Revert of [intrinsic] Drop the %_ValueOf intrinsic.

src/full-codegen/x64/full-codegen-x64.cc

 // Copyright 2012 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 2715 matching lines @@
   // Objects with a non-function constructor have class 'Object'.
   __ bind(&non_function_constructor);
   __ LoadRoot(rax, Heap::kObject_stringRootIndex);
 
   // All done.
   __ bind(&done);
 
   context()->Plug(rax);
 }
 
+
+void FullCodeGenerator::EmitValueOf(CallRuntime* expr) {
+  ZoneList<Expression*>* args = expr->arguments();
+  DCHECK(args->length() == 1);
+
+  VisitForAccumulatorValue(args->at(0));  // Load the object.
+
+  Label done;
+  // If the object is a smi return the object.
+  __ JumpIfSmi(rax, &done);
+  // If the object is not a value type, return the object.
+  __ CmpObjectType(rax, JS_VALUE_TYPE, rbx);
+  __ j(not_equal, &done);
+  __ movp(rax, FieldOperand(rax, JSValue::kValueOffset));
+
+  __ bind(&done);
+  context()->Plug(rax);
+}
+
 
 void FullCodeGenerator::EmitStringCharFromCode(CallRuntime* expr) {
   ZoneList<Expression*>* args = expr->arguments();
   DCHECK(args->length() == 1);
 
   VisitForAccumulatorValue(args->at(0));
 
   Label done;
   StringCharFromCodeGenerator generator(rax, rbx);
   generator.GenerateFast(masm_);
@@ skipping 912 matching lines @@
   DCHECK_EQ(
       isolate->builtins()->OnStackReplacement()->entry(),
       Assembler::target_address_at(call_target_address, unoptimized_code));
   return ON_STACK_REPLACEMENT;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64