Export of internal Abseil changes.

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1c1d6e2404dfc6caa022b335df5acdac6da50fe1 by Derek Mauro <dmauro@google.com>:

Fix the internal namespacing in unaligned_access.h

PiperOrigin-RevId: 215434506

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17d4400aebf025a230690fc1c7a968ef8d85bbba by Eric Fiselier <ericwf@google.com>:

gtest depends on the GCC extension allowing variadic macros
to be passed a empty parameter pack for ..., but LLVM diagnoses
this as a GNU extension.

This patch suppresses the warning when building the absl tests.

PiperOrigin-RevId: 215426161

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f2c49dde23a9f445b9de963f1bbe840ebb568b30 by Eric Fiselier <ericwf@google.com>:

Use EXPECT_DEATH_IF_SUPPORTED instead of EXPECT_DEATH.

This avoids breaking the test when gtest doesn't support
death tests.

PiperOrigin-RevId: 215423849

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cd687c1e121709603f4fc3726b534f6a9c52cc89 by Eric Fiselier <ericwf@google.com>:

Disable LLVM's -Wmissing-variable-declarations in tests.

GCC's configuration already disables this via -Wno-missing-declarations,
this change makes LLVM do the same.

The warning would otherwise flag most tests which use ABSL_FLAG.

PiperOrigin-RevId: 215407429

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d14098824c84e3a8c8f6fb920e0335fb48fe2010 by Eric Fiselier <ericwf@google.com>:

Fix local variable shadowing in city hash implementation.

PiperOrigin-RevId: 215407249

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4b5e140ba743f0d231790a26c49083abb4329e2c by Abseil Team <absl-team@google.com>:

Make raw_hash_set::reserve 2X fast when reserve doesn't do any allocation.
Make raw_hash_set::reserve ~1% faster when reserve does some (128~4k) allocation.

PiperOrigin-RevId: 215348727

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461161e65e04b801480aa117af2534c594654ccf by Eric Fiselier <ericwf@google.com>:

Internal change

PiperOrigin-RevId: 215272283

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50413ae31ad3d3a177257416acd8ede47a17bff2 by Eric Fiselier <ericwf@google.com>:

Internal Change

PiperOrigin-RevId: 215233183

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477be54c43d61019a8fe4e190e340eb52737d383 by Abseil Team <absl-team@google.com>:

Clarify misleading comment on ABSL_ATTRIBUTE_UNUSED

PiperOrigin-RevId: 215185496

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2cafa2b5287507d3a946682aee9ab13af6d471c9 by Matt Kulukundis <kfm@google.com>:

Add support for absl::Hash to various absl in types.

PiperOrigin-RevId: 215039569

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082248901991aa3d29be0ea3689c7f213cf0fd83 by Derek Mauro <dmauro@google.com>:

Remove an instance of HAS_GLOBAL_STRING from hash_function_defaults.h

PiperOrigin-RevId: 214989094

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b929f61907f0786a6133e3a9d7287e339c0a0acb by Derek Mauro <dmauro@google.com>:

Internal import of Github #174
Fix code snippet in comment
https://github.com/abseil/abseil-cpp/pull/174

PiperOrigin-RevId: 214958849

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f2c5e829eca11c352e121f56eefbf87083305023 by Derek Mauro <dmauro@google.com>:

Internal import of GitHub #173
Fix CMake build for absl::container.
https://github.com/abseil/abseil-cpp/pull/173

PiperOrigin-RevId: 214957796

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d704f860f9fddafb99e34e6c5032e49f73874e10 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 214828181
GitOrigin-RevId: 1c1d6e2404dfc6caa022b335df5acdac6da50fe1
Change-Id: I551de2b1ba0cbaf6856cd5959358cf6651179dea

1 files changed, 13 insertions, 4 deletions

diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 0c0e5906d206..70da90f79a4f 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -1330,8 +1330,7 @@ class raw_hash_set {
   void rehash(size_t n) {
     if (n == 0 && capacity_ == 0) return;
     if (n == 0 && size_ == 0) return destroy_slots();
-    auto m = NormalizeCapacity(std::max(
-        n, static_cast<size_t>(std::ceil(size() / kMaxLoadFactor))));
+    auto m = NormalizeCapacity(std::max(n, NumSlotsFast(size())));
     // n == 0 unconditionally rehashes as per the standard.
     if (n == 0 || m > capacity_) {
       resize(m);
@@ -1339,7 +1338,7 @@ class raw_hash_set {
   }
 
   void reserve(size_t n) {
-    rehash(static_cast<size_t>(std::ceil(n / kMaxLoadFactor)));
+    rehash(NumSlotsFast(n));
   }
 
   // Extension API: support for heterogeneous keys.
@@ -1518,6 +1517,13 @@ class raw_hash_set {
     slot_type&& slot;
   };
 
+  // Computes std::ceil(n / kMaxLoadFactor). Faster than calling std::ceil.
+  static inline size_t NumSlotsFast(size_t n) {
+    return static_cast<size_t>(
+        (n * kMaxLoadFactorDenominator + (kMaxLoadFactorNumerator - 1)) /
+        kMaxLoadFactorNumerator);
+  }
+
   // "erases" the object from the container, except that it doesn't actually
   // destroy the object. It only updates all the metadata of the class.
   // This can be used in conjunction with Policy::transfer to move the object to
@@ -1825,7 +1831,10 @@ class raw_hash_set {
   }
 
   // On average each group has 2 empty slot (for the vectorized case).
-  static constexpr float kMaxLoadFactor = 14.0 / 16.0;
+  static constexpr int64_t kMaxLoadFactorNumerator = 14;
+  static constexpr int64_t kMaxLoadFactorDenominator = 16;
+  static constexpr float kMaxLoadFactor =
+      1.0 * kMaxLoadFactorNumerator / kMaxLoadFactorDenominator;
 
   // TODO(alkis): Investigate removing some of these fields:
   // - ctrl/slots can be derived from each other