lib/IRGen/GenTuple.cpp - third_party/swift - Git at Google

 //===--- GenTuple.cpp - Swift IR Generation For Tuple Types ---------------===//
 //
 // This source file is part of the Swift.org open source project
 //
 // Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 //
 //===----------------------------------------------------------------------===//
 //
 //  This file implements IR generation for tuple types in Swift.  This
 //  includes creating the IR type as well as emitting the primitive access
 //  operations.
 //
 //  It is assumed in several places in IR-generation that the
 //  explosion schema of a tuple type is always equal to the appended
 //  explosion schemas of the component types.
 //
 //===----------------------------------------------------------------------===//

 #include "swift/AST/Types.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/Pattern.h"
 #include "swift/SIL/SILType.h"
 #include "llvm/IR/DerivedTypes.h"

 #include "GenHeap.h"
 #include "GenRecord.h"
 #include "GenType.h"
 #include "IRGenFunction.h"
 #include "IRGenModule.h"
 #include "Explosion.h"
 #include "IndirectTypeInfo.h"
 #include "NonFixedTypeInfo.h"

 #include "GenTuple.h"

 #pragma clang diagnostic ignored "-Winconsistent-missing-override"

 using namespace swift;
 using namespace irgen;

 namespace {
   class TupleFieldInfo : public RecordField<TupleFieldInfo> {
   public:
     TupleFieldInfo(unsigned index, StringRef name, const TypeInfo &type)
       : RecordField(type), Index(index), Name(name)
     {}

     /// The field index.
     const unsigned Index;
     const StringRef Name;

     StringRef getFieldName() const {
       return Name;
     }

     const TupleTypeElt &getField(SILType T) const {
       auto tup = T.castTo<TupleType>();

       return tup->getElement(Index);
     }

     SILType getType(IRGenModule&, SILType t) const {
       return t.getTupleElementType(Index);
     }
   };

   /// Adapter for tuple types.
   template <class Impl, class Base>
   class TupleTypeInfoBase
       : public RecordTypeInfo<Impl, Base, TupleFieldInfo> {
     typedef RecordTypeInfo<Impl, Base, TupleFieldInfo> super;

   protected:
     template <class... As>
     TupleTypeInfoBase(As &&...args) : super(std::forward<As>(args)...) {}

     using super::asImpl;

   public:
     /// Given a full tuple explosion, project out a single element.
     void projectElementFromExplosion(IRGenFunction &IGF,
                                      Explosion &tuple,
                                      unsigned fieldNo,
                                      Explosion &out) const {
       const TupleFieldInfo &field = asImpl().getFields()[fieldNo];

       // If the field requires no storage, there's nothing to do.
       if (field.isEmpty())
         return IGF.emitFakeExplosion(field.getTypeInfo(), out);

       // Otherwise, project from the base.
       auto fieldRange = field.getProjectionRange();
       ArrayRef<llvm::Value *> element = tuple.getRange(fieldRange.first,
                                                        fieldRange.second);
       out.add(element);
     }

     /// Given the address of a tuple, project out the address of a
     /// single element.
     Address projectElementAddress(IRGenFunction &IGF,
                                   Address tuple,
                                   SILType T,
                                   unsigned fieldNo) const {
       const TupleFieldInfo &field = asImpl().getFields()[fieldNo];
       if (field.isEmpty())
         return field.getTypeInfo().getUndefAddress();

       auto offsets = asImpl().getNonFixedOffsets(IGF, T);
       return field.projectAddress(IGF, tuple, offsets);
     }

     /// Return the statically-known offset of the given element.
     Optional<Size> getFixedElementOffset(IRGenModule &IGM,
                                          unsigned fieldNo) const {
       const TupleFieldInfo &field = asImpl().getFields()[fieldNo];
       switch (field.getKind()) {
       case ElementLayout::Kind::Empty:
       case ElementLayout::Kind::Fixed:
         return field.getFixedByteOffset();
       case ElementLayout::Kind::InitialNonFixedSize:
         return Size(0);
       case ElementLayout::Kind::NonFixed:
         return None;
       }
       llvm_unreachable("bad element layout kind");
     }

     void initializeFromParams(IRGenFunction &IGF, Explosion &params,
                               Address src, SILType T) const override {
       llvm_unreachable("unexploded tuple as argument?");
     }

