Export of internal Abseil changes

--
77cd6291781bc39e8472c706163d6951fe2ae573 by Derek Mauro <dmauro@google.com>:

absl::uint128: Use intrinsics for more operations when available

This change also inlines the division and modulus operators when
intrinsics are available for better code generation.

Fixes #987

PiperOrigin-RevId: 389895706

--
fa23339584599e07ebcb4d0a857e2553b017757c by Abseil Team <absl-team@google.com>:

only hide retired flags if human-readable output is requested

PiperOrigin-RevId: 389835452

--
f1111f2b88359d4b253d4d81681c8a488458a36e by Martijn Vels <mvels@google.com>:

Add helpers IsFlat(), IsExternal(), etc to improve readability

PiperOrigin-RevId: 389779333

--
785b8712261e41695ebeeb64b4317f93b37adc11 by Martijn Vels <mvels@google.com>:

Split off 'concat' and 'btree' RepMemoryUsageLeaf and RepMemoryUsageDataEdge

PiperOrigin-RevId: 389701120

--
5264bffebffc2b377bf7e18f0ce69a3ed38c6629 by CJ Johnson <johnsoncj@google.com>:

Eagerly destroy `Callback` in `absl::Cleanup`

PiperOrigin-RevId: 389678813

--
a05312f0668458e97c50ca932c8f974c1508ebf2 by Abseil Team <absl-team@google.com>:

Have one instance of empty_group per program, rather than one per translation unit.

https://stackoverflow.com/questions/185624/static-variables-in-an-inlined-function

PiperOrigin-RevId: 389185845
GitOrigin-RevId: 77cd6291781bc39e8472c706163d6951fe2ae573
Change-Id: Iac8d9cb27707a9562c831c77a552d1fb4bb0405f

absl/cleanup/cleanup.h

@@ -86,25 +86,25 @@ class ABSL_MUST_USE_RESULT Cleanup final {
                 "Callbacks that return values are not supported.");
 
  public:
-  Cleanup(Callback callback)  // NOLINT
-      : storage_(std::move(callback), /* is_callback_engaged = */ true) {}
+  Cleanup(Callback callback) : storage_(std::move(callback)) {}  // NOLINT
 
   Cleanup(Cleanup&& other) = default;
 
   void Cancel() && {
     ABSL_HARDENING_ASSERT(storage_.IsCallbackEngaged());
-    storage_.DisengageCallback();
+    storage_.DestroyCallback();
   }
 
   void Invoke() && {
     ABSL_HARDENING_ASSERT(storage_.IsCallbackEngaged());
-    storage_.DisengageCallback();
     storage_.InvokeCallback();
+    storage_.DestroyCallback();
   }
 
   ~Cleanup() {
     if (storage_.IsCallbackEngaged()) {
       storage_.InvokeCallback();
+      storage_.DestroyCallback();
     }
   }
 

absl/cleanup/cleanup_test.cc

@@ -264,4 +264,48 @@ TYPED_TEST(CleanupTest, Move) {
   EXPECT_FALSE(called);  // Destructor shouldn't invoke the callback
 }
 
+int DestructionCount = 0;
+
+struct DestructionCounter {
+  void operator()() {}
+
+  ~DestructionCounter() { ++DestructionCount; }
+};
+
+TYPED_TEST(CleanupTest, DestructorDestroys) {
+  {
+    auto cleanup =
+        absl::MakeCleanup(TypeParam::AsCallback(DestructionCounter()));
+    DestructionCount = 0;
+  }
+
+  EXPECT_EQ(DestructionCount, 1);  // Engaged cleanup destroys
+}
+
+TYPED_TEST(CleanupTest, CancelDestroys) {
+  {
+    auto cleanup =
+        absl::MakeCleanup(TypeParam::AsCallback(DestructionCounter()));
+    DestructionCount = 0;
+
+    std::move(cleanup).Cancel();
+    EXPECT_EQ(DestructionCount, 1);  // Cancel destroys
+  }
+
+  EXPECT_EQ(DestructionCount, 1);  // Canceled cleanup does not double destroy
+}
+
+TYPED_TEST(CleanupTest, InvokeDestroys) {
+  {
+    auto cleanup =
+        absl::MakeCleanup(TypeParam::AsCallback(DestructionCounter()));
+    DestructionCount = 0;
+
+    std::move(cleanup).Invoke();
+    EXPECT_EQ(DestructionCount, 1);  // Invoke destroys
+  }
+
+  EXPECT_EQ(DestructionCount, 1);  // Invoked cleanup does not double destroy
+}
+
 }  // namespace

