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Split configuration related to cycle clock into separate headers

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PiperOrigin-RevId: 477043101
Change-Id: I009ea39ad61e7e78cdac51afc57a8ad5b4d8aa2d
This commit is contained in:
Abseil Team
2022-09-26 18:43:11 -07:00
committed by Copybara-Service
parent 1cd889767e
commit df19c20996
7 changed files with 144 additions and 57 deletions
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2
CMake/AbseilDll.cmake
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@@ -13,6 +13,7 @@ set(ABSL_INTERNAL_DLL_FILES
"base/internal/atomic_hook.h"
"base/internal/cycleclock.cc"
"base/internal/cycleclock.h"
"base/internal/cycleclock_config.h"
"base/internal/direct_mmap.h"
"base/internal/dynamic_annotations.h"
"base/internal/endian.h"
@@ -50,6 +51,7 @@ set(ABSL_INTERNAL_DLL_FILES
"base/internal/unaligned_access.h"
"base/internal/unscaledcycleclock.cc"
"base/internal/unscaledcycleclock.h"
"base/internal/unscaledcycleclock_config.h"
"base/log_severity.cc"
"base/log_severity.h"
"base/macros.h"

18
absl/base/BUILD.bazel
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@@ -113,6 +113,23 @@ cc_library(
linkopts = ABSL_DEFAULT_LINKOPTS,
)
cc_library(
name = "cycleclock_internal",
hdrs = [
"internal/cycleclock_config.h",
"internal/unscaledcycleclock_config.h",
],
copts = ABSL_DEFAULT_COPTS,
linkopts = ABSL_DEFAULT_LINKOPTS,
visibility = [
"//absl:__subpackages__",
],
deps = [
":base_internal",
":config",
],
)
cc_library(
name = "dynamic_annotations",
srcs = [
@@ -237,6 +254,7 @@ cc_library(
":base_internal",
":config",
":core_headers",
":cycleclock_internal",
":dynamic_annotations",
":log_severity",
":raw_logging_internal",

2
absl/base/CMakeLists.txt
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@@ -181,6 +181,7 @@ absl_cc_library(
"call_once.h"
"casts.h"
"internal/cycleclock.h"
"internal/cycleclock_config.h"
"internal/low_level_scheduling.h"
"internal/per_thread_tls.h"
"internal/spinlock.h"
@@ -188,6 +189,7 @@ absl_cc_library(
"internal/thread_identity.h"
"internal/tsan_mutex_interface.h"
"internal/unscaledcycleclock.h"
"internal/unscaledcycleclock_config.h"
SRCS
"internal/cycleclock.cc"
"internal/spinlock.cc"

21
absl/base/internal/cycleclock.h
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@@ -47,6 +47,7 @@
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/internal/cycleclock_config.h"
#include "absl/base/internal/unscaledcycleclock.h"
namespace absl {
@@ -76,25 +77,9 @@ class CycleClock {
#if ABSL_USE_UNSCALED_CYCLECLOCK
static CycleClockSourceFunc LoadCycleClockSource();
#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 // NDEBUG
// In debug mode use a different shift to discourage depending on a
// particular shift value.
static constexpr int32_t kShift = 2;
#endif // NDEBUG
static constexpr int32_t kShift = kCycleClockShift;
static constexpr double kFrequencyScale = kCycleClockFrequencyScale;
static constexpr double kFrequencyScale = 1.0 / (1 << kShift);
ABSL_CONST_INIT static std::atomic<CycleClockSourceFunc> cycle_clock_source_;
#endif // ABSL_USE_UNSCALED_CYCLECLOC

55
absl/base/internal/cycleclock_config.h Normal file
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@@ -0,0 +1,55 @@
// 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.
#ifndef ABSL_BASE_INTERNAL_CYCLECLOCK_CONFIG_H_
#define ABSL_BASE_INTERNAL_CYCLECLOCK_CONFIG_H_
#include <cstdint>
#include "absl/base/config.h"
#include "absl/base/internal/inline_variable.h"
#include "absl/base/internal/unscaledcycleclock_config.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace base_internal {
#if ABSL_USE_UNSCALED_CYCLECLOCK
#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.
ABSL_INTERNAL_INLINE_CONSTEXPR(int32_t, kCycleClockShift, 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.
ABSL_INTERNAL_INLINE_CONSTEXPR(int32_t, kCycleClockShift, 0);
#endif
#else // NDEBUG
// In debug mode use a different shift to discourage depending on a
// particular shift value.
ABSL_INTERNAL_INLINE_CONSTEXPR(int32_t, kCycleClockShift, 2);
#endif // NDEBUG
ABSL_INTERNAL_INLINE_CONSTEXPR(double, kCycleClockFrequencyScale,
1.0 / (1 << kCycleClockShift));
#endif // ABSL_USE_UNSCALED_CYCLECLOC
} // namespace base_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_BASE_INTERNAL_CYCLECLOCK_CONFIG_H_

