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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_ANDROID_THREAD_INSTRUCTION_COUNT_H_
#define BASE_ANDROID_THREAD_INSTRUCTION_COUNT_H_
#include <stdint.h>
#include "base/base_export.h"
namespace base {
namespace android {
// Represents the number of instructions that were retired between two samples
// of a thread's performance counters.
class BASE_EXPORT ThreadInstructionDelta {
public:
constexpr ThreadInstructionDelta() : delta_(0) {}
explicit constexpr ThreadInstructionDelta(int64_t delta) : delta_(delta) {}
constexpr int64_t ToInternalValue() const { return delta_; }
private:
int64_t delta_;
};
// Helper class for reading the current count of instructions retired for the
// current thread via ThreadInstructionCount::Now(). Does *not* count
// instructions retired while running in the kernel.
//
// Limitations:
// * Crashes when used in sandboxed process
// * Works on a userdebug build of Android 12, kernel 4.19. May require extra
// effort to allow on later Android releases and kernel versions.
class BASE_EXPORT ThreadInstructionCount {
public:
// Returns true if the platform supports hardware retired instruction
// counters. May crash in sandboxed processes.
static bool IsSupported();
// Returns the number of retired instructions relative to some epoch count,
// or 0 if getting the current instruction count failed / is disabled.
static ThreadInstructionCount Now();
explicit constexpr ThreadInstructionCount(uint64_t value = 0)
: value_(value) {}
constexpr ThreadInstructionDelta operator-(
ThreadInstructionCount other) const {
return ThreadInstructionDelta(static_cast<int64_t>(value_ - other.value_));
}
constexpr uint64_t ToInternalValue() const { return value_; }
private:
uint64_t value_;
};
} // namespace android
} // namespace base
#endif // BASE_ANDROID_THREAD_INSTRUCTION_COUNT_H_
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