Merge new upstream LTS 20240722.0

1 files changed, 334 insertions, 71 deletions

diff --git a/absl/container/internal/raw_hash_set.cc b/absl/container/internal/raw_hash_set.cc
index 9f8ea519..1cae0381 100644
--- a/absl/container/internal/raw_hash_set.cc
+++ b/absl/container/internal/raw_hash_set.cc
@@ -23,19 +23,24 @@
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
 #include "absl/base/dynamic_annotations.h"
+#include "absl/base/internal/endian.h"
+#include "absl/base/optimization.h"
 #include "absl/container/internal/container_memory.h"
+#include "absl/container/internal/hashtablez_sampler.h"
 #include "absl/hash/hash.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
-// We have space for `growth_left` before a single block of control bytes. A
+// Represents a control byte corresponding to a full slot with arbitrary hash.
+constexpr ctrl_t ZeroCtrlT() { return static_cast<ctrl_t>(0); }
+
+// We have space for `growth_info` before a single block of control bytes. A
 // single block of empty control bytes for tables without any slots allocated.
 // This enables removing a branch in the hot path of find(). In order to ensure
 // that the control bytes are aligned to 16, we have 16 bytes before the control
-// bytes even though growth_left only needs 8.
-constexpr ctrl_t ZeroCtrlT() { return static_cast<ctrl_t>(0); }
+// bytes even though growth_info only needs 8.
 alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[32] = {
     ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
     ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),
@@ -46,6 +51,18 @@ alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[32] = {
     ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,
     ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty};
 
+// We need one full byte followed by a sentinel byte for iterator::operator++ to
+// work. We have a full group after kSentinel to be safe (in case operator++ is
+// changed to read a full group).
+ABSL_CONST_INIT ABSL_DLL const ctrl_t kSooControl[17] = {
+    ZeroCtrlT(),    ctrl_t::kSentinel, ZeroCtrlT(),    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_assert(NumControlBytes(SooCapacity()) <= 17,
+              "kSooControl capacity too small");
+
 #ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
 constexpr size_t Group::kWidth;
 #endif
@@ -104,10 +121,25 @@ bool CommonFieldsGenerationInfoEnabled::should_rehash_for_bug_detection_on_move(
   return ShouldRehashForBugDetection(ctrl, capacity);
 }
 
-bool ShouldInsertBackwards(size_t hash, const ctrl_t* ctrl) {
+bool ShouldInsertBackwardsForDebug(size_t capacity, size_t hash,
+                                   const ctrl_t* ctrl) {
   // To avoid problems with weak hashes and single bit tests, we use % 13.
   // TODO(kfm,sbenza): revisit after we do unconditional mixing
-  return (H1(hash, ctrl) ^ RandomSeed()) % 13 > 6;
+  return !is_small(capacity) && (H1(hash, ctrl) ^ RandomSeed()) % 13 > 6;
+}
+
+size_t PrepareInsertAfterSoo(size_t hash, size_t slot_size,
+                             CommonFields& common) {
+  assert(common.capacity() == NextCapacity(SooCapacity()));
+  // After resize from capacity 1 to 3, we always have exactly the slot with
+  // index 1 occupied, so we need to insert either at index 0 or index 2.
+  assert(HashSetResizeHelper::SooSlotIndex() == 1);
+  PrepareInsertCommon(common);
+  const size_t offset = H1(hash, common.control()) & 2;
+  common.growth_info().OverwriteEmptyAsFull();
+  SetCtrlInSingleGroupTable(common, offset, H2(hash), slot_size);
+  common.infoz().RecordInsert(hash, /*distance_from_desired=*/0);
+  return offset;
 }
 
 void ConvertDeletedToEmptyAndFullToDeleted(ctrl_t* ctrl, size_t capacity) {
@@ -128,6 +160,8 @@ FindInfo find_first_non_full_outofline(const CommonFields& common,
   return find_first_non_full(common, hash);
 }
 
+namespace {
+
 // Returns the address of the slot just after slot assuming each slot has the
 // specified size.
 static inline void* NextSlot(void* slot, size_t slot_size) {
@@ -140,8 +174,22 @@ static inline void* PrevSlot(void* slot, size_t slot_size) {
   return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot) - slot_size);
 }
 