     // For now, just use extra inhabitants from the first element.
     // FIXME: generalize
     bool mayHaveExtraInhabitants(IRGenModule &IGM) const override {
       if (asImpl().getFields().empty()) return false;
       return asImpl().getFields()[0].getTypeInfo().mayHaveExtraInhabitants(IGM);
     }

     // This is dead code in NonFixedTupleTypeInfo.
     unsigned getFixedExtraInhabitantCount(IRGenModule &IGM) const {
       if (asImpl().getFields().empty()) return 0;
       auto &eltTI = cast<FixedTypeInfo>(asImpl().getFields()[0].getTypeInfo());
       return eltTI.getFixedExtraInhabitantCount(IGM);
     }

     // This is dead code in NonFixedTupleTypeInfo.
     APInt getFixedExtraInhabitantValue(IRGenModule &IGM,
                                        unsigned bits,
                                        unsigned index) const {
       auto &eltTI = cast<FixedTypeInfo>(asImpl().getFields()[0].getTypeInfo());
       return eltTI.getFixedExtraInhabitantValue(IGM, bits, index);
     }

     // This is dead code in NonFixedTupleTypeInfo.
     APInt getFixedExtraInhabitantMask(IRGenModule &IGM) const {
       if (asImpl().getFields().empty())
         return APInt();

       const FixedTypeInfo &fieldTI
         = cast<FixedTypeInfo>(asImpl().getFields()[0].getTypeInfo());
       auto size = asImpl().getFixedSize().getValueInBits();

       if (fieldTI.isKnownEmpty(ResilienceExpansion::Maximal))
         return APInt(size, 0);

       APInt firstMask = fieldTI.getFixedExtraInhabitantMask(IGM);
       return firstMask.zextOrTrunc(size);
     }

     llvm::Value *getExtraInhabitantIndex(IRGenFunction &IGF,
                                          Address tupleAddr,
                                          SILType tupleType) const override {
       Address eltAddr =
         asImpl().projectElementAddress(IGF, tupleAddr, tupleType, 0);
       auto &elt = asImpl().getFields()[0];
       return elt.getTypeInfo().getExtraInhabitantIndex(IGF, eltAddr,
                                                elt.getType(IGF.IGM, tupleType));
     }

     void storeExtraInhabitant(IRGenFunction &IGF,
                               llvm::Value *index,
                               Address tupleAddr,
                               SILType tupleType) const override {
       Address eltAddr =
         asImpl().projectElementAddress(IGF, tupleAddr, tupleType, 0);
       auto &elt = asImpl().getFields()[0];
       elt.getTypeInfo().storeExtraInhabitant(IGF, index, eltAddr,
                                              elt.getType(IGF.IGM, tupleType));
     }
   };

   /// Type implementation for loadable tuples.
   class LoadableTupleTypeInfo final :
       public TupleTypeInfoBase<LoadableTupleTypeInfo, LoadableTypeInfo> {
   public:
     // FIXME: Spare bits between tuple elements.
     LoadableTupleTypeInfo(ArrayRef<TupleFieldInfo> fields,
                           unsigned explosionSize,
                           llvm::Type *ty,
                           Size size, SpareBitVector &&spareBits,
                           Alignment align, IsPOD_t isPOD,
                           IsFixedSize_t alwaysFixedSize)
       : TupleTypeInfoBase(fields, explosionSize,
                           ty, size, std::move(spareBits), align, isPOD,
                           alwaysFixedSize)
       {}

     void addToAggLowering(IRGenModule &IGM, SwiftAggLowering &lowering,
                           Size offset) const override {
       for (auto &field : getFields()) {
         auto fieldOffset = offset + field.getFixedByteOffset();
         cast<LoadableTypeInfo>(field.getTypeInfo())
           .addToAggLowering(IGM, lowering, fieldOffset);
       }
     }

     llvm::NoneType getNonFixedOffsets(IRGenFunction &IGF) const {
       return None;
     }
     llvm::NoneType getNonFixedOffsets(IRGenFunction &IGF, SILType T) const {
       return None;
     }
   };

