StorageLocation.h

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//===-- StorageLocation.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 classes that represent elements of the local variable store
// and of the heap during dataflow analysis.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_STORAGELOCATION_H
#define LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_STORAGELOCATION_H
 
#include "clang/AST/Decl.h"
#include "clang/AST/Type.h"
#include "llvm/ADT/DenseMap.h"
 
namespace clang {
namespace dataflow {
 
/// Base class for elements of the local variable store and of the heap.
///
/// Each storage location holds a value. The mapping from storage locations to
/// values is stored in the environment.
class StorageLocation {
public:
  enum class Kind { Scalar, Aggregate };
 
  StorageLocation(Kind LocKind, QualType Type) : LocKind(LocKind), Type(Type) {}
 
  // Non-copyable because addresses of storage locations are used as their
  // identities throughout framework and user code. The framework is responsible
  // for construction and destruction of storage locations.
  StorageLocation(const StorageLocation &) = delete;
  StorageLocation &operator=(const StorageLocation &) = delete;
 
  virtual ~StorageLocation() = default;
 
  Kind getKind() const { return LocKind; }
 
  QualType getType() const { return Type; }
 
private:
  Kind LocKind;
  QualType Type;
};
 
/// A storage location that is not subdivided further for the purposes of
/// abstract interpretation. For example: `int`, `int*`, `int&`.
class ScalarStorageLocation final : public StorageLocation {
public:
  explicit ScalarStorageLocation(QualType Type)
      : StorageLocation(Kind::Scalar, Type) {}
 
  static bool classof(const StorageLocation *Loc) {
    return Loc->getKind() == Kind::Scalar;
  }
};
 
/// A storage location which is subdivided into smaller storage locations that
/// can be traced independently by abstract interpretation. For example: a
/// struct with public members. The child map is flat, so when used for a struct
/// or class type, all accessible members of base struct and class types are
/// directly accesible as children of this location.
/// FIXME: Currently, the storage location of unions is modelled the same way as
/// that of structs or classes. Eventually, we need to change this modelling so
/// that all of the members of a given union have the same storage location.
class AggregateStorageLocation final : public StorageLocation {
public:
  explicit AggregateStorageLocation(QualType Type)
      : AggregateStorageLocation(
            Type, llvm::DenseMap<const ValueDecl *, StorageLocation *>()) {}
 
  AggregateStorageLocation(
      QualType Type,
      llvm::DenseMap<const ValueDecl *, StorageLocation *> Children)
      : StorageLocation(Kind::Aggregate, Type), Children(std::move(Children)) {}
 
  static bool classof(const StorageLocation *Loc) {
    return Loc->getKind() == Kind::Aggregate;
  }
 
  /// Returns the child storage location for `D`.
  StorageLocation &getChild(const ValueDecl &D) const {
    auto It = Children.find(&D);
    assert(It != Children.end());
    return *It->second;
  }
 
private:
  llvm::DenseMap<const ValueDecl *, StorageLocation *> Children;
};
 
} // namespace dataflow
} // namespace clang
 
#endif // LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_STORAGELOCATION_H