lib/SILGen/Cleanup.cpp - third_party/swift - Git at Google

 //===--- Cleanup.cpp - Implements the Cleanup mechanics -------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//

 #include "Cleanup.h"
 #include "ManagedValue.h"
 #include "RValue.h"
 #include "Scope.h"
 #include "SILGenBuilder.h"
 #include "SILGenFunction.h"

 using namespace swift;
 using namespace Lowering;

 //===----------------------------------------------------------------------===//
 //                                CleanupState
 //===----------------------------------------------------------------------===//

 llvm::raw_ostream &Lowering::operator<<(llvm::raw_ostream &os,
                                         CleanupState state) {
   switch (state) {
   case CleanupState::Dormant:
     return os << "Dormant";
   case CleanupState::Dead:
     return os << "Dead";
   case CleanupState::Active:
     return os << "Active";
   case CleanupState::PersistentlyActive:
     return os << "PersistentlyActive";
   }

   llvm_unreachable("Unhandled CleanupState in switch.");
 }

 //===----------------------------------------------------------------------===//
 //                               CleanupManager
 //===----------------------------------------------------------------------===//

 /// Are there any active cleanups in the given range?
 static bool hasAnyActiveCleanups(DiverseStackImpl<Cleanup>::iterator begin,
                                  DiverseStackImpl<Cleanup>::iterator end) {
   for (; begin != end; ++begin)
     if (begin->isActive())
       return true;
   return false;
 }

 void CleanupManager::popTopDeadCleanups() {
   auto end = (innermostScope ? innermostScope->depth : stack.stable_end());
   assert(end.isValid());
   stack.checkIterator(end);

   while (stack.stable_begin() != end && stack.begin()->isDead()) {
     assert(!stack.empty());
     stack.pop();
     stack.checkIterator(end);
   }
 }

 using CleanupBuffer = DiverseValueBuffer<Cleanup>;

 void CleanupManager::popAndEmitCleanup(CleanupHandle handle,
                                        CleanupLocation loc,
                                        ForUnwind_t forUnwind) {
   auto iter = stack.find(handle);
   Cleanup &stackCleanup = *iter;

   // Copy the cleanup off the cleanup stack.
   CleanupBuffer buffer(stackCleanup);
   Cleanup &cleanup = buffer.getCopy();

   // Deactivate it.
   forwardCleanup(handle);

   // Emit the cleanup.
   cleanup.emit(SGF, loc, forUnwind);
 }

 void CleanupManager::emitCleanups(CleanupsDepth depth, CleanupLocation loc,
                                   ForUnwind_t forUnwind, bool popCleanups) {
   auto cur = stack.stable_begin();
 #ifndef NDEBUG
   auto topOfStack = cur;
 #endif
   while (cur != depth) {
     // Advance the iterator.
     auto cleanupHandle = cur;
     auto iter = stack.find(cleanupHandle);
     Cleanup &stackCleanup = *iter;
     cur = stack.stabilize(++iter);

     // Copy the cleanup off the stack if it needs to be emitted.
     // This is necessary both because we might need to pop the cleanup and
     // because the cleanup might push other cleanups that will invalidate
     // references onto the stack.
     Optional<CleanupBuffer> copiedCleanup;
     if (stackCleanup.isActive() && SGF.B.hasValidInsertionPoint()) {
       copiedCleanup.emplace(stackCleanup);
     }

     // Pop now if that was requested.
     if (popCleanups) {
 #ifndef NDEBUG
       // This is an implicit deactivation.
       if (stackCleanup.isActive()) {
         SGF.FormalEvalContext.checkCleanupDeactivation(cleanupHandle);
       }
 #endif

       stack.pop();

 #ifndef NDEBUG
       topOfStack = stack.stable_begin();
 #endif
     }

     // Emit the cleanup.
     if (copiedCleanup) {
       copiedCleanup->getCopy().emit(SGF, loc, forUnwind);
 #ifndef NDEBUG
       if (hasAnyActiveCleanups(stack.stable_begin(), topOfStack)) {
         copiedCleanup->getCopy().dump(SGF);
         llvm_unreachable("cleanup left active cleanups on stack");
       }
 #endif
     }

     stack.checkIterator(cur);
   }
 }

 /// Leave a scope, emitting all the cleanups that are currently active.
 void CleanupManager::endScope(CleanupsDepth depth, CleanupLocation loc) {
   emitCleanups(depth, loc, NotForUnwind, /*popCleanups*/ true);
 }

 bool CleanupManager::hasAnyActiveCleanups(CleanupsDepth from,
                                           CleanupsDepth to) {
   return ::hasAnyActiveCleanups(stack.find(from), stack.find(to));
 }

 bool CleanupManager::hasAnyActiveCleanups(CleanupsDepth from) {
   return ::hasAnyActiveCleanups(stack.begin(), stack.find(from));
 }

