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-rw-r--r--absl/base/internal/cycleclock.cc54
1 files changed, 12 insertions, 42 deletions
diff --git a/absl/base/internal/cycleclock.cc b/absl/base/internal/cycleclock.cc
index 0e65005b..902e3f5e 100644
--- a/absl/base/internal/cycleclock.cc
+++ b/absl/base/internal/cycleclock.cc
@@ -25,6 +25,8 @@
#include <atomic>
#include <chrono> // NOLINT(build/c++11)
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
#include "absl/base/internal/unscaledcycleclock.h"
namespace absl {
@@ -33,44 +35,20 @@ namespace base_internal {
#if ABSL_USE_UNSCALED_CYCLECLOCK
-namespace {
-
-#ifdef NDEBUG
-#ifdef ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY
-// Not debug mode and the UnscaledCycleClock frequency is the CPU
-// frequency. Scale the CycleClock to prevent overflow if someone
-// tries to represent the time as cycles since the Unix epoch.
-static constexpr int32_t kShift = 1;
-#else
-// Not debug mode and the UnscaledCycleClock isn't operating at the
-// raw CPU frequency. There is no need to do any scaling, so don't
-// needlessly sacrifice precision.
-static constexpr int32_t kShift = 0;
-#endif
-#else
-// In debug mode use a different shift to discourage depending on a
-// particular shift value.
-static constexpr int32_t kShift = 2;
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr int32_t CycleClock::kShift;
+constexpr double CycleClock::kFrequencyScale;
#endif
-static constexpr double kFrequencyScale = 1.0 / (1 << kShift);
-static std::atomic<CycleClockSourceFunc> cycle_clock_source;
+ABSL_CONST_INIT std::atomic<CycleClockSourceFunc>
+ CycleClock::cycle_clock_source_{nullptr};
-CycleClockSourceFunc LoadCycleClockSource() {
- // Optimize for the common case (no callback) by first doing a relaxed load;
- // this is significantly faster on non-x86 platforms.
- if (cycle_clock_source.load(std::memory_order_relaxed) == nullptr) {
- return nullptr;
- }
- // This corresponds to the store(std::memory_order_release) in
- // CycleClockSource::Register, and makes sure that any updates made prior to
- // registering the callback are visible to this thread before the callback is
- // invoked.
- return cycle_clock_source.load(std::memory_order_acquire);
+void CycleClockSource::Register(CycleClockSourceFunc source) {
+ // Corresponds to the load(std::memory_order_acquire) in LoadCycleClockSource.
+ CycleClock::cycle_clock_source_.store(source, std::memory_order_release);
}
-} // namespace
-
+#ifdef _WIN32
int64_t CycleClock::Now() {
auto fn = LoadCycleClockSource();
if (fn == nullptr) {
@@ -78,15 +56,7 @@ int64_t CycleClock::Now() {
}
return fn() >> kShift;
}
-
-double CycleClock::Frequency() {
- return kFrequencyScale * base_internal::UnscaledCycleClock::Frequency();
-}
-
-void CycleClockSource::Register(CycleClockSourceFunc source) {
- // Corresponds to the load(std::memory_order_acquire) in LoadCycleClockSource.
- cycle_clock_source.store(source, std::memory_order_release);
-}
+#endif
#else