absl/cleanup/internal/cleanup.h

@@ -15,10 +15,12 @@
 #ifndef ABSL_CLEANUP_INTERNAL_CLEANUP_H_
 #define ABSL_CLEANUP_INTERNAL_CLEANUP_H_
 
+#include <new>
 #include <type_traits>
 #include <utility>
 
 #include "absl/base/internal/invoke.h"
+#include "absl/base/macros.h"
 #include "absl/base/thread_annotations.h"
 #include "absl/utility/utility.h"
 
@@ -45,14 +47,22 @@ class Storage {
  public:
   Storage() = delete;
 
-  Storage(Callback callback, bool is_callback_engaged)
-      : callback_(std::move(callback)),
-        is_callback_engaged_(is_callback_engaged) {}
+  explicit Storage(Callback callback) {
+    // Placement-new into a character buffer is used for eager destruction when
+    // the cleanup is invoked or cancelled. To ensure this optimizes well, the
+    // behavior is implemented locally instead of using an absl::optional.
+    ::new (GetCallbackBuffer()) Callback(std::move(callback));
+    is_callback_engaged_ = true;
+  }
+
+  Storage(Storage&& other) {
+    ABSL_HARDENING_ASSERT(other.IsCallbackEngaged());
 
-  Storage(Storage&& other)
-      : callback_(std::move(other.callback_)),
-        is_callback_engaged_(
-            absl::exchange(other.is_callback_engaged_, false)) {}
+    ::new (GetCallbackBuffer()) Callback(std::move(other.GetCallback()));
+    is_callback_engaged_ = true;
+
+    other.DestroyCallback();
+  }
 
   Storage(const Storage& other) = delete;
 
@@ -60,17 +70,26 @@ class Storage {
 
   Storage& operator=(const Storage& other) = delete;
 
+  void* GetCallbackBuffer() { return static_cast<void*>(+callback_buffer_); }
+
+  Callback& GetCallback() {
+    return *reinterpret_cast<Callback*>(GetCallbackBuffer());
+  }
+
   bool IsCallbackEngaged() const { return is_callback_engaged_; }
 
-  void DisengageCallback() { is_callback_engaged_ = false; }
+  void DestroyCallback() {
+    is_callback_engaged_ = false;
+    GetCallback().~Callback();
+  }
 
   void InvokeCallback() ABSL_NO_THREAD_SAFETY_ANALYSIS {
-    std::move(callback_)();
+    std::move(GetCallback())();
   }
 
  private:
-  Callback callback_;
   bool is_callback_engaged_;
+  alignas(Callback) char callback_buffer_[sizeof(Callback)];
 };
 
 }  // namespace cleanup_internal

absl/container/internal/raw_hash_set.cc

@@ -23,6 +23,12 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
+ABSL_CONST_INIT ABSL_DLL alignas(16) 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};
+
 constexpr size_t Group::kWidth;
 
 // Returns "random" seed.

absl/container/internal/raw_hash_set.h

@@ -291,13 +291,9 @@ static_assert(ctrl_t::kDeleted == static_cast<ctrl_t>(-2),
 
 // A single block of empty control bytes for tables without any slots allocated.
 // This enables removing a branch in the hot path of find().
+ABSL_DLL extern const ctrl_t kEmptyGroup[16];
 inline ctrl_t* EmptyGroup() {
-  alignas(16) static constexpr ctrl_t empty_group[] = {
-      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};
-  return const_cast<ctrl_t*>(empty_group);
+  return const_cast<ctrl_t*>(kEmptyGroup);
 }
 
