tools/llvm-exegesis/lib/BenchmarkRunner.cpp

   1 //===-- BenchmarkRunner.cpp -------------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include <array>
  10 #include <string>
  11
  12 #include "Assembler.h"
  13 #include "BenchmarkRunner.h"
  14 #include "Error.h"
  15 #include "MCInstrDescView.h"
  16 #include "PerfHelper.h"
  17 #include "llvm/ADT/StringExtras.h"
  18 #include "llvm/ADT/StringRef.h"
  19 #include "llvm/ADT/Twine.h"
  20 #include "llvm/Support/CrashRecoveryContext.h"
  21 #include "llvm/Support/FileSystem.h"
  22 #include "llvm/Support/MemoryBuffer.h"
  23 #include "llvm/Support/Program.h"
  24
  25 namespace llvm {
  26 namespace exegesis {
  27
  28 BenchmarkRunner::BenchmarkRunner(const LLVMState &State,
  29                                  InstructionBenchmark::ModeE Mode)
  30     : State(State), Mode(Mode), Scratch(std::make_unique<ScratchSpace>()) {}
  31
  32 BenchmarkRunner::~BenchmarkRunner() = default;
  33
  34 namespace {
  35 class FunctionExecutorImpl : public BenchmarkRunner::FunctionExecutor {
  36 public:
  37   FunctionExecutorImpl(const LLVMState &State,
  38                        object::OwningBinary<object::ObjectFile> Obj,
  39                        BenchmarkRunner::ScratchSpace *Scratch)
  40       : Function(State.createTargetMachine(), std::move(Obj)),
  41         Scratch(Scratch) {}
  42
  43 private:
  44   Expected<int64_t> runAndMeasure(const char *Counters) const override {
  45     // We sum counts when there are several counters for a single ProcRes
  46     // (e.g. P23 on SandyBridge).
  47     int64_t CounterValue = 0;
  48     SmallVector<StringRef, 2> CounterNames;
  49     StringRef(Counters).split(CounterNames, '+');
  50     char *const ScratchPtr = Scratch->ptr();
  51     for (auto &CounterName : CounterNames) {
  52       CounterName = CounterName.trim();
  53       pfm::PerfEvent PerfEvent(CounterName);
  54       if (!PerfEvent.valid())
  55         report_fatal_error(
  56             Twine("invalid perf event '").concat(CounterName).concat("'"));
  57       pfm::Counter Counter(PerfEvent);
  58       Scratch->clear();
  59       {
  60         CrashRecoveryContext CRC;
  61         CrashRecoveryContext::Enable();
  62         const bool Crashed = !CRC.RunSafely([this, &Counter, ScratchPtr]() {
  63           Counter.start();
  64           this->Function(ScratchPtr);
  65           Counter.stop();
  66         });
  67         CrashRecoveryContext::Disable();
  68         // FIXME: Better diagnosis.
  69         if (Crashed)
  70           return make_error<Failure>("snippet crashed while running");
  71       }
  72       CounterValue += Counter.read();
  73     }
  74     return CounterValue;
  75   }
  76
  77   const ExecutableFunction Function;
  78   BenchmarkRunner::ScratchSpace *const Scratch;
  79 };
  80 } // namespace
  81
  82 InstructionBenchmark BenchmarkRunner::runConfiguration(
  83     const BenchmarkCode &BC, unsigned NumRepetitions,
  84     const SnippetRepetitor &Repetitor, bool DumpObjectToDisk) const {
  85   InstructionBenchmark InstrBenchmark;
  86   InstrBenchmark.Mode = Mode;
  87   InstrBenchmark.CpuName = State.getTargetMachine().getTargetCPU();
  88   InstrBenchmark.LLVMTriple =
  89       State.getTargetMachine().getTargetTriple().normalize();
  90   InstrBenchmark.NumRepetitions = NumRepetitions;
  91   InstrBenchmark.Info = BC.Info;
  92
  93   const std::vector<MCInst> &Instructions = BC.Key.Instructions;
  94
  95   InstrBenchmark.Key = BC.Key;
  96
  97   // Assemble at least kMinInstructionsForSnippet instructions by repeating the
  98   // snippet for debug/analysis. This is so that the user clearly understands
  99   // that the inside instructions are repeated.
