Improve performance of addAll for internallt known lists.

runtime/lib/growable_array.dart

Index: runtime/lib/growable_array.dart
===================================================================
--- runtime/lib/growable_array.dart	(revision 43118)
+++ runtime/lib/growable_array.dart	(working copy)
@@ -152,7 +152,12 @@
 
   void addAll(Iterable<T> iterable) {
     var len = length;
-    if (iterable is EfficientLength) {
+    final cid = ClassID.getID(iterable);
+    final isList =

[Cutch, 2015/01/26 20:56:38]

maybe rename isBuiltinList, isVMList?

[srdjan, 2015/01/26 21:34:09]

isVMList.

+        (cid == ClassID.cidArray) ||
+        (cid == ClassID.cidGrowableObjectArray) ||
+        (cid == ClassID.cidImmutableArray);
+    if (isList || iterable is EfficientLength) {
       var cap = _capacity;
       // Pregrow if we know iterable.length.
       var iterLen = iterable.length;
@@ -163,6 +168,16 @@
         } while (newLen > cap);
         _grow(cap);
       }
+      if (isList) {

[Cutch, 2015/01/26 20:56:38]

Should this block (171-180) be moved down to 182?

[srdjan, 2015/01/26 21:34:09]

This code can be executed only if isVMList is true (if (isVMList || iterable is
EfficientLength). If I move it out I would need to recompute 'newLen' and
'iterLen',  and would not change the behavior. 

+        if (identical(iterable, this)) {
+          throw new ConcurrentModificationError(this);
+        }
+        this._setLength(newLen);
+        for (int i = 0; i < iterLen; i++) {
+          this[len++] = iterable[i];
+        }
+        return;
+      }
     }
     Iterator it = iterable.iterator;
     if (!it.moveNext()) return;