /// Return the number of times an exit condition checking the specified
1591
  /// value for nonzero will execute.  If not computable, return
1592
  /// CouldNotCompute.
1593
  ExitLimit howFarToNonZero(const SCEV *V, const Loop *L);
1594
1595
  /// Return the number of times an exit condition containing the specified
1596
  /// less-than comparison will execute.  If not computable, return
1597
  /// CouldNotCompute.
1598
  ///
1599
  /// \p isSigned specifies whether the less-than is signed.
1600
  ///
1601
  /// \p ControlsExit is true when the LHS < RHS condition directly controls
1602
  /// the branch (loops exits only if condition is true). In this case, we can
1603
  /// use NoWrapFlags to skip overflow checks.
1604
  ///
1605
  /// If \p AllowPredicates is set, this call will try to use a minimal set of
1606
  /// SCEV predicates in order to return an exact answer.
1607
  ExitLimit howManyLessThans(const SCEV *LHS, const SCEV *RHS, const Loop *L,
1608
                             bool isSigned, bool ControlsExit,
1609
                             bool AllowPredicates = false);
1610
1611
  ExitLimit howManyGreaterThans(const SCEV *LHS, const SCEV *RHS, const Loop *L,
1612
                                bool isSigned, bool IsSubExpr,
1613
                                bool AllowPredicates = false);
1614
1615
  /// Return a predecessor of BB (which may not be an immediate predecessor)
1616
  /// which has exactly one successor from which BB is reachable, or null if
1617
  /// no such block is found.
1618
  std::pair<BasicBlock *, BasicBlock *>
1619
  getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
1620
1621
  /// Test whether the condition described by Pred, LHS, and RHS is true
1622
  /// whenever the given FoundCondValue value evaluates to true.
1623
  bool isImpliedCond(ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS,
1624
                     Value *FoundCondValue, bool Inverse);
1625
1626
  /// Test whether the condition described by Pred, LHS, and RHS is true
1627
  /// whenever the condition described by FoundPred, FoundLHS, FoundRHS is
1628
  /// true.
1629
  bool isImpliedCond(ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS,
1630
                     ICmpInst::Predicate FoundPred, const SCEV *FoundLHS,
1631
                     const SCEV *FoundRHS);
1632
1633
  /// Test whether the condition described by Pred, LHS, and RHS is true
1634
  /// whenever the condition described by Pred, FoundLHS, and FoundRHS is
1635
  /// true.
1636
  bool isImpliedCondOperands(ICmpInst::Predicate Pred, const SCEV *LHS,
1637
                             const SCEV *RHS, const SCEV *FoundLHS,
1638
                             const SCEV *FoundRHS);
1639
1640
  /// Test whether the condition described by Pred, LHS, and RHS is true
1641
  /// whenever the condition described by Pred, FoundLHS, and FoundRHS is
1642
  /// true. Here LHS is an operation that includes FoundLHS as one of its
1643
  /// arguments.
1644
  bool isImpliedViaOperations(ICmpInst::Predicate Pred,
1645
                              const SCEV *LHS, const SCEV *RHS,
1646
                              const SCEV *FoundLHS, const SCEV *FoundRHS,
1647
                              unsigned Depth = 0);
1648
1649
  /// Test whether the condition described by Pred, LHS, and RHS is true.
1650
  /// Use only simple non-recursive types of checks, such as range analysis etc.
1651
  bool isKnownViaNonRecursiveReasoning(ICmpInst::Predicate Pred,
1652
                                       const SCEV *LHS, const SCEV *RHS);
1653
1654
  /// Test whether the condition described by Pred, LHS, and RHS is true
1655
  /// whenever the condition described by Pred, FoundLHS, and FoundRHS is
1656
  /// true.
1657
  bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred, const SCEV *LHS,
1658
                                   const SCEV *RHS, const SCEV *FoundLHS,
1659
                                   const SCEV *FoundRHS);
1660
1661
  /// Test whether the condition described by Pred, LHS, and RHS is true
1662
  /// whenever the condition described by Pred, FoundLHS, and FoundRHS is
1663
  /// true.  Utility function used by isImpliedCondOperands.  Tries to get
1664
  /// cases like "X `sgt` 0 => X - 1 `sgt` -1".
1665
  bool isImpliedCondOperandsViaRanges(ICmpInst::Predicate Pred, const SCEV *LHS,
1666
                                      const SCEV *RHS, const SCEV *FoundLHS,
1667
                                      const SCEV *FoundRHS);
1668
1669
  /// Return true if the condition denoted by \p LHS \p Pred \p RHS is implied
1670
  /// by a call to \c @llvm.experimental.guard in \p BB.
