[builtins] Introduce DeleteProperty builtin

src/builtins/builtins-internal-gen.cc

 // Copyright 2017 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/builtins/builtins-utils-gen.h"
 #include "src/builtins/builtins.h"
 #include "src/code-stub-assembler.h"
 #include "src/macro-assembler.h"
 #include "src/runtime/runtime.h"
 
@@ skipping 146 matching lines @@
     // Allocate in old space (or large object space).
     TailCallRuntime(Runtime::kNewArgumentsElements, NoContextConstant(),
                     BitcastWordToTagged(frame), SmiFromWord(length));
   }
 }
 
 TF_BUILTIN(ReturnReceiver, CodeStubAssembler) {
   Return(Parameter(Descriptor::kReceiver));
 }
 
+class DeletePropertyBaseAssembler : public CodeStubAssembler {
+ public:
+  explicit DeletePropertyBaseAssembler(compiler::CodeAssemblerState* state)
+      : CodeStubAssembler(state) {}
+
+  void DeleteDictionaryProperty(Node* receiver, Node* properties, Node* name,
+                                Node* context, Label* dont_delete,
+                                Label* notfound) {
+    VARIABLE(var_name_index, MachineType::PointerRepresentation());
+    Label dictionary_found(this, &var_name_index);
+    NameDictionaryLookup<NameDictionary>(properties, name, &dictionary_found,
+                                         &var_name_index, notfound);
+
+    BIND(&dictionary_found);
+    Node* key_index = var_name_index.value();
+    Node* details =
+        LoadDetailsByKeyIndex<NameDictionary>(properties, key_index);
+    GotoIf(IsSetWord32(details, PropertyDetails::kAttributesDontDeleteMask),
+           dont_delete);
+    // Overwrite the entry itself (see NameDictionary::SetEntry).
+    Node* filler = TheHoleConstant();
+    StoreFixedArrayElement(properties, key_index, filler);

[Igor Sheludko, 2017/04/20 09:18:42]

TheHoleValue is in IMMORTAL_IMMOVABLE_ROOT_LIST so we can skip write barrier
here

[Jakob Kummerow, 2017/04/20 09:52:34]

Done.

+    StoreValueByKeyIndex<NameDictionary>(properties, key_index, filler);

[Igor Sheludko, 2017/04/20 09:18:42]

and here.

[Jakob Kummerow, 2017/04/20 09:52:34]

Done.

+    StoreDetailsByKeyIndex<NameDictionary>(properties, key_index,
+                                           SmiConstant(Smi::kZero));
+
+    // Update bookkeeping information (see NameDictionary::ElementRemoved).
+    Node* nof = GetNumberOfElements<NameDictionary>(properties);
+    Node* new_nof = SmiSub(nof, SmiConstant(1));
+    SetNumberOfElements<NameDictionary>(properties, new_nof);
+    Node* num_deleted = GetNumberOfDeletedElements<NameDictionary>(properties);
+    Node* new_deleted = SmiAdd(num_deleted, SmiConstant(1));
+    SetNumberOfDeletedElements<NameDictionary>(properties, new_deleted);
+
+    // Shrink the dictionary if necessary (see NameDictionary::Shrink).
+    Label shrinking_done(this);
+    Node* capacity = GetCapacity<NameDictionary>(properties);
+    GotoIf(SmiGreaterThan(new_nof, SmiShr(capacity, 2)), &shrinking_done);
+    GotoIf(SmiLessThan(new_nof, SmiConstant(16)), &shrinking_done);
+    CallRuntime(Runtime::kShrinkPropertyDictionary, context, receiver, name);
+    Goto(&shrinking_done);
+    BIND(&shrinking_done);
+
+    Return(TrueConstant());
+  }
+};
+
+TF_BUILTIN(DeleteProperty, DeletePropertyBaseAssembler) {
+  Node* receiver = Parameter(Descriptor::kObject);
+  Node* key = Parameter(Descriptor::kKey);
+  Node* language_mode = Parameter(Descriptor::kLanguageMode);
+  Node* context = Parameter(Descriptor::kContext);
+
+  VARIABLE(var_index, MachineType::PointerRepresentation());
+  VARIABLE(var_unique, MachineRepresentation::kTagged, key);
+  Label if_index(this), if_unique_name(this), if_notunique(this),
+      if_notfound(this), slow(this);
+
+  GotoIf(TaggedIsSmi(receiver), &slow);
+  Node* receiver_map = LoadMap(receiver);
+  Node* instance_type = LoadMapInstanceType(receiver_map);
+  GotoIf(Int32LessThanOrEqual(instance_type,
+                              Int32Constant(LAST_CUSTOM_ELEMENTS_RECEIVER)),
+         &slow);
+  TryToName(key, &if_index, &var_index, &if_unique_name, &var_unique, &slow,
+            &if_notunique);
+
+  BIND(&if_index);
+  {
+    Comment("integer index");
+    Goto(&slow);  // TODO(jkummerow): Implement more smarts here.
+  }
+
+  BIND(&if_unique_name);
+  {
+    Comment("key is unique name");
+    Node* unique = var_unique.value();
+    CheckForAssociatedProtector(unique, &slow);
+
+    Label dictionary(this), dont_delete(this);
+    Node* properties = LoadProperties(receiver);
+    Node* properties_map = LoadMap(properties);
+    GotoIf(WordEqual(properties_map, LoadRoot(Heap::kHashTableMapRootIndex)),
+           &dictionary);
+    // TODO(jkummerow): Implement support for fast properties?
+    Goto(&slow);
+
+    BIND(&dictionary);
+    {
+      DeleteDictionaryProperty(receiver, properties, unique, context,
+                               &dont_delete, &if_notfound);
+    }
+
+    BIND(&dont_delete);
+    {
+      GotoIf(SmiEqual(language_mode, SmiConstant(STRICT)), &slow);

[Igor Sheludko, 2017/04/20 09:18:42]

is_strict(lm) is implemented as lm != SLOPPY which should also generate a little
bit better code because SLOPPY is 0.
Maybe also STATIC_ASSERT(LANGUAGE_END == 2).

[Jakob Kummerow, 2017/04/20 09:52:34]

Done.

+      Return(FalseConstant());
+    }
+  }
+
+  BIND(&if_notunique);
+  {
+    // If the string was not found in the string table, then no object can
+    // have a property with that name.
+    TryInternalizeString(key, &if_index, &var_index, &if_unique_name,
+                         &var_unique, &if_notfound, &slow);
+  }
+
+  BIND(&if_notfound);
+  { Return(TrueConstant()); }

[Igor Sheludko, 2017/04/20 09:18:42]

I think this line will look nicer without {}.

[Jakob Kummerow, 2017/04/20 09:52:34]

Done.

+
+  BIND(&slow);
+  {
+    TailCallRuntime(Runtime::kDeleteProperty, context, receiver, key,
+                    language_mode);
+  }
+}
+
 }  // namespace internal
 }  // namespace v8