+// Finds guaranteed to exists empty slot from the given position.
+// NOTE: this function is almost never triggered inside of the
+// DropDeletesWithoutResize, so we keep it simple.
+// The table is rather sparse, so empty slot will be found very quickly.
+size_t FindEmptySlot(size_t start, size_t end, const ctrl_t* ctrl) {
+  for (size_t i = start; i < end; ++i) {
+    if (IsEmpty(ctrl[i])) {
+      return i;
+    }
+  }
+  assert(false && "no empty slot");
+  return ~size_t{};
+}
+
 void DropDeletesWithoutResize(CommonFields& common,
-                              const PolicyFunctions& policy, void* tmp_space) {
+                              const PolicyFunctions& policy) {
   void* set = &common;
   void* slot_array = common.slot_array();
   const size_t capacity = common.capacity();
@@ -165,17 +213,28 @@ void DropDeletesWithoutResize(CommonFields& common,
   //       repeat procedure for current slot with moved from element (target)
   ctrl_t* ctrl = common.control();
   ConvertDeletedToEmptyAndFullToDeleted(ctrl, capacity);
+  const void* hash_fn = policy.hash_fn(common);
   auto hasher = policy.hash_slot;
   auto transfer = policy.transfer;
   const size_t slot_size = policy.slot_size;
 
   size_t total_probe_length = 0;
   void* slot_ptr = SlotAddress(slot_array, 0, slot_size);
+
+  // The index of an empty slot that can be used as temporary memory for
+  // the swap operation.
+  constexpr size_t kUnknownId = ~size_t{};
+  size_t tmp_space_id = kUnknownId;
+
   for (size_t i = 0; i != capacity;
        ++i, slot_ptr = NextSlot(slot_ptr, slot_size)) {
     assert(slot_ptr == SlotAddress(slot_array, i, slot_size));
+    if (IsEmpty(ctrl[i])) {
+      tmp_space_id = i;
+      continue;
+    }
     if (!IsDeleted(ctrl[i])) continue;
-    const size_t hash = (*hasher)(set, slot_ptr);
+    const size_t hash = (*hasher)(hash_fn, slot_ptr);
     const FindInfo target = find_first_non_full(common, hash);
     const size_t new_i = target.offset;
     total_probe_length += target.probe_length;
@@ -202,16 +261,26 @@ void DropDeletesWithoutResize(CommonFields& common,
       SetCtrl(common, new_i, H2(hash), slot_size);
       (*transfer)(set, new_slot_ptr, slot_ptr);
       SetCtrl(common, i, ctrl_t::kEmpty, slot_size);
+      // Initialize or change empty space id.
+      tmp_space_id = i;
     } else {
       assert(IsDeleted(ctrl[new_i]));
       SetCtrl(common, new_i, H2(hash), slot_size);
       // Until we are done rehashing, DELETED marks previously FULL slots.
 
+      if (tmp_space_id == kUnknownId) {
+        tmp_space_id = FindEmptySlot(i + 1, capacity, ctrl);
+      }
+      void* tmp_space = SlotAddress(slot_array, tmp_space_id, slot_size);
+      SanitizerUnpoisonMemoryRegion(tmp_space, slot_size);
+
       // Swap i and new_i elements.
       (*transfer)(set, tmp_space, new_slot_ptr);
       (*transfer)(set, new_slot_ptr, slot_ptr);
       (*transfer)(set, slot_ptr, tmp_space);
 
+      SanitizerPoisonMemoryRegion(tmp_space, slot_size);
+
       // repeat the processing of the ith slot
       --i;
       slot_ptr = PrevSlot(slot_ptr, slot_size);
@@ -238,6 +307,8 @@ static bool WasNeverFull(CommonFields& c, size_t index) {
              Group::kWidth;
 }
 
+}  // namespace
+
 void EraseMetaOnly(CommonFields& c, size_t index, size_t slot_size) {
   assert(IsFull(c.control()[index]) && "erasing a dangling iterator");
   c.decrement_size();
@@ -245,17 +316,19 @@ void EraseMetaOnly(CommonFields& c, size_t index, size_t slot_size) {
 
   if (WasNeverFull(c, index)) {
     SetCtrl(c, index, ctrl_t::kEmpty, slot_size);
-    c.set_growth_left(c.growth_left() + 1);
+    c.growth_info().OverwriteFullAsEmpty();
     return;
   }
 