1671
  bool isImpliedViaGuard(BasicBlock *BB, ICmpInst::Predicate Pred,
1672
                         const SCEV *LHS, const SCEV *RHS);
1673
1674
  /// Test whether the condition described by Pred, LHS, and RHS is true
1675
  /// whenever the condition described by Pred, FoundLHS, and FoundRHS is
1676
  /// true.
1677
  ///
1678
  /// This routine tries to rule out certain kinds of integer overflow, and
1679
  /// then tries to reason about arithmetic properties of the predicates.
1680
  bool isImpliedCondOperandsViaNoOverflow(ICmpInst::Predicate Pred,
1681
                                          const SCEV *LHS, const SCEV *RHS,
1682
                                          const SCEV *FoundLHS,
1683
                                          const SCEV *FoundRHS);
1684
1685
  /// Test whether the condition described by Pred, LHS, and RHS is true
1686
  /// whenever the condition described by Pred, FoundLHS, and FoundRHS is
1687
  /// true.
1688
  ///
1689
  /// This routine tries to figure out predicate for Phis which are SCEVUnknown
1690
  /// if it is true for every possible incoming value from their respective
1691
  /// basic blocks.
1692
  bool isImpliedViaMerge(ICmpInst::Predicate Pred,
1693
                         const SCEV *LHS, const SCEV *RHS,
1694
                         const SCEV *FoundLHS, const SCEV *FoundRHS,
1695
                         unsigned Depth);
1696
1697
  /// If we know that the specified Phi is in the header of its containing
1698
  /// loop, we know the loop executes a constant number of times, and the PHI
1699
  /// node is just a recurrence involving constants, fold it.
1700
  Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt &BEs,
1701
                                              const Loop *L);
1702
1703
  /// Test if the given expression is known to satisfy the condition described
1704
  /// by Pred and the known constant ranges of LHS and RHS.
1705
  bool isKnownPredicateViaConstantRanges(ICmpInst::Predicate Pred,
1706
                                         const SCEV *LHS, const SCEV *RHS);
1707
1708
  /// Try to prove the condition described by "LHS Pred RHS" by ruling out
1709
  /// integer overflow.
1710
  ///
1711
  /// For instance, this will return true for "A s< (A + C)<nsw>" if C is
1712
  /// positive.
1713
  bool isKnownPredicateViaNoOverflow(ICmpInst::Predicate Pred, const SCEV *LHS,
1714
                                     const SCEV *RHS);
1715
1716
  /// Try to split Pred LHS RHS into logical conjunctions (and's) and try to
1717
  /// prove them individually.
1718
  bool isKnownPredicateViaSplitting(ICmpInst::Predicate Pred, const SCEV *LHS,
1719
                                    const SCEV *RHS);
1720
1721
  /// Try to match the Expr as "(L + R)<Flags>".
1722
  bool splitBinaryAdd(const SCEV *Expr, const SCEV *&L, const SCEV *&R,
1723
                      SCEV::NoWrapFlags &Flags);
1724
1725
  /// Compute \p LHS - \p RHS and returns the result as an APInt if it is a
1726
  /// constant, and None if it isn't.
1727
  ///
1728
  /// This is intended to be a cheaper version of getMinusSCEV.  We can be
1729
  /// frugal here since we just bail out of actually constructing and
1730
  /// canonicalizing an expression in the cases where the result isn't going
1731
  /// to be a constant.
1732
  Optional<APInt> computeConstantDifference(const SCEV *LHS, const SCEV *RHS);
1733
1734
  /// Drop memoized information computed for S.
1735
  void forgetMemoizedResults(const SCEV *S);
1736
1737
  /// Return an existing SCEV for V if there is one, otherwise return nullptr.
1738
  const SCEV *getExistingSCEV(Value *V);
1739
1740
  /// Return false iff given SCEV contains a SCEVUnknown with NULL value-
1741
  /// pointer.
1742
  bool checkValidity(const SCEV *S) const;
1743
1744
  /// Return true if `ExtendOpTy`({`Start`,+,`Step`}) can be proved to be
1745
  /// equal to {`ExtendOpTy`(`Start`),+,`ExtendOpTy`(`Step`)}.  This is
1746
  /// equivalent to proving no signed (resp. unsigned) wrap in
1747
  /// {`Start`,+,`Step`} if `ExtendOpTy` is `SCEVSignExtendExpr`
1748
  /// (resp. `SCEVZeroExtendExpr`).
