chore(3p/abseil_cpp): unvendor abseil_cpp r/3786

we weren't actually using these sources anymore, okay?

Change-Id: If701571d9716de308d3512e1eb22c35db0877a66
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5248
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
Autosubmit: tazjin <tazjin@tvl.su>

1 files changed, 0 insertions, 804 deletions

diff --git a/third_party/abseil_cpp/absl/random/internal/nanobenchmark.cc b/third_party/abseil_cpp/absl/random/internal/nanobenchmark.cc
deleted file mode 100644
index c9181813f7f0..000000000000
--- a/third_party/abseil_cpp/absl/random/internal/nanobenchmark.cc
+++ /dev/null
@@ -1,804 +0,0 @@
-// Copyright 2017 Google Inc. All Rights Reserved.
-//
-// 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 "absl/random/internal/nanobenchmark.h"
-
-#include <sys/types.h>
-
-#include <algorithm>  // sort
-#include <atomic>
-#include <cstddef>
-#include <cstdint>
-#include <cstdlib>
-#include <cstring>  // memcpy
-#include <limits>
-#include <string>
-#include <utility>
-#include <vector>
-
-#include "absl/base/attributes.h"
-#include "absl/base/internal/raw_logging.h"
-#include "absl/random/internal/platform.h"
-#include "absl/random/internal/randen_engine.h"
-
-// OS
-#if defined(_WIN32) || defined(_WIN64)
-#define ABSL_OS_WIN
-#include <windows.h>  // NOLINT
-
-#elif defined(__ANDROID__)
-#define ABSL_OS_ANDROID
-
-#elif defined(__linux__)
-#define ABSL_OS_LINUX
-#include <sched.h>        // NOLINT
-#include <sys/syscall.h>  // NOLINT
-#endif
-
-#if defined(ABSL_ARCH_X86_64) && !defined(ABSL_OS_WIN)
-#include <cpuid.h>  // NOLINT
-#endif
-
-// __ppc_get_timebase_freq
-#if defined(ABSL_ARCH_PPC)
-#include <sys/platform/ppc.h>  // NOLINT
-#endif
-
-// clock_gettime
-#if defined(ABSL_ARCH_ARM) || defined(ABSL_ARCH_AARCH64)
-#include <time.h>  // NOLINT
-#endif
-
-// ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE prevents inlining of the method.
-#if ABSL_HAVE_ATTRIBUTE(noinline) || (defined(__GNUC__) && !defined(__clang__))
-#define ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE __attribute__((noinline))
-#elif defined(_MSC_VER)
-#define ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE __declspec(noinline)
-#else
-#define ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE
-#endif
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace random_internal_nanobenchmark {
-namespace {
-
-// For code folding.
-namespace platform {
-#if defined(ABSL_ARCH_X86_64)
-
-// TODO(janwas): Merge with the one in randen_hwaes.cc?
-void Cpuid(const uint32_t level, const uint32_t count,
-           uint32_t* ABSL_RANDOM_INTERNAL_RESTRICT abcd) {
-#if defined(ABSL_OS_WIN)
-  int regs[4];
-  __cpuidex(regs, level, count);
-  for (int i = 0; i < 4; ++i) {
-    abcd[i] = regs[i];
-  }
-#else
-  uint32_t a, b, c, d;
-  __cpuid_count(level, count, a, b, c, d);
-  abcd[0] = a;
-  abcd[1] = b;
-  abcd[2] = c;
-  abcd[3] = d;
-#endif
-}
-
-std::string BrandString() {
-  char brand_string[49];
-  uint32_t abcd[4];
-
-  // Check if brand string is supported (it is on all reasonable Intel/AMD)
-  Cpuid(0x80000000U, 0, abcd);
-  if (abcd[0] < 0x80000004U) {
-    return std::string();
-  }
-
-  for (int i = 0; i < 3; ++i) {
-    Cpuid(0x80000002U + i, 0, abcd);
-    memcpy(brand_string + i * 16, &abcd, sizeof(abcd));
-  }
-  brand_string[48] = 0;
-  return brand_string;
-}
-
-// Returns the frequency quoted inside the brand string. This does not
-// account for throttling nor Turbo Boost.
