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

 //===--- Conversion.h - Types for value conversion --------------*- 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
 //
 //===----------------------------------------------------------------------===//
 //
 // Defines the Conversion class as well as ConvertingInitialization.
 //
 //===----------------------------------------------------------------------===//

 #ifndef SWIFT_LOWERING_CONVERSION_H
 #define SWIFT_LOWERING_CONVERSION_H

 #include "swift/Basic/ExternalUnion.h"
 #include "Initialization.h"
 #include "SGFContext.h"

 namespace swift {
 namespace Lowering {

 /// An abstraction representing certain kinds of conversion that SILGen can
 /// do automatically in various situations.
 class Conversion {
 public:
   enum KindTy {
     /// A bridging conversion to a foreign type.
     BridgeToObjC,

     /// A bridging conversion to a foreign type following a force.
     /// Although it's not reflected in the name, this is always an
     /// implicit force cast.
     ForceAndBridgeToObjC,

     /// A bridging conversion from a foreign type.
     BridgeFromObjC,

     /// A bridging conversion for a function result.
     BridgeResultFromObjC,

     /// An erasure to Any (possibly wrapped in optional conversions).
     /// This is sortof a bridging conversion.
     AnyErasure,

     LastBridgingKind = AnyErasure,

     /// An orig-to-subst conversion.
     OrigToSubst,

     /// A subst-to-orig conversion.  These can always be annihilated.
     SubstToOrig,
   };

   static bool isBridgingKind(KindTy kind) {
     return kind <= LastBridgingKind;
   }

 private:
   KindTy Kind;

   struct BridgingTypes {
     CanType OrigType;
     CanType ResultType;
     SILType LoweredResultType;
     bool IsExplicit;
   };

   struct ReabstractionTypes {
     AbstractionPattern OrigType;
     CanType SubstType;
     SILType LoweredResultType;
   };

   using Members = ExternalUnionMembers<BridgingTypes, ReabstractionTypes>;

   static Members::Index getStorageIndexForKind(KindTy kind) {
     switch (kind) {
     case BridgeToObjC:
     case ForceAndBridgeToObjC:
     case BridgeFromObjC:
     case BridgeResultFromObjC:
     case AnyErasure:
       return Members::indexOf<BridgingTypes>();

     case OrigToSubst:
     case SubstToOrig:
       return Members::indexOf<ReabstractionTypes>();
     }
     llvm_unreachable("bad kind");
   }

   ExternalUnion<KindTy, Members, getStorageIndexForKind> Types;
   static_assert(decltype(Types)::union_is_trivially_copyable,
                 "define the special members if this changes");

   Conversion(KindTy kind, CanType origType, CanType resultType,
              SILType loweredResultTy, bool isExplicit)
       : Kind(kind) {
     Types.emplaceAggregate<BridgingTypes>(kind, origType, resultType,
                                           loweredResultTy, isExplicit);
   }

   Conversion(KindTy kind, AbstractionPattern origType, CanType substType,
              SILType loweredResultTy)
       : Kind(kind) {
     Types.emplaceAggregate<ReabstractionTypes>(kind, origType, substType,
                                                loweredResultTy);
   }

 public:
   static Conversion getOrigToSubst(AbstractionPattern origType,
                                    CanType substType,
                                    SILType loweredResultTy) {
     return Conversion(OrigToSubst, origType, substType, loweredResultTy);
   }

   static Conversion getSubstToOrig(AbstractionPattern origType,
                                    CanType substType,
                                    SILType loweredResultTy) {
     return Conversion(SubstToOrig, origType, substType, loweredResultTy);
   }

   static Conversion getBridging(KindTy kind, CanType origType,
                                 CanType resultType, SILType loweredResultTy,
                                 bool isExplicit = false) {
     assert(isBridgingKind(kind));
     return Conversion(kind, origType, resultType, loweredResultTy, isExplicit);
   }

   KindTy getKind() const {
     return Kind;
   }

   bool isBridging() const {
     return isBridgingKind(getKind());
   }

   AbstractionPattern getReabstractionOrigType() const {
     return Types.get<ReabstractionTypes>(Kind).OrigType;
   }

