Coverage Report

Created: 2019-07-24 05:18

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/Analysis/BasicAliasAnalysis.h
Line
Count
Source (jump to first uncovered line)
1
//===- BasicAliasAnalysis.h - Stateless, local Alias Analysis ---*- C++ -*-===//
2
//
3
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4
// See https://llvm.org/LICENSE.txt for license information.
5
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6
//
7
//===----------------------------------------------------------------------===//
8
/// \file
9
/// This is the interface for LLVM's primary stateless and local alias analysis.
10
///
11
//===----------------------------------------------------------------------===//
12
13
#ifndef LLVM_ANALYSIS_BASICALIASANALYSIS_H
14
#define LLVM_ANALYSIS_BASICALIASANALYSIS_H
15
16
#include "llvm/ADT/DenseMap.h"
17
#include "llvm/ADT/Optional.h"
18
#include "llvm/ADT/SmallPtrSet.h"
19
#include "llvm/ADT/SmallVector.h"
20
#include "llvm/Analysis/AliasAnalysis.h"
21
#include "llvm/Analysis/AssumptionCache.h"
22
#include "llvm/Analysis/MemoryLocation.h"
23
#include "llvm/IR/InstrTypes.h"
24
#include "llvm/IR/PassManager.h"
25
#include "llvm/Pass.h"
26
#include <algorithm>
27
#include <cstdint>
28
#include <memory>
29
#include <utility>
30
31
namespace llvm {
32
33
struct AAMDNodes;
34
class APInt;
35
class AssumptionCache;
36
class BasicBlock;
37
class DataLayout;
38
class DominatorTree;
39
class Function;
40
class GEPOperator;
41
class LoopInfo;
42
class PHINode;
43
class SelectInst;
44
class TargetLibraryInfo;
45
class PhiValues;
46
class Value;
47
48
/// This is the AA result object for the basic, local, and stateless alias
49
/// analysis. It implements the AA query interface in an entirely stateless
50
/// manner. As one consequence, it is never invalidated due to IR changes.
51
/// While it does retain some storage, that is used as an optimization and not
52
/// to preserve information from query to query. However it does retain handles
53
/// to various other analyses and must be recomputed when those analyses are.
54
class BasicAAResult : public AAResultBase<BasicAAResult> {
55
  friend AAResultBase<BasicAAResult>;
56
57
  const DataLayout &DL;
58
  const Function &F;
59
  const TargetLibraryInfo &TLI;
60
  AssumptionCache &AC;
61
  DominatorTree *DT;
62
  LoopInfo *LI;
63
  PhiValues *PV;
64
65
public:
66
  BasicAAResult(const DataLayout &DL, const Function &F,
67
                const TargetLibraryInfo &TLI, AssumptionCache &AC,
68
                DominatorTree *DT = nullptr, LoopInfo *LI = nullptr,
69
                PhiValues *PV = nullptr)
70
      : AAResultBase(), DL(DL), F(F), TLI(TLI), AC(AC), DT(DT), LI(LI), PV(PV)
71
10.7M
        {}
72
73
  BasicAAResult(const BasicAAResult &Arg)
74
      : AAResultBase(Arg), DL(Arg.DL), F(Arg.F), TLI(Arg.TLI), AC(Arg.AC),
75
0
        DT(Arg.DT),  LI(Arg.LI), PV(Arg.PV) {}
76
  BasicAAResult(BasicAAResult &&Arg)
77
      : AAResultBase(std::move(Arg)), DL(Arg.DL), F(Arg.F), TLI(Arg.TLI),
78
1.18M
        AC(Arg.AC), DT(Arg.DT), LI(Arg.LI), PV(Arg.PV) {}
79
80
  /// Handle invalidation events in the new pass manager.
81
  bool invalidate(Function &Fn, const PreservedAnalyses &PA,
82
                  FunctionAnalysisManager::Invalidator &Inv);
83
84
  AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
85
                    AAQueryInfo &AAQI);
86
87
  ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc,
88
                           AAQueryInfo &AAQI);
89
90
  ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2,
91
                           AAQueryInfo &AAQI);
92
93
  /// Chases pointers until we find a (constant global) or not.
94
  bool pointsToConstantMemory(const MemoryLocation &Loc, AAQueryInfo &AAQI,
95
                              bool OrLocal);
96
97
  /// Get the location associated with a pointer argument of a callsite.
