lib/SILGen/ManagedValue.h - third_party/swift - Git at Google

 //===--- ManagedValue.h - Exploded RValue Representation --------*- 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
 //
 //===----------------------------------------------------------------------===//
 //
 // A storage structure for holding a destructured rvalue with an optional
 // cleanup(s).
 // Ownership of the rvalue can be "forwarded" to disable the associated
 // cleanup(s).
 //
 //===----------------------------------------------------------------------===//

 #ifndef SWIFT_LOWERING_MANAGEDVALUE_H
 #define SWIFT_LOWERING_MANAGEDVALUE_H

 #include "Cleanup.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "swift/SIL/Consumption.h"
 #include "swift/SIL/SILValue.h"

 namespace swift {

 enum class CastConsumptionKind : unsigned char;

 namespace Lowering {

 class Initialization;
 class SILGenFunction;

 /// ManagedValue - represents a singular SIL value and an optional cleanup.
 /// Ownership of the ManagedValue can be "forwarded" to disable its cleanup when
 /// the rvalue is consumed. A ManagedValue can also represent an LValue used as
 /// a value, such as an inout function argument, and can be null.
 ///
 /// Interesting relevant cases include:
 ///   LValue: the SILValue will always have an isAddress() SILType. LValues
 ///           never have an associated cleanup.
 ///   RValue, isAddress() type: an address-only RValue.
 ///   RValue, !isAddress() type: a loadable RValue.
 ///   "InContext": Represented with the lvalue flag set but with no SILValue,
 ///                this represents a value that was emitted directly into an
 ///                initialization stored by an SGFContext.
 ///
 /// The RValue cases may or may not have a cleanup associated with the value.  A
 /// cleanup is associated with +1 values of non-trivial type and +0 values of
 /// non-trivial type.
 ///
 class ManagedValue {
   /// The value (or address of an address-only value) being managed, and
   /// whether it represents an lvalue.  InContext is represented with the lvalue
   /// flag set but with a null SILValue.
   llvm::PointerIntPair<SILValue, 1, bool> valueAndFlag;

   /// A handle to the cleanup that destroys this value, or
   /// CleanupHandle::invalid() if the value has no cleanup.
   CleanupHandle cleanup;

   explicit ManagedValue(SILValue value, bool isLValue, CleanupHandle cleanup)
     : valueAndFlag(value, isLValue), cleanup(cleanup) {
   }

 public:

   ManagedValue() = default;

   /// Create a managed value for a +1 rvalue.
   ///
   /// Please do not introduce new uses of this method! Instead use one of the
   /// static constructors below.
   ManagedValue(SILValue value, CleanupHandle cleanup)
     : valueAndFlag(value, false), cleanup(cleanup) {
     assert(value && "No value specified?!");
     assert((!getType().isObject() ||
             value.getOwnershipKind() != ValueOwnershipKind::Trivial ||
             !hasCleanup()) &&
            "Objects with trivial ownership should never have a cleanup");
   }

   /// Create a managed value for a +0 rvalue.
   ///
   /// Please do not introduce new uses of this method! Instead use one of the
   /// static constructors below!
   static ManagedValue forUnmanaged(SILValue value) {
     assert(value && "No value specified");
     return ManagedValue(value, false, CleanupHandle::invalid());
   }

   /// Create a managed value for a +1 rvalue object.
   static ManagedValue forOwnedObjectRValue(SILValue value,
                                            CleanupHandle cleanup) {
     assert(value && "No value specified");
     assert(value->getType().isObject() &&
            "Expected borrowed rvalues to be objects");
     assert(value.getOwnershipKind() != ValueOwnershipKind::Trivial);
     return ManagedValue(value, false, cleanup);
   }

   /// Create a managed value for a +1 rvalue address.
   ///
   /// From a high level perspective, this consists of a temporary buffer.
   static ManagedValue forOwnedAddressRValue(SILValue value,
                                             CleanupHandle cleanup) {
     assert(value && "No value specified");
     assert(value->getType().isAddress() && "Expected value to be an address");
     assert(value.getOwnershipKind() == ValueOwnershipKind::Trivial &&
            "Addresses always have trivial ownership");
     return ManagedValue(value, false, cleanup);
   }

