From db5c79932e16e97e8b2f9ecd0e74f99f0e74e0d7 Mon Sep 17 00:00:00 2001
From: Abseil Team <absl-team@google.com>
Date: Mon, 20 Nov 2023 14:57:43 -0800
Subject: Make `FlatHashMapPolicy` return `std::true_type` for relocatable
 objects.

This reduces produced binary size and can trigger even more optimizations in the future.

PiperOrigin-RevId: 584136517
Change-Id: I3854833799f88f28b755ec53132925f0c3d468ab
---
 absl/container/internal/container_memory.h | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

(limited to 'absl/container/internal/container_memory.h')

diff --git a/absl/container/internal/container_memory.h b/absl/container/internal/container_memory.h
index f59ca4ee..3262d4eb 100644
--- a/absl/container/internal/container_memory.h
+++ b/absl/container/internal/container_memory.h
@@ -122,10 +122,10 @@ auto TupleRefImpl(T&& t, absl::index_sequence<Is...>)
 // Returns a tuple of references to the elements of the input tuple. T must be a
 // tuple.
 template <class T>
-auto TupleRef(T&& t) -> decltype(
-    TupleRefImpl(std::forward<T>(t),
-                 absl::make_index_sequence<
-                     std::tuple_size<typename std::decay<T>::type>::value>())) {
+auto TupleRef(T&& t) -> decltype(TupleRefImpl(
+    std::forward<T>(t),
+    absl::make_index_sequence<
+        std::tuple_size<typename std::decay<T>::type>::value>())) {
   return TupleRefImpl(
       std::forward<T>(t),
       absl::make_index_sequence<
@@ -156,8 +156,8 @@ void ConstructFromTuple(Alloc* alloc, T* ptr, Tuple&& t) {
 // Constructs T using the args specified in the tuple and calls F with the
 // constructed value.
 template <class T, class Tuple, class F>
-decltype(std::declval<F>()(std::declval<T>())) WithConstructed(
-    Tuple&& t, F&& f) {
+decltype(std::declval<F>()(std::declval<T>())) WithConstructed(Tuple&& t,
+                                                               F&& f) {
   return memory_internal::WithConstructedImpl<T>(
       std::forward<Tuple>(t),
       absl::make_index_sequence<
@@ -423,16 +423,19 @@ struct map_slot_policy {
   }
 
   template <class Allocator>
-  static void transfer(Allocator* alloc, slot_type* new_slot,
+  static auto transfer(Allocator* alloc, slot_type* new_slot,
                        slot_type* old_slot) {
+    auto is_relocatable =
+        typename absl::is_trivially_relocatable<value_type>::type();
+
     emplace(new_slot);
 #if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
-    if (absl::is_trivially_relocatable<value_type>()) {
+    if (is_relocatable) {
       // TODO(b/247130232,b/251814870): remove casts after fixing warnings.
       std::memcpy(static_cast<void*>(std::launder(&new_slot->value)),
                   static_cast<const void*>(&old_slot->value),
                   sizeof(value_type));
-      return;
+      return is_relocatable;
     }
 #endif
 
@@ -444,6 +447,7 @@ struct map_slot_policy {
                                                    std::move(old_slot->value));
     }
     destroy(alloc, old_slot);
+    return is_relocatable;
   }
 };
 
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