+  c.growth_info().OverwriteFullAsDeleted();
   SetCtrl(c, index, ctrl_t::kDeleted, slot_size);
 }
 
 void ClearBackingArray(CommonFields& c, const PolicyFunctions& policy,
-                       bool reuse) {
+                       bool reuse, bool soo_enabled) {
   c.set_size(0);
   if (reuse) {
+    assert(!soo_enabled || c.capacity() > SooCapacity());
     ResetCtrl(c, policy.slot_size);
     ResetGrowthLeft(c);
     c.infoz().RecordStorageChanged(0, c.capacity());
@@ -263,118 +336,308 @@ void ClearBackingArray(CommonFields& c, const PolicyFunctions& policy,
     // We need to record infoz before calling dealloc, which will unregister
     // infoz.
     c.infoz().RecordClearedReservation();
-    c.infoz().RecordStorageChanged(0, 0);
+    c.infoz().RecordStorageChanged(0, soo_enabled ? SooCapacity() : 0);
     (*policy.dealloc)(c, policy);
-    c.set_control(EmptyGroup());
-    c.set_generation_ptr(EmptyGeneration());
-    c.set_slots(nullptr);
-    c.set_capacity(0);
+    c = soo_enabled ? CommonFields{soo_tag_t{}} : CommonFields{};
   }
 }
 
 void HashSetResizeHelper::GrowIntoSingleGroupShuffleControlBytes(
-    ctrl_t* new_ctrl, size_t new_capacity) const {
+    ctrl_t* __restrict new_ctrl, size_t new_capacity) const {
   assert(is_single_group(new_capacity));
   constexpr size_t kHalfWidth = Group::kWidth / 2;
+  constexpr size_t kQuarterWidth = Group::kWidth / 4;
   assert(old_capacity_ < kHalfWidth);
+  static_assert(sizeof(uint64_t) >= kHalfWidth,
+                "Group size is too large. The ctrl bytes for half a group must "
+                "fit into a uint64_t for this implementation.");
+  static_assert(sizeof(uint64_t) <= Group::kWidth,
+                "Group size is too small. The ctrl bytes for a group must "
+                "cover a uint64_t for this implementation.");
 
   const size_t half_old_capacity = old_capacity_ / 2;
 
   // NOTE: operations are done with compile time known size = kHalfWidth.
   // Compiler optimizes that into single ASM operation.
 
