clang/Sema/ScopeInfo.h

//===--- ScopeInfo.h - Information about a semantic context -----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines FunctionScopeInfo and its subclasses, which contain
// information about a single function, block, lambda, or method body.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_SEMA_SCOPE_INFO_H
#define LLVM_CLANG_SEMA_SCOPE_INFO_H

#include "clang/AST/Type.h"
#include "clang/Basic/CapturedStmt.h"
#include "clang/Basic/PartialDiagnostic.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"

namespace clang {

class Decl;
class BlockDecl;
class CapturedDecl;
class CXXMethodDecl;
class ObjCPropertyDecl;
class IdentifierInfo;
class ImplicitParamDecl;
class LabelDecl;
class ReturnStmt;
class Scope;
class SwitchStmt;
class VarDecl;
class DeclRefExpr;
class ObjCIvarRefExpr;
class ObjCPropertyRefExpr;
class ObjCMessageExpr;

namespace sema {

/// \brief Contains information about the compound statement currently being
/// parsed.
class CompoundScopeInfo {
public:
  CompoundScopeInfo()
    : HasEmptyLoopBodies(false) { }

  /// \brief Whether this compound stamement contains `for' or `while' loops
  /// with empty bodies.
  bool HasEmptyLoopBodies;

  void setHasEmptyLoopBodies() {
    HasEmptyLoopBodies = true;
  }
};

class PossiblyUnreachableDiag {
public:
  PartialDiagnostic PD;
  SourceLocation Loc;
  const Stmt *stmt;

  PossiblyUnreachableDiag(const PartialDiagnostic &PD, SourceLocation Loc,
                          const Stmt *stmt)
    : PD(PD), Loc(Loc), stmt(stmt) {}
};

/// \brief Retains information about a function, method, or block that is
/// currently being parsed.
class FunctionScopeInfo {
protected:
  enum ScopeKind {
    SK_Function,
    SK_Block,
    SK_Lambda,
    SK_CapturedRegion
  };

public:
  /// \brief What kind of scope we are describing.
  ///
  ScopeKind Kind;

  /// \brief Whether this function contains a VLA, \@try, try, C++
  /// initializer, or anything else that can't be jumped past.
  bool HasBranchProtectedScope;

  /// \brief Whether this function contains any switches or direct gotos.
  bool HasBranchIntoScope;

  /// \brief Whether this function contains any indirect gotos.
  bool HasIndirectGoto;

  /// \brief Whether a statement was dropped because it was invalid.
  bool HasDroppedStmt;

  /// A flag that is set when parsing a method that must call super's
  /// implementation, such as \c -dealloc, \c -finalize, or any method marked
  /// with \c __attribute__((objc_requires_super)).
  bool ObjCShouldCallSuper;

  /// \brief Used to determine if errors occurred in this function or block.
  DiagnosticErrorTrap ErrorTrap;

  /// SwitchStack - This is the current set of active switch statements in the
  /// block.
  SmallVector<SwitchStmt*, 8> SwitchStack;

  /// \brief The list of return statements that occur within the function or
  /// block, if there is any chance of applying the named return value
  /// optimization, or if we need to infer a return type.
  SmallVector<ReturnStmt*, 4> Returns;

  /// \brief The stack of currently active compound stamement scopes in the
  /// function.
  SmallVector<CompoundScopeInfo, 4> CompoundScopes;

  /// \brief A list of PartialDiagnostics created but delayed within the
  /// current function scope.  These diagnostics are vetted for reachability
  /// prior to being emitted.
  SmallVector<PossiblyUnreachableDiag, 4> PossiblyUnreachableDiags;

public:
  /// Represents a simple identification of a weak object.
  ///
  /// Part of the implementation of -Wrepeated-use-of-weak.
  ///
  /// This is used to determine if two weak accesses refer to the same object.
  /// Here are some examples of how various accesses are "profiled":
  ///
  /// Access Expression |     "Base" Decl     |          "Property" Decl
  /// :---------------: | :-----------------: | :------------------------------:
  /// self.property     | self (VarDecl)      | property (ObjCPropertyDecl)
  /// self.implicitProp | self (VarDecl)      | -implicitProp (ObjCMethodDecl)
  /// self->ivar.prop   | ivar (ObjCIvarDecl) | prop (ObjCPropertyDecl)
  /// cxxObj.obj.prop   | obj (FieldDecl)     | prop (ObjCPropertyDecl)
  /// [self foo].prop   | 0 (unknown)         | prop (ObjCPropertyDecl)
  /// self.prop1.prop2  | prop1 (ObjCPropertyDecl)    | prop2 (ObjCPropertyDecl)
  /// MyClass.prop      | MyClass (ObjCInterfaceDecl) | -prop (ObjCMethodDecl)
  /// weakVar           | 0 (known)           | weakVar (VarDecl)
  /// self->weakIvar    | self (VarDecl)      | weakIvar (ObjCIvarDecl)
  ///
  /// Objects are identified with only two Decls to make it reasonably fast to
  /// compare them.
  class WeakObjectProfileTy {
    /// The base object decl, as described in the class documentation.
    ///
    /// The extra flag is "true" if the Base and Property are enough to uniquely
    /// identify the object in memory.
    ///
    /// \sa isExactProfile()
    typedef llvm::PointerIntPair<const NamedDecl *, 1, bool> BaseInfoTy;
    BaseInfoTy Base;

