Export of internal Abseil changes.

--
7a6ff16a85beb730c172d5d25cf1b5e1be885c56 by Laramie Leavitt <lar@google.com>:

Internal change.

PiperOrigin-RevId: 254454546

--
ff8f9bafaefc26d451f576ea4a06d150aed63f6f by Andy Soffer <asoffer@google.com>:

Internal changes

PiperOrigin-RevId: 254451562

--
deefc5b651b479ce36f0b4ef203e119c0c8936f2 by CJ Johnson <johnsoncj@google.com>:

Account for subtracting unsigned values from the size of InlinedVector

PiperOrigin-RevId: 254450625

--
3c677316a27bcadc17e41957c809ca472d5fef14 by Andy Soffer <asoffer@google.com>:

Add C++17's std::make_from_tuple to absl/utility/utility.h

PiperOrigin-RevId: 254411573

--
4ee3536a918830eeec402a28fc31a62c7c90b940 by CJ Johnson <johnsoncj@google.com>:

Adds benchmark for the rest of the InlinedVector public API

PiperOrigin-RevId: 254408378

--
e5a21a00700ee83498ff1efbf649169756463ee4 by CJ Johnson <johnsoncj@google.com>:

Updates the definition of InlinedVector::shrink_to_fit() to be exception safe and adds exception safety tests for it.

PiperOrigin-RevId: 254401387

--
2ea82e72b86d82d78b4e4712a63a55981b53c64b by Laramie Leavitt <lar@google.com>:

Use absl::InsecureBitGen in place of std::mt19937
in tests absl/random/...distribution_test.cc

PiperOrigin-RevId: 254289444

--
fa099e02c413a7ffda732415e8105cad26a90337 by Andy Soffer <asoffer@google.com>:

Internal changes

PiperOrigin-RevId: 254286334

--
ce34b7f36933b30cfa35b9c9a5697a792b5666e4 by Andy Soffer <asoffer@google.com>:

Internal changes

PiperOrigin-RevId: 254273059

--
6f9c473da7c2090c2e85a37c5f00622e8a912a89 by Jorg Brown <jorg@google.com>:

Change absl::container_internal::CompressedTuple to instantiate its
internal Storage class with the name of the type it's holding, rather
than the name of the Tuple.  This is not an externally-visible change,
other than less compiler memory is used and less debug information is
generated.

PiperOrigin-RevId: 254269285

--
8bd3c186bf2fc0c55d8a2dd6f28a5327502c9fba by Andy Soffer <asoffer@google.com>:

Adding short-hand IntervalClosed for IntervalClosedClosed and IntervalOpen for
IntervalOpenOpen.

PiperOrigin-RevId: 254252419

--
ea957f99b6a04fccd42aa05605605f3b44b1ecfd by Abseil Team <absl-team@google.com>:

Do not directly use __SIZEOF_INT128__.

In order to avoid linker errors when building with clang-cl (__fixunsdfti, __udivti3 and __fixunssfti are undefined), this CL uses ABSL_HAVE_INTRINSIC_INT128 which is not defined for clang-cl.

PiperOrigin-RevId: 254250739

--
89ab385cd26b34d64130bce856253aaba96d2345 by Andy Soffer <asoffer@google.com>:

Internal changes

PiperOrigin-RevId: 254242321

--
cffc793d93eca6d6bdf7de733847b6ab4a255ae9 by CJ Johnson <johnsoncj@google.com>:

Adds benchmark for InlinedVector::reserve(size_type)

PiperOrigin-RevId: 254199226

--
c90c7a9fa3c8f0c9d5114036979548b055ea2f2a by Gennadiy Rozental <rogeeff@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 254072387

--
c4c388beae016c9570ab54ffa1d52660e4a85b7b by Laramie Leavitt <lar@google.com>:

Internal cleanup.

PiperOrigin-RevId: 254062381

--
d3c992e221cc74e5372d0c8fa410170b6a43c062 by Tom Manshreck <shreck@google.com>:

Update distributions.h to Abseil standards

PiperOrigin-RevId: 254054946

--
d15ad0035c34ef11b14fadc5a4a2d3ec415f5518 by CJ Johnson <johnsoncj@google.com>:

Removes functions with only one caller from the implementation details of InlinedVector by manually inlining the definitions

PiperOrigin-RevId: 254005427

--
2f37e807efc3a8ef1f4b539bdd379917d4151520 by Andy Soffer <asoffer@google.com>:

Initial release of Abseil Random

PiperOrigin-RevId: 253999861

--
24ed1694b6430791d781ed533a8f8ccf6cac5856 by CJ Johnson <johnsoncj@google.com>:

Updates the definition of InlinedVector::assign(...)/InlinedVector::operator=(...) to new, exception-safe implementations with exception safety tests to boot

PiperOrigin-RevId: 253993691

--
5613d95f5a7e34a535cfaeadce801441e990843e by CJ Johnson <johnsoncj@google.com>:

Adds benchmarks for InlinedVector::shrink_to_fit()

PiperOrigin-RevId: 253989647

--
2a96ddfdac40bbb8cb6a7f1aeab90917067c6e63 by Abseil Team <absl-team@google.com>:

Initial release of Abseil Random

PiperOrigin-RevId: 253927497

--
bf1aff8fc9ffa921ad74643e9525ecf25b0d8dc1 by Andy Soffer <asoffer@google.com>:

Initial release of Abseil Random

PiperOrigin-RevId: 253920512

--
bfc03f4a3dcda3cf3a4b84bdb84cda24e3394f41 by Laramie Leavitt <lar@google.com>:

Internal change.

PiperOrigin-RevId: 253886486

--
05036cfcc078ca7c5f581a00dfb0daed568cbb69 by Eric Fiselier <ericwf@google.com>:

Don't include `winsock2.h` because it drags in `windows.h` and friends,
and they define awful macros like OPAQUE, ERROR, and more. This has the
potential to break abseil users.

Instead we only forward declare `timeval` and require Windows users
include `winsock2.h` themselves. This is both inconsistent and poor QoI, but so
including 'windows.h' is bad too.

PiperOrigin-RevId: 253852615
GitOrigin-RevId: 7a6ff16a85beb730c172d5d25cf1b5e1be885c56
Change-Id: Icd6aff87da26f29ec8915da856f051129987cef6

9 files changed, 711 insertions, 299 deletions

diff --git a/absl/container/BUILD.bazel b/absl/container/BUILD.bazel
index 998294c07cab..17d725c18ba9 100644
--- a/absl/container/BUILD.bazel
+++ b/absl/container/BUILD.bazel
@@ -127,6 +127,7 @@ cc_library(
         "//absl/base:core_headers",
         "//absl/memory",
         "//absl/meta:type_traits",
+        "//absl/types:span",
     ],
 )
 