-double NominalClockRate() {
-  const std::string& brand_string = BrandString();
-  // Brand strings include the maximum configured frequency. These prefixes are
-  // defined by Intel CPUID documentation.
-  const char* prefixes[3] = {"MHz", "GHz", "THz"};
-  const double multipliers[3] = {1E6, 1E9, 1E12};
-  for (size_t i = 0; i < 3; ++i) {
-    const size_t pos_prefix = brand_string.find(prefixes[i]);
-    if (pos_prefix != std::string::npos) {
-      const size_t pos_space = brand_string.rfind(' ', pos_prefix - 1);
-      if (pos_space != std::string::npos) {
-        const std::string digits =
-            brand_string.substr(pos_space + 1, pos_prefix - pos_space - 1);
-        return std::stod(digits) * multipliers[i];
-      }
-    }
-  }
-
-  return 0.0;
-}
-
-#endif  // ABSL_ARCH_X86_64
-}  // namespace platform
-
-// Prevents the compiler from eliding the computations that led to "output".
-template <class T>
-inline void PreventElision(T&& output) {
-#ifndef ABSL_OS_WIN
-  // Works by indicating to the compiler that "output" is being read and
-  // modified. The +r constraint avoids unnecessary writes to memory, but only
-  // works for built-in types (typically FuncOutput).
-  asm volatile("" : "+r"(output) : : "memory");
-#else
-  // MSVC does not support inline assembly anymore (and never supported GCC's
-  // RTL constraints). Self-assignment with #pragma optimize("off") might be
-  // expected to prevent elision, but it does not with MSVC 2015. Type-punning
-  // with volatile pointers generates inefficient code on MSVC 2017.
-  static std::atomic<T> dummy(T{});
-  dummy.store(output, std::memory_order_relaxed);
-#endif
-}
-
-namespace timer {
-
-// Start/Stop return absolute timestamps and must be placed immediately before
-// and after the region to measure. We provide separate Start/Stop functions
-// because they use different fences.
-//
-// Background: RDTSC is not 'serializing'; earlier instructions may complete
-// after it, and/or later instructions may complete before it. 'Fences' ensure
-// regions' elapsed times are independent of such reordering. The only
-// documented unprivileged serializing instruction is CPUID, which acts as a
-// full fence (no reordering across it in either direction). Unfortunately
-// the latency of CPUID varies wildly (perhaps made worse by not initializing
-// its EAX input). Because it cannot reliably be deducted from the region's
-// elapsed time, it must not be included in the region to measure (i.e.
-// between the two RDTSC).
-//
-// The newer RDTSCP is sometimes described as serializing, but it actually
-// only serves as a half-fence with release semantics. Although all
-// instructions in the region will complete before the final timestamp is
-// captured, subsequent instructions may leak into the region and increase the
-// elapsed time. Inserting another fence after the final RDTSCP would prevent
-// such reordering without affecting the measured region.
-//
-// Fortunately, such a fence exists. The LFENCE instruction is only documented
-// to delay later loads until earlier loads are visible. However, Intel's
-// reference manual says it acts as a full fence (waiting until all earlier
-// instructions have completed, and delaying later instructions until it
-// completes). AMD assigns the same behavior to MFENCE.
-//
-// We need a fence before the initial RDTSC to prevent earlier instructions
-// from leaking into the region, and arguably another after RDTSC to avoid
-// region instructions from completing before the timestamp is recorded.
-// When surrounded by fences, the additional RDTSCP half-fence provides no
-// benefit, so the initial timestamp can be recorded via RDTSC, which has
-// lower overhead than RDTSCP because it does not read TSC_AUX. In summary,
-// we define Start = LFENCE/RDTSC/LFENCE; Stop = RDTSCP/LFENCE.
-//
-// Using Start+Start leads to higher variance and overhead than Stop+Stop.
