LLVM  13.0.0git
PhiValues.h
Go to the documentation of this file.
1 //===- PhiValues.h - Phi Value 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 //
9 // This file defines the PhiValues class, and associated passes, which can be
10 // used to find the underlying values of the phis in a function, i.e. the
11 // non-phi values that can be found by traversing the phi graph.
12 //
13 // This information is computed lazily and cached. If new phis are added to the
14 // function they are handled correctly, but if an existing phi has its operands
15 // modified PhiValues has to be notified by calling invalidateValue.
16 //
17 //===----------------------------------------------------------------------===//
18 
19 #ifndef LLVM_ANALYSIS_PHIVALUES_H
20 #define LLVM_ANALYSIS_PHIVALUES_H
21 
22 #include "llvm/ADT/DenseMap.h"
23 #include "llvm/ADT/DenseSet.h"
24 #include "llvm/ADT/SetVector.h"
25 #include "llvm/ADT/SmallVector.h"
26 #include "llvm/IR/PassManager.h"
27 #include "llvm/IR/ValueHandle.h"
28 #include "llvm/Pass.h"
29 
30 namespace llvm {
31 
32 class Value;
33 class PHINode;
34 class Function;
35 
36 /// Class for calculating and caching the underlying values of phis in a
37 /// function.
38 ///
39 /// Initially the PhiValues is empty, and gets incrementally populated whenever
40 /// it is queried.
41 class PhiValues {
42 public:
44 
45  /// Construct an empty PhiValues.
46  PhiValues(const Function &F) : F(F) {}
47 
48  /// Get the underlying values of a phi.
49  ///
50  /// This returns the cached value if PN has previously been processed,
51  /// otherwise it processes it first.
52  const ValueSet &getValuesForPhi(const PHINode *PN);
53 
54  /// Notify PhiValues that the cached information using V is no longer valid
55  ///
56  /// Whenever a phi has its operands modified the cached values for that phi
57  /// (and the phis that use that phi) become invalid. A user of PhiValues has
58  /// to notify it of this by calling invalidateValue on either the operand or
59  /// the phi, which will then clear the relevant cached information.
60  void invalidateValue(const Value *V);
61 
62  /// Free the memory used by this class.
63  void releaseMemory();
64 
65  /// Print out the values currently in the cache.
66  void print(raw_ostream &OS) const;
67 
68  /// Handle invalidation events in the new pass manager.
69  bool invalidate(Function &, const PreservedAnalyses &,
71 
72 private:
73  using ConstValueSet = SmallSetVector<const Value *, 4>;
74 
75  /// The next depth number to be used by processPhi.
76  unsigned int NextDepthNumber = 1;
77 
78  /// Depth numbers of phis. Phis with the same depth number are part of the
79  /// same strongly connected component.
81 
82  /// Non-phi values reachable from each component.
83  DenseMap<unsigned int, ValueSet> NonPhiReachableMap;
84 
85  /// All values reachable from each component.
87 
88  /// A CallbackVH to notify PhiValues when a value is deleted or replaced, so
89  /// that the cached information for that value can be cleared to avoid
90  /// dangling pointers to invalid values.
91  class PhiValuesCallbackVH final : public CallbackVH {
92  PhiValues *PV;
93  void deleted() override;
94  void allUsesReplacedWith(Value *New) override;
95 
96  public:
97  PhiValuesCallbackVH(Value *V, PhiValues *PV = nullptr)
98  : CallbackVH(V), PV(PV) {}
99  };
100 
101  /// A set of callbacks to the values that processPhi has seen.
102  DenseSet<PhiValuesCallbackVH, DenseMapInfo<Value *>> TrackedValues;
103 
104  /// The function that the PhiValues is for.
105  const Function &F;
106 
107  /// Process a phi so that its entries in the depth and reachable maps are
108  /// fully populated.
109  void processPhi(const PHINode *PN, SmallVectorImpl<const PHINode *> &Stack);
110 };
111 
112 /// The analysis pass which yields a PhiValues
113 ///
114 /// The analysis does nothing by itself, and just returns an empty PhiValues
115 /// which will get filled in as it's used.
116 class PhiValuesAnalysis : public AnalysisInfoMixin<PhiValuesAnalysis> {
118  static AnalysisKey Key;
119 
120 public:
121  using Result = PhiValues;
123 };
124 
125 /// A pass for printing the PhiValues for a function.
126 ///
127 /// This pass doesn't print whatever information the PhiValues happens to hold,
128 /// but instead first uses the PhiValues to analyze all the phis in the function
129 /// so the complete information is printed.
130 class PhiValuesPrinterPass : public PassInfoMixin<PhiValuesPrinterPass> {
131  raw_ostream &OS;
132 
133 public:
134  explicit PhiValuesPrinterPass(raw_ostream &OS) : OS(OS) {}
136 };
137 
138 /// Wrapper pass for the legacy pass manager
140  std::unique_ptr<PhiValues> Result;
141 
142 public:
143  static char ID;
145 
146  PhiValues &getResult() { return *Result; }
147  const PhiValues &getResult() const { return *Result; }
148 
149  bool runOnFunction(Function &F) override;
150  void releaseMemory() override;
151  void getAnalysisUsage(AnalysisUsage &AU) const override;
152 };
153 
154 } // namespace llvm
155 
156 #endif
llvm::PreservedAnalyses
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:155
llvm::PhiValues::invalidate
bool invalidate(Function &, const PreservedAnalyses &, FunctionAnalysisManager::Invalidator &)
Handle invalidation events in the new pass manager.
