Allow inline caching for getting the length of string wrapper objects.

src/stub-cache-ia32.cc

 // Copyright 2006-2008 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 141 matching lines @@
   __ movzx_b(scratch, FieldOperand(scratch, Map::kInstanceTypeOffset));
   __ cmp(scratch, JS_ARRAY_TYPE);
   __ j(not_equal, miss_label, not_taken);
 
   // Load length directly from the JS array.
   __ mov(eax, FieldOperand(receiver, JSArray::kLengthOffset));
   __ ret(0);
 }
 
 
+// Generate code to check is an object is a string.  If the object is
+// a string, the map's instance type is left in the scratch register.
+static void GenerateStringCheck(MacroAssembler* masm,
+                                Register receiver,
+                                Register scratch,
+                                Label* smi,
+                                Label* non_string_object) {
+  // Check that the object isn't a smi.
+  __ test(receiver, Immediate(kSmiTagMask));
+  __ j(zero, smi, not_taken);
+
+  // Check that the object is a string.
+  __ mov(scratch, FieldOperand(receiver, HeapObject::kMapOffset));
+  __ movzx_b(scratch, FieldOperand(scratch, Map::kInstanceTypeOffset));
+  ASSERT(kNotStringTag != 0);
+  __ test(scratch, Immediate(kNotStringTag));
+  __ j(not_zero, non_string_object, not_taken);
+}
+
+
 void StubCompiler::GenerateLoadStringLength(MacroAssembler* masm,
                                             Register receiver,
                                             Register scratch,
-                                            Label* miss_label) {
-  // Check that the receiver isn't a smi.
-  __ test(receiver, Immediate(kSmiTagMask));
-  __ j(zero, miss_label, not_taken);
+                                            Label* miss) {
+  Label load_length, check_wrapper;
 
-  // Check that the object is a string.
-  __ mov(scratch, FieldOperand(receiver, HeapObject::kMapOffset));
-  __ movzx_b(scratch, FieldOperand(scratch, Map::kInstanceTypeOffset));
-  ASSERT(kNotStringTag != 0);
-  __ test(scratch, Immediate(kNotStringTag));
-  __ j(not_zero, miss_label, not_taken);
-
-  __ and_(scratch, kStringSizeMask);
+  // Check if the object is a string.
+  GenerateStringCheck(masm, receiver, scratch, miss, &check_wrapper);
 
   // Load length directly from the string.
+  __ bind(&load_length);
+  __ and_(scratch, kStringSizeMask);
   __ mov(eax, FieldOperand(receiver, String::kLengthOffset));
-
   // ecx is also the receiver.
   __ lea(ecx, Operand(scratch, String::kLongLengthShift));
   __ shr(eax);  // ecx is implicit shift register.
   __ shl(eax, kSmiTagSize);
   __ ret(0);
+
+  // Check if the object is a JSValue wrapper.
+  __ bind(&check_wrapper);
+  __ cmp(receiver, JS_VALUE_TYPE);
+  __ j(not_equal, miss, not_taken);
+
+  // Check if the wrapped value is a string and load the length
+  // directly if it is.
+  __ mov(receiver, FieldOperand(receiver, JSValue::kValueOffset));
+  GenerateStringCheck(masm, receiver, scratch, miss, miss);
+  __ jmp(&load_length);
 }
 
 
 void StubCompiler::GenerateLoadFunctionPrototype(MacroAssembler* masm,
                                                  Register receiver,
                                                  Register scratch1,
                                                  Register scratch2,
                                                  Label* miss_label) {
   __ TryGetFunctionPrototype(receiver, scratch1, scratch2, miss_label);
   __ mov(eax, Operand(scratch1));
@@ skipping 966 matching lines @@
   GenerateLoadMiss(masm(), Code::KEYED_LOAD_IC);
 
   // Return the generated code.
   return GetCode(CALLBACKS);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal