Split configuration related to cycle clock into separate headers

PiperOrigin-RevId: 477043101
Change-Id: I009ea39ad61e7e78cdac51afc57a8ad5b4d8aa2d

6 files changed, 142 insertions, 57 deletions

diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index bd023ad8..ded26d6a 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel
@@ -114,6 +114,23 @@ cc_library(
 )
 
 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 = [
         "internal/dynamic_annotations.h",
@@ -237,6 +254,7 @@ cc_library(
         ":base_internal",
         ":config",
         ":core_headers",
+        ":cycleclock_internal",
         ":dynamic_annotations",
         ":log_severity",
         ":raw_logging_internal",
diff --git a/absl/base/CMakeLists.txt b/absl/base/CMakeLists.txt
index ed55093a..5c46ba32 100644
--- a/absl/base/CMakeLists.txt
+++ b/absl/base/CMakeLists.txt
@@ -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"
diff --git a/absl/base/internal/cycleclock.h b/absl/base/internal/cycleclock.h
index 9704e388..cbfdf579 100644
--- a/absl/base/internal/cycleclock.h
+++ b/absl/base/internal/cycleclock.h
@@ -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
 
diff --git a/absl/base/internal/cycleclock_config.h b/absl/base/internal/cycleclock_config.h
new file mode 100644
index 00000000..191112b5
--- /dev/null
+++ b/absl/base/internal/cycleclock_config.h
@@ -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_
diff --git a/absl/base/internal/unscaledcycleclock.h b/absl/base/internal/unscaledcycleclock.h
index 74bac8a0..cc1276ba 100644
--- a/absl/base/internal/unscaledcycleclock.h
+++ b/absl/base/internal/unscaledcycleclock.h
@@ -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 {
diff --git a/absl/base/internal/unscaledcycleclock_config.h b/absl/base/internal/unscaledcycleclock_config.h
new file mode 100644
index 00000000..24b324ac
--- /dev/null
+++ b/absl/base/internal/unscaledcycleclock_config.h
@@ -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_