| //===- DataflowAnalysis.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 base types and functions for building dataflow analyses |
| // that run over Control-Flow Graphs (CFGs). |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_DATAFLOWANALYSIS_H |
| #define LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_DATAFLOWANALYSIS_H |
| |
| #include <iterator> |
| #include <utility> |
| #include <vector> |
| |
| #include "clang/AST/ASTContext.h" |
| #include "clang/AST/Stmt.h" |
| #include "clang/Analysis/CFG.h" |
| #include "clang/Analysis/FlowSensitive/ControlFlowContext.h" |
| #include "clang/Analysis/FlowSensitive/DataflowEnvironment.h" |
| #include "clang/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.h" |
| #include "llvm/ADT/Any.h" |
| #include "llvm/ADT/Optional.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/Support/Error.h" |
| |
| namespace clang { |
| namespace dataflow { |
| |
| /// Base class template for dataflow analyses built on a single lattice type. |
| /// |
| /// Requirements: |
| /// |
| /// `Derived` must be derived from a specialization of this class template and |
| /// must provide the following public members: |
| /// * `LatticeT initialElement()` - returns a lattice element that models the |
| /// initial state of a basic block; |
| /// * `void transfer(const Stmt *, LatticeT &, Environment &)` - applies the |
| /// analysis transfer function for a given statement and lattice element. |
| /// |
| /// `Derived` can optionally override the following members: |
| /// * `bool merge(QualType, const Value &, const Value &, Value &, |
| /// Environment &)` - joins distinct values. This could be a strict |
| /// lattice join or a more general widening operation. |
| /// |
| /// `LatticeT` is a bounded join-semilattice that is used by `Derived` and must |
| /// provide the following public members: |
| /// * `LatticeJoinEffect join(const LatticeT &)` - joins the object and the |
| /// argument by computing their least upper bound, modifies the object if |
| /// necessary, and returns an effect indicating whether any changes were |
| /// made to it; |
| /// * `bool operator==(const LatticeT &) const` - returns true if and only if |
| /// the object is equal to the argument. |
| template <typename Derived, typename LatticeT> |
| class DataflowAnalysis : public TypeErasedDataflowAnalysis { |
| public: |
| /// Bounded join-semilattice that is used in the analysis. |
| using Lattice = LatticeT; |
| |
| explicit DataflowAnalysis(ASTContext &Context) : Context(Context) {} |
| |
| /// Deprecated. Use the `DataflowAnalysisOptions` constructor instead. |
| explicit DataflowAnalysis(ASTContext &Context, bool ApplyBuiltinTransfer) |
| : TypeErasedDataflowAnalysis(ApplyBuiltinTransfer), Context(Context) {} |
| |
| explicit DataflowAnalysis(ASTContext &Context, |
| DataflowAnalysisOptions Options) |
| : TypeErasedDataflowAnalysis(Options), Context(Context) {} |
| |
| ASTContext &getASTContext() final { return Context; } |
| |
| TypeErasedLattice typeErasedInitialElement() final { |
| return {static_cast<Derived *>(this)->initialElement()}; |
| } |
| |
| LatticeJoinEffect joinTypeErased(TypeErasedLattice &E1, |
| const TypeErasedLattice &E2) final { |
| Lattice &L1 = llvm::any_cast<Lattice &>(E1.Value); |
| const Lattice &L2 = llvm::any_cast<const Lattice &>(E2.Value); |
| return L1.join(L2); |
| } |
| |
| bool isEqualTypeErased(const TypeErasedLattice &E1, |
| const TypeErasedLattice &E2) final { |
| const Lattice &L1 = llvm::any_cast<const Lattice &>(E1.Value); |
| const Lattice &L2 = llvm::any_cast<const Lattice &>(E2.Value); |
| return L1 == L2; |
| } |
| |
| void transferTypeErased(const Stmt *Stmt, TypeErasedLattice &E, |
| Environment &Env) final { |
| Lattice &L = llvm::any_cast<Lattice &>(E.Value); |
| static_cast<Derived *>(this)->transfer(Stmt, L, Env); |
| } |
| |
| private: |
| ASTContext &Context; |
| }; |
| |
| // Model of the program at a given program point. |
| template <typename LatticeT> struct DataflowAnalysisState { |
| // Model of a program property. |
| LatticeT Lattice; |
| |
| // Model of the state of the program (store and heap). |
| Environment Env; |
| }; |
| |
| /// Performs dataflow analysis and returns a mapping from basic block IDs to |
| /// dataflow analysis states that model the respective basic blocks. The |
| /// returned vector, if any, will have the same size as the number of CFG |
| /// blocks, with indices corresponding to basic block IDs. Returns an error if |
| /// the dataflow analysis cannot be performed successfully. Otherwise, calls |
| /// `PostVisitStmt` on each statement with the final analysis results at that |
| /// program point. |
| template <typename AnalysisT> |
| llvm::Expected<std::vector< |
| llvm::Optional<DataflowAnalysisState<typename AnalysisT::Lattice>>>> |
| runDataflowAnalysis( |
| const ControlFlowContext &CFCtx, AnalysisT &Analysis, |
| const Environment &InitEnv, |
| std::function<void(const Stmt *, const DataflowAnalysisState< |
| typename AnalysisT::Lattice> &)> |
| PostVisitStmt = nullptr) { |
| std::function<void(const Stmt *, const TypeErasedDataflowAnalysisState &)> |
| PostVisitStmtClosure = nullptr; |
| if (PostVisitStmt != nullptr) { |
| PostVisitStmtClosure = [&PostVisitStmt]( |
| const Stmt *Stmt, |
| const TypeErasedDataflowAnalysisState &State) { |
| auto *Lattice = |
| llvm::any_cast<typename AnalysisT::Lattice>(&State.Lattice.Value); |
| PostVisitStmt(Stmt, DataflowAnalysisState<typename AnalysisT::Lattice>{ |
| *Lattice, State.Env}); |
| }; |
| } |
| |
| auto TypeErasedBlockStates = runTypeErasedDataflowAnalysis( |
| CFCtx, Analysis, InitEnv, PostVisitStmtClosure); |
| if (!TypeErasedBlockStates) |
| return TypeErasedBlockStates.takeError(); |
| |
| std::vector< |
| llvm::Optional<DataflowAnalysisState<typename AnalysisT::Lattice>>> |
| BlockStates; |
| BlockStates.reserve(TypeErasedBlockStates->size()); |
| |
| llvm::transform(std::move(*TypeErasedBlockStates), |
| std::back_inserter(BlockStates), [](auto &OptState) { |
| return std::move(OptState).map([](auto &&State) { |
| return DataflowAnalysisState<typename AnalysisT::Lattice>{ |
| llvm::any_cast<typename AnalysisT::Lattice>( |
| std::move(State.Lattice.Value)), |
| std::move(State.Env)}; |
| }); |
| }); |
| return BlockStates; |
| } |
| |
| /// Abstract base class for dataflow "models": reusable analysis components that |
| /// model a particular aspect of program semantics in the `Environment`. For |
| /// example, a model may capture a type and its related functions. |
| class DataflowModel : public Environment::ValueModel { |
| public: |
| /// Return value indicates whether the model processed the `Stmt`. |
| virtual bool transfer(const Stmt *Stmt, Environment &Env) = 0; |
| }; |
| |
| } // namespace dataflow |
| } // namespace clang |
| |
| #endif // LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_DATAFLOWANALYSIS_H |