1749
  template <typename ExtendOpTy>
1750
  bool proveNoWrapByVaryingStart(const SCEV *Start, const SCEV *Step,
1751
                                 const Loop *L);
1752
1753
  /// Try to prove NSW or NUW on \p AR relying on ConstantRange manipulation.
1754
  SCEV::NoWrapFlags proveNoWrapViaConstantRanges(const SCEVAddRecExpr *AR);
1755
1756
  bool isMonotonicPredicateImpl(const SCEVAddRecExpr *LHS,
1757
                                ICmpInst::Predicate Pred, bool &Increasing);
1758
1759
  /// Return SCEV no-wrap flags that can be proven based on reasoning about
1760
  /// how poison produced from no-wrap flags on this value (e.g. a nuw add)
1761
  /// would trigger undefined behavior on overflow.
1762
  SCEV::NoWrapFlags getNoWrapFlagsFromUB(const Value *V);
1763
1764
  /// Return true if the SCEV corresponding to \p I is never poison.  Proving
1765
  /// this is more complex than proving that just \p I is never poison, since
1766
  /// SCEV commons expressions across control flow, and you can have cases
1767
  /// like:
1768
  ///
1769
  ///   idx0 = a + b;
1770
  ///   ptr[idx0] = 100;
1771
  ///   if (<condition>) {
1772
  ///     idx1 = a +nsw b;
1773
  ///     ptr[idx1] = 200;
1774
  ///   }
1775
  ///
1776
  /// where the SCEV expression (+ a b) is guaranteed to not be poison (and
1777
  /// hence not sign-overflow) only if "<condition>" is true.  Since both
1778
  /// `idx0` and `idx1` will be mapped to the same SCEV expression, (+ a b),
1779
  /// it is not okay to annotate (+ a b) with <nsw> in the above example.
1780
  bool isSCEVExprNeverPoison(const Instruction *I);
1781
1782
  /// This is like \c isSCEVExprNeverPoison but it specifically works for
1783
  /// instructions that will get mapped to SCEV add recurrences.  Return true
1784
  /// if \p I will never generate poison under the assumption that \p I is an
1785
  /// add recurrence on the loop \p L.
1786
  bool isAddRecNeverPoison(const Instruction *I, const Loop *L);
1787
1788
  /// Similar to createAddRecFromPHI, but with the additional flexibility of
1789
  /// suggesting runtime overflow checks in case casts are encountered.
1790
  /// If successful, the analysis records that for this loop, \p SymbolicPHI,
1791
  /// which is the UnknownSCEV currently representing the PHI, can be rewritten
1792
  /// into an AddRec, assuming some predicates; The function then returns the
1793
  /// AddRec and the predicates as a pair, and caches this pair in
1794
  /// PredicatedSCEVRewrites.
1795
  /// If the analysis is not successful, a mapping from the \p SymbolicPHI to
1796
  /// itself (with no predicates) is recorded, and a nullptr with an empty
1797
  /// predicates vector is returned as a pair.
1798
  Optional<std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>>>
1799
  createAddRecFromPHIWithCastsImpl(const SCEVUnknown *SymbolicPHI);
1800
1801
  /// Compute the backedge taken count knowing the interval difference, the
1802
  /// stride and presence of the equality in the comparison.
1803
  const SCEV *computeBECount(const SCEV *Delta, const SCEV *Stride,
1804
                             bool Equality);
1805
1806
  /// Compute the maximum backedge count based on the range of values
1807
  /// permitted by Start, End, and Stride. This is for loops of the form
1808
  /// {Start, +, Stride} LT End.
1809
  ///
1810
  /// Precondition: the induction variable is known to be positive.  We *don't*
1811
  /// assert these preconditions so please be careful.
1812
  const SCEV *computeMaxBECountForLT(const SCEV *Start, const SCEV *Stride,
1813
                                     const SCEV *End, unsigned BitWidth,
1814
                                     bool IsSigned);
1815
1816
  /// Verify if an linear IV with positive stride can overflow when in a
1817
  /// less-than comparison, knowing the invariant term of the comparison,
1818
  /// the stride and the knowledge of NSW/NUW flags on the recurrence.
1819
  bool doesIVOverflowOnLT(const SCEV *RHS, const SCEV *Stride, bool IsSigned,
1820
                          bool NoWrap);
1821
1822
  /// Verify if an linear IV with negative stride can overflow when in a
1823
  /// greater-than comparison, knowing the invariant term of the comparison,
1824
  /// the stride and the knowledge of NSW/NUW flags on the recurrence.
