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John McCall
dff0031b02
The layout changes to become relative-address based. For this to be truly immutable (at least on Darwin), things like the RO data patterns must be moved out of the pattern header. Additionally, compress the pattern header so that we do not include metadata about patterns that are not needed for the type. Value metadata patterns just include the metadata kind and VWT. The design here is meant to accomodate non-default instantiation patterns should that become an interesting thing to support in the future, e.g. for v-table specialization.
100 lines
2.9 KiB
C++
100 lines
2.9 KiB
C++
//===--- StructMetadataVisitor.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 - 2017 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 https://swift.org/LICENSE.txt for license information
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// See https://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 "NominalMetadataVisitor.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 StructMetadataVisitor
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: public NominalMetadataVisitor<Impl> {
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using super = NominalMetadataVisitor<Impl>;
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protected:
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using super::IGM;
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using super::asImpl;
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/// The struct.
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StructDecl *const Target;
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StructMetadataVisitor(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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// Everything after this is type-specific.
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asImpl().noteStartOfTypeSpecificMembers();
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// Generic arguments.
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// This must always be the first piece of trailing data.
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asImpl().addGenericFields(Target, Target->getDeclaredTypeInContext());
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// Struct field offsets.
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asImpl().noteStartOfFieldOffsets();
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for (VarDecl *prop : Target->getStoredProperties())
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asImpl().addFieldOffset(prop);
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}
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// Note the start of the field offset vector.
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void noteStartOfFieldOffsets() {}
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};
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/// An "implementation" of StructMetadataVisitor that just scans through
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/// the metadata layout, maintaining the offset of the next field.
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template <class Impl>
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class StructMetadataScanner : public StructMetadataVisitor<Impl> {
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typedef StructMetadataVisitor<Impl> super;
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protected:
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Size NextOffset = Size(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() { addPointer(); }
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void addValueWitnessTable() { addPointer(); }
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void addNominalTypeDescriptor() { addPointer(); }
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void addFieldOffset(VarDecl*) { addPointer(); }
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void addGenericArgument(CanType argument) { addPointer(); }
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void addGenericWitnessTable(CanType argument, ProtocolConformanceRef conf) {
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addPointer();
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}
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void noteStartOfTypeSpecificMembers() {}
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private:
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void addPointer() {
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NextOffset += super::IGM.getPointerSize();
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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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