Improve load IC so it can call a native accessor even if the holder is

src/arm/stub-cache-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1212 matching lines @@
   // Check that the maps haven't changed.
   CheckPrototypes(
       object, receiver, holder, scratch1, scratch2, scratch3, name, miss);
 
   // Return the constant value.
   __ LoadHeapObject(r0, value);
   __ Ret();
 }
 
 
+void StubCompiler::GenerateDictionaryLoadCallback(Register receiver,
+                                                  Register name_reg,
+                                                  Register scratch1,
+                                                  Register scratch2,
+                                                  Register scratch3,
+                                                  Handle<AccessorInfo> callback,
+                                                  Handle<String> name,
+                                                  Label* miss) {
+  Register dictionary = scratch1;
+  __ ldr(dictionary, FieldMemOperand(receiver, JSObject::kPropertiesOffset));
+
+  // Probe the dictionary.
+  Label probe_done;
+  StringDictionaryLookupStub::GeneratePositiveLookup(masm(),
+                                                     miss,
+                                                     &probe_done,
+                                                     dictionary,
+                                                     name_reg,
+                                                     scratch2,
+                                                     scratch3);
+  __ bind(&probe_done);
+
+  // If probing finds an entry in the dictionary, scratch2 contains the
+  // index into the dictionary. Check that the value is the callback.
+  Register index = scratch2;

[Toon Verwaest, 2012/08/06 13:49:24]

If you do this assignment before passing scratch2 (index) into
GeneratePositiveLookup, half of the comment becomes unnecessary.

[Erik Corry, 2012/08/06 14:26:46]

Done.

+  const int kElementsStartOffset =
+      StringDictionary::kHeaderSize +
+      StringDictionary::kElementsStartIndex * kPointerSize;
+  const int kValueOffset = kElementsStartOffset + kPointerSize;
+  __ add(scratch1, dictionary, Operand(kValueOffset - kHeapObjectTag));
+  __ ldr(scratch3, MemOperand(scratch1, index, LSL, kPointerSizeLog2));
+  __ cmp(scratch3, Operand(callback));
+  __ b(ne, miss);
+}
+
+
 void StubCompiler::GenerateLoadCallback(Handle<JSObject> object,
                                         Handle<JSObject> holder,
                                         Register receiver,
                                         Register name_reg,
                                         Register scratch1,
                                         Register scratch2,
                                         Register scratch3,
                                         Handle<AccessorInfo> callback,
                                         Handle<String> name,
                                         Label* miss) {
   // Check that the receiver isn't a smi.
   __ JumpIfSmi(receiver, miss);
 
   // Check that the maps haven't changed.
   Register reg = CheckPrototypes(object, receiver, holder, scratch1,
                                  scratch2, scratch3, name, miss);
 
+  if (!holder->HasFastProperties() && !holder->IsJSGlobalObject()) {
+    GenerateDictionaryLoadCallback(
+        receiver, name_reg, scratch1, scratch2, scratch3, callback, name, miss);
+  }
+
   // Build AccessorInfo::args_ list on the stack and push property name below
   // the exit frame to make GC aware of them and store pointers to them.
   __ push(receiver);
   __ mov(scratch2, sp);  // scratch2 = AccessorInfo::args_
   if (heap()->InNewSpace(callback->data())) {
     __ Move(scratch3, callback);
     __ ldr(scratch3, FieldMemOperand(scratch3, AccessorInfo::kDataOffset));
   } else {
     __ Move(scratch3, Handle<Object>(callback->data()));
   }
@@ skipping 3420 matching lines @@
     __ Jump(ic_slow, RelocInfo::CODE_TARGET);
   }
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM