diff --git a/core/lib/Drupal/Core/Entity/EntityViewBuilder.php b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
index 7c9c5c3..086a826 100644
--- a/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
+++ b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
@@ -368,10 +368,9 @@ public function resetCache(array $entities = NULL) {
     if (isset($entities)) {
       $tags = [];
       foreach ($entities as $entity) {
-        $tags = array_merge($tags, $entity->getCacheTags());
-        $tags = array_merge($tags, $entity->getEntityType()->getListCacheTags());
+        $tags = Cache::mergeTags($tags, $entity->getCacheTags());
+        $tags = Cache::mergeTags($tags, $entity->getEntityType()->getListCacheTags());
       }
-      $tags = Cache::mergeTags($tags)
       Cache::invalidateTags($tags);
     }
     else {
diff --git a/core/modules/block/src/BlockViewBuilder.php b/core/modules/block/src/BlockViewBuilder.php
index 0990f17..6d5c7bd 100644
--- a/core/modules/block/src/BlockViewBuilder.php
+++ b/core/modules/block/src/BlockViewBuilder.php
@@ -48,15 +48,14 @@ public function viewMultiple(array $entities = array(), $view_mode = 'full', $la
       $derivative_id = $plugin->getDerivativeId();
       $configuration = $plugin->getConfiguration();
 
-      $cache_tags = array_merge(
+      $cache_tags = Cache::mergeTags(
         $this->getCacheTags(), // Block view builder cache tag.
         $entity->getCacheTags() // Block entity cache tag.
       );
-      $cache_tags = array_merge(
+      $cache_tags = Cache::mergeTags(
         $cache_tags,
         $plugin->getCacheTags() // Block plugin cache tags.
       );
-      $cache_tags = Cache::mergeTags($cache_tags);
 
       // Create the render array for the block as a whole.
       // @see template_preprocess_block().
diff --git a/core/modules/block_content/src/Tests/BlockContentCacheTagsTest.php b/core/modules/block_content/src/Tests/BlockContentCacheTagsTest.php
index 819ef90..c3a07c4 100644
--- a/core/modules/block_content/src/Tests/BlockContentCacheTagsTest.php
+++ b/core/modules/block_content/src/Tests/BlockContentCacheTagsTest.php
@@ -91,16 +91,14 @@ public function testBlock() {
     // @see \Drupal\block\BlockViewBuilder::viewMultiple()
     $expected_block_cache_keys = ['entity_view', 'block', $block->id()];
     $expected_block_cache_contexts = ['languages:' . LanguageInterface::TYPE_INTERFACE, 'theme'];
-    $expected_block_cache_tags = array_merge(['block_view', 'rendered'], $block->getCacheTags());
-    $expected_block_cache_tags = array_merge($expected_block_cache_tags, $block->getPlugin()->getCacheTags());
-    $expected_block_cache_tags = Cache::mergeTags($expected_block_cache_tags);
+    $expected_block_cache_tags = Cache::mergeTags(['block_view', 'rendered'], $block->getCacheTags());
+    $expected_block_cache_tags = Cache::mergeTags($expected_block_cache_tags, $block->getPlugin()->getCacheTags());
 
     // Expected contexts and tags for the BlockContent entity.
     // @see \Drupal\Core\Entity\EntityViewBuilder::getBuildDefaults().
     $expected_entity_cache_contexts = ['theme'];
-    $expected_entity_cache_tags = array_merge(['block_content_view'], $this->entity->getCacheTags());
-    $expected_entity_cache_tags = array_merge($expected_entity_cache_tags, $this->getAdditionalCacheTagsForEntity($this->entity));
-    $expected_entity_cache_tags = Cache::mergeTags($expected_entity_cache_tags);
+    $expected_entity_cache_tags = Cache::mergeTags(['block_content_view'], $this->entity->getCacheTags());
+    $expected_entity_cache_tags = Cache::mergeTags($expected_entity_cache_tags, $this->getAdditionalCacheTagsForEntity($this->entity));
 
