ExecutorBreadcrumb.h

//===--- ExecutorBreadcrumb.h - executor hop tracking for SILGen ----------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#ifndef SWIFT_SILGEN_EXECUTORBREADCRUMB_H
#define SWIFT_SILGEN_EXECUTORBREADCRUMB_H

#include "swift/SIL/SILValue.h"

namespace swift {

class SILLocation;

namespace Lowering {

class SILGenFunction;

/// Represents the information necessary to return to a caller's own
/// active executor after making a hop to an actor for actor-isolated calls.
class ExecutorBreadcrumb {
  bool mustReturnToExecutor;
  
public:
  // An empty breadcrumb, indicating no hop back is necessary.
  ExecutorBreadcrumb() : mustReturnToExecutor(false) {}
  
  // A breadcrumb representing the need to hop back to the expected
  // executor of the current function.
  explicit ExecutorBreadcrumb(bool mustReturnToExecutor)
    : mustReturnToExecutor(mustReturnToExecutor) {}
  
  // Emits the hop back sequence, if any, necessary to get back to
  // the executor represented by this breadcrumb.
  void emit(SILGenFunction &SGF, SILLocation loc);

#ifndef NDEBUG
  // FOR ASSERTS ONLY: returns true if calling `emit` will emit a hop-back.
  bool needsEmit() const { return mustReturnToExecutor; }
#endif
};

} // namespace Lowering
} // namespace swift

#endif