diff --git a/absl/container/CMakeLists.txt b/absl/container/CMakeLists.txt
index 5196e50346a8..6df331e17165 100644
--- a/absl/container/CMakeLists.txt
+++ b/absl/container/CMakeLists.txt
@@ -126,6 +126,7 @@ absl_cc_library(
     absl::compressed_tuple
     absl::core_headers
     absl::memory
+    absl::span
     absl::type_traits
   PUBLIC
 )
diff --git a/absl/container/inlined_vector.h b/absl/container/inlined_vector.h
index 2c96cc37b47a..10881b22a918 100644
--- a/absl/container/inlined_vector.h
+++ b/absl/container/inlined_vector.h
@@ -166,7 +166,7 @@ class InlinedVector {
   InlinedVector(const InlinedVector& other, const allocator_type& alloc)
       : storage_(alloc) {
     if (IsMemcpyOk::value && !other.storage_.GetIsAllocated()) {
-      storage_.MemcpyContents(other.storage_);
+      storage_.MemcpyFrom(other.storage_);
     } else {
       storage_.Initialize(IteratorValueAdapter<const_pointer>(other.data()),
                           other.size());
@@ -193,7 +193,7 @@ class InlinedVector {
       std::is_nothrow_move_constructible<value_type>::value)
       : storage_(*other.storage_.GetAllocPtr()) {
     if (IsMemcpyOk::value) {
-      storage_.MemcpyContents(other.storage_);
+      storage_.MemcpyFrom(other.storage_);
       other.storage_.SetInlinedSize(0);
     } else if (other.storage_.GetIsAllocated()) {
       storage_.SetAllocatedData(other.storage_.GetAllocatedData(),
@@ -227,7 +227,7 @@ class InlinedVector {
       absl::allocator_is_nothrow<allocator_type>::value)
       : storage_(alloc) {
     if (IsMemcpyOk::value) {
-      storage_.MemcpyContents(other.storage_);
+      storage_.MemcpyFrom(other.storage_);
       other.storage_.SetInlinedSize(0);
     } else if ((*storage_.GetAllocPtr() == *other.storage_.GetAllocPtr()) &&
                other.storage_.GetIsAllocated()) {
@@ -464,26 +464,22 @@ class InlinedVector {
   InlinedVector& operator=(InlinedVector&& other) {
     if (ABSL_PREDICT_FALSE(this == std::addressof(other))) return *this;
 
-    if (other.storage_.GetIsAllocated()) {
-      clear();
-      storage_.SetAllocatedSize(other.size());
-      storage_.SetAllocatedData(other.storage_.GetAllocatedData(),
-                                other.storage_.GetAllocatedCapacity());
+    if (IsMemcpyOk::value || other.storage_.GetIsAllocated()) {
+      inlined_vector_internal::DestroyElements(storage_.GetAllocPtr(), data(),
+                                               size());
+      if (storage_.GetIsAllocated()) {
+        AllocatorTraits::deallocate(*storage_.GetAllocPtr(),
+                                    storage_.GetAllocatedData(),
+                                    storage_.GetAllocatedCapacity());
+      }
+      storage_.MemcpyFrom(other.storage_);
       other.storage_.SetInlinedSize(0);
     } else {
-      if (storage_.GetIsAllocated()) clear();
-      // Both are inlined now.
-      if (size() < other.size()) {
-        auto mid = std::make_move_iterator(other.begin() + size());
-        std::copy(std::make_move_iterator(other.begin()), mid, begin());
-        UninitializedCopy(mid, std::make_move_iterator(other.end()), end());
-      } else {
-        auto new_end = std::copy(std::make_move_iterator(other.begin()),
-                                 std::make_move_iterator(other.end()), begin());
-        Destroy(new_end, end());
-      }
-      storage_.SetInlinedSize(other.size());
+      storage_.Assign(IteratorValueAdapter<MoveIterator>(
+                          MoveIterator(other.storage_.GetInlinedData())),
+                      other.size());
     }
+
     return *this;
   }
 
@@ -491,23 +487,7 @@ class InlinedVector {
   //
   // Replaces the contents of the inlined vector with `n` copies of `v`.
   void assign(size_type n, const_reference v) {
-    if (n <= size()) {  // Possibly shrink
-      std::fill_n(begin(), n, v);
-      erase(begin() + n, end());
-      return;
-    }
-    // Grow
-    reserve(n);
-    std::fill_n(begin(), size(), v);
-    if (storage_.GetIsAllocated()) {
-      UninitializedFill(storage_.GetAllocatedData() + size(),
-                        storage_.GetAllocatedData() + n, v);
-      storage_.SetAllocatedSize(n);
-    } else {
-      UninitializedFill(storage_.GetInlinedData() + size(),
-                        storage_.GetInlinedData() + n, v);
-      storage_.SetInlinedSize(n);
-    }
+    storage_.Assign(CopyValueAdapter(v), n);
   }
 
   // Overload of `InlinedVector::assign()` to replace the contents of the
@@ -522,24 +502,8 @@ class InlinedVector {
   template <typename ForwardIterator,
             EnableIfAtLeastForwardIterator<ForwardIterator>* = nullptr>
   void assign(ForwardIterator first, ForwardIterator last) {
-    auto length = std::distance(first, last);
-
-    // Prefer reassignment to copy construction for elements.
-    if (static_cast<size_type>(length) <= size()) {
-      erase(std::copy(first, last, begin()), end());
-      return;
-    }
-
-    reserve(length);
-    iterator out = begin();
-    for (; out != end(); ++first, ++out) *out = *first;
-    if (storage_.GetIsAllocated()) {
-      UninitializedCopy(first, last, out);
-      storage_.SetAllocatedSize(length);
-    } else {
-      UninitializedCopy(first, last, out);
-      storage_.SetInlinedSize(length);
-    }
+    storage_.Assign(IteratorValueAdapter<ForwardIterator>(first),
+                    std::distance(first, last));
   }
 
   // Overload of `InlinedVector::assign()` to replace the contents of the
@@ -624,7 +588,15 @@ class InlinedVector {
   // of `v` starting at `pos`. Returns an `iterator` pointing to the first of
   // the newly inserted elements.
   iterator insert(const_iterator pos, size_type n, const_reference v) {
-    return InsertWithCount(pos, n, v);
+    assert(pos >= begin() && pos <= end());
+    if (ABSL_PREDICT_FALSE(n == 0)) {
+      return const_cast<iterator>(pos);
+    }
+    value_type copy = v;
+    std::pair<iterator, iterator> it_pair = ShiftRight(pos, n);
+    std::fill(it_pair.first, it_pair.second, copy);
+    UninitializedFill(it_pair.second, it_pair.first + n, copy);
+    return it_pair.first;
   }
 
   // Overload of `InlinedVector::insert()` for copying the contents of the
@@ -644,7 +616,17 @@ class InlinedVector {
             EnableIfAtLeastForwardIterator<ForwardIterator>* = nullptr>
   iterator insert(const_iterator pos, ForwardIterator first,
                   ForwardIterator last) {
-    return InsertWithForwardRange(pos, first, last);
+    assert(pos >= begin() && pos <= end());
+    if (ABSL_PREDICT_FALSE(first == last)) {
+      return const_cast<iterator>(pos);
+    }
+    auto n = std::distance(first, last);
+    std::pair<iterator, iterator> it_pair = ShiftRight(pos, n);
+    size_type used_spots = it_pair.second - it_pair.first;
+    auto open_spot = std::next(first, used_spots);
+    std::copy(first, open_spot, it_pair.first);
+    UninitializedCopy(open_spot, last, it_pair.second);
+    return it_pair.first;
   }
 
   // Overload of `InlinedVector::insert()` for inserting elements constructed
@@ -696,17 +678,26 @@ class InlinedVector {
   reference emplace_back(Args&&... args) {
     size_type s = size();
     if (ABSL_PREDICT_FALSE(s == capacity())) {
-      return GrowAndEmplaceBack(std::forward<Args>(args)...);
-    }
-    pointer space;
-    if (storage_.GetIsAllocated()) {
-      storage_.SetAllocatedSize(s + 1);
-      space = storage_.GetAllocatedData();
+      size_type new_capacity = 2 * capacity();
+      pointer new_data =
+          AllocatorTraits::allocate(*storage_.GetAllocPtr(), new_capacity);
+      reference new_element =
+          Construct(new_data + s, std::forward<Args>(args)...);
+      UninitializedCopy(std::make_move_iterator(data()),
+                        std::make_move_iterator(data() + s), new_data);
+      ResetAllocation(new_data, new_capacity, s + 1);
+      return new_element;
     } else {
-      storage_.SetInlinedSize(s + 1);
-      space = storage_.GetInlinedData();
+      pointer space;
+      if (storage_.GetIsAllocated()) {
+        storage_.SetAllocatedSize(s + 1);
+        space = storage_.GetAllocatedData();
+      } else {
+        storage_.SetInlinedSize(s + 1);
+        space = storage_.GetInlinedData();
+      }
+      return Construct(space + s, std::forward<Args>(args)...);
     }
-    return Construct(space + s, std::forward<Args>(args)...);
   }
 
