From d9dcb4461ed90b2e006e2120f3dad180f8045814 Mon Sep 17 00:00:00 2001
From: Leonardo de Moura <leonardo@microsoft.com>
Date: Tue, 21 Feb 2017 15:29:55 -0800
Subject: [PATCH] perf(library/vm/vm_array): minor optimization

---
 src/library/vm/vm_array.cpp | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/src/library/vm/vm_array.cpp b/src/library/vm/vm_array.cpp
index b0341d2d30..d5377c0eaf 100644
--- a/src/library/vm/vm_array.cpp
+++ b/src/library/vm/vm_array.cpp
@@ -74,37 +74,37 @@ vm_obj array_read(vm_obj const &, vm_obj const &, vm_obj const & a, vm_obj const
 vm_obj array_write(vm_obj const &, vm_obj const &, vm_obj const & a, vm_obj const & i, vm_obj const & v) {
     /* TODO(Leo): handle case where n is too big */
     unsigned idx = force_to_unsigned(i);
-    lean_vm_check(idx < to_array(a).size());
+    parray<vm_obj> const & p = to_array(a);
+    lean_vm_check(idx < p.size());
     if (a.raw()->get_rc() == 1) {
-        parray<vm_obj> & new_a = const_cast<parray<vm_obj> &>(to_array(a));
-        new_a.set(idx, v);
-        return to_obj(new_a);
+        const_cast<parray<vm_obj> &>(p).set(idx, v);
+        return a;
     } else {
-        parray<vm_obj> new_a = to_array(a);
+        parray<vm_obj> new_a = p;
         new_a.set(idx, v);
         return to_obj(new_a);
     }
 }
 
 vm_obj array_push_back(vm_obj const &, vm_obj const &, vm_obj const & a, vm_obj const & v) {
+    parray<vm_obj> const & p = to_array(a);
     if (a.raw()->get_rc() == 1) {
-        parray<vm_obj> & new_a = const_cast<parray<vm_obj> &>(to_array(a));
-        new_a.push_back(v);
-        return to_obj(new_a);
+        const_cast<parray<vm_obj> &>(p).push_back(v);
+        return a;
     } else {
-        parray<vm_obj> new_a = to_array(a);
+        parray<vm_obj> new_a = p;
         new_a.push_back(v);
         return to_obj(new_a);
     }
 }
 
 vm_obj array_pop_back(vm_obj const &, vm_obj const &, vm_obj const & a) {
+    parray<vm_obj> const & p = to_array(a);
     if (a.raw()->get_rc() == 1) {
-        parray<vm_obj> & new_a = const_cast<parray<vm_obj> &>(to_array(a));
-        new_a.pop_back();
-        return to_obj(new_a);
+        const_cast<parray<vm_obj> &>(p).pop_back();
+        return a;
     } else {
-        parray<vm_obj> new_a = to_array(a);
+        parray<vm_obj> new_a = p;
         new_a.pop_back();
         return to_obj(new_a);
     }