-// However, Stop+Stop includes an LFENCE in the region measurements, which
-// adds a delay dependent on earlier loads. The combination of Start+Stop
-// is faster than Start+Start and more consistent than Stop+Stop because
-// the first LFENCE already delayed subsequent loads before the measured
-// region. This combination seems not to have been considered in prior work:
-// http://akaros.cs.berkeley.edu/lxr/akaros/kern/arch/x86/rdtsc_test.c
-//
-// Note: performance counters can measure 'exact' instructions-retired or
-// (unhalted) cycle counts. The RDPMC instruction is not serializing and also
-// requires fences. Unfortunately, it is not accessible on all OSes and we
-// prefer to avoid kernel-mode drivers. Performance counters are also affected
-// by several under/over-count errata, so we use the TSC instead.
-
-// Returns a 64-bit timestamp in unit of 'ticks'; to convert to seconds,
-// divide by InvariantTicksPerSecond.
-inline uint64_t Start64() {
-  uint64_t t;
-#if defined(ABSL_ARCH_PPC)
-  asm volatile("mfspr %0, %1" : "=r"(t) : "i"(268));
-#elif defined(ABSL_ARCH_X86_64)
-#if defined(ABSL_OS_WIN)
-  _ReadWriteBarrier();
-  _mm_lfence();
-  _ReadWriteBarrier();
-  t = __rdtsc();
-  _ReadWriteBarrier();
-  _mm_lfence();
-  _ReadWriteBarrier();
-#else
-  asm volatile(
-      "lfence\n\t"
-      "rdtsc\n\t"
-      "shl $32, %%rdx\n\t"
-      "or %%rdx, %0\n\t"
-      "lfence"
-      : "=a"(t)
-      :
-      // "memory" avoids reordering. rdx = TSC >> 32.
-      // "cc" = flags modified by SHL.
-      : "rdx", "memory", "cc");
-#endif
-#else
-  // Fall back to OS - unsure how to reliably query cntvct_el0 frequency.
-  timespec ts;
-  clock_gettime(CLOCK_REALTIME, &ts);
-  t = ts.tv_sec * 1000000000LL + ts.tv_nsec;
-#endif
-  return t;
-}
-
-inline uint64_t Stop64() {
-  uint64_t t;
-#if defined(ABSL_ARCH_X86_64)
-#if defined(ABSL_OS_WIN)
-  _ReadWriteBarrier();
-  unsigned aux;
-  t = __rdtscp(&aux);
-  _ReadWriteBarrier();
-  _mm_lfence();
-  _ReadWriteBarrier();
-#else
-  // Use inline asm because __rdtscp generates code to store TSC_AUX (ecx).
-  asm volatile(
-      "rdtscp\n\t"
-      "shl $32, %%rdx\n\t"
-      "or %%rdx, %0\n\t"
-      "lfence"
-      : "=a"(t)
-      :
-      // "memory" avoids reordering. rcx = TSC_AUX. rdx = TSC >> 32.
-      // "cc" = flags modified by SHL.
-      : "rcx", "rdx", "memory", "cc");
-#endif
-#else
-  t = Start64();
-#endif
-  return t;
-}
-
-// Returns a 32-bit timestamp with about 4 cycles less overhead than
-// Start64. Only suitable for measuring very short regions because the
-// timestamp overflows about once a second.
-inline uint32_t Start32() {
-  uint32_t t;
-#if defined(ABSL_ARCH_X86_64)
-#if defined(ABSL_OS_WIN)
-  _ReadWriteBarrier();
-  _mm_lfence();
-  _ReadWriteBarrier();
-  t = static_cast<uint32_t>(__rdtsc());
-  _ReadWriteBarrier();
-  _mm_lfence();
-  _ReadWriteBarrier();
-#else
-  asm volatile(
-      "lfence\n\t"
-      "rdtsc\n\t"
-      "lfence"
-      : "=a"(t)
-      :
-      // "memory" avoids reordering. rdx = TSC >> 32.
-      : "rdx", "memory");
-#endif
-#else
-  t = static_cast<uint32_t>(Start64());
-#endif
-  return t;
-}
-
-inline uint32_t Stop32() {
-  uint32_t t;
-#if defined(ABSL_ARCH_X86_64)
-#if defined(ABSL_OS_WIN)
-  _ReadWriteBarrier();
-  unsigned aux;
-  t = static_cast<uint32_t>(__rdtscp(&aux));
-  _ReadWriteBarrier();
-  _mm_lfence();
-  _ReadWriteBarrier();
-#else
-  // Use inline asm because __rdtscp generates code to store TSC_AUX (ecx).
