Export of internal Abseil changes

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23500704dd7c2642fad49f88c07ce41ebaab12e4 by Abseil Team <absl-team@google.com>:

Change fetch_add() to store(1 + load())

As there is only one concurrent writer to the Info struct, we can avoid using
the more expensive fetch_add() function.

PiperOrigin-RevId: 329523785

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79e5018dba2e117ad89b76367165a604b3f24045 by Abseil Team <absl-team@google.com>:

Record rehash count in hashtablez

This will help identify which containers could benefit from a reserve call.

PiperOrigin-RevId: 329510552

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e327e54b805d67556f934fa7f7dc2d4e72fa066a by Abseil Team <absl-team@google.com>:

Fix -Wsign-compare issues.

These lines could theoretically have overflowed in cases of very large stack
traces etc. Very unlikely, but this was causing warnings when built with
-Wsign-compare, which we intend to enable with Chromium.

In none of these three cases is it trivial to switch to a range-based for loop.

PiperOrigin-RevId: 329415195

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08aca2fc75e8b3ad1201849987b64148fe48f283 by Xiaoyi Zhang <zhangxy@google.com>:

Release absl::StatusOr.

PiperOrigin-RevId: 329353348

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bf4d2a7f8b089e2adf14d32b0e39de0a981005c3 by Xiaoyi Zhang <zhangxy@google.com>:

Internal change

PiperOrigin-RevId: 329337031

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42fa7d2fb993bbfc344954227cf1eeb801eca065 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 329099807
GitOrigin-RevId: 23500704dd7c2642fad49f88c07ce41ebaab12e4
Change-Id: I6713e4ca3bb0ab2ced5e487827ae036ab8ac61f1

3 files changed, 17 insertions, 2 deletions

diff --git a/absl/container/internal/hashtablez_sampler.cc b/absl/container/internal/hashtablez_sampler.cc
index 886524f1..e4484fbb 100644
--- a/absl/container/internal/hashtablez_sampler.cc
+++ b/absl/container/internal/hashtablez_sampler.cc
@@ -67,6 +67,7 @@ void HashtablezInfo::PrepareForSampling() {
   capacity.store(0, std::memory_order_relaxed);
   size.store(0, std::memory_order_relaxed);
   num_erases.store(0, std::memory_order_relaxed);
+  num_rehashes.store(0, std::memory_order_relaxed);
   max_probe_length.store(0, std::memory_order_relaxed);
   total_probe_length.store(0, std::memory_order_relaxed);
   hashes_bitwise_or.store(0, std::memory_order_relaxed);
diff --git a/absl/container/internal/hashtablez_sampler.h b/absl/container/internal/hashtablez_sampler.h
index e140ee00..b2a30c9a 100644
--- a/absl/container/internal/hashtablez_sampler.h
+++ b/absl/container/internal/hashtablez_sampler.h
@@ -73,6 +73,7 @@ struct HashtablezInfo {
   std::atomic<size_t> capacity;
   std::atomic<size_t> size;
   std::atomic<size_t> num_erases;
+  std::atomic<size_t> num_rehashes;
   std::atomic<size_t> max_probe_length;
   std::atomic<size_t> total_probe_length;
   std::atomic<size_t> hashes_bitwise_or;
@@ -105,6 +106,11 @@ inline void RecordRehashSlow(HashtablezInfo* info, size_t total_probe_length) {
 #endif
   info->total_probe_length.store(total_probe_length, std::memory_order_relaxed);
   info->num_erases.store(0, std::memory_order_relaxed);
+  // There is only one concurrent writer, so `load` then `store` is sufficient
+  // instead of using `fetch_add`.
+  info->num_rehashes.store(
+      1 + info->num_rehashes.load(std::memory_order_relaxed),
+      std::memory_order_relaxed);
 }
 
 inline void RecordStorageChangedSlow(HashtablezInfo* info, size_t size,
@@ -113,7 +119,8 @@ inline void RecordStorageChangedSlow(HashtablezInfo* info, size_t size,
   info->capacity.store(capacity, std::memory_order_relaxed);
   if (size == 0) {
     // This is a clear, reset the total/num_erases too.
-    RecordRehashSlow(info, 0);
+    info->total_probe_length.store(0, std::memory_order_relaxed);
+    info->num_erases.store(0, std::memory_order_relaxed);
   }
 }
 
@@ -122,7 +129,11 @@ void RecordInsertSlow(HashtablezInfo* info, size_t hash,
 
 inline void RecordEraseSlow(HashtablezInfo* info) {
   info->size.fetch_sub(1, std::memory_order_relaxed);
-  info->num_erases.fetch_add(1, std::memory_order_relaxed);
+  // There is only one concurrent writer, so `load` then `store` is sufficient
+  // instead of using `fetch_add`.
+  info->num_erases.store(
+      1 + info->num_erases.load(std::memory_order_relaxed),
+      std::memory_order_relaxed);
 }
 
 HashtablezInfo* SampleSlow(int64_t* next_sample);
diff --git a/absl/container/internal/hashtablez_sampler_test.cc b/absl/container/internal/hashtablez_sampler_test.cc
index b4c4ff92..04a26cb7 100644
--- a/absl/container/internal/hashtablez_sampler_test.cc
+++ b/absl/container/internal/hashtablez_sampler_test.cc
@@ -76,6 +76,7 @@ TEST(HashtablezInfoTest, PrepareForSampling) {
   EXPECT_EQ(info.capacity.load(), 0);
   EXPECT_EQ(info.size.load(), 0);
   EXPECT_EQ(info.num_erases.load(), 0);
+  EXPECT_EQ(info.num_rehashes.load(), 0);
   EXPECT_EQ(info.max_probe_length.load(), 0);
   EXPECT_EQ(info.total_probe_length.load(), 0);
   EXPECT_EQ(info.hashes_bitwise_or.load(), 0);
@@ -95,6 +96,7 @@ TEST(HashtablezInfoTest, PrepareForSampling) {
   EXPECT_EQ(info.capacity.load(), 0);
   EXPECT_EQ(info.size.load(), 0);
   EXPECT_EQ(info.num_erases.load(), 0);
+  EXPECT_EQ(info.num_rehashes.load(), 0);
   EXPECT_EQ(info.max_probe_length.load(), 0);
   EXPECT_EQ(info.total_probe_length.load(), 0);
   EXPECT_EQ(info.hashes_bitwise_or.load(), 0);
@@ -167,6 +169,7 @@ TEST(HashtablezInfoTest, RecordRehash) {
   EXPECT_EQ(info.size.load(), 2);
   EXPECT_EQ(info.total_probe_length.load(), 3);
   EXPECT_EQ(info.num_erases.load(), 0);
+  EXPECT_EQ(info.num_rehashes.load(), 1);
 }
 
 #if defined(ABSL_HASHTABLEZ_SAMPLE)