 /// emitBranchAndCleanups - Emit a branch to the given jump destination,
 /// threading out through any cleanups we might need to run.  This does not
 /// pop the cleanup stack.
 void CleanupManager::emitBranchAndCleanups(JumpDest dest, SILLocation branchLoc,
                                            ArrayRef<SILValue> args,
                                            ForUnwind_t forUnwind) {
   SILGenBuilder &builder = SGF.getBuilder();
   assert(builder.hasValidInsertionPoint() && "Emitting branch in invalid spot");
   emitCleanups(dest.getDepth(), dest.getCleanupLocation(),
                forUnwind, /*popCleanups=*/false);
   builder.createBranch(branchLoc, dest.getBlock(), args);
 }

 void CleanupManager::emitCleanupsForReturn(CleanupLocation loc,
                                            ForUnwind_t forUnwind) {
   SILGenBuilder &builder = SGF.getBuilder();
   assert(builder.hasValidInsertionPoint() && "Emitting return in invalid spot");
   (void)builder;
   emitCleanups(stack.stable_end(), loc, forUnwind, /*popCleanups=*/false);
 }

 /// Emit a new block that jumps to the specified location and runs necessary
 /// cleanups based on its level. Emit a block even if there are no cleanups;
 /// this is usually the destination of a conditional branch, so jumping
 /// straight to `dest` creates a critical edge.
 SILBasicBlock *CleanupManager::emitBlockForCleanups(JumpDest dest,
                                                     SILLocation branchLoc,
                                                     ArrayRef<SILValue> args,
                                                     ForUnwind_t forUnwind) {
   // Otherwise, create and emit a new block.
   auto *newBlock = SGF.createBasicBlock();
   SILGenSavedInsertionPoint IPRAII(SGF, newBlock);
   emitBranchAndCleanups(dest, branchLoc, args, forUnwind);
   return newBlock;
 }


 Cleanup &CleanupManager::initCleanup(Cleanup &cleanup,
                                      size_t allocSize,
                                      CleanupState state) {
   cleanup.allocatedSize = allocSize;
   cleanup.state = state;
   return cleanup;
 }

 #ifndef NDEBUG
 static void checkCleanupDeactivation(SILGenFunction &SGF,
                                      CleanupsDepth handle,
                                      CleanupState state) {
   if (state != CleanupState::Dead) return;
   SGF.FormalEvalContext.checkCleanupDeactivation(handle);
 }
 #endif

 void CleanupManager::setCleanupState(CleanupsDepth depth, CleanupState state) {
   auto iter = stack.find(depth);
   assert(iter != stack.end() && "can't change end of cleanups stack");
   setCleanupState(*iter, state);

 #ifndef NDEBUG
   // This must be done after setting the state because setting the state can
   // itself finish a formal evaluation in some cases.
   checkCleanupDeactivation(SGF, depth, state);
 #endif

   if (state == CleanupState::Dead && iter == stack.begin())
     popTopDeadCleanups();
 }

 void CleanupManager::forwardCleanup(CleanupsDepth handle) {
   auto iter = stack.find(handle);
   assert(iter != stack.end() && "can't change end of cleanups stack");
   Cleanup &cleanup = *iter;
   assert(cleanup.isActive() && "forwarding inactive or dead cleanup?");

   CleanupState newState = (cleanup.getState() == CleanupState::Active
                              ? CleanupState::Dead
                              : CleanupState::Dormant);
   setCleanupState(cleanup, newState);

 #ifndef NDEBUG
   // This must be done after setting the state because setting the state can
   // itself finish a formal evaluation in some cases.
   checkCleanupDeactivation(SGF, handle, newState);
 #endif

   if (newState == CleanupState::Dead && iter == stack.begin())
     popTopDeadCleanups();
 }

 void CleanupManager::setCleanupState(Cleanup &cleanup, CleanupState state) {
   assert(SGF.B.hasValidInsertionPoint() &&
          "changing cleanup state at invalid IP");

   // Do the transition now to avoid doing it in N places below.
   CleanupState oldState = cleanup.getState();
   (void)oldState;
   cleanup.setState(SGF, state);

   assert(state != oldState && "trivial cleanup state change");
   assert(oldState != CleanupState::Dead && "changing state of dead cleanup");

