llvm/lib/Analysis/InlineSizeEstimatorAnalysis.cpp

   1 //===- InlineSizeEstimatorAnalysis.cpp - IR to native size from ML model --===//
   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 // This implements feature and label extraction for offline supervised learning
  10 // of a IR to native size model.
  11 //
  12 //===----------------------------------------------------------------------===//
  13 #include "llvm/Analysis/InlineSizeEstimatorAnalysis.h"
  14
  15 #ifdef LLVM_HAVE_TFLITE
  16 #include "llvm/Analysis/Utils/TFUtils.h"
  17 #endif
  18 #include "llvm/IR/Function.h"
  19 #include "llvm/IR/PassManager.h"
  20 #include "llvm/Support/raw_ostream.h"
  21
  22 using namespace llvm;
  23
  24 AnalysisKey InlineSizeEstimatorAnalysis::Key;
  25
  26 #ifdef LLVM_HAVE_TFLITE
  27 #include "llvm/Analysis/LoopInfo.h"
  28 #include "llvm/Analysis/TargetLibraryInfo.h"
  29 #include "llvm/Analysis/TargetTransformInfo.h"
  30 #include "llvm/IR/BasicBlock.h"
  31 #include "llvm/IR/Dominators.h"
  32 #include "llvm/IR/Instructions.h"
  33 #include "llvm/MC/MCAsmLayout.h"
  34 #include "llvm/Support/Casting.h"
  35 #include "llvm/Support/CommandLine.h"
  36 #include <algorithm>
  37 #include <deque>
  38 #include <optional>
  39
  40 cl::opt<std::string> TFIR2NativeModelPath(
  41     "ml-inliner-ir2native-model", cl::Hidden,
  42     cl::desc("Path to saved model evaluating native size from IR."));
  43
  44 #define DEBUG_TYPE "inline-size-estimator"
  45 namespace {
  46 unsigned getMaxInstructionID() {
  47 #define LAST_OTHER_INST(NR) return NR;
  48 #include "llvm/IR/Instruction.def"
  49 }
  50
  51 class IRToNativeSizeLearning {
  52 public:
  53   enum class NamedFeatureIndex : size_t {
  54     InitialSize,
  55     Blocks,
  56     Calls,
  57     IsLocal,
  58     IsLinkOnceODR,
  59     IsLinkOnce,
  60     Loops,
  61     MaxLoopDepth,
  62     MaxDomTreeLevel,
  63
  64     NumNamedFeatures
  65   };
  66   static const size_t NumNamedFeatures =
  67       static_cast<size_t>(NamedFeatureIndex::NumNamedFeatures);
  68   struct FunctionFeatures {
  69     static const size_t FeatureCount;
  70
  71     std::array<int32_t, NumNamedFeatures> NamedFeatures = {0};
  72     std::vector<int32_t> InstructionHistogram;
  73     std::vector<int32_t> InstructionPairHistogram;
  74
  75     void fillTensor(int32_t *Ptr) const;
  76     int32_t &operator[](NamedFeatureIndex Pos) {
  77       return NamedFeatures[static_cast<size_t>(Pos)];
  78     }
  79   };
  80   IRToNativeSizeLearning() = default;
  81
  82   static FunctionFeatures getFunctionFeatures(Function &F,
  83                                               FunctionAnalysisManager &FAM);
  84 };
  85
  86 // This is a point in time - we determined including these pairs of
  87 // consecutive instructions (in the IR layout available at inline time) as
  88 // features improves the model performance. We want to move away from manual
  89 // feature selection.
  90 // The array is given in opcode pairs rather than labels because 1) labels
  91 // weren't readily available, and 2) the successions were hand - extracted.
  92 //
  93 // This array must be sorted.