98
  ModRefInfo getArgModRefInfo(const CallBase *Call, unsigned ArgIdx);
99
100
  /// Returns the behavior when calling the given call site.
101
  FunctionModRefBehavior getModRefBehavior(const CallBase *Call);
102
103
  /// Returns the behavior when calling the given function. For use when the
104
  /// call site is not known.
105
  FunctionModRefBehavior getModRefBehavior(const Function *Fn);
106
107
private:
108
  // A linear transformation of a Value; this class represents ZExt(SExt(V,
109
  // SExtBits), ZExtBits) * Scale + Offset.
110
  struct VariableGEPIndex {
111
    // An opaque Value - we can't decompose this further.
112
    const Value *V;
113
114
    // We need to track what extensions we've done as we consider the same Value
115
    // with different extensions as different variables in a GEP's linear
116
    // expression;
117
    // e.g.: if V == -1, then sext(x) != zext(x).
118
    unsigned ZExtBits;
119
    unsigned SExtBits;
120
121
    APInt Scale;
122
123
156k
    bool operator==(const VariableGEPIndex &Other) const {
124
156k
      return V == Other.V && 
ZExtBits == Other.ZExtBits49.4k
&&
125
156k
             
SExtBits == Other.SExtBits49.4k
&&
Scale == Other.Scale49.4k
;
126
156k
    }
127
128
0
    bool operator!=(const VariableGEPIndex &Other) const {
129
0
      return !operator==(Other);
130
0
    }
131
  };
132
133
  // Represents the internal structure of a GEP, decomposed into a base pointer,
134
  // constant offsets, and variable scaled indices.
135
  struct DecomposedGEP {
136
    // Base pointer of the GEP
137
    const Value *Base;
138
    // Total constant offset w.r.t the base from indexing into structs
139
    APInt StructOffset;
140
    // Total constant offset w.r.t the base from indexing through
141
    // pointers/arrays/vectors
142
    APInt OtherOffset;
143
    // Scaled variable (non-constant) indices.
144
    SmallVector<VariableGEPIndex, 4> VarIndices;
145
  };
146
147
  /// Tracks phi nodes we have visited.
148
  ///
149
  /// When interpret "Value" pointer equality as value equality we need to make
150
  /// sure that the "Value" is not part of a cycle. Otherwise, two uses could
151
  /// come from different "iterations" of a cycle and see different values for
152
  /// the same "Value" pointer.
153
  ///
154
  /// The following example shows the problem:
155
  ///   %p = phi(%alloca1, %addr2)
156
  ///   %l = load %ptr
157
  ///   %addr1 = gep, %alloca2, 0, %l
158
  ///   %addr2 = gep  %alloca2, 0, (%l + 1)
159
  ///      alias(%p, %addr1) -> MayAlias !
160
  ///   store %l, ...
161
  SmallPtrSet<const BasicBlock *, 8> VisitedPhiBBs;
162
163
  /// Tracks instructions visited by pointsToConstantMemory.
164
  SmallPtrSet<const Value *, 16> Visited;
165
166
  static const Value *
167
  GetLinearExpression(const Value *V, APInt &Scale, APInt &Offset,
168
                      unsigned &ZExtBits, unsigned &SExtBits,
169
                      const DataLayout &DL, unsigned Depth, AssumptionCache *AC,
170
                      DominatorTree *DT, bool &NSW, bool &NUW);
171
172
  static bool DecomposeGEPExpression(const Value *V, DecomposedGEP &Decomposed,
173
      const DataLayout &DL, AssumptionCache *AC, DominatorTree *DT);
174
175
  static bool isGEPBaseAtNegativeOffset(const GEPOperator *GEPOp,
176
      const DecomposedGEP &DecompGEP, const DecomposedGEP &DecompObject,
177
      LocationSize ObjectAccessSize);
178
179
  /// A Heuristic for aliasGEP that searches for a constant offset
180
  /// between the variables.
181
  ///
182
  /// GetLinearExpression has some limitations, as generally zext(%x + 1)
183
  /// != zext(%x) + zext(1) if the arithmetic overflows. GetLinearExpression
184
  /// will therefore conservatively refuse to decompose these expressions.
