Export of internal Abseil changes

--
0db7f4046f9b59c0f8c3df2f0eb7fd88fc328439 by Abseil Team <absl-team@google.com>:

Revise documentation of bit_cast:

* Removes inappropriate examples (round-tripping pointers, serialization), for which reinterpret_cast is more appropriate.
* Removes mention of "bit representation", which is not an explicit notion in C++. The best we get is "byte representation".
* Removes a circular defition of "bitcast" as itself, and instead explains what it does.
* Removes the mathism "for some values of", which is probably not totally accessible to a general audience, and in any case needless verbiage.
* Fixes comments in the example.
* Replaces some colloquialisms with simpler, more direct language.

PiperOrigin-RevId: 421791786

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e04e64df55d93c1b9a09c0483b97cc4d8763260d by Derek Mauro <dmauro@google.com>:

Update Docker image to use GCC 11.2, Clang 14 (prerelease),
CMake 3.22.1, and Bazel 4.2.2

PiperOrigin-RevId: 421658559

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d002bb3dc5cd1fc5b4cbd79a450efc894caa567c by Chris Kennelly <ckennelly@google.com>:

Add a small microbenchmark for absl::bit_width.

PiperOrigin-RevId: 421604852

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131b057d1b76ecd7170421b48d661bb958ff676b by Evan Brown <ezb@google.com>:

Adds a disabled test for EBO in nested `CompressedTuple`s.

PiperOrigin-RevId: 421413134

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e34c7876d3a1212d90c73c030ccae6169b682d43 by Jorg Brown <jorg@google.com>:

Show users a better error message if they pass a pointer to absl::Uniform.

PiperOrigin-RevId: 421090472
GitOrigin-RevId: 0db7f4046f9b59c0f8c3df2f0eb7fd88fc328439
Change-Id: I5a004e8d17e974fa4897a09d1466ae8fc65dfdbb

2 files changed, 87 insertions, 0 deletions

diff --git a/absl/numeric/BUILD.bazel b/absl/numeric/BUILD.bazel
index 1f9e0f20..eaa27dfd 100644
--- a/absl/numeric/BUILD.bazel
+++ b/absl/numeric/BUILD.bazel
@@ -37,6 +37,20 @@ cc_library(
     ],
 )
 
+cc_binary(
+    name = "bits_benchmark",
+    testonly = 1,
+    srcs = ["bits_benchmark.cc"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":bits",
+        "//absl/base:core_headers",
+        "//absl/random",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+)
+
 cc_test(
     name = "bits_test",
     size = "small",
diff --git a/absl/numeric/bits_benchmark.cc b/absl/numeric/bits_benchmark.cc
new file mode 100644
index 00000000..3de1dbfa
--- /dev/null
+++ b/absl/numeric/bits_benchmark.cc
@@ -0,0 +1,73 @@
+// Copyright 2022 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstdint>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "absl/base/optimization.h"
+#include "absl/numeric/bits.h"
+#include "absl/random/random.h"
+
+namespace absl {
+namespace {
+
+template <typename T>
+static void BM_bitwidth(benchmark::State& state) {
+  const int count = state.range(0);
+
+  absl::BitGen rng;
+  std::vector<T> values;
+  values.reserve(count);
+  for (int i = 0; i < count; ++i) {
+    values.push_back(absl::Uniform<T>(rng, 0, std::numeric_limits<T>::max()));
+  }
+
+  while (state.KeepRunningBatch(count)) {
+    for (int i = 0; i < count; ++i) {
+      benchmark::DoNotOptimize(values[i]);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_bitwidth, uint8_t)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_bitwidth, uint16_t)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_bitwidth, uint32_t)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_bitwidth, uint64_t)->Range(1, 1 << 20);
+
+template <typename T>
+static void BM_bitwidth_nonzero(benchmark::State& state) {
+  const int count = state.range(0);
+
+  absl::BitGen rng;
+  std::vector<T> values;
+  values.reserve(count);
+  for (int i = 0; i < count; ++i) {
+    values.push_back(absl::Uniform<T>(rng, 1, std::numeric_limits<T>::max()));
+  }
+
+  while (state.KeepRunningBatch(count)) {
+    for (int i = 0; i < count; ++i) {
+      const T value = values[i];
+      ABSL_INTERNAL_ASSUME(value > 0);
+      benchmark::DoNotOptimize(value);
+    }
+  }
+}
+BENCHMARK_TEMPLATE(BM_bitwidth_nonzero, uint8_t)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_bitwidth_nonzero, uint16_t)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_bitwidth_nonzero, uint32_t)->Range(1, 1 << 20);
+BENCHMARK_TEMPLATE(BM_bitwidth_nonzero, uint64_t)->Range(1, 1 << 20);
+
+}  // namespace
+}  // namespace absl