    /// The "property" decl, as described in the class documentation.
    ///
    /// Note that this may not actually be an ObjCPropertyDecl, e.g. in the
    /// case of "implicit" properties (regular methods accessed via dot syntax).
    const NamedDecl *Property;

    /// Used to find the proper base profile for a given base expression.
    static BaseInfoTy getBaseInfo(const Expr *BaseE);

    // For use in DenseMap.
    friend class DenseMapInfo;
    inline WeakObjectProfileTy();
    static inline WeakObjectProfileTy getSentinel();

  public:
    WeakObjectProfileTy(const ObjCPropertyRefExpr *RE);
    WeakObjectProfileTy(const Expr *Base, const ObjCPropertyDecl *Property);
    WeakObjectProfileTy(const DeclRefExpr *RE);
    WeakObjectProfileTy(const ObjCIvarRefExpr *RE);

    const NamedDecl *getBase() const { return Base.getPointer(); }
    const NamedDecl *getProperty() const { return Property; }

    /// Returns true if the object base specifies a known object in memory,
    /// rather than, say, an instance variable or property of another object.
    ///
    /// Note that this ignores the effects of aliasing; that is, \c foo.bar is
    /// considered an exact profile if \c foo is a local variable, even if
    /// another variable \c foo2 refers to the same object as \c foo.
    ///
    /// For increased precision, accesses with base variables that are
    /// properties or ivars of 'self' (e.g. self.prop1.prop2) are considered to
    /// be exact, though this is not true for arbitrary variables
    /// (foo.prop1.prop2).
    bool isExactProfile() const {
      return Base.getInt();
    }

    bool operator==(const WeakObjectProfileTy &Other) const {
      return Base == Other.Base && Property == Other.Property;
    }

    // For use in DenseMap.
    // We can't specialize the usual llvm::DenseMapInfo at the end of the file
    // because by that point the DenseMap in FunctionScopeInfo has already been
    // instantiated.
    class DenseMapInfo {
    public:
      static inline WeakObjectProfileTy getEmptyKey() {
        return WeakObjectProfileTy();
      }
      static inline WeakObjectProfileTy getTombstoneKey() {
        return WeakObjectProfileTy::getSentinel();
      }

      static unsigned getHashValue(const WeakObjectProfileTy &Val) {
        typedef std::pair<BaseInfoTy, const NamedDecl *> Pair;
        return llvm::DenseMapInfo<Pair>::getHashValue(Pair(Val.Base,
                                                           Val.Property));
      }

      static bool isEqual(const WeakObjectProfileTy &LHS,
                          const WeakObjectProfileTy &RHS) {
        return LHS == RHS;
      }
    };
  };

  /// Represents a single use of a weak object.
  ///
  /// Stores both the expression and whether the access is potentially unsafe
  /// (i.e. it could potentially be warned about).
  ///
  /// Part of the implementation of -Wrepeated-use-of-weak.
  class WeakUseTy {
    llvm::PointerIntPair<const Expr *, 1, bool> Rep;
  public:
    WeakUseTy(const Expr *Use, bool IsRead) : Rep(Use, IsRead) {}

    const Expr *getUseExpr() const { return Rep.getPointer(); }
    bool isUnsafe() const { return Rep.getInt(); }
    void markSafe() { Rep.setInt(false); }

    bool operator==(const WeakUseTy &Other) const {
      return Rep == Other.Rep;
    }
  };

  /// Used to collect uses of a particular weak object in a function body.
  ///
  /// Part of the implementation of -Wrepeated-use-of-weak.
  typedef SmallVector<WeakUseTy, 4> WeakUseVector;