Definition: PhiValues.cpp:26
llvm
Definition: AllocatorList.h:23
llvm::PhiValuesWrapperPass::getResult
const PhiValues & getResult() const
Definition: PhiValues.h:147
llvm::PhiValuesWrapperPass::getResult
PhiValues & getResult()
Definition: PhiValues.h:146
llvm::PhiValuesPrinterPass::run
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: PhiValues.cpp:195
llvm::PhiValuesPrinterPass::PhiValuesPrinterPass
PhiValuesPrinterPass(raw_ostream &OS)
Definition: PhiValues.h:134
llvm::PassInfoMixin
A CRTP mix-in to automatically provide informational APIs needed for passes.
Definition: PassManager.h:374
llvm::Function
Definition: Function.h:61
llvm::PhiValues::ValueSet
SmallSetVector< Value *, 4 > ValueSet
Definition: PhiValues.h:43
Pass.h
llvm::PhiValues::print
void print(raw_ostream &OS) const
Print out the values currently in the cache.
Definition: PhiValues.cpp:163
llvm::PhiValuesWrapperPass::getAnalysisUsage
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
Definition: PhiValues.cpp:219
llvm::PhiValuesWrapperPass
Wrapper pass for the legacy pass manager.
Definition: PhiValues.h:139
DenseMap.h
llvm::PhiValues::PhiValues
PhiValues(const Function &F)
Construct an empty PhiValues.
Definition: PhiValues.h:46
F
#define F(x, y, z)
Definition: MD5.cpp:56
llvm::PhiValuesAnalysis::run
PhiValues run(Function &F, FunctionAnalysisManager &)
Definition: PhiValues.cpp:191
llvm::PhiValuesWrapperPass::runOnFunction
bool runOnFunction(Function &F) override
runOnFunction - Virtual method overriden by subclasses to do the per-function processing of the pass.
Definition: PhiValues.cpp:210
llvm::PhiValuesWrapperPass::releaseMemory
void releaseMemory() override
releaseMemory() - This member can be implemented by a pass if it wants to be able to release its memo...
Definition: PhiValues.cpp:215
llvm::PhiValues::releaseMemory
void releaseMemory()
Free the memory used by this class.
Definition: PhiValues.cpp:157
llvm::AnalysisUsage
Represent the analysis usage information of a pass.
Definition: PassAnalysisSupport.h:47
DenseSet.h
llvm::raw_ostream
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:50
llvm::AnalysisManager::Invalidator
API to communicate dependencies between analyses during invalidation.
Definition: PassManager.h:656
llvm::PhiValues::getValuesForPhi
const ValueSet & getValuesForPhi(const PHINode *PN)
Get the underlying values of a phi.
Definition: PhiValues.cpp:125
llvm::PhiValuesPrinterPass
A pass for printing the PhiValues for a function.
Definition: PhiValues.h:130
llvm::DenseMap
Definition: DenseMap.h:714
llvm::AnalysisKey
A special type used by analysis passes to provide an address that identifies that particular analysis...
Definition: PassManager.h:72
llvm::PhiValuesAnalysis
The analysis pass which yields a PhiValues.
Definition: PhiValues.h:116
llvm::PhiValuesWrapperPass::ID
static char ID
Definition: PhiValues.h:143
llvm::AnalysisInfoMixin
A CRTP mix-in that provides informational APIs needed for analysis passes.
Definition: PassManager.h:391
ValueHandle.h
llvm::PhiValues::invalidateValue
void invalidateValue(const Value *V)
Notify PhiValues that the cached information using V is no longer valid.
Definition: PhiValues.cpp:137
llvm::TargetStackID::Value
Value
Definition: TargetFrameLowering.h:27
PassManager.h
llvm::CallbackVH
Value handle with callbacks on RAUW and destruction.
Definition: ValueHandle.h:383
llvm::PhiValues
Class for calculating and caching the underlying values of phis in a function.
Definition: PhiValues.h:41
SmallVector.h
llvm::PHINode
Definition: Instructions.h:2600
llvm::SmallSetVector
A SetVector that performs no allocations if smaller than a certain size.
Definition: SetVector.h:307
llvm::AnalysisManager
A container for analyses that lazily runs them and caches their results.
Definition: InstructionSimplify.h:44
llvm::FunctionPass
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:298
llvm::Value
LLVM Value Representation.
Definition: Value.h:75
llvm::codeview::PublicSymFlags::Function
@ Function
llvm::PhiValuesWrapperPass::PhiValuesWrapperPass
PhiValuesWrapperPass()
Definition: PhiValues.cpp:206
SetVector.h