-  // Copy second half of bytes to the beginning.
-  // We potentially copy more bytes in order to have compile time known size.
-  // Mirrored bytes from the old_ctrl_ will also be copied.
-  // In case of old_capacity_ == 3, we will copy 1st element twice.
+  // Load the bytes from half_old_capacity + 1. This contains the last half of
+  // old_ctrl bytes, followed by the sentinel byte, and then the first half of
+  // the cloned bytes. This effectively shuffles the control bytes.
+  uint64_t copied_bytes = 0;
+  copied_bytes =
+      absl::little_endian::Load64(old_ctrl() + half_old_capacity + 1);
+
+  // We change the sentinel byte to kEmpty before storing to both the start of
+  // the new_ctrl, and past the end of the new_ctrl later for the new cloned
+  // bytes. Note that this is faster than setting the sentinel byte to kEmpty
+  // after the copy directly in new_ctrl because we are limited on store
+  // bandwidth.
+  constexpr uint64_t kEmptyXorSentinel =
+      static_cast<uint8_t>(ctrl_t::kEmpty) ^
+      static_cast<uint8_t>(ctrl_t::kSentinel);
+  const uint64_t mask_convert_old_sentinel_to_empty =
+      kEmptyXorSentinel << (half_old_capacity * 8);
+  copied_bytes ^= mask_convert_old_sentinel_to_empty;
+
+  // Copy second half of bytes to the beginning. This correctly sets the bytes
+  // [0, old_capacity]. We potentially copy more bytes in order to have compile
+  // time known size. Mirrored bytes from the old_ctrl() will also be copied. In
+  // case of old_capacity_ == 3, we will copy 1st element twice.
   // Examples:
+  // (old capacity = 1)
   // old_ctrl = 0S0EEEEEEE...
-  // new_ctrl = S0EEEEEEEE...
+  // new_ctrl = E0EEEEEE??...
   //
-  // old_ctrl = 01S01EEEEE...
-  // new_ctrl = 1S01EEEEEE...
+  // (old capacity = 3)
+  // old_ctrl = 012S012EEEEE...
+  // new_ctrl = 12E012EE????...
   //
+  // (old capacity = 7)
   // old_ctrl = 0123456S0123456EE...
-  // new_ctrl = 456S0123?????????...
-  std::memcpy(new_ctrl, old_ctrl_ + half_old_capacity + 1, kHalfWidth);
-  // Clean up copied kSentinel from old_ctrl.
-  new_ctrl[half_old_capacity] = ctrl_t::kEmpty;
-
-  // Clean up damaged or uninitialized bytes.
-
-  // Clean bytes after the intended size of the copy.
-  // Example:
-  // new_ctrl = 1E01EEEEEEE????
-  // *new_ctrl= 1E0EEEEEEEE????
-  // position      /
-  std::memset(new_ctrl + old_capacity_ + 1, static_cast<int8_t>(ctrl_t::kEmpty),
-              kHalfWidth);
-  // Clean non-mirrored bytes that are not initialized.
-  // For small old_capacity that may be inside of mirrored bytes zone.
+  // new_ctrl = 456E0123?????????...
+  absl::little_endian::Store64(new_ctrl, copied_bytes);
+
+  // Set the space [old_capacity + 1, new_capacity] to empty as these bytes will
+  // not be written again. This is safe because
+  // NumControlBytes = new_capacity + kWidth and new_capacity >=
+  // old_capacity+1.
   // Examples:
-  // new_ctrl = 1E0EEEEEEEE??????????....
-  // *new_ctrl= 1E0EEEEEEEEEEEEE?????....
-  // position           /
+  // (old_capacity = 3, new_capacity = 15)
+  // new_ctrl  = 12E012EE?????????????...??
+  // *new_ctrl = 12E0EEEEEEEEEEEEEEEE?...??
+  // position        /          S
   //
-  // new_ctrl = 456E0123???????????...
-  // *new_ctrl= 456E0123EEEEEEEE???...
-  // position           /
-  std::memset(new_ctrl + kHalfWidth, static_cast<int8_t>(ctrl_t::kEmpty),
-              kHalfWidth);
-  // Clean last mirrored bytes that are not initialized
-  // and will not be overwritten by mirroring.
+  // (old_capacity = 7, new_capacity = 15)
+  // new_ctrl  = 456E0123?????????????????...??
+  // *new_ctrl = 456E0123EEEEEEEEEEEEEEEE?...??
+  // position            /      S
+  std::memset(new_ctrl + old_capacity_ + 1, static_cast<int8_t>(ctrl_t::kEmpty),
+              Group::kWidth);
+
+  // Set the last kHalfWidth bytes to empty, to ensure the bytes all the way to
+  // the end are initialized.
   // Examples:
-  // new_ctrl = 1E0EEEEEEEEEEEEE????????
-  // *new_ctrl= 1E0EEEEEEEEEEEEEEEEEEEEE
-  // position           S       /
+  // new_ctrl  = 12E0EEEEEEEEEEEEEEEE?...???????
+  // *new_ctrl = 12E0EEEEEEEEEEEEEEEE???EEEEEEEE
+  // position                   S       /
   //
-  // new_ctrl = 456E0123EEEEEEEE???????????????
-  // *new_ctrl= 456E0123EEEEEEEE???????EEEEEEEE
-  // position                  S       /
-  std::memset(new_ctrl + new_capacity + kHalfWidth,
+  // new_ctrl  = 456E0123EEEEEEEEEEEEEEEE???????
+  // *new_ctrl = 456E0123EEEEEEEEEEEEEEEEEEEEEEE
+  // position                   S       /
+  std::memset(new_ctrl + NumControlBytes(new_capacity) - kHalfWidth,
               static_cast<int8_t>(ctrl_t::kEmpty), kHalfWidth);
 
