1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
//===-- IndirectCallPromotionAnalysis.cpp - Find promotion candidates ===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Helper methods for identifying profitable indirect call promotion
// candidates for an instruction when the indirect-call value profile metadata
// is available.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/IndirectCallPromotionAnalysis.h"
#include "llvm/IR/Instruction.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
#define DEBUG_TYPE "pgo-icall-prom-analysis"
// The percent threshold for the direct-call target (this call site vs the
// remaining call count) for it to be considered as the promotion target.
static cl::opt<unsigned> ICPRemainingPercentThreshold(
"icp-remaining-percent-threshold", cl::init(30), cl::Hidden,
cl::desc("The percentage threshold against remaining unpromoted indirect "
"call count for the promotion"));
// The percent threshold for the direct-call target (this call site vs the
// total call count) for it to be considered as the promotion target.
static cl::opt<uint64_t>
ICPTotalPercentThreshold("icp-total-percent-threshold", cl::init(5),
cl::Hidden,
cl::desc("The percentage threshold against total "
"count for the promotion"));
// Set the minimum absolute count threshold for indirect call promotion.
// Candidates with counts below this threshold will not be promoted.
static cl::opt<unsigned> ICPMinimumCountThreshold(
"icp-minimum-count-threshold", cl::init(0), cl::Hidden,
cl::desc("Minimum absolute count for promotion candidate"));
// Set the maximum number of targets to promote for a single indirect-call
// callsite.
static cl::opt<unsigned>
MaxNumPromotions("icp-max-prom", cl::init(3), cl::Hidden,
cl::desc("Max number of promotions for a single indirect "
"call callsite"));
cl::opt<unsigned> MaxNumVTableAnnotations(
"icp-max-num-vtables", cl::init(6), cl::Hidden,
cl::desc("Max number of vtables annotated for a vtable load instruction."));
bool ICallPromotionAnalysis::isPromotionProfitable(uint64_t Count,
uint64_t TotalCount,
uint64_t RemainingCount) {
return Count >= ICPMinimumCountThreshold &&
Count * 100 >= ICPRemainingPercentThreshold * RemainingCount &&
Count * 100 >= ICPTotalPercentThreshold * TotalCount;
}
// Indirect-call promotion heuristic. The direct targets are sorted based on
// the count. Stop at the first target that is not promoted. Returns the
// number of candidates deemed profitable.
uint32_t ICallPromotionAnalysis::getProfitablePromotionCandidates(
const Instruction *Inst, uint64_t TotalCount) {
LLVM_DEBUG(dbgs() << " \nWork on callsite " << *Inst
<< " Num_targets: " << ValueDataArray.size() << "\n");
uint32_t I = 0;
uint64_t RemainingCount = TotalCount;
for (; I < MaxNumPromotions && I < ValueDataArray.size(); I++) {
uint64_t Count = ValueDataArray[I].Count;
assert(Count <= RemainingCount);
LLVM_DEBUG(dbgs() << " Candidate " << I << " Count=" << Count
<< " Target_func: " << ValueDataArray[I].Value << "\n");
if (!isPromotionProfitable(Count, TotalCount, RemainingCount)) {
LLVM_DEBUG(dbgs() << " Not promote: Cold target.\n");
return I;
}
RemainingCount -= Count;
}
return I;
}
MutableArrayRef<InstrProfValueData>
ICallPromotionAnalysis::getPromotionCandidatesForInstruction(
const Instruction *I, uint64_t &TotalCount, uint32_t &NumCandidates) {
ValueDataArray = getValueProfDataFromInst(*I, IPVK_IndirectCallTarget,
MaxNumPromotions, TotalCount);
if (ValueDataArray.empty()) {
NumCandidates = 0;
return MutableArrayRef<InstrProfValueData>();
}
NumCandidates = getProfitablePromotionCandidates(I, TotalCount);
return ValueDataArray;
}
|