   /// Create a managed value for a +1 non-trivial rvalue.
   static ManagedValue forOwnedRValue(SILValue value, CleanupHandle cleanup) {
     if (value->getType().isAddress())
       return ManagedValue::forOwnedAddressRValue(value, cleanup);
     return ManagedValue::forOwnedObjectRValue(value, cleanup);
   }

   /// Create a managed value for a +0 borrowed non-trivial rvalue object.
   static ManagedValue
   forBorrowedObjectRValue(SILValue value) {
     assert(value && "No value specified");
     assert(value->getType().isObject() &&
            "Expected borrowed rvalues to be objects");
     assert(value.getOwnershipKind() != ValueOwnershipKind::Trivial);
     return ManagedValue(value, false, CleanupHandle::invalid());
   }

   /// Create a managed value for a +0 borrowed non-trivial rvalue address.
   static ManagedValue
   forBorrowedAddressRValue(SILValue value) {
     assert(value && "No value specified");
     assert(value->getType().isAddress() && "Expected value to be an address");
     assert(value.getOwnershipKind() == ValueOwnershipKind::Trivial &&
            "Addresses always have trivial ownership");
     return ManagedValue(value, false, CleanupHandle::invalid());
   }

   /// Create a managed value for a +0 guaranteed rvalue.
   static ManagedValue
   forBorrowedRValue(SILValue value) {
     if (value->getType().isAddress())
       return ManagedValue::forBorrowedAddressRValue(value);
     return ManagedValue::forBorrowedObjectRValue(value);
   }

   /// Create a managed value for a +0 trivial object rvalue.
   static ManagedValue forTrivialObjectRValue(SILValue value) {
     assert(value->getType().isObject() && "Expected an object");
     assert(value.getOwnershipKind() == ValueOwnershipKind::Trivial);
     return ManagedValue(value, false, CleanupHandle::invalid());
   }

   /// Create a managed value for a +0 trivial address rvalue.
   static ManagedValue forTrivialAddressRValue(SILValue value) {
     assert(value->getType().isAddress() && "Expected an address");
     assert(value.getOwnershipKind() == ValueOwnershipKind::Trivial);
     return ManagedValue(value, false, CleanupHandle::invalid());
   }

   /// Create a managed value for a +0 trivial rvalue.
   static ManagedValue forTrivialRValue(SILValue value) {
     if (value->getType().isObject())
       return ManagedValue::forTrivialObjectRValue(value);
     return ManagedValue::forTrivialAddressRValue(value);
   }

   /// Create a managed value for an l-value.
   static ManagedValue forLValue(SILValue value) {
     assert(value && "No value specified");
     assert(value->getType().isAddress() &&
            "lvalues always have isAddress() type");
     return ManagedValue(value, true, CleanupHandle::invalid());
   }

   /// Create a managed value that indicates that the value you're looking for
   /// got stored into an initialization specified by an SGFContext, instead of
   /// being represented by this ManagedValue.
   static ManagedValue forInContext() {
     return ManagedValue(SILValue(), true, CleanupHandle::invalid());
   }

   bool isLValue() const {
     return valueAndFlag.getInt() && valueAndFlag.getPointer();
   }
   bool isInContext() const {
     return valueAndFlag.getInt() && !valueAndFlag.getPointer();
   }

   /// Return true if this is an +0 rvalue, or has trivial type.
   bool isPlusZeroRValueOrTrivial() const {
     // If this is an lvalue or isInContext() then it is not an RValue.
     if (isLValue() || isInContext()) return false;

     // If this has a cleanup attached, then it is +1 rvalue.  If not, it is
     // either +0 or trivial (in which case +0 vs +1 doesn't matter).
     return !hasCleanup();
   }

