mirror of
https://github.com/apple/swift.git
synced 2026-06-20 15:42:51 +02:00
Dario Rexin
5b0da23150
rdar://158239258 This change adds logic in the compiler to compute malloc type ids and emit them together with typed allocation calls. It also adds the new runtime function swift_allocObjectTyped, which calls typed malloc.
117 lines
4.3 KiB
C++
117 lines
4.3 KiB
C++
//===--- ClassLayout.cpp - Layout of class instances ---------------------===//
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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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// This file implements algorithms for laying out class instances.
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//
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//===----------------------------------------------------------------------===//
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#include "swift/AST/ASTContext.h"
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#include "swift/SIL/SILType.h"
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#include "llvm/ADT/SmallVector.h"
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#include "ClassLayout.h"
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#include "GenHeap.h"
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#include "IRGenFunction.h"
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#include "IRGenModule.h"
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#include "TypeInfo.h"
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using namespace swift;
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using namespace irgen;
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ClassLayout::ClassLayout(const StructLayoutBuilder &builder,
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ClassMetadataOptions options,
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llvm::Type *classTy,
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ArrayRef<Field> allStoredProps,
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ArrayRef<FieldAccess> allFieldAccesses,
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ArrayRef<ElementLayout> allElements,
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Size headerSize)
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: MinimumAlign(builder.getAlignment()),
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MinimumSize(builder.getSize()),
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IsFixedLayout(builder.isFixedLayout()),
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Options(options),
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Ty(classTy),
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HeaderSize(headerSize),
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AllStoredProperties(allStoredProps),
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AllFieldAccesses(allFieldAccesses),
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AllElements(allElements) { }
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Size ClassLayout::getInstanceStart() const {
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ArrayRef<ElementLayout> elements = AllElements;
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while (!elements.empty()) {
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auto element = elements.front();
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elements = elements.drop_front();
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// Ignore empty elements.
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if (element.isEmpty()) {
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continue;
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} else if (element.hasByteOffset()) {
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// FIXME: assumes layout is always sequential!
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return element.getByteOffset();
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} else {
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// We used to crash for classes that have an empty and a resilient field
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// during initialization.
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// class CrashInInit {
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// var empty = EmptyStruct()
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// var resilient = ResilientThing()
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// }
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// What happened was that for such a class we we would compute a
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// instanceStart of 0. The shared cache builder would then slide the value
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// of the constant ivar offset for the empty field from 0 to 16. However
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// the field offset for empty fields is assume to be zero and the runtime
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// does not compute a different value for the empty field and so the field
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// offset for the empty field stays 0. The runtime then trys to reconcile
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// the field offset and the ivar offset trying to write to the ivar
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// offset. However, the ivar offset is marked as constant and so we
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// crashed.
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// This can be avoided by correctly computing the instanceStart for such a
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// class to be 16 such that the shared cache builder does not update the
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// value of the empty field.
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if (!Options.contains(ClassMetadataFlags::ClassHasObjCAncestry))
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return HeaderSize;
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return Size(0);
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}
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}
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// If there are no non-empty elements, just return the computed size.
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return getSize();
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}
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std::optional<uint64_t>
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ClassLayout::computeTypedMallocTypeDescriptor(IRGenModule &IGM,
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SILType selfType) const {
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if (!isFixedSize()) {
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return std::nullopt;
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}
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llvm::SmallVector<SILType> storageEntries;
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auto rawPointerType = SILType::getRawPointerType(IGM.Context);
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// Add the heap header as the first entry
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if (hasObjCImplementation()) {
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storageEntries.push_back(rawPointerType);
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} else if (!HeaderSize.isZero()) {
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assert(HeaderSize == IGM.RefCountedStructSize &&
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"Swift object with non-standard header size");
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storageEntries.push_back(rawPointerType);
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storageEntries.push_back(rawPointerType);
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}
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// Add entries for each stored property
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for (auto field : AllStoredProperties) {
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assert(field.isConcrete() && "Missing member on fixed size class");
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auto fieldType = field.getType(IGM, selfType).getObjectType();
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storageEntries.push_back(fieldType);
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}
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return irgen::computeTypedMallocTypeDescriptor(IGM, storageEntries);
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}
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