tools/llvm-mca/Views/SummaryView.cpp

//===--------------------- SummaryView.cpp -------------------*- 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
///
/// This file implements the functionalities used by the SummaryView to print
/// the report information.
///
//===----------------------------------------------------------------------===//

#include "Views/SummaryView.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/MCA/Support.h"
#include "llvm/Support/Format.h"

namespace llvm {
namespace mca {

#define DEBUG_TYPE "llvm-mca"

SummaryView::SummaryView(const MCSchedModel &Model, ArrayRef<MCInst> S,
                         unsigned Width, bool EmitBottleneckAnalysis)
    : SM(Model), Source(S), DispatchWidth(Width?Width: Model.IssueWidth),
      LastInstructionIdx(0),
      TotalCycles(0), NumMicroOps(0), BPI({0, 0, 0, 0, 0}),
      ResourcePressureDistribution(Model.getNumProcResourceKinds(), 0),
      ProcResourceUsage(Model.getNumProcResourceKinds(), 0),
      ProcResourceMasks(Model.getNumProcResourceKinds()),
      ResIdx2ProcResID(Model.getNumProcResourceKinds(), 0),
      PressureIncreasedBecauseOfResources(false),
      PressureIncreasedBecauseOfDataDependencies(false),
      SeenStallCycles(false),
      ShouldEmitBottleneckAnalysis(EmitBottleneckAnalysis) {
  computeProcResourceMasks(SM, ProcResourceMasks);
  for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
    unsigned Index = getResourceStateIndex(ProcResourceMasks[I]);
    ResIdx2ProcResID[Index] = I;
  }
}

void SummaryView::onEvent(const HWInstructionEvent &Event) {
  if (Event.Type == HWInstructionEvent::Dispatched)
    LastInstructionIdx = Event.IR.getSourceIndex();

  // We are only interested in the "instruction retired" events generated by
  // the retire stage for instructions that are part of iteration #0.
  if (Event.Type != HWInstructionEvent::Retired ||
      Event.IR.getSourceIndex() >= Source.size())
    return;

  // Update the cumulative number of resource cycles based on the processor
  // resource usage information available from the instruction descriptor. We
  // need to compute the cumulative number of resource cycles for every
  // processor resource which is consumed by an instruction of the block.
  const Instruction &Inst = *Event.IR.getInstruction();
  const InstrDesc &Desc = Inst.getDesc();
  NumMicroOps += Desc.NumMicroOps;
  for (const std::pair<uint64_t, const ResourceUsage> &RU : Desc.Resources) {
    if (RU.second.size()) {
      unsigned ProcResID = ResIdx2ProcResID[getResourceStateIndex(RU.first)];
      ProcResourceUsage[ProcResID] += RU.second.size();
    }
  }
}

void SummaryView::onEvent(const HWPressureEvent &Event) {
  assert(Event.Reason != HWPressureEvent::INVALID &&
         "Unexpected invalid event!");

  switch (Event.Reason) {
  default:
    break;

  case HWPressureEvent::RESOURCES: {
    PressureIncreasedBecauseOfResources = true;
    ++BPI.ResourcePressureCycles;
    uint64_t ResourceMask = Event.ResourceMask;
    while (ResourceMask) {
      uint64_t Current = ResourceMask & (-ResourceMask);
      unsigned Index = getResourceStateIndex(Current);
      unsigned ProcResID = ResIdx2ProcResID[Index];
      const MCProcResourceDesc &PRDesc = *SM.getProcResource(ProcResID);
      if (!PRDesc.SubUnitsIdxBegin) {
        ResourcePressureDistribution[Index]++;
        ResourceMask ^= Current;
        continue;
      }

      for (unsigned I = 0, E = PRDesc.NumUnits; I < E; ++I) {
        unsigned OtherProcResID = PRDesc.SubUnitsIdxBegin[I];
        unsigned OtherMask = ProcResourceMasks[OtherProcResID];
        ResourcePressureDistribution[getResourceStateIndex(OtherMask)]++;
      }

