LLVM  7.0.0svn
IndirectCallPromotionAnalysis.cpp
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1 //===-- IndirectCallPromotionAnalysis.cpp - Find promotion candidates ===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Helper methods for identifying profitable indirect call promotion
11 // candidates for an instruction when the indirect-call value profile metadata
12 // is available.
13 //
14 //===----------------------------------------------------------------------===//
15 
17 #include "llvm/ADT/STLExtras.h"
19 #include "llvm/IR/CallSite.h"
20 #include "llvm/IR/InstIterator.h"
21 #include "llvm/IR/InstVisitor.h"
22 #include "llvm/IR/Instructions.h"
23 #include "llvm/IR/IntrinsicInst.h"
25 #include "llvm/Support/Debug.h"
26 #include <string>
27 #include <utility>
28 #include <vector>
29 
30 using namespace llvm;
31 
32 #define DEBUG_TYPE "pgo-icall-prom-analysis"
33 
34 // The percent threshold for the direct-call target (this call site vs the
35 // remaining call count) for it to be considered as the promotion target.
37  "icp-remaining-percent-threshold", cl::init(30), cl::Hidden, cl::ZeroOrMore,
38  cl::desc("The percentage threshold against remaining unpromoted indirect "
39  "call count for the promotion"));
40 
41 // The percent threshold for the direct-call target (this call site vs the
42 // total call count) for it to be considered as the promotion target.
43 static cl::opt<unsigned>
44  ICPTotalPercentThreshold("icp-total-percent-threshold", cl::init(5),
46  cl::desc("The percentage threshold against total "
47  "count for the promotion"));
48 
49 // Set the maximum number of targets to promote for a single indirect-call
50 // callsite.
51 static cl::opt<unsigned>
53  cl::desc("Max number of promotions for a single indirect "
54  "call callsite"));
55 
57  ValueDataArray = llvm::make_unique<InstrProfValueData[]>(MaxNumPromotions);
58 }
59 
60 bool ICallPromotionAnalysis::isPromotionProfitable(uint64_t Count,
61  uint64_t TotalCount,
62  uint64_t RemainingCount) {
63  return Count * 100 >= ICPRemainingPercentThreshold * RemainingCount &&
64  Count * 100 >= ICPTotalPercentThreshold * TotalCount;
65 }
66 
67 // Indirect-call promotion heuristic. The direct targets are sorted based on
68 // the count. Stop at the first target that is not promoted. Returns the
69 // number of candidates deemed profitable.
70 uint32_t ICallPromotionAnalysis::getProfitablePromotionCandidates(
71  const Instruction *Inst, uint32_t NumVals, uint64_t TotalCount) {
72  ArrayRef<InstrProfValueData> ValueDataRef(ValueDataArray.get(), NumVals);
73 
74  LLVM_DEBUG(dbgs() << " \nWork on callsite " << *Inst
75  << " Num_targets: " << NumVals << "\n");
76 
77  uint32_t I = 0;
78  uint64_t RemainingCount = TotalCount;
79  for (; I < MaxNumPromotions && I < NumVals; I++) {
80  uint64_t Count = ValueDataRef[I].Count;
81  assert(Count <= RemainingCount);
82  LLVM_DEBUG(dbgs() << " Candidate " << I << " Count=" << Count
83  << " Target_func: " << ValueDataRef[I].Value << "\n");
84 
85  if (!isPromotionProfitable(Count, TotalCount, RemainingCount)) {
86  LLVM_DEBUG(dbgs() << " Not promote: Cold target.\n");
87  return I;
88  }
89  RemainingCount -= Count;
90  }
91  return I;
92 }
93 
96  const Instruction *I, uint32_t &NumVals, uint64_t &TotalCount,
97  uint32_t &NumCandidates) {
98  bool Res =
99  getValueProfDataFromInst(*I, IPVK_IndirectCallTarget, MaxNumPromotions,
100  ValueDataArray.get(), NumVals, TotalCount);
101  if (!Res) {
102  NumCandidates = 0;
104  }
105  NumCandidates = getProfitablePromotionCandidates(I, NumVals, TotalCount);
106  return ArrayRef<InstrProfValueData>(ValueDataArray.get(), NumVals);
107 }
ArrayRef< InstrProfValueData > getPromotionCandidatesForInstruction(const Instruction *I, uint32_t &NumVals, uint64_t &TotalCount, uint32_t &NumCandidates)
Returns reference to array of InstrProfValueData for the given instruction I.
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
static cl::opt< unsigned > ICPTotalPercentThreshold("icp-total-percent-threshold", cl::init(5), cl::Hidden, cl::ZeroOrMore, cl::desc("The percentage threshold against total " "count for the promotion"))
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory)...
Definition: APInt.h:33
Interface to identify indirect call promotion candidates.
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:410
bool getValueProfDataFromInst(const Instruction &Inst, InstrProfValueKind ValueKind, uint32_t MaxNumValueData, InstrProfValueData ValueData[], uint32_t &ActualNumValueData, uint64_t &TotalC)
Extract the value profile data from Inst which is annotated with value profile meta data...
Definition: InstrProf.cpp:857
static cl::opt< unsigned > ICPRemainingPercentThreshold("icp-remaining-percent-threshold", cl::init(30), cl::Hidden, cl::ZeroOrMore, cl::desc("The percentage threshold against remaining unpromoted indirect " "call count for the promotion"))
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
static cl::opt< unsigned > MaxNumPromotions("icp-max-prom", cl::init(3), cl::Hidden, cl::ZeroOrMore, cl::desc("Max number of promotions for a single indirect " "call callsite"))
#define I(x, y, z)
Definition: MD5.cpp:58
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM Value Representation.
Definition: Value.h:73
#define LLVM_DEBUG(X)
Definition: Debug.h:119