   // Our current cleanup emission logic, where we don't try to re-use
   // cleanup emissions between various branches, doesn't require any
   // code to be emitted at transition points.
 }

 void CleanupManager::dump() const {
 #ifndef NDEBUG
   auto begin = stack.stable_begin();
   auto end = stack.stable_end();
   while (begin != end) {
     auto iter = stack.find(begin);
     const Cleanup &stackCleanup = *iter;
     llvm::errs() << "CLEANUP DEPTH: " << begin.getDepth() << "\n";
     stackCleanup.dump(SGF);
     begin = stack.stabilize(++iter);
     stack.checkIterator(begin);
   }
 #endif
 }

 void CleanupManager::dump(CleanupHandle handle) const {
   auto iter = stack.find(handle);
   const Cleanup &stackCleanup = *iter;
   llvm::errs() << "CLEANUP DEPTH: " << handle.getDepth() << "\n";
   stackCleanup.dump(SGF);
 }

 void CleanupManager::checkIterator(CleanupHandle handle) const {
 #ifndef NDEBUG
   stack.checkIterator(handle);
 #endif
 }

 //===----------------------------------------------------------------------===//
 //                        CleanupStateRestorationScope
 //===----------------------------------------------------------------------===//

 void CleanupStateRestorationScope::pushCleanupState(CleanupHandle handle,
                                                     CleanupState newState) {
   // Don't put the cleanup in a state we can't restore it from.
   assert(newState != CleanupState::Dead && "cannot restore cleanup from death");

   auto iter = cleanups.stack.find(handle);
   assert(iter != cleanups.stack.end() && "can't change end of cleanups stack");
   Cleanup &cleanup = *iter;
   assert(cleanup.getState() != CleanupState::Dead &&
          "changing state of dead cleanup");

   CleanupState oldState = cleanup.getState();
   cleanup.setState(cleanups.SGF, newState);

   savedStates.push_back({handle, oldState});
 }

 void
 CleanupStateRestorationScope::pushCurrentCleanupState(CleanupHandle handle) {
   auto iter = cleanups.stack.find(handle);
   assert(iter != cleanups.stack.end() && "can't change end of cleanups stack");
   Cleanup &cleanup = *iter;
   assert(cleanup.getState() != CleanupState::Dead &&
          "changing state of dead cleanup");

   CleanupState oldState = cleanup.getState();
   savedStates.push_back({handle, oldState});
 }

 void CleanupStateRestorationScope::popImpl() {
   // Restore cleanup states in the opposite order in which we saved them.
   for (auto i = savedStates.rbegin(), e = savedStates.rend(); i != e; ++i) {
     CleanupHandle handle = i->first;
     CleanupState stateToRestore = i->second;

     auto iter = cleanups.stack.find(handle);
     assert(iter != cleanups.stack.end() &&
            "can't change end of cleanups stack");
     Cleanup &cleanup = *iter;
     assert(cleanup.getState() != CleanupState::Dead &&
            "changing state of dead cleanup");
     cleanup.setState(cleanups.SGF, stateToRestore);
   }

   savedStates.clear();
 }

 void CleanupStateRestorationScope::pop() && { popImpl(); }

 //===----------------------------------------------------------------------===//
 //                               Cleanup Cloner
 //===----------------------------------------------------------------------===//

 CleanupCloner::CleanupCloner(SILGenFunction &SGF, const ManagedValue &mv)
     : SGF(SGF), hasCleanup(mv.hasCleanup()), isLValue(mv.isLValue()) {}

 CleanupCloner::CleanupCloner(SILGenBuilder &builder, const ManagedValue &mv)
     : CleanupCloner(builder.getSILGenFunction(), mv) {}

 CleanupCloner::CleanupCloner(SILGenFunction &SGF, const RValue &rv)
     : SGF(SGF), hasCleanup(rv.isPlusOne(SGF)), isLValue(false) {}

 CleanupCloner::CleanupCloner(SILGenBuilder &builder, const RValue &rv)
     : CleanupCloner(builder.getSILGenFunction(), rv) {}

 ManagedValue CleanupCloner::clone(SILValue value) const {
   if (isLValue) {
     return ManagedValue::forLValue(value);
   }

   if (!hasCleanup) {
     return ManagedValue::forUnmanaged(value);
   }

   if (value->getType().isAddress()) {
     return SGF.emitManagedBufferWithCleanup(value);
   }

   return SGF.emitManagedRValueWithCleanup(value);
 }
	//===--- Cleanup.cpp - Implements the Cleanup mechanics -------------------===//
	//
	// 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
	//
	//===----------------------------------------------------------------------===//