      ResourceMask ^= Current;
    }
  }

  break;
  case HWPressureEvent::REGISTER_DEPS:
    PressureIncreasedBecauseOfDataDependencies = true;
    ++BPI.RegisterDependencyCycles;
    break;
  case HWPressureEvent::MEMORY_DEPS:
    PressureIncreasedBecauseOfDataDependencies = true;
    ++BPI.MemoryDependencyCycles;
    break;
  }
}

void SummaryView::printBottleneckHints(raw_ostream &OS) const {
  if (!SeenStallCycles || !BPI.PressureIncreaseCycles) {
    OS << "\nNo resource or data dependency bottlenecks discovered.\n";
    return;
  }

  double PressurePerCycle =
      (double)BPI.PressureIncreaseCycles * 100 / TotalCycles;
  double ResourcePressurePerCycle =
      (double)BPI.ResourcePressureCycles * 100 / TotalCycles;
  double DDPerCycle = (double)BPI.DataDependencyCycles * 100 / TotalCycles;
  double RegDepPressurePerCycle =
      (double)BPI.RegisterDependencyCycles * 100 / TotalCycles;
  double MemDepPressurePerCycle =
      (double)BPI.MemoryDependencyCycles * 100 / TotalCycles;

  OS << "\nCycles with backend pressure increase [ "
     << format("%.2f", floor((PressurePerCycle * 100) + 0.5) / 100) << "% ]";

  OS << "\nThroughput Bottlenecks: "
     << "\n  Resource Pressure       [ "
     << format("%.2f", floor((ResourcePressurePerCycle * 100) + 0.5) / 100)
     << "% ]";

  if (BPI.PressureIncreaseCycles) {
    for (unsigned I = 0, E = ResourcePressureDistribution.size(); I < E; ++I) {
      if (ResourcePressureDistribution[I]) {
        double Frequency =
            (double)ResourcePressureDistribution[I] * 100 / TotalCycles;
        unsigned Index = ResIdx2ProcResID[getResourceStateIndex(1ULL << I)];
        const MCProcResourceDesc &PRDesc = *SM.getProcResource(Index);
        OS << "\n  - " << PRDesc.Name << "  [ "
           << format("%.2f", floor((Frequency * 100) + 0.5) / 100) << "% ]";
      }
    }
  }

  OS << "\n  Data Dependencies:      [ "
     << format("%.2f", floor((DDPerCycle * 100) + 0.5) / 100) << "% ]";

  OS << "\n  - Register Dependencies [ "
     << format("%.2f", floor((RegDepPressurePerCycle * 100) + 0.5) / 100)
     << "% ]";

  OS << "\n  - Memory Dependencies   [ "
     << format("%.2f", floor((MemDepPressurePerCycle * 100) + 0.5) / 100)
     << "% ]\n\n";
}

void SummaryView::printView(raw_ostream &OS) const {
  unsigned Instructions = Source.size();
  unsigned Iterations = (LastInstructionIdx / Instructions) + 1;
  unsigned TotalInstructions = Instructions * Iterations;
  unsigned TotalUOps = NumMicroOps * Iterations;
  double IPC = (double)TotalInstructions / TotalCycles;
  double UOpsPerCycle = (double)TotalUOps / TotalCycles;
  double BlockRThroughput = computeBlockRThroughput(
      SM, DispatchWidth, NumMicroOps, ProcResourceUsage);

  std::string Buffer;
  raw_string_ostream TempStream(Buffer);
  TempStream << "Iterations:        " << Iterations;
  TempStream << "\nInstructions:      " << TotalInstructions;
  TempStream << "\nTotal Cycles:      " << TotalCycles;
  TempStream << "\nTotal uOps:        " << TotalUOps << '\n';
  TempStream << "\nDispatch Width:    " << DispatchWidth;
  TempStream << "\nuOps Per Cycle:    "
             << format("%.2f", floor((UOpsPerCycle * 100) + 0.5) / 100);
  TempStream << "\nIPC:               "
             << format("%.2f", floor((IPC * 100) + 0.5) / 100);
  TempStream << "\nBlock RThroughput: "
             << format("%.1f", floor((BlockRThroughput * 10) + 0.5) / 10)
             << '\n';
  if (ShouldEmitBottleneckAnalysis)
    printBottleneckHints(TempStream);
  TempStream.flush();
  OS << Buffer;
}
} // namespace mca.
} // namespace llvm