[SIL] InitAccessors: Add tracking of properties that require assign instead of initialization

Some properties from `initializes(...)` list could be already initialized,
which means that Raw SIL lowering has to emit `destroy_addr` for them
before calling init accessor.

Author: xedin

include/swift/AST/Attr.h

@@ -1568,6 +1568,8 @@ class InitializesAttr final
     return numProperties;
   }
 
+  unsigned getNumProperties() const { return numProperties; }
+
   ArrayRef<Identifier> getProperties() const {
     return {getTrailingObjects<Identifier>(), numProperties};
   }

include/swift/SIL/SILInstruction.h

@@ -4951,6 +4951,11 @@ class AssignOrInitInst
 
   FixedOperandList<3> Operands;
 
+  /// Marks all of the properties in `initializes(...)` list that
+  /// have been initialized before this intruction to help Raw SIL
+  /// lowering to emit destroys.
+  llvm::BitVector Assignments;
+
 public:
   enum Mode {
     /// The mode is not decided yet (by DefiniteInitialization).
@@ -4981,6 +4986,17 @@ class AssignOrInitInst
     sharedUInt8().AssignOrInitInst.mode = uint8_t(mode);
   }
 
+  /// Mark a property from `initializes(...)` list as initialized
+  /// before this instruction.
+  void markAsInitialized(VarDecl *property);
+
+  /// Check whether a property from `initializes(...)` list with
+  /// the given index has already been initialized and requires
+  /// destroy before it could be re-initialized.
+  bool isPropertyAlreadyInitialized(unsigned propertyIdx);
+
+  unsigned getNumInitializedProperties() const;
+
   ArrayRef<VarDecl *> getInitializedProperties() const;
   ArrayRef<VarDecl *> getAccessedProperties() const;
 

lib/SIL/IR/SILInstructions.cpp

@@ -1263,27 +1263,51 @@ AssignOrInitInst::AssignOrInitInst(SILDebugLocation Loc, SILValue Src,
       Operands(this, Src, Initializer, Setter) {
   assert(Initializer->getType().is<SILFunctionType>());
   sharedUInt8().AssignOrInitInst.mode = uint8_t(Mode);
+  Assignments.resize(getNumInitializedProperties());
+}
+
+void AssignOrInitInst::markAsInitialized(VarDecl *property) {
+  auto toInitProperties = getInitializedProperties();
+  for (unsigned index : indices(toInitProperties)) {
+    if (toInitProperties[index] == property) {
+      Assignments.set(index);
+      break;
+    }
+  }
+}
+
+bool AssignOrInitInst::isPropertyAlreadyInitialized(unsigned propertyIdx) {
+  assert(propertyIdx < Assignments.size());
+  return Assignments.test(propertyIdx);
 }
 
 AccessorDecl *AssignOrInitInst::getReferencedInitAccessor() const {
-  auto *initRef =
-      cast<FunctionRefInst>(getInitializer()->getDefiningInstruction());
-  auto *accessorRef = initRef->getReferencedFunction();
-  return cast<AccessorDecl>(accessorRef->getDeclContext());
+  auto *initRef = cast<FunctionRefInst>(getInitializer());
+  auto *accessorRef = initRef->getReferencedFunctionOrNull();
+  assert(accessorRef);
+  return dyn_cast_or_null<AccessorDecl>(accessorRef->getDeclContext());
+}
+
+unsigned AssignOrInitInst::getNumInitializedProperties() const {
+  if (auto *accessor = getReferencedInitAccessor()) {
+    auto *initAttr = accessor->getAttrs().getAttribute<InitializesAttr>();
+    return initAttr ? initAttr->getNumProperties() : 0;
+  }
+  return 0;
 }
 
 ArrayRef<VarDecl *> AssignOrInitInst::getInitializedProperties() const {
-  auto *accessor = getReferencedInitAccessor();
-  if (auto *initAttr = accessor->getAttrs().getAttribute<InitializesAttr>()) {
-    return initAttr->getPropertyDecls(accessor);
+  if (auto *accessor = getReferencedInitAccessor()) {
+    if (auto *initAttr = accessor->getAttrs().getAttribute<InitializesAttr>())
+      return initAttr->getPropertyDecls(accessor);
   }
   return {};
 }
 
 ArrayRef<VarDecl *> AssignOrInitInst::getAccessedProperties() const {
-  auto *accessor = getReferencedInitAccessor();
-  if (auto *accessAttr = accessor->getAttrs().getAttribute<AccessesAttr>()) {
-    return accessAttr->getPropertyDecls(accessor);
+  if (auto *accessor = getReferencedInitAccessor()) {
+    if (auto *accessAttr = accessor->getAttrs().getAttribute<AccessesAttr>())
+      return accessAttr->getPropertyDecls(accessor);
   }
   return {};
 }