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//===-- Analysis.cpp --------------------------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "Analysis.h"
#include "BenchmarkResult.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/FormatVariadic.h"
#include <unordered_set>
#include <vector>
namespace exegesis {
static const char kCsvSep = ',';
namespace {
enum EscapeTag { kEscapeCsv, kEscapeHtml };
template <EscapeTag Tag>
void writeEscaped(llvm::raw_ostream &OS, const llvm::StringRef S);
template <>
void writeEscaped<kEscapeCsv>(llvm::raw_ostream &OS, const llvm::StringRef S) {
if (std::find(S.begin(), S.end(), kCsvSep) == S.end()) {
OS << S;
} else {
// Needs escaping.
OS << '"';
for (const char C : S) {
if (C == '"')
OS << "\"\"";
else
OS << C;
}
OS << '"';
}
}
template <>
void writeEscaped<kEscapeHtml>(llvm::raw_ostream &OS, const llvm::StringRef S) {
for (const char C : S) {
if (C == '<')
OS << "&lt;";
else if (C == '>')
OS << "&gt;";
else if (C == '&')
OS << "&amp;";
else
OS << C;
}
}
} // namespace
template <EscapeTag Tag>
static void
writeClusterId(llvm::raw_ostream &OS,
const InstructionBenchmarkClustering::ClusterId &CID) {
if (CID.isNoise())
writeEscaped<Tag>(OS, "[noise]");
else if (CID.isError())
writeEscaped<Tag>(OS, "[error]");
else
OS << CID.getId();
}
template <EscapeTag Tag>
static void writeMeasurementValue(llvm::raw_ostream &OS, const double Value) {
writeEscaped<Tag>(OS, llvm::formatv("{0:F}", Value).str());
}
// Prints a row representing an instruction, along with scheduling info and
// point coordinates (measurements).
void Analysis::printInstructionRowCsv(const size_t PointId,
llvm::raw_ostream &OS) const {
const InstructionBenchmark &Point = Clustering_.getPoints()[PointId];
writeClusterId<kEscapeCsv>(OS, Clustering_.getClusterIdForPoint(PointId));
OS << kCsvSep;
writeEscaped<kEscapeCsv>(OS, Point.Key.OpcodeName);
OS << kCsvSep;
writeEscaped<kEscapeCsv>(OS, Point.Key.Config);
OS << kCsvSep;
const auto OpcodeIt = MnemonicToOpcode_.find(Point.Key.OpcodeName);
if (OpcodeIt != MnemonicToOpcode_.end()) {
const unsigned SchedClassId =
InstrInfo_->get(OpcodeIt->second).getSchedClass();
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
const auto &SchedModel = SubtargetInfo_->getSchedModel();
const llvm::MCSchedClassDesc *const SCDesc =
SchedModel.getSchedClassDesc(SchedClassId);
writeEscaped<kEscapeCsv>(OS, SCDesc->Name);
#else
OS << SchedClassId;
#endif
}
// FIXME: Print the sched class once InstructionBenchmark separates key into
// (mnemonic, mode, opaque).
for (const auto &Measurement : Point.Measurements) {
OS << kCsvSep;
writeMeasurementValue<kEscapeCsv>(OS, Measurement.Value);
}
OS << "\n";
}
Analysis::Analysis(const llvm::Target &Target,
const InstructionBenchmarkClustering &Clustering)
: Clustering_(Clustering) {
if (Clustering.getPoints().empty())
return;
InstrInfo_.reset(Target.createMCInstrInfo());
const InstructionBenchmark &FirstPoint = Clustering.getPoints().front();
SubtargetInfo_.reset(Target.createMCSubtargetInfo(FirstPoint.LLVMTriple,
FirstPoint.CpuName, ""));
// Build an index of mnemonic->opcode.
for (int I = 0, E = InstrInfo_->getNumOpcodes(); I < E; ++I)
MnemonicToOpcode_.emplace(InstrInfo_->getName(I), I);
}
template <>
llvm::Error
Analysis::run<Analysis::PrintClusters>(llvm::raw_ostream &OS) const {
if (Clustering_.getPoints().empty())
return llvm::Error::success();
// Write the header.