   SILValue getLValueAddress() const {
     assert(isLValue() && "This isn't an lvalue");
     return getValue();
   }

   SILValue getUnmanagedValue() const {
     assert(!hasCleanup());
     return getValue();
   }
   SILValue getValue() const { return valueAndFlag.getPointer(); }

   SILType getType() const { return getValue()->getType(); }

   ValueOwnershipKind getOwnershipKind() const {
     return getValue().getOwnershipKind();
   }

   /// Transform the given ManagedValue, replacing the underlying value, but
   /// keeping the same cleanup.
   ///
   /// For owned values, this is equivalent to forwarding the cleanup and
   /// creating a new cleanup of the same type on the new value. This is useful
   /// for forwarding sequences.
   ///
   /// For all other values, it is a move.
   ManagedValue transform(SILValue newValue) && {
     assert(getValue().getOwnershipKind() == newValue.getOwnershipKind() &&
            "New value and old value must have the same ownership kind");
     ManagedValue M(newValue, isLValue(), getCleanup());
     *this = ManagedValue();
     return M;
   }

   /// Emit a copy of this value with independent ownership.
   ManagedValue copy(SILGenFunction &SGF, SILLocation loc) const;

   /// Emit a copy of this value with independent ownership into the current
   /// formal evaluation scope.
   ManagedValue formalAccessCopy(SILGenFunction &SGF, SILLocation loc);

   /// Store a copy of this value with independent ownership into the given
   /// uninitialized address.
   void copyInto(SILGenFunction &SGF, SILValue dest, SILLocation loc);

   /// This is the same operation as 'copy', but works on +0 values that don't
   /// have cleanups.  It returns a +1 value with one.
   ManagedValue copyUnmanaged(SILGenFunction &SGF, SILLocation loc);

   /// This is the same operation as 'formalAccessCopy', but works on +0 values
   /// that don't have cleanups.  It returns a +1 value with one.
   ManagedValue formalAccessCopyUnmanaged(SILGenFunction &SGF, SILLocation loc);

   bool hasCleanup() const { return cleanup.isValid(); }
   CleanupHandle getCleanup() const { return cleanup; }

   /// Return a "borrowed" version of this value.
   ///
   /// An l-value is borrowed as itself.  A +1 r-value is borrowed as a
   /// +0 r-value, with the assumption that the original ManagedValue
   /// will not be forwarded until the borrowed value is fully used.
   ManagedValue borrow(SILGenFunction &SGF, SILLocation loc) const;

   /// Return a formally evaluated "borrowed" version of this value.
   ManagedValue formalAccessBorrow(SILGenFunction &SGF, SILLocation loc) const;

   ManagedValue unmanagedBorrow() const {
     return isLValue() ? *this : ManagedValue::forUnmanaged(getValue());
   }

   /// If this managed value is a plus one value, return *this. If this is a plus
   /// zero value, return a copy instead.
   ManagedValue ensurePlusOne(SILGenFunction &SGF, SILLocation loc) const;

   /// Given a scalar value, materialize it into memory with the
   /// exact same level of cleanup it had before.
   ManagedValue materialize(SILGenFunction &SGF, SILLocation loc) const;

   /// Disable the cleanup for this value.
   void forwardCleanup(SILGenFunction &SGF) const;

   /// Forward this value, deactivating the cleanup and returning the
   /// underlying value.
   SILValue forward(SILGenFunction &SGF) const;

   /// Forward this value into memory by storing it to the given address.
   ///
   /// \param SGF - The SILGenFunction.
   /// \param loc - the AST location to associate with emitted instructions.
   /// \param address - the address to assign to.
   void forwardInto(SILGenFunction &SGF, SILLocation loc, SILValue address);

   /// Forward this value into the given initialization.
   ///
   /// \param SGF - The SILGenFunction.
   /// \param loc - the AST location to associate with emitted instructions.
   /// \param dest - the destination to forward into
   void forwardInto(SILGenFunction &SGF, SILLocation loc, Initialization *dest);