   CanType getReabstractionSubstType() const {
     return Types.get<ReabstractionTypes>(Kind).SubstType;
   }

   SILType getReabstractionLoweredResultType() const {
     return Types.get<ReabstractionTypes>(Kind).LoweredResultType;
   }

   bool isBridgingExplicit() const {
     return Types.get<BridgingTypes>(Kind).IsExplicit;
   }

   CanType getBridgingSourceType() const {
     return Types.get<BridgingTypes>(Kind).OrigType;
   }

   CanType getBridgingResultType() const {
     return Types.get<BridgingTypes>(Kind).ResultType;
   }

   SILType getBridgingLoweredResultType() const {
     return Types.get<BridgingTypes>(Kind).LoweredResultType;
   }

   ManagedValue emit(SILGenFunction &SGF, SILLocation loc,
                     ManagedValue source, SGFContext ctxt) const;

   /// Try to form a conversion that does an optional injection
   /// or optional-to-optional conversion followed by this conversion.
   Optional<Conversion>
   adjustForInitialOptionalConversions(CanType newSourceType) const;

   /// Try to form a conversion that does a force-value followed by
   /// this conversion.
   Optional<Conversion> adjustForInitialForceValue() const;

   void dump() const LLVM_ATTRIBUTE_USED;
   void print(llvm::raw_ostream &out) const;
 };

 /// Information about how to peephole two conversions.
 ///
 /// This is really the private state of SILGenConvert.
 class ConversionPeepholeHint {
 public:
   enum Kind : uint8_t {
     /// The value will be exactly the right type.
     Identity,

     /// The value needs to be bridged to AnyObject (possibly optionally).
     BridgeToAnyObject,

     /// The value just needs to undergo a subtype conversion.
     Subtype
   };

 private:
   Kind TheKind;
   bool Forced;

 public:
   ConversionPeepholeHint(Kind kind, bool forced)
     : TheKind(kind), Forced(forced) {
   }

   Kind getKind() const { return TheKind; }

   /// Does the value need to be forced before the conversion?
   /// This comes up with result conversions where the result was imported
   /// as non-optional, as well as with implicitly unwrapped optionals.
   bool isForced() const { return Forced; }
 };

 Optional<ConversionPeepholeHint>
 canPeepholeConversions(SILGenFunction &SGF,
                        const Conversion &outerConversion,
                        const Conversion &innerConversion);

 ManagedValue emitPeepholedConversions(SILGenFunction &SGF, SILLocation loc,
                                       const Conversion &outerConversion,
                                       const Conversion &innerConversion,
                                       ConversionPeepholeHint hint,
                                       SGFContext C,
                                       ValueProducerRef produceValue);

 /// An initialization where we ultimately want to apply a conversion to
 /// the value before completing the initialization.
 ///
 /// Value generators may call getAsConversion() to check whether an
 /// Initialization is one of these.  If so, they may call either
 /// tryPeephole or setConvertedValue.
 class ConvertingInitialization final : public Initialization {
 private:
   enum StateTy {
     /// Nothing has happened.
     Uninitialized,

     /// The converted value has been set.
     Initialized,

     /// finishInitialization has been called.
     Finished,

     /// The converted value has been extracted.
     Extracted
   };

   StateTy State;

   /// The conversion that needs to be applied to the formal value.
   Conversion TheConversion;

   /// The converted value, set if the initializing code calls tryPeephole,
   /// setReabstractedValue, or copyOrInitValueInto.
   ManagedValue Value;
   SGFContext FinalContext;

   StateTy getState() const {
     return State;
   }

 public:
   ConvertingInitialization(Conversion conversion, SGFContext finalContext)
     : State(Uninitialized), TheConversion(conversion),
       FinalContext(finalContext) {}

   /// Return the conversion to apply to the unconverted value.
   const Conversion &getConversion() const {
     return TheConversion;
   }

   /// Return the context into which to emit the converted value.
   SGFContext getFinalContext() const {
     return FinalContext;
   }

   // The three ways to perform this initialization:

   /// Set the unconverted value for this initialization.
   void copyOrInitValueInto(SILGenFunction &SGF, SILLocation loc,
                            ManagedValue value, bool isInit) override;

