LLVM  15.0.0git
IndirectCallPromotionAnalysis.cpp
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1 //===-- IndirectCallPromotionAnalysis.cpp - Find promotion candidates ===//
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 // Helper methods for identifying profitable indirect call promotion
10 // candidates for an instruction when the indirect-call value profile metadata
11 // is available.
12 //
13 //===----------------------------------------------------------------------===//
14 
16 #include "llvm/IR/Instruction.h"
19 #include "llvm/Support/Debug.h"
20 #include <memory>
21 
22 using namespace llvm;
23 
24 #define DEBUG_TYPE "pgo-icall-prom-analysis"
25 
26 // The percent threshold for the direct-call target (this call site vs the
27 // remaining call count) for it to be considered as the promotion target.
29  "icp-remaining-percent-threshold", cl::init(30), cl::Hidden, cl::ZeroOrMore,
30  cl::desc("The percentage threshold against remaining unpromoted indirect "
31  "call count for the promotion"));
32 
33 // The percent threshold for the direct-call target (this call site vs the
34 // total call count) for it to be considered as the promotion target.
35 static cl::opt<unsigned>
36  ICPTotalPercentThreshold("icp-total-percent-threshold", cl::init(5),
38  cl::desc("The percentage threshold against total "
39  "count for the promotion"));
40 
41 // Set the maximum number of targets to promote for a single indirect-call
42 // callsite.
43 static cl::opt<unsigned>
45  cl::desc("Max number of promotions for a single indirect "
46  "call callsite"));
47 
49  ValueDataArray = std::make_unique<InstrProfValueData[]>(MaxNumPromotions);
50 }
51 
52 bool ICallPromotionAnalysis::isPromotionProfitable(uint64_t Count,
53  uint64_t TotalCount,
54  uint64_t RemainingCount) {
55  return Count * 100 >= ICPRemainingPercentThreshold * RemainingCount &&
56  Count * 100 >= ICPTotalPercentThreshold * TotalCount;
57 }
58 
59 // Indirect-call promotion heuristic. The direct targets are sorted based on
60 // the count. Stop at the first target that is not promoted. Returns the
61 // number of candidates deemed profitable.
62 uint32_t ICallPromotionAnalysis::getProfitablePromotionCandidates(
63  const Instruction *Inst, uint32_t NumVals, uint64_t TotalCount) {
64  ArrayRef<InstrProfValueData> ValueDataRef(ValueDataArray.get(), NumVals);
65 
66  LLVM_DEBUG(dbgs() << " \nWork on callsite " << *Inst
67  << " Num_targets: " << NumVals << "\n");
68 
69  uint32_t I = 0;
70  uint64_t RemainingCount = TotalCount;
71  for (; I < MaxNumPromotions && I < NumVals; I++) {
72  uint64_t Count = ValueDataRef[I].Count;
73  assert(Count <= RemainingCount);
74  LLVM_DEBUG(dbgs() << " Candidate " << I << " Count=" << Count
75  << " Target_func: " << ValueDataRef[I].Value << "\n");
76 
77  if (!isPromotionProfitable(Count, TotalCount, RemainingCount)) {
78  LLVM_DEBUG(dbgs() << " Not promote: Cold target.\n");
79  return I;
80  }
81  RemainingCount -= Count;
82  }
83  return I;
84 }
85 
88  const Instruction *I, uint32_t &NumVals, uint64_t &TotalCount,
89  uint32_t &NumCandidates) {
90  bool Res =
91  getValueProfDataFromInst(*I, IPVK_IndirectCallTarget, MaxNumPromotions,
92  ValueDataArray.get(), NumVals, TotalCount);
93  if (!Res) {
94  NumCandidates = 0;
96  }
97  NumCandidates = getProfitablePromotionCandidates(I, NumVals, TotalCount);
98  return ArrayRef<InstrProfValueData>(ValueDataArray.get(), NumVals);
99 }
llvm
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:17
llvm::cl::Hidden
@ Hidden
Definition: CommandLine.h:139
ICPTotalPercentThreshold
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"))
LLVM_DEBUG
#define LLVM_DEBUG(X)
Definition: Debug.h:101
IndirectCallPromotionAnalysis.h
llvm::dbgs
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
Instruction.h
CommandLine.h
llvm::Instruction
Definition: Instruction.h:42
InstrProf.h
llvm::cl::ZeroOrMore
@ ZeroOrMore
Definition: CommandLine.h:116
llvm::cl::opt
Definition: CommandLine.h:1392
uint64_t
ICPRemainingPercentThreshold
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"))
I
#define I(x, y, z)
Definition: MD5.cpp:58
llvm::cl::init
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:432
assert
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
llvm::ArrayRef
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: APInt.h:32
uint32_t
llvm::ICallPromotionAnalysis::getPromotionCandidatesForInstruction
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.
Definition: IndirectCallPromotionAnalysis.cpp:87
llvm::ICallPromotionAnalysis::ICallPromotionAnalysis
ICallPromotionAnalysis()
Definition: IndirectCallPromotionAnalysis.cpp:48
llvm::getValueProfDataFromInst
bool getValueProfDataFromInst(const Instruction &Inst, InstrProfValueKind ValueKind, uint32_t MaxNumValueData, InstrProfValueData ValueData[], uint32_t &ActualNumValueData, uint64_t &TotalC, bool GetNoICPValue=false)
Extract the value profile data from Inst which is annotated with value profile meta data.
Definition: InstrProf.cpp:1039
llvm::cl::desc
Definition: CommandLine.h:405
MaxNumPromotions
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"))
llvm::Value
LLVM Value Representation.
Definition: Value.h:74
Debug.h