fix: copy whole register on assignment

src/main/wacc/backend/asmGenerator.scala

@@ -161,15 +161,15 @@ object asmGenerator {
       labelGenerator: LabelGenerator
   ): Chain[AsmLine] = {
     var asm = Chain.empty[AsmLine]
+    asm += Comment(stmt.toString)
     stmt match {
       case Assign(lhs, rhs) =>
         lhs match {
           case ident: Ident =>
             if (!stack.contains(ident)) asm += stack.reserve(ident)
-            val dest = Register(ident.ty.size, AX)
             asm ++= evalExprOntoStack(rhs)
             asm += stack.pop(RAX)
-            asm += Move(stack.accessVar(ident), dest)
+            asm += Move(stack.accessVar(ident).copy(opSize = Some(Size.Q64)), RAX)
           case ArrayElem(x, i) =>
             asm ++= evalExprOntoStack(rhs)
             asm ++= evalExprOntoStack(i)