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, 567 deletions

diff --git a/third_party/abseil_cpp/absl/time/clock.cc b/third_party/abseil_cpp/absl/time/clock.cc
deleted file mode 100644
index 6862e011be1f..000000000000
--- a/third_party/abseil_cpp/absl/time/clock.cc
+++ /dev/null
@@ -1,567 +0,0 @@
-// Copyright 2017 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 "absl/time/clock.h"
-
-#include "absl/base/attributes.h"
-
-#ifdef _WIN32
-#include <windows.h>
-#endif
-
-#include <algorithm>
-#include <atomic>
-#include <cerrno>
-#include <cstdint>
-#include <ctime>
-#include <limits>
-
-#include "absl/base/internal/spinlock.h"
-#include "absl/base/internal/unscaledcycleclock.h"
-#include "absl/base/macros.h"
-#include "absl/base/port.h"
-#include "absl/base/thread_annotations.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-Time Now() {
-  // TODO(bww): Get a timespec instead so we don't have to divide.
-  int64_t n = absl::GetCurrentTimeNanos();
-  if (n >= 0) {
-    return time_internal::FromUnixDuration(
-        time_internal::MakeDuration(n / 1000000000, n % 1000000000 * 4));
-  }
-  return time_internal::FromUnixDuration(absl::Nanoseconds(n));
-}
-ABSL_NAMESPACE_END
-}  // namespace absl
-
-// Decide if we should use the fast GetCurrentTimeNanos() algorithm
-// based on the cyclecounter, otherwise just get the time directly
-// from the OS on every call. This can be chosen at compile-time via
-// -DABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS=[0|1]
-#ifndef ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS
-#if ABSL_USE_UNSCALED_CYCLECLOCK
-#define ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS 1
-#else
-#define ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS 0
-#endif
-#endif
-
-#if defined(__APPLE__) || defined(_WIN32)
-#include "absl/time/internal/get_current_time_chrono.inc"
-#else
-#include "absl/time/internal/get_current_time_posix.inc"
-#endif
-
-// Allows override by test.
-#ifndef GET_CURRENT_TIME_NANOS_FROM_SYSTEM
-#define GET_CURRENT_TIME_NANOS_FROM_SYSTEM() \
-  ::absl::time_internal::GetCurrentTimeNanosFromSystem()
-#endif
-
-#if !ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-int64_t GetCurrentTimeNanos() { return GET_CURRENT_TIME_NANOS_FROM_SYSTEM(); }
-ABSL_NAMESPACE_END
-}  // namespace absl
-#else  // Use the cyclecounter-based implementation below.
-
-// Allows override by test.
-#ifndef GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW
-#define GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW() \
-  ::absl::time_internal::UnscaledCycleClockWrapperForGetCurrentTime::Now()
-#endif
-
-// The following counters are used only by the test code.
-static int64_t stats_initializations;
-static int64_t stats_reinitializations;
-static int64_t stats_calibrations;
-static int64_t stats_slow_paths;
-static int64_t stats_fast_slow_paths;
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace time_internal {
-// This is a friend wrapper around UnscaledCycleClock::Now()
-// (needed to access UnscaledCycleClock).
-class UnscaledCycleClockWrapperForGetCurrentTime {
- public:
-  static int64_t Now() { return base_internal::UnscaledCycleClock::Now(); }
-};
-}  // namespace time_internal
-
-// uint64_t is used in this module to provide an extra bit in multiplications
-
-// Return the time in ns as told by the kernel interface.  Place in *cycleclock
-// the value of the cycleclock at about the time of the syscall.
-// This call represents the time base that this module synchronizes to.
-// Ensures that *cycleclock does not step back by up to (1 << 16) from
-// last_cycleclock, to discard small backward counter steps.  (Larger steps are
-// assumed to be complete resyncs, which shouldn't happen.  If they do, a full
-// reinitialization of the outer algorithm should occur.)
-static int64_t GetCurrentTimeNanosFromKernel(uint64_t last_cycleclock,
-                                             uint64_t *cycleclock) {
-  // We try to read clock values at about the same time as the kernel clock.
-  // This value gets adjusted up or down as estimate of how long that should
-  // take, so we can reject attempts that take unusually long.