   // `InlinedVector::push_back()`
@@ -727,7 +718,7 @@ class InlinedVector {
   void pop_back() noexcept {
     assert(!empty());
     AllocatorTraits::destroy(*storage_.GetAllocPtr(), data() + (size() - 1));
-    storage_.AddSize(-1);
+    storage_.SubtractSize(1);
   }
 
   // `InlinedVector::erase()`
@@ -794,10 +785,20 @@ class InlinedVector {
   // effects. Otherwise, `reserve()` will reallocate, performing an n-time
   // element-wise move of everything contained.
   void reserve(size_type n) {
-    if (n > capacity()) {
-      // Make room for new elements
-      EnlargeBy(n - size());
+    if (n <= capacity()) {
+      return;
+    }
+    const size_type s = size();
+    size_type target = (std::max)(static_cast<size_type>(N), n);
+    size_type new_capacity = capacity();
+    while (new_capacity < target) {
+      new_capacity <<= 1;
     }
+    pointer new_data =
+        AllocatorTraits::allocate(*storage_.GetAllocPtr(), new_capacity);
+    UninitializedCopy(std::make_move_iterator(data()),
+                      std::make_move_iterator(data() + s), new_data);
+    ResetAllocation(new_data, new_capacity, s);
   }
 
   // `InlinedVector::shrink_to_fit()`
@@ -812,37 +813,105 @@ class InlinedVector {
   // If `size() > N` and `size() < capacity()` the elements will be moved to a
   // smaller heap allocation.
   void shrink_to_fit() {
-    const auto s = size();
-    if (ABSL_PREDICT_FALSE(!storage_.GetIsAllocated() || s == capacity()))
-      return;
-
-    if (s <= N) {
-      // Move the elements to the inlined storage.
-      // We have to do this using a temporary, because `inlined_storage` and
-      // `allocation_storage` are in a union field.
-      auto temp = std::move(*this);
-      assign(std::make_move_iterator(temp.begin()),
-             std::make_move_iterator(temp.end()));
-      return;
+    if (storage_.GetIsAllocated()) {
+      storage_.ShrinkToFit();
     }
-
-    // Reallocate storage and move elements.
-    // We can't simply use the same approach as above, because `assign()` would
-    // call into `reserve()` internally and reserve larger capacity than we need
-    pointer new_data = AllocatorTraits::allocate(*storage_.GetAllocPtr(), s);
-    UninitializedCopy(std::make_move_iterator(storage_.GetAllocatedData()),
-                      std::make_move_iterator(storage_.GetAllocatedData() + s),
-                      new_data);
-    ResetAllocation(new_data, s, s);
   }
 
   // `InlinedVector::swap()`
   //
   // Swaps the contents of this inlined vector with the contents of `other`.
   void swap(InlinedVector& other) {
-    if (ABSL_PREDICT_FALSE(this == std::addressof(other))) return;
+    using std::swap;
+
+    if (ABSL_PREDICT_FALSE(this == std::addressof(other))) {
+      return;
+    }
+
+    bool is_allocated = storage_.GetIsAllocated();
+    bool other_is_allocated = other.storage_.GetIsAllocated();
+
+    if (is_allocated && other_is_allocated) {
+      // Both out of line, so just swap the tag, allocation, and allocator.
+      storage_.SwapSizeAndIsAllocated(std::addressof(other.storage_));
+      storage_.SwapAllocatedSizeAndCapacity(std::addressof(other.storage_));
+      swap(*storage_.GetAllocPtr(), *other.storage_.GetAllocPtr());
+
+      return;
+    }
+
+    if (!is_allocated && !other_is_allocated) {
+      // Both inlined: swap up to smaller size, then move remaining elements.
+      InlinedVector* a = this;
+      InlinedVector* b = std::addressof(other);
+      if (size() < other.size()) {
+        swap(a, b);
+      }
+
+      const size_type a_size = a->size();
+      const size_type b_size = b->size();
+      assert(a_size >= b_size);
+      // `a` is larger. Swap the elements up to the smaller array size.
+      std::swap_ranges(a->storage_.GetInlinedData(),
+                       a->storage_.GetInlinedData() + b_size,
+                       b->storage_.GetInlinedData());
+
+      // Move the remaining elements:
+      //   [`b_size`, `a_size`) from `a` -> [`b_size`, `a_size`) from `b`
+      b->UninitializedCopy(a->storage_.GetInlinedData() + b_size,
+                           a->storage_.GetInlinedData() + a_size,
+                           b->storage_.GetInlinedData() + b_size);
+      a->Destroy(a->storage_.GetInlinedData() + b_size,
+                 a->storage_.GetInlinedData() + a_size);
+
+      storage_.SwapSizeAndIsAllocated(std::addressof(other.storage_));
+      swap(*storage_.GetAllocPtr(), *other.storage_.GetAllocPtr());
+
+      assert(b->size() == a_size);
+      assert(a->size() == b_size);
+      return;
+    }
+
+    // One is out of line, one is inline.
+    // We first move the elements from the inlined vector into the
+    // inlined space in the other vector.  We then put the other vector's
+    // pointer/capacity into the originally inlined vector and swap
+    // the tags.
+    InlinedVector* a = this;
+    InlinedVector* b = std::addressof(other);
+    if (a->storage_.GetIsAllocated()) {
+      swap(a, b);
+    }
+
+    assert(!a->storage_.GetIsAllocated());
+    assert(b->storage_.GetIsAllocated());
+
+    const size_type a_size = a->size();
+    const size_type b_size = b->size();
+    // In an optimized build, `b_size` would be unused.
+    static_cast<void>(b_size);
+
+    // Made Local copies of `size()`, these can now be swapped
+    a->storage_.SwapSizeAndIsAllocated(std::addressof(b->storage_));
+
+    // Copy out before `b`'s union gets clobbered by `inline_space`
+    pointer b_data = b->storage_.GetAllocatedData();
+    size_type b_capacity = b->storage_.GetAllocatedCapacity();
+
+    b->UninitializedCopy(a->storage_.GetInlinedData(),
+                         a->storage_.GetInlinedData() + a_size,
+                         b->storage_.GetInlinedData());
+    a->Destroy(a->storage_.GetInlinedData(),
+               a->storage_.GetInlinedData() + a_size);
+
+    a->storage_.SetAllocatedData(b_data, b_capacity);
 
-    SwapImpl(other);
+    if (*a->storage_.GetAllocPtr() != *b->storage_.GetAllocPtr()) {
+      swap(*a->storage_.GetAllocPtr(), *b->storage_.GetAllocPtr());
+    }
+
+    assert(b->size() == a_size);
+    assert(a->size() == b_size);
   }
 
  private:
@@ -900,31 +969,6 @@ class InlinedVector {
 #endif  // !defined(NDEBUG)
   }
 