   /// Assign this value into memory, destroying the existing
   /// value at the destination address.
   ///
   /// \param SGF - The SILGenFunction.
   /// \param loc - the AST location to associate with emitted instructions.
   /// \param address - the address to assign to.
   void assignInto(SILGenFunction &SGF, SILLocation loc, SILValue address);

   explicit operator bool() const {
     // "InContext" is not considered false.
     return bool(getValue()) || valueAndFlag.getInt();
   }

   void dump() const;
   void dump(raw_ostream &os, unsigned indent = 0) const;
   void print(raw_ostream &os) const;
 };

 /// A ManagedValue which may not be intended to be consumed.
 ///
 /// The invariant is that the cleanup on a ManagedValue that's not
 /// meant to be consumed should be free to clear.
 ///
 /// Code which gets a ManagedValue from a ConsumableManagedValue
 /// must be careful before handing the MV off to an API.  Many
 /// SILGen APIs expect that an MV is +1, but ConsumableManagedValue
 /// often traffics in borrowed values.  A value is only +1 if
 /// the associated consumption is TakeAlways, but conditional
 /// operation should turn TakeOnSuccess consumptions into TakeAlways
 /// consumptions on their success path.
 class ConsumableManagedValue {
   ManagedValue Value;
   CastConsumptionKind FinalConsumption;

 public:
   /// Create an invalid CMV.
   ConsumableManagedValue() = default;

   /// Create a CMV with a specific value and consumption rule.
   /*implicit*/ ConsumableManagedValue(ManagedValue value,
                                       CastConsumptionKind finalConsumption)
     : Value(value), FinalConsumption(finalConsumption) {}

   /// Create a CMV for a value of trivial type.
   static ConsumableManagedValue forUnmanaged(SILValue value) {
     return { ManagedValue::forUnmanaged(value),
              CastConsumptionKind::TakeAlways };
   }

   /// Create a CMV for an owned value.
   static ConsumableManagedValue forOwned(ManagedValue value) {
     return { value, CastConsumptionKind::TakeAlways };
   }

   /// Has this been filled in with meaningful data?
   bool isValid() const { return (bool) Value; }

   bool isOwned() const {
     assert(isValid());
     return FinalConsumption == CastConsumptionKind::TakeAlways;
   }

   /// Return true if there's a cleanup associated with this value.
   bool hasCleanup() const { return Value.hasCleanup(); }
   CleanupHandle getCleanup() const { return Value.getCleanup(); }

   SILType getType() const { return Value.getType(); }
   SILValue getValue() const { return Value.getValue(); }
   ValueOwnershipKind getOwnershipKind() const {
     return Value.getOwnershipKind();
   }

   /// Return a managed value appropriate for the final use of this CMV.
   ManagedValue getFinalManagedValue() const { return Value; }

   /// Get the value as an unmanaged ManagedValue.
   ///
   /// You probably should not be using this; it's here to make it easy
   /// to find code that is probably wrong.
   ManagedValue asUnmanagedValue() const {
     return ManagedValue::forUnmanaged(Value.getValue());
   }

   /// Return the consumption rules appropriate for the final use of
   /// this CMV.
   CastConsumptionKind getFinalConsumption() const { return FinalConsumption; }

   /// Return a managed value that's appropriate for borrowing this
   /// value and promising not to consume it.
   ConsumableManagedValue asBorrowedOperand() const {
     return { asUnmanagedValue(), CastConsumptionKind::CopyOnSuccess };
   }

   /// Return a managed value that's appropriate for copying this value and
   /// always consuming it.
   ConsumableManagedValue copy(SILGenFunction &SGF, SILLocation loc) const {
     return ConsumableManagedValue::forOwned(asUnmanagedValue().copy(SGF, loc));
   }
 };

 } // namespace Lowering
 } // namespace swift

 namespace swift {

 template <typename To> inline bool isa(const Lowering::ManagedValue &M) {
   return isa<To>(M.getValue());
 }