-  asm volatile(
-      "rdtscp\n\t"
-      "lfence"
-      : "=a"(t)
-      :
-      // "memory" avoids reordering. rcx = TSC_AUX. rdx = TSC >> 32.
-      : "rcx", "rdx", "memory");
-#endif
-#else
-  t = static_cast<uint32_t>(Stop64());
-#endif
-  return t;
-}
-
-}  // namespace timer
-
-namespace robust_statistics {
-
-// Sorts integral values in ascending order (e.g. for Mode). About 3x faster
-// than std::sort for input distributions with very few unique values.
-template <class T>
-void CountingSort(T* values, size_t num_values) {
-  // Unique values and their frequency (similar to flat_map).
-  using Unique = std::pair<T, int>;
-  std::vector<Unique> unique;
-  for (size_t i = 0; i < num_values; ++i) {
-    const T value = values[i];
-    const auto pos =
-        std::find_if(unique.begin(), unique.end(),
-                     [value](const Unique u) { return u.first == value; });
-    if (pos == unique.end()) {
-      unique.push_back(std::make_pair(value, 1));
-    } else {
-      ++pos->second;
-    }
-  }
-
-  // Sort in ascending order of value (pair.first).
-  std::sort(unique.begin(), unique.end());
-
-  // Write that many copies of each unique value to the array.
-  T* ABSL_RANDOM_INTERNAL_RESTRICT p = values;
-  for (const auto& value_count : unique) {
-    std::fill(p, p + value_count.second, value_count.first);
-    p += value_count.second;
-  }
-  ABSL_RAW_CHECK(p == values + num_values, "Did not produce enough output");
-}
-
-// @return i in [idx_begin, idx_begin + half_count) that minimizes
-// sorted[i + half_count] - sorted[i].
-template <typename T>
-size_t MinRange(const T* const ABSL_RANDOM_INTERNAL_RESTRICT sorted,
-                const size_t idx_begin, const size_t half_count) {
-  T min_range = (std::numeric_limits<T>::max)();
-  size_t min_idx = 0;
-
-  for (size_t idx = idx_begin; idx < idx_begin + half_count; ++idx) {
-    ABSL_RAW_CHECK(sorted[idx] <= sorted[idx + half_count], "Not sorted");
-    const T range = sorted[idx + half_count] - sorted[idx];
-    if (range < min_range) {
-      min_range = range;
-      min_idx = idx;
-    }
-  }
-
-  return min_idx;
-}
-
-// Returns an estimate of the mode by calling MinRange on successively
-// halved intervals. "sorted" must be in ascending order. This is the
-// Half Sample Mode estimator proposed by Bickel in "On a fast, robust
-// estimator of the mode", with complexity O(N log N). The mode is less
-// affected by outliers in highly-skewed distributions than the median.
-// The averaging operation below assumes "T" is an unsigned integer type.
-template <typename T>
-T ModeOfSorted(const T* const ABSL_RANDOM_INTERNAL_RESTRICT sorted,
-               const size_t num_values) {
-  size_t idx_begin = 0;
-  size_t half_count = num_values / 2;
-  while (half_count > 1) {
-    idx_begin = MinRange(sorted, idx_begin, half_count);
-    half_count >>= 1;
-  }
-
-  const T x = sorted[idx_begin + 0];
-  if (half_count == 0) {
-    return x;
-  }
-  ABSL_RAW_CHECK(half_count == 1, "Should stop at half_count=1");
-  const T average = (x + sorted[idx_begin + 1] + 1) / 2;
-  return average;
-}
-
-// Returns the mode. Side effect: sorts "values".
-template <typename T>
-T Mode(T* values, const size_t num_values) {
-  CountingSort(values, num_values);
-  return ModeOfSorted(values, num_values);
-}
-
-template <typename T, size_t N>
-T Mode(T (&values)[N]) {
-  return Mode(&values[0], N);
-}
-
-// Returns the median value. Side effect: sorts "values".
