Revert of [intrinsic] Drop the %_ValueOf intrinsic.

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

Index: src/full-codegen/x64/full-codegen-x64.cc
diff --git a/src/full-codegen/x64/full-codegen-x64.cc b/src/full-codegen/x64/full-codegen-x64.cc
index cf59e66abdcb7aec5469fe61aff43f3c53ef31ff..0e5cf985b8d9286f4192c9d6c6db93fcbae0b2e7 100644
--- a/src/full-codegen/x64/full-codegen-x64.cc
+++ b/src/full-codegen/x64/full-codegen-x64.cc
@@ -2730,6 +2730,25 @@
   // 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);
 }