 } // end namespace swift

 #endif
	//===--- ManagedValue.h - Exploded RValue Representation --------- 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
	//
	//===----------------------------------------------------------------------===//
	//
	// A storage structure for holding a destructured rvalue with an optional
	// cleanup(s).
	// Ownership of the rvalue can be "forwarded" to disable the associated
	// cleanup(s).
	//
	//===----------------------------------------------------------------------===//

	#ifndef SWIFT_LOWERING_MANAGEDVALUE_H
	#define SWIFT_LOWERING_MANAGEDVALUE_H

	#include "Cleanup.h"
	#include "llvm/ADT/PointerIntPair.h"
	#include "swift/SIL/Consumption.h"
	#include "swift/SIL/SILValue.h"

	namespace swift {

	enum class CastConsumptionKind : unsigned char;

	namespace Lowering {

	class Initialization;
	class SILGenFunction;

	/// ManagedValue - represents a singular SIL value and an optional cleanup.
	/// Ownership of the ManagedValue can be "forwarded" to disable its cleanup when
	/// the rvalue is consumed. A ManagedValue can also represent an LValue used as
	/// a value, such as an inout function argument, and can be null.
	///
	/// Interesting relevant cases include:
	/// LValue: the SILValue will always have an isAddress() SILType. LValues
	/// never have an associated cleanup.
	/// RValue, isAddress() type: an address-only RValue.
	/// RValue, !isAddress() type: a loadable RValue.
	/// "InContext": Represented with the lvalue flag set but with no SILValue,
	/// this represents a value that was emitted directly into an
	/// initialization stored by an SGFContext.
	///
	/// The RValue cases may or may not have a cleanup associated with the value. A
	/// cleanup is associated with +1 values of non-trivial type and +0 values of
	/// non-trivial type.
	///
	class ManagedValue {
	/// The value (or address of an address-only value) being managed, and
	/// whether it represents an lvalue. InContext is represented with the lvalue
	/// flag set but with a null SILValue.
	llvm::PointerIntPair<SILValue, 1, bool> valueAndFlag;

	/// A handle to the cleanup that destroys this value, or
	/// CleanupHandle::invalid() if the value has no cleanup.
	CleanupHandle cleanup;

	explicit ManagedValue(SILValue value, bool isLValue, CleanupHandle cleanup)
	: valueAndFlag(value, isLValue), cleanup(cleanup) {
	}

	public:

	ManagedValue() = default;

	/// Create a managed value for a +1 rvalue.
	///
	/// Please do not introduce new uses of this method! Instead use one of the
	/// static constructors below.
	ManagedValue(SILValue value, CleanupHandle cleanup)
	: valueAndFlag(value, false), cleanup(cleanup) {
	assert(value && "No value specified?!");
	assert((!getType().isObject() \|\|
	value.getOwnershipKind() != ValueOwnershipKind::Trivial \|\|
	!hasCleanup()) &&
	"Objects with trivial ownership should never have a cleanup");
	}

	/// Create a managed value for a +0 rvalue.
	///
	/// Please do not introduce new uses of this method! Instead use one of the
	/// static constructors below!
	static ManagedValue forUnmanaged(SILValue value) {
	assert(value && "No value specified");
	return ManagedValue(value, false, CleanupHandle::invalid());
	}

	/// Create a managed value for a +1 rvalue object.
	static ManagedValue forOwnedObjectRValue(SILValue value,
	CleanupHandle cleanup) {
	assert(value && "No value specified");
	assert(value->getType().isObject() &&
	"Expected borrowed rvalues to be objects");
	assert(value.getOwnershipKind() != ValueOwnershipKind::Trivial);
	return ManagedValue(value, false, cleanup);
	}

	/// Create a managed value for a +1 rvalue address.
	///
	/// From a high level perspective, this consists of a temporary buffer.
	static ManagedValue forOwnedAddressRValue(SILValue value,
	CleanupHandle cleanup) {
	assert(value && "No value specified");
	assert(value->getType().isAddress() && "Expected value to be an address");
	assert(value.getOwnershipKind() == ValueOwnershipKind::Trivial &&
	"Addresses always have trivial ownership");
	return ManagedValue(value, false, cleanup);
	}

