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//===--- StructMetadataVisitor.h - CRTP for struct metadata ------*- 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
//
//===----------------------------------------------------------------------===//
//
// A CRTP class useful for laying out struct metadata.
//
//===----------------------------------------------------------------------===//
#ifndef SWIFT_IRGEN_STRUCTMETADATALAYOUT_H
#define SWIFT_IRGEN_STRUCTMETADATALAYOUT_H
#include "NominalMetadataVisitor.h"
#include "swift/AST/IRGenOptions.h"
namespace swift {
namespace irgen {
/// A CRTP class for laying out struct metadata.
///
/// This produces an object corresponding to the StructMetadata type.
/// It does not itself doing anything special for metadata templates.
template <class Impl> class StructMetadataVisitor
: public NominalMetadataVisitor<Impl> {
using super = NominalMetadataVisitor<Impl>;
protected:
using super::IGM;
using super::asImpl;
/// The struct.
StructDecl *const Target;
StructMetadataVisitor(IRGenModule &IGM, StructDecl *target)
: super(IGM), Target(target) {}
public:
void layout() {
static_assert(MetadataAdjustmentIndex::ValueType == 2,
"Adjustment index must be synchronized with this layout");
asImpl().addLayoutStringPointer();
// Metadata header.
super::layout();
// StructMetadata header.
asImpl().addNominalTypeDescriptor();
// Everything after this is type-specific.
asImpl().noteStartOfTypeSpecificMembers();
// Generic arguments.
// This must always be the first piece of trailing data.
asImpl().addGenericFields(Target);
// Struct field offsets.
asImpl().noteStartOfFieldOffsets();
for (VarDecl *prop : Target->getStoredProperties())
asImpl().addFieldOffset(prop);
asImpl().noteEndOfFieldOffsets();
if (asImpl().hasTrailingFlags())
asImpl().addTrailingFlags();
}
// Note the start of the field offset vector.
void noteStartOfFieldOffsets() {}
// Note the end of the field offset vector.
void noteEndOfFieldOffsets() {}
bool hasTrailingFlags() {
return Target->isGenericContext() &&
IGM.shouldPrespecializeGenericMetadata();
}
};
/// An "implementation" of StructMetadataVisitor that just scans through
/// the metadata layout, maintaining the offset of the next field.
template <class Impl>
class StructMetadataScanner : public StructMetadataVisitor<Impl> {
using super = StructMetadataVisitor<Impl>;
protected:
Size NextOffset = Size(0);
StructMetadataScanner(IRGenModule &IGM, StructDecl *target)
: super(IGM, target) {}
public:
void addMetadataFlags() { addPointer(); }
void addLayoutStringPointer() { addPointer(); }
void addValueWitnessTable() { addPointer(); }
void addNominalTypeDescriptor() { addPointer(); }
void addFieldOffset(VarDecl *) { addInt32(); }
void addGenericRequirement(GenericRequirement requirement) { addPointer(); }
void noteStartOfTypeSpecificMembers() {}
void noteEndOfFieldOffsets() {
NextOffset = NextOffset.roundUpToAlignment(super::IGM.getPointerAlignment());
}
void addTrailingFlags() { addInt64(); }
private:
void addPointer() {
NextOffset += super::IGM.getPointerSize();
}
void addInt32() { NextOffset += Size(4); }
void addInt64() { NextOffset += Size(8); }
};
} // end namespace irgen
} // end namespace swift
#endif
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