-  // Create mirrored bytes. old_capacity_ < kHalfWidth
-  // Example:
-  // new_ctrl = 456E0123EEEEEEEE???????EEEEEEEE
-  // *new_ctrl= 456E0123EEEEEEEE456E0123EEEEEEE
-  // position                  S/
-  ctrl_t g[kHalfWidth];
-  std::memcpy(g, new_ctrl, kHalfWidth);
-  std::memcpy(new_ctrl + new_capacity + 1, g, kHalfWidth);
+  // Copy the first bytes to the end (starting at new_capacity +1) to set the
+  // cloned bytes. Note that we use the already copied bytes from old_ctrl here
+  // rather than copying from new_ctrl to avoid a Read-after-Write hazard, since
+  // new_ctrl was just written to. The first old_capacity-1 bytes are set
+  // correctly. Then there may be up to old_capacity bytes that need to be
+  // overwritten, and any remaining bytes will be correctly set to empty. This
+  // sets [new_capacity + 1, new_capacity +1 + old_capacity] correctly.
+  // Examples:
+  // new_ctrl  = 12E0EEEEEEEEEEEEEEEE?...???????
+  // *new_ctrl = 12E0EEEEEEEEEEEE12E012EEEEEEEEE
+  // position                   S/
+  //
+  // new_ctrl  = 456E0123EEEEEEEE?...???EEEEEEEE
+  // *new_ctrl = 456E0123EEEEEEEE456E0123EEEEEEE
+  // position                   S/
+  absl::little_endian::Store64(new_ctrl + new_capacity + 1, copied_bytes);
+
+  // Set The remaining bytes at the end past the cloned bytes to empty. The
+  // incorrectly set bytes are [new_capacity + old_capacity + 2,
+  // min(new_capacity + 1 + kHalfWidth, new_capacity + old_capacity + 2 +
+  // half_old_capacity)]. Taking the difference, we need to set min(kHalfWidth -
+  // (old_capacity + 1), half_old_capacity)]. Since old_capacity < kHalfWidth,
+  // half_old_capacity < kQuarterWidth, so we set kQuarterWidth beginning at
+  // new_capacity + old_capacity + 2 to kEmpty.
+  // Examples:
+  // new_ctrl  = 12E0EEEEEEEEEEEE12E012EEEEEEEEE
+  // *new_ctrl = 12E0EEEEEEEEEEEE12E0EEEEEEEEEEE
+  // position                   S    /
+  //
+  // new_ctrl  = 456E0123EEEEEEEE456E0123EEEEEEE
+  // *new_ctrl = 456E0123EEEEEEEE456E0123EEEEEEE (no change)
+  // position                   S        /
+  std::memset(new_ctrl + new_capacity + old_capacity_ + 2,
+              static_cast<int8_t>(ctrl_t::kEmpty), kQuarterWidth);
+
+  // Finally, we set the new sentinel byte.
+  new_ctrl[new_capacity] = ctrl_t::kSentinel;
+}
 
-  // Finally set sentinel to its place.
+void HashSetResizeHelper::InitControlBytesAfterSoo(ctrl_t* new_ctrl, ctrl_t h2,
+                                                   size_t new_capacity) {
+  assert(is_single_group(new_capacity));
+  std::memset(new_ctrl, static_cast<int8_t>(ctrl_t::kEmpty),
+              NumControlBytes(new_capacity));
+  assert(HashSetResizeHelper::SooSlotIndex() == 1);
+  // This allows us to avoid branching on had_soo_slot_.
+  assert(had_soo_slot_ || h2 == ctrl_t::kEmpty);
+  new_ctrl[1] = new_ctrl[new_capacity + 2] = h2;
   new_ctrl[new_capacity] = ctrl_t::kSentinel;
 }
 
 void HashSetResizeHelper::GrowIntoSingleGroupShuffleTransferableSlots(
-    void* old_slots, void* new_slots, size_t slot_size) const {
+    void* new_slots, size_t slot_size) const {
   assert(old_capacity_ > 0);
   const size_t half_old_capacity = old_capacity_ / 2;
 
