Add reference counting to the VM functions

This reduces memory pressure, keep engine->functions small and thus makes back
trace lookup faster. It became visible for example in the QtQuickControls
auto-tests that use plenty of loaders and we ended up with 30k+ functions.

Change-Id: Iaa5981f44e1e49ad9417a50c1e6a74946090dd28
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 16 insertions, 2 deletions

diff --git a/src/qml/jsruntime/qv4function_p.h b/src/qml/jsruntime/qv4function_p.h
index 3ff31ed2e3..612bbb122e 100644
--- a/src/qml/jsruntime/qv4function_p.h
+++ b/src/qml/jsruntime/qv4function_p.h
@@ -87,6 +87,7 @@ struct LineNumberMapping
 };
 
 struct Function {
+    int refCount;
     String *name;
 
     Value (*code)(ExecutionContext *, const uchar *);
@@ -111,8 +112,11 @@ struct Function {
     QString sourceFile;
     QVector<LineNumberMapping> lineNumberMappings;
 
-    Function(String *name)
-        : name(name)
+    ExecutionEngine *engine;
+
+    Function(ExecutionEngine *engine, String *name)
+        : refCount(0)
+        , name(name)
         , code(0)
         , codeData(0)
         , codeSize(0)
@@ -122,9 +126,19 @@ struct Function {
         , usesArgumentsObject(false)
         , isStrict(false)
         , isNamedExpression(false)
+        , engine(engine)
     {}
     ~Function();
 
+    void ref() { ++refCount; }
+    void deref() { if (!--refCount) delete this; }
+
+    void addNestedFunction(Function *f)
+    {
+        f->ref();
+        nestedFunctions.append(f);
+    }
+
     inline bool needsActivation() const { return hasNestedFunctions || hasDirectEval || usesArgumentsObject; }
 
     void mark();