   /// Given that the result of the given expression needs to sequentially
   /// undergo the the given conversion and then this conversion, attempt to
   /// peephole the result.  If successful, the value will be set in this
   /// initialization.  The initialization will not yet be finished.
   bool tryPeephole(SILGenFunction &SGF, Expr *E, Conversion innerConversion);
   bool tryPeephole(SILGenFunction &SGF, SILLocation loc,
                    Conversion innerConversion, ValueProducerRef producer);
   bool tryPeephole(SILGenFunction &SGF, SILLocation loc, ManagedValue value,
                    Conversion innerConversion);

   /// Set the converted value for this initialization.
   void setConvertedValue(ManagedValue value) {
     assert(getState() == Uninitialized);
     assert(!value.isInContext() || FinalContext.getEmitInto());
     Value = value;
     State = Initialized;
   }

   /// Given that an emitter was able to adjust the conversion when
   /// emitting into this initialization, continue emission into the
   /// new conversion.
   ManagedValue emitWithAdjustedConversion(SILGenFunction &SGF, SILLocation loc,
                                           Conversion adjustedConversion,
                                           ValueProducerRef producer);

   /// Given the unconverted result, i.e. the result of emitting a
   /// value formally of the unconverted type with this initialization
   /// as the SGFContext, produce the converted result.
   ///
   /// If this initialization was initialized, the unconverted result
   /// must be ManagedValue::forInContext(), and vice-versa.
   ///
   /// The result of this function may itself be
   /// ManagedValue::forInContext() if this Initialization was created
   /// with an SGFContext which contains another Initialization.
   ManagedValue finishEmission(SILGenFunction &SGF, SILLocation loc,
                               ManagedValue formalResult);

   // Implement to make the cast work.
   ConvertingInitialization *getAsConversion() override {
     return this;
   }

   // Bookkeeping.
   void finishInitialization(SILGenFunction &SGF) override {
     assert(getState() == Initialized);
     State = Finished;
   }
 };

 } // end namespace Lowering
 } // end namespace swift

 #endif
	//===--- Conversion.h - Types for value conversion --------------- 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
	//
	//===----------------------------------------------------------------------===//
	//
	// Defines the Conversion class as well as ConvertingInitialization.
	//
	//===----------------------------------------------------------------------===//

	#ifndef SWIFT_LOWERING_CONVERSION_H
	#define SWIFT_LOWERING_CONVERSION_H

	#include "swift/Basic/ExternalUnion.h"
	#include "Initialization.h"
	#include "SGFContext.h"

	namespace swift {
	namespace Lowering {

	/// An abstraction representing certain kinds of conversion that SILGen can
	/// do automatically in various situations.
	class Conversion {
	public:
	enum KindTy {
	/// A bridging conversion to a foreign type.
	BridgeToObjC,

	/// A bridging conversion to a foreign type following a force.
	/// Although it's not reflected in the name, this is always an
	/// implicit force cast.
	ForceAndBridgeToObjC,

	/// A bridging conversion from a foreign type.
	BridgeFromObjC,

	/// A bridging conversion for a function result.
	BridgeResultFromObjC,

	/// An erasure to Any (possibly wrapped in optional conversions).
	/// This is sortof a bridging conversion.
	AnyErasure,

	LastBridgingKind = AnyErasure,

	/// An orig-to-subst conversion.
	OrigToSubst,

	/// A subst-to-orig conversion. These can always be annihilated.
	SubstToOrig,
	};

	static bool isBridgingKind(KindTy kind) {
	return kind <= LastBridgingKind;
	}

	private:
	KindTy Kind;

	struct BridgingTypes {
	CanType OrigType;
	CanType ResultType;
	SILType LoweredResultType;
	bool IsExplicit;
	};

	struct ReabstractionTypes {
	AbstractionPattern OrigType;
	CanType SubstType;
	SILType LoweredResultType;
	};

	using Members = ExternalUnionMembers<BridgingTypes, ReabstractionTypes>;

	static Members::Index getStorageIndexForKind(KindTy kind) {
	switch (kind) {
	case BridgeToObjC:
	case ForceAndBridgeToObjC:
	case BridgeFromObjC:
	case BridgeResultFromObjC:
	case AnyErasure:
	return Members::indexOf<BridgingTypes>();

	case OrigToSubst:
	case SubstToOrig:
	return Members::indexOf<ReabstractionTypes>();
	}
	llvm_unreachable("bad kind");
	}