  /// Used to collect all uses of weak objects in a function body.
  ///
  /// Part of the implementation of -Wrepeated-use-of-weak.
  typedef llvm::SmallDenseMap<WeakObjectProfileTy, WeakUseVector, 8,
                              WeakObjectProfileTy::DenseMapInfo>
          WeakObjectUseMap;

private:
  /// Used to collect all uses of weak objects in this function body.
  ///
  /// Part of the implementation of -Wrepeated-use-of-weak.
  WeakObjectUseMap WeakObjectUses;

public:
  /// Record that a weak object was accessed.
  ///
  /// Part of the implementation of -Wrepeated-use-of-weak.
  template <typename ExprT>
  inline void recordUseOfWeak(const ExprT *E, bool IsRead = true);

  void recordUseOfWeak(const ObjCMessageExpr *Msg,
                       const ObjCPropertyDecl *Prop);

  /// Record that a given expression is a "safe" access of a weak object (e.g.
  /// assigning it to a strong variable.)
  ///
  /// Part of the implementation of -Wrepeated-use-of-weak.
  void markSafeWeakUse(const Expr *E);

  const WeakObjectUseMap &getWeakObjectUses() const {
    return WeakObjectUses;
  }

  void setHasBranchIntoScope() {
    HasBranchIntoScope = true;
  }

  void setHasBranchProtectedScope() {
    HasBranchProtectedScope = true;
  }

  void setHasIndirectGoto() {
    HasIndirectGoto = true;
  }

  void setHasDroppedStmt() {
    HasDroppedStmt = true;
  }

  bool NeedsScopeChecking() const {
    return !HasDroppedStmt &&
        (HasIndirectGoto ||
          (HasBranchProtectedScope && HasBranchIntoScope));
  }

  FunctionScopeInfo(DiagnosticsEngine &Diag)
    : Kind(SK_Function),
      HasBranchProtectedScope(false),
      HasBranchIntoScope(false),
      HasIndirectGoto(false),
      HasDroppedStmt(false),
      ObjCShouldCallSuper(false),
      ErrorTrap(Diag) { }

  virtual ~FunctionScopeInfo();

  /// \brief Clear out the information in this function scope, making it
  /// suitable for reuse.
  void Clear();
};

class CapturingScopeInfo : public FunctionScopeInfo {
public:
  enum ImplicitCaptureStyle {
    ImpCap_None, ImpCap_LambdaByval, ImpCap_LambdaByref, ImpCap_Block,
    ImpCap_CapturedRegion
  };

  ImplicitCaptureStyle ImpCaptureStyle;

  class Capture {
    // There are two categories of capture: capturing 'this', and capturing
    // local variables.  There are three ways to capture a local variable:
    // capture by copy in the C++11 sense, capture by reference
    // in the C++11 sense, and __block capture.  Lambdas explicitly specify
    // capture by copy or capture by reference.  For blocks, __block capture
    // applies to variables with that annotation, variables of reference type
    // are captured by reference, and other variables are captured by copy.
    enum CaptureKind {
      Cap_This, Cap_ByCopy, Cap_ByRef, Cap_Block
    };

    // The variable being captured (if we are not capturing 'this'),
    // and misc bits descibing the capture.
    llvm::PointerIntPair<VarDecl*, 2, CaptureKind> VarAndKind;

    // Expression to initialize a field of the given type, and whether this
    // is a nested capture; the expression is only required if we are
    // capturing ByVal and the variable's type has a non-trivial
    // copy constructor.
    llvm::PointerIntPair<Expr*, 1, bool> CopyExprAndNested;

    /// \brief The source location at which the first capture occurred..
    SourceLocation Loc;

    /// \brief The location of the ellipsis that expands a parameter pack.
    SourceLocation EllipsisLoc;

    /// \brief The type as it was captured, which is in effect the type of the
    /// non-static data member that would hold the capture.
    QualType CaptureType;

  public:
    Capture(VarDecl *Var, bool block, bool byRef, bool isNested,
            SourceLocation Loc, SourceLocation EllipsisLoc,
            QualType CaptureType, Expr *Cpy)
      : VarAndKind(Var, block ? Cap_Block : byRef ? Cap_ByRef : Cap_ByCopy),
        CopyExprAndNested(Cpy, isNested), Loc(Loc), EllipsisLoc(EllipsisLoc),
        CaptureType(CaptureType){}

    enum IsThisCapture { ThisCapture };
    Capture(IsThisCapture, bool isNested, SourceLocation Loc,
            QualType CaptureType, Expr *Cpy)
      : VarAndKind(0, Cap_This), CopyExprAndNested(Cpy, isNested), Loc(Loc),
        EllipsisLoc(), CaptureType(CaptureType) { }

    bool isThisCapture() const { return VarAndKind.getInt() == Cap_This; }
    bool isVariableCapture() const { return !isThisCapture(); }
    bool isCopyCapture() const { return VarAndKind.getInt() == Cap_ByCopy; }
    bool isReferenceCapture() const { return VarAndKind.getInt() == Cap_ByRef; }
    bool isBlockCapture() const { return VarAndKind.getInt() == Cap_Block; }
    bool isNested() { return CopyExprAndNested.getInt(); }