 // Mixes a randomly generated per-process seed with `hash` and `ctrl` to

absl/flags/internal/usage.cc

@@ -17,6 +17,7 @@
 
 #include <stdint.h>
 
+#include <algorithm>
 #include <functional>
 #include <map>
 #include <ostream>
@@ -255,9 +256,6 @@ void FlagsHelpImpl(std::ostream& out, PerFlagFilter filter_cb,
       matching_flags;
 
   flags_internal::ForEachFlag([&](absl::CommandLineFlag& flag) {
-    // Ignore retired flags.
-    if (flag.IsRetired()) return;
-
     // If the flag has been stripped, pretend that it doesn't exist.
     if (flag.Help() == flags_internal::kStrippedFlagHelp) return;
 
@@ -275,6 +273,14 @@ void FlagsHelpImpl(std::ostream& out, PerFlagFilter filter_cb,
   absl::string_view file_separator;     // controls blank lines between files
   for (auto& package : matching_flags) {
     if (format == HelpFormat::kHumanReadable) {
+      // Hide packages with only retired flags
+      bool all_package_flags_are_retired = true;
+      for (const auto& flags_in_file : package.second) {
+        for (const auto* flag : flags_in_file.second) {
+          all_package_flags_are_retired &= flag->IsRetired();
+        }
+      }
+      if (all_package_flags_are_retired) continue;
       out << package_separator;
       package_separator = "\n\n";
     }
@@ -334,8 +340,11 @@ void FlagsHelpImpl(std::ostream& out,
 // Produces the help message describing specific flag.
 void FlagHelp(std::ostream& out, const CommandLineFlag& flag,
               HelpFormat format) {
-  if (format == HelpFormat::kHumanReadable)
+  if (format == HelpFormat::kHumanReadable) {
+    // Ignore retired flags
+    if (flag.IsRetired()) return;
     flags_internal::FlagHelpHumanReadable(flag, out);
+  }
 }
 
 // --------------------------------------------------------------------

absl/flags/internal/usage_test.cc

@@ -61,6 +61,9 @@ ABSL_FLAG(
     "Even more long long long long long long long long long long long long "
     "help message.");
 
+ABSL_RETIRED_FLAG(int64_t, usage_reporting_test_flag_07, 1,
+                  "usage_reporting_test_flag_07 help message");
+
 namespace {
 
 namespace flags = absl::flags_internal;

absl/numeric/int128.cc

@@ -138,28 +138,21 @@ uint128::uint128(float v) : uint128(MakeUint128FromFloat(v)) {}
 uint128::uint128(double v) : uint128(MakeUint128FromFloat(v)) {}
 uint128::uint128(long double v) : uint128(MakeUint128FromFloat(v)) {}
 
+#if !defined(ABSL_HAVE_INTRINSIC_INT128)
 uint128 operator/(uint128 lhs, uint128 rhs) {
-#if defined(ABSL_HAVE_INTRINSIC_INT128)
-  return static_cast<unsigned __int128>(lhs) /
-         static_cast<unsigned __int128>(rhs);
-#else  // ABSL_HAVE_INTRINSIC_INT128
   uint128 quotient = 0;
   uint128 remainder = 0;
   DivModImpl(lhs, rhs, &quotient, &remainder);
   return quotient;
-#endif  // ABSL_HAVE_INTRINSIC_INT128
 }
+
 uint128 operator%(uint128 lhs, uint128 rhs) {
-#if defined(ABSL_HAVE_INTRINSIC_INT128)
-  return static_cast<unsigned __int128>(lhs) %
-         static_cast<unsigned __int128>(rhs);
-#else  // ABSL_HAVE_INTRINSIC_INT128
   uint128 quotient = 0;
   uint128 remainder = 0;
   DivModImpl(lhs, rhs, &quotient, &remainder);
   return remainder;
-#endif  // ABSL_HAVE_INTRINSIC_INT128
 }
+#endif  // !defined(ABSL_HAVE_INTRINSIC_INT128)
 
 namespace {
 

absl/numeric/int128.h

@@ -18,6 +18,10 @@
 // -----------------------------------------------------------------------------
 //
 // This header file defines 128-bit integer types, `uint128` and `int128`.
+//
+// TODO(absl-team): This module is inconsistent as many inline `uint128` methods
+// are defined in this file, while many inline `int128` methods are defined in
+// the `int128_*_intrinsic.inc` files.
 