-template <typename T>
-T Median(T* values, const size_t num_values) {
-  ABSL_RAW_CHECK(num_values != 0, "Empty input");
-  std::sort(values, values + num_values);
-  const size_t half = num_values / 2;
-  // Odd count: return middle
-  if (num_values % 2) {
-    return values[half];
-  }
-  // Even count: return average of middle two.
-  return (values[half] + values[half - 1] + 1) / 2;
-}
-
-// Returns a robust measure of variability.
-template <typename T>
-T MedianAbsoluteDeviation(const T* values, const size_t num_values,
-                          const T median) {
-  ABSL_RAW_CHECK(num_values != 0, "Empty input");
-  std::vector<T> abs_deviations;
-  abs_deviations.reserve(num_values);
-  for (size_t i = 0; i < num_values; ++i) {
-    const int64_t abs = std::abs(int64_t(values[i]) - int64_t(median));
-    abs_deviations.push_back(static_cast<T>(abs));
-  }
-  return Median(abs_deviations.data(), num_values);
-}
-
-}  // namespace robust_statistics
-
-// Ticks := platform-specific timer values (CPU cycles on x86). Must be
-// unsigned to guarantee wraparound on overflow. 32 bit timers are faster to
-// read than 64 bit.
-using Ticks = uint32_t;
-
-// Returns timer overhead / minimum measurable difference.
-Ticks TimerResolution() {
-  // Nested loop avoids exceeding stack/L1 capacity.
-  Ticks repetitions[Params::kTimerSamples];
-  for (size_t rep = 0; rep < Params::kTimerSamples; ++rep) {
-    Ticks samples[Params::kTimerSamples];
-    for (size_t i = 0; i < Params::kTimerSamples; ++i) {
-      const Ticks t0 = timer::Start32();
-      const Ticks t1 = timer::Stop32();
-      samples[i] = t1 - t0;
-    }
-    repetitions[rep] = robust_statistics::Mode(samples);
-  }
-  return robust_statistics::Mode(repetitions);
-}
-
-static const Ticks timer_resolution = TimerResolution();
-
-// Estimates the expected value of "lambda" values with a variable number of
-// samples until the variability "rel_mad" is less than "max_rel_mad".
-template <class Lambda>
-Ticks SampleUntilStable(const double max_rel_mad, double* rel_mad,
-                        const Params& p, const Lambda& lambda) {
-  auto measure_duration = [&lambda]() -> Ticks {
-    const Ticks t0 = timer::Start32();
-    lambda();
-    const Ticks t1 = timer::Stop32();
-    return t1 - t0;
-  };
-
-  // Choose initial samples_per_eval based on a single estimated duration.
-  Ticks est = measure_duration();
-  static const double ticks_per_second = InvariantTicksPerSecond();
-  const size_t ticks_per_eval = ticks_per_second * p.seconds_per_eval;
-  size_t samples_per_eval = ticks_per_eval / est;
-  samples_per_eval = (std::max)(samples_per_eval, p.min_samples_per_eval);
-
-  std::vector<Ticks> samples;
-  samples.reserve(1 + samples_per_eval);
-  samples.push_back(est);
-
-  // Percentage is too strict for tiny differences, so also allow a small
-  // absolute "median absolute deviation".
-  const Ticks max_abs_mad = (timer_resolution + 99) / 100;
-  *rel_mad = 0.0;  // ensure initialized
-
-  for (size_t eval = 0; eval < p.max_evals; ++eval, samples_per_eval *= 2) {
-    samples.reserve(samples.size() + samples_per_eval);
-    for (size_t i = 0; i < samples_per_eval; ++i) {
-      const Ticks r = measure_duration();
-      samples.push_back(r);
-    }
-
-    if (samples.size() >= p.min_mode_samples) {
-      est = robust_statistics::Mode(samples.data(), samples.size());
-    } else {
-      // For "few" (depends also on the variance) samples, Median is safer.
-      est = robust_statistics::Median(samples.data(), samples.size());
-    }
-    ABSL_RAW_CHECK(est != 0, "Estimator returned zero duration");
-
-    // Median absolute deviation (mad) is a robust measure of 'variability'.
