[vm] Better List.of
List.from now calls List.of instead of the other way around.
Separate loops for system Lists, EfficientLengthIterables
and other Iterables should keep the performance of these
cases independent.
Change-Id: I26a23b10d2fb8fd2683a4f9c26257860cfdfa758
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/173860
Commit-Queue: Stephen Adams <sra@google.com>
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
diff --git a/sdk/lib/_internal/vm/lib/array_patch.dart b/sdk/lib/_internal/vm/lib/array_patch.dart
index 51fe288..df03cf6 100644
--- a/sdk/lib/_internal/vm/lib/array_patch.dart
+++ b/sdk/lib/_internal/vm/lib/array_patch.dart
@@ -30,43 +30,60 @@
@patch
factory List.from(Iterable elements, {bool growable: true}) {
- if (elements is EfficientLengthIterable<E>) {
- int length = elements.length;
- var list = growable ? new _GrowableList<E>(length) : new _List<E>(length);
- if (length > 0) {
- // Avoid creating iterator unless necessary.
- int i = 0;
- for (var element in elements) {
- list[i++] = element;
- }
- }
- return list;
- }
// If elements is an Iterable<E>, we won't need a type-test for each
- // element. In the "common case" that elements is an Iterable<E>, this
- // replaces a type-test on every element with a single type-test before
- // starting the loop.
+ // element.
if (elements is Iterable<E>) {
- List<E> list = new _GrowableList<E>(0);
- for (E e in elements) {
- list.add(e);
- }
- if (growable) return list;
- return makeListFixedLength(list);
- } else {
- List<E> list = new _GrowableList<E>(0);
- for (E e in elements) {
- list.add(e);
- }
- if (growable) return list;
- return makeListFixedLength(list);
+ return List.of(elements, growable: growable);
}
+
+ List<E> list = new _GrowableList<E>(0);
+ for (E e in elements) {
+ list.add(e);
+ }
+ if (growable) return list;
+ return makeListFixedLength(list);
}
@patch
factory List.of(Iterable<E> elements, {bool growable: true}) {
- // TODO(32937): Specialize to benefit from known element type.
- return List.from(elements, growable: growable);
+ final cid = ClassID.getID(elements);
+ final isVMList = (cid == ClassID.cidArray) ||
+ (cid == ClassID.cidGrowableObjectArray) ||
+ (cid == ClassID.cidImmutableArray);
+
+ if (isVMList) {
+ final ListBase<E> elementsAsList = elements as ListBase<E>;
+ final int length = elementsAsList.length;
+ final list =
+ growable ? new _GrowableList<E>(length) : new _List<E>(length);
+ if (length > 0) {
+ for (int i = 0; i < length; i++) {
+ list[i] = elementsAsList[i];
+ }
+ }
+ return list;
+ }
+
+ if (elements is EfficientLengthIterable) {
+ final int length = elements.length;
+ final list =
+ growable ? new _GrowableList<E>(length) : new _List<E>(length);
+ if (length > 0) {
+ int i = 0;
+ for (var element in elements) {
+ list[i++] = element;
+ }
+ if (i != length) throw ConcurrentModificationError(elements);
+ }
+ return list;
+ }
+
+ final list = <E>[];
+ for (var elements in elements) {
+ list.add(elements);
+ }
+ if (growable) return list;
+ return makeListFixedLength(list);
}
@patch
