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1 : //===- PhiValues.h - Phi Value Analysis -------------------------*- C++ -*-===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 : //
10 : // This file defines the PhiValues class, and associated passes, which can be
11 : // used to find the underlying values of the phis in a function, i.e. the
12 : // non-phi values that can be found by traversing the phi graph.
13 : //
14 : // This information is computed lazily and cached. If new phis are added to the
15 : // function they are handled correctly, but if an existing phi has its operands
16 : // modified PhiValues has to be notified by calling invalidateValue.
17 : //
18 : //===----------------------------------------------------------------------===//
19 :
20 : #ifndef LLVM_ANALYSIS_PHIVALUES_H
21 : #define LLVM_ANALYSIS_PHIVALUES_H
22 :
23 : #include "llvm/ADT/DenseMap.h"
24 : #include "llvm/ADT/DenseSet.h"
25 : #include "llvm/ADT/SmallPtrSet.h"
26 : #include "llvm/ADT/SmallVector.h"
27 : #include "llvm/IR/PassManager.h"
28 : #include "llvm/IR/ValueHandle.h"
29 : #include "llvm/Pass.h"
30 :
31 : namespace llvm {
32 :
33 : class Use;
34 : class Value;
35 : class PHINode;
36 : class Function;
37 :
38 : /// Class for calculating and caching the underlying values of phis in a
39 : /// function.
40 : ///
41 : /// Initially the PhiValues is empty, and gets incrementally populated whenever
42 : /// it is queried.
43 : class PhiValues {
44 : public:
45 : using ValueSet = SmallPtrSet<Value *, 4>;
46 :
47 : /// Construct an empty PhiValues.
48 151222 : PhiValues(const Function &F) : F(F) {}
49 :
50 : /// Get the underlying values of a phi.
51 : ///
52 : /// This returns the cached value if PN has previously been processed,
53 : /// otherwise it processes it first.
54 : const ValueSet &getValuesForPhi(const PHINode *PN);
55 :
56 : /// Notify PhiValues that the cached information using V is no longer valid
57 : ///
58 : /// Whenever a phi has its operands modified the cached values for that phi
59 : /// (and the phis that use that phi) become invalid. A user of PhiValues has
60 : /// to notify it of this by calling invalidateValue on either the operand or
61 : /// the phi, which will then clear the relevant cached information.
62 : void invalidateValue(const Value *V);
63 :
64 : /// Free the memory used by this class.
65 : void releaseMemory();
66 :
67 : /// Print out the values currently in the cache.
68 : void print(raw_ostream &OS) const;
69 :
70 : /// Handle invalidation events in the new pass manager.
71 : bool invalidate(Function &, const PreservedAnalyses &,
72 : FunctionAnalysisManager::Invalidator &);
73 :
74 : private:
75 : using PhiSet = SmallPtrSet<const PHINode *, 4>;
76 : using ConstValueSet = SmallPtrSet<const Value *, 4>;
77 :
78 : /// The next depth number to be used by processPhi.
79 : unsigned int NextDepthNumber = 1;
80 :
81 : /// Depth numbers of phis. Phis with the same depth number are part of the
82 : /// same strongly connected component.
83 : DenseMap<const PHINode *, unsigned int> DepthMap;
84 :
85 : /// Non-phi values reachable from each component.
86 : DenseMap<unsigned int, ValueSet> NonPhiReachableMap;
87 :
88 : /// All values reachable from each component.
89 : DenseMap<unsigned int, ConstValueSet> ReachableMap;
90 :
91 : /// A CallbackVH to notify PhiValues when a value is deleted or replaced, so
92 : /// that the cached information for that value can be cleared to avoid
93 : /// dangling pointers to invalid values.
94 1737797 : class PhiValuesCallbackVH final : public CallbackVH {
95 : PhiValues *PV;
96 : void deleted() override;
97 : void allUsesReplacedWith(Value *New) override;
98 :
99 : public:
100 : PhiValuesCallbackVH(Value *V, PhiValues *PV = nullptr)
101 1016587 : : CallbackVH(V), PV(PV) {}
102 : };
103 :
104 : /// A set of callbacks to the values that processPhi has seen.
105 : DenseSet<PhiValuesCallbackVH, DenseMapInfo<Value *>> TrackedValues;
106 :
107 : /// The function that the PhiValues is for.
108 : const Function &F;
109 :
110 : /// Process a phi so that its entries in the depth and reachable maps are
111 : /// fully populated.
112 : void processPhi(const PHINode *PN, SmallVector<const PHINode *, 8> &Stack);
113 : };
114 :
115 : /// The analysis pass which yields a PhiValues
116 : ///
117 : /// The analysis does nothing by itself, and just returns an empty PhiValues
118 : /// which will get filled in as it's used.
119 : class PhiValuesAnalysis : public AnalysisInfoMixin<PhiValuesAnalysis> {
120 : friend AnalysisInfoMixin<PhiValuesAnalysis>;
121 : static AnalysisKey Key;
122 :
123 : public:
124 : using Result = PhiValues;
125 : PhiValues run(Function &F, FunctionAnalysisManager &);
126 : };
127 :
128 : /// A pass for printing the PhiValues for a function.
129 : ///
130 : /// This pass doesn't print whatever information the PhiValues happens to hold,
131 : /// but instead first uses the PhiValues to analyze all the phis in the function
132 : /// so the complete information is printed.
133 : class PhiValuesPrinterPass : public PassInfoMixin<PhiValuesPrinterPass> {
134 : raw_ostream &OS;
135 :
136 : public:
137 3 : explicit PhiValuesPrinterPass(raw_ostream &OS) : OS(OS) {}
138 : PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
139 : };
140 :
141 : /// Wrapper pass for the legacy pass manager
142 : class PhiValuesWrapperPass : public FunctionPass {
143 : std::unique_ptr<PhiValues> Result;
144 :
145 : public:
146 : static char ID;
147 : PhiValuesWrapperPass();
148 :
149 : PhiValues &getResult() { return *Result; }
150 : const PhiValues &getResult() const { return *Result; }
151 :
152 : bool runOnFunction(Function &F) override;
153 : void releaseMemory() override;
154 : void getAnalysisUsage(AnalysisUsage &AU) const override;
155 : };
156 :
157 : } // namespace llvm
158 :
159 : #endif
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