112 lines
3.1 KiB
C++
112 lines
3.1 KiB
C++
//===-- PerfHelper.h ------------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// Helpers for measuring perf events.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
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#define LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Config/config.h"
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#include "llvm/Support/Error.h"
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#include <cstdint>
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#include <functional>
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#include <memory>
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struct perf_event_attr;
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namespace llvm {
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namespace exegesis {
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namespace pfm {
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// Returns true on error.
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bool pfmInitialize();
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void pfmTerminate();
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// Retrieves the encoding for the event described by pfm_event_string.
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// NOTE: pfm_initialize() must be called before creating PerfEvent objects.
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class PerfEvent {
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public:
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// http://perfmon2.sourceforge.net/manv4/libpfm.html
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// Events are expressed as strings. e.g. "INSTRUCTION_RETIRED"
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explicit PerfEvent(StringRef PfmEventString);
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PerfEvent(const PerfEvent &) = delete;
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PerfEvent(PerfEvent &&other);
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~PerfEvent();
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// The pfm_event_string passed at construction time.
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StringRef name() const;
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// Whether the event was successfully created.
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bool valid() const;
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// The encoded event to be passed to the Kernel.
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const perf_event_attr *attribute() const;
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// The fully qualified name for the event.
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// e.g. "snb_ep::INSTRUCTION_RETIRED:e=0:i=0:c=0:t=0:u=1:k=0:mg=0:mh=1"
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StringRef getPfmEventString() const;
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protected:
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PerfEvent() = default;
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std::string EventString;
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std::string FullQualifiedEventString;
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perf_event_attr *Attr;
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};
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// Uses a valid PerfEvent to configure the Kernel so we can measure the
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// underlying event.
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class Counter {
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public:
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// event: the PerfEvent to measure.
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explicit Counter(PerfEvent &&event);
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Counter(const Counter &) = delete;
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Counter(Counter &&other) = default;
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virtual ~Counter();
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/// Starts the measurement of the event.
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virtual void start();
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/// Stops the measurement of the event.
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void stop();
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/// Returns the current value of the counter or -1 if it cannot be read.
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int64_t read() const;
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/// Returns the current value of the counter or error if it cannot be read.
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/// FunctionBytes: The benchmark function being executed.
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/// This is used to filter out the measurements to ensure they are only
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/// within the benchmarked code.
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/// If empty (or not specified), then no filtering will be done.
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/// Not all counters choose to use this.
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virtual llvm::Expected<llvm::SmallVector<int64_t, 4>>
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readOrError(StringRef FunctionBytes = StringRef()) const;
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virtual int numValues() const;
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protected:
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PerfEvent Event;
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#ifdef HAVE_LIBPFM
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int FileDescriptor = -1;
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#endif
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};
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} // namespace pfm
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} // namespace exegesis
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} // namespace llvm
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#endif // LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
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