Remove (H|L)JSArrayLength instructions

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index c2305d7bbfeb0bfcd4374651856da0109ce28bd4..79ffd5254cb02614e0514b9fd567e47c176dac48 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -1165,8 +1165,8 @@ HInstruction* HGraphBuilder::BuildUncheckedMonomorphicElementAccess(
   }
   HInstruction* length = NULL;
   if (is_js_array) {
-    length = AddInstruction(new(zone) HJSArrayLength(object, mapcheck,
-                                                     HType::Smi()));
+    length = AddInstruction(
+        HLoadNamedField::NewArrayLength(zone, object, mapcheck));

[danno, 2013/04/02 11:10:43]

I think you are losing the fact that the type of this instruction is a Smi. It
is used for optimization purposes later in the compilation pipeline. Some array
lengths are known to be Smis (if their map is guaranteed to fast elements), but
otherwise, they may be a tagged heap number, which will require more heavy
checks in the generated code. You will need to preserve the ability to specify
the return type of the load.

   } else {
     length = AddInstruction(new(zone) HFixedArrayBaseLength(elements));
   }
@@ -1237,8 +1237,7 @@ HInstruction* HGraphBuilder::BuildUncheckedMonomorphicElementAccess(
 
 HInstruction* HGraphBuilder::BuildFastArrayLengthLoad(HValue* object,
                                                       HValue* typecheck) {
-  Zone* zone = this->zone();
-  return new (zone) HJSArrayLength(object, typecheck, HType::Smi());
+  return HLoadNamedField::NewArrayLength(zone(), object, typecheck);
 }
 
 
@@ -7377,8 +7376,8 @@ HValue* HOptimizedGraphBuilder::HandlePolymorphicElementAccess(
 
         set_current_block(if_jsarray);
         HInstruction* length;
-        length = AddInstruction(new(zone()) HJSArrayLength(object, typecheck,
-                                                           HType::Smi()));
+        length = AddInstruction(
+            HLoadNamedField::NewArrayLength(zone(), object, typecheck));
         checked_key = AddBoundsCheck(key, length, ALLOW_SMI_KEY);
         access = AddInstruction(BuildFastElementAccess(
             elements, checked_key, val, elements_kind_branch,