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comparison lib/Analysis/ProfileSummaryInfo.cpp @ 120:1172e4bd9c6f

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update 4.0.0
author mir3636
date Fri, 25 Nov 2016 19:14:25 +0900
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children 803732b1fca8
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101:34baf5011add 120:1172e4bd9c6f
1 //===- ProfileSummaryInfo.cpp - Global profile summary information --------===//
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 // This file contains a pass that provides access to the global profile summary
11 // information.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "llvm/Analysis/BlockFrequencyInfo.h"
16 #include "llvm/Analysis/ProfileSummaryInfo.h"
17 #include "llvm/IR/BasicBlock.h"
18 #include "llvm/IR/Metadata.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/IR/ProfileSummary.h"
21 using namespace llvm;
22
23 // The following two parameters determine the threshold for a count to be
24 // considered hot/cold. These two parameters are percentile values (multiplied
25 // by 10000). If the counts are sorted in descending order, the minimum count to
26 // reach ProfileSummaryCutoffHot gives the threshold to determine a hot count.
27 // Similarly, the minimum count to reach ProfileSummaryCutoffCold gives the
28 // threshold for determining cold count (everything <= this threshold is
29 // considered cold).
30
31 static cl::opt<int> ProfileSummaryCutoffHot(
32 "profile-summary-cutoff-hot", cl::Hidden, cl::init(999000), cl::ZeroOrMore,
33 cl::desc("A count is hot if it exceeds the minimum count to"
34 " reach this percentile of total counts."));
35
36 static cl::opt<int> ProfileSummaryCutoffCold(
37 "profile-summary-cutoff-cold", cl::Hidden, cl::init(999999), cl::ZeroOrMore,
38 cl::desc("A count is cold if it is below the minimum count"
39 " to reach this percentile of total counts."));
40
41 // Find the minimum count to reach a desired percentile of counts.
42 static uint64_t getMinCountForPercentile(SummaryEntryVector &DS,
43 uint64_t Percentile) {
44 auto Compare = [](const ProfileSummaryEntry &Entry, uint64_t Percentile) {
45 return Entry.Cutoff < Percentile;
46 };
47 auto It = std::lower_bound(DS.begin(), DS.end(), Percentile, Compare);
48 // The required percentile has to be <= one of the percentiles in the
49 // detailed summary.
50 if (It == DS.end())
51 report_fatal_error("Desired percentile exceeds the maximum cutoff");
52 return It->MinCount;
53 }
54
55 // The profile summary metadata may be attached either by the frontend or by
56 // any backend passes (IR level instrumentation, for example). This method
57 // checks if the Summary is null and if so checks if the summary metadata is now
58 // available in the module and parses it to get the Summary object.
59 void ProfileSummaryInfo::computeSummary() {
60 if (Summary)
61 return;
62 auto *SummaryMD = M.getProfileSummary();
63 if (!SummaryMD)
64 return;
65 Summary.reset(ProfileSummary::getFromMD(SummaryMD));
66 }
67
68 /// Returns true if the function's entry is hot. If it returns false, it
69 /// either means it is not hot or it is unknown whether it is hot or not (for
70 /// example, no profile data is available).
71 bool ProfileSummaryInfo::isFunctionEntryHot(const Function *F) {
72 computeSummary();
73 if (!F || !Summary)
74 return false;
75 auto FunctionCount = F->getEntryCount();
76 // FIXME: The heuristic used below for determining hotness is based on
77 // preliminary SPEC tuning for inliner. This will eventually be a
78 // convenience method that calls isHotCount.
79 return FunctionCount && isHotCount(FunctionCount.getValue());
80 }
81
82 /// Returns true if the function's entry is a cold. If it returns false, it
83 /// either means it is not cold or it is unknown whether it is cold or not (for
84 /// example, no profile data is available).
85 bool ProfileSummaryInfo::isFunctionEntryCold(const Function *F) {
86 computeSummary();
87 if (!F)
88 return false;
89 if (F->hasFnAttribute(Attribute::Cold)) {
90 return true;
91 }
92 if (!Summary)
93 return false;
94 auto FunctionCount = F->getEntryCount();
95 // FIXME: The heuristic used below for determining coldness is based on
96 // preliminary SPEC tuning for inliner. This will eventually be a
97 // convenience method that calls isHotCount.
98 return FunctionCount && isColdCount(FunctionCount.getValue());
99 }
100
101 /// Compute the hot and cold thresholds.
102 void ProfileSummaryInfo::computeThresholds() {
103 if (!Summary)
104 computeSummary();
105 if (!Summary)
106 return;
107 auto &DetailedSummary = Summary->getDetailedSummary();
108 HotCountThreshold =
109 getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffHot);
110 ColdCountThreshold =
111 getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffCold);
112 }
113
114 bool ProfileSummaryInfo::isHotCount(uint64_t C) {
115 if (!HotCountThreshold)
116 computeThresholds();
117 return HotCountThreshold && C >= HotCountThreshold.getValue();
118 }
119
120 bool ProfileSummaryInfo::isColdCount(uint64_t C) {
121 if (!ColdCountThreshold)
122 computeThresholds();
123 return ColdCountThreshold && C <= ColdCountThreshold.getValue();
124 }
125
126 bool ProfileSummaryInfo::isHotBB(const BasicBlock *B, BlockFrequencyInfo *BFI) {
127 auto Count = BFI->getBlockProfileCount(B);
128 if (Count && isHotCount(*Count))
129 return true;
130 // Use extractProfTotalWeight to get BB count.
131 // For Sample PGO, BFI may not provide accurate BB count due to errors
132 // magnified during sample count propagation. This serves as a backup plan
133 // to ensure all hot BB will not be missed.
134 // The query currently has false positives as branch instruction cloning does
135 // not update/scale branch weights. Unlike false negatives, this will not cause
136 // performance problem.
137 uint64_t TotalCount;
138 if (B->getTerminator()->extractProfTotalWeight(TotalCount) &&
139 isHotCount(TotalCount))
140 return true;
141 return false;
142 }
143
144 INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
145 "Profile summary info", false, true)
146
147 ProfileSummaryInfoWrapperPass::ProfileSummaryInfoWrapperPass()
148 : ImmutablePass(ID) {
149 initializeProfileSummaryInfoWrapperPassPass(*PassRegistry::getPassRegistry());
150 }
151
152 bool ProfileSummaryInfoWrapperPass::doInitialization(Module &M) {
153 PSI.reset(new ProfileSummaryInfo(M));
154 return false;
155 }
156
157 bool ProfileSummaryInfoWrapperPass::doFinalization(Module &M) {
158 PSI.reset();
159 return false;
160 }
161
162 AnalysisKey ProfileSummaryAnalysis::Key;
163 ProfileSummaryInfo ProfileSummaryAnalysis::run(Module &M,
164 ModuleAnalysisManager &) {
165 return ProfileSummaryInfo(M);
166 }
167
168 PreservedAnalyses ProfileSummaryPrinterPass::run(Module &M,
169 ModuleAnalysisManager &AM) {
170 ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
171
172 OS << "Functions in " << M.getName() << " with hot/cold annotations: \n";
173 for (auto &F : M) {
174 OS << F.getName();
175 if (PSI.isFunctionEntryHot(&F))
176 OS << " :hot entry ";
177 else if (PSI.isFunctionEntryCold(&F))
178 OS << " :cold entry ";
179 OS << "\n";
180 }
181 return PreservedAnalyses::all();
182 }
183
184 char ProfileSummaryInfoWrapperPass::ID = 0;