QML: Do not register static QML dependencies on every call.

QML objects can be re-parented on the fly, resulting in different
dependencies for expressions like 'parent.width'. So, because of this,
dependencies are cleared and re-calculated after every binding
evaluation.

However, dependencies on properties of the scope and context objects
cannot change, because these objects do not get changed for the
life-time of a binding. So we can permanently register them. This is
only done for bindings, not for functions, because those might be
conditionally executed.

According to valgrind, this is a reduction of ~186 instructions on x86
for every evaluation of:
Item {
    height: width
}

Change-Id: Ib095497323d4f08caf712d480007e2627a176369
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/qml/compiler/qqmlirbuilder.cpp b/src/qml/compiler/qqmlirbuilder.cpp
index 4fa63e3c84..c31a7bce4f 100644
--- a/src/qml/compiler/qqmlirbuilder.cpp
+++ b/src/qml/compiler/qqmlirbuilder.cpp
@@ -1890,7 +1890,9 @@ QV4::IR::Expr *JSCodeGen::fallbackNameLookup(const QString &name, int line, int
     // Look for IDs first.
     foreach (const IdMapping &mapping, _idObjects)
         if (name == mapping.name) {
-            _function->idObjectDependencies.insert(mapping.idIndex);
+            if (_function->isQmlBinding)
+                _function->idObjectDependencies.insert(mapping.idIndex);
+
             QV4::IR::Expr *s = _block->MEMBER(_block->TEMP(_qmlContextTemp), _function->newString(name), 0, QV4::IR::Member::MemberOfIdObjectsArray, mapping.idIndex);
             QV4::IR::Temp *result = _block->TEMP(_block->newTemp());
             _block->MOVE(result, s);