//===- LiveVariables.h - Live Variable Analysis for Source CFGs -*- 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 implements Live Variables analysis for source-level CFGs.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_ANALYSIS_ANALYSES_LIVEVARIABLES_H

#define LLVM_CLANG_ANALYSIS_ANALYSES_LIVEVARIABLES_H

#include "clang/AST/Decl.h"

#include "clang/Analysis/AnalysisDeclContext.h"

#include "llvm/ADT/ImmutableSet.h"

namespace clang {

class CFG;

class CFGBlock;

class Stmt;

class DeclRefExpr;

class SourceManager;

class LiveVariables : public ManagedAnalysis {

public:

  class LivenessValues {

  public:

    llvm::ImmutableSet<const Expr *> liveExprs;

    llvm::ImmutableSet<const VarDecl *> liveDecls;

    llvm::ImmutableSet<const BindingDecl *> liveBindings;

    bool equals(const LivenessValues &V) const;

    LivenessValues()

      : liveExprs(nullptr), liveDecls(nullptr), liveBindings(nullptr) {}

    LivenessValues(llvm::ImmutableSet<const Expr *> liveExprs,

                   llvm::ImmutableSet<const VarDecl *> LiveDecls,

                   llvm::ImmutableSet<const BindingDecl *> LiveBindings)

        : liveExprs(liveExprs), liveDecls(LiveDecls),

          liveBindings(LiveBindings) {}

    bool isLive(const Expr *E) const;

    bool isLive(const VarDecl *D) const;

    friend class LiveVariables;

  };

  class Observer {

    virtual void anchor();

  public:

    virtual ~Observer() {}

    /// A callback invoked right before invoking the

    ///  liveness transfer function on the given statement.

    virtual void observeStmt(const Stmt *S,

                             const CFGBlock *currentBlock,

                             const LivenessValues& V) {}

    /// Called when the live variables analysis registers

    /// that a variable is killed.

    virtual void observerKill(const DeclRefExpr *DR) {}

  };

  ~LiveVariables() override;

  /// Compute the liveness information for a given CFG.

  static std::unique_ptr<LiveVariables>

  computeLiveness(AnalysisDeclContext &analysisContext, bool killAtAssign);

  /// Return true if a variable is live at the end of a

  /// specified block.

  bool isLive(const CFGBlock *B, const VarDecl *D);

  /// Returns true if a variable is live at the beginning of the

  ///  the statement.  This query only works if liveness information

  ///  has been recorded at the statement level (see runOnAllBlocks), and

  ///  only returns liveness information for block-level expressions.

  bool isLive(const Stmt *S, const VarDecl *D);

  /// Returns true the block-level expression value is live

  ///  before the given block-level expression (see runOnAllBlocks).

  bool isLive(const Stmt *Loc, const Expr *Val);

  /// Print to stderr the variable liveness information associated with

  /// each basic block.

  void dumpBlockLiveness(const SourceManager &M);

  /// Print to stderr the expression liveness information associated with

  /// each basic block.

  void dumpExprLiveness(const SourceManager &M);

  void runOnAllBlocks(Observer &obs);

  static std::unique_ptr<LiveVariables>

  create(AnalysisDeclContext &analysisContext) {

    return computeLiveness(analysisContext, true);

  }

  static const void *getTag();

private:

  LiveVariables(void *impl);

  void *impl;

};

class RelaxedLiveVariables : public LiveVariables {

public:

  static std::unique_ptr<LiveVariables>

  create(AnalysisDeclContext &analysisContext) {

    return computeLiveness(analysisContext, false);

  }

  static const void *getTag();

};

} // end namespace clang

#endif