-  // Enlarge the underlying representation so we can store `size_ + delta` elems
-  // in allocated space. The size is not changed, and any newly added memory is
-  // not initialized.
-  void EnlargeBy(size_type delta) {
-    const size_type s = size();
-    assert(s <= capacity());
-
-    size_type target = (std::max)(static_cast<size_type>(N), s + delta);
-
-    // Compute new capacity by repeatedly doubling current capacity
-    // TODO(psrc): Check and avoid overflow?
-    size_type new_capacity = capacity();
-    while (new_capacity < target) {
-      new_capacity <<= 1;
-    }
-
-    pointer new_data =
-        AllocatorTraits::allocate(*storage_.GetAllocPtr(), new_capacity);
-
-    UninitializedCopy(std::make_move_iterator(data()),
-                      std::make_move_iterator(data() + s), new_data);
-
-    ResetAllocation(new_data, new_capacity, s);
-  }
-
   // Shift all elements from `position` to `end()` by `n` places to the right.
   // If the vector needs to be enlarged, memory will be allocated.
   // Returns `iterator`s pointing to the start of the previously-initialized
@@ -991,147 +1035,6 @@ class InlinedVector {
     return std::make_pair(start_used, start_raw);
   }
 
-  template <typename... Args>
-  reference GrowAndEmplaceBack(Args&&... args) {
-    assert(size() == capacity());
-    const size_type s = size();
-
-    size_type new_capacity = 2 * capacity();
-    pointer new_data =
-        AllocatorTraits::allocate(*storage_.GetAllocPtr(), new_capacity);
-
-    reference new_element =
-        Construct(new_data + s, std::forward<Args>(args)...);
-    UninitializedCopy(std::make_move_iterator(data()),
-                      std::make_move_iterator(data() + s), new_data);
-
-    ResetAllocation(new_data, new_capacity, s + 1);
-
-    return new_element;
-  }
-
-  iterator InsertWithCount(const_iterator position, size_type n,
-                           const_reference v) {
-    assert(position >= begin() && position <= end());
-    if (ABSL_PREDICT_FALSE(n == 0)) return const_cast<iterator>(position);
-
-    value_type copy = v;
-    std::pair<iterator, iterator> it_pair = ShiftRight(position, n);
-    std::fill(it_pair.first, it_pair.second, copy);
-    UninitializedFill(it_pair.second, it_pair.first + n, copy);
-
-    return it_pair.first;
-  }
-
-  template <typename ForwardIt>
-  iterator InsertWithForwardRange(const_iterator position, ForwardIt first,
-                                  ForwardIt last) {
-    static_assert(absl::inlined_vector_internal::IsAtLeastForwardIterator<
-                      ForwardIt>::value,
-                  "");
-    assert(position >= begin() && position <= end());
-
-    if (ABSL_PREDICT_FALSE(first == last))
-      return const_cast<iterator>(position);
-
-    auto n = std::distance(first, last);
-    std::pair<iterator, iterator> it_pair = ShiftRight(position, n);
-    size_type used_spots = it_pair.second - it_pair.first;
-    auto open_spot = std::next(first, used_spots);
-    std::copy(first, open_spot, it_pair.first);
-    UninitializedCopy(open_spot, last, it_pair.second);
-    return it_pair.first;
-  }
-
-  void SwapImpl(InlinedVector& other) {
-    using std::swap;
-
-    bool is_allocated = storage_.GetIsAllocated();
-    bool other_is_allocated = other.storage_.GetIsAllocated();
-
-    if (is_allocated && other_is_allocated) {
-      // Both out of line, so just swap the tag, allocation, and allocator.
-      storage_.SwapSizeAndIsAllocated(std::addressof(other.storage_));
-      storage_.SwapAllocatedSizeAndCapacity(std::addressof(other.storage_));
-      swap(*storage_.GetAllocPtr(), *other.storage_.GetAllocPtr());
-
-      return;
-    }
-
-    if (!is_allocated && !other_is_allocated) {
-      // Both inlined: swap up to smaller size, then move remaining elements.
-      InlinedVector* a = this;
-      InlinedVector* b = std::addressof(other);
-      if (size() < other.size()) {
-        swap(a, b);
-      }
-
-      const size_type a_size = a->size();
-      const size_type b_size = b->size();
-      assert(a_size >= b_size);
-      // `a` is larger. Swap the elements up to the smaller array size.
-      std::swap_ranges(a->storage_.GetInlinedData(),
-                       a->storage_.GetInlinedData() + b_size,
-                       b->storage_.GetInlinedData());
-
-      // Move the remaining elements:
-      //   [`b_size`, `a_size`) from `a` -> [`b_size`, `a_size`) from `b`
-      b->UninitializedCopy(a->storage_.GetInlinedData() + b_size,
-                           a->storage_.GetInlinedData() + a_size,
-                           b->storage_.GetInlinedData() + b_size);
-      a->Destroy(a->storage_.GetInlinedData() + b_size,
-                 a->storage_.GetInlinedData() + a_size);
-
-      storage_.SwapSizeAndIsAllocated(std::addressof(other.storage_));
-      swap(*storage_.GetAllocPtr(), *other.storage_.GetAllocPtr());
-
-      assert(b->size() == a_size);
-      assert(a->size() == b_size);
-      return;
-    }
-
-    // One is out of line, one is inline.
-    // We first move the elements from the inlined vector into the
-    // inlined space in the other vector.  We then put the other vector's
-    // pointer/capacity into the originally inlined vector and swap
-    // the tags.
-    InlinedVector* a = this;
-    InlinedVector* b = std::addressof(other);
-    if (a->storage_.GetIsAllocated()) {
-      swap(a, b);
-    }
-
-    assert(!a->storage_.GetIsAllocated());
-    assert(b->storage_.GetIsAllocated());
-
-    const size_type a_size = a->size();
-    const size_type b_size = b->size();
-    // In an optimized build, `b_size` would be unused.
-    static_cast<void>(b_size);
-
-    // Made Local copies of `size()`, these can now be swapped
-    a->storage_.SwapSizeAndIsAllocated(std::addressof(b->storage_));
-
-    // Copy out before `b`'s union gets clobbered by `inline_space`
-    pointer b_data = b->storage_.GetAllocatedData();
-    size_type b_capacity = b->storage_.GetAllocatedCapacity();
-
-    b->UninitializedCopy(a->storage_.GetInlinedData(),
-                         a->storage_.GetInlinedData() + a_size,
-                         b->storage_.GetInlinedData());
-    a->Destroy(a->storage_.GetInlinedData(),
-               a->storage_.GetInlinedData() + a_size);
-
-    a->storage_.SetAllocatedData(b_data, b_capacity);
-
-    if (*a->storage_.GetAllocPtr() != *b->storage_.GetAllocPtr()) {
-      swap(*a->storage_.GetAllocPtr(), *b->storage_.GetAllocPtr());
-    }
-
-    assert(b->size() == a_size);
-    assert(a->size() == b_size);
-  }
-
   Storage storage_;
 };
 
diff --git a/absl/container/inlined_vector_benchmark.cc b/absl/container/inlined_vector_benchmark.cc
index df4d3ce5a2d1..b99bbd62544f 100644
--- a/absl/container/inlined_vector_benchmark.cc
+++ b/absl/container/inlined_vector_benchmark.cc
@@ -599,6 +599,146 @@ void BM_AssignFromMove(benchmark::State& state) {
 ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_AssignFromMove, TrivialType);
 ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_AssignFromMove, NontrivialType);
 