    VarDecl *getVariable() const {
      return VarAndKind.getPointer();
    }

    /// \brief Retrieve the location at which this variable was captured.
    SourceLocation getLocation() const { return Loc; }

    /// \brief Retrieve the source location of the ellipsis, whose presence
    /// indicates that the capture is a pack expansion.
    SourceLocation getEllipsisLoc() const { return EllipsisLoc; }

    /// \brief Retrieve the capture type for this capture, which is effectively
    /// the type of the non-static data member in the lambda/block structure
    /// that would store this capture.
    QualType getCaptureType() const { return CaptureType; }

    Expr *getCopyExpr() const {
      return CopyExprAndNested.getPointer();
    }
  };

  CapturingScopeInfo(DiagnosticsEngine &Diag, ImplicitCaptureStyle Style)
    : FunctionScopeInfo(Diag), ImpCaptureStyle(Style), CXXThisCaptureIndex(0),
      HasImplicitReturnType(false)
     {}

  /// CaptureMap - A map of captured variables to (index+1) into Captures.
  llvm::DenseMap<VarDecl*, unsigned> CaptureMap;

  /// CXXThisCaptureIndex - The (index+1) of the capture of 'this';
  /// zero if 'this' is not captured.
  unsigned CXXThisCaptureIndex;

  /// Captures - The captures.
  SmallVector<Capture, 4> Captures;

  /// \brief - Whether the target type of return statements in this context
  /// is deduced (e.g. a lambda or block with omitted return type).
  bool HasImplicitReturnType;

  /// ReturnType - The target type of return statements in this context,
  /// or null if unknown.
  QualType ReturnType;

  void addCapture(VarDecl *Var, bool isBlock, bool isByref, bool isNested,
                  SourceLocation Loc, SourceLocation EllipsisLoc,
                  QualType CaptureType, Expr *Cpy) {
    Captures.push_back(Capture(Var, isBlock, isByref, isNested, Loc,
                               EllipsisLoc, CaptureType, Cpy));
    CaptureMap[Var] = Captures.size();
  }

  void addThisCapture(bool isNested, SourceLocation Loc, QualType CaptureType,
                      Expr *Cpy);

  /// \brief Determine whether the C++ 'this' is captured.
  bool isCXXThisCaptured() const { return CXXThisCaptureIndex != 0; }

  /// \brief Retrieve the capture of C++ 'this', if it has been captured.
  Capture &getCXXThisCapture() {
    assert(isCXXThisCaptured() && "this has not been captured");
    return Captures[CXXThisCaptureIndex - 1];
  }

  /// \brief Determine whether the given variable has been captured.
  bool isCaptured(VarDecl *Var) const {
    return CaptureMap.count(Var);
  }

  /// \brief Retrieve the capture of the given variable, if it has been
  /// captured already.
  Capture &getCapture(VarDecl *Var) {
    assert(isCaptured(Var) && "Variable has not been captured");
    return Captures[CaptureMap[Var] - 1];
  }

  const Capture &getCapture(VarDecl *Var) const {
    llvm::DenseMap<VarDecl*, unsigned>::const_iterator Known
      = CaptureMap.find(Var);
    assert(Known != CaptureMap.end() && "Variable has not been captured");
    return Captures[Known->second - 1];
  }

  static bool classof(const FunctionScopeInfo *FSI) {
    return FSI->Kind == SK_Block || FSI->Kind == SK_Lambda
                                 || FSI->Kind == SK_CapturedRegion;
  }
};

/// \brief Retains information about a block that is currently being parsed.
class BlockScopeInfo : public CapturingScopeInfo {
public:
  BlockDecl *TheDecl;

  /// TheScope - This is the scope for the block itself, which contains
  /// arguments etc.
  Scope *TheScope;

  /// BlockType - The function type of the block, if one was given.
  /// Its return type may be BuiltinType::Dependent.
  QualType FunctionType;

  BlockScopeInfo(DiagnosticsEngine &Diag, Scope *BlockScope, BlockDecl *Block)
    : CapturingScopeInfo(Diag, ImpCap_Block), TheDecl(Block),
      TheScope(BlockScope)
  {
    Kind = SK_Block;
  }

  virtual ~BlockScopeInfo();

  static bool classof(const FunctionScopeInfo *FSI) {
    return FSI->Kind == SK_Block;
  }
};