-    const Ticks abs_mad = robust_statistics::MedianAbsoluteDeviation(
-        samples.data(), samples.size(), est);
-    *rel_mad = static_cast<double>(static_cast<int>(abs_mad)) / est;
-
-    if (*rel_mad <= max_rel_mad || abs_mad <= max_abs_mad) {
-      if (p.verbose) {
-        ABSL_RAW_LOG(INFO,
-                     "%6zu samples => %5u (abs_mad=%4u, rel_mad=%4.2f%%)\n",
-                     samples.size(), est, abs_mad, *rel_mad * 100.0);
-      }
-      return est;
-    }
-  }
-
-  if (p.verbose) {
-    ABSL_RAW_LOG(WARNING,
-                 "rel_mad=%4.2f%% still exceeds %4.2f%% after %6zu samples.\n",
-                 *rel_mad * 100.0, max_rel_mad * 100.0, samples.size());
-  }
-  return est;
-}
-
-using InputVec = std::vector<FuncInput>;
-
-// Returns vector of unique input values.
-InputVec UniqueInputs(const FuncInput* inputs, const size_t num_inputs) {
-  InputVec unique(inputs, inputs + num_inputs);
-  std::sort(unique.begin(), unique.end());
-  unique.erase(std::unique(unique.begin(), unique.end()), unique.end());
-  return unique;
-}
-
-// Returns how often we need to call func for sufficient precision, or zero
-// on failure (e.g. the elapsed time is too long for a 32-bit tick count).
-size_t NumSkip(const Func func, const void* arg, const InputVec& unique,
-               const Params& p) {
-  // Min elapsed ticks for any input.
-  Ticks min_duration = ~0u;
-
-  for (const FuncInput input : unique) {
-    // Make sure a 32-bit timer is sufficient.
-    const uint64_t t0 = timer::Start64();
-    PreventElision(func(arg, input));
-    const uint64_t t1 = timer::Stop64();
-    const uint64_t elapsed = t1 - t0;
-    if (elapsed >= (1ULL << 30)) {
-      ABSL_RAW_LOG(WARNING,
-                   "Measurement failed: need 64-bit timer for input=%zu\n",
-                   static_cast<size_t>(input));
-      return 0;
-    }
-
-    double rel_mad;
-    const Ticks total = SampleUntilStable(
-        p.target_rel_mad, &rel_mad, p,
-        [func, arg, input]() { PreventElision(func(arg, input)); });
-    min_duration = (std::min)(min_duration, total - timer_resolution);
-  }
-
-  // Number of repetitions required to reach the target resolution.
-  const size_t max_skip = p.precision_divisor;
-  // Number of repetitions given the estimated duration.
-  const size_t num_skip =
-      min_duration == 0 ? 0 : (max_skip + min_duration - 1) / min_duration;
-  if (p.verbose) {
-    ABSL_RAW_LOG(INFO, "res=%u max_skip=%zu min_dur=%u num_skip=%zu\n",
-                 timer_resolution, max_skip, min_duration, num_skip);
-  }
-  return num_skip;
-}
-
-// Replicates inputs until we can omit "num_skip" occurrences of an input.
-InputVec ReplicateInputs(const FuncInput* inputs, const size_t num_inputs,
-                         const size_t num_unique, const size_t num_skip,
-                         const Params& p) {
-  InputVec full;
-  if (num_unique == 1) {
-    full.assign(p.subset_ratio * num_skip, inputs[0]);
-    return full;
-  }
-
-  full.reserve(p.subset_ratio * num_skip * num_inputs);
-  for (size_t i = 0; i < p.subset_ratio * num_skip; ++i) {
-    full.insert(full.end(), inputs, inputs + num_inputs);
-  }
-  absl::random_internal::randen_engine<uint32_t> rng;
-  std::shuffle(full.begin(), full.end(), rng);
-  return full;
-}
-
-// Copies the "full" to "subset" in the same order, but with "num_skip"
-// randomly selected occurrences of "input_to_skip" removed.
