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//===-- PerfHelper.h ------------------------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
/// \file
/// Helpers for measuring perf events.
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Config/config.h"
#include "llvm/Support/Error.h"
#include <cstdint>
#include <functional>
#include <memory>
struct perf_event_attr;
namespace llvm {
namespace exegesis {
namespace pfm {
// Returns true on error.
bool pfmInitialize();
void pfmTerminate();
// Retrieves the encoding for the event described by pfm_event_string.
// NOTE: pfm_initialize() must be called before creating PerfEvent objects.
class PerfEvent {
// Dummy event that does not require access to counters (for tests).
static const char *const DummyEventString;
// Events are expressed as strings. e.g. "INSTRUCTION_RETIRED"
explicit PerfEvent(StringRef PfmEventString);
PerfEvent(const PerfEvent &) = delete;
PerfEvent(PerfEvent &&other);
// The pfm_event_string passed at construction time.
StringRef name() const;
// Whether the event was successfully created.
bool valid() const;
// The encoded event to be passed to the Kernel.
const perf_event_attr *attribute() const;
// The fully qualified name for the event.
// e.g. "snb_ep::INSTRUCTION_RETIRED:e=0:i=0:c=0:t=0:u=1:k=0:mg=0:mh=1"
StringRef getPfmEventString() const;
PerfEvent() = default;
std::string EventString;
std::string FullQualifiedEventString;
perf_event_attr *Attr;
void initRealEvent(StringRef PfmEventString);
// Uses a valid PerfEvent to configure the Kernel so we can measure the
// underlying event.
class Counter {
// event: the PerfEvent to measure.
explicit Counter(PerfEvent &&event);
Counter(const Counter &) = delete;
Counter(Counter &&other) = default;
virtual ~Counter();
/// Starts the measurement of the event.
virtual void start();
/// Stops the measurement of the event.
void stop();
/// Returns the current value of the counter or -1 if it cannot be read.
int64_t read() const;
/// Returns the current value of the counter or error if it cannot be read.
/// FunctionBytes: The benchmark function being executed.
/// This is used to filter out the measurements to ensure they are only
/// within the benchmarked code.
/// If empty (or not specified), then no filtering will be done.
/// Not all counters choose to use this.
virtual llvm::Expected<llvm::SmallVector<int64_t, 4>>
readOrError(StringRef FunctionBytes = StringRef()) const;
virtual int numValues() const;
PerfEvent Event;
int FileDescriptor = -1;
bool IsDummyEvent;
void initRealEvent(const PerfEvent &E);
} // namespace pfm
} // namespace exegesis
} // namespace llvm