OS << "cluster_id" << kCsvSep << "opcode_name" << kCsvSep << "config"
<< kCsvSep << "sched_class";
for (const auto &Measurement : Clustering_.getPoints().front().Measurements) {
OS << kCsvSep;
writeEscaped<kEscapeCsv>(OS, Measurement.Key);
}
OS << "\n";
// Write the points.
const auto &Clusters = Clustering_.getValidClusters();
for (size_t I = 0, E = Clusters.size(); I < E; ++I) {
for (const size_t PointId : Clusters[I].PointIndices) {
printInstructionRowCsv(PointId, OS);
}
OS << "\n\n";
}
return llvm::Error::success();
}
std::unordered_map<unsigned, std::vector<size_t>>
Analysis::makePointsPerSchedClass() const {
std::unordered_map<unsigned, std::vector<size_t>> PointsPerSchedClass;
const auto &Points = Clustering_.getPoints();
for (size_t PointId = 0, E = Points.size(); PointId < E; ++PointId) {
const InstructionBenchmark &Point = Points[PointId];
if (!Point.Error.empty())
continue;
const auto OpcodeIt = MnemonicToOpcode_.find(Point.Key.OpcodeName);
if (OpcodeIt == MnemonicToOpcode_.end())
continue;
const unsigned SchedClassId =
InstrInfo_->get(OpcodeIt->second).getSchedClass();
PointsPerSchedClass[SchedClassId].push_back(PointId);
}
return PointsPerSchedClass;
}
void Analysis::printSchedClassClustersHtml(std::vector<size_t> PointIds,
llvm::raw_ostream &OS) const {
assert(!PointIds.empty());
// Sort the points by cluster id so that we can display them grouped by
// cluster.
llvm::sort(PointIds.begin(), PointIds.end(),
[this](const size_t A, const size_t B) {
return Clustering_.getClusterIdForPoint(A) <
Clustering_.getClusterIdForPoint(B);
});
const auto &Points = Clustering_.getPoints();
OS << "<table class=\"sched-class-clusters\">";
OS << "<tr><th>ClusterId</th><th>Opcode/Config</th>";
for (const auto &Measurement : Points[PointIds[0]].Measurements) {
OS << "<th>";
if (Measurement.DebugString.empty())
writeEscaped<kEscapeHtml>(OS, Measurement.Key);
else
writeEscaped<kEscapeHtml>(OS, Measurement.DebugString);
OS << "</th>";
}
OS << "</tr>";
for (size_t I = 0, E = PointIds.size(); I < E;) {
const auto &CurrentClusterId =
Clustering_.getClusterIdForPoint(PointIds[I]);
OS << "<tr><td>";
writeClusterId<kEscapeHtml>(OS, CurrentClusterId);
OS << "</td><td><ul>";
std::vector<BenchmarkMeasureStats> MeasurementStats(
Points[PointIds[I]].Measurements.size());
for (; I < E &&
Clustering_.getClusterIdForPoint(PointIds[I]) == CurrentClusterId;
++I) {
const auto &Point = Points[PointIds[I]];
OS << "<li><span class=\"mono\">";
writeEscaped<kEscapeHtml>(OS, Point.Key.OpcodeName);
OS << "</span> <span class=\"mono\">";
writeEscaped<kEscapeHtml>(OS, Point.Key.Config);
OS << "</span></li>";
for (size_t J = 0, F = Point.Measurements.size(); J < F; ++J) {
MeasurementStats[J].push(Point.Measurements[J]);
}
}
OS << "</ul></td>";
for (const auto &Stats : MeasurementStats) {
OS << "<td class=\"measurement\">";
writeMeasurementValue<kEscapeHtml>(OS, Stats.avg());
OS << "<br><span class=\"minmax\">[";
writeMeasurementValue<kEscapeHtml>(OS, Stats.min());
OS << ";";
writeMeasurementValue<kEscapeHtml>(OS, Stats.max());
OS << "]</span></td>";
}
OS << "</tr>";
}
OS << "</table>";
}
// Return the non-redundant list of WriteProcRes used by the given sched class.
