Make so that array length property access uses a new IC that tracks the array map.

src/ia32/stub-cache-ia32.cc

Index: src/ia32/stub-cache-ia32.cc
diff --git a/src/ia32/stub-cache-ia32.cc b/src/ia32/stub-cache-ia32.cc
index f5e2d0589272047876166b353d1507dd26b554e0..cd471b1868db1e5fad6ddf0104b8eeab0ef0a7f3 100644
--- a/src/ia32/stub-cache-ia32.cc
+++ b/src/ia32/stub-cache-ia32.cc
@@ -3000,6 +3000,56 @@ Handle<Code> LoadStubCompiler::CompileLoadCallback(
 #define __ ACCESS_MASM(masm)
 
 
+void LoadStubCompiler::GenerateLoadArrayLength(
+    MacroAssembler* masm,
+    Register holder) {
+  // ----------- S t a t e -------------
+  //  -- ecx    : name
+  //  -- edx    : receiver
+  //  -- esp[0] : return address
+  // -----------------------------------
+
+  // Load length directly from the JS array.
+  __ mov(eax, FieldOperand(holder, JSArray::kLengthOffset));
+  __ ret(0);
+}
+
+
+#undef __
+#define __ ACCESS_MASM(masm())
+
+
+Handle<Code> LoadStubCompiler::CompileLoadArrayLength(
+    Handle<String> name,
+    Handle<JSObject> receiver,
+    Handle<JSObject> holder) {
+  // ----------- S t a t e -------------
+  //  -- ecx    : name
+  //  -- edx    : receiver
+  //  -- esp[0] : return address
+  // -----------------------------------
+  Label miss;
+
+  // Check that the maps haven't changed.
+  __ JumpIfSmi(edx, &miss);
+  Register holder_reg = CheckPrototypes(
+      receiver, edx, holder, ebx, eax, edi, name, &miss);
+
+  GenerateLoadArrayLength(masm(), holder_reg);
+
+  __ bind(&miss);
+  GenerateLoadMiss(masm(), Code::LOAD_IC);
+
+  // Return the generated code.
+  return GetCode(Code::CALLBACKS, name,
+                 Code::ExtraICStateForeignCallbackArrayLength);
+}
+
+
+#undef __
+#define __ ACCESS_MASM(masm)
+
+
 void LoadStubCompiler::GenerateLoadViaGetter(MacroAssembler* masm,
                                              Handle<JSFunction> getter) {
   // ----------- S t a t e -------------