	#include "Cleanup.h"
	#include "ManagedValue.h"
	#include "RValue.h"
	#include "Scope.h"
	#include "SILGenBuilder.h"
	#include "SILGenFunction.h"

	using namespace swift;
	using namespace Lowering;

	//===----------------------------------------------------------------------===//
	// CleanupState
	//===----------------------------------------------------------------------===//

	llvm::raw_ostream &Lowering::operator<<(llvm::raw_ostream &os,
	CleanupState state) {
	switch (state) {
	case CleanupState::Dormant:
	return os << "Dormant";
	case CleanupState::Dead:
	return os << "Dead";
	case CleanupState::Active:
	return os << "Active";
	case CleanupState::PersistentlyActive:
	return os << "PersistentlyActive";
	}

	llvm_unreachable("Unhandled CleanupState in switch.");
	}

	//===----------------------------------------------------------------------===//
	// CleanupManager
	//===----------------------------------------------------------------------===//

	/// Are there any active cleanups in the given range?
	static bool hasAnyActiveCleanups(DiverseStackImpl<Cleanup>::iterator begin,
	DiverseStackImpl<Cleanup>::iterator end) {
	for (; begin != end; ++begin)
	if (begin->isActive())
	return true;
	return false;
	}

	void CleanupManager::popTopDeadCleanups() {
	auto end = (innermostScope ? innermostScope->depth : stack.stable_end());
	assert(end.isValid());
	stack.checkIterator(end);

	while (stack.stable_begin() != end && stack.begin()->isDead()) {
	assert(!stack.empty());
	stack.pop();
	stack.checkIterator(end);
	}
	}

	using CleanupBuffer = DiverseValueBuffer<Cleanup>;

	void CleanupManager::popAndEmitCleanup(CleanupHandle handle,
	CleanupLocation loc,
	ForUnwind_t forUnwind) {
	auto iter = stack.find(handle);
	Cleanup &stackCleanup = *iter;

	// Copy the cleanup off the cleanup stack.
	CleanupBuffer buffer(stackCleanup);
	Cleanup &cleanup = buffer.getCopy();

	// Deactivate it.
	forwardCleanup(handle);

	// Emit the cleanup.
	cleanup.emit(SGF, loc, forUnwind);
	}

	void CleanupManager::emitCleanups(CleanupsDepth depth, CleanupLocation loc,
	ForUnwind_t forUnwind, bool popCleanups) {
	auto cur = stack.stable_begin();
	#ifndef NDEBUG
	auto topOfStack = cur;
	#endif
	while (cur != depth) {
	// Advance the iterator.
	auto cleanupHandle = cur;
	auto iter = stack.find(cleanupHandle);
	Cleanup &stackCleanup = *iter;
	cur = stack.stabilize(++iter);

	// Copy the cleanup off the stack if it needs to be emitted.
	// This is necessary both because we might need to pop the cleanup and
	// because the cleanup might push other cleanups that will invalidate
	// references onto the stack.
	Optional<CleanupBuffer> copiedCleanup;
	if (stackCleanup.isActive() && SGF.B.hasValidInsertionPoint()) {
	copiedCleanup.emplace(stackCleanup);
	}

	// Pop now if that was requested.
	if (popCleanups) {
	#ifndef NDEBUG
	// This is an implicit deactivation.
	if (stackCleanup.isActive()) {
	SGF.FormalEvalContext.checkCleanupDeactivation(cleanupHandle);
	}
	#endif

	stack.pop();

	#ifndef NDEBUG
	topOfStack = stack.stable_begin();
	#endif
	}

	// Emit the cleanup.
	if (copiedCleanup) {
	copiedCleanup->getCopy().emit(SGF, loc, forUnwind);
	#ifndef NDEBUG
	if (hasAnyActiveCleanups(stack.stable_begin(), topOfStack)) {
	copiedCleanup->getCopy().dump(SGF);
	llvm_unreachable("cleanup left active cleanups on stack");
	}
	#endif
	}

	stack.checkIterator(cur);
	}
	}

	/// Leave a scope, emitting all the cleanups that are currently active.
	void CleanupManager::endScope(CleanupsDepth depth, CleanupLocation loc) {
	emitCleanups(depth, loc, NotForUnwind, /popCleanups/ true);
	}

	bool CleanupManager::hasAnyActiveCleanups(CleanupsDepth from,
	CleanupsDepth to) {
	return ::hasAnyActiveCleanups(stack.find(from), stack.find(to));
	}

	bool CleanupManager::hasAnyActiveCleanups(CleanupsDepth from) {
	return ::hasAnyActiveCleanups(stack.begin(), stack.find(from));
	}