     // Verify that what was render cached matches the above expectations.
     $cid = $this->createCacheId($expected_block_cache_keys, $expected_block_cache_contexts);
diff --git a/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php b/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php
index 7259dc9..f46ad04 100644
--- a/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php
+++ b/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php
@@ -350,38 +350,36 @@ public function testReferencedEntity() {
     }
 
     // Generate the cache tags for the (non) referencing entities.
-    $referencing_entity_cache_tags = array_merge(
+    $referencing_entity_cache_tags = Cache::mergeTags(
       $this->referencingEntity->getCacheTags(),
       \Drupal::entityManager()->getViewBuilder('entity_test')->getCacheTags()
     );
-    $referencing_entity_cache_tags = array_merge(
+    $referencing_entity_cache_tags = Cache::mergeTags(
       $referencing_entity_cache_tags,
       // Includes the main entity's cache tags, since this entity references it.
       $this->entity->getCacheTags()
     );
-    $referencing_entity_cache_tags = array_merge(
+    $referencing_entity_cache_tags = Cache::mergeTags(
       $referencing_entity_cache_tags,
       $this->getAdditionalCacheTagsForEntity($this->entity)
     );
-    $referencing_entity_cache_tags = array_merge(
+    $referencing_entity_cache_tags = Cache::mergeTags(
       $referencing_entity_cache_tags,
       $view_cache_tag
     );
-    $referencing_entity_cache_tags = array_merge(
+    $referencing_entity_cache_tags = Cache::mergeTags(
       $referencing_entity_cache_tags,
       ['rendered']
     );
-    $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags);
 
-    $non_referencing_entity_cache_tags = array_merge(
+    $non_referencing_entity_cache_tags = Cache::mergeTags(
       $this->nonReferencingEntity->getCacheTags(),
       \Drupal::entityManager()->getViewBuilder('entity_test')->getCacheTags()
     );
-    $non_referencing_entity_cache_tags = array_merge(
+    $non_referencing_entity_cache_tags = Cache::mergeTags(
       $non_referencing_entity_cache_tags,
       ['rendered']
     );
-    $non_referencing_entity_cache_tags = Cache::mergeTags($non_referencing_entity_cache_tags);
 
     // Generate the cache tags for all two possible entity listing paths.
     // 1. list cache tag only (listing query has no match)
@@ -391,27 +389,26 @@ public function testReferencedEntity() {
       $page_cache_tags
     );
 
-    $nonempty_entity_listing_cache_tags = array_merge(
+    $nonempty_entity_listing_cache_tags = Cache::mergeTags(
       $this->entity->getEntityType()->getListCacheTags(),
       $this->entity->getCacheTags()
     );
-    $nonempty_entity_listing_cache_tags = array_merge(
+    $nonempty_entity_listing_cache_tags = Cache::mergeTags(
       $nonempty_entity_listing_cache_tags,
       $this->getAdditionalCacheTagsForEntityListing($this->entity)
     );
-    $nonempty_entity_listing_cache_tags = array_merge(
+    $nonempty_entity_listing_cache_tags = Cache::mergeTags(
       $nonempty_entity_listing_cache_tags,
       $page_cache_tags
     );
-    $nonempty_entity_listing_cache_tags = Cache::mergeTags($nonempty_entity_listing_cache_tags);
+
     $this->pass("Test referencing entity.", 'Debug');
     $this->verifyPageCache($referencing_entity_url, 'MISS');
 
     // Verify a cache hit, but also the presence of the correct cache tags.
     $expectedTags = [];
-    $expectedTags = array_merge($referencing_entity_cache_tags, $page_cache_tags);
-    $expectedTags = array_merge($expectedTags, $page_cache_tags_referencing_entity);
-    $expectedTags = cache::mergeTags($expectedTags);
+    $expectedTags = Cache::mergeTags($referencing_entity_cache_tags, $page_cache_tags);
+    $expectedTags = Cache::mergeTags($expectedTags, $page_cache_tags_referencing_entity);
     $this->verifyPageCache($referencing_entity_url, 'HIT', $expectedTags);
 
     // Also verify the existence of an entity render cache entry.
@@ -442,9 +439,8 @@ public function testReferencedEntity() {
 