	/// Create a managed value for a +1 non-trivial rvalue.
	static ManagedValue forOwnedRValue(SILValue value, CleanupHandle cleanup) {
	if (value->getType().isAddress())
	return ManagedValue::forOwnedAddressRValue(value, cleanup);
	return ManagedValue::forOwnedObjectRValue(value, cleanup);
	}

	/// Create a managed value for a +0 borrowed non-trivial rvalue object.
	static ManagedValue
	forBorrowedObjectRValue(SILValue value) {
	assert(value && "No value specified");
	assert(value->getType().isObject() &&
	"Expected borrowed rvalues to be objects");
	assert(value.getOwnershipKind() != ValueOwnershipKind::Trivial);
	return ManagedValue(value, false, CleanupHandle::invalid());
	}

	/// Create a managed value for a +0 borrowed non-trivial rvalue address.
	static ManagedValue
	forBorrowedAddressRValue(SILValue value) {
	assert(value && "No value specified");
	assert(value->getType().isAddress() && "Expected value to be an address");
	assert(value.getOwnershipKind() == ValueOwnershipKind::Trivial &&
	"Addresses always have trivial ownership");
	return ManagedValue(value, false, CleanupHandle::invalid());
	}

	/// Create a managed value for a +0 guaranteed rvalue.
	static ManagedValue
	forBorrowedRValue(SILValue value) {
	if (value->getType().isAddress())
	return ManagedValue::forBorrowedAddressRValue(value);
	return ManagedValue::forBorrowedObjectRValue(value);
	}

	/// Create a managed value for a +0 trivial object rvalue.
	static ManagedValue forTrivialObjectRValue(SILValue value) {
	assert(value->getType().isObject() && "Expected an object");
	assert(value.getOwnershipKind() == ValueOwnershipKind::Trivial);
	return ManagedValue(value, false, CleanupHandle::invalid());
	}

	/// Create a managed value for a +0 trivial address rvalue.
	static ManagedValue forTrivialAddressRValue(SILValue value) {
	assert(value->getType().isAddress() && "Expected an address");
	assert(value.getOwnershipKind() == ValueOwnershipKind::Trivial);
	return ManagedValue(value, false, CleanupHandle::invalid());
	}

	/// Create a managed value for a +0 trivial rvalue.
	static ManagedValue forTrivialRValue(SILValue value) {
	if (value->getType().isObject())
	return ManagedValue::forTrivialObjectRValue(value);
	return ManagedValue::forTrivialAddressRValue(value);
	}

	/// Create a managed value for an l-value.
	static ManagedValue forLValue(SILValue value) {
	assert(value && "No value specified");
	assert(value->getType().isAddress() &&
	"lvalues always have isAddress() type");
	return ManagedValue(value, true, CleanupHandle::invalid());
	}

	/// Create a managed value that indicates that the value you're looking for
	/// got stored into an initialization specified by an SGFContext, instead of
	/// being represented by this ManagedValue.
	static ManagedValue forInContext() {
	return ManagedValue(SILValue(), true, CleanupHandle::invalid());
	}

	bool isLValue() const {
	return valueAndFlag.getInt() && valueAndFlag.getPointer();
	}
	bool isInContext() const {
	return valueAndFlag.getInt() && !valueAndFlag.getPointer();
	}

	/// Return true if this is an +0 rvalue, or has trivial type.
	bool isPlusZeroRValueOrTrivial() const {
	// If this is an lvalue or isInContext() then it is not an RValue.
	if (isLValue() \|\| isInContext()) return false;

	// If this has a cleanup attached, then it is +1 rvalue. If not, it is
	// either +0 or trivial (in which case +0 vs +1 doesn't matter).
	return !hasCleanup();
	}