 100   constexpr const int kMinInstructionsForSnippet = 16;
 101   {
 102     SmallString<0> Buffer;
 103     raw_svector_ostream OS(Buffer);
 104     assembleToStream(State.getExegesisTarget(), State.createTargetMachine(),
 105                      BC.LiveIns, BC.Key.RegisterInitialValues,
 106                      Repetitor.Repeat(Instructions, kMinInstructionsForSnippet),
 107                      OS);
 108     const ExecutableFunction EF(State.createTargetMachine(),
 109                                 getObjectFromBuffer(OS.str()));
 110     const auto FnBytes = EF.getFunctionBytes();
 111     InstrBenchmark.AssembledSnippet.assign(FnBytes.begin(), FnBytes.end());
 112   }
 113
 114   // Assemble NumRepetitions instructions repetitions of the snippet for
 115   // measurements.
 116   const auto Filler =
 117       Repetitor.Repeat(Instructions, InstrBenchmark.NumRepetitions);
 118
 119   object::OwningBinary<object::ObjectFile> ObjectFile;
 120   if (DumpObjectToDisk) {
 121     auto ObjectFilePath = writeObjectFile(BC, Filler);
 122     if (Error E = ObjectFilePath.takeError()) {
 123       InstrBenchmark.Error = toString(std::move(E));
 124       return InstrBenchmark;
 125     }
 126     outs() << "Check generated assembly with: /usr/bin/objdump -d "
 127            << *ObjectFilePath << "\n";
 128     ObjectFile = getObjectFromFile(*ObjectFilePath);
 129   } else {
 130     SmallString<0> Buffer;
 131     raw_svector_ostream OS(Buffer);
 132     assembleToStream(State.getExegesisTarget(), State.createTargetMachine(),
 133                      BC.LiveIns, BC.Key.RegisterInitialValues, Filler, OS);
 134     ObjectFile = getObjectFromBuffer(OS.str());
 135   }
 136
 137   const FunctionExecutorImpl Executor(State, std::move(ObjectFile),
 138                                       Scratch.get());
 139   auto Measurements = runMeasurements(Executor);
 140   if (Error E = Measurements.takeError()) {
 141     InstrBenchmark.Error = toString(std::move(E));
 142     return InstrBenchmark;
 143   }
 144   InstrBenchmark.Measurements = std::move(*Measurements);
 145   assert(InstrBenchmark.NumRepetitions > 0 && "invalid NumRepetitions");
 146   for (BenchmarkMeasure &BM : InstrBenchmark.Measurements) {
 147     // Scale the measurements by instruction.
 148     BM.PerInstructionValue /= InstrBenchmark.NumRepetitions;
 149     // Scale the measurements by snippet.
 150     BM.PerSnippetValue *= static_cast<double>(Instructions.size()) /
 151                           InstrBenchmark.NumRepetitions;
 152   }
 153
 154   return InstrBenchmark;
 155 }
 156
 157 Expected<std::string>
 158 BenchmarkRunner::writeObjectFile(const BenchmarkCode &BC,
 159                                  const FillFunction &FillFunction) const {
 160   int ResultFD = 0;
 161   SmallString<256> ResultPath;
 162   if (Error E = errorCodeToError(
 163           sys::fs::createTemporaryFile("snippet", "o", ResultFD, ResultPath)))
 164     return std::move(E);
 165   raw_fd_ostream OFS(ResultFD, true /*ShouldClose*/);
 166   assembleToStream(State.getExegesisTarget(), State.createTargetMachine(),
 167                    BC.LiveIns, BC.Key.RegisterInitialValues, FillFunction, OFS);
 168   return ResultPath.str();
 169 }
 170
 171 BenchmarkRunner::FunctionExecutor::~FunctionExecutor() {}
 172
 173 } // namespace exegesis
 174 } // namespace llvm