     // Verify a cache hit, but also the presence of the correct cache tags.
     $expectedTags = [];
-    $expectedTags = array_merge($referencing_entity_cache_tags, $page_cache_tags);
-    $expectedTags = array_merge($expectedTags, $page_cache_tags_referencing_entity);
-    $expectedTags =  Cache::mergeTags($expectedTags);
+    $expectedTags = Cache::mergeTags($referencing_entity_cache_tags, $page_cache_tags);
+    $expectedTags = Cache::mergeTags($expectedTags, $page_cache_tags_referencing_entity);
     $this->verifyPageCache($listing_url, 'HIT', $expectedTags);
 
     $this->pass("Test empty listing.", 'Debug');
@@ -664,25 +660,23 @@ public function testReferencedEntity() {
     $this->verifyPageCache($non_referencing_entity_url, 'HIT');
 
     // Verify cache hits.
-    $referencing_entity_cache_tags = array_merge(
+    $referencing_entity_cache_tags = Cache::mergeTags(
       $this->referencingEntity->getCacheTags(),
       \Drupal::entityManager()->getViewBuilder('entity_test')->getCacheTags()
     );
-    $referencing_entity_cache_tags = array_merge(
+    $referencing_entity_cache_tags = Cache::mergeTags(
       $referencing_entity_cache_tags,
       ['rendered']
     );
-    $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags);
 
-    $nonempty_entity_listing_cache_tags = array_merge(
+    $nonempty_entity_listing_cache_tags = Cache::mergeTags(
       $this->entity->getEntityType()->getListCacheTags(),
       $this->getAdditionalCacheTagsForEntityListing()
     );
-    $nonempty_entity_listing_cache_tags = array_merge(
+    $nonempty_entity_listing_cache_tags = Cache::mergeTags(
       $nonempty_entity_listing_cache_tags,
       $page_cache_tags
     );
-    $nonempty_entity_listing_cache_tags = Cache::mergeTags($nonempty_entity_listing_cache_tags);
 
     $this->verifyPageCache($referencing_entity_url, 'HIT', Cache::mergeTags($referencing_entity_cache_tags, $page_cache_tags));
     $this->verifyPageCache($listing_url, 'HIT', $page_cache_tags);
diff --git a/core/modules/system/src/Tests/Entity/EntityWithUriCacheTagsTestBase.php b/core/modules/system/src/Tests/Entity/EntityWithUriCacheTagsTestBase.php
index a410c49..abbcad3 100644
--- a/core/modules/system/src/Tests/Entity/EntityWithUriCacheTagsTestBase.php
+++ b/core/modules/system/src/Tests/Entity/EntityWithUriCacheTagsTestBase.php
@@ -56,10 +56,9 @@ public function testEntityUri() {
       if (count($additional_cache_contexts)) {
         $redirected_cid = $this->createCacheId($cache_keys, Cache::mergeContexts($entity_cache_contexts, $additional_cache_contexts));
       }
-      $expected_cache_tags = array_merge($cache_tag, $view_cache_tag);
-      $expected_cache_tags = array_merge($expected_cache_tags, $this->getAdditionalCacheTagsForEntity($this->entity));
-      $expected_cache_tags = array_merge($expected_cache_tags, array($render_cache_tag));
-      $expected_cache_tags = Cache::mergeTags($expected_cache_tags);
+      $expected_cache_tags = Cache::mergeTags($cache_tag, $view_cache_tag);
+      $expected_cache_tags = Cache::mergeTags($expected_cache_tags, $this->getAdditionalCacheTagsForEntity($this->entity));
+      $expected_cache_tags = Cache::mergeTags($expected_cache_tags, array($render_cache_tag));
       $this->verifyRenderCache($cid, $expected_cache_tags, $redirected_cid);
     }
 