-  static std::atomic<uint64_t> approx_syscall_time_in_cycles{10 * 1000};
-
-  uint64_t local_approx_syscall_time_in_cycles =  // local copy
-      approx_syscall_time_in_cycles.load(std::memory_order_relaxed);
-
-  int64_t current_time_nanos_from_system;
-  uint64_t before_cycles;
-  uint64_t after_cycles;
-  uint64_t elapsed_cycles;
-  int loops = 0;
-  do {
-    before_cycles = GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW();
-    current_time_nanos_from_system = GET_CURRENT_TIME_NANOS_FROM_SYSTEM();
-    after_cycles = GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW();
-    // elapsed_cycles is unsigned, so is large on overflow
-    elapsed_cycles = after_cycles - before_cycles;
-    if (elapsed_cycles >= local_approx_syscall_time_in_cycles &&
-        ++loops == 20) {  // clock changed frequencies?  Back off.
-      loops = 0;
-      if (local_approx_syscall_time_in_cycles < 1000 * 1000) {
-        local_approx_syscall_time_in_cycles =
-            (local_approx_syscall_time_in_cycles + 1) << 1;
-      }
-      approx_syscall_time_in_cycles.store(
-          local_approx_syscall_time_in_cycles,
-          std::memory_order_relaxed);
-    }
-  } while (elapsed_cycles >= local_approx_syscall_time_in_cycles ||
-           last_cycleclock - after_cycles < (static_cast<uint64_t>(1) << 16));
-
-  // Number of times in a row we've seen a kernel time call take substantially
-  // less than approx_syscall_time_in_cycles.
-  static std::atomic<uint32_t> seen_smaller{ 0 };
-
-  // Adjust approx_syscall_time_in_cycles to be within a factor of 2
-  // of the typical time to execute one iteration of the loop above.
-  if ((local_approx_syscall_time_in_cycles >> 1) < elapsed_cycles) {
-    // measured time is no smaller than half current approximation
-    seen_smaller.store(0, std::memory_order_relaxed);
-  } else if (seen_smaller.fetch_add(1, std::memory_order_relaxed) >= 3) {
-    // smaller delays several times in a row; reduce approximation by 12.5%
-    const uint64_t new_approximation =
-        local_approx_syscall_time_in_cycles -
-        (local_approx_syscall_time_in_cycles >> 3);
-    approx_syscall_time_in_cycles.store(new_approximation,
-                                        std::memory_order_relaxed);
-    seen_smaller.store(0, std::memory_order_relaxed);
-  }
-
-  *cycleclock = after_cycles;
-  return current_time_nanos_from_system;
-}
-
-
-// ---------------------------------------------------------------------
-// An implementation of reader-write locks that use no atomic ops in the read
-// case.  This is a generalization of Lamport's method for reading a multiword
-// clock.  Increment a word on each write acquisition, using the low-order bit
-// as a spinlock; the word is the high word of the "clock".  Readers read the
-// high word, then all other data, then the high word again, and repeat the
-// read if the reads of the high words yields different answers, or an odd
-// value (either case suggests possible interference from a writer).
-// Here we use a spinlock to ensure only one writer at a time, rather than
-// spinning on the bottom bit of the word to benefit from SpinLock
-// spin-delay tuning.
-
-// Acquire seqlock (*seq) and return the value to be written to unlock.
-static inline uint64_t SeqAcquire(std::atomic<uint64_t> *seq) {
-  uint64_t x = seq->fetch_add(1, std::memory_order_relaxed);
-
-  // We put a release fence between update to *seq and writes to shared data.
-  // Thus all stores to shared data are effectively release operations and
-  // update to *seq above cannot be re-ordered past any of them.  Note that
-  // this barrier is not for the fetch_add above.  A release barrier for the
-  // fetch_add would be before it, not after.
-  std::atomic_thread_fence(std::memory_order_release);
-
-  return x + 2;   // original word plus 2
-}
-
-// Release seqlock (*seq) by writing x to it---a value previously returned by
-// SeqAcquire.
-static inline void SeqRelease(std::atomic<uint64_t> *seq, uint64_t x) {
-  // The unlock store to *seq must have release ordering so that all
-  // updates to shared data must finish before this store.
-  seq->store(x, std::memory_order_release);  // release lock for readers
-}
-
-// ---------------------------------------------------------------------
-
-// "nsscaled" is unit of time equal to a (2**kScale)th of a nanosecond.
-enum { kScale = 30 };
-
-// The minimum interval between samples of the time base.
-// We pick enough time to amortize the cost of the sample,
-// to get a reasonably accurate cycle counter rate reading,
-// and not so much that calculations will overflow 64-bits.