   /// Type implementation for fixed-size but non-loadable tuples.
   class FixedTupleTypeInfo final :
       public TupleTypeInfoBase<FixedTupleTypeInfo,
                                IndirectTypeInfo<FixedTupleTypeInfo,
                                                 FixedTypeInfo>>
   {
   public:
     // FIXME: Spare bits between tuple elements.
     FixedTupleTypeInfo(ArrayRef<TupleFieldInfo> fields, llvm::Type *ty,
                        Size size, SpareBitVector &&spareBits, Alignment align,
                        IsPOD_t isPOD, IsBitwiseTakable_t isBT,
                        IsFixedSize_t alwaysFixedSize)
       : TupleTypeInfoBase(fields, ty, size, std::move(spareBits), align,
                           isPOD, isBT, alwaysFixedSize)
     {}

     llvm::NoneType getNonFixedOffsets(IRGenFunction &IGF) const {
       return None;
     }
     llvm::NoneType getNonFixedOffsets(IRGenFunction &IGF, SILType T) const {
       return None;
     }
   };

   /// An accessor for the non-fixed offsets for a tuple type.
   class TupleNonFixedOffsets : public NonFixedOffsetsImpl {
     // TODO: Should be a SILType.
     SILType TheType;
   public:
     TupleNonFixedOffsets(SILType type) : TheType(type) {
       assert(TheType.is<TupleType>());
     }

     llvm::Value *getOffsetForIndex(IRGenFunction &IGF, unsigned index) {
       // Fetch the metadata as a tuple type.  We cache this because
       // we might repeatedly need the bitcast.
       auto metadata = IGF.emitTypeMetadataRefForLayout(TheType);
       auto asTuple = IGF.Builder.CreateBitCast(metadata,
                                                IGF.IGM.TupleTypeMetadataPtrTy);

       llvm::Value *indices[] = {
         IGF.IGM.getSize(Size(0)),                   // (*tupleType)
         llvm::ConstantInt::get(IGF.IGM.Int32Ty, 3), //   .Elements
         IGF.IGM.getSize(Size(index)),               //     [index]
         llvm::ConstantInt::get(IGF.IGM.Int32Ty, 1)  //       .Offset
       };
       auto slot = IGF.Builder.CreateInBoundsGEP(asTuple, indices);

       return IGF.Builder.CreateLoad(slot, IGF.IGM.getPointerAlignment(),
                                     metadata->getName()
                                       + "." + Twine(index) + ".offset");
     }
   };

   /// Type implementation for non-fixed-size tuples.
   class NonFixedTupleTypeInfo final :
       public TupleTypeInfoBase<NonFixedTupleTypeInfo,
                                WitnessSizedTypeInfo<NonFixedTupleTypeInfo>>
   {
   public:
     NonFixedTupleTypeInfo(ArrayRef<TupleFieldInfo> fields, llvm::Type *T,
                           Alignment minAlign, IsPOD_t isPOD,
                           IsBitwiseTakable_t isBT)
       : TupleTypeInfoBase(fields, T, minAlign, isPOD, isBT) {}

     TupleNonFixedOffsets getNonFixedOffsets(IRGenFunction &IGF,
                                             SILType T) const {
       return TupleNonFixedOffsets(T);
     }

     void initializeMetadata(IRGenFunction &IGF,
                             llvm::Value *metadata,
                             llvm::Value *vwtable,
                             SILType T) const override {
       // Tuple value witness tables are instantiated by the runtime along with
       // their metadata. We should never try to initialize one in the compiler.
       llvm_unreachable("initializing value witness table for tuple?!");
     }
   };

   class TupleTypeBuilder :
       public RecordTypeBuilder<TupleTypeBuilder, TupleFieldInfo,
                                TupleTypeElt> {
     SILType TheTuple;

   public:
     TupleTypeBuilder(IRGenModule &IGM, SILType theTuple)
       : RecordTypeBuilder(IGM), TheTuple(theTuple) {}

