1 //===-- Arena.h -------------------------------*- 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 #ifndef LLVM_CLANG_ANALYSIS_FLOWSENSITIVE__ARENA_H 9 #define LLVM_CLANG_ANALYSIS_FLOWSENSITIVE__ARENA_H 10 11 #include "clang/Analysis/FlowSensitive/Formula.h" 12 #include "clang/Analysis/FlowSensitive/StorageLocation.h" 13 #include "clang/Analysis/FlowSensitive/Value.h" 14 #include <vector> 15 16 namespace clang::dataflow { 17 18 /// The Arena owns the objects that model data within an analysis. 19 /// For example, `Value`, `StorageLocation`, `Atom`, and `Formula`. 20 class Arena { 21 public: 22 Arena() : True(makeAtom()), False(makeAtom()) {} 23 Arena(const Arena &) = delete; 24 Arena &operator=(const Arena &) = delete; 25 26 /// Creates a `T` (some subclass of `StorageLocation`), forwarding `args` to 27 /// the constructor, and returns a reference to it. 28 /// 29 /// The `DataflowAnalysisContext` takes ownership of the created object. The 30 /// object will be destroyed when the `DataflowAnalysisContext` is destroyed. 31 template <typename T, typename... Args> 32 std::enable_if_t<std::is_base_of<StorageLocation, T>::value, T &> 33 create(Args &&...args) { 34 // Note: If allocation of individual `StorageLocation`s turns out to be 35 // costly, consider creating specializations of `create<T>` for commonly 36 // used `StorageLocation` subclasses and make them use a `BumpPtrAllocator`. 37 return *cast<T>( 38 Locs.emplace_back(std::make_unique<T>(std::forward<Args>(args)...)) 39 .get()); 40 } 41 42 /// Creates a `T` (some subclass of `Value`), forwarding `args` to the 43 /// constructor, and returns a reference to it. 44 /// 45 /// The `DataflowAnalysisContext` takes ownership of the created object. The 46 /// object will be destroyed when the `DataflowAnalysisContext` is destroyed. 47 template <typename T, typename... Args> 48 std::enable_if_t<std::is_base_of<Value, T>::value, T &> 49 create(Args &&...args) { 50 // Note: If allocation of individual `Value`s turns out to be costly, 51 // consider creating specializations of `create<T>` for commonly used 52 // `Value` subclasses and make them use a `BumpPtrAllocator`. 53 return *cast<T>( 54 Vals.emplace_back(std::make_unique<T>(std::forward<Args>(args)...)) 55 .get()); 56 } 57 58 /// Creates a BoolValue wrapping a particular formula. 59 /// 60 /// Passing in the same formula will result in the same BoolValue. 61 /// FIXME: Interning BoolValues but not other Values is inconsistent. 62 /// Decide whether we want Value interning or not. 63 BoolValue &makeBoolValue(const Formula &); 64 65 /// Creates a fresh atom and wraps in in an AtomicBoolValue. 66 /// FIXME: For now, identical-address AtomicBoolValue <=> identical atom. 67 /// Stop relying on pointer identity and remove this guarantee. 68 AtomicBoolValue &makeAtomValue() { 69 return cast<AtomicBoolValue>(makeBoolValue(makeAtomRef(makeAtom()))); 70 } 71 72 /// Creates a fresh Top boolean value. 73 TopBoolValue &makeTopValue() { 74 // No need for deduplicating: there's no way to create aliasing Tops. 75 return create<TopBoolValue>(makeAtomRef(makeAtom())); 76 } 77 78 /// Returns a symbolic integer value that models an integer literal equal to 79 /// `Value`. These literals are the same every time. 80 /// Integer literals are not typed; the type is determined by the `Expr` that 81 /// an integer literal is associated with. 82 IntegerValue &makeIntLiteral(llvm::APInt Value); 83 84 // Factories for boolean formulas. 85 // Formulas are interned: passing the same arguments return the same result. 86 // For commutative operations like And/Or, interning ignores order. 87 // Simplifications are applied: makeOr(X, X) => X, etc. 88 89 /// Returns a formula for the conjunction of `LHS` and `RHS`. 90 const Formula &makeAnd(const Formula &LHS, const Formula &RHS); 91 92 /// Returns a formula for the disjunction of `LHS` and `RHS`. 93 const Formula &makeOr(const Formula &LHS, const Formula &RHS); 94 95 /// Returns a formula for the negation of `Val`. 96 const Formula &makeNot(const Formula &Val); 97 98 /// Returns a formula for `LHS => RHS`. 99 const Formula &makeImplies(const Formula &LHS, const Formula &RHS); 100 101 /// Returns a formula for `LHS <=> RHS`. 102 const Formula &makeEquals(const Formula &LHS, const Formula &RHS); 103 104 /// Returns a formula for the variable A. 105 const Formula &makeAtomRef(Atom A); 106 107 /// Returns a formula for a literal true/false. 108 const Formula &makeLiteral(bool Value) { 109 return makeAtomRef(Value ? True : False); 110 } 111 112 /// Returns a new atomic boolean variable, distinct from any other. 113 Atom makeAtom() { return static_cast<Atom>(NextAtom++); }; 114 115 /// Creates a fresh flow condition and returns a token that identifies it. The 116 /// token can be used to perform various operations on the flow condition such 117 /// as adding constraints to it, forking it, joining it with another flow 118 /// condition, or checking implications. 119 Atom makeFlowConditionToken() { return makeAtom(); } 120 121 private: 122 llvm::BumpPtrAllocator Alloc; 123 124 // Storage for the state of a program. 125 std::vector<std::unique_ptr<StorageLocation>> Locs; 126 std::vector<std::unique_ptr<Value>> Vals; 127 128 // Indices that are used to avoid recreating the same integer literals and 129 // composite boolean values. 130 llvm::DenseMap<llvm::APInt, IntegerValue *> IntegerLiterals; 131 using FormulaPair = std::pair<const Formula *, const Formula *>; 132 llvm::DenseMap<FormulaPair, const Formula *> Ands; 133 llvm::DenseMap<FormulaPair, const Formula *> Ors; 134 llvm::DenseMap<const Formula *, const Formula *> Nots; 135 llvm::DenseMap<FormulaPair, const Formula *> Implies; 136 llvm::DenseMap<FormulaPair, const Formula *> Equals; 137 llvm::DenseMap<Atom, const Formula *> AtomRefs; 138 139 llvm::DenseMap<const Formula *, BoolValue *> FormulaValues; 140 unsigned NextAtom = 0; 141 142 Atom True, False; 143 }; 144 145 } // namespace clang::dataflow 146 147 #endif // LLVM_CLANG_ANALYSIS_FLOWSENSITIVE__ARENA_H 148