-static const uint64_t kMinNSBetweenSamples = 2000 << 20;
-
-// We require that kMinNSBetweenSamples shifted by kScale
-// have at least a bit left over for 64-bit calculations.
-static_assert(((kMinNSBetweenSamples << (kScale + 1)) >> (kScale + 1)) ==
-               kMinNSBetweenSamples,
-               "cannot represent kMaxBetweenSamplesNSScaled");
-
-// A reader-writer lock protecting the static locations below.
-// See SeqAcquire() and SeqRelease() above.
-ABSL_CONST_INIT static absl::base_internal::SpinLock lock(
-    absl::kConstInit, base_internal::SCHEDULE_KERNEL_ONLY);
-ABSL_CONST_INIT static std::atomic<uint64_t> seq(0);
-
-// data from a sample of the kernel's time value
-struct TimeSampleAtomic {
-  std::atomic<uint64_t> raw_ns;              // raw kernel time
-  std::atomic<uint64_t> base_ns;             // our estimate of time
-  std::atomic<uint64_t> base_cycles;         // cycle counter reading
-  std::atomic<uint64_t> nsscaled_per_cycle;  // cycle period
-  // cycles before we'll sample again (a scaled reciprocal of the period,
-  // to avoid a division on the fast path).
-  std::atomic<uint64_t> min_cycles_per_sample;
-};
-// Same again, but with non-atomic types
-struct TimeSample {
-  uint64_t raw_ns;                 // raw kernel time
-  uint64_t base_ns;                // our estimate of time
-  uint64_t base_cycles;            // cycle counter reading
-  uint64_t nsscaled_per_cycle;     // cycle period
-  uint64_t min_cycles_per_sample;  // approx cycles before next sample
-};
-
-static struct TimeSampleAtomic last_sample;   // the last sample; under seq
-
-static int64_t GetCurrentTimeNanosSlowPath() ABSL_ATTRIBUTE_COLD;
-
-// Read the contents of *atomic into *sample.
-// Each field is read atomically, but to maintain atomicity between fields,
-// the access must be done under a lock.
-static void ReadTimeSampleAtomic(const struct TimeSampleAtomic *atomic,
-                                 struct TimeSample *sample) {
-  sample->base_ns = atomic->base_ns.load(std::memory_order_relaxed);
-  sample->base_cycles = atomic->base_cycles.load(std::memory_order_relaxed);
-  sample->nsscaled_per_cycle =
-      atomic->nsscaled_per_cycle.load(std::memory_order_relaxed);
-  sample->min_cycles_per_sample =
-      atomic->min_cycles_per_sample.load(std::memory_order_relaxed);
-  sample->raw_ns = atomic->raw_ns.load(std::memory_order_relaxed);
-}
-
-// Public routine.
-// Algorithm:  We wish to compute real time from a cycle counter.  In normal
-// operation, we construct a piecewise linear approximation to the kernel time
-// source, using the cycle counter value.  The start of each line segment is at
-// the same point as the end of the last, but may have a different slope (that
-// is, a different idea of the cycle counter frequency).  Every couple of
-// seconds, the kernel time source is sampled and compared with the current
-// approximation.  A new slope is chosen that, if followed for another couple
-// of seconds, will correct the error at the current position.  The information
-// for a sample is in the "last_sample" struct.  The linear approximation is
-//   estimated_time = last_sample.base_ns +
-//     last_sample.ns_per_cycle * (counter_reading - last_sample.base_cycles)
-// (ns_per_cycle is actually stored in different units and scaled, to avoid
-// overflow).  The base_ns of the next linear approximation is the
-// estimated_time using the last approximation; the base_cycles is the cycle
-// counter value at that time; the ns_per_cycle is the number of ns per cycle
-// measured since the last sample, but adjusted so that most of the difference
-// between the estimated_time and the kernel time will be corrected by the
-// estimated time to the next sample.  In normal operation, this algorithm
-// relies on:
-// - the cycle counter and kernel time rates not changing a lot in a few
-//   seconds.
-// - the client calling into the code often compared to a couple of seconds, so
-//   the time to the next correction can be estimated.
-// Any time ns_per_cycle is not known, a major error is detected, or the
-// assumption about frequent calls is violated, the implementation returns the
-// kernel time.  It records sufficient data that a linear approximation can
-// resume a little later.
-
-int64_t GetCurrentTimeNanos() {
-  // read the data from the "last_sample" struct (but don't need raw_ns yet)
-  // The reads of "seq" and test of the values emulate a reader lock.
