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 43149)
+++ 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 isVMList =
+        (cid == ClassID.cidArray) ||
+        (cid == ClassID.cidGrowableObjectArray) ||
+        (cid == ClassID.cidImmutableArray);

[Lasse Reichstein Nielsen, 2015/01/27 15:13:57]

Would it be worth it to recognize growable list as well in setRange?

[srdjan, 2015/01/29 17:42:19]

I think so, but we would need to move it here since cid-s are VM specific stuff.
Comparing cids is faster than instanceof test.

+    if (isVMList || (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 (isVMList) {
+        if (identical(iterable, this)) {
+          throw new ConcurrentModificationError(this);

[Lasse Reichstein Nielsen, 2015/01/27 15:13:57]

This does change behavior (it now throws before adding the first element), but
nobody should be depending on that, so that's fine with me.

Of the internal lists, only GrowableObjectArray will reach here, the other ones
throw immediately when calling addAll, but the boolean is already computed, so
it's probably just as good as comparing cid to ClassID.cidGrowable....
Might be worth a comment though, so the _setLength below isn't confusing anyone
into thinking you change the length of an Array.

[srdjan, 2015/01/29 17:42:19]

I do not understand. 'this' is always GrowableObjectArray.

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