Store the stack of executioncontext's on the JS stack

This saves one pointer per allocated execution context.
Now every execution context that is pushed, allocates two
Values on the js stack. One contains the context itself, the
other one the offset to the parent context.

Things are a bit tricky for with and catch scopes, as those
are called from the generated code, and can't open a Scope
anymore. In addition, all methods iterating over the js
stack frames need to work with ExecutionContext pointers,
not ScopedContext's.

Change-Id: I6f3013749d4e73d2fac37973b976ba6029686b82
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

1 files changed, 16 insertions, 13 deletions

diff --git a/src/qml/jsruntime/qv4runtime.cpp b/src/qml/jsruntime/qv4runtime.cpp
index 5cc47aacd8..ca3195b405 100644
--- a/src/qml/jsruntime/qv4runtime.cpp
+++ b/src/qml/jsruntime/qv4runtime.cpp
@@ -1175,14 +1175,6 @@ QV4::ReturnedValue Runtime::typeofElement(ExecutionEngine *engine, const Value &
     return Runtime::typeofValue(engine, prop);
 }
 
-void Runtime::pushWithScope(const Value &o, ExecutionEngine *engine)
-{
-    Scope scope(engine);
-    ScopedObject obj(scope, o.toObject(engine));
-    ScopedContext ctx(scope, engine->currentContext());
-    engine->pushContext(ctx->newWithContext(obj));
-}
-
 ReturnedValue Runtime::unwindException(ExecutionEngine *engine)
 {
     if (!engine->hasException)
@@ -1190,18 +1182,29 @@ ReturnedValue Runtime::unwindException(ExecutionEngine *engine)
     return engine->catchException(0);
 }
 
+/* The next three methods are a bit tricky. They can't open up a Scope, as that
+ * would mess up the pushing of the context.
+ *
+ * Instead the push/pop pair acts as a non local scope.
+ */
+void Runtime::pushWithScope(const Value &o, ExecutionEngine *engine)
+{
+    engine->pushContext(engine->currentExecutionContext->newWithContext(o.toObject(engine)));
+    Q_ASSERT(engine->jsStackTop = engine->currentExecutionContext + 2);
+}
+
 void Runtime::pushCatchScope(NoThrowEngine *engine, int exceptionVarNameIndex)
 {
-    Scope scope(engine);
-    ScopedValue v(scope, engine->catchException(0));
-    ScopedString exceptionVarName(scope, engine->currentContext()->compilationUnit->runtimeStrings[exceptionVarNameIndex]);
-    ScopedContext ctx(scope, engine->currentContext());
-    engine->pushContext(ctx->newCatchContext(exceptionVarName, v));
+    ExecutionContext *c = engine->currentExecutionContext;
+    engine->pushContext(c->newCatchContext(c->d()->compilationUnit->runtimeStrings[exceptionVarNameIndex], engine->catchException(0)));
+    Q_ASSERT(engine->jsStackTop = engine->currentExecutionContext + 2);
 }
 
 void Runtime::popScope(ExecutionEngine *engine)
 {
+    Q_ASSERT(engine->jsStackTop = engine->currentExecutionContext + 2);
     engine->popContext();
+    engine->jsStackTop -= 2;
 }
 
 void Runtime::declareVar(ExecutionEngine *engine, bool deletable, int nameIndex)