  94 static const std::array<std::pair<size_t, size_t>, 137>
  95     ImportantInstructionSuccessions{
  96         {{1, 1},   {1, 4},   {1, 5},   {1, 7},   {1, 8},   {1, 9},   {1, 11},
  97          {1, 12},  {1, 13},  {1, 14},  {1, 18},  {1, 20},  {1, 22},  {1, 24},
  98          {1, 25},  {1, 26},  {1, 27},  {1, 28},  {1, 29},  {1, 30},  {1, 31},
  99          {1, 32},  {1, 33},  {1, 34},  {1, 39},  {1, 40},  {1, 42},  {1, 45},
 100          {2, 1},   {2, 2},   {2, 13},  {2, 28},  {2, 29},  {2, 32},  {2, 33},
 101          {2, 34},  {2, 38},  {2, 48},  {2, 49},  {2, 53},  {2, 55},  {2, 56},
 102          {13, 2},  {13, 13}, {13, 26}, {13, 33}, {13, 34}, {13, 56}, {15, 27},
 103          {28, 2},  {28, 48}, {28, 53}, {29, 2},  {29, 33}, {29, 56}, {31, 31},
 104          {31, 33}, {31, 34}, {31, 49}, {32, 1},  {32, 2},  {32, 13}, {32, 15},
 105          {32, 28}, {32, 29}, {32, 32}, {32, 33}, {32, 34}, {32, 39}, {32, 40},
 106          {32, 48}, {32, 49}, {32, 53}, {32, 56}, {33, 1},  {33, 2},  {33, 32},
 107          {33, 33}, {33, 34}, {33, 49}, {33, 53}, {33, 56}, {34, 1},  {34, 2},
 108          {34, 32}, {34, 33}, {34, 34}, {34, 49}, {34, 53}, {34, 56}, {38, 34},
 109          {39, 57}, {40, 34}, {47, 15}, {47, 49}, {48, 2},  {48, 34}, {48, 56},
 110          {49, 1},  {49, 2},  {49, 28}, {49, 32}, {49, 33}, {49, 34}, {49, 39},
 111          {49, 49}, {49, 56}, {53, 1},  {53, 2},  {53, 28}, {53, 34}, {53, 53},
 112          {53, 57}, {55, 1},  {55, 28}, {55, 34}, {55, 53}, {55, 55}, {55, 56},
 113          {56, 1},  {56, 2},  {56, 7},  {56, 13}, {56, 32}, {56, 33}, {56, 34},
 114          {56, 49}, {56, 53}, {56, 56}, {56, 64}, {57, 34}, {57, 56}, {57, 57},
 115          {64, 1},  {64, 64}, {65, 1},  {65, 65}}};
 116
 117 // We have: 9 calculated features (the features here); 1 feature for each
 118 // instruction opcode; and 1 feature for each manually-identified sequence.
 119 // For the latter 2, we build a histogram: we count the number of
 120 // occurrences of each instruction opcode or succession of instructions,
 121 // respectively.
 122 // Note that instruction opcodes start from 1. For convenience, we also have an
 123 // always 0 feature for the '0' opcode, hence the extra 1.
 124 const size_t IRToNativeSizeLearning::FunctionFeatures::FeatureCount =
 125     ImportantInstructionSuccessions.size() + getMaxInstructionID() + 1 +
 126     IRToNativeSizeLearning::NumNamedFeatures;
 127
 128 size_t getSize(Function &F, TargetTransformInfo &TTI) {
 129   size_t Ret = 0;
 130   for (const auto &BB : F)
 131     for (const auto &I : BB)
 132       Ret += *(TTI.getInstructionCost(
 133           &I, TargetTransformInfo::TargetCostKind::TCK_CodeSize).getValue());
 134   return Ret;
 135 }
 136
 137 size_t getSize(Function &F, FunctionAnalysisManager &FAM) {
 138   auto &TTI = FAM.getResult<TargetIRAnalysis>(F);
 139   return getSize(F, TTI);
 140 }
 141
 142 unsigned getMaxDominatorTreeDepth(const Function &F,
 143                                   const DominatorTree &Tree) {
 144   unsigned Ret = 0;
 145   for (const auto &BB : F)
 146     if (const auto *TN = Tree.getNode(&BB))
 147       Ret = std::max(Ret, TN->getLevel());
 148   return Ret;
 149 }
 150 } // namespace
 151
 152 IRToNativeSizeLearning::FunctionFeatures
 153 IRToNativeSizeLearning::getFunctionFeatures(Function &F,
 154                                             FunctionAnalysisManager &FAM) {
 155   assert(llvm::is_sorted(ImportantInstructionSuccessions) &&
 156          "expected function features are sorted");
 157
 158   auto &DomTree = FAM.getResult<DominatorTreeAnalysis>(F);
 159   FunctionFeatures FF;
 160   size_t InstrCount = getMaxInstructionID() + 1;
 161   FF.InstructionHistogram.resize(InstrCount);
 162
 163   FF.InstructionPairHistogram.resize(ImportantInstructionSuccessions.size());
 164
 165   int StartID = 0;
 166   int LastID = StartID;
 167   auto getPairIndex = [](size_t a, size_t b) {
 168     auto I = llvm::find(ImportantInstructionSuccessions, std::make_pair(a, b));
 169     if (I == ImportantInstructionSuccessions.end())
 170       return -1;
 171     return static_cast<int>(
 172         std::distance(ImportantInstructionSuccessions.begin(), I));
 173   };
 174
 175   // We don't want debug calls, because they'd just add noise.
