Early return from destroy_slots for trivially destructible types in flat_hash_{*}.

PiperOrigin-RevId: 602813933
Change-Id: I744fe438281755a141b2fd47e54ab9c6c0fad5a3

1 files changed, 14 insertions, 1 deletions

diff --git a/absl/container/internal/container_memory.h b/absl/container/internal/container_memory.h
index 3262d4eb..d86d7b80 100644
--- a/absl/container/internal/container_memory.h
+++ b/absl/container/internal/container_memory.h
@@ -68,6 +68,18 @@ void* Allocate(Alloc* alloc, size_t n) {
   return p;
 }
 
+// Returns true if the destruction of the value with given Allocator will be
+// trivial.
+template <class Allocator, class ValueType>
+constexpr auto IsDestructionTrivial() {
+  constexpr bool result =
+      std::is_trivially_destructible<ValueType>::value &&
+      std::is_same<typename absl::allocator_traits<
+                       Allocator>::template rebind_alloc<char>,
+                   std::allocator<char>>::value;
+  return std::integral_constant<bool, result>();
+}
+
 // The pointer must have been previously obtained by calling
 // Allocate<Alignment>(alloc, n).
 template <size_t Alignment, class Alloc>
@@ -414,12 +426,13 @@ struct map_slot_policy {
   }
 
   template <class Allocator>
-  static void destroy(Allocator* alloc, slot_type* slot) {
+  static auto destroy(Allocator* alloc, slot_type* slot) {
     if (kMutableKeys::value) {
       absl::allocator_traits<Allocator>::destroy(*alloc, &slot->mutable_value);
     } else {
       absl::allocator_traits<Allocator>::destroy(*alloc, &slot->value);
     }
+    return IsDestructionTrivial<Allocator, value_type>();
   }
 
   template <class Allocator>