	ExternalUnion<KindTy, Members, getStorageIndexForKind> Types;
	static_assert(decltype(Types)::union_is_trivially_copyable,
	"define the special members if this changes");

	Conversion(KindTy kind, CanType origType, CanType resultType,
	SILType loweredResultTy, bool isExplicit)
	: Kind(kind) {
	Types.emplaceAggregate<BridgingTypes>(kind, origType, resultType,
	loweredResultTy, isExplicit);
	}

	Conversion(KindTy kind, AbstractionPattern origType, CanType substType,
	SILType loweredResultTy)
	: Kind(kind) {
	Types.emplaceAggregate<ReabstractionTypes>(kind, origType, substType,
	loweredResultTy);
	}

	public:
	static Conversion getOrigToSubst(AbstractionPattern origType,
	CanType substType,
	SILType loweredResultTy) {
	return Conversion(OrigToSubst, origType, substType, loweredResultTy);
	}

	static Conversion getSubstToOrig(AbstractionPattern origType,
	CanType substType,
	SILType loweredResultTy) {
	return Conversion(SubstToOrig, origType, substType, loweredResultTy);
	}

	static Conversion getBridging(KindTy kind, CanType origType,
	CanType resultType, SILType loweredResultTy,
	bool isExplicit = false) {
	assert(isBridgingKind(kind));
	return Conversion(kind, origType, resultType, loweredResultTy, isExplicit);
	}

	KindTy getKind() const {
	return Kind;
	}

	bool isBridging() const {
	return isBridgingKind(getKind());
	}

	AbstractionPattern getReabstractionOrigType() const {
	return Types.get<ReabstractionTypes>(Kind).OrigType;
	}

	CanType getReabstractionSubstType() const {
	return Types.get<ReabstractionTypes>(Kind).SubstType;
	}

	SILType getReabstractionLoweredResultType() const {
	return Types.get<ReabstractionTypes>(Kind).LoweredResultType;
	}

	bool isBridgingExplicit() const {
	return Types.get<BridgingTypes>(Kind).IsExplicit;
	}

	CanType getBridgingSourceType() const {
	return Types.get<BridgingTypes>(Kind).OrigType;
	}

	CanType getBridgingResultType() const {
	return Types.get<BridgingTypes>(Kind).ResultType;
	}

	SILType getBridgingLoweredResultType() const {
	return Types.get<BridgingTypes>(Kind).LoweredResultType;
	}

	ManagedValue emit(SILGenFunction &SGF, SILLocation loc,
	ManagedValue source, SGFContext ctxt) const;

	/// Try to form a conversion that does an optional injection
	/// or optional-to-optional conversion followed by this conversion.
	Optional<Conversion>
	adjustForInitialOptionalConversions(CanType newSourceType) const;

	/// Try to form a conversion that does a force-value followed by
	/// this conversion.
	Optional<Conversion> adjustForInitialForceValue() const;

	void dump() const LLVM_ATTRIBUTE_USED;
	void print(llvm::raw_ostream &out) const;
	};

	/// Information about how to peephole two conversions.
	///
	/// This is really the private state of SILGenConvert.
	class ConversionPeepholeHint {
	public:
	enum Kind : uint8_t {
	/// The value will be exactly the right type.
	Identity,

	/// The value needs to be bridged to AnyObject (possibly optionally).
	BridgeToAnyObject,

	/// The value just needs to undergo a subtype conversion.
	Subtype
	};

	private:
	Kind TheKind;
	bool Forced;

	public:
	ConversionPeepholeHint(Kind kind, bool forced)
	: TheKind(kind), Forced(forced) {
	}

