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>

4 files changed, 7 insertions, 2 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);
diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index 8711bc049a..7a444e8c57 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -1961,6 +1961,7 @@ int Codegen::defineFunction(const QString &name, AST::Node *ast,
     function->maxNumberOfArguments = qMax(_env->maxNumberOfArguments, (int)QV4::Global::ReservedArgumentCount);
     function->isStrict = _env->isStrict;
     function->isNamedExpression = _env->isNamedFunctionExpression;
+    function->isQmlBinding = _env->compilationMode == QmlBinding;
 
     AST::SourceLocation loc = ast->firstSourceLocation();
     function->line = loc.startLine;
diff --git a/src/qml/compiler/qv4jsir.cpp b/src/qml/compiler/qv4jsir.cpp
index b994d2f707..74c4f91f2b 100644
--- a/src/qml/compiler/qv4jsir.cpp
+++ b/src/qml/compiler/qv4jsir.cpp
@@ -368,6 +368,7 @@ Function::Function(Module *module, Function *outer, const QString &name)
     , isNamedExpression(false)
     , hasTry(false)
     , hasWith(false)
+    , isQmlBinding(false)
     , unused(0)
     , line(-1)
     , column(-1)
diff --git a/src/qml/compiler/qv4jsir_p.h b/src/qml/compiler/qv4jsir_p.h
index 0254ae224d..c196e8127b 100644
--- a/src/qml/compiler/qv4jsir_p.h
+++ b/src/qml/compiler/qv4jsir_p.h
@@ -1258,7 +1258,8 @@ struct Function {
     uint isNamedExpression : 1;
     uint hasTry: 1;
     uint hasWith: 1;
-    uint unused : 25;
+    uint isQmlBinding: 1;
+    uint unused : 24;
 
     // Location of declaration in source code (-1 if not specified)
     int line;