-void FillSubset(const InputVec& full, const FuncInput input_to_skip,
-                const size_t num_skip, InputVec* subset) {
-  const size_t count = std::count(full.begin(), full.end(), input_to_skip);
-  // Generate num_skip random indices: which occurrence to skip.
-  std::vector<uint32_t> omit;
-  // Replacement for std::iota, not yet available in MSVC builds.
-  omit.reserve(count);
-  for (size_t i = 0; i < count; ++i) {
-    omit.push_back(i);
-  }
-  // omit[] is the same on every call, but that's OK because they identify the
-  // Nth instance of input_to_skip, so the position within full[] differs.
-  absl::random_internal::randen_engine<uint32_t> rng;
-  std::shuffle(omit.begin(), omit.end(), rng);
-  omit.resize(num_skip);
-  std::sort(omit.begin(), omit.end());
-
-  uint32_t occurrence = ~0u;  // 0 after preincrement
-  size_t idx_omit = 0;        // cursor within omit[]
-  size_t idx_subset = 0;      // cursor within *subset
-  for (const FuncInput next : full) {
-    if (next == input_to_skip) {
-      ++occurrence;
-      // Haven't removed enough already
-      if (idx_omit < num_skip) {
-        // This one is up for removal
-        if (occurrence == omit[idx_omit]) {
-          ++idx_omit;
-          continue;
-        }
-      }
-    }
-    if (idx_subset < subset->size()) {
-      (*subset)[idx_subset++] = next;
-    }
-  }
-  ABSL_RAW_CHECK(idx_subset == subset->size(), "idx_subset not at end");
-  ABSL_RAW_CHECK(idx_omit == omit.size(), "idx_omit not at end");
-  ABSL_RAW_CHECK(occurrence == count - 1, "occurrence not at end");
-}
-
-// Returns total ticks elapsed for all inputs.
-Ticks TotalDuration(const Func func, const void* arg, const InputVec* inputs,
-                    const Params& p, double* max_rel_mad) {
-  double rel_mad;
-  const Ticks duration =
-      SampleUntilStable(p.target_rel_mad, &rel_mad, p, [func, arg, inputs]() {
-        for (const FuncInput input : *inputs) {
-          PreventElision(func(arg, input));
-        }
-      });
-  *max_rel_mad = (std::max)(*max_rel_mad, rel_mad);
-  return duration;
-}
-
-// (Nearly) empty Func for measuring timer overhead/resolution.
-ABSL_RANDOM_INTERNAL_ATTRIBUTE_NEVER_INLINE FuncOutput
-EmptyFunc(const void* arg, const FuncInput input) {
-  return input;
-}
-
-// Returns overhead of accessing inputs[] and calling a function; this will
-// be deducted from future TotalDuration return values.
-Ticks Overhead(const void* arg, const InputVec* inputs, const Params& p) {
-  double rel_mad;
-  // Zero tolerance because repeatability is crucial and EmptyFunc is fast.
-  return SampleUntilStable(0.0, &rel_mad, p, [arg, inputs]() {
-    for (const FuncInput input : *inputs) {
-      PreventElision(EmptyFunc(arg, input));
-    }
-  });
-}
-
-}  // namespace
-
-void PinThreadToCPU(int cpu) {
-  // We might migrate to another CPU before pinning below, but at least cpu
-  // will be one of the CPUs on which this thread ran.
-#if defined(ABSL_OS_WIN)
-  if (cpu < 0) {
-    cpu = static_cast<int>(GetCurrentProcessorNumber());
-    ABSL_RAW_CHECK(cpu >= 0, "PinThreadToCPU detect failed");
-    if (cpu >= 64) {
-      // NOTE: On wine, at least, GetCurrentProcessorNumber() sometimes returns
-      // a value > 64, which is out of range. When this happens, log a message
-      // and don't set a cpu affinity.
-      ABSL_RAW_LOG(ERROR, "Invalid CPU number: %d", cpu);
-      return;
-    }
-  } else if (cpu >= 64) {
-    // User specified an explicit CPU affinity > the valid range.