1825
  bool doesIVOverflowOnGT(const SCEV *RHS, const SCEV *Stride, bool IsSigned,
1826
                          bool NoWrap);
1827
1828
  /// Get add expr already created or create a new one.
1829
  const SCEV *getOrCreateAddExpr(SmallVectorImpl<const SCEV *> &Ops,
1830
                                 SCEV::NoWrapFlags Flags);
1831
1832
  /// Get mul expr already created or create a new one.
1833
  const SCEV *getOrCreateMulExpr(SmallVectorImpl<const SCEV *> &Ops,
1834
                                 SCEV::NoWrapFlags Flags);
1835
1836
  /// Return x if \p Val is f(x) where f is a 1-1 function.
1837
  const SCEV *stripInjectiveFunctions(const SCEV *Val) const;
1838
1839
  /// Find all of the loops transitively used in \p S, and fill \p LoopsUsed.
1840
  /// A loop is considered "used" by an expression if it contains
1841
  /// an add rec on said loop.
1842
  void getUsedLoops(const SCEV *S, SmallPtrSetImpl<const Loop *> &LoopsUsed);
1843
1844
  /// Find all of the loops transitively used in \p S, and update \c LoopUsers
1845
  /// accordingly.
1846
  void addToLoopUseLists(const SCEV *S);
1847
1848
  /// Try to match the pattern generated by getURemExpr(A, B). If successful,
1849
  /// Assign A and B to LHS and RHS, respectively.
1850
  bool matchURem(const SCEV *Expr, const SCEV *&LHS, const SCEV *&RHS);
1851
1852
  FoldingSet<SCEV> UniqueSCEVs;
1853
  FoldingSet<SCEVPredicate> UniquePreds;
1854
  BumpPtrAllocator SCEVAllocator;
1855
1856
  /// This maps loops to a list of SCEV expressions that (transitively) use said
1857
  /// loop.
1858
  DenseMap<const Loop *, SmallVector<const SCEV *, 4>> LoopUsers;
1859
1860
  /// Cache tentative mappings from UnknownSCEVs in a Loop, to a SCEV expression
1861
  /// they can be rewritten into under certain predicates.
1862
  DenseMap<std::pair<const SCEVUnknown *, const Loop *>,
1863
           std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>>>
1864
      PredicatedSCEVRewrites;
1865
1866
  /// The head of a linked list of all SCEVUnknown values that have been
1867
  /// allocated. This is used by releaseMemory to locate them all and call
1868
  /// their destructors.
1869
  SCEVUnknown *FirstUnknown = nullptr;
1870
};
1871
1872
/// Analysis pass that exposes the \c ScalarEvolution for a function.
1873
class ScalarEvolutionAnalysis
1874
    : public AnalysisInfoMixin<ScalarEvolutionAnalysis> {
1875
  friend AnalysisInfoMixin<ScalarEvolutionAnalysis>;
1876
1877
  static AnalysisKey Key;
1878
1879
public:
1880
  using Result = ScalarEvolution;
1881
1882
  ScalarEvolution run(Function &F, FunctionAnalysisManager &AM);
1883
};
1884
1885
/// Printer pass for the \c ScalarEvolutionAnalysis results.
1886
class ScalarEvolutionPrinterPass
1887
    : public PassInfoMixin<ScalarEvolutionPrinterPass> {
1888
  raw_ostream &OS;
1889
1890
public:
1891
6
  explicit ScalarEvolutionPrinterPass(raw_ostream &OS) : OS(OS) {}
1892
1893
  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
1894
};
1895
1896
class ScalarEvolutionWrapperPass : public FunctionPass {
1897
  std::unique_ptr<ScalarEvolution> SE;
1898
1899
public:
1900
  static char ID;
1901
1902
  ScalarEvolutionWrapperPass();
1903
1904
5.28M
  ScalarEvolution &getSE() { return *SE; }
1905
0
  const ScalarEvolution &getSE() const { return *SE; }
1906
1907
  bool runOnFunction(Function &F) override;
1908
  void releaseMemory() override;
1909
  void getAnalysisUsage(AnalysisUsage &AU) const override;
1910
  void print(raw_ostream &OS, const Module * = nullptr) const override;
1911
  void verifyAnalysis() const override;
1912
};
1913
1914
/// An interface layer with SCEV used to manage how we see SCEV expressions
1915
/// for values in the context of existing predicates. We can add new
1916
/// predicates, but we cannot remove them.
1917
///
1918
/// This layer has multiple purposes:
1919
///   - provides a simple interface for SCEV versioning.