 #ifndef ABSL_NUMERIC_INT128_H_
 #define ABSL_NUMERIC_INT128_H_
@@ -783,8 +787,13 @@ inline uint128::operator long double() const {
 // Comparison operators.
 
 inline bool operator==(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) ==
+         static_cast<unsigned __int128>(rhs);
+#else
   return (Uint128Low64(lhs) == Uint128Low64(rhs) &&
           Uint128High64(lhs) == Uint128High64(rhs));
+#endif
 }
 
 inline bool operator!=(uint128 lhs, uint128 rhs) {
@@ -819,52 +828,76 @@ constexpr inline int128 operator+(int128 val) {
 }
 
 inline uint128 operator-(uint128 val) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return -static_cast<unsigned __int128>(val);
+#else
   uint64_t hi = ~Uint128High64(val);
   uint64_t lo = ~Uint128Low64(val) + 1;
   if (lo == 0) ++hi;  // carry
   return MakeUint128(hi, lo);
+#endif
 }
 
 constexpr inline bool operator!(uint128 val) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return !static_cast<unsigned __int128>(val);
+#else
   return !Uint128High64(val) && !Uint128Low64(val);
+#endif
 }
 
 // Logical operators.
 
 constexpr inline uint128 operator~(uint128 val) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return ~static_cast<unsigned __int128>(val);
+#else
   return MakeUint128(~Uint128High64(val), ~Uint128Low64(val));
+#endif
 }
 
 constexpr inline uint128 operator|(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) |
+         static_cast<unsigned __int128>(rhs);
+#else
   return MakeUint128(Uint128High64(lhs) | Uint128High64(rhs),
-                           Uint128Low64(lhs) | Uint128Low64(rhs));
+                     Uint128Low64(lhs) | Uint128Low64(rhs));
+#endif
 }
 
 constexpr inline uint128 operator&(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) &
+         static_cast<unsigned __int128>(rhs);
+#else
   return MakeUint128(Uint128High64(lhs) & Uint128High64(rhs),
-                           Uint128Low64(lhs) & Uint128Low64(rhs));
+                     Uint128Low64(lhs) & Uint128Low64(rhs));
+#endif
 }
 
 constexpr inline uint128 operator^(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) ^
+         static_cast<unsigned __int128>(rhs);
+#else
   return MakeUint128(Uint128High64(lhs) ^ Uint128High64(rhs),
-                           Uint128Low64(lhs) ^ Uint128Low64(rhs));
+                     Uint128Low64(lhs) ^ Uint128Low64(rhs));
+#endif
 }
 
 inline uint128& uint128::operator|=(uint128 other) {
-  hi_ |= other.hi_;
-  lo_ |= other.lo_;
+  *this = *this | other;
   return *this;
 }
 
 inline uint128& uint128::operator&=(uint128 other) {
-  hi_ &= other.hi_;
-  lo_ &= other.lo_;
+  *this = *this & other;
   return *this;
 }
 
 inline uint128& uint128::operator^=(uint128 other) {
-  hi_ ^= other.hi_;
-  lo_ ^= other.lo_;
+  *this = *this ^ other;
   return *this;
 }
 
@@ -907,21 +940,31 @@ inline uint128 operator>>(uint128 lhs, int amount) {
 }
 
 inline uint128 operator+(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) +
+         static_cast<unsigned __int128>(rhs);
+#else
   uint128 result = MakeUint128(Uint128High64(lhs) + Uint128High64(rhs),
                                Uint128Low64(lhs) + Uint128Low64(rhs));
   if (Uint128Low64(result) < Uint128Low64(lhs)) {  // check for carry
     return MakeUint128(Uint128High64(result) + 1, Uint128Low64(result));
   }
   return result;
+#endif
 }
 
 inline uint128 operator-(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+  return static_cast<unsigned __int128>(lhs) -
+         static_cast<unsigned __int128>(rhs);
+#else
   uint128 result = MakeUint128(Uint128High64(lhs) - Uint128High64(rhs),
                                Uint128Low64(lhs) - Uint128Low64(rhs));
   if (Uint128Low64(lhs) < Uint128Low64(rhs)) {  // check for carry
     return MakeUint128(Uint128High64(result) - 1, Uint128Low64(result));
   }
   return result;
+#endif
 }
 
 inline uint128 operator*(uint128 lhs, uint128 rhs) {
@@ -951,6 +994,18 @@ inline uint128 operator*(uint128 lhs, uint128 rhs) {
 #endif  // ABSL_HAVE_INTRINSIC128
 }
 