-  SanitizerUnpoisonMemoryRegion(old_slots, slot_size * old_capacity_);
+  SanitizerUnpoisonMemoryRegion(old_slots(), slot_size * old_capacity_);
   std::memcpy(new_slots,
-              SlotAddress(old_slots, half_old_capacity + 1, slot_size),
+              SlotAddress(old_slots(), half_old_capacity + 1, slot_size),
               slot_size * half_old_capacity);
   std::memcpy(SlotAddress(new_slots, half_old_capacity + 1, slot_size),
-              old_slots, slot_size * (half_old_capacity + 1));
+              old_slots(), slot_size * (half_old_capacity + 1));
 }
 
 void HashSetResizeHelper::GrowSizeIntoSingleGroupTransferable(
-    CommonFields& c, void* old_slots, size_t slot_size) {
+    CommonFields& c, size_t slot_size) {
   assert(old_capacity_ < Group::kWidth / 2);
   assert(is_single_group(c.capacity()));
   assert(IsGrowingIntoSingleGroupApplicable(old_capacity_, c.capacity()));
 
   GrowIntoSingleGroupShuffleControlBytes(c.control(), c.capacity());
-  GrowIntoSingleGroupShuffleTransferableSlots(old_slots, c.slot_array(),
-                                              slot_size);
+  GrowIntoSingleGroupShuffleTransferableSlots(c.slot_array(), slot_size);
 
   // We poison since GrowIntoSingleGroupShuffleTransferableSlots
   // may leave empty slots unpoisoned.
   PoisonSingleGroupEmptySlots(c, slot_size);
 }
 