41
absl/base/internal/unscaledcycleclock.h
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@@ -42,48 +42,11 @@
#include <TargetConditionals.h>
#endif
#include "absl/base/port.h"
// The following platforms have an implementation of a hardware counter.
#if defined(__i386__) || defined(__x86_64__) || defined(__aarch64__) || \
defined(__powerpc__) || defined(__ppc__) || defined(__riscv) || \
defined(_M_IX86) || (defined(_M_X64) && !defined(_M_ARM64EC))
#define ABSL_HAVE_UNSCALED_CYCLECLOCK_IMPLEMENTATION 1
#else
#define ABSL_HAVE_UNSCALED_CYCLECLOCK_IMPLEMENTATION 0
#endif
// The following platforms often disable access to the hardware
// counter (through a sandbox) even if the underlying hardware has a
// usable counter. The CycleTimer interface also requires a *scaled*
// CycleClock that runs at atleast 1 MHz. We've found some Android
// ARM64 devices where this is not the case, so we disable it by
// default on Android ARM64.
#if defined(__native_client__) || (defined(__APPLE__)) || \
(defined(__ANDROID__) && defined(__aarch64__))
#define ABSL_USE_UNSCALED_CYCLECLOCK_DEFAULT 0
#else
#define ABSL_USE_UNSCALED_CYCLECLOCK_DEFAULT 1
#endif
// UnscaledCycleClock is an optional internal feature.
// Use "#if ABSL_USE_UNSCALED_CYCLECLOCK" to test for its presence.
// Can be overridden at compile-time via -DABSL_USE_UNSCALED_CYCLECLOCK=0|1
#if !defined(ABSL_USE_UNSCALED_CYCLECLOCK)
#define ABSL_USE_UNSCALED_CYCLECLOCK \
(ABSL_HAVE_UNSCALED_CYCLECLOCK_IMPLEMENTATION && \
ABSL_USE_UNSCALED_CYCLECLOCK_DEFAULT)
#endif
#include "absl/base/config.h"
#include "absl/base/internal/unscaledcycleclock_config.h"
#if ABSL_USE_UNSCALED_CYCLECLOCK
// This macro can be used to test if UnscaledCycleClock::Frequency()
// is NominalCPUFrequency() on a particular platform.
#if (defined(__i386__) || defined(__x86_64__) || defined(__riscv) || \
defined(_M_IX86) || defined(_M_X64))
#define ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY
#endif
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace time_internal {

62
absl/base/internal/unscaledcycleclock_config.h Normal file
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@@ -0,0 +1,62 @@
// 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.
#ifndef ABSL_BASE_INTERNAL_UNSCALEDCYCLECLOCK_CONFIG_H_
#define ABSL_BASE_INTERNAL_UNSCALEDCYCLECLOCK_CONFIG_H_
#if defined(__APPLE__)
#include <TargetConditionals.h>
#endif
// The following platforms have an implementation of a hardware counter.
#if defined(__i386__) || defined(__x86_64__) || defined(__aarch64__) || \
defined(__powerpc__) || defined(__ppc__) || defined(__riscv) || \
defined(_M_IX86) || (defined(_M_X64) && !defined(_M_ARM64EC))
#define ABSL_HAVE_UNSCALED_CYCLECLOCK_IMPLEMENTATION 1
#else
#define ABSL_HAVE_UNSCALED_CYCLECLOCK_IMPLEMENTATION 0
#endif
// The following platforms often disable access to the hardware
// counter (through a sandbox) even if the underlying hardware has a
// usable counter. The CycleTimer interface also requires a *scaled*
// CycleClock that runs at atleast 1 MHz. We've found some Android
// ARM64 devices where this is not the case, so we disable it by
// default on Android ARM64.
#if defined(__native_client__) || (defined(__APPLE__)) || \
(defined(__ANDROID__) && defined(__aarch64__))
#define ABSL_USE_UNSCALED_CYCLECLOCK_DEFAULT 0
#else
#define ABSL_USE_UNSCALED_CYCLECLOCK_DEFAULT 1
#endif
// UnscaledCycleClock is an optional internal feature.
// Use "#if ABSL_USE_UNSCALED_CYCLECLOCK" to test for its presence.
// Can be overridden at compile-time via -DABSL_USE_UNSCALED_CYCLECLOCK=0|1
#if !defined(ABSL_USE_UNSCALED_CYCLECLOCK)
#define ABSL_USE_UNSCALED_CYCLECLOCK \
(ABSL_HAVE_UNSCALED_CYCLECLOCK_IMPLEMENTATION && \
ABSL_USE_UNSCALED_CYCLECLOCK_DEFAULT)
#endif
#if ABSL_USE_UNSCALED_CYCLECLOCK
// This macro can be used to test if UnscaledCycleClock::Frequency()
// is NominalCPUFrequency() on a particular platform.
#if (defined(__i386__) || defined(__x86_64__) || defined(__riscv) || \
defined(_M_IX86) || defined(_M_X64))
#define ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY
#endif
#endif
#endif // ABSL_BASE_INTERNAL_UNSCALEDCYCLECLOCK_CONFIG_H_