feat(opt): Don't clone on array_len (#9440)

Author: jfecher

compiler/noirc_frontend/src/ownership/mod.rs

@@ -324,6 +324,20 @@ impl Context {
         for arg in &mut call.arguments {
             self.handle_expression(arg);
         }
+
+        // Hack to avoid clones when calling `array.len()`.
+        // That function takes arrays by value but we know it never mutates them.
+        if let Expression::Ident(ident) = call.func.as_ref() {
+            if let Definition::Builtin(name) = &ident.definition {
+                if name == "array_len" {
+                    if let Some(Expression::Clone(array)) = call.arguments.get_mut(0) {
+                        let array =
+                            std::mem::replace(array.as_mut(), Expression::Literal(Literal::Unit));
+                        call.arguments[0] = array;
+                    }
+                }
+            }
+        }
     }
 
     fn handle_let(&mut self, let_expr: &mut crate::monomorphization::ast::Let) {