llvm/tools/llvm-exegesis/lib/BenchmarkRunner.h

//===-- BenchmarkRunner.h ---------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// Defines the abstract BenchmarkRunner class for measuring a certain execution
/// property of instructions (e.g. latency).
///
//===----------------------------------------------------------------------===//

#ifndef LLVM_TOOLS_LLVM_EXEGESIS_BENCHMARKRUNNER_H
#define LLVM_TOOLS_LLVM_EXEGESIS_BENCHMARKRUNNER_H

#include "Assembler.h"
#include "BenchmarkCode.h"
#include "BenchmarkResult.h"
#include "LlvmState.h"
#include "MCInstrDescView.h"
#include "llvm/MC/MCInst.h"
#include "llvm/Support/Error.h"
#include <cstdlib>
#include <memory>
#include <vector>

namespace llvm {
namespace exegesis {

// A class representing failures that happened during Benchmark, they are used
// to report informations to the user.
class BenchmarkFailure : public llvm::StringError {
public:
  BenchmarkFailure(const llvm::Twine &S);
};

// Common code for all benchmark modes.
class BenchmarkRunner {
public:
  explicit BenchmarkRunner(const LLVMState &State,
                           InstructionBenchmark::ModeE Mode);

  virtual ~BenchmarkRunner();

  InstructionBenchmark runConfiguration(const BenchmarkCode &Configuration,
                                        unsigned NumRepetitions,
                                        bool DumpObjectToDisk) const;

  // Scratch space to run instructions that touch memory.
  struct ScratchSpace {
    static constexpr const size_t kAlignment = 1024;
    static constexpr const size_t kSize = 1 << 20; // 1MB.
    ScratchSpace()
        : UnalignedPtr(std::make_unique<char[]>(kSize + kAlignment)),
          AlignedPtr(
              UnalignedPtr.get() + kAlignment -
              (reinterpret_cast<intptr_t>(UnalignedPtr.get()) % kAlignment)) {}
    char *ptr() const { return AlignedPtr; }
    void clear() { std::memset(ptr(), 0, kSize); }

  private:
    const std::unique_ptr<char[]> UnalignedPtr;
    char *const AlignedPtr;
  };

  // A helper to measure counters while executing a function in a sandboxed
  // context.
  class FunctionExecutor {
  public:
    virtual ~FunctionExecutor();
    virtual llvm::Expected<int64_t>
    runAndMeasure(const char *Counters) const = 0;
  };

protected:
  const LLVMState &State;
  const InstructionBenchmark::ModeE Mode;

private:
  virtual llvm::Expected<std::vector<BenchmarkMeasure>>
  runMeasurements(const FunctionExecutor &Executor) const = 0;

  llvm::Expected<std::string>
  writeObjectFile(const BenchmarkCode &Configuration,
                  llvm::ArrayRef<llvm::MCInst> Code) const;

  const std::unique_ptr<ScratchSpace> Scratch;
};

} // namespace exegesis
} // namespace llvm

#endif // LLVM_TOOLS_LLVM_EXEGESIS_BENCHMARKRUNNER_H