Export of internal Abseil changes

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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

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

only hide retired flags if human-readable output is requested

PiperOrigin-RevId: 389835452

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

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

PiperOrigin-RevId: 389779333

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

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

PiperOrigin-RevId: 389701120

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

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

PiperOrigin-RevId: 389678813

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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

1 files changed, 29 insertions, 10 deletions

diff --git a/absl/cleanup/internal/cleanup.h b/absl/cleanup/internal/cleanup.h
index b4c40737..2783fcb7 100644
--- a/absl/cleanup/internal/cleanup.h
+++ b/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