     FixedTupleTypeInfo *createFixed(ArrayRef<TupleFieldInfo> fields,
                                     StructLayout &&layout) {
       return FixedTupleTypeInfo::create(fields, layout.getType(),
                                         layout.getSize(),
                                         std::move(layout.getSpareBits()),
                                         layout.getAlignment(),
                                         layout.isPOD(),
                                         layout.isBitwiseTakable(),
                                         layout.isAlwaysFixedSize());
     }

     LoadableTupleTypeInfo *createLoadable(ArrayRef<TupleFieldInfo> fields,
                                           StructLayout &&layout,
                                           unsigned explosionSize) {
       return LoadableTupleTypeInfo::create(fields, explosionSize,
                                            layout.getType(), layout.getSize(),
                                            std::move(layout.getSpareBits()),
                                            layout.getAlignment(),
                                            layout.isPOD(),
                                            layout.isAlwaysFixedSize());
     }

     NonFixedTupleTypeInfo *createNonFixed(ArrayRef<TupleFieldInfo> fields,
                                           StructLayout &&layout) {
       return NonFixedTupleTypeInfo::create(fields, layout.getType(),
                                            layout.getAlignment(),
                                            layout.isPOD(),
                                            layout.isBitwiseTakable());
     }

     TupleFieldInfo getFieldInfo(unsigned index,
                                 const TupleTypeElt &field,
                                 const TypeInfo &fieldTI) {
       StringRef name = field.hasName() ? field.getName().str() : "elt";
       return TupleFieldInfo(index, name, fieldTI);
     }

     SILType getType(const TupleTypeElt &field) {
       // We know we're working with a lowered type here.
       return SILType::getPrimitiveObjectType(CanType(field.getType()));
     }

     StructLayout performLayout(ArrayRef<const TypeInfo *> fieldTypes) {
       return StructLayout(IGM, CanType(), LayoutKind::NonHeapObject,
                           LayoutStrategy::Universal, fieldTypes);
     }
   };
 }

 const TypeInfo *TypeConverter::convertTupleType(TupleType *tuple) {
   TupleTypeBuilder builder(IGM, SILType::getPrimitiveAddressType(CanType(tuple)));
   return builder.layout(tuple->getElements());
 }

 /// A convenient macro for delegating an operation to all of the
 /// various tuple implementations.
 #define FOR_TUPLE_IMPL(IGF, type, op, ...) do {                      \
   auto &tupleTI = IGF.getTypeInfo(type);                             \
   if (isa<LoadableTypeInfo>(tupleTI)) {                              \
     return tupleTI.as<LoadableTupleTypeInfo>().op(IGF, __VA_ARGS__); \
   } else if (isa<FixedTypeInfo>(tupleTI)) {                          \
     return tupleTI.as<FixedTupleTypeInfo>().op(IGF, __VA_ARGS__);    \
   } else {                                                           \
     return tupleTI.as<NonFixedTupleTypeInfo>().op(IGF, __VA_ARGS__); \
   }                                                                  \
 } while (0)

 void irgen::projectTupleElementFromExplosion(IRGenFunction &IGF,
                                              SILType tupleType,
                                              Explosion &tuple,
                                              unsigned fieldNo,
                                              Explosion &out) {
   FOR_TUPLE_IMPL(IGF, tupleType, projectElementFromExplosion,
                  tuple, fieldNo, out);
 }

 Address irgen::projectTupleElementAddress(IRGenFunction &IGF,
                                           Address tuple,
                                           SILType tupleType,
                                           unsigned fieldNo) {
   FOR_TUPLE_IMPL(IGF, tupleType, projectElementAddress, tuple,
                  tupleType, fieldNo);
 }