+template <typename T, size_t FromSize, size_t ToSize>
+void BM_ResizeSize(benchmark::State& state) {
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [](InlVec<T>* vec, size_t) { vec->resize(ToSize); });
+}
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_ResizeSize, TrivialType);
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_ResizeSize, NontrivialType);
+
+template <typename T, size_t FromSize, size_t ToSize>
+void BM_ResizeSizeRef(benchmark::State& state) {
+  auto t = T();
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [&](InlVec<T>* vec, size_t) {
+        benchmark::DoNotOptimize(t);
+        vec->resize(ToSize, t);
+      });
+}
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_ResizeSizeRef, TrivialType);
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_ResizeSizeRef, NontrivialType);
+
+template <typename T, size_t FromSize, size_t ToSize>
+void BM_InsertSizeRef(benchmark::State& state) {
+  auto t = T();
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [&](InlVec<T>* vec, size_t) {
+        benchmark::DoNotOptimize(t);
+        auto* pos = vec->data() + (vec->size() / 2);
+        vec->insert(pos, t);
+      });
+}
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_InsertSizeRef, TrivialType);
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_InsertSizeRef, NontrivialType);
+
+template <typename T, size_t FromSize, size_t ToSize>
+void BM_InsertRange(benchmark::State& state) {
+  InlVec<T> other_vec(ToSize);
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [&](InlVec<T>* vec, size_t) {
+        benchmark::DoNotOptimize(other_vec);
+        auto* pos = vec->data() + (vec->size() / 2);
+        vec->insert(pos, other_vec.begin(), other_vec.end());
+      });
+}
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_InsertRange, TrivialType);
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_InsertRange, NontrivialType);
+
+template <typename T, size_t FromSize>
+void BM_EmplaceBack(benchmark::State& state) {
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [](InlVec<T>* vec, size_t) { vec->emplace_back(); });
+}
+ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_EmplaceBack, TrivialType);
+ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_EmplaceBack, NontrivialType);
+
+template <typename T, size_t FromSize>
+void BM_PopBack(benchmark::State& state) {
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [](InlVec<T>* vec, size_t) { vec->pop_back(); });
+}
+ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_PopBack, TrivialType);
+ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_PopBack, NontrivialType);
+
+template <typename T, size_t FromSize>
+void BM_EraseOne(benchmark::State& state) {
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [](InlVec<T>* vec, size_t) {
+        auto* pos = vec->data() + (vec->size() / 2);
+        vec->erase(pos);
+      });
+}
+ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_EraseOne, TrivialType);
+ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_EraseOne, NontrivialType);
+
+template <typename T, size_t FromSize>
+void BM_EraseRange(benchmark::State& state) {
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [](InlVec<T>* vec, size_t) {
+        auto* pos = vec->data() + (vec->size() / 2);
+        vec->erase(pos, pos + 1);
+      });
+}
+ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_EraseRange, TrivialType);
+ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_EraseRange, NontrivialType);
+
 template <typename T, size_t FromSize>
 void BM_Clear(benchmark::State& state) {
   BatchedBenchmark<T>(
@@ -609,4 +749,56 @@ void BM_Clear(benchmark::State& state) {
 ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_Clear, TrivialType);
 ABSL_INTERNAL_BENCHMARK_ONE_SIZE(BM_Clear, NontrivialType);
 
+template <typename T, size_t FromSize, size_t ToCapacity>
+void BM_Reserve(benchmark::State& state) {
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [](InlVec<T>* vec, size_t) { vec->reserve(ToCapacity); });
+}
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_Reserve, TrivialType);
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_Reserve, NontrivialType);
+
+template <typename T, size_t FromCapacity, size_t ToCapacity>
+void BM_ShrinkToFit(benchmark::State& state) {
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [](InlVec<T>* vec, size_t) {
+        vec->clear();
+        vec->resize(ToCapacity);
+        vec->reserve(FromCapacity);
+      },
+      /* test_vec = */ [](InlVec<T>* vec, size_t) { vec->shrink_to_fit(); });
+}
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_ShrinkToFit, TrivialType);
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_ShrinkToFit, NontrivialType);
+
+template <typename T, size_t FromSize, size_t ToSize>
+void BM_Swap(benchmark::State& state) {
+  using VecT = InlVec<T>;
+  std::array<VecT, kBatchSize> vector_batch{};
+  BatchedBenchmark<T>(
+      state,
+      /* prepare_vec = */
+      [&](InlVec<T>* vec, size_t i) {
+        vector_batch[i].clear();
+        vector_batch[i].resize(ToSize);
+        vec->resize(FromSize);
+      },
+      /* test_vec = */
+      [&](InlVec<T>* vec, size_t i) {
+        using std::swap;
+        benchmark::DoNotOptimize(vector_batch[i]);
+        swap(*vec, vector_batch[i]);
+      });
+}
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_Swap, TrivialType);
+ABSL_INTERNAL_BENCHMARK_TWO_SIZE(BM_Swap, NontrivialType);
+
 }  // namespace
diff --git a/absl/container/inlined_vector_exception_safety_test.cc b/absl/container/inlined_vector_exception_safety_test.cc
index 0a9649250302..e7c47127df9f 100644
--- a/absl/container/inlined_vector_exception_safety_test.cc
+++ b/absl/container/inlined_vector_exception_safety_test.cc
@@ -12,7 +12,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <array>
+#include <initializer_list>
+#include <iterator>
 #include <memory>
+#include <utility>
 
 #include "gtest/gtest.h"
 #include "absl/base/internal/exception_safety_testing.h"
@@ -81,6 +85,24 @@ using OneSizeTestParams =
                      TestParams<ThrowAllocMovableThrowerVec, kLargeSize>,
                      TestParams<ThrowAllocMovableThrowerVec, kSmallSize>>;
 
+using TwoSizeTestParams = ::testing::Types<
+    TestParams<ThrowerVec, kLargeSize, kLargeSize>,
+    TestParams<ThrowerVec, kLargeSize, kSmallSize>,
+    TestParams<ThrowerVec, kSmallSize, kLargeSize>,
+    TestParams<ThrowerVec, kSmallSize, kSmallSize>,
+    TestParams<MovableThrowerVec, kLargeSize, kLargeSize>,
+    TestParams<MovableThrowerVec, kLargeSize, kSmallSize>,
+    TestParams<MovableThrowerVec, kSmallSize, kLargeSize>,
+    TestParams<MovableThrowerVec, kSmallSize, kSmallSize>,
+    TestParams<ThrowAllocThrowerVec, kLargeSize, kLargeSize>,
+    TestParams<ThrowAllocThrowerVec, kLargeSize, kSmallSize>,
+    TestParams<ThrowAllocThrowerVec, kSmallSize, kLargeSize>,
+    TestParams<ThrowAllocThrowerVec, kSmallSize, kSmallSize>,
+    TestParams<ThrowAllocMovableThrowerVec, kLargeSize, kLargeSize>,
+    TestParams<ThrowAllocMovableThrowerVec, kLargeSize, kSmallSize>,
+    TestParams<ThrowAllocMovableThrowerVec, kSmallSize, kLargeSize>,
+    TestParams<ThrowAllocMovableThrowerVec, kSmallSize, kSmallSize>>;
+
 template <typename>
 struct NoSizeTest : ::testing::Test {};
 TYPED_TEST_SUITE(NoSizeTest, NoSizeTestParams);
@@ -89,6 +111,25 @@ template <typename>
 struct OneSizeTest : ::testing::Test {};
 TYPED_TEST_SUITE(OneSizeTest, OneSizeTestParams);
 
+template <typename>
+struct TwoSizeTest : ::testing::Test {};
+TYPED_TEST_SUITE(TwoSizeTest, TwoSizeTestParams);
+
+template <typename VecT>
+bool InlinedVectorInvariants(VecT* vec) {
+  if (*vec != *vec) return false;
+  if (vec->size() > vec->capacity()) return false;
+  if (vec->size() > vec->max_size()) return false;
+  if (vec->capacity() > vec->max_size()) return false;
+  if (vec->data() != std::addressof(vec->at(0))) return false;
+  if (vec->data() != vec->begin()) return false;
+  if (*vec->data() != *vec->begin()) return false;
+  if (vec->begin() > vec->end()) return false;
+  if ((vec->end() - vec->begin()) != vec->size()) return false;
+  if (std::distance(vec->begin(), vec->end()) != vec->size()) return false;
+  return true;
+}
+
 // Function that always returns false is correct, but refactoring is required
 // for clarity. It's needed to express that, as a contract, certain operations
 // should not throw at all. Execution of this function means an exception was
@@ -179,6 +220,45 @@ TYPED_TEST(OneSizeTest, MoveConstructor) {
   }
 }
 
