Add faster, but unsafe version of LoadInternalField.

src/fast-accessor-assembler.h

 // Copyright 2015 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.
 
 #ifndef V8_FAST_ACCESSOR_ASSEMBLER_H_
 #define V8_FAST_ACCESSOR_ASSEMBLER_H_
 
 #include <stdint.h>
 #include <memory>
 #include <vector>
@@ skipping 36 matching lines @@
   typedef v8::experimental::FastAccessorBuilder::LabelId LabelId;
   typedef v8::FunctionCallback FunctionCallback;
 
   explicit FastAccessorAssembler(Isolate* isolate);
   ~FastAccessorAssembler();
 
   // Builder / assembler functions:
   ValueId IntegerConstant(int int_constant);
   ValueId GetReceiver();
   ValueId LoadInternalField(ValueId value_id, int field_no);
+
+  // Loads internal field and assumes the object is indeed a valid API object
+  // with the proper internal fields present.
+  // The intended use is to call this on an object whose structure has already
+  // been checked previously, e.g. the accessor's receiver, which is map-checked
+  // before the fast accessor is called on it. Using this on an arbitrary object
+  // will result in unsafe memory accesses.
+  ValueId LoadInternalFieldUnchecked(ValueId value_id, int field_no);
+
   ValueId LoadValue(ValueId value_id, int offset);
   ValueId LoadObject(ValueId value_id, int offset);
 
   // Builder / assembler functions for control flow.
   void ReturnValue(ValueId value_id);
   void CheckFlagSetOrReturnNull(ValueId value_id, int mask);
   void CheckNotZeroOrReturnNull(ValueId value_id);
   LabelId MakeLabel();
   void SetLabel(LabelId label_id);
   void CheckNotZeroOrJump(ValueId value_id, LabelId label_id);
 
   // C++ callback.
   ValueId Call(FunctionCallback callback, ValueId arg);
 
   // Assemble the code.
   MaybeHandle<Code> Build();
 
  private:
   ValueId FromRaw(compiler::Node* node);
   LabelId FromRaw(CodeStubAssembler::Label* label);
   compiler::Node* FromId(ValueId value) const;
   CodeStubAssembler::Label* FromId(LabelId value) const;
+  void CheckIsJSObjectOrJump(ValueId value, LabelId label_id);

[vogelheim, 2016/08/08 11:47:22]

nitpick: Maybe add empty line. The previous 4 methods are a group of closely
related functions (translating API-IDs to Node*), while this one is quite
different.

[Alfonso, 2016/08/08 13:03:28]

Acknowledged.

 
   void Clear();
   Zone* zone() { return &zone_; }
   Isolate* isolate() const { return isolate_; }
 
   Zone zone_;
   Isolate* isolate_;
   std::unique_ptr<CodeStubAssembler> assembler_;
 
   // To prevent exposing the RMA internals to the outside world, we'll map
   // Node + Label pointers integers wrapped in ValueId and LabelId instances.
   // These vectors maintain this mapping.
   std::vector<compiler::Node*> nodes_;
   std::vector<CodeStubAssembler::Label*> labels_;
 
   // Remember the current state for easy error checking. (We prefer to be
   // strict as this class will be exposed at the API.)
   enum { kBuilding, kBuilt, kError } state_;
 
   DISALLOW_COPY_AND_ASSIGN(FastAccessorAssembler);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_FAST_ACCESSOR_ASSEMBLER_H_