-  uint64_t base_ns;
-  uint64_t base_cycles;
-  uint64_t nsscaled_per_cycle;
-  uint64_t min_cycles_per_sample;
-  uint64_t seq_read0;
-  uint64_t seq_read1;
-
-  // If we have enough information to interpolate, the value returned will be
-  // derived from this cycleclock-derived time estimate.  On some platforms
-  // (POWER) the function to retrieve this value has enough complexity to
-  // contribute to register pressure - reading it early before initializing
-  // the other pieces of the calculation minimizes spill/restore instructions,
-  // minimizing icache cost.
-  uint64_t now_cycles = GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW();
-
-  // Acquire pairs with the barrier in SeqRelease - if this load sees that
-  // store, the shared-data reads necessarily see that SeqRelease's updates
-  // to the same shared data.
-  seq_read0 = seq.load(std::memory_order_acquire);
-
-  base_ns = last_sample.base_ns.load(std::memory_order_relaxed);
-  base_cycles = last_sample.base_cycles.load(std::memory_order_relaxed);
-  nsscaled_per_cycle =
-      last_sample.nsscaled_per_cycle.load(std::memory_order_relaxed);
-  min_cycles_per_sample =
-      last_sample.min_cycles_per_sample.load(std::memory_order_relaxed);
-
-  // This acquire fence pairs with the release fence in SeqAcquire.  Since it
-  // is sequenced between reads of shared data and seq_read1, the reads of
-  // shared data are effectively acquiring.
-  std::atomic_thread_fence(std::memory_order_acquire);
-
-  // The shared-data reads are effectively acquire ordered, and the
-  // shared-data writes are effectively release ordered. Therefore if our
-  // shared-data reads see any of a particular update's shared-data writes,
-  // seq_read1 is guaranteed to see that update's SeqAcquire.
-  seq_read1 = seq.load(std::memory_order_relaxed);
-
-  // Fast path.  Return if min_cycles_per_sample has not yet elapsed since the
-  // last sample, and we read a consistent sample.  The fast path activates
-  // only when min_cycles_per_sample is non-zero, which happens when we get an
-  // estimate for the cycle time.  The predicate will fail if now_cycles <
-  // base_cycles, or if some other thread is in the slow path.
-  //
-  // Since we now read now_cycles before base_ns, it is possible for now_cycles
-  // to be less than base_cycles (if we were interrupted between those loads and
-  // last_sample was updated). This is harmless, because delta_cycles will wrap
-  // and report a time much much bigger than min_cycles_per_sample. In that case
-  // we will take the slow path.
-  uint64_t delta_cycles = now_cycles - base_cycles;
-  if (seq_read0 == seq_read1 && (seq_read0 & 1) == 0 &&
-      delta_cycles < min_cycles_per_sample) {
-    return base_ns + ((delta_cycles * nsscaled_per_cycle) >> kScale);
-  }
-  return GetCurrentTimeNanosSlowPath();
-}
-
-// Return (a << kScale)/b.
-// Zero is returned if b==0.   Scaling is performed internally to
-// preserve precision without overflow.
-static uint64_t SafeDivideAndScale(uint64_t a, uint64_t b) {
-  // Find maximum safe_shift so that
-  //  0 <= safe_shift <= kScale  and  (a << safe_shift) does not overflow.
-  int safe_shift = kScale;
-  while (((a << safe_shift) >> safe_shift) != a) {
-    safe_shift--;
-  }
-  uint64_t scaled_b = b >> (kScale - safe_shift);
-  uint64_t quotient = 0;
-  if (scaled_b != 0) {
-    quotient = (a << safe_shift) / scaled_b;
-  }
-  return quotient;
-}
-
-static uint64_t UpdateLastSample(
-    uint64_t now_cycles, uint64_t now_ns, uint64_t delta_cycles,
-    const struct TimeSample *sample) ABSL_ATTRIBUTE_COLD;
-
-// The slow path of GetCurrentTimeNanos().  This is taken while gathering
-// initial samples, when enough time has elapsed since the last sample, and if
-// any other thread is writing to last_sample.
-//
-// Manually mark this 'noinline' to minimize stack frame size of the fast
-// path.  Without this, sometimes a compiler may inline this big block of code
-// into the fast path.  That causes lots of register spills and reloads that
-// are unnecessary unless the slow path is taken.