	/// emitBranchAndCleanups - Emit a branch to the given jump destination,
	/// threading out through any cleanups we might need to run. This does not
	/// pop the cleanup stack.
	void CleanupManager::emitBranchAndCleanups(JumpDest dest, SILLocation branchLoc,
	ArrayRef<SILValue> args,
	ForUnwind_t forUnwind) {
	SILGenBuilder &builder = SGF.getBuilder();
	assert(builder.hasValidInsertionPoint() && "Emitting branch in invalid spot");
	emitCleanups(dest.getDepth(), dest.getCleanupLocation(),
	forUnwind, /popCleanups=/false);
	builder.createBranch(branchLoc, dest.getBlock(), args);
	}

	void CleanupManager::emitCleanupsForReturn(CleanupLocation loc,
	ForUnwind_t forUnwind) {
	SILGenBuilder &builder = SGF.getBuilder();
	assert(builder.hasValidInsertionPoint() && "Emitting return in invalid spot");
	(void)builder;
	emitCleanups(stack.stable_end(), loc, forUnwind, /popCleanups=/false);
	}

	/// Emit a new block that jumps to the specified location and runs necessary
	/// cleanups based on its level. Emit a block even if there are no cleanups;
	/// this is usually the destination of a conditional branch, so jumping
	/// straight to `dest` creates a critical edge.
	SILBasicBlock *CleanupManager::emitBlockForCleanups(JumpDest dest,
	SILLocation branchLoc,
	ArrayRef<SILValue> args,
	ForUnwind_t forUnwind) {
	// Otherwise, create and emit a new block.
	auto *newBlock = SGF.createBasicBlock();
	SILGenSavedInsertionPoint IPRAII(SGF, newBlock);
	emitBranchAndCleanups(dest, branchLoc, args, forUnwind);
	return newBlock;
	}


	Cleanup &CleanupManager::initCleanup(Cleanup &cleanup,
	size_t allocSize,
	CleanupState state) {
	cleanup.allocatedSize = allocSize;
	cleanup.state = state;
	return cleanup;
	}

	#ifndef NDEBUG
	static void checkCleanupDeactivation(SILGenFunction &SGF,
	CleanupsDepth handle,
	CleanupState state) {
	if (state != CleanupState::Dead) return;
	SGF.FormalEvalContext.checkCleanupDeactivation(handle);
	}
	#endif

	void CleanupManager::setCleanupState(CleanupsDepth depth, CleanupState state) {
	auto iter = stack.find(depth);
	assert(iter != stack.end() && "can't change end of cleanups stack");
	setCleanupState(*iter, state);

	#ifndef NDEBUG
	// This must be done after setting the state because setting the state can
	// itself finish a formal evaluation in some cases.
	checkCleanupDeactivation(SGF, depth, state);
	#endif

	if (state == CleanupState::Dead && iter == stack.begin())
	popTopDeadCleanups();
	}

	void CleanupManager::forwardCleanup(CleanupsDepth handle) {
	auto iter = stack.find(handle);
	assert(iter != stack.end() && "can't change end of cleanups stack");
	Cleanup &cleanup = *iter;
	assert(cleanup.isActive() && "forwarding inactive or dead cleanup?");

	CleanupState newState = (cleanup.getState() == CleanupState::Active
	? CleanupState::Dead
	: CleanupState::Dormant);
	setCleanupState(cleanup, newState);

	#ifndef NDEBUG
	// This must be done after setting the state because setting the state can
	// itself finish a formal evaluation in some cases.
	checkCleanupDeactivation(SGF, handle, newState);
	#endif

	if (newState == CleanupState::Dead && iter == stack.begin())
	popTopDeadCleanups();
	}

	void CleanupManager::setCleanupState(Cleanup &cleanup, CleanupState state) {
	assert(SGF.B.hasValidInsertionPoint() &&
	"changing cleanup state at invalid IP");

	// Do the transition now to avoid doing it in N places below.
	CleanupState oldState = cleanup.getState();
	(void)oldState;
	cleanup.setState(SGF, state);

	assert(state != oldState && "trivial cleanup state change");
	assert(oldState != CleanupState::Dead && "changing state of dead cleanup");

