include/swift/AST/CaptureInfo.h

//===--- CaptureInfo.h - Data Structure for Capture Lists -------*- C++ -*-===//
//
// 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_AST_CAPTURE_INFO_H
#define SWIFT_AST_CAPTURE_INFO_H

#include "swift/Basic/Debug.h"
#include "swift/Basic/LLVM.h"
#include "swift/Basic/OptionSet.h"
#include "swift/Basic/SourceLoc.h"
#include "swift/AST/TypeAlignments.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/Support/TrailingObjects.h"

namespace swift {
class CapturedValue;
}

namespace llvm {
class raw_ostream;
template <> struct DenseMapInfo<swift::CapturedValue>;
}

namespace swift {
class ValueDecl;
class FuncDecl;
class OpaqueValueExpr;

/// CapturedValue includes both the declaration being captured, along with flags
/// that indicate how it is captured.
class CapturedValue {
public:
  using Storage =
      llvm::PointerIntPair<llvm::PointerUnion<ValueDecl*, OpaqueValueExpr*>, 2,
                           unsigned>;

private:
  Storage Value;
  SourceLoc Loc;

  explicit CapturedValue(Storage V, SourceLoc Loc) : Value(V), Loc(Loc) {}

public:
  friend struct llvm::DenseMapInfo<CapturedValue>;

  enum {
    /// IsDirect is set when a VarDecl with storage *and* accessors is captured
    /// by its storage address.  This happens in the accessors for the VarDecl.
    IsDirect = 1 << 0,

    /// IsNoEscape is set when a vardecl is captured by a noescape closure, and
    /// thus has its lifetime guaranteed.  It can be closed over by a fixed
    /// address if it has storage.
    IsNoEscape = 1 << 1
  };

  CapturedValue(ValueDecl *Val, unsigned Flags, SourceLoc Loc)
      : Value(Val, Flags), Loc(Loc) {}

  CapturedValue(OpaqueValueExpr *Val, unsigned Flags)
      : Value(Val, Flags), Loc(SourceLoc()) {}

  static CapturedValue getDynamicSelfMetadata() {
    return CapturedValue((ValueDecl *)nullptr, 0, SourceLoc());
  }

  bool isDirect() const { return Value.getInt() & IsDirect; }
  bool isNoEscape() const { return Value.getInt() & IsNoEscape; }

  bool isDynamicSelfMetadata() const { return !Value.getPointer(); }
  bool isOpaqueValue() const {
    return Value.getPointer().is<OpaqueValueExpr *>();
  }

  CapturedValue mergeFlags(CapturedValue cv) {
    assert(Value.getPointer() == cv.Value.getPointer() &&
           "merging flags on two different value decls");
    return CapturedValue(
        Storage(Value.getPointer(), getFlags() & cv.getFlags()),
        Loc);
  }

  ValueDecl *getDecl() const {
    assert(Value.getPointer() && "dynamic Self metadata capture does not "
           "have a value");
    return Value.getPointer().dyn_cast<ValueDecl *>();
  }

  OpaqueValueExpr *getOpaqueValue() const {
    assert(Value.getPointer() && "dynamic Self metadata capture does not "
           "have a value");
    return Value.getPointer().dyn_cast<OpaqueValueExpr *>();
  }

  SourceLoc getLoc() const { return Loc; }

  unsigned getFlags() const { return Value.getInt(); }
};

} // end swift namespace

namespace swift {

class DynamicSelfType;

/// Stores information about captured variables.
class CaptureInfo {
  class CaptureInfoStorage final
      : public llvm::TrailingObjects<CaptureInfoStorage, CapturedValue> {

    DynamicSelfType *DynamicSelf;
    OpaqueValueExpr *OpaqueValue;
    unsigned Count;
  public:
    explicit CaptureInfoStorage(unsigned count, DynamicSelfType *dynamicSelf,
                                OpaqueValueExpr *opaqueValue)
      : DynamicSelf(dynamicSelf), OpaqueValue(opaqueValue), Count(count) { }

    ArrayRef<CapturedValue> getCaptures() const {
      return llvm::makeArrayRef(this->getTrailingObjects<CapturedValue>(),
                                Count);
    }

    DynamicSelfType *getDynamicSelfType() const {
      return DynamicSelf;
    }

    OpaqueValueExpr *getOpaqueValue() const {
      return OpaqueValue;
    }
  };

  enum class Flags : unsigned {
    HasGenericParamCaptures = 1 << 0
  };

  llvm::PointerIntPair<const CaptureInfoStorage *, 2, OptionSet<Flags>>
      StorageAndFlags;

public:
  /// The default-constructed CaptureInfo is "not yet computed".
  CaptureInfo() = default;
  CaptureInfo(ASTContext &ctx, ArrayRef<CapturedValue> captures,
              DynamicSelfType *dynamicSelf, OpaqueValueExpr *opaqueValue,
              bool genericParamCaptures);

  /// A CaptureInfo representing no captures at all.
  static CaptureInfo empty();

  bool hasBeenComputed() const {
    return StorageAndFlags.getPointer();
  }

  bool isTrivial() const {
    return getCaptures().empty() && !hasGenericParamCaptures() &&
           !hasDynamicSelfCapture() && !hasOpaqueValueCapture();
  }

  ArrayRef<CapturedValue> getCaptures() const {
    // FIXME: Ideally, everywhere that synthesizes a function should include
    // its capture info.
    if (!hasBeenComputed())
      return None;
    return StorageAndFlags.getPointer()->getCaptures();
  }

  /// Return a filtered list of the captures for this function,
  /// filtering out global variables.  This function returns the list that
  /// actually needs to be closed over.
  ///
  void getLocalCaptures(SmallVectorImpl<CapturedValue> &Result) const;

  /// \returns true if getLocalCaptures() will return a non-empty list.
  bool hasLocalCaptures() const;

  /// \returns true if the function captures any generic type parameters.
  bool hasGenericParamCaptures() const {
    // FIXME: Ideally, everywhere that synthesizes a function should include
    // its capture info.
    if (!hasBeenComputed())
      return false;
    return StorageAndFlags.getInt().contains(Flags::HasGenericParamCaptures);
  }

  /// \returns true if the function captures the dynamic Self type.
  bool hasDynamicSelfCapture() const {
    return getDynamicSelfType() != nullptr;
  }

  /// \returns the captured dynamic Self type, if any.
  DynamicSelfType *getDynamicSelfType() const {
    // FIXME: Ideally, everywhere that synthesizes a function should include
    // its capture info.
    if (!hasBeenComputed())
      return nullptr;
    return StorageAndFlags.getPointer()->getDynamicSelfType();
  }

  bool hasOpaqueValueCapture() const {
    return getOpaqueValue() != nullptr;
  }

  OpaqueValueExpr *getOpaqueValue() const {
    // FIXME: Ideally, everywhere that synthesizes a function should include
    // its capture info.
    if (!hasBeenComputed())
      return nullptr;
    return StorageAndFlags.getPointer()->getOpaqueValue();
  }

  SWIFT_DEBUG_DUMP;
  void print(raw_ostream &OS) const;
};

} // namespace swift

#endif // LLVM_SWIFT_AST_CAPTURE_INFO_H