diff --git a/core/modules/views/src/Tests/RenderCacheIntegrationTest.php b/core/modules/views/src/Tests/RenderCacheIntegrationTest.php
index 4a7e907..b1235b1 100644
--- a/core/modules/views/src/Tests/RenderCacheIntegrationTest.php
+++ b/core/modules/views/src/Tests/RenderCacheIntegrationTest.php
@@ -124,12 +124,7 @@ protected function assertCacheTagsForFieldBasedView($do_assert_views_caches) {
     $this->pass('Test pager');
     $this->pass('Page 1');
     \Drupal::request()->query->set('page', 0);
-    $tags_page_1 = array_merge($base_tags, $entities[1]->getCacheTags());
-    $tags_page_1 = array_merge($tags_page_1, $entities[2]->getCacheTags()
-    $tags_page_1 = array_mergemergeTags($tags_page_1, $entities[3]->getCacheTags()
-    $tags_page_1 = array_merge($tags_page_1, $entities[4]->getCacheTags()
-    $tags_page_1 = array_merge($tags_page_1, $entities[5]->getCacheTags());
-    $tags_page_1 = Cache::mergeTags($tags_page_1);
+    $tags_page_1 = Cache::mergeTags($base_tags, $entities[1]->getCacheTags(), $entities[2]->getCacheTags(), $entities[3]->getCacheTags(), $entities[4]->getCacheTags(), $entities[5]->getCacheTags());
     $this->assertViewsCacheTags($view, $tags_page_1, $do_assert_views_caches, $tags_page_1);
     $this->assertViewsCacheTagsFromStaticRenderArray($view, $tags_page_1, $do_assert_views_caches);
     $view->destroy();
@@ -259,9 +254,7 @@ protected function assertCacheTagsForEntityBasedView($do_assert_views_caches) {
     $entity->save();
 
     $result_tags_with_entity = Cache::mergeTags($base_tags, $entities[0]->getCacheTags());
-    $render_tags_with_entity = array_merge($base_render_tags, $entities[0]->getCacheTags());
-    $render_tags_with_entity = array_merge($render_tags_with_entity, ['entity_test_view']);
-    $render_tags_with_entity = Cache::mergeTags($render_tags_with_entity);
+    $render_tags_with_entity = Cache::mergeTags($base_render_tags, $entities[0]->getCacheTags(), ['entity_test_view']);
     $this->assertViewsCacheTags($view, $result_tags_with_entity, $do_assert_views_caches, $render_tags_with_entity);
     $this->assertViewsCacheTagsFromStaticRenderArray($view, $render_tags_with_entity, $do_assert_views_caches);
 
@@ -272,15 +265,9 @@ protected function assertCacheTagsForEntityBasedView($do_assert_views_caches) {
       $entity->save();
     }
 
-    $new_entities_cache_tags = array_merge($entities[1]->getCacheTags(), $entities[2]->getCacheTags());
-    $new_entities_cache_tags = array_merge($new_entities_cache_tags, $entities[3]->getCacheTags());
-    $new_entities_cache_tags = array_merge($new_entities_cache_tags, $entities[4]->getCacheTags());
-    $new_entities_cache_tags = array_merge($new_entities_cache_tags, $entities[5]->getCacheTags());
-    $new_entities_cache_tags = Cache::mergeTags($new_entities_cache_tags);
+    $new_entities_cache_tags = Cache::mergeTags($entities[1]->getCacheTags(), $entities[2]->getCacheTags(), $entities[3]->getCacheTags(), $entities[4]->getCacheTags(), $entities[5]->getCacheTags());
     $result_tags_page_1 = Cache::mergeTags($base_tags, $new_entities_cache_tags);
-    $render_tags_page_1 = array_merge($base_render_tags, $new_entities_cache_tags);
-    $render_tags_page_1 = array_merge($render_tags_page_1, ['entity_test_view']);
-    $render_tags_page_1 = Cache::mergeTags($render_tags_page_1);
+    $render_tags_page_1 = Cache::mergeTags($base_render_tags, $new_entities_cache_tags, ['entity_test_view']);
     $this->assertViewsCacheTags($view, $result_tags_page_1, $do_assert_views_caches, $render_tags_page_1);
     $this->assertViewsCacheTagsFromStaticRenderArray($view, $render_tags_page_1, $do_assert_views_caches);
   }