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Capture closures around megamorphic dispatches

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The performLayout and build callsite are highly megamorphic because they
dispatch into a large number of clients. However, for a given caller, the
callee is always of the same type, which means the megamorphic lookup exactly
factors by the caller. We can speed up the dispatch by capturing a closure at
initialization and then monomorphically dispatching through the closure.
This commit is contained in:
Adam Barth 2016-03-31 12:26:50 -07:00
parent 0be7a33b14
commit 622bec43be
2 changed files with 19 additions and 4 deletions
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13
packages/flutter/lib/src/rendering/object.dart
View File

@ -777,6 +777,9 @@ class PipelineOwner {
}
// See _performLayout.
void _doNothing() { }
/// An object in the render tree.
///
/// The [RenderObject] class hierarchy is the core of the rendering
@ -804,6 +807,7 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
RenderObject() {
_needsCompositing = isRepaintBoundary || alwaysNeedsCompositing;
_performLayout = performLayout;
}
// LAYOUT
@ -1073,7 +1077,7 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
return true;
});
try {
performLayout();
_performLayout();
markNeedsSemanticsUpdate();
} catch (e, stack) {
_debugReportException('performLayout', e, stack);
@ -1168,7 +1172,7 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
return true;
});
try {
performLayout();
_performLayout();
markNeedsSemanticsUpdate();
assert(() { debugAssertDoesMeetConstraints(); return true; });
} catch (e, stack) {
@ -1235,6 +1239,11 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
/// information without informing this render object.
void performLayout();
// We cache a closure to performLayout so that the callsite is monomorphic.
// Initializing this field with _buildNothing helps the compiler prove that
// this field always holds a closure.
VoidCallback _performLayout = _doNothing;
/// Allows this render object to mutate its child list during layout and
/// invokes callback.
void invokeLayoutCallback(LayoutCallback callback) {

10
packages/flutter/lib/src/widgets/framework.dart
View File

@ -1351,12 +1351,18 @@ abstract class BuildableElement extends Element {
typedef Widget WidgetBuilder(BuildContext context);
// See _builder.
Widget _buildNothing(BuildContext context) => null;
/// Base class for the instantiation of [StatelessWidget], [StatefulWidget],
/// and [_ProxyWidget] widgets.
abstract class ComponentElement extends BuildableElement {
ComponentElement(Widget widget) : super(widget);
WidgetBuilder _builder;
// Initializing this field with _buildNothing helps the compiler prove that
// this field always holds a closure.
WidgetBuilder _builder = _buildNothing;
Element _child;
@override
@ -1456,7 +1462,7 @@ class StatefulElement extends ComponentElement {
assert(_state._debugTypesAreRight(widget));
assert(_state._element == null);
_state._element = this;
assert(_builder == null);
assert(_builder == _buildNothing);
_builder = _state.build;
assert(_state._config == null);
_state._config = widget;