	// Our current cleanup emission logic, where we don't try to re-use
	// cleanup emissions between various branches, doesn't require any
	// code to be emitted at transition points.
	}

	void CleanupManager::dump() const {
	#ifndef NDEBUG
	auto begin = stack.stable_begin();
	auto end = stack.stable_end();
	while (begin != end) {
	auto iter = stack.find(begin);
	const Cleanup &stackCleanup = *iter;
	llvm::errs() << "CLEANUP DEPTH: " << begin.getDepth() << "\n";
	stackCleanup.dump(SGF);
	begin = stack.stabilize(++iter);
	stack.checkIterator(begin);
	}
	#endif
	}

	void CleanupManager::dump(CleanupHandle handle) const {
	auto iter = stack.find(handle);
	const Cleanup &stackCleanup = *iter;
	llvm::errs() << "CLEANUP DEPTH: " << handle.getDepth() << "\n";
	stackCleanup.dump(SGF);
	}

	void CleanupManager::checkIterator(CleanupHandle handle) const {
	#ifndef NDEBUG
	stack.checkIterator(handle);
	#endif
	}

	//===----------------------------------------------------------------------===//
	// CleanupStateRestorationScope
	//===----------------------------------------------------------------------===//

	void CleanupStateRestorationScope::pushCleanupState(CleanupHandle handle,
	CleanupState newState) {
	// Don't put the cleanup in a state we can't restore it from.
	assert(newState != CleanupState::Dead && "cannot restore cleanup from death");

	auto iter = cleanups.stack.find(handle);
	assert(iter != cleanups.stack.end() && "can't change end of cleanups stack");
	Cleanup &cleanup = *iter;
	assert(cleanup.getState() != CleanupState::Dead &&
	"changing state of dead cleanup");

	CleanupState oldState = cleanup.getState();
	cleanup.setState(cleanups.SGF, newState);

	savedStates.push_back({handle, oldState});
	}

	void
	CleanupStateRestorationScope::pushCurrentCleanupState(CleanupHandle handle) {
	auto iter = cleanups.stack.find(handle);
	assert(iter != cleanups.stack.end() && "can't change end of cleanups stack");
	Cleanup &cleanup = *iter;
	assert(cleanup.getState() != CleanupState::Dead &&
	"changing state of dead cleanup");

	CleanupState oldState = cleanup.getState();
	savedStates.push_back({handle, oldState});
	}

	void CleanupStateRestorationScope::popImpl() {
	// Restore cleanup states in the opposite order in which we saved them.
	for (auto i = savedStates.rbegin(), e = savedStates.rend(); i != e; ++i) {
	CleanupHandle handle = i->first;
	CleanupState stateToRestore = i->second;

	auto iter = cleanups.stack.find(handle);
	assert(iter != cleanups.stack.end() &&
	"can't change end of cleanups stack");
	Cleanup &cleanup = *iter;
	assert(cleanup.getState() != CleanupState::Dead &&
	"changing state of dead cleanup");
	cleanup.setState(cleanups.SGF, stateToRestore);
	}

	savedStates.clear();
	}

	void CleanupStateRestorationScope::pop() && { popImpl(); }

	//===----------------------------------------------------------------------===//
	// Cleanup Cloner
	//===----------------------------------------------------------------------===//

	CleanupCloner::CleanupCloner(SILGenFunction &SGF, const ManagedValue &mv)
	: SGF(SGF), hasCleanup(mv.hasCleanup()), isLValue(mv.isLValue()) {}

	CleanupCloner::CleanupCloner(SILGenBuilder &builder, const ManagedValue &mv)
	: CleanupCloner(builder.getSILGenFunction(), mv) {}

	CleanupCloner::CleanupCloner(SILGenFunction &SGF, const RValue &rv)
	: SGF(SGF), hasCleanup(rv.isPlusOne(SGF)), isLValue(false) {}

	CleanupCloner::CleanupCloner(SILGenBuilder &builder, const RValue &rv)
	: CleanupCloner(builder.getSILGenFunction(), rv) {}

	ManagedValue CleanupCloner::clone(SILValue value) const {
	if (isLValue) {
	return ManagedValue::forLValue(value);
	}

	if (!hasCleanup) {
	return ManagedValue::forUnmanaged(value);
	}

	if (value->getType().isAddress()) {
	return SGF.emitManagedBufferWithCleanup(value);
	}

	return SGF.emitManagedRValueWithCleanup(value);
	}