diff options
Diffstat (limited to 'absl/container/internal/raw_hash_set.cc')
| -rw-r--r-- | absl/container/internal/raw_hash_set.cc | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/absl/container/internal/raw_hash_set.cc b/absl/container/internal/raw_hash_set.cc index a6d9b7c0..b91d5a47 100644 --- a/absl/container/internal/raw_hash_set.cc +++ b/absl/container/internal/raw_hash_set.cc @@ -28,19 +28,18 @@ namespace container_internal { // A single block of empty control bytes for tables without any slots allocated. // This enables removing a branch in the hot path of find(). -// We have 17 bytes because there may be a generation counter. Any constant is -// fine for the generation counter. -alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[17] = { +alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[16] = { ctrl_t::kSentinel, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, - ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, - static_cast<ctrl_t>(0)}; + ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty}; #ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL constexpr size_t Group::kWidth; #endif +namespace { + // Returns "random" seed. inline size_t RandomSeed() { #ifdef ABSL_HAVE_THREAD_LOCAL @@ -58,6 +57,18 @@ inline size_t RandomSeed() { return value ^ static_cast<size_t>(reinterpret_cast<uintptr_t>(&counter)); } +} // namespace + +GenerationType* EmptyGeneration() { + if (SwisstableGenerationsEnabled()) { + constexpr size_t kNumEmptyGenerations = 1024; + static constexpr GenerationType kEmptyGenerations[kNumEmptyGenerations]{}; + return const_cast<GenerationType*>( + &kEmptyGenerations[RandomSeed() % kNumEmptyGenerations]); + } + return nullptr; +} + bool CommonFieldsGenerationInfoEnabled:: should_rehash_for_bug_detection_on_insert(const ctrl_t* ctrl, size_t capacity) const { |