// The scheduling model for LLVM is such that each instruction has a certain
// number of uops which consume resources which are described by WriteProcRes
// entries. Each entry describe how many cycles are spent on a specific ProcRes
// kind.
// For example, an instruction might have 3 uOps, one dispatching on P0
// (ProcResIdx=1) and two on P06 (ProcResIdx = 7).
// Note that LLVM additionally denormalizes resource consumption to include
// usage of super resources by subresources. So in practice if there exists a
// P016 (ProcResIdx=10), then the cycles consumed by P0 are also consumed by
// P06 (ProcResIdx = 7) and P016 (ProcResIdx = 10), and the resources consumed
// by P06 are also consumed by P016. In the figure below, parenthesized cycles
// denote implied usage of superresources by subresources:
// P0 P06 P016
// uOp1 1 (1) (1)
// uOp2 1 (1)
// uOp3 1 (1)
// =============================
// 1 3 3
// Eventually we end up with three entries for the WriteProcRes of the
// instruction:
// {ProcResIdx=1, Cycles=1} // P0
// {ProcResIdx=7, Cycles=3} // P06
// {ProcResIdx=10, Cycles=3} // P016
//
// Note that in this case, P016 does not contribute any cycles, so it would
// be removed by this function.
// FIXME: Move this to MCSubtargetInfo and use it in llvm-mca.
static llvm::SmallVector<llvm::MCWriteProcResEntry, 8>
getNonRedundantWriteProcRes(const llvm::MCSchedClassDesc &SCDesc,
const llvm::MCSubtargetInfo &STI) {
llvm::SmallVector<llvm::MCWriteProcResEntry, 8> Result;
const auto &SM = STI.getSchedModel();
const unsigned NumProcRes = SM.getNumProcResourceKinds();
// This assumes that the ProcResDescs are sorted in topological order, which
// is guaranteed by the tablegen backend.
llvm::SmallVector<float, 32> ProcResUnitUsage(NumProcRes);
for (const auto *WPR = STI.getWriteProcResBegin(&SCDesc),
*const WPREnd = STI.getWriteProcResEnd(&SCDesc);
WPR != WPREnd; ++WPR) {
const llvm::MCProcResourceDesc *const ProcResDesc =
SM.getProcResource(WPR->ProcResourceIdx);
if (ProcResDesc->SubUnitsIdxBegin == nullptr) {
// This is a ProcResUnit.
Result.push_back({WPR->ProcResourceIdx, WPR->Cycles});
ProcResUnitUsage[WPR->ProcResourceIdx] += WPR->Cycles;
} else {
// This is a ProcResGroup. First see if it contributes any cycles or if
// it has cycles just from subunits.
float RemainingCycles = WPR->Cycles;
for (const auto *SubResIdx = ProcResDesc->SubUnitsIdxBegin;
SubResIdx != ProcResDesc->SubUnitsIdxBegin + ProcResDesc->NumUnits;
++SubResIdx) {
RemainingCycles -= ProcResUnitUsage[*SubResIdx];
}
if (RemainingCycles < 0.01f) {
// The ProcResGroup contributes no cycles of its own.
continue;
}
// The ProcResGroup contributes `RemainingCycles` cycles of its own.