 Optional<Size> irgen::getFixedTupleElementOffset(IRGenModule &IGM,
                                                  SILType tupleType,
                                                  unsigned fieldNo) {
   // Macro happens to work with IGM, too.
   FOR_TUPLE_IMPL(IGM, tupleType, getFixedElementOffset, fieldNo);
 }
	//===--- GenTuple.cpp - Swift IR Generation For Tuple Types ---------------===//
	//
	// This source file is part of the Swift.org open source project
	//
	// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
	// Licensed under Apache License v2.0 with Runtime Library Exception
	//
	// See http://swift.org/LICENSE.txt for license information
	// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
	//
	//===----------------------------------------------------------------------===//
	//
	// This file implements IR generation for tuple types in Swift. This
	// includes creating the IR type as well as emitting the primitive access
	// operations.
	//
	// It is assumed in several places in IR-generation that the
	// explosion schema of a tuple type is always equal to the appended
	// explosion schemas of the component types.
	//
	//===----------------------------------------------------------------------===//

	#include "swift/AST/Types.h"
	#include "swift/AST/Decl.h"
	#include "swift/AST/Pattern.h"
	#include "swift/SIL/SILType.h"
	#include "llvm/IR/DerivedTypes.h"

	#include "GenHeap.h"
	#include "GenRecord.h"
	#include "GenType.h"
	#include "IRGenFunction.h"
	#include "IRGenModule.h"
	#include "Explosion.h"
	#include "IndirectTypeInfo.h"
	#include "NonFixedTypeInfo.h"

	#include "GenTuple.h"

	#pragma clang diagnostic ignored "-Winconsistent-missing-override"

	using namespace swift;
	using namespace irgen;

	namespace {
	class TupleFieldInfo : public RecordField<TupleFieldInfo> {
	public:
	TupleFieldInfo(unsigned index, StringRef name, const TypeInfo &type)
	: RecordField(type), Index(index), Name(name)
	{}

	/// The field index.
	const unsigned Index;
	const StringRef Name;

	StringRef getFieldName() const {
	return Name;
	}

	const TupleTypeElt &getField(SILType T) const {
	auto tup = T.castTo<TupleType>();

	return tup->getElement(Index);
	}

	SILType getType(IRGenModule&, SILType t) const {
	return t.getTupleElementType(Index);
	}
	};

	/// Adapter for tuple types.
	template <class Impl, class Base>
	class TupleTypeInfoBase
	: public RecordTypeInfo<Impl, Base, TupleFieldInfo> {
	typedef RecordTypeInfo<Impl, Base, TupleFieldInfo> super;

	protected:
	template <class... As>
	TupleTypeInfoBase(As &&...args) : super(std::forward<As>(args)...) {}

	using super::asImpl;

	public:
	/// Given a full tuple explosion, project out a single element.
	void projectElementFromExplosion(IRGenFunction &IGF,
	Explosion &tuple,
	unsigned fieldNo,
	Explosion &out) const {
	const TupleFieldInfo &field = asImpl().getFields()[fieldNo];

	// If the field requires no storage, there's nothing to do.
	if (field.isEmpty())
	return IGF.emitFakeExplosion(field.getTypeInfo(), out);

	// Otherwise, project from the base.
	auto fieldRange = field.getProjectionRange();
	ArrayRef<llvm::Value *> element = tuple.getRange(fieldRange.first,
	fieldRange.second);
	out.add(element);
	}

	/// Given the address of a tuple, project out the address of a
	/// single element.
	Address projectElementAddress(IRGenFunction &IGF,
	Address tuple,
	SILType T,
	unsigned fieldNo) const {
	const TupleFieldInfo &field = asImpl().getFields()[fieldNo];
	if (field.isEmpty())
	return field.getTypeInfo().getUndefAddress();

	auto offsets = asImpl().getNonFixedOffsets(IGF, T);
	return field.projectAddress(IGF, tuple, offsets);
	}

