QML: Remove internal field padding from QQuickAnchorPrivate.

Don't store QQuickAnchorLine, but store both fields separately in
QQuickAnchorPrivate. This prevents padding of QQuickAnchorLine, saving
48 bytes on x86_64 (or any platform where structs are 8-byte aligned).

On x86_64, this also removes ~180 instructions for each QQuickAnchor
creation/removal, and speeds up the constructor by 25%.

While in the neighborhood, do a drive-by change and merge
QQuickAnchorLine::AnchorLine and QQuickAnchors::Anchor by removing the
former.

Change-Id: I50ab6252b1903f5f1a075174e6185c3048a8f8ec
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/tests/benchmarks/qml/creation/tst_creation.cpp b/tests/benchmarks/qml/creation/tst_creation.cpp
index e126cdae7e..7b00eabc28 100644
--- a/tests/benchmarks/qml/creation/tst_creation.cpp
+++ b/tests/benchmarks/qml/creation/tst_creation.cpp
@@ -68,6 +68,7 @@ private slots:
     void itemtests_qml_data();
     void itemtests_qml();
 
+    void anchors_creation();
     void anchors_heightChange();
 
 private:
@@ -375,6 +376,20 @@ void tst_creation::itemtests_qml()
     QBENCHMARK { delete component.create(); }
 }
 
+void tst_creation::anchors_creation()
+{
+    QQmlComponent component(&engine);
+    component.setData("import QtQuick 2.0\nItem { Item { anchors.bottom: parent.bottom } }", QUrl());
+
+    QObject *obj = component.create();
+    delete obj;
+
+    QBENCHMARK {
+        QObject *obj = component.create();
+        delete obj;
+    }
+}
+
 void tst_creation::anchors_heightChange()
 {
     QQmlComponent component(&engine);