+void HashSetResizeHelper::TransferSlotAfterSoo(CommonFields& c,
+                                               size_t slot_size) {
+  assert(was_soo_);
+  assert(had_soo_slot_);
+  assert(is_single_group(c.capacity()));
+  std::memcpy(SlotAddress(c.slot_array(), SooSlotIndex(), slot_size),
+              old_soo_data(), slot_size);
+  PoisonSingleGroupEmptySlots(c, slot_size);
+}
+
+namespace {
+
+// Called whenever the table needs to vacate empty slots either by removing
+// tombstones via rehash or growth.
+ABSL_ATTRIBUTE_NOINLINE
+FindInfo FindInsertPositionWithGrowthOrRehash(CommonFields& common, size_t hash,
+                                              const PolicyFunctions& policy) {
+  const size_t cap = common.capacity();
+  if (cap > Group::kWidth &&
+      // Do these calculations in 64-bit to avoid overflow.
+      common.size() * uint64_t{32} <= cap * uint64_t{25}) {
+    // Squash DELETED without growing if there is enough capacity.
+    //
+    // Rehash in place if the current size is <= 25/32 of capacity.
+    // Rationale for such a high factor: 1) DropDeletesWithoutResize() is
+    // faster than resize, and 2) it takes quite a bit of work to add
+    // tombstones.  In the worst case, seems to take approximately 4
+    // insert/erase pairs to create a single tombstone and so if we are
+    // rehashing because of tombstones, we can afford to rehash-in-place as
+    // long as we are reclaiming at least 1/8 the capacity without doing more
+    // than 2X the work.  (Where "work" is defined to be size() for rehashing
+    // or rehashing in place, and 1 for an insert or erase.)  But rehashing in
+    // place is faster per operation than inserting or even doubling the size
+    // of the table, so we actually afford to reclaim even less space from a
+    // resize-in-place.  The decision is to rehash in place if we can reclaim
+    // at about 1/8th of the usable capacity (specifically 3/28 of the
+    // capacity) which means that the total cost of rehashing will be a small
+    // fraction of the total work.
+    //
+    // Here is output of an experiment using the BM_CacheInSteadyState
+    // benchmark running the old case (where we rehash-in-place only if we can
+    // reclaim at least 7/16*capacity) vs. this code (which rehashes in place
+    // if we can recover 3/32*capacity).
+    //
+    // Note that although in the worst-case number of rehashes jumped up from
+    // 15 to 190, but the number of operations per second is almost the same.
+    //
+    // Abridged output of running BM_CacheInSteadyState benchmark from
+    // raw_hash_set_benchmark.   N is the number of insert/erase operations.
+    //
+    //      | OLD (recover >= 7/16        | NEW (recover >= 3/32)
+    // size |    N/s LoadFactor NRehashes |    N/s LoadFactor NRehashes
+    //  448 | 145284       0.44        18 | 140118       0.44        19
+    //  493 | 152546       0.24        11 | 151417       0.48        28
+    //  538 | 151439       0.26        11 | 151152       0.53        38
+    //  583 | 151765       0.28        11 | 150572       0.57        50
+    //  628 | 150241       0.31        11 | 150853       0.61        66
+    //  672 | 149602       0.33        12 | 150110       0.66        90
+    //  717 | 149998       0.35        12 | 149531       0.70       129
+    //  762 | 149836       0.37        13 | 148559       0.74       190
+    //  807 | 149736       0.39        14 | 151107       0.39        14
+    //  852 | 150204       0.42        15 | 151019       0.42        15
+    DropDeletesWithoutResize(common, policy);
+  } else {
+    // Otherwise grow the container.
+    policy.resize(common, NextCapacity(cap), HashtablezInfoHandle{});
+  }
+  // This function is typically called with tables containing deleted slots.
+  // The table will be big and `FindFirstNonFullAfterResize` will always
+  // fallback to `find_first_non_full`. So using `find_first_non_full` directly.
+  return find_first_non_full(common, hash);
+}
+
+}  // namespace
+
+const void* GetHashRefForEmptyHasher(const CommonFields& common) {
+  // Empty base optimization typically make the empty base class address to be
+  // the same as the first address of the derived class object.
+  // But we generally assume that for empty hasher we can return any valid
+  // pointer.
+  return &common;
+}
+
+size_t PrepareInsertNonSoo(CommonFields& common, size_t hash, FindInfo target,
+                           const PolicyFunctions& policy) {
+  // When there are no deleted slots in the table
+  // and growth_left is positive, we can insert at the first
+  // empty slot in the probe sequence (target).
+  const bool use_target_hint =
+      // Optimization is disabled when generations are enabled.
+      // We have to rehash even sparse tables randomly in such mode.
+      !SwisstableGenerationsEnabled() &&
+      common.growth_info().HasNoDeletedAndGrowthLeft();
+  if (ABSL_PREDICT_FALSE(!use_target_hint)) {
+    // Notes about optimized mode when generations are disabled:
+    // We do not enter this branch if table has no deleted slots
+    // and growth_left is positive.
+    // We enter this branch in the following cases listed in decreasing
+    // frequency:
+    // 1. Table without deleted slots (>95% cases) that needs to be resized.
+    // 2. Table with deleted slots that has space for the inserting element.
+    // 3. Table with deleted slots that needs to be rehashed or resized.
+    if (ABSL_PREDICT_TRUE(common.growth_info().HasNoGrowthLeftAndNoDeleted())) {
+      const size_t old_capacity = common.capacity();
+      policy.resize(common, NextCapacity(old_capacity), HashtablezInfoHandle{});
+      target = HashSetResizeHelper::FindFirstNonFullAfterResize(
+          common, old_capacity, hash);
+    } else {
+      // Note: the table may have no deleted slots here when generations
+      // are enabled.
+      const bool rehash_for_bug_detection =
+          common.should_rehash_for_bug_detection_on_insert();
+      if (rehash_for_bug_detection) {
+        // Move to a different heap allocation in order to detect bugs.
+        const size_t cap = common.capacity();
+        policy.resize(common,
+                      common.growth_left() > 0 ? cap : NextCapacity(cap),
+                      HashtablezInfoHandle{});
+      }
+      if (ABSL_PREDICT_TRUE(common.growth_left() > 0)) {
+        target = find_first_non_full(common, hash);
+      } else {
+        target = FindInsertPositionWithGrowthOrRehash(common, hash, policy);
+      }
+    }
+  }
+  PrepareInsertCommon(common);
+  common.growth_info().OverwriteControlAsFull(common.control()[target.offset]);
+  SetCtrl(common, target.offset, H2(hash), policy.slot_size);
+  common.infoz().RecordInsert(hash, target.probe_length);
+  return target.offset;
+}
+
 }  // namespace container_internal
 ABSL_NAMESPACE_END
 }  // namespace absl