Disable memelim

It's causing issues with the vector translator.

hphp/runtime/vm/translator/hopt/memelim.cpp

@@ -818,7 +818,10 @@ void MemMap::sinkStores(StoreList& stores) {
 }
 
 void optimizeMemoryAccesses(Trace* trace, IRFactory* factory) {
-  MemMap(factory).optimizeMemoryAccesses(trace);
+  if (false) { // TODO(#2302684): memelim can break vector
+               // translations right now
+    MemMap(factory).optimizeMemoryAccesses(trace);
+  }
 }
 
 } } }

hphp/test/quick/hopt_cgetelemc_test.php

@@ -0,0 +1,15 @@
+<?php
+
+function val() { return 0; }
+function foo($k) {
+  $array = array(0, 1);
+  $idx =& val();
+  for ($ik = 0; $ik < 10; ++$ik) {
+  }
+
+  $idx++;
+  echo $array[$idx];
+  echo "\n";
+}
+
+foo(12);

hphp/test/quick/hopt_cgetelemc_test.php.expect

@@ -0,0 +1 @@
+1