 176   for (const auto &BB : F) {
 177     for (const auto &I : BB.instructionsWithoutDebug()) {
 178       auto ID = I.getOpcode();
 179
 180       ++FF.InstructionHistogram[ID];
 181       int PairIndex = getPairIndex(LastID, ID);
 182       if (PairIndex >= 0)
 183         ++FF.InstructionPairHistogram[PairIndex];
 184       LastID = ID;
 185       if (isa<CallBase>(I))
 186         ++FF[NamedFeatureIndex::Calls];
 187     }
 188   }
 189
 190   FF[NamedFeatureIndex::InitialSize] = getSize(F, FAM);
 191   FF[NamedFeatureIndex::IsLocal] = F.hasLocalLinkage();
 192   FF[NamedFeatureIndex::IsLinkOnceODR] = F.hasLinkOnceODRLinkage();
 193   FF[NamedFeatureIndex::IsLinkOnce] = F.hasLinkOnceLinkage();
 194   FF[NamedFeatureIndex::Blocks] = F.size();
 195   auto &LI = FAM.getResult<LoopAnalysis>(F);
 196   FF[NamedFeatureIndex::Loops] = std::distance(LI.begin(), LI.end());
 197   for (auto &L : LI)
 198     FF[NamedFeatureIndex::MaxLoopDepth] =
 199         std::max(FF[NamedFeatureIndex::MaxLoopDepth],
 200                  static_cast<int32_t>(L->getLoopDepth()));
 201   FF[NamedFeatureIndex::MaxDomTreeLevel] = getMaxDominatorTreeDepth(F, DomTree);
 202   return FF;
 203 }
 204
 205 void IRToNativeSizeLearning::FunctionFeatures::fillTensor(int32_t *Ptr) const {
 206   std::copy(NamedFeatures.begin(), NamedFeatures.end(), Ptr);
 207   Ptr += NamedFeatures.size();
 208   std::copy(InstructionHistogram.begin(), InstructionHistogram.end(), Ptr);
 209   Ptr += InstructionHistogram.size();
 210   std::copy(InstructionPairHistogram.begin(), InstructionPairHistogram.end(),
 211             Ptr);
 212 }
 213
 214 bool InlineSizeEstimatorAnalysis::isEvaluatorRequested() {
 215   return !TFIR2NativeModelPath.empty();
 216 }
 217
 218 InlineSizeEstimatorAnalysis::InlineSizeEstimatorAnalysis() {
 219   if (!isEvaluatorRequested()) {
 220     return;
 221   }
 222   std::vector<TensorSpec> InputSpecs{TensorSpec::createSpec<int32_t>(
 223       "serving_default_input_1",
 224       {1, static_cast<int64_t>(
 225               IRToNativeSizeLearning::FunctionFeatures::FeatureCount)})};
 226   std::vector<TensorSpec> OutputSpecs{
 227       TensorSpec::createSpec<float>("StatefulPartitionedCall", {1})};
 228   Evaluator = std::make_unique<TFModelEvaluator>(
 229       TFIR2NativeModelPath.getValue().c_str(), InputSpecs, OutputSpecs);
 230   if (!Evaluator || !Evaluator->isValid()) {
 231     Evaluator.reset();
 232     return;
 233   }
 234 }
 235
 236 InlineSizeEstimatorAnalysis::Result
 237 InlineSizeEstimatorAnalysis::run(const Function &F,
 238                                  FunctionAnalysisManager &FAM) {
 239   if (!Evaluator)
 240     return std::nullopt;
 241   auto Features = IRToNativeSizeLearning::getFunctionFeatures(
 242       const_cast<Function &>(F), FAM);
 243   int32_t *V = Evaluator->getInput<int32_t>(0);
 244   Features.fillTensor(V);
 245   auto ER = Evaluator->evaluate();
 246   if (!ER)
 247     return std::nullopt;
 248   float Ret = *ER->getTensorValue<float>(0);
 249   if (Ret < 0.0)
 250     Ret = 0.0;
 251   return static_cast<size_t>(Ret);
 252 }
 253
 254 InlineSizeEstimatorAnalysis::~InlineSizeEstimatorAnalysis() {}
 255 InlineSizeEstimatorAnalysis::InlineSizeEstimatorAnalysis(
 256     InlineSizeEstimatorAnalysis &&Other)
 257     : Evaluator(std::move(Other.Evaluator)) {}
 258
 259 #else
 260 namespace llvm {
 261 class TFModelEvaluator {};
 262 } // namespace llvm
 263 InlineSizeEstimatorAnalysis::InlineSizeEstimatorAnalysis() = default;
 264 InlineSizeEstimatorAnalysis ::InlineSizeEstimatorAnalysis(
 265     InlineSizeEstimatorAnalysis &&) {}
 266 InlineSizeEstimatorAnalysis::~InlineSizeEstimatorAnalysis() = default;
 267 InlineSizeEstimatorAnalysis::Result
 268 InlineSizeEstimatorAnalysis::run(const Function &F,
 269                                  FunctionAnalysisManager &FAM) {
 270   return std::nullopt;
 271 }
 272 bool InlineSizeEstimatorAnalysis::isEvaluatorRequested() { return false; }
 273 #endif
 274
 275 PreservedAnalyses
 276 InlineSizeEstimatorAnalysisPrinterPass::run(Function &F,
 277                                             FunctionAnalysisManager &AM) {
 278   OS << "[InlineSizeEstimatorAnalysis] size estimate for " << F.getName()
 279      << ": " << AM.getResult<InlineSizeEstimatorAnalysis>(F) << "\n";
 280   return PreservedAnalyses::all();
 281 }