	SILValue getLValueAddress() const {
	assert(isLValue() && "This isn't an lvalue");
	return getValue();
	}

	SILValue getUnmanagedValue() const {
	assert(!hasCleanup());
	return getValue();
	}
	SILValue getValue() const { return valueAndFlag.getPointer(); }

	SILType getType() const { return getValue()->getType(); }

	ValueOwnershipKind getOwnershipKind() const {
	return getValue().getOwnershipKind();
	}

	/// Transform the given ManagedValue, replacing the underlying value, but
	/// keeping the same cleanup.
	///
	/// For owned values, this is equivalent to forwarding the cleanup and
	/// creating a new cleanup of the same type on the new value. This is useful
	/// for forwarding sequences.
	///
	/// For all other values, it is a move.
	ManagedValue transform(SILValue newValue) && {
	assert(getValue().getOwnershipKind() == newValue.getOwnershipKind() &&
	"New value and old value must have the same ownership kind");
	ManagedValue M(newValue, isLValue(), getCleanup());
	*this = ManagedValue();
	return M;
	}

	/// Emit a copy of this value with independent ownership.
	ManagedValue copy(SILGenFunction &SGF, SILLocation loc) const;

	/// Emit a copy of this value with independent ownership into the current
	/// formal evaluation scope.
	ManagedValue formalAccessCopy(SILGenFunction &SGF, SILLocation loc);

	/// Store a copy of this value with independent ownership into the given
	/// uninitialized address.
	void copyInto(SILGenFunction &SGF, SILValue dest, SILLocation loc);

	/// This is the same operation as 'copy', but works on +0 values that don't
	/// have cleanups. It returns a +1 value with one.
	ManagedValue copyUnmanaged(SILGenFunction &SGF, SILLocation loc);

	/// This is the same operation as 'formalAccessCopy', but works on +0 values
	/// that don't have cleanups. It returns a +1 value with one.
	ManagedValue formalAccessCopyUnmanaged(SILGenFunction &SGF, SILLocation loc);

	bool hasCleanup() const { return cleanup.isValid(); }
	CleanupHandle getCleanup() const { return cleanup; }

	/// Return a "borrowed" version of this value.
	///
	/// An l-value is borrowed as itself. A +1 r-value is borrowed as a
	/// +0 r-value, with the assumption that the original ManagedValue
	/// will not be forwarded until the borrowed value is fully used.
	ManagedValue borrow(SILGenFunction &SGF, SILLocation loc) const;

	/// Return a formally evaluated "borrowed" version of this value.
	ManagedValue formalAccessBorrow(SILGenFunction &SGF, SILLocation loc) const;

	ManagedValue unmanagedBorrow() const {
	return isLValue() ? *this : ManagedValue::forUnmanaged(getValue());
	}

	/// If this managed value is a plus one value, return *this. If this is a plus
	/// zero value, return a copy instead.
	ManagedValue ensurePlusOne(SILGenFunction &SGF, SILLocation loc) const;

	/// Given a scalar value, materialize it into memory with the
	/// exact same level of cleanup it had before.
	ManagedValue materialize(SILGenFunction &SGF, SILLocation loc) const;

	/// Disable the cleanup for this value.
	void forwardCleanup(SILGenFunction &SGF) const;

	/// Forward this value, deactivating the cleanup and returning the
	/// underlying value.
	SILValue forward(SILGenFunction &SGF) const;

	/// Forward this value into memory by storing it to the given address.
	///
	/// \param SGF - The SILGenFunction.
	/// \param loc - the AST location to associate with emitted instructions.
	/// \param address - the address to assign to.
	void forwardInto(SILGenFunction &SGF, SILLocation loc, SILValue address);

	/// Forward this value into the given initialization.
	///
	/// \param SGF - The SILGenFunction.
	/// \param loc - the AST location to associate with emitted instructions.
	/// \param dest - the destination to forward into
	void forwardInto(SILGenFunction &SGF, SILLocation loc, Initialization *dest);