	/// Return the statically-known offset of the given element.
	Optional<Size> getFixedElementOffset(IRGenModule &IGM,
	unsigned fieldNo) const {
	const TupleFieldInfo &field = asImpl().getFields()[fieldNo];
	switch (field.getKind()) {
	case ElementLayout::Kind::Empty:
	case ElementLayout::Kind::Fixed:
	return field.getFixedByteOffset();
	case ElementLayout::Kind::InitialNonFixedSize:
	return Size(0);
	case ElementLayout::Kind::NonFixed:
	return None;
	}
	llvm_unreachable("bad element layout kind");
	}

	void initializeFromParams(IRGenFunction &IGF, Explosion &params,
	Address src, SILType T) const override {
	llvm_unreachable("unexploded tuple as argument?");
	}

	// For now, just use extra inhabitants from the first element.
	// FIXME: generalize
	bool mayHaveExtraInhabitants(IRGenModule &IGM) const override {
	if (asImpl().getFields().empty()) return false;
	return asImpl().getFields()[0].getTypeInfo().mayHaveExtraInhabitants(IGM);
	}

	// This is dead code in NonFixedTupleTypeInfo.
	unsigned getFixedExtraInhabitantCount(IRGenModule &IGM) const {
	if (asImpl().getFields().empty()) return 0;
	auto &eltTI = cast<FixedTypeInfo>(asImpl().getFields()[0].getTypeInfo());
	return eltTI.getFixedExtraInhabitantCount(IGM);
	}

	// This is dead code in NonFixedTupleTypeInfo.
	APInt getFixedExtraInhabitantValue(IRGenModule &IGM,
	unsigned bits,
	unsigned index) const {
	auto &eltTI = cast<FixedTypeInfo>(asImpl().getFields()[0].getTypeInfo());
	return eltTI.getFixedExtraInhabitantValue(IGM, bits, index);
	}

	// This is dead code in NonFixedTupleTypeInfo.
	APInt getFixedExtraInhabitantMask(IRGenModule &IGM) const {
	if (asImpl().getFields().empty())
	return APInt();

	const FixedTypeInfo &fieldTI
	= cast<FixedTypeInfo>(asImpl().getFields()[0].getTypeInfo());
	auto size = asImpl().getFixedSize().getValueInBits();

	if (fieldTI.isKnownEmpty(ResilienceExpansion::Maximal))
	return APInt(size, 0);

	APInt firstMask = fieldTI.getFixedExtraInhabitantMask(IGM);
	return firstMask.zextOrTrunc(size);
	}

	llvm::Value *getExtraInhabitantIndex(IRGenFunction &IGF,
	Address tupleAddr,
	SILType tupleType) const override {
	Address eltAddr =
	asImpl().projectElementAddress(IGF, tupleAddr, tupleType, 0);
	auto &elt = asImpl().getFields()[0];
	return elt.getTypeInfo().getExtraInhabitantIndex(IGF, eltAddr,
	elt.getType(IGF.IGM, tupleType));
	}

	void storeExtraInhabitant(IRGenFunction &IGF,
	llvm::Value *index,
	Address tupleAddr,
	SILType tupleType) const override {
	Address eltAddr =
	asImpl().projectElementAddress(IGF, tupleAddr, tupleType, 0);
	auto &elt = asImpl().getFields()[0];
	elt.getTypeInfo().storeExtraInhabitant(IGF, index, eltAddr,
	elt.getType(IGF.IGM, tupleType));
	}
	};

	/// Type implementation for loadable tuples.
	class LoadableTupleTypeInfo final :
	public TupleTypeInfoBase<LoadableTupleTypeInfo, LoadableTypeInfo> {
	public:
	// FIXME: Spare bits between tuple elements.
	LoadableTupleTypeInfo(ArrayRef<TupleFieldInfo> fields,
	unsigned explosionSize,
	llvm::Type *ty,
	Size size, SpareBitVector &&spareBits,
	Alignment align, IsPOD_t isPOD,
	IsFixedSize_t alwaysFixedSize)
	: TupleTypeInfoBase(fields, explosionSize,
	ty, size, std::move(spareBits), align, isPOD,
	alwaysFixedSize)
	{}

	void addToAggLowering(IRGenModule &IGM, SwiftAggLowering &lowering,
	Size offset) const override {
	for (auto &field : getFields()) {
	auto fieldOffset = offset + field.getFixedByteOffset();
	cast<LoadableTypeInfo>(field.getTypeInfo())
	.addToAggLowering(IGM, lowering, fieldOffset);
	}
	}

	llvm::NoneType getNonFixedOffsets(IRGenFunction &IGF) const {
	return None;
	}
	llvm::NoneType getNonFixedOffsets(IRGenFunction &IGF, SILType T) const {
	return None;
	}
	};