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+inline uint128 operator/(uint128 lhs, uint128 rhs) {
+  return static_cast<unsigned __int128>(lhs) /
+         static_cast<unsigned __int128>(rhs);
+}
+
+inline uint128 operator%(uint128 lhs, uint128 rhs) {
+  return static_cast<unsigned __int128>(lhs) %
+         static_cast<unsigned __int128>(rhs);
+}
+#endif
+
 // Increment/decrement operators.
 
 inline uint128 uint128::operator++(int) {

absl/strings/internal/cord_internal.h

@@ -216,6 +216,14 @@ struct CordRep {
   // padding space from the base class (clang and gcc do, MSVC does not, etc)
   uint8_t storage[3];
 
+  // Returns true if this instance's tag matches the requested type.
+  constexpr bool IsRing() const { return tag == RING; }
+  constexpr bool IsConcat() const { return tag == CONCAT; }
+  constexpr bool IsSubstring() const { return tag == SUBSTRING; }
+  constexpr bool IsExternal() const { return tag == EXTERNAL; }
+  constexpr bool IsFlat() const { return tag >= FLAT; }
+  constexpr bool IsBtree() const { return tag == BTREE; }
+
   inline CordRepRing* ring();
   inline const CordRepRing* ring() const;
   inline CordRepConcat* concat();
@@ -226,7 +234,6 @@ struct CordRep {
   inline const CordRepExternal* external() const;
   inline CordRepFlat* flat();
   inline const CordRepFlat* flat() const;
-
   inline CordRepBtree* btree();
   inline const CordRepBtree* btree() const;
 
@@ -277,7 +284,7 @@ struct CordRepExternal : public CordRep {
   ExternalReleaserInvoker releaser_invoker;
 
   // Deletes (releases) the external rep.
-  // Requires rep != nullptr and rep->tag == EXTERNAL
+  // Requires rep != nullptr and rep->IsExternal()
   static void Delete(CordRep* rep);
 };
 
@@ -320,7 +327,7 @@ struct CordRepExternalImpl
 };
 
 inline void CordRepExternal::Delete(CordRep* rep) {
-  assert(rep != nullptr && rep->tag == EXTERNAL);
+  assert(rep != nullptr && rep->IsExternal());
   auto* rep_external = static_cast<CordRepExternal*>(rep);
   assert(rep_external->releaser_invoker != nullptr);
   rep_external->releaser_invoker(rep_external);
@@ -531,32 +538,32 @@ class InlineData {
 static_assert(sizeof(InlineData) == kMaxInline + 1, "");
 
 inline CordRepConcat* CordRep::concat() {
-  assert(tag == CONCAT);
+  assert(IsConcat());
   return static_cast<CordRepConcat*>(this);
 }
 
 inline const CordRepConcat* CordRep::concat() const {
-  assert(tag == CONCAT);
+  assert(IsConcat());
   return static_cast<const CordRepConcat*>(this);
 }
 
 inline CordRepSubstring* CordRep::substring() {
-  assert(tag == SUBSTRING);
+  assert(IsSubstring());
   return static_cast<CordRepSubstring*>(this);
 }
 
 inline const CordRepSubstring* CordRep::substring() const {
-  assert(tag == SUBSTRING);
+  assert(IsSubstring());
   return static_cast<const CordRepSubstring*>(this);
 }
 
 inline CordRepExternal* CordRep::external() {
-  assert(tag == EXTERNAL);
+  assert(IsExternal());
   return static_cast<CordRepExternal*>(this);
 }
 
 inline const CordRepExternal* CordRep::external() const {
-  assert(tag == EXTERNAL);
+  assert(IsExternal());
   return static_cast<const CordRepExternal*>(this);
 }
 

absl/strings/internal/cord_rep_btree.cc

@@ -79,7 +79,7 @@ void DumpAll(const CordRep* rep, bool include_contents, std::ostream& stream,
   // indented by two spaces per recursive depth.
   stream << std::string(depth * 2, ' ') << sharing << " (" << sptr << ") ";
 
