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of a class is part of the class members section and is not global to the entire class metadata. This is crucial for correct operation of functions expecting a base-class metadata object. That gives us the correct foundation to implement an optimization under which generic arguments that can be inferred from the 'this' pointer need not actually be separately passed. This has the important result of making all class member functions with the same signature up to abstraction actually have the same physical signature. Swift SVN r2936
89 lines
2.6 KiB
C++
89 lines
2.6 KiB
C++
//===--- StructMetadataLayout.h - CRTP for struct metadata ------*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// A CRTP class useful for laying out struct metadata.
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//
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//===----------------------------------------------------------------------===//
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#ifndef SWIFT_IRGEN_STRUCTMETADATALAYOUT_H
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#define SWIFT_IRGEN_STRUCTMETADATALAYOUT_H
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#include "MetadataLayout.h"
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namespace swift {
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namespace irgen {
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/// A CRTP class for laying out struct metadata.
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///
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/// This produces an object corresponding to the StructMetadata type.
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/// It does not itself doing anything special for metadata templates.
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template <class Impl> class StructMetadataLayout : public MetadataLayout<Impl> {
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typedef MetadataLayout<Impl> super;
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protected:
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using super::IGM;
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using super::asImpl;
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/// The most-derived class.
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StructDecl *const Target;
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StructMetadataLayout(IRGenModule &IGM, StructDecl *target)
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: super(IGM), Target(target) {}
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public:
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void layout() {
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// Metadata header.
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super::layout();
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// StructMetadata header.
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asImpl().addNominalTypeDescriptor();
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asImpl().addParentMetadataRef();
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// If changing this layout, you must update the magic number in
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// emitParentMetadataRef.
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// Instantiation-specific.
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if (auto generics = Target->getGenericParamsOfContext()) {
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this->addGenericFields(*generics);
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}
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}
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};
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/// An "implementation" of StructMetadataLayout that just scans through
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/// the metadata layout, maintaining the next index: the offset (in
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/// pointer-sized chunks) into the metadata for the next field.
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template <class Impl>
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class StructMetadataScanner : public StructMetadataLayout<Impl> {
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typedef StructMetadataLayout<Impl> super;
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protected:
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unsigned NextIndex = 0;
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StructMetadataScanner(IRGenModule &IGM, StructDecl *target)
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: super(IGM, target) {}
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public:
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void addMetadataFlags() { NextIndex++; }
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void addValueWitnessTable() { NextIndex++; }
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void addNominalTypeDescriptor() { NextIndex++; }
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void addParentMetadataRef() { NextIndex++; }
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void addGenericArgument(ArchetypeType *argument) { NextIndex++; }
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void addGenericWitnessTable(ArchetypeType *argument,
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ProtocolDecl *protocol) {
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NextIndex++;
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}
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};
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} // end namespace irgen
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} // end namespace swift
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#endif
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