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
30namespace llvm {
31
32class Value;
33class PHINode;
34class 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.
41class PhiValues {
42public:
43 using ValueSet = SmallSetVector<Value *, 4>;
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54 /// Notify PhiValues that the cached information using V is no longer valid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 &,
70 FunctionAnalysisManager::Invalidator &);
71
72private:
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.
80 DenseMap<const PHINode *, unsigned int> DepthMap;
81
82 /// Non-phi values reachable from each component.
83 DenseMap<unsigned int, ValueSet> NonPhiReachableMap;
84
85 /// All values reachable from each component.
86 DenseMap<unsigned int, ConstValueSet> ReachableMap;
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.
116class PhiValuesAnalysis : public AnalysisInfoMixin<PhiValuesAnalysis> {
117 friend AnalysisInfoMixin<PhiValuesAnalysis>;
118 static AnalysisKey Key;
119
120public:
121 using Result = PhiValues;
122 PhiValues run(Function &F, FunctionAnalysisManager &);
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.
130class PhiValuesPrinterPass : public PassInfoMixin<PhiValuesPrinterPass> {
131 raw_ostream &OS;
132
133public:
134 explicit PhiValuesPrinterPass(raw_ostream &OS) : OS(OS) {}
135 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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