feat: lots of optimization

* allocate vm stack on the stack
* use Rc instead of Arc
* optimize recursive attribute set

src/compile.rs

@@ -95,11 +95,7 @@ impl Compile for ir::Thunk {
 
 impl Compile for ir::Attrs {
     fn compile(self, comp: &mut Compiler) {
-        comp.push(if self.rec {
-            OpCode::RecAttrSet
-        } else {
-            OpCode::AttrSet
-        });
+        comp.push(OpCode::AttrSet);
         for stc in self.stcs {
             stc.1.compile(comp);
             comp.push(OpCode::PushStaticAttr { name: stc.0 });
@@ -110,7 +106,7 @@ impl Compile for ir::Attrs {
             comp.push(OpCode::PushDynamicAttr)
         }
         if self.rec {
-            comp.push(OpCode::LeaveEnv);
+            comp.push(OpCode::FinalizeRec);
         }
     }
 }