Result.push_back({WPR->ProcResourceIdx,
static_cast<uint16_t>(std::round(RemainingCycles))});
// Spread the remaining cycles over all subunits.
for (const auto *SubResIdx = ProcResDesc->SubUnitsIdxBegin;
SubResIdx != ProcResDesc->SubUnitsIdxBegin + ProcResDesc->NumUnits;
++SubResIdx) {
ProcResUnitUsage[*SubResIdx] += RemainingCycles / ProcResDesc->NumUnits;
}
}
}
return Result;
}
void Analysis::printSchedClassDescHtml(const llvm::MCSchedClassDesc &SCDesc,
llvm::raw_ostream &OS) const {
OS << "<table class=\"sched-class-desc\">";
OS << "<tr><th>Valid</th><th>Variant</th><th>uOps</th><th>Latency</"
"th><th>WriteProcRes</th><th title=\"This is the idealized unit "
"resource (port) pressure assuming ideal distribution\">Idealized "
"Resource Pressure</th></tr>";
if (SCDesc.isValid()) {
const auto &SM = SubtargetInfo_->getSchedModel();
OS << "<tr><td>&#10004;</td>";
OS << "<td>" << (SCDesc.isVariant() ? "&#10004;" : "&#10005;") << "</td>";
OS << "<td>" << SCDesc.NumMicroOps << "</td>";
// Latencies.
OS << "<td><ul>";
for (int I = 0, E = SCDesc.NumWriteLatencyEntries; I < E; ++I) {
const auto *const Entry =
SubtargetInfo_->getWriteLatencyEntry(&SCDesc, I);
OS << "<li>" << Entry->Cycles;
if (SCDesc.NumWriteLatencyEntries > 1) {
// Dismabiguate if more than 1 latency.
OS << " (WriteResourceID " << Entry->WriteResourceID << ")";
}
OS << "</li>";
}
OS << "</ul></td>";
// WriteProcRes.
OS << "<td><ul>";
const auto ProcRes = getNonRedundantWriteProcRes(SCDesc, *SubtargetInfo_);
for (const auto &WPR : ProcRes) {
OS << "<li><span class=\"mono\">";
writeEscaped<kEscapeHtml>(OS,
SM.getProcResource(WPR.ProcResourceIdx)->Name);
OS << "</span>: " << WPR.Cycles << "</li>";
}
OS << "</ul></td>";
// Idealized port pressure.
OS << "<td><ul>";
for (const auto &Pressure : computeIdealizedProcResPressure(SM, ProcRes)) {
OS << "<li><span class=\"mono\">";
writeEscaped<kEscapeHtml>(OS, SubtargetInfo_->getSchedModel()
.getProcResource(Pressure.first)
->Name);
OS << "</span>: ";
writeMeasurementValue<kEscapeHtml>(OS, Pressure.second);
OS << "</li>";
}
OS << "</ul></td>";
OS << "</tr>";
} else {
OS << "<tr><td>&#10005;</td><td></td><td></td></tr>";
}
OS << "</table>";
}
static constexpr const char kHtmlHead[] = R"(
<head>
<title>llvm-exegesis Analysis Results</title>
<style>
body {
font-family: sans-serif
}
span.sched-class-name {
font-weight: bold;
font-family: monospace;
}
span.opcode {
font-family: monospace;
}
span.config {
font-family: monospace;
}
div.inconsistency {
margin-top: 50px;
}
table {
margin-left: 50px;
border-collapse: collapse;
}
table, table tr,td,th {
border: 1px solid #444;
}
table ul {
padding-left: 0px;
margin: 0px;
list-style-type: none;
}
table.sched-class-clusters td {
padding-left: 10px;
padding-right: 10px;
padding-top: 10px;
padding-bottom: 10px;
}
table.sched-class-desc td {
padding-left: 10px;
padding-right: 10px;
padding-top: 2px;
padding-bottom: 2px;
}
span.mono {
font-family: monospace;
}
span.minmax {
color: #888;
}
td.measurement {
text-align: center;
}
</style>
</head>
)";
template <>
llvm::Error Analysis::run<Analysis::PrintSchedClassInconsistencies>(
llvm::raw_ostream &OS) const {
// Print the header.
