From 7339447a7f457f1d8efa6322c971e71afc304d32 Mon Sep 17 00:00:00 2001
From: Abseil Team <absl-team@google.com>
Date: Thu, 1 Feb 2024 11:43:33 -0800
Subject: Optimize raw_hash_set destructor.

There are three optimizations here:
1. Early exit in case all slots were destroyed. especially useful for empty tables.
2. MatchFull is used in order to iterate over all full slots.
3. Portable group is used for `MatchFull` in the case of small table.

PiperOrigin-RevId: 603434899
Change-Id: I40bc90d17331d579cfbb1b4e0693f0913e5c38e4
---
 absl/container/internal/raw_hash_set_test.cc | 35 ++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'absl/container/internal/raw_hash_set_test.cc')

diff --git a/absl/container/internal/raw_hash_set_test.cc b/absl/container/internal/raw_hash_set_test.cc
index 7ec72b22..5852904f 100644
--- a/absl/container/internal/raw_hash_set_test.cc
+++ b/absl/container/internal/raw_hash_set_test.cc
@@ -63,6 +63,10 @@ ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 struct RawHashSetTestOnlyAccess {
+  template <typename C>
+  static auto GetCommon(const C& c) -> decltype(c.common()) {
+    return c.common();
+  }
   template <typename C>
   static auto GetSlots(const C& c) -> decltype(c.slot_array()) {
     return c.slot_array();
@@ -2741,6 +2745,37 @@ TEST(Table, CountedHash) {
   }
 }
 
+TEST(Table, IterateOverFullSlotsEmpty) {
+  IntTable t;
+  auto fail_if_any = [](int64_t* i) { FAIL() << "expected no slots " << i; };
+  container_internal::IterateOverFullSlots(
+      RawHashSetTestOnlyAccess::GetCommon(t),
+      RawHashSetTestOnlyAccess::GetSlots(t), fail_if_any);
+  for (size_t i = 0; i < 256; ++i) {
+    t.reserve(i);
+    container_internal::IterateOverFullSlots(
+        RawHashSetTestOnlyAccess::GetCommon(t),
+        RawHashSetTestOnlyAccess::GetSlots(t), fail_if_any);
+  }
+}
+
+TEST(Table, IterateOverFullSlotsFull) {
+  IntTable t;
+
+  std::vector<int64_t> expected_slots;
+  for (int64_t i = 0; i < 128; ++i) {
+    t.insert(i);
+    expected_slots.push_back(i);
+
+    std::vector<int64_t> slots;
+    container_internal::IterateOverFullSlots(
+        RawHashSetTestOnlyAccess::GetCommon(t),
+        RawHashSetTestOnlyAccess::GetSlots(t),
+        [&slots](int64_t* i) { slots.push_back(*i); });
+    EXPECT_THAT(slots, testing::UnorderedElementsAreArray(expected_slots));
+  }
+}
+
 }  // namespace
 }  // namespace container_internal
 ABSL_NAMESPACE_END
-- 
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