-//
-// TODO(absl-team): Remove this attribute when our compiler is smart enough
-// to do the right thing.
-ABSL_ATTRIBUTE_NOINLINE
-static int64_t GetCurrentTimeNanosSlowPath() ABSL_LOCKS_EXCLUDED(lock) {
-  // Serialize access to slow-path.  Fast-path readers are not blocked yet, and
-  // code below must not modify last_sample until the seqlock is acquired.
-  lock.Lock();
-
-  // Sample the kernel time base.  This is the definition of
-  // "now" if we take the slow path.
-  static uint64_t last_now_cycles;  // protected by lock
-  uint64_t now_cycles;
-  uint64_t now_ns = GetCurrentTimeNanosFromKernel(last_now_cycles, &now_cycles);
-  last_now_cycles = now_cycles;
-
-  uint64_t estimated_base_ns;
-
-  // ----------
-  // Read the "last_sample" values again; this time holding the write lock.
-  struct TimeSample sample;
-  ReadTimeSampleAtomic(&last_sample, &sample);
-
-  // ----------
-  // Try running the fast path again; another thread may have updated the
-  // sample between our run of the fast path and the sample we just read.
-  uint64_t delta_cycles = now_cycles - sample.base_cycles;
-  if (delta_cycles < sample.min_cycles_per_sample) {
-    // Another thread updated the sample.  This path does not take the seqlock
-    // so that blocked readers can make progress without blocking new readers.
-    estimated_base_ns = sample.base_ns +
-        ((delta_cycles * sample.nsscaled_per_cycle) >> kScale);
-    stats_fast_slow_paths++;
-  } else {
-    estimated_base_ns =
-        UpdateLastSample(now_cycles, now_ns, delta_cycles, &sample);
-  }
-
-  lock.Unlock();
-
-  return estimated_base_ns;
-}
-
-// Main part of the algorithm.  Locks out readers, updates the approximation
-// using the new sample from the kernel, and stores the result in last_sample
-// for readers.  Returns the new estimated time.
-static uint64_t UpdateLastSample(uint64_t now_cycles, uint64_t now_ns,
-                                 uint64_t delta_cycles,
-                                 const struct TimeSample *sample)
-    ABSL_EXCLUSIVE_LOCKS_REQUIRED(lock) {
-  uint64_t estimated_base_ns = now_ns;
-  uint64_t lock_value = SeqAcquire(&seq);  // acquire seqlock to block readers
-
-  // The 5s in the next if-statement limits the time for which we will trust
-  // the cycle counter and our last sample to give a reasonable result.
-  // Errors in the rate of the source clock can be multiplied by the ratio
-  // between this limit and kMinNSBetweenSamples.
-  if (sample->raw_ns == 0 ||  // no recent sample, or clock went backwards
-      sample->raw_ns + static_cast<uint64_t>(5) * 1000 * 1000 * 1000 < now_ns ||
-      now_ns < sample->raw_ns || now_cycles < sample->base_cycles) {
-    // record this sample, and forget any previously known slope.
-    last_sample.raw_ns.store(now_ns, std::memory_order_relaxed);
-    last_sample.base_ns.store(estimated_base_ns, std::memory_order_relaxed);
-    last_sample.base_cycles.store(now_cycles, std::memory_order_relaxed);
-    last_sample.nsscaled_per_cycle.store(0, std::memory_order_relaxed);
-    last_sample.min_cycles_per_sample.store(0, std::memory_order_relaxed);
-    stats_initializations++;
-  } else if (sample->raw_ns + 500 * 1000 * 1000 < now_ns &&
-             sample->base_cycles + 50 < now_cycles) {
-    // Enough time has passed to compute the cycle time.
-    if (sample->nsscaled_per_cycle != 0) {  // Have a cycle time estimate.
-      // Compute time from counter reading, but avoiding overflow
-      // delta_cycles may be larger than on the fast path.
-      uint64_t estimated_scaled_ns;
-      int s = -1;
-      do {
-        s++;
-        estimated_scaled_ns = (delta_cycles >> s) * sample->nsscaled_per_cycle;
-      } while (estimated_scaled_ns / sample->nsscaled_per_cycle !=
-               (delta_cycles >> s));
-      estimated_base_ns = sample->base_ns +
-                          (estimated_scaled_ns >> (kScale - s));
-    }
-
-    // Compute the assumed cycle time kMinNSBetweenSamples ns into the future
-    // assuming the cycle counter rate stays the same as the last interval.
