| //===-- DataflowAnalysisContext.h -------------------------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines a DataflowAnalysisContext class that owns objects that |
| // encompass the state of a program and stores context that is used during |
| // dataflow analysis. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_DATAFLOWANALYSISCONTEXT_H |
| #define LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_DATAFLOWANALYSISCONTEXT_H |
| |
| #include "clang/AST/Decl.h" |
| #include "clang/AST/Expr.h" |
| #include "clang/AST/TypeOrdering.h" |
| #include "clang/Analysis/FlowSensitive/Arena.h" |
| #include "clang/Analysis/FlowSensitive/ControlFlowContext.h" |
| #include "clang/Analysis/FlowSensitive/Solver.h" |
| #include "clang/Analysis/FlowSensitive/StorageLocation.h" |
| #include "clang/Analysis/FlowSensitive/Value.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/DenseSet.h" |
| #include "llvm/ADT/SetVector.h" |
| #include "llvm/Support/Compiler.h" |
| #include <cassert> |
| #include <memory> |
| #include <optional> |
| #include <type_traits> |
| #include <utility> |
| #include <vector> |
| |
| namespace clang { |
| namespace dataflow { |
| class Logger; |
| |
| /// Skip past nodes that the CFG does not emit. These nodes are invisible to |
| /// flow-sensitive analysis, and should be ignored as they will effectively not |
| /// exist. |
| /// |
| /// * `ParenExpr` - The CFG takes the operator precedence into account, but |
| /// otherwise omits the node afterwards. |
| /// |
| /// * `ExprWithCleanups` - The CFG will generate the appropriate calls to |
| /// destructors and then omit the node. |
| /// |
| const Expr &ignoreCFGOmittedNodes(const Expr &E); |
| const Stmt &ignoreCFGOmittedNodes(const Stmt &S); |
| |
| /// A set of `FieldDecl *`. Use `SmallSetVector` to guarantee deterministic |
| /// iteration order. |
| using FieldSet = llvm::SmallSetVector<const FieldDecl *, 4>; |
| |
| /// Returns the set of all fields in the type. |
| FieldSet getObjectFields(QualType Type); |
| |
| struct ContextSensitiveOptions { |
| /// The maximum depth to analyze. A value of zero is equivalent to disabling |
| /// context-sensitive analysis entirely. |
| unsigned Depth = 2; |
| }; |
| |
| /// Owns objects that encompass the state of a program and stores context that |
| /// is used during dataflow analysis. |
| class DataflowAnalysisContext { |
| public: |
| struct Options { |
| /// Options for analyzing function bodies when present in the translation |
| /// unit, or empty to disable context-sensitive analysis. Note that this is |
| /// fundamentally limited: some constructs, such as recursion, are |
| /// explicitly unsupported. |
| std::optional<ContextSensitiveOptions> ContextSensitiveOpts; |
| |
| /// If provided, analysis details will be recorded here. |
| /// (This is always non-null within an AnalysisContext, the framework |
| /// provides a fallback no-op logger). |
| Logger *Log = nullptr; |
| }; |
| |
| /// Constructs a dataflow analysis context. |
| /// |
| /// Requirements: |
| /// |
| /// `S` must not be null. |
| DataflowAnalysisContext(std::unique_ptr<Solver> S, |
| Options Opts = Options{ |
| /*ContextSensitiveOpts=*/std::nullopt, |
| /*Logger=*/nullptr}); |
| ~DataflowAnalysisContext(); |
| |
| /// Returns a new storage location appropriate for `Type`. |
| /// |
| /// A null `Type` is interpreted as the pointee type of `std::nullptr_t`. |
| StorageLocation &createStorageLocation(QualType Type); |
| |
| /// Returns a stable storage location for `D`. |
| StorageLocation &getStableStorageLocation(const VarDecl &D); |
| |
| /// Returns a stable storage location for `E`. |
| StorageLocation &getStableStorageLocation(const Expr &E); |
| |
| /// Returns a pointer value that represents a null pointer. Calls with |
| /// `PointeeType` that are canonically equivalent will return the same result. |
| /// A null `PointeeType` can be used for the pointee of `std::nullptr_t`. |
| PointerValue &getOrCreateNullPointerValue(QualType PointeeType); |
| |
| /// Adds `Constraint` to the flow condition identified by `Token`. |
| void addFlowConditionConstraint(Atom Token, const Formula &Constraint); |
| |
| /// Creates a new flow condition with the same constraints as the flow |
| /// condition identified by `Token` and returns its token. |
| Atom forkFlowCondition(Atom Token); |
| |
| /// Creates a new flow condition that represents the disjunction of the flow |
| /// conditions identified by `FirstToken` and `SecondToken`, and returns its |
| /// token. |
| Atom joinFlowConditions(Atom FirstToken, Atom SecondToken); |
| |
| /// Returns true if and only if the constraints of the flow condition |
| /// identified by `Token` imply that `Val` is true. |
| bool flowConditionImplies(Atom Token, const Formula &); |
| |
| /// Returns true if and only if the constraints of the flow condition |
| /// identified by `Token` are always true. |