	/// Type implementation for fixed-size but non-loadable tuples.
	class FixedTupleTypeInfo final :
	public TupleTypeInfoBase<FixedTupleTypeInfo,
	IndirectTypeInfo<FixedTupleTypeInfo,
	FixedTypeInfo>>
	{
	public:
	// FIXME: Spare bits between tuple elements.
	FixedTupleTypeInfo(ArrayRef<TupleFieldInfo> fields, llvm::Type *ty,
	Size size, SpareBitVector &&spareBits, Alignment align,
	IsPOD_t isPOD, IsBitwiseTakable_t isBT,
	IsFixedSize_t alwaysFixedSize)
	: TupleTypeInfoBase(fields, ty, size, std::move(spareBits), align,
	isPOD, isBT, alwaysFixedSize)
	{}

	llvm::NoneType getNonFixedOffsets(IRGenFunction &IGF) const {
	return None;
	}
	llvm::NoneType getNonFixedOffsets(IRGenFunction &IGF, SILType T) const {
	return None;
	}
	};

	/// An accessor for the non-fixed offsets for a tuple type.
	class TupleNonFixedOffsets : public NonFixedOffsetsImpl {
	// TODO: Should be a SILType.
	SILType TheType;
	public:
	TupleNonFixedOffsets(SILType type) : TheType(type) {
	assert(TheType.is<TupleType>());
	}

	llvm::Value *getOffsetForIndex(IRGenFunction &IGF, unsigned index) {
	// Fetch the metadata as a tuple type. We cache this because
	// we might repeatedly need the bitcast.
	auto metadata = IGF.emitTypeMetadataRefForLayout(TheType);
	auto asTuple = IGF.Builder.CreateBitCast(metadata,
	IGF.IGM.TupleTypeMetadataPtrTy);

	llvm::Value *indices[] = {
	IGF.IGM.getSize(Size(0)), // (*tupleType)
	llvm::ConstantInt::get(IGF.IGM.Int32Ty, 3), // .Elements
	IGF.IGM.getSize(Size(index)), // [index]
	llvm::ConstantInt::get(IGF.IGM.Int32Ty, 1) // .Offset
	};
	auto slot = IGF.Builder.CreateInBoundsGEP(asTuple, indices);

	return IGF.Builder.CreateLoad(slot, IGF.IGM.getPointerAlignment(),
	metadata->getName()
	+ "." + Twine(index) + ".offset");
	}
	};

	/// Type implementation for non-fixed-size tuples.
	class NonFixedTupleTypeInfo final :
	public TupleTypeInfoBase<NonFixedTupleTypeInfo,
	WitnessSizedTypeInfo<NonFixedTupleTypeInfo>>
	{
	public:
	NonFixedTupleTypeInfo(ArrayRef<TupleFieldInfo> fields, llvm::Type *T,
	Alignment minAlign, IsPOD_t isPOD,
	IsBitwiseTakable_t isBT)
	: TupleTypeInfoBase(fields, T, minAlign, isPOD, isBT) {}

	TupleNonFixedOffsets getNonFixedOffsets(IRGenFunction &IGF,
	SILType T) const {
	return TupleNonFixedOffsets(T);
	}

	void initializeMetadata(IRGenFunction &IGF,
	llvm::Value *metadata,
	llvm::Value *vwtable,
	SILType T) const override {
	// Tuple value witness tables are instantiated by the runtime along with
	// their metadata. We should never try to initialize one in the compiler.
	llvm_unreachable("initializing value witness table for tuple?!");
	}
	};

	class TupleTypeBuilder :
	public RecordTypeBuilder<TupleTypeBuilder, TupleFieldInfo,
	TupleTypeElt> {
	SILType TheTuple;

	public:
	TupleTypeBuilder(IRGenModule &IGM, SILType theTuple)
	: RecordTypeBuilder(IGM), TheTuple(theTuple) {}