/// \brief Retains information about a captured region.
class CapturedRegionScopeInfo: public CapturingScopeInfo {
public:
  /// \brief The CapturedDecl for this statement.
  CapturedDecl *TheCapturedDecl;
  /// \brief The captured record type.
  RecordDecl *TheRecordDecl;
  /// \brief This is the enclosing scope of the captured region.
  Scope *TheScope;
  /// \brief The implicit parameter for the captured variables.
  ImplicitParamDecl *ContextParam;
  /// \brief The kind of captured region.
  CapturedRegionKind CapRegionKind;

  CapturedRegionScopeInfo(DiagnosticsEngine &Diag, Scope *S, CapturedDecl *CD,
                          RecordDecl *RD, ImplicitParamDecl *Context,
                          CapturedRegionKind K)
    : CapturingScopeInfo(Diag, ImpCap_CapturedRegion),
      TheCapturedDecl(CD), TheRecordDecl(RD), TheScope(S),
      ContextParam(Context), CapRegionKind(K)
  {
    Kind = SK_CapturedRegion;
  }

  virtual ~CapturedRegionScopeInfo();

  /// \brief A descriptive name for the kind of captured region this is.
  StringRef getRegionName() const {
    switch (CapRegionKind) {
    case CR_Default:
      return "default captured statement";
    }
    llvm_unreachable("Invalid captured region kind!");
  }

  static bool classof(const FunctionScopeInfo *FSI) {
    return FSI->Kind == SK_CapturedRegion;
  }
};

class LambdaScopeInfo : public CapturingScopeInfo {
public:
  /// \brief The class that describes the lambda.
  CXXRecordDecl *Lambda;

  /// \brief The class that describes the lambda.
  CXXMethodDecl *CallOperator;

  /// \brief Source range covering the lambda introducer [...].
  SourceRange IntroducerRange;

  /// \brief The number of captures in the \c Captures list that are
  /// explicit captures.
  unsigned NumExplicitCaptures;

  /// \brief Whether this is a mutable lambda.
  bool Mutable;

  /// \brief Whether the (empty) parameter list is explicit.
  bool ExplicitParams;

  /// \brief Whether any of the capture expressions requires cleanups.
  bool ExprNeedsCleanups;

  /// \brief Whether the lambda contains an unexpanded parameter pack.
  bool ContainsUnexpandedParameterPack;

  /// \brief Variables used to index into by-copy array captures.
  SmallVector<VarDecl *, 4> ArrayIndexVars;

  /// \brief Offsets into the ArrayIndexVars array at which each capture starts
  /// its list of array index variables.
  SmallVector<unsigned, 4> ArrayIndexStarts;

  LambdaScopeInfo(DiagnosticsEngine &Diag, CXXRecordDecl *Lambda,
                  CXXMethodDecl *CallOperator)
    : CapturingScopeInfo(Diag, ImpCap_None), Lambda(Lambda),
      CallOperator(CallOperator), NumExplicitCaptures(0), Mutable(false),
      ExprNeedsCleanups(false), ContainsUnexpandedParameterPack(false)
  {
    Kind = SK_Lambda;
  }

  virtual ~LambdaScopeInfo();

  /// \brief Note when
  void finishedExplicitCaptures() {
    NumExplicitCaptures = Captures.size();
  }

  static bool classof(const FunctionScopeInfo *FSI) {
    return FSI->Kind == SK_Lambda;
  }
};


FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy()
  : Base(0, false), Property(0) {}

FunctionScopeInfo::WeakObjectProfileTy
FunctionScopeInfo::WeakObjectProfileTy::getSentinel() {
  FunctionScopeInfo::WeakObjectProfileTy Result;
  Result.Base.setInt(true);
  return Result;
}

template <typename ExprT>
void FunctionScopeInfo::recordUseOfWeak(const ExprT *E, bool IsRead) {
  assert(E);
  WeakUseVector &Uses = WeakObjectUses[WeakObjectProfileTy(E)];
  Uses.push_back(WeakUseTy(E, IsRead));
}

inline void
CapturingScopeInfo::addThisCapture(bool isNested, SourceLocation Loc,
                                   QualType CaptureType, Expr *Cpy) {
  Captures.push_back(Capture(Capture::ThisCapture, isNested, Loc, CaptureType,
                             Cpy));
  CXXThisCaptureIndex = Captures.size();

  if (LambdaScopeInfo *LSI = dyn_cast<LambdaScopeInfo>(this))
    LSI->ArrayIndexStarts.push_back(LSI->ArrayIndexVars.size());
}

} // end namespace sema
} // end namespace clang

#endif