| bool flowConditionIsTautology(Atom Token); |
| |
| /// Returns true if `Val1` is equivalent to `Val2`. |
| /// Note: This function doesn't take into account constraints on `Val1` and |
| /// `Val2` imposed by the flow condition. |
| bool equivalentFormulas(const Formula &Val1, const Formula &Val2); |
| |
| LLVM_DUMP_METHOD void dumpFlowCondition(Atom Token, |
| llvm::raw_ostream &OS = llvm::dbgs()); |
| |
| /// Returns the `ControlFlowContext` registered for `F`, if any. Otherwise, |
| /// returns null. |
| const ControlFlowContext *getControlFlowContext(const FunctionDecl *F); |
| |
| const Options &getOptions() { return Opts; } |
| |
| Arena &arena() { return *A; } |
| |
| /// Returns the outcome of satisfiability checking on `Constraints`. |
| /// |
| /// Flow conditions are not incorporated, so they may need to be manually |
| /// included in `Constraints` to provide contextually-accurate results, e.g. |
| /// if any definitions or relationships of the values in `Constraints` have |
| /// been stored in flow conditions. |
| Solver::Result querySolver(llvm::SetVector<const Formula *> Constraints); |
| |
| /// Returns the fields of `Type`, limited to the set of fields modeled by this |
| /// context. |
| FieldSet getModeledFields(QualType Type); |
| |
| private: |
| friend class Environment; |
| |
| struct NullableQualTypeDenseMapInfo : private llvm::DenseMapInfo<QualType> { |
| static QualType getEmptyKey() { |
| // Allow a NULL `QualType` by using a different value as the empty key. |
| return QualType::getFromOpaquePtr(reinterpret_cast<Type *>(1)); |
| } |
| |
| using DenseMapInfo::getHashValue; |
| using DenseMapInfo::getTombstoneKey; |
| using DenseMapInfo::isEqual; |
| }; |
| |
| // Extends the set of modeled field declarations. |
| void addModeledFields(const FieldSet &Fields); |
| |
| /// Adds all constraints of the flow condition identified by `Token` and all |
| /// of its transitive dependencies to `Constraints`. `VisitedTokens` is used |
| /// to track tokens of flow conditions that were already visited by recursive |
| /// calls. |
| void addTransitiveFlowConditionConstraints( |
| Atom Token, llvm::SetVector<const Formula *> &Constraints, |
| llvm::DenseSet<Atom> &VisitedTokens); |
| |
| /// Returns true if the solver is able to prove that there is no satisfying |
| /// assignment for `Constraints` |
| bool isUnsatisfiable(llvm::SetVector<const Formula *> Constraints) { |
| return querySolver(std::move(Constraints)).getStatus() == |
| Solver::Result::Status::Unsatisfiable; |
| } |
| |
| std::unique_ptr<Solver> S; |
| std::unique_ptr<Arena> A; |
| |
| // Maps from program declarations and statements to storage locations that are |
| // assigned to them. These assignments are global (aggregated across all basic |
| // blocks) and are used to produce stable storage locations when the same |
| // basic blocks are evaluated multiple times. The storage locations that are |
| // in scope for a particular basic block are stored in `Environment`. |
| llvm::DenseMap<const ValueDecl *, StorageLocation *> DeclToLoc; |
| llvm::DenseMap<const Expr *, StorageLocation *> ExprToLoc; |
| |
| // Null pointer values, keyed by the canonical pointee type. |
| // |
| // FIXME: The pointer values are indexed by the pointee types which are |
| // required to initialize the `PointeeLoc` field in `PointerValue`. Consider |
| // creating a type-independent `NullPointerValue` without a `PointeeLoc` |
| // field. |
| llvm::DenseMap<QualType, PointerValue *, NullableQualTypeDenseMapInfo> |
| NullPointerVals; |
| |
| Options Opts; |
| |
| // Flow conditions are tracked symbolically: each unique flow condition is |
| // associated with a fresh symbolic variable (token), bound to the clause that |
| // defines the flow condition. Conceptually, each binding corresponds to an |
| // "iff" of the form `FC <=> (C1 ^ C2 ^ ...)` where `FC` is a flow condition |
| // token (an atomic boolean) and `Ci`s are the set of constraints in the flow |
| // flow condition clause. The set of constraints (C1 ^ C2 ^ ...) are stored in |
| // the `FlowConditionConstraints` map, keyed by the token of the flow |
| // condition. |
| // |
| // Flow conditions depend on other flow conditions if they are created using |
| // `forkFlowCondition` or `joinFlowConditions`. The graph of flow condition |
| // dependencies is stored in the `FlowConditionDeps` map. |
| llvm::DenseMap<Atom, llvm::DenseSet<Atom>> FlowConditionDeps; |
| llvm::DenseMap<Atom, const Formula *> FlowConditionConstraints; |
| |
| llvm::DenseMap<const FunctionDecl *, ControlFlowContext> FunctionContexts; |
| |
| // Fields modeled by environments covered by this context. |
| FieldSet ModeledFields; |
| |
| std::unique_ptr<Logger> LogOwner; // If created via flags. |
| }; |
| |
| } // namespace dataflow |
| } // namespace clang |
| |
| #endif // LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_DATAFLOWANALYSISCONTEXT_H |