	FixedTupleTypeInfo *createFixed(ArrayRef<TupleFieldInfo> fields,
	StructLayout &&layout) {
	return FixedTupleTypeInfo::create(fields, layout.getType(),
	layout.getSize(),
	std::move(layout.getSpareBits()),
	layout.getAlignment(),
	layout.isPOD(),
	layout.isBitwiseTakable(),
	layout.isAlwaysFixedSize());
	}

	LoadableTupleTypeInfo *createLoadable(ArrayRef<TupleFieldInfo> fields,
	StructLayout &&layout,
	unsigned explosionSize) {
	return LoadableTupleTypeInfo::create(fields, explosionSize,
	layout.getType(), layout.getSize(),
	std::move(layout.getSpareBits()),
	layout.getAlignment(),
	layout.isPOD(),
	layout.isAlwaysFixedSize());
	}

	NonFixedTupleTypeInfo *createNonFixed(ArrayRef<TupleFieldInfo> fields,
	StructLayout &&layout) {
	return NonFixedTupleTypeInfo::create(fields, layout.getType(),
	layout.getAlignment(),
	layout.isPOD(),
	layout.isBitwiseTakable());
	}

	TupleFieldInfo getFieldInfo(unsigned index,
	const TupleTypeElt &field,
	const TypeInfo &fieldTI) {
	StringRef name = field.hasName() ? field.getName().str() : "elt";
	return TupleFieldInfo(index, name, fieldTI);
	}

	SILType getType(const TupleTypeElt &field) {
	// We know we're working with a lowered type here.
	return SILType::getPrimitiveObjectType(CanType(field.getType()));
	}

	StructLayout performLayout(ArrayRef<const TypeInfo *> fieldTypes) {
	return StructLayout(IGM, CanType(), LayoutKind::NonHeapObject,
	LayoutStrategy::Universal, fieldTypes);
	}
	};
	}

	const TypeInfo TypeConverter::convertTupleType(TupleType tuple) {
	TupleTypeBuilder builder(IGM, SILType::getPrimitiveAddressType(CanType(tuple)));
	return builder.layout(tuple->getElements());
	}

	/// A convenient macro for delegating an operation to all of the
	/// various tuple implementations.
	#define FOR_TUPLE_IMPL(IGF, type, op, ...) do { \
	auto &tupleTI = IGF.getTypeInfo(type); \
	if (isa<LoadableTypeInfo>(tupleTI)) { \
	return tupleTI.as<LoadableTupleTypeInfo>().op(IGF, __VA_ARGS__); \
	} else if (isa<FixedTypeInfo>(tupleTI)) { \
	return tupleTI.as<FixedTupleTypeInfo>().op(IGF, __VA_ARGS__); \
	} else { \
	return tupleTI.as<NonFixedTupleTypeInfo>().op(IGF, __VA_ARGS__); \
	} \
	} while (0)

	void irgen::projectTupleElementFromExplosion(IRGenFunction &IGF,
	SILType tupleType,
	Explosion &tuple,
	unsigned fieldNo,
	Explosion &out) {
	FOR_TUPLE_IMPL(IGF, tupleType, projectElementFromExplosion,
	tuple, fieldNo, out);
	}

	Address irgen::projectTupleElementAddress(IRGenFunction &IGF,
	Address tuple,
	SILType tupleType,
	unsigned fieldNo) {
	FOR_TUPLE_IMPL(IGF, tupleType, projectElementAddress, tuple,
	tupleType, fieldNo);
	}

	Optional<Size> irgen::getFixedTupleElementOffset(IRGenModule &IGM,
	SILType tupleType,
	unsigned fieldNo) {
	// Macro happens to work with IGM, too.
	FOR_TUPLE_IMPL(IGM, tupleType, getFixedElementOffset, fieldNo);
	}