+TYPED_TEST(TwoSizeTest, Assign) {
+  using VecT = typename TypeParam::VecT;
+  using value_type = typename VecT::value_type;
+  constexpr static auto from_size = TypeParam::GetSizeAt(0);
+  constexpr static auto to_size = TypeParam::GetSizeAt(1);
+
+  auto tester = testing::MakeExceptionSafetyTester()
+                    .WithInitialValue(VecT{from_size})
+                    .WithContracts(InlinedVectorInvariants<VecT>);
+
+  EXPECT_TRUE(tester.Test([](VecT* vec) {
+    *vec = ABSL_INTERNAL_MAKE_INIT_LIST(value_type, to_size);
+  }));
+
+  EXPECT_TRUE(tester.Test([](VecT* vec) {
+    VecT other_vec{to_size};
+    *vec = other_vec;
+  }));
+
+  EXPECT_TRUE(tester.Test([](VecT* vec) {
+    VecT other_vec{to_size};
+    *vec = std::move(other_vec);
+  }));
+
+  EXPECT_TRUE(tester.Test([](VecT* vec) {
+    value_type val{};
+    vec->assign(to_size, val);
+  }));
+
+  EXPECT_TRUE(tester.Test([](VecT* vec) {
+    vec->assign(ABSL_INTERNAL_MAKE_INIT_LIST(value_type, to_size));
+  }));
+
+  EXPECT_TRUE(tester.Test([](VecT* vec) {
+    std::array<value_type, to_size> arr{};
+    vec->assign(arr.begin(), arr.end());
+  }));
+}
+
 TYPED_TEST(OneSizeTest, PopBack) {
   using VecT = typename TypeParam::VecT;
   constexpr static auto size = TypeParam::GetSizeAt(0);
@@ -205,4 +285,17 @@ TYPED_TEST(OneSizeTest, Clear) {
   }));
 }
 
+TYPED_TEST(OneSizeTest, ShrinkToFit) {
+  using VecT = typename TypeParam::VecT;
+  constexpr static auto size = TypeParam::GetSizeAt(0);
+
+  auto tester = testing::MakeExceptionSafetyTester()
+                    .WithInitialValue(VecT{size})
+                    .WithContracts(InlinedVectorInvariants<VecT>);
+
+  EXPECT_TRUE(tester.Test([](VecT* vec) {
+    vec->shrink_to_fit();  //
+  }));
+}
+
 }  // namespace
diff --git a/absl/container/inlined_vector_test.cc b/absl/container/inlined_vector_test.cc
index 6037001a0473..60fe89b28aee 100644
--- a/absl/container/inlined_vector_test.cc
+++ b/absl/container/inlined_vector_test.cc
@@ -190,6 +190,12 @@ TEST(IntVec, SimpleOps) {
   }
 }
 
+TEST(IntVec, PopBackNoOverflow) {
+  IntVec v = {1};
+  v.pop_back();
+  EXPECT_EQ(v.size(), 0);
+}
+
 TEST(IntVec, AtThrows) {
   IntVec v = {1, 2, 3};
   EXPECT_EQ(v.at(2), 3);
diff --git a/absl/container/internal/compressed_tuple.h b/absl/container/internal/compressed_tuple.h
index bb3471f5d747..1713ad6862c5 100644
--- a/absl/container/internal/compressed_tuple.h
+++ b/absl/container/internal/compressed_tuple.h
@@ -32,6 +32,7 @@
 #ifndef ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_
 #define ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_
 
+#include <initializer_list>
 #include <tuple>
 #include <type_traits>
 #include <utility>
@@ -75,17 +76,30 @@ constexpr bool IsFinal() {
 #endif
 }
 
+// We can't use EBCO on other CompressedTuples because that would mean that we
+// derive from multiple Storage<> instantiations with the same I parameter,
+// and potentially from multiple identical Storage<> instantiations.  So anytime
+// we use type inheritance rather than encapsulation, we mark
+// CompressedTupleImpl, to make this easy to detect.
+struct uses_inheritance {};
+
 template <typename T>
 constexpr bool ShouldUseBase() {
-  return std::is_class<T>::value && std::is_empty<T>::value && !IsFinal<T>();
+  return std::is_class<T>::value && std::is_empty<T>::value && !IsFinal<T>() &&
+         !std::is_base_of<uses_inheritance, T>::value;
 }
 
 // The storage class provides two specializations:
 //  - For empty classes, it stores T as a base class.
 //  - For everything else, it stores T as a member.
-template <typename D, size_t I, bool = ShouldUseBase<ElemT<D, I>>()>
+template <typename T, size_t I,
+#if defined(_MSC_VER)
+          bool UseBase =
+              ShouldUseBase<typename std::enable_if<true, T>::type>()>
+#else
+          bool UseBase = ShouldUseBase<T>()>
+#endif
 struct Storage {
-  using T = ElemT<D, I>;
   T value;
   constexpr Storage() = default;
   explicit constexpr Storage(T&& v) : value(absl::forward<T>(v)) {}
@@ -95,10 +109,8 @@ struct Storage {
   T&& get() && { return std::move(*this).value; }
 };
 
-template <typename D, size_t I>
-struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC Storage<D, I, true>
-    : ElemT<D, I> {
-  using T = internal_compressed_tuple::ElemT<D, I>;
+template <typename T, size_t I>
+struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC Storage<T, I, true> : T {
   constexpr Storage() = default;
   explicit constexpr Storage(T&& v) : T(absl::forward<T>(v)) {}
   constexpr const T& get() const& { return *this; }
@@ -107,29 +119,54 @@ struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC Storage<D, I, true>
   T&& get() && { return std::move(*this); }
 };
 
-template <typename D, typename I>
+template <typename D, typename I, bool ShouldAnyUseBase>
 struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTupleImpl;
 
-template <typename... Ts, size_t... I>
-struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC
-    CompressedTupleImpl<CompressedTuple<Ts...>, absl::index_sequence<I...>>
+template <typename... Ts, size_t... I, bool ShouldAnyUseBase>
+struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTupleImpl<
+    CompressedTuple<Ts...>, absl::index_sequence<I...>, ShouldAnyUseBase>
     // We use the dummy identity function through std::integral_constant to
     // convince MSVC of accepting and expanding I in that context. Without it
     // you would get:
     //   error C3548: 'I': parameter pack cannot be used in this context
-    : Storage<CompressedTuple<Ts...>,
-              std::integral_constant<size_t, I>::value>... {
+    : uses_inheritance,
+      Storage<Ts, std::integral_constant<size_t, I>::value>... {
+  constexpr CompressedTupleImpl() = default;
+  explicit constexpr CompressedTupleImpl(Ts&&... args)
+      : Storage<Ts, I>(absl::forward<Ts>(args))... {}
+  friend CompressedTuple<Ts...>;
+};
+
+template <typename... Ts, size_t... I>
+struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTupleImpl<
+    CompressedTuple<Ts...>, absl::index_sequence<I...>, false>
+    // We use the dummy identity function as above...
+    : Storage<Ts, std::integral_constant<size_t, I>::value, false>... {
   constexpr CompressedTupleImpl() = default;
   explicit constexpr CompressedTupleImpl(Ts&&... args)
-      : Storage<CompressedTuple<Ts...>, I>(absl::forward<Ts>(args))... {}
+      : Storage<Ts, I, false>(absl::forward<Ts>(args))... {}
+  friend CompressedTuple<Ts...>;
 };
 