-    uint64_t ns = now_ns - sample->raw_ns;
-    uint64_t measured_nsscaled_per_cycle = SafeDivideAndScale(ns, delta_cycles);
-
-    uint64_t assumed_next_sample_delta_cycles =
-        SafeDivideAndScale(kMinNSBetweenSamples, measured_nsscaled_per_cycle);
-
-    int64_t diff_ns = now_ns - estimated_base_ns;  // estimate low by this much
-
-    // We want to set nsscaled_per_cycle so that our estimate of the ns time
-    // at the assumed cycle time is the assumed ns time.
-    // That is, we want to set nsscaled_per_cycle so:
-    //  kMinNSBetweenSamples + diff_ns  ==
-    //  (assumed_next_sample_delta_cycles * nsscaled_per_cycle) >> kScale
-    // But we wish to damp oscillations, so instead correct only most
-    // of our current error, by solving:
-    //  kMinNSBetweenSamples + diff_ns - (diff_ns / 16) ==
-    //  (assumed_next_sample_delta_cycles * nsscaled_per_cycle) >> kScale
-    ns = kMinNSBetweenSamples + diff_ns - (diff_ns / 16);
-    uint64_t new_nsscaled_per_cycle =
-        SafeDivideAndScale(ns, assumed_next_sample_delta_cycles);
-    if (new_nsscaled_per_cycle != 0 &&
-        diff_ns < 100 * 1000 * 1000 && -diff_ns < 100 * 1000 * 1000) {
-      // record the cycle time measurement
-      last_sample.nsscaled_per_cycle.store(
-          new_nsscaled_per_cycle, std::memory_order_relaxed);
-      uint64_t new_min_cycles_per_sample =
-          SafeDivideAndScale(kMinNSBetweenSamples, new_nsscaled_per_cycle);
-      last_sample.min_cycles_per_sample.store(
-          new_min_cycles_per_sample, std::memory_order_relaxed);
-      stats_calibrations++;
-    } else {  // something went wrong; forget the slope
-      last_sample.nsscaled_per_cycle.store(0, std::memory_order_relaxed);
-      last_sample.min_cycles_per_sample.store(0, std::memory_order_relaxed);
-      estimated_base_ns = now_ns;
-      stats_reinitializations++;
-    }
-    last_sample.raw_ns.store(now_ns, std::memory_order_relaxed);
-    last_sample.base_ns.store(estimated_base_ns, std::memory_order_relaxed);
-    last_sample.base_cycles.store(now_cycles, std::memory_order_relaxed);
-  } else {
-    // have a sample, but no slope; waiting for enough time for a calibration
-    stats_slow_paths++;
-  }
-
-  SeqRelease(&seq, lock_value);  // release the readers
-
-  return estimated_base_ns;
-}
-ABSL_NAMESPACE_END
-}  // namespace absl
-#endif  // ABSL_USE_CYCLECLOCK_FOR_GET_CURRENT_TIME_NANOS
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace {
-
-// Returns the maximum duration that SleepOnce() can sleep for.
-constexpr absl::Duration MaxSleep() {
-#ifdef _WIN32
-  // Windows Sleep() takes unsigned long argument in milliseconds.
-  return absl::Milliseconds(
-      std::numeric_limits<unsigned long>::max());  // NOLINT(runtime/int)
-#else
-  return absl::Seconds(std::numeric_limits<time_t>::max());
-#endif
-}
-
-// Sleeps for the given duration.
-// REQUIRES: to_sleep <= MaxSleep().
-void SleepOnce(absl::Duration to_sleep) {
-#ifdef _WIN32
-  Sleep(to_sleep / absl::Milliseconds(1));
-#else
-  struct timespec sleep_time = absl::ToTimespec(to_sleep);
-  while (nanosleep(&sleep_time, &sleep_time) != 0 && errno == EINTR) {
-    // Ignore signals and wait for the full interval to elapse.
-  }
-#endif
-}
-
-}  // namespace
-ABSL_NAMESPACE_END
-}  // namespace absl
-
-extern "C" {
-
-ABSL_ATTRIBUTE_WEAK void AbslInternalSleepFor(absl::Duration duration) {
-  while (duration > absl::ZeroDuration()) {
-    absl::Duration to_sleep = std::min(duration, absl::MaxSleep());
-    absl::SleepOnce(to_sleep);
-    duration -= to_sleep;
-  }
-}
-
-}  // extern "C"