OS << "<!DOCTYPE html><html>" << kHtmlHead << "<body>";
OS << "<h1><span class=\"mono\">llvm-exegesis</span> Analysis Results</h1>";
OS << "<h3>Triple: <span class=\"mono\">";
writeEscaped<kEscapeHtml>(OS, Clustering_.getPoints()[0].LLVMTriple);
OS << "</span></h3><h3>Cpu: <span class=\"mono\">";
writeEscaped<kEscapeHtml>(OS, Clustering_.getPoints()[0].CpuName);
OS << "</span></h3>";
// All the points in a scheduling class should be in the same cluster.
// Print any scheduling class for which this is not the case.
for (const auto &SchedClassAndPoints : makePointsPerSchedClass()) {
std::unordered_set<size_t> ClustersForSchedClass;
for (const size_t PointId : SchedClassAndPoints.second) {
const auto &ClusterId = Clustering_.getClusterIdForPoint(PointId);
if (!ClusterId.isValid())
continue; // Ignore noise and errors.
ClustersForSchedClass.insert(ClusterId.getId());
}
if (ClustersForSchedClass.size() <= 1)
continue; // Nothing weird.
const auto &SchedModel = SubtargetInfo_->getSchedModel();
const llvm::MCSchedClassDesc *const SCDesc =
SchedModel.getSchedClassDesc(SchedClassAndPoints.first);
if (!SCDesc)
continue;
OS << "<div class=\"inconsistency\"><p>Sched Class <span "
"class=\"sched-class-name\">";
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
writeEscaped<kEscapeHtml>(OS, SCDesc->Name);
#else
OS << SchedClassAndPoints.first;
#endif
OS << "</span> contains instructions with distinct performance "
"characteristics, falling into "
<< ClustersForSchedClass.size() << " clusters:</p>";
printSchedClassClustersHtml(SchedClassAndPoints.second, OS);
OS << "<p>llvm data:</p>";
printSchedClassDescHtml(*SCDesc, OS);
OS << "</div>";
}
OS << "</body></html>";
return llvm::Error::success();
}
// Distributes a pressure budget as evenly as possible on the provided subunits
// given the already existing port pressure distribution.
//
// The algorithm is as follows: while there is remaining pressure to
// distribute, find the subunits with minimal pressure, and distribute
// remaining pressure equally up to the pressure of the unit with
// second-to-minimal pressure.
// For example, let's assume we want to distribute 2*P1256
// (Subunits = [P1,P2,P5,P6]), and the starting DensePressure is:
// DensePressure = P0 P1 P2 P3 P4 P5 P6 P7
// 0.1 0.3 0.2 0.0 0.0 0.5 0.5 0.5
// RemainingPressure = 2.0
// We sort the subunits by pressure:
// Subunits = [(P2,p=0.2), (P1,p=0.3), (P5,p=0.5), (P6, p=0.5)]
// We'll first start by the subunits with minimal pressure, which are at
// the beginning of the sorted array. In this example there is one (P2).
// The subunit with second-to-minimal pressure is the next one in the
// array (P1). So we distribute 0.1 pressure to P2, and remove 0.1 cycles
// from the budget.
// Subunits = [(P2,p=0.3), (P1,p=0.3), (P5,p=0.5), (P5,p=0.5)]
// RemainingPressure = 1.9
// We repeat this process: distribute 0.2 pressure on each of the minimal
// P2 and P1, decrease budget by 2*0.2:
// Subunits = [(P2,p=0.5), (P1,p=0.5), (P5,p=0.5), (P5,p=0.5)]
// RemainingPressure = 1.5
// There are no second-to-minimal subunits so we just share the remaining
// budget (1.5 cycles) equally:
// Subunits = [(P2,p=0.875), (P1,p=0.875), (P5,p=0.875), (P5,p=0.875)]
// RemainingPressure = 0.0
// We stop as there is no remaining budget to distribute.
