More class layout cleanups and a better fix for SR-4687

lib/IRGen/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_swift_library(swiftIRGen STATIC
   AllocStackHoisting.cpp
+  ClassLayout.cpp
   DebugTypeInfo.cpp
   EnumPayload.cpp
   ExtraInhabitants.cpp

lib/IRGen/ClassLayout.cpp

@@ -0,0 +1,56 @@
+//===--- ClassLayout.cpp - Layout of class instances ---------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements algorithms for laying out class instances.
+//
+//===----------------------------------------------------------------------===//
+
+#include "swift/AST/ASTContext.h"
+
+#include "IRGenFunction.h"
+#include "IRGenModule.h"
+#include "ClassLayout.h"
+#include "TypeInfo.h"
+
+using namespace swift;
+using namespace irgen;
+
+ClassLayout::ClassLayout(const StructLayoutBuilder &builder,
+                         bool isFixedSize,
+                         bool metadataRequiresDynamicInitialization,
+                         llvm::Type *classTy,
+                         ArrayRef<VarDecl *> allStoredProps,
+                         ArrayRef<FieldAccess> allFieldAccesses,
+                         ArrayRef<ElementLayout> allElements)
+  : MinimumAlign(builder.getAlignment()),
+    MinimumSize(builder.getSize()),
+    IsFixedLayout(builder.isFixedLayout()),
+    IsFixedSize(isFixedSize),
+    MetadataRequiresDynamicInitialization(metadataRequiresDynamicInitialization),
+    Ty(classTy),
+    AllStoredProperties(allStoredProps),
+    AllFieldAccesses(allFieldAccesses),
+    AllElements(allElements) { }
+
+Size ClassLayout::getInstanceStart() const {
+  if (AllElements.empty())
+    return getSize();
+
+  auto element = AllElements[0];
+  if (element.getKind() == ElementLayout::Kind::Fixed ||
+      element.getKind() == ElementLayout::Kind::Empty) {
+    // FIXME: assumes layout is always sequential!
+    return element.getByteOffset();
+  }
+
+  return Size(0);
+}

lib/IRGen/ClassLayout.h

@@ -0,0 +1,116 @@
+//===--- ClassLayout.h - Class instance layout ------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines some routines that are useful for calculating class
+// instance layout.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_IRGEN_CLASSLAYOUT_H
+#define SWIFT_IRGEN_CLASSLAYOUT_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "IRGen.h"
+#include "StructLayout.h"
+
+namespace swift {
+namespace irgen {
+
+/// Different policies for accessing a physical field.
+enum class FieldAccess : uint8_t {
+  /// Instance variable offsets are constant.
+  ConstantDirect,
+
+  /// Instance variable offsets must be loaded from "direct offset"
+  /// global variables.
+  NonConstantDirect,
+
+  /// Instance variable offsets are kept in fields in metadata, but
+  /// the offsets of those fields within the metadata are constant.
+  ConstantIndirect
+};
+
+class ClassLayout {
+  /// The statically-known minimum bound on the alignment.
+  Alignment MinimumAlign;
+
+  /// The statically-known minimum bound on the size.
+  Size MinimumSize;
+
+  /// Whether this layout is fixed in size. If so, the size and
+  /// alignment are exact.
+  bool IsFixedLayout;
+
+  /// Do instances of this class have a size and layout known at compile time?
+  ///
+  /// Note: This is a stronger condition than having a fixed layout. The latter
+  /// is true even when the class requires sliding ivars by the Objective-C
+  /// runtime.
+  bool IsFixedSize;
+
+  /// Does the class metadata require dynamic initialization?
+  bool MetadataRequiresDynamicInitialization;
+
+  /// The LLVM type for instances of this class.
+  llvm::Type *Ty;
+
+  /// Lazily-initialized array of all fragile stored properties directly defined
+  /// in the class itself.
+  ArrayRef<VarDecl *> AllStoredProperties;
+
+  /// Lazily-initialized array of all field access methods.
+  ArrayRef<FieldAccess> AllFieldAccesses;
+
+  /// Fixed offsets of fields, if known (does not take Objective-C sliding into
+  /// account).
+  ArrayRef<ElementLayout> AllElements;
+
+public:
+  ClassLayout(const StructLayoutBuilder &builder,
+              bool isFixedSize,
+              bool metadataRequiresDynamicInitialization,
+              llvm::Type *classTy,
+              ArrayRef<VarDecl *> allStoredProps,
+              ArrayRef<FieldAccess> allFieldAccesses,
+              ArrayRef<ElementLayout> allElements);
+
+  Size getInstanceStart() const;
+
+  llvm::Type *getType() const { return Ty; }
+  Size getSize() const { return MinimumSize; }
+  Alignment getAlignment() const { return MinimumAlign; }
+  Size getAlignMask() const { return getAlignment().asSize() - Size(1); }
+
+  bool isFixedLayout() const { return IsFixedLayout; }
+
+  bool isFixedSize() const { return IsFixedSize; }
+
+  bool doesMetadataRequireDynamicInitialization() const {
+    return MetadataRequiresDynamicInitialization;
+  }
+
+  std::pair<FieldAccess, ElementLayout>
+  getFieldAccessAndElement(VarDecl *field) const {
+    // FIXME: This is algorithmically terrible.
+    auto found = std::find(AllStoredProperties.begin(),
+                           AllStoredProperties.end(), field);
+    assert(found != AllStoredProperties.end() && "didn't find field in type?!");
+    unsigned index = found - AllStoredProperties.begin();
+
+    return std::make_pair(AllFieldAccesses[index], AllElements[index]);
+  }
+};
+
+} // end namespace irgen
+} // end namespace swift
+
+#endif