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authorGravatar Evan Brown <ezb@google.com>2022-10-03 10:51:40 -0700
committerGravatar Copybara-Service <copybara-worker@google.com>2022-10-03 10:52:25 -0700
commitf8e0ff7f33338c2874b75e45e4ea5abbfafb954c (patch)
tree343d800108e96f67e578ebc3f614055a2d997065
parentd277a48d4cd998a9d8937b99fe6ee28f7adb0484 (diff)
Use trivial relocation for transfers in swisstable and b-tree.
PiperOrigin-RevId: 478547898 Change-Id: Ie20cd0a49df042be912888ee238333a5f5fa0404
-rw-r--r--absl/container/internal/common_policy_traits.h15
-rw-r--r--absl/container/internal/common_policy_traits_test.cc9
-rw-r--r--absl/container/internal/container_memory.h13
3 files changed, 31 insertions, 6 deletions
diff --git a/absl/container/internal/common_policy_traits.h b/absl/container/internal/common_policy_traits.h
index cc2e89ba..c99e68f4 100644
--- a/absl/container/internal/common_policy_traits.h
+++ b/absl/container/internal/common_policy_traits.h
@@ -16,6 +16,7 @@
#define ABSL_CONTAINER_INTERNAL_COMMON_POLICY_TRAITS_H_
#include <cstddef>
+#include <cstring>
#include <memory>
#include <new>
#include <type_traits>
@@ -32,7 +33,8 @@ template <class Policy, class = void>
struct common_policy_traits {
// The actual object stored in the container.
using slot_type = typename Policy::slot_type;
-
+ using reference = decltype(Policy::element(std::declval<slot_type*>()));
+ using value_type = typename std::remove_reference<reference>::type;
// PRECONDITION: `slot` is UNINITIALIZED
// POSTCONDITION: `slot` is INITIALIZED
@@ -89,6 +91,17 @@ struct common_policy_traits {
template <class Alloc>
static void transfer_impl(Alloc* alloc, slot_type* new_slot,
slot_type* old_slot, char) {
+#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
+ if (absl::is_trivially_relocatable<value_type>()) {
+ // TODO(b/247130232): remove cast after fixing class-memaccess warning.
+ std::memcpy(static_cast<void*>(
+ std::launder(const_cast<std::remove_const_t<value_type>*>(
+ &element(new_slot)))),
+ &element(old_slot), sizeof(value_type));
+ return;
+ }
+#endif
+
construct(alloc, new_slot, std::move(element(old_slot)));
destroy(alloc, old_slot);
}
diff --git a/absl/container/internal/common_policy_traits_test.cc b/absl/container/internal/common_policy_traits_test.cc
index 768d870e..5eaa4aae 100644
--- a/absl/container/internal/common_policy_traits_test.cc
+++ b/absl/container/internal/common_policy_traits_test.cc
@@ -27,7 +27,7 @@ namespace container_internal {
namespace {
using ::testing::MockFunction;
-using ::testing::Return;
+using ::testing::AnyNumber;
using ::testing::ReturnRef;
using Slot = int;
@@ -101,9 +101,10 @@ TEST_F(Test, element) {
TEST_F(Test, without_transfer) {
int b = 42;
- EXPECT_CALL(element, Call(&b)).WillOnce(::testing::ReturnRef(b));
- EXPECT_CALL(construct, Call(&alloc, &a, b));
- EXPECT_CALL(destroy, Call(&alloc, &b));
+ EXPECT_CALL(element, Call(&a)).Times(AnyNumber()).WillOnce(ReturnRef(a));
+ EXPECT_CALL(element, Call(&b)).WillOnce(ReturnRef(b));
+ EXPECT_CALL(construct, Call(&alloc, &a, b)).Times(AnyNumber());
+ EXPECT_CALL(destroy, Call(&alloc, &b)).Times(AnyNumber());
common_policy_traits<PolicyWithoutOptionalOps>::transfer(&alloc, &a, &b);
}
diff --git a/absl/container/internal/container_memory.h b/absl/container/internal/container_memory.h
index 00e9f6d7..c29c533b 100644
--- a/absl/container/internal/container_memory.h
+++ b/absl/container/internal/container_memory.h
@@ -17,6 +17,7 @@
#include <cassert>
#include <cstddef>
+#include <cstring>
#include <memory>
#include <new>
#include <tuple>
@@ -340,7 +341,8 @@ template <class K, class V>
struct map_slot_policy {
using slot_type = map_slot_type<K, V>;
using value_type = std::pair<const K, V>;
- using mutable_value_type = std::pair<K, V>;
+ using mutable_value_type =
+ std::pair<absl::remove_const_t<K>, absl::remove_const_t<V>>;
private:
static void emplace(slot_type* slot) {
@@ -424,6 +426,15 @@ struct map_slot_policy {
static void transfer(Allocator* alloc, slot_type* new_slot,
slot_type* old_slot) {
emplace(new_slot);
+#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
+ if (absl::is_trivially_relocatable<value_type>()) {
+ // TODO(b/247130232): remove cast after fixing class-memaccess warning.
+ std::memcpy(static_cast<void*>(std::launder(&new_slot->value)),
+ &old_slot->value, sizeof(value_type));
+ return;
+ }
+#endif
+
if (kMutableKeys::value) {
absl::allocator_traits<Allocator>::construct(
*alloc, &new_slot->mutable_value, std::move(old_slot->mutable_value));