+std::false_type Or(std::initializer_list<std::false_type>);
+std::true_type Or(std::initializer_list<bool>);
+
+// MSVC requires this to be done separately rather than within the declaration
+// of CompressedTuple below.
+template <typename... Ts>
+constexpr bool ShouldAnyUseBase() {
+  return decltype(
+      Or({std::integral_constant<bool, ShouldUseBase<Ts>()>()...})){};
+}
+
 }  // namespace internal_compressed_tuple
 
 // Helper class to perform the Empty Base Class Optimization.
 // Ts can contain classes and non-classes, empty or not. For the ones that
 // are empty classes, we perform the CompressedTuple. If all types in Ts are
-// empty classes, then CompressedTuple<Ts...> is itself an empty class.
+// empty classes, then CompressedTuple<Ts...> is itself an empty class.  (This
+// does not apply when one or more of those empty classes is itself an empty
+// CompressedTuple.)
 //
 // To access the members, use member .get<N>() function.
 //
@@ -145,7 +182,8 @@ struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC
 template <typename... Ts>
 class ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTuple
     : private internal_compressed_tuple::CompressedTupleImpl<
-          CompressedTuple<Ts...>, absl::index_sequence_for<Ts...>> {
+          CompressedTuple<Ts...>, absl::index_sequence_for<Ts...>,
+          internal_compressed_tuple::ShouldAnyUseBase<Ts...>()> {
  private:
   template <int I>
   using ElemT = internal_compressed_tuple::ElemT<CompressedTuple, I>;
@@ -157,24 +195,24 @@ class ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTuple
 
   template <int I>
   ElemT<I>& get() & {
-    return internal_compressed_tuple::Storage<CompressedTuple, I>::get();
+    return internal_compressed_tuple::Storage<ElemT<I>, I>::get();
   }
 
   template <int I>
   constexpr const ElemT<I>& get() const& {
-    return internal_compressed_tuple::Storage<CompressedTuple, I>::get();
+    return internal_compressed_tuple::Storage<ElemT<I>, I>::get();
   }
 
   template <int I>
   ElemT<I>&& get() && {
     return std::move(*this)
-        .internal_compressed_tuple::template Storage<CompressedTuple, I>::get();
+        .internal_compressed_tuple::template Storage<ElemT<I>, I>::get();
   }
 
   template <int I>
   constexpr const ElemT<I>&& get() const&& {
     return absl::move(*this)
-        .internal_compressed_tuple::template Storage<CompressedTuple, I>::get();
+        .internal_compressed_tuple::template Storage<ElemT<I>, I>::get();
   }
 };
 
diff --git a/absl/container/internal/compressed_tuple_test.cc b/absl/container/internal/compressed_tuple_test.cc
index 28e7741c9a45..3b0ec4555abf 100644
--- a/absl/container/internal/compressed_tuple_test.cc
+++ b/absl/container/internal/compressed_tuple_test.cc
@@ -22,10 +22,8 @@
 #include "absl/memory/memory.h"
 #include "absl/utility/utility.h"
 
-namespace absl {
-namespace container_internal {
-namespace {
-
+// These are declared at global scope purely so that error messages
+// are smaller and easier to understand.
 enum class CallType { kConstRef, kConstMove };
 
 template <int>
@@ -45,6 +43,10 @@ struct TwoValues {
   U value2;
 };
 
+namespace absl {
+namespace container_internal {
+namespace {
+
 TEST(CompressedTupleTest, Sizeof) {
   EXPECT_EQ(sizeof(int), sizeof(CompressedTuple<int>));
   EXPECT_EQ(sizeof(int), sizeof(CompressedTuple<int, Empty<0>>));
@@ -120,9 +122,14 @@ TEST(CompressedTupleTest, Nested) {
   EXPECT_EQ(4 * sizeof(char),
             sizeof(CompressedTuple<CompressedTuple<char, char>,
                                    CompressedTuple<char, char>>));
-  EXPECT_TRUE(
-      (std::is_empty<CompressedTuple<CompressedTuple<Empty<0>>,
-                                     CompressedTuple<Empty<1>>>>::value));
+  EXPECT_TRUE((std::is_empty<CompressedTuple<Empty<0>, Empty<1>>>::value));
+
+  // Make sure everything still works when things are nested.
+  struct CT_Empty : CompressedTuple<Empty<0>> {};
+  CompressedTuple<Empty<0>, CT_Empty> nested_empty;
+  auto contained = nested_empty.get<0>();
+  auto nested = nested_empty.get<1>().get<0>();
+  EXPECT_TRUE((std::is_same<decltype(contained), decltype(nested)>::value));
 }
 
 TEST(CompressedTupleTest, Reference) {
diff --git a/absl/container/internal/inlined_vector.h b/absl/container/internal/inlined_vector.h
index 92c21ab96571..f117ee0c75de 100644
--- a/absl/container/internal/inlined_vector.h
+++ b/absl/container/internal/inlined_vector.h
@@ -25,6 +25,7 @@
 #include "absl/container/internal/compressed_tuple.h"
 #include "absl/memory/memory.h"
 #include "absl/meta/type_traits.h"
+#include "absl/types/span.h"
 
 namespace absl {
 namespace inlined_vector_internal {
@@ -78,6 +79,14 @@ void ConstructElements(AllocatorType* alloc_ptr, ValueType* construct_first,
   }
 }
 
+template <typename ValueType, typename ValueAdapter, typename SizeType>
+void AssignElements(ValueType* assign_first, ValueAdapter* values_ptr,
+                    SizeType assign_size) {
+  for (SizeType i = 0; i < assign_size; ++i) {
+    values_ptr->AssignNext(assign_first + i);
+  }
+}
+
 template <typename AllocatorType>
 struct StorageView {
   using pointer = typename AllocatorType::pointer;
@@ -101,6 +110,11 @@ class IteratorValueAdapter {
     ++it_;
   }
 
+  void AssignNext(pointer assign_at) {
+    *assign_at = *it_;
+    ++it_;
+  }
+
  private:
   Iterator it_;
 };
@@ -119,6 +133,8 @@ class CopyValueAdapter {
     AllocatorTraits::construct(*alloc_ptr, construct_at, *ptr_);
   }
 
+  void AssignNext(pointer assign_at) { *assign_at = *ptr_; }
+
  private:
   const_pointer ptr_;
 };
@@ -135,6 +151,44 @@ class DefaultValueAdapter {
   void ConstructNext(AllocatorType* alloc_ptr, pointer construct_at) {
     AllocatorTraits::construct(*alloc_ptr, construct_at);
   }
+
+  void AssignNext(pointer assign_at) { *assign_at = value_type(); }
+};
+
+template <typename AllocatorType>
+class AllocationTransaction {
+  using value_type = typename AllocatorType::value_type;
+  using pointer = typename AllocatorType::pointer;
+  using size_type = typename AllocatorType::size_type;
+  using AllocatorTraits = absl::allocator_traits<AllocatorType>;
+
+ public:
+  explicit AllocationTransaction(AllocatorType* alloc_ptr)
+      : alloc_data_(*alloc_ptr, nullptr) {}
+
+  AllocationTransaction(const AllocationTransaction&) = delete;
+  void operator=(const AllocationTransaction&) = delete;
+
+  AllocatorType& GetAllocator() { return alloc_data_.template get<0>(); }
+  pointer& GetData() { return alloc_data_.template get<1>(); }
+  size_type& GetCapacity() { return capacity_; }
+
+  bool DidAllocate() { return GetData() != nullptr; }
+  pointer Allocate(size_type capacity) {
+    GetData() = AllocatorTraits::allocate(GetAllocator(), capacity);
+    GetCapacity() = capacity;
+    return GetData();
+  }
+
+  ~AllocationTransaction() {
+    if (DidAllocate()) {
+      AllocatorTraits::deallocate(GetAllocator(), GetData(), GetCapacity());
+    }
+  }
+
+ private:
+  container_internal::CompressedTuple<AllocatorType, pointer> alloc_data_;
+  size_type capacity_ = 0;
 };
 
 template <typename T, size_t N, typename A>
@@ -167,6 +221,9 @@ class Storage {
   using DefaultValueAdapter =
       inlined_vector_internal::DefaultValueAdapter<allocator_type>;
 