	Kind getKind() const { return TheKind; }

	/// Does the value need to be forced before the conversion?
	/// This comes up with result conversions where the result was imported
	/// as non-optional, as well as with implicitly unwrapped optionals.
	bool isForced() const { return Forced; }
	};

	Optional<ConversionPeepholeHint>
	canPeepholeConversions(SILGenFunction &SGF,
	const Conversion &outerConversion,
	const Conversion &innerConversion);

	ManagedValue emitPeepholedConversions(SILGenFunction &SGF, SILLocation loc,
	const Conversion &outerConversion,
	const Conversion &innerConversion,
	ConversionPeepholeHint hint,
	SGFContext C,
	ValueProducerRef produceValue);

	/// An initialization where we ultimately want to apply a conversion to
	/// the value before completing the initialization.
	///
	/// Value generators may call getAsConversion() to check whether an
	/// Initialization is one of these. If so, they may call either
	/// tryPeephole or setConvertedValue.
	class ConvertingInitialization final : public Initialization {
	private:
	enum StateTy {
	/// Nothing has happened.
	Uninitialized,

	/// The converted value has been set.
	Initialized,

	/// finishInitialization has been called.
	Finished,

	/// The converted value has been extracted.
	Extracted
	};

	StateTy State;

	/// The conversion that needs to be applied to the formal value.
	Conversion TheConversion;

	/// The converted value, set if the initializing code calls tryPeephole,
	/// setReabstractedValue, or copyOrInitValueInto.
	ManagedValue Value;
	SGFContext FinalContext;

	StateTy getState() const {
	return State;
	}

	public:
	ConvertingInitialization(Conversion conversion, SGFContext finalContext)
	: State(Uninitialized), TheConversion(conversion),
	FinalContext(finalContext) {}

	/// Return the conversion to apply to the unconverted value.
	const Conversion &getConversion() const {
	return TheConversion;
	}

	/// Return the context into which to emit the converted value.
	SGFContext getFinalContext() const {
	return FinalContext;
	}

	// The three ways to perform this initialization:

	/// Set the unconverted value for this initialization.
	void copyOrInitValueInto(SILGenFunction &SGF, SILLocation loc,
	ManagedValue value, bool isInit) override;

	/// Given that the result of the given expression needs to sequentially
	/// undergo the the given conversion and then this conversion, attempt to
	/// peephole the result. If successful, the value will be set in this
	/// initialization. The initialization will not yet be finished.
	bool tryPeephole(SILGenFunction &SGF, Expr *E, Conversion innerConversion);
	bool tryPeephole(SILGenFunction &SGF, SILLocation loc,
	Conversion innerConversion, ValueProducerRef producer);
	bool tryPeephole(SILGenFunction &SGF, SILLocation loc, ManagedValue value,
	Conversion innerConversion);

	/// Set the converted value for this initialization.
	void setConvertedValue(ManagedValue value) {
	assert(getState() == Uninitialized);
	assert(!value.isInContext() \|\| FinalContext.getEmitInto());
	Value = value;
	State = Initialized;
	}

	/// Given that an emitter was able to adjust the conversion when
	/// emitting into this initialization, continue emission into the
	/// new conversion.
	ManagedValue emitWithAdjustedConversion(SILGenFunction &SGF, SILLocation loc,
	Conversion adjustedConversion,
	ValueProducerRef producer);

	/// Given the unconverted result, i.e. the result of emitting a
	/// value formally of the unconverted type with this initialization
	/// as the SGFContext, produce the converted result.
	///
	/// If this initialization was initialized, the unconverted result
	/// must be ManagedValue::forInContext(), and vice-versa.
	///
	/// The result of this function may itself be
	/// ManagedValue::forInContext() if this Initialization was created
	/// with an SGFContext which contains another Initialization.
	ManagedValue finishEmission(SILGenFunction &SGF, SILLocation loc,
	ManagedValue formalResult);

	// Implement to make the cast work.
	ConvertingInitialization *getAsConversion() override {
	return this;
	}

	// Bookkeeping.
	void finishInitialization(SILGenFunction &SGF) override {
	assert(getState() == Initialized);
	State = Finished;
	}
	};

	} // end namespace Lowering
	} // end namespace swift

	#endif