Aggressively pipeline branches that have Arenas for performance.

PiperOrigin-RevId: 494917475

src/google/protobuf/arena.h

diff --git a/src/google/protobuf/arena.h b/src/google/protobuf/arena.h
index b60b7d0..8a7d1b4 100644
--- a/src/google/protobuf/arena.h
+++ b/src/google/protobuf/arena.h
@@ -271,7 +271,7 @@
   // is obtained from the arena).
   template <typename T, typename... Args>
   PROTOBUF_NDEBUG_INLINE static T* Create(Arena* arena, Args&&... args) {
-    if (arena == nullptr) {
+    if (PROTOBUF_PREDICT_FALSE(arena == nullptr)) {
       return new T(std::forward<Args>(args)...);
     }
     auto destructor =
@@ -320,10 +320,13 @@
                   "CreateArray requires a trivially destructible type");
     GOOGLE_ABSL_CHECK_LE(num_elements, std::numeric_limits<size_t>::max() / sizeof(T))
         << "Requested size is too large to fit into size_t.";
-    if (arena == nullptr) {
+    if (PROTOBUF_PREDICT_FALSE(arena == nullptr)) {
       return static_cast<T*>(::operator new[](num_elements * sizeof(T)));
     } else {
-      return arena->CreateInternalRawArray<T>(num_elements);
+      // We count on compiler to realize that if sizeof(T) is a multiple of
+      // 8 AlignUpTo can be elided.
+      return static_cast<T*>(
+          arena->AllocateAlignedForArray(sizeof(T) * num_elements, alignof(T)));
     }
   }
 
@@ -598,18 +601,6 @@
                                    std::forward<Args>(args)...);
   }
 
-  // Just allocate the required size for the given type assuming the
-  // type has a trivial constructor.
-  template <typename T>
-  PROTOBUF_NDEBUG_INLINE T* CreateInternalRawArray(size_t num_elements) {
-    GOOGLE_ABSL_CHECK_LE(num_elements, std::numeric_limits<size_t>::max() / sizeof(T))
-        << "Requested size is too large to fit into size_t.";
-    // We count on compiler to realize that if sizeof(T) is a multiple of
-    // 8 AlignUpTo can be elided.
-    const size_t n = sizeof(T) * num_elements;
-    return static_cast<T*>(AllocateAlignedForArray(n, alignof(T)));
-  }
-
   template <typename T, typename... Args>
   PROTOBUF_NDEBUG_INLINE T* DoCreateMessage(Args&&... args) {
     return InternalHelper<T>::Construct(