-    ABSL_RAW_LOG(FATAL, "Invalid CPU number: %d", cpu);
-  }
-  const DWORD_PTR prev = SetThreadAffinityMask(GetCurrentThread(), 1ULL << cpu);
-  ABSL_RAW_CHECK(prev != 0, "SetAffinity failed");
-#elif defined(ABSL_OS_LINUX) && !defined(ABSL_OS_ANDROID)
-  if (cpu < 0) {
-    cpu = sched_getcpu();
-    ABSL_RAW_CHECK(cpu >= 0, "PinThreadToCPU detect failed");
-  }
-  const pid_t pid = 0;  // current thread
-  cpu_set_t set;
-  CPU_ZERO(&set);
-  CPU_SET(cpu, &set);
-  const int err = sched_setaffinity(pid, sizeof(set), &set);
-  ABSL_RAW_CHECK(err == 0, "SetAffinity failed");
-#endif
-}
-
-// Returns tick rate. Invariant means the tick counter frequency is independent
-// of CPU throttling or sleep. May be expensive, caller should cache the result.
-double InvariantTicksPerSecond() {
-#if defined(ABSL_ARCH_PPC)
-  return __ppc_get_timebase_freq();
-#elif defined(ABSL_ARCH_X86_64)
-  // We assume the TSC is invariant; it is on all recent Intel/AMD CPUs.
-  return platform::NominalClockRate();
-#else
-  // Fall back to clock_gettime nanoseconds.
-  return 1E9;
-#endif
-}
-
-size_t MeasureImpl(const Func func, const void* arg, const size_t num_skip,
-                   const InputVec& unique, const InputVec& full,
-                   const Params& p, Result* results) {
-  const float mul = 1.0f / static_cast<int>(num_skip);
-
-  InputVec subset(full.size() - num_skip);
-  const Ticks overhead = Overhead(arg, &full, p);
-  const Ticks overhead_skip = Overhead(arg, &subset, p);
-  if (overhead < overhead_skip) {
-    ABSL_RAW_LOG(WARNING, "Measurement failed: overhead %u < %u\n", overhead,
-                 overhead_skip);
-    return 0;
-  }
-
-  if (p.verbose) {
-    ABSL_RAW_LOG(INFO, "#inputs=%5zu,%5zu overhead=%5u,%5u\n", full.size(),
-                 subset.size(), overhead, overhead_skip);
-  }
-
-  double max_rel_mad = 0.0;
-  const Ticks total = TotalDuration(func, arg, &full, p, &max_rel_mad);
-
-  for (size_t i = 0; i < unique.size(); ++i) {
-    FillSubset(full, unique[i], num_skip, &subset);
-    const Ticks total_skip = TotalDuration(func, arg, &subset, p, &max_rel_mad);
-
-    if (total < total_skip) {
-      ABSL_RAW_LOG(WARNING, "Measurement failed: total %u < %u\n", total,
-                   total_skip);
-      return 0;
-    }
-
-    const Ticks duration = (total - overhead) - (total_skip - overhead_skip);
-    results[i].input = unique[i];
-    results[i].ticks = duration * mul;
-    results[i].variability = max_rel_mad;
-  }
-
-  return unique.size();
-}
-
-size_t Measure(const Func func, const void* arg, const FuncInput* inputs,
-               const size_t num_inputs, Result* results, const Params& p) {
-  ABSL_RAW_CHECK(num_inputs != 0, "No inputs");
-
-  const InputVec unique = UniqueInputs(inputs, num_inputs);
-  const size_t num_skip = NumSkip(func, arg, unique, p);  // never 0
-  if (num_skip == 0) return 0;  // NumSkip already printed error message
-
-  const InputVec full =
-      ReplicateInputs(inputs, num_inputs, unique.size(), num_skip, p);
-
-  // MeasureImpl may fail up to p.max_measure_retries times.
-  for (size_t i = 0; i < p.max_measure_retries; i++) {
-    auto result = MeasureImpl(func, arg, num_skip, unique, full, p, results);
-    if (result != 0) {
-      return result;
-    }
-  }
-  // All retries failed. (Unusual)
-  return 0;
-}
-
-}  // namespace random_internal_nanobenchmark
-ABSL_NAMESPACE_END
-}  // namespace absl