void distributePressure(float RemainingPressure,
llvm::SmallVector<uint16_t, 32> Subunits,
llvm::SmallVector<float, 32> &DensePressure) {
// Find the number of subunits with minimal pressure (they are at the
// front).
llvm::sort(Subunits.begin(), Subunits.end(),
[&DensePressure](const uint16_t A, const uint16_t B) {
return DensePressure[A] < DensePressure[B];
});
const auto getPressureForSubunit = [&DensePressure,
&Subunits](size_t I) -> float & {
return DensePressure[Subunits[I]];
};
size_t NumMinimalSU = 1;
while (NumMinimalSU < Subunits.size() &&
getPressureForSubunit(NumMinimalSU) == getPressureForSubunit(0)) {
++NumMinimalSU;
}
while (RemainingPressure > 0.0f) {
if (NumMinimalSU == Subunits.size()) {
// All units are minimal, just distribute evenly and be done.
for (size_t I = 0; I < NumMinimalSU; ++I) {
getPressureForSubunit(I) += RemainingPressure / NumMinimalSU;
}
return;
}
// Distribute the remaining pressure equally.
const float MinimalPressure = getPressureForSubunit(NumMinimalSU - 1);
const float SecondToMinimalPressure = getPressureForSubunit(NumMinimalSU);
assert(MinimalPressure < SecondToMinimalPressure);
const float Increment = SecondToMinimalPressure - MinimalPressure;
if (RemainingPressure <= NumMinimalSU * Increment) {
// There is not enough remaining pressure.
for (size_t I = 0; I < NumMinimalSU; ++I) {
getPressureForSubunit(I) += RemainingPressure / NumMinimalSU;
}
return;
}
// Bump all minimal pressure subunits to `SecondToMinimalPressure`.
for (size_t I = 0; I < NumMinimalSU; ++I) {
getPressureForSubunit(I) = SecondToMinimalPressure;
RemainingPressure -= SecondToMinimalPressure;
}
while (NumMinimalSU < Subunits.size() &&
getPressureForSubunit(NumMinimalSU) == SecondToMinimalPressure) {
++NumMinimalSU;
}
}
}
std::vector<std::pair<uint16_t, float>> computeIdealizedProcResPressure(
const llvm::MCSchedModel &SM,
llvm::SmallVector<llvm::MCWriteProcResEntry, 8> WPRS) {
// DensePressure[I] is the port pressure for Proc Resource I.
llvm::SmallVector<float, 32> DensePressure(SM.getNumProcResourceKinds());
llvm::sort(WPRS.begin(), WPRS.end(),
[](const llvm::MCWriteProcResEntry &A,
const llvm::MCWriteProcResEntry &B) {
return A.ProcResourceIdx < B.ProcResourceIdx;
});
for (const llvm::MCWriteProcResEntry &WPR : WPRS) {
// Get units for the entry.
const llvm::MCProcResourceDesc *const ProcResDesc =
SM.getProcResource(WPR.ProcResourceIdx);
if (ProcResDesc->SubUnitsIdxBegin == nullptr) {
// This is a ProcResUnit.
DensePressure[WPR.ProcResourceIdx] += WPR.Cycles;
} else {
// This is a ProcResGroup.
llvm::SmallVector<uint16_t, 32> Subunits(ProcResDesc->SubUnitsIdxBegin,
ProcResDesc->SubUnitsIdxBegin +
ProcResDesc->NumUnits);
distributePressure(WPR.Cycles, Subunits, DensePressure);
}
}
// Turn dense pressure into sparse pressure by removing zero entries.
std::vector<std::pair<uint16_t, float>> Pressure;
for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) {
if (DensePressure[I] > 0.0f)
Pressure.emplace_back(I, DensePressure[I]);
}
return Pressure;
}
} // namespace exegesis