/Users/buildslave/jenkins/sharedspace/clang-stage2-coverage-R@2/llvm/include/llvm/Analysis/DemandedBits.h
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1 | | //===- llvm/Analysis/DemandedBits.h - Determine demanded bits ---*- 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 pass implements a demanded bits analysis. A demanded bit is one that |
11 | | // contributes to a result; bits that are not demanded can be either zero or |
12 | | // one without affecting control or data flow. For example in this sequence: |
13 | | // |
14 | | // %1 = add i32 %x, %y |
15 | | // %2 = trunc i32 %1 to i16 |
16 | | // |
17 | | // Only the lowest 16 bits of %1 are demanded; the rest are removed by the |
18 | | // trunc. |
19 | | // |
20 | | //===----------------------------------------------------------------------===// |
21 | | |
22 | | #ifndef LLVM_ANALYSIS_DEMANDED_BITS_H |
23 | | #define LLVM_ANALYSIS_DEMANDED_BITS_H |
24 | | |
25 | | #include "llvm/ADT/APInt.h" |
26 | | #include "llvm/ADT/DenseMap.h" |
27 | | #include "llvm/ADT/Optional.h" |
28 | | #include "llvm/ADT/SmallPtrSet.h" |
29 | | #include "llvm/IR/PassManager.h" |
30 | | #include "llvm/Pass.h" |
31 | | |
32 | | namespace llvm { |
33 | | |
34 | | class AssumptionCache; |
35 | | class DominatorTree; |
36 | | class Function; |
37 | | class Instruction; |
38 | | struct KnownBits; |
39 | | class raw_ostream; |
40 | | |
41 | | class DemandedBits { |
42 | | public: |
43 | | DemandedBits(Function &F, AssumptionCache &AC, DominatorTree &DT) : |
44 | 1.44M | F(F), AC(AC), DT(DT) {} |
45 | | |
46 | | /// Return the bits demanded from instruction I. |
47 | | APInt getDemandedBits(Instruction *I); |
48 | | |
49 | | /// Return true if, during analysis, I could not be reached. |
50 | | bool isInstructionDead(Instruction *I); |
51 | | |
52 | | void print(raw_ostream &OS); |
53 | | |
54 | | private: |
55 | | void performAnalysis(); |
56 | | void determineLiveOperandBits(const Instruction *UserI, |
57 | | const Instruction *I, unsigned OperandNo, |
58 | | const APInt &AOut, APInt &AB, |
59 | | KnownBits &Known, KnownBits &Known2); |
60 | | |
61 | | Function &F; |
62 | | AssumptionCache ∾ |
63 | | DominatorTree &DT; |
64 | | |
65 | | bool Analyzed = false; |
66 | | |
67 | | // The set of visited instructions (non-integer-typed only). |
68 | | SmallPtrSet<Instruction*, 32> Visited; |
69 | | DenseMap<Instruction *, APInt> AliveBits; |
70 | | }; |
71 | | |
72 | | class DemandedBitsWrapperPass : public FunctionPass { |
73 | | private: |
74 | | mutable Optional<DemandedBits> DB; |
75 | | |
76 | | public: |
77 | | static char ID; // Pass identification, replacement for typeid |
78 | | |
79 | | DemandedBitsWrapperPass(); |
80 | | |
81 | | bool runOnFunction(Function &F) override; |
82 | | void getAnalysisUsage(AnalysisUsage &AU) const override; |
83 | | |
84 | | /// Clean up memory in between runs |
85 | | void releaseMemory() override; |
86 | | |
87 | 1.44M | DemandedBits &getDemandedBits() { return *DB; } |
88 | | |
89 | | void print(raw_ostream &OS, const Module *M) const override; |
90 | | }; |
91 | | |
92 | | /// An analysis that produces \c DemandedBits for a function. |
93 | | class DemandedBitsAnalysis : public AnalysisInfoMixin<DemandedBitsAnalysis> { |
94 | | friend AnalysisInfoMixin<DemandedBitsAnalysis>; |
95 | | |
96 | | static AnalysisKey Key; |
97 | | |
98 | | public: |
99 | | /// \brief Provide the result type for this analysis pass. |
100 | | using Result = DemandedBits; |
101 | | |
102 | | /// \brief Run the analysis pass over a function and produce demanded bits |
103 | | /// information. |
104 | | DemandedBits run(Function &F, FunctionAnalysisManager &AM); |
105 | | }; |
106 | | |
107 | | /// \brief Printer pass for DemandedBits |
108 | | class DemandedBitsPrinterPass : public PassInfoMixin<DemandedBitsPrinterPass> { |
109 | | raw_ostream &OS; |
110 | | |
111 | | public: |
112 | 0 | explicit DemandedBitsPrinterPass(raw_ostream &OS) : OS(OS) {} |
113 | | |
114 | | PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); |
115 | | }; |
116 | | |
117 | | /// Create a demanded bits analysis pass. |
118 | | FunctionPass *createDemandedBitsWrapperPass(); |
119 | | |
120 | | } // end namespace llvm |
121 | | |
122 | | #endif // LLVM_ANALYSIS_DEMANDED_BITS_H |