-  if (rep->tag == BTREE) {
+  if (rep->IsBtree()) {
     const CordRepBtree* node = rep->btree();
     std::string label =
         node->height() ? absl::StrCat("Node(", node->height(), ")") : "Leaf";
@@ -378,7 +378,7 @@ bool CordRepBtree::IsValid(const CordRepBtree* tree, bool shallow) {
   }
 
   NODE_CHECK_VALID(tree != nullptr);
-  NODE_CHECK_EQ(tree->tag, BTREE);
+  NODE_CHECK_VALID(tree->IsBtree());
   NODE_CHECK_VALID(tree->height() <= kMaxHeight);
   NODE_CHECK_VALID(tree->begin() < tree->capacity());
   NODE_CHECK_VALID(tree->end() <= tree->capacity());
@@ -387,7 +387,7 @@ bool CordRepBtree::IsValid(const CordRepBtree* tree, bool shallow) {
   for (CordRep* edge : tree->Edges()) {
     NODE_CHECK_VALID(edge != nullptr);
     if (tree->height() > 0) {
-      NODE_CHECK_VALID(edge->tag == BTREE);
+      NODE_CHECK_VALID(edge->IsBtree());
       NODE_CHECK_VALID(edge->btree()->height() == tree->height() - 1);
     } else {
       NODE_CHECK_VALID(IsDataEdge(edge));
@@ -889,7 +889,7 @@ Span<char> CordRepBtree::GetAppendBufferSlow(size_t size) {
 }
 
 CordRepBtree* CordRepBtree::CreateSlow(CordRep* rep) {
-  if (rep->tag == BTREE) return rep->btree();
+  if (rep->IsBtree()) return rep->btree();
 
   CordRepBtree* node = nullptr;
   auto consume = [&node](CordRep* r, size_t offset, size_t length) {
@@ -905,7 +905,7 @@ CordRepBtree* CordRepBtree::CreateSlow(CordRep* rep) {
 }
 
 CordRepBtree* CordRepBtree::AppendSlow(CordRepBtree* tree, CordRep* rep) {
-  if (ABSL_PREDICT_TRUE(rep->tag == BTREE)) {
+  if (ABSL_PREDICT_TRUE(rep->IsBtree())) {
     return MergeTrees(tree, rep->btree());
   }
   auto consume = [&tree](CordRep* r, size_t offset, size_t length) {
@@ -917,7 +917,7 @@ CordRepBtree* CordRepBtree::AppendSlow(CordRepBtree* tree, CordRep* rep) {
 }
 
 CordRepBtree* CordRepBtree::PrependSlow(CordRepBtree* tree, CordRep* rep) {
-  if (ABSL_PREDICT_TRUE(rep->tag == BTREE)) {
+  if (ABSL_PREDICT_TRUE(rep->IsBtree())) {
     return MergeTrees(rep->btree(), tree);
   }
   auto consume = [&tree](CordRep* r, size_t offset, size_t length) {

absl/strings/internal/cord_rep_btree.h

@@ -153,7 +153,7 @@ class CordRepBtree : public CordRep {
   };
 
   // Creates a btree from the given input. Adopts a ref of `rep`.
-  // If the input `rep` is itself a btree, i.e., `tag == BTREE`, then this
+  // If the input `rep` is itself a btree, i.e., `IsBtree()`, then this
   // function immediately returns `rep->btree()`. If the input is a valid data
   // edge (see IsDataEdge()), then a new leaf node is returned containing `rep`
   // as the sole data edge. Else, the input is assumed to be a (legacy) concat
@@ -514,12 +514,12 @@ class CordRepBtree : public CordRep {
 };
 
 inline CordRepBtree* CordRep::btree() {
-  assert(tag == BTREE);
+  assert(IsBtree());
   return static_cast<CordRepBtree*>(this);
 }
 
 inline const CordRepBtree* CordRep::btree() const {
-  assert(tag == BTREE);
+  assert(IsBtree());
   return static_cast<const CordRepBtree*>(this);
 }
 