185
  /// However, we know that, for all %x, zext(%x) != zext(%x + 1), even if
186
  /// the addition overflows.
187
  bool
188
  constantOffsetHeuristic(const SmallVectorImpl<VariableGEPIndex> &VarIndices,
189
                          LocationSize V1Size, LocationSize V2Size,
190
                          APInt BaseOffset, AssumptionCache *AC,
191
                          DominatorTree *DT);
192
193
  bool isValueEqualInPotentialCycles(const Value *V1, const Value *V2);
194
195
  void GetIndexDifference(SmallVectorImpl<VariableGEPIndex> &Dest,
196
                          const SmallVectorImpl<VariableGEPIndex> &Src);
197
198
  AliasResult aliasGEP(const GEPOperator *V1, LocationSize V1Size,
199
                       const AAMDNodes &V1AAInfo, const Value *V2,
200
                       LocationSize V2Size, const AAMDNodes &V2AAInfo,
201
                       const Value *UnderlyingV1, const Value *UnderlyingV2,
202
                       AAQueryInfo &AAQI);
203
204
  AliasResult aliasPHI(const PHINode *PN, LocationSize PNSize,
205
                       const AAMDNodes &PNAAInfo, const Value *V2,
206
                       LocationSize V2Size, const AAMDNodes &V2AAInfo,
207
                       const Value *UnderV2, AAQueryInfo &AAQI);
208
209
  AliasResult aliasSelect(const SelectInst *SI, LocationSize SISize,
210
                          const AAMDNodes &SIAAInfo, const Value *V2,
211
                          LocationSize V2Size, const AAMDNodes &V2AAInfo,
212
                          const Value *UnderV2, AAQueryInfo &AAQI);
213
214
  AliasResult aliasCheck(const Value *V1, LocationSize V1Size,
215
                         AAMDNodes V1AATag, const Value *V2,
216
                         LocationSize V2Size, AAMDNodes V2AATag,
217
                         AAQueryInfo &AAQI, const Value *O1 = nullptr,
218
                         const Value *O2 = nullptr);
219
};
220
221
/// Analysis pass providing a never-invalidated alias analysis result.
222
class BasicAA : public AnalysisInfoMixin<BasicAA> {
223
  friend AnalysisInfoMixin<BasicAA>;
224
225
  static AnalysisKey Key;
226
227
public:
228
  using Result = BasicAAResult;
229
230
  BasicAAResult run(Function &F, FunctionAnalysisManager &AM);
231
};
232
233
/// Legacy wrapper pass to provide the BasicAAResult object.
234
class BasicAAWrapperPass : public FunctionPass {
235
  std::unique_ptr<BasicAAResult> Result;
236
237
  virtual void anchor();
238
239
public:
240
  static char ID;
241
242
  BasicAAWrapperPass();
243
244
9.40M
  BasicAAResult &getResult() { return *Result; }
245
0
  const BasicAAResult &getResult() const { return *Result; }
246
247
  bool runOnFunction(Function &F) override;
248
  void getAnalysisUsage(AnalysisUsage &AU) const override;
249
};
250
251
FunctionPass *createBasicAAWrapperPass();
252
253
/// A helper for the legacy pass manager to create a \c BasicAAResult object
254
/// populated to the best of our ability for a particular function when inside
255
/// of a \c ModulePass or a \c CallGraphSCCPass.
256
BasicAAResult createLegacyPMBasicAAResult(Pass &P, Function &F);
257
258
/// This class is a functor to be used in legacy module or SCC passes for
259
/// computing AA results for a function. We store the results in fields so that
260
/// they live long enough to be queried, but we re-use them each time.
261
class LegacyAARGetter {
262
  Pass &P;
263
  Optional<BasicAAResult> BAR;
264
  Optional<AAResults> AAR;
265
266
public:
267
2.12M
  LegacyAARGetter(Pass &P) : P(P) {}
268
1.17M
  AAResults &operator()(Function &F) {
269
1.17M
    BAR.emplace(createLegacyPMBasicAAResult(P, F));
270
1.17M
    AAR.emplace(createLegacyPMAAResults(P, F, *BAR));
271
1.17M
    return *AAR;
272
1.17M
  }
273
};
274
275
} // end namespace llvm
276
277
#endif // LLVM_ANALYSIS_BASICALIASANALYSIS_H