1920
///   - guarantees that the order of transformations applied on a SCEV
1921
///     expression for a single Value is consistent across two different
1922
///     getSCEV calls. This means that, for example, once we've obtained
1923
///     an AddRec expression for a certain value through expression
1924
///     rewriting, we will continue to get an AddRec expression for that
1925
///     Value.
1926
///   - lowers the number of expression rewrites.
1927
class PredicatedScalarEvolution {
1928
public:
1929
  PredicatedScalarEvolution(ScalarEvolution &SE, Loop &L);
1930
1931
  const SCEVUnionPredicate &getUnionPredicate() const;
1932
1933
  /// Returns the SCEV expression of V, in the context of the current SCEV
1934
  /// predicate.  The order of transformations applied on the expression of V
1935
  /// returned by ScalarEvolution is guaranteed to be preserved, even when
1936
  /// adding new predicates.
1937
  const SCEV *getSCEV(Value *V);
1938
1939
  /// Get the (predicated) backedge count for the analyzed loop.
1940
  const SCEV *getBackedgeTakenCount();
1941
1942
  /// Adds a new predicate.
1943
  void addPredicate(const SCEVPredicate &Pred);
1944
1945
  /// Attempts to produce an AddRecExpr for V by adding additional SCEV
1946
  /// predicates. If we can't transform the expression into an AddRecExpr we
1947
  /// return nullptr and not add additional SCEV predicates to the current
1948
  /// context.
1949
  const SCEVAddRecExpr *getAsAddRec(Value *V);
1950
1951
  /// Proves that V doesn't overflow by adding SCEV predicate.
1952
  void setNoOverflow(Value *V, SCEVWrapPredicate::IncrementWrapFlags Flags);
1953
1954
  /// Returns true if we've proved that V doesn't wrap by means of a SCEV
1955
  /// predicate.
1956
  bool hasNoOverflow(Value *V, SCEVWrapPredicate::IncrementWrapFlags Flags);
1957
1958
  /// Returns the ScalarEvolution analysis used.
1959
2.41M
  ScalarEvolution *getSE() const { return &SE; }
1960
1961
  /// We need to explicitly define the copy constructor because of FlagsMap.
1962
  PredicatedScalarEvolution(const PredicatedScalarEvolution &);
1963
1964
  /// Print the SCEV mappings done by the Predicated Scalar Evolution.
1965
  /// The printed text is indented by \p Depth.
1966
  void print(raw_ostream &OS, unsigned Depth) const;
1967
1968
  /// Check if \p AR1 and \p AR2 are equal, while taking into account
1969
  /// Equal predicates in Preds.
1970
  bool areAddRecsEqualWithPreds(const SCEVAddRecExpr *AR1,
1971
                                const SCEVAddRecExpr *AR2) const;
1972
1973
private:
1974
  /// Increments the version number of the predicate.  This needs to be called
1975
  /// every time the SCEV predicate changes.
1976
  void updateGeneration();
1977
1978
  /// Holds a SCEV and the version number of the SCEV predicate used to
1979
  /// perform the rewrite of the expression.
1980
  using RewriteEntry = std::pair<unsigned, const SCEV *>;
1981
1982
  /// Maps a SCEV to the rewrite result of that SCEV at a certain version
1983
  /// number. If this number doesn't match the current Generation, we will
1984
  /// need to do a rewrite. To preserve the transformation order of previous
1985
  /// rewrites, we will rewrite the previous result instead of the original
1986
  /// SCEV.
1987
  DenseMap<const SCEV *, RewriteEntry> RewriteMap;
1988
1989
  /// Records what NoWrap flags we've added to a Value *.
1990
  ValueMap<Value *, SCEVWrapPredicate::IncrementWrapFlags> FlagsMap;
1991
1992
  /// The ScalarEvolution analysis.
1993
  ScalarEvolution &SE;
1994
1995
  /// The analyzed Loop.
1996
  const Loop &L;
1997
1998
  /// The SCEVPredicate that forms our context. We will rewrite all
1999
  /// expressions assuming that this predicate true.
2000
  SCEVUnionPredicate Preds;
2001
2002
  /// Marks the version of the SCEV predicate used. When rewriting a SCEV
2003
  /// expression we mark it with the version of the predicate. We use this to
2004
  /// figure out if the predicate has changed from the last rewrite of the
2005
  /// SCEV. If so, we need to perform a new rewrite.
2006
  unsigned Generation = 0;
2007
2008
  /// The backedge taken count.
2009
  const SCEV *BackedgeCount = nullptr;
2010
};
2011
2012
} // end namespace llvm
2013
2014
#endif // LLVM_ANALYSIS_SCALAREVOLUTION_H