+  using AllocationTransaction =
+      inlined_vector_internal::AllocationTransaction<allocator_type>;
+
   Storage() : metadata_() {}
 
   explicit Storage(const allocator_type& alloc)
@@ -215,19 +272,48 @@ class Storage {
 
   void SetIsAllocated() { GetSizeAndIsAllocated() |= 1; }
 
+  void UnsetIsAllocated() {
+    SetIsAllocated();
+    GetSizeAndIsAllocated() -= 1;
+  }
+
   void SetAllocatedSize(size_type size) {
     GetSizeAndIsAllocated() = (size << 1) | static_cast<size_type>(1);
   }
 
   void SetInlinedSize(size_type size) { GetSizeAndIsAllocated() = size << 1; }
 
+  void SetSize(size_type size) {
+    GetSizeAndIsAllocated() =
+        (size << 1) | static_cast<size_type>(GetIsAllocated());
+  }
+
   void AddSize(size_type count) { GetSizeAndIsAllocated() += count << 1; }
 
+  void SubtractSize(size_type count) {
+    assert(count <= GetSize());
+    GetSizeAndIsAllocated() -= count << 1;
+  }
+
   void SetAllocatedData(pointer data, size_type capacity) {
     data_.allocated.allocated_data = data;
     data_.allocated.allocated_capacity = capacity;
   }
 
+  void DeallocateIfAllocated() {
+    if (GetIsAllocated()) {
+      AllocatorTraits::deallocate(*GetAllocPtr(), GetAllocatedData(),
+                                  GetAllocatedCapacity());
+    }
+  }
+
+  void AcquireAllocation(AllocationTransaction* allocation_tx_ptr) {
+    SetAllocatedData(allocation_tx_ptr->GetData(),
+                     allocation_tx_ptr->GetCapacity());
+    allocation_tx_ptr->GetData() = nullptr;
+    allocation_tx_ptr->GetCapacity() = 0;
+  }
+
   void SwapSizeAndIsAllocated(Storage* other) {
     using std::swap;
     swap(GetSizeAndIsAllocated(), other->GetSizeAndIsAllocated());
@@ -238,11 +324,11 @@ class Storage {
     swap(data_.allocated, other->data_.allocated);
   }
 
-  void MemcpyContents(const Storage& other) {
-    assert(IsMemcpyOk::value);
+  void MemcpyFrom(const Storage& other_storage) {
+    assert(IsMemcpyOk::value || other_storage.GetIsAllocated());
 
-    GetSizeAndIsAllocated() = other.GetSizeAndIsAllocated();
-    data_ = other.data_;
+    GetSizeAndIsAllocated() = other_storage.GetSizeAndIsAllocated();
+    data_ = other_storage.data_;
   }
 
   void DestroyAndDeallocate();
@@ -250,6 +336,11 @@ class Storage {
   template <typename ValueAdapter>
   void Initialize(ValueAdapter values, size_type new_size);
 
+  template <typename ValueAdapter>
+  void Assign(ValueAdapter values, size_type new_size);
+
+  void ShrinkToFit();
+
  private:
   size_type& GetSizeAndIsAllocated() { return metadata_.template get<1>(); }
 
@@ -282,15 +373,10 @@ class Storage {
 
 template <typename T, size_t N, typename A>
 void Storage<T, N, A>::DestroyAndDeallocate() {
-  StorageView storage_view = MakeStorageView();
-
-  inlined_vector_internal::DestroyElements(GetAllocPtr(), storage_view.data,
-                                           storage_view.size);
-
-  if (GetIsAllocated()) {
-    AllocatorTraits::deallocate(*GetAllocPtr(), storage_view.data,
-                                storage_view.capacity);
-  }
+  inlined_vector_internal::DestroyElements(
+      GetAllocPtr(), (GetIsAllocated() ? GetAllocatedData() : GetInlinedData()),
+      GetSize());
+  DeallocateIfAllocated();
 }
 
 template <typename T, size_t N, typename A>
@@ -323,6 +409,91 @@ auto Storage<T, N, A>::Initialize(ValueAdapter values, size_type new_size)
   AddSize(new_size);
 }
 
+template <typename T, size_t N, typename A>
+template <typename ValueAdapter>
+auto Storage<T, N, A>::Assign(ValueAdapter values, size_type new_size) -> void {
+  StorageView storage_view = MakeStorageView();
+
+  AllocationTransaction allocation_tx(GetAllocPtr());
+
+  absl::Span<value_type> assign_loop;
+  absl::Span<value_type> construct_loop;
+  absl::Span<value_type> destroy_loop;
+
+  if (new_size > storage_view.capacity) {
+    construct_loop = {allocation_tx.Allocate(new_size), new_size};
+    destroy_loop = {storage_view.data, storage_view.size};
+  } else if (new_size > storage_view.size) {
+    assign_loop = {storage_view.data, storage_view.size};
+    construct_loop = {storage_view.data + storage_view.size,
+                      new_size - storage_view.size};
+  } else {
+    assign_loop = {storage_view.data, new_size};
+    destroy_loop = {storage_view.data + new_size, storage_view.size - new_size};
+  }
+
+  inlined_vector_internal::AssignElements(assign_loop.data(), &values,
+                                          assign_loop.size());
+  inlined_vector_internal::ConstructElements(
+      GetAllocPtr(), construct_loop.data(), &values, construct_loop.size());
+  inlined_vector_internal::DestroyElements(GetAllocPtr(), destroy_loop.data(),
+                                           destroy_loop.size());
+
+  if (allocation_tx.DidAllocate()) {
+    DeallocateIfAllocated();
+    AcquireAllocation(&allocation_tx);
+    SetIsAllocated();
+  }
+
+  SetSize(new_size);
+}
+
+template <typename T, size_t N, typename A>
+auto Storage<T, N, A>::ShrinkToFit() -> void {
+  // May only be called on allocated instances!
+  assert(GetIsAllocated());
+
+  StorageView storage_view = {GetAllocatedData(), GetSize(),
+                              GetAllocatedCapacity()};
+
+  AllocationTransaction allocation_tx(GetAllocPtr());
+
+  IteratorValueAdapter<MoveIterator> move_values(
+      MoveIterator(storage_view.data));
+
+  pointer construct_data;
+
+  if (storage_view.size <= static_cast<size_type>(N)) {
+    construct_data = GetInlinedData();
+  } else if (storage_view.size < GetAllocatedCapacity()) {
+    construct_data = allocation_tx.Allocate(storage_view.size);
+  } else {
+    return;
+  }
+
+  ABSL_INTERNAL_TRY {
+    inlined_vector_internal::ConstructElements(GetAllocPtr(), construct_data,
+                                               &move_values, storage_view.size);
+  }
+  ABSL_INTERNAL_CATCH_ANY {
+    // Writing to inlined data will trample on the existing state, thus it needs
+    // to be restored when a construction fails.
+    SetAllocatedData(storage_view.data, storage_view.capacity);
+    ABSL_INTERNAL_RETHROW;
+  }
+
+  inlined_vector_internal::DestroyElements(GetAllocPtr(), storage_view.data,
+                                           storage_view.size);
+  AllocatorTraits::deallocate(*GetAllocPtr(), storage_view.data,
+                              storage_view.capacity);
+
+  if (allocation_tx.DidAllocate()) {
+    AcquireAllocation(&allocation_tx);
+  } else {
+    UnsetIsAllocated();
+  }
+}
+
 }  // namespace inlined_vector_internal
 }  // namespace absl