avm2: Optimize ConstructProp to ConstructSlot when possible

Author: Lord-McSweeney

core/src/avm2/activation.rs

@@ -883,6 +883,7 @@ impl<'a, 'gc> Activation<'a, 'gc> {
                     multiname,
                     num_args,
                 } => self.op_construct_prop(*multiname, *num_args),
+                Op::ConstructSlot { index, num_args } => self.op_construct_slot(*index, *num_args),
                 Op::ConstructSuper { num_args } => self.op_construct_super(*num_args),
                 Op::NewActivation => self.op_new_activation(),
                 Op::NewObject { num_args } => self.op_new_object(*num_args),
@@ -1729,6 +1730,26 @@ impl<'a, 'gc> Activation<'a, 'gc> {
         Ok(FrameControl::Continue)
     }
 
+    fn op_construct_slot(
+        &mut self,
+        index: u32,
+        arg_count: u32,
+    ) -> Result<FrameControl<'gc>, Error<'gc>> {
+        let args = self.pop_stack_args(arg_count);
+        let source = self
+            .pop_stack()
+            .null_check(self, None)?
+            .as_object()
+            .expect("Cannot get_slot on primitive");
+
+        let ctor = source.get_slot(index);
+        let constructed_object = ctor.construct(self, &args)?;
+
+        self.push_stack(constructed_object);
+
+        Ok(FrameControl::Continue)
+    }
+
     fn op_construct_super(&mut self, arg_count: u32) -> Result<FrameControl<'gc>, Error<'gc>> {
         let args = self.pop_stack_args(arg_count);
         let receiver = self.pop_stack().null_check(self, None)?;

core/src/avm2/op.rs

@@ -84,6 +84,10 @@ pub enum Op<'gc> {
         multiname: Gc<'gc, Multiname<'gc>>,
         num_args: u32,
     },
+    ConstructSlot {
+        index: u32,
+        num_args: u32,
+    },
     ConstructSuper {
         num_args: u32,
     },

core/src/avm2/optimizer/optimize.rs

@@ -1532,6 +1532,11 @@ fn abstract_interpret_ops<'gc>(
                         match vtable.get_trait(&multiname) {
                             Some(Property::Slot { slot_id })
                             | Some(Property::ConstSlot { slot_id }) => {
+                                optimize_op_to!(Op::ConstructSlot {
+                                    index: slot_id,
+                                    num_args
+                                });
+
                                 let mut value_class = vtable.slot_classes()[slot_id as usize];
                                 let resolved_value_class = value_class.get_class(activation)?;
 
@@ -1798,6 +1803,7 @@ fn abstract_interpret_ops<'gc>(
             | Op::CoerceDSwapPop
             | Op::CoerceISwapPop
             | Op::CoerceUSwapPop
+            | Op::ConstructSlot { .. }
             | Op::GetScriptGlobals { .. }
             | Op::SetSlotNoCoerce { .. } => unreachable!("Custom ops should not be encountered"),
         }