	/// Assign this value into memory, destroying the existing
	/// value at the destination address.
	///
	/// \param SGF - The SILGenFunction.
	/// \param loc - the AST location to associate with emitted instructions.
	/// \param address - the address to assign to.
	void assignInto(SILGenFunction &SGF, SILLocation loc, SILValue address);

	explicit operator bool() const {
	// "InContext" is not considered false.
	return bool(getValue()) \|\| valueAndFlag.getInt();
	}

	void dump() const;
	void dump(raw_ostream &os, unsigned indent = 0) const;
	void print(raw_ostream &os) const;
	};

	/// A ManagedValue which may not be intended to be consumed.
	///
	/// The invariant is that the cleanup on a ManagedValue that's not
	/// meant to be consumed should be free to clear.
	///
	/// Code which gets a ManagedValue from a ConsumableManagedValue
	/// must be careful before handing the MV off to an API. Many
	/// SILGen APIs expect that an MV is +1, but ConsumableManagedValue
	/// often traffics in borrowed values. A value is only +1 if
	/// the associated consumption is TakeAlways, but conditional
	/// operation should turn TakeOnSuccess consumptions into TakeAlways
	/// consumptions on their success path.
	class ConsumableManagedValue {
	ManagedValue Value;
	CastConsumptionKind FinalConsumption;

	public:
	/// Create an invalid CMV.
	ConsumableManagedValue() = default;

	/// Create a CMV with a specific value and consumption rule.
	/implicit/ ConsumableManagedValue(ManagedValue value,
	CastConsumptionKind finalConsumption)
	: Value(value), FinalConsumption(finalConsumption) {}

	/// Create a CMV for a value of trivial type.
	static ConsumableManagedValue forUnmanaged(SILValue value) {
	return { ManagedValue::forUnmanaged(value),
	CastConsumptionKind::TakeAlways };
	}

	/// Create a CMV for an owned value.
	static ConsumableManagedValue forOwned(ManagedValue value) {
	return { value, CastConsumptionKind::TakeAlways };
	}

	/// Has this been filled in with meaningful data?
	bool isValid() const { return (bool) Value; }

	bool isOwned() const {
	assert(isValid());
	return FinalConsumption == CastConsumptionKind::TakeAlways;
	}

	/// Return true if there's a cleanup associated with this value.
	bool hasCleanup() const { return Value.hasCleanup(); }
	CleanupHandle getCleanup() const { return Value.getCleanup(); }

	SILType getType() const { return Value.getType(); }
	SILValue getValue() const { return Value.getValue(); }
	ValueOwnershipKind getOwnershipKind() const {
	return Value.getOwnershipKind();
	}

	/// Return a managed value appropriate for the final use of this CMV.
	ManagedValue getFinalManagedValue() const { return Value; }

	/// Get the value as an unmanaged ManagedValue.
	///
	/// You probably should not be using this; it's here to make it easy
	/// to find code that is probably wrong.
	ManagedValue asUnmanagedValue() const {
	return ManagedValue::forUnmanaged(Value.getValue());
	}

	/// Return the consumption rules appropriate for the final use of
	/// this CMV.
	CastConsumptionKind getFinalConsumption() const { return FinalConsumption; }

	/// Return a managed value that's appropriate for borrowing this
	/// value and promising not to consume it.
	ConsumableManagedValue asBorrowedOperand() const {
	return { asUnmanagedValue(), CastConsumptionKind::CopyOnSuccess };
	}

	/// Return a managed value that's appropriate for copying this value and
	/// always consuming it.
	ConsumableManagedValue copy(SILGenFunction &SGF, SILLocation loc) const {
	return ConsumableManagedValue::forOwned(asUnmanagedValue().copy(SGF, loc));
	}
	};

	} // namespace Lowering
	} // namespace swift

	namespace swift {

	template <typename To> inline bool isa(const Lowering::ManagedValue &M) {
	return isa<To>(M.getValue());
	}

	} // end namespace swift

	#endif