[DI] Improve performance of processDefinition

Author: Stefan Kruppa

Compiler/ResolveInstanceofConditionalsPass.php

@@ -64,9 +64,10 @@ private function processDefinition(ContainerBuilder $container, $id, Definition
         $definition->setInstanceofConditionals([]);
         $parent = $shared = null;
         $instanceofTags = [];
+        $reflectionClass = null;
 
         foreach ($conditionals as $interface => $instanceofDefs) {
-            if ($interface !== $class && (!$container->getReflectionClass($class, false))) {
+            if ($interface !== $class && !(null === $reflectionClass ? $reflectionClass = ($container->getReflectionClass($class, false) ?: false) : $reflectionClass)) {
                 continue;
             }