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/IR/PassManager.h"
26#include "llvm/IR/ValueHandle.h"
27#include "llvm/Pass.h"
28
29namespace llvm {
30
31class Value;
32class PHINode;
33class Function;
34
35/// Class for calculating and caching the underlying values of phis in a
36/// function.
37///
38/// Initially the PhiValues is empty, and gets incrementally populated whenever
39/// it is queried.
40class PhiValues {
41public:
42 using ValueSet = SmallSetVector<Value *, 4>;
43
44 /// Construct an empty PhiValues.
45 PhiValues(const Function &F) : F(F) {}
46
47 /// Get the underlying values of a phi.
48 ///
49 /// This returns the cached value if PN has previously been processed,
50 /// otherwise it processes it first.
51 const ValueSet &getValuesForPhi(const PHINode *PN);
52
53 /// Notify PhiValues that the cached information using V is no longer valid
54 ///
55 /// Whenever a phi has its operands modified the cached values for that phi
56 /// (and the phis that use that phi) become invalid. A user of PhiValues has
57 /// to notify it of this by calling invalidateValue on either the operand or
58 /// the phi, which will then clear the relevant cached information.
59 void invalidateValue(const Value *V);
60
61 /// Free the memory used by this class.
62 void releaseMemory();
63
64 /// Print out the values currently in the cache.
65 void print(raw_ostream &OS) const;
66
67 /// Handle invalidation events in the new pass manager.
68 bool invalidate(Function &, const PreservedAnalyses &,
69 FunctionAnalysisManager::Invalidator &);
70
71private:
72 using ConstValueSet = SmallSetVector<const Value *, 4>;
73
74 /// The next depth number to be used by processPhi.
75 unsigned int NextDepthNumber = 1;
76
77 /// Depth numbers of phis. Phis with the same depth number are part of the
78 /// same strongly connected component.
79 DenseMap<const PHINode *, unsigned int> DepthMap;
80
81 /// Non-phi values reachable from each component.
82 DenseMap<unsigned int, ValueSet> NonPhiReachableMap;
83
84 /// All values reachable from each component.
85 DenseMap<unsigned int, ConstValueSet> ReachableMap;
86
87 /// A CallbackVH to notify PhiValues when a value is deleted or replaced, so
88 /// that the cached information for that value can be cleared to avoid
89 /// dangling pointers to invalid values.
90 class PhiValuesCallbackVH final : public CallbackVH {
91 PhiValues *PV;
92 void deleted() override;
93 void allUsesReplacedWith(Value *New) override;
94
95 public:
96 PhiValuesCallbackVH(Value *V, PhiValues *PV = nullptr)
97 : CallbackVH(V), PV(PV) {}
98 };
99
100 /// A set of callbacks to the values that processPhi has seen.
101 DenseSet<PhiValuesCallbackVH, DenseMapInfo<Value *>> TrackedValues;
102
103 /// The function that the PhiValues is for.
104 const Function &F;
105
106 /// Process a phi so that its entries in the depth and reachable maps are
107 /// fully populated.
108 void processPhi(const PHINode *PN, SmallVectorImpl<const PHINode *> &Stack);
109};
110
111/// The analysis pass which yields a PhiValues
112///
113/// The analysis does nothing by itself, and just returns an empty PhiValues
114/// which will get filled in as it's used.
115class PhiValuesAnalysis : public AnalysisInfoMixin<PhiValuesAnalysis> {
116 friend AnalysisInfoMixin<PhiValuesAnalysis>;
117 static AnalysisKey Key;
118
119public:
120 using Result = PhiValues;
121 PhiValues run(Function &F, FunctionAnalysisManager &);
122};
123
124/// A pass for printing the PhiValues for a function.
125///
126/// This pass doesn't print whatever information the PhiValues happens to hold,
127/// but instead first uses the PhiValues to analyze all the phis in the function
128/// so the complete information is printed.
129class PhiValuesPrinterPass : public PassInfoMixin<PhiValuesPrinterPass> {
130 raw_ostream &OS;
131
132public:
133 explicit PhiValuesPrinterPass(raw_ostream &OS) : OS(OS) {}
134 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
135 static bool isRequired() { return true; }
136};
137
138/// Wrapper pass for the legacy pass manager
139class PhiValuesWrapperPass : public FunctionPass {
140 std::unique_ptr<PhiValues> Result;
141
142public:
143 static char ID;
144 PhiValuesWrapperPass();
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
157

source code of llvm/include/llvm/Analysis/PhiValues.h