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1 //===-- IndirectCallPromotionAnalysis.cpp - Find promotion candidates ===//
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2 //
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3 // The LLVM Compiler Infrastructure
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4 //
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5 // This file is distributed under the University of Illinois Open Source
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6 // License. See LICENSE.TXT for details.
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7 //
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8 //===----------------------------------------------------------------------===//
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9 //
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10 // Helper methods for identifying profitable indirect call promotion
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11 // candidates for an instruction when the indirect-call value profile metadata
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12 // is available.
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13 //
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14 //===----------------------------------------------------------------------===//
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15
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16 #include "llvm/Analysis/IndirectCallPromotionAnalysis.h"
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17 #include "llvm/ADT/STLExtras.h"
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18 #include "llvm/Analysis/IndirectCallSiteVisitor.h"
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19 #include "llvm/IR/CallSite.h"
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20 #include "llvm/IR/DiagnosticInfo.h"
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21 #include "llvm/IR/InstIterator.h"
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22 #include "llvm/IR/InstVisitor.h"
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23 #include "llvm/IR/Instructions.h"
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24 #include "llvm/IR/IntrinsicInst.h"
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25 #include "llvm/ProfileData/InstrProf.h"
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26 #include "llvm/Support/Debug.h"
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27 #include <string>
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28 #include <utility>
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29 #include <vector>
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30
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31 using namespace llvm;
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32
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33 #define DEBUG_TYPE "pgo-icall-prom-analysis"
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34
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121
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35 // The percent threshold for the direct-call target (this call site vs the
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36 // remaining call count) for it to be considered as the promotion target.
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37 static cl::opt<unsigned> ICPRemainingPercentThreshold(
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38 "icp-remaining-percent-threshold", cl::init(30), cl::Hidden, cl::ZeroOrMore,
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39 cl::desc("The percentage threshold against remaining unpromoted indirect "
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40 "call count for the promotion"));
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120
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41
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42 // The percent threshold for the direct-call target (this call site vs the
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43 // total call count) for it to be considered as the promotion target.
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44 static cl::opt<unsigned>
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45 ICPTotalPercentThreshold("icp-total-percent-threshold", cl::init(5),
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46 cl::Hidden, cl::ZeroOrMore,
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47 cl::desc("The percentage threshold against total "
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48 "count for the promotion"));
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120
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49
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50 // Set the maximum number of targets to promote for a single indirect-call
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51 // callsite.
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52 static cl::opt<unsigned>
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53 MaxNumPromotions("icp-max-prom", cl::init(3), cl::Hidden, cl::ZeroOrMore,
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54 cl::desc("Max number of promotions for a single indirect "
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55 "call callsite"));
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56
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57 ICallPromotionAnalysis::ICallPromotionAnalysis() {
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58 ValueDataArray = llvm::make_unique<InstrProfValueData[]>(MaxNumPromotions);
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59 }
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60
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61 bool ICallPromotionAnalysis::isPromotionProfitable(uint64_t Count,
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121
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62 uint64_t TotalCount,
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63 uint64_t RemainingCount) {
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64 return Count * 100 >= ICPRemainingPercentThreshold * RemainingCount &&
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65 Count * 100 >= ICPTotalPercentThreshold * TotalCount;
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120
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66 }
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67
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68 // Indirect-call promotion heuristic. The direct targets are sorted based on
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69 // the count. Stop at the first target that is not promoted. Returns the
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70 // number of candidates deemed profitable.
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71 uint32_t ICallPromotionAnalysis::getProfitablePromotionCandidates(
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72 const Instruction *Inst, uint32_t NumVals, uint64_t TotalCount) {
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73 ArrayRef<InstrProfValueData> ValueDataRef(ValueDataArray.get(), NumVals);
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74
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75 DEBUG(dbgs() << " \nWork on callsite " << *Inst << " Num_targets: " << NumVals
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76 << "\n");
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77
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78 uint32_t I = 0;
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79 uint64_t RemainingCount = TotalCount;
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80 for (; I < MaxNumPromotions && I < NumVals; I++) {
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81 uint64_t Count = ValueDataRef[I].Count;
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82 assert(Count <= RemainingCount);
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83 DEBUG(dbgs() << " Candidate " << I << " Count=" << Count
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84 << " Target_func: " << ValueDataRef[I].Value << "\n");
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85
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86 if (!isPromotionProfitable(Count, TotalCount, RemainingCount)) {
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87 DEBUG(dbgs() << " Not promote: Cold target.\n");
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88 return I;
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89 }
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90 RemainingCount -= Count;
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120
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91 }
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92 return I;
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93 }
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94
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95 ArrayRef<InstrProfValueData>
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96 ICallPromotionAnalysis::getPromotionCandidatesForInstruction(
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97 const Instruction *I, uint32_t &NumVals, uint64_t &TotalCount,
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98 uint32_t &NumCandidates) {
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99 bool Res =
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100 getValueProfDataFromInst(*I, IPVK_IndirectCallTarget, MaxNumPromotions,
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101 ValueDataArray.get(), NumVals, TotalCount);
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102 if (!Res) {
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103 NumCandidates = 0;
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104 return ArrayRef<InstrProfValueData>();
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105 }
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106 NumCandidates = getProfitablePromotionCandidates(I, NumVals, TotalCount);
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107 return ArrayRef<InstrProfValueData>(ValueDataArray.get(), NumVals);
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108 }
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