@@ -589,7 +589,7 @@ inline CordRepBtree* CordRepBtree::New(int height) {
 
 inline CordRepBtree* CordRepBtree::New(CordRep* rep) {
   CordRepBtree* tree = new CordRepBtree;
-  int height = rep->tag == BTREE ? rep->btree()->height() + 1 : 0;
+  int height = rep->IsBtree() ? rep->btree()->height() + 1 : 0;
   tree->length = rep->length;
   tree->InitInstance(height, /*begin=*/0, /*end=*/1);
   tree->edges_[0] = rep;

absl/strings/internal/cord_rep_ring.cc

@@ -40,7 +40,7 @@ using index_type = CordRepRing::index_type;
 enum class Direction { kForward, kReversed };
 
 inline bool IsFlatOrExternal(CordRep* rep) {
-  return rep->tag >= FLAT || rep->tag == EXTERNAL;
+  return rep->IsFlat() || rep->IsExternal();
 }
 
 // Verifies that n + extra <= kMaxCapacity: throws std::length_error otherwise.
@@ -229,7 +229,7 @@ void CordRepRing::SetCapacityForTesting(size_t capacity) {
 }
 
 void CordRepRing::Delete(CordRepRing* rep) {
-  assert(rep != nullptr && rep->tag == RING);
+  assert(rep != nullptr && rep->IsRing());
 #if defined(__cpp_sized_deallocation)
   size_t size = AllocSize(rep->capacity_);
   rep->~CordRepRing();
@@ -360,7 +360,7 @@ CordRepRing* CordRepRing::Create(CordRep* child, size_t extra) {
   if (IsFlatOrExternal(child)) {
     return CreateFromLeaf(child, 0, length, extra);
   }
-  if (child->tag == RING) {
+  if (child->IsRing()) {
     return Mutable(child->ring(), extra);
   }
   return CreateSlow(child, extra);
@@ -433,7 +433,7 @@ CordRepRing* CordRepRing::AddRing(CordRepRing* rep, CordRepRing* ring,
 
 CordRepRing* CordRepRing::AppendSlow(CordRepRing* rep, CordRep* child) {
   Consume(child, [&rep](CordRep* child_arg, size_t offset, size_t len) {
-    if (child_arg->tag == RING) {
+    if (child_arg->IsRing()) {
       rep = AddRing<AddMode::kAppend>(rep, child_arg->ring(), offset, len);
     } else {
       rep = AppendLeaf(rep, child_arg, offset, len);
@@ -460,7 +460,7 @@ CordRepRing* CordRepRing::Append(CordRepRing* rep, CordRep* child) {
   if (IsFlatOrExternal(child)) {
     return AppendLeaf(rep, child, 0, length);
   }
-  if (child->tag == RING) {
+  if (child->IsRing()) {
     return AddRing<AddMode::kAppend>(rep, child->ring(), 0, length);
   }
   return AppendSlow(rep, child);
@@ -496,7 +496,7 @@ CordRepRing* CordRepRing::Prepend(CordRepRing* rep, CordRep* child) {
   if (IsFlatOrExternal(child)) {
     return PrependLeaf(rep, child, 0, length);
   }
-  if (child->tag == RING) {
+  if (child->IsRing()) {
     return AddRing<AddMode::kPrepend>(rep, child->ring(), 0, length);
   }
   return PrependSlow(rep, child);

absl/strings/internal/cord_rep_ring.h

@@ -570,12 +570,12 @@ inline CordRepRing::Position CordRepRing::FindTail(index_type head,
 
 // Now that CordRepRing is defined, we can define CordRep's helper casts:
 inline CordRepRing* CordRep::ring() {
-  assert(tag == RING);
+  assert(IsRing());
   return static_cast<CordRepRing*>(this);
 }
 
 inline const CordRepRing* CordRep::ring() const {
-  assert(tag == RING);
+  assert(IsRing());
   return static_cast<const CordRepRing*>(this);
 }