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/ProfileSummaryInfo.h"
16 #include "llvm/IR/Metadata.h"
17 #include "llvm/IR/Module.h"
18 #include "llvm/IR/ProfileSummary.h"
19 using namespace llvm;
20
21 // The following two parameters determine the threshold for a count to be
22 // considered hot/cold. These two parameters are percentile values (multiplied
23 // by 10000). If the counts are sorted in descending order, the minimum count to
24 // reach ProfileSummaryCutoffHot gives the threshold to determine a hot count.
25 // Similarly, the minimum count to reach ProfileSummaryCutoffCold gives the
26 // threshold for determining cold count (everything <= this threshold is
27 // considered cold).
28
29 static cl::opt<int> ProfileSummaryCutoffHot(
30 "profile-summary-cutoff-hot", cl::Hidden, cl::init(999000), cl::ZeroOrMore,
31 cl::desc("A count is hot if it exceeds the minimum count to"
32 " reach this percentile of total counts."));
33
34 static cl::opt<int> ProfileSummaryCutoffCold(
35 "profile-summary-cutoff-cold", cl::Hidden, cl::init(999999), cl::ZeroOrMore,
36 cl::desc("A count is cold if it is below the minimum count"
37 " to reach this percentile of total counts."));
38
39 // Find the minimum count to reach a desired percentile of counts.
getMinCountForPercentile(SummaryEntryVector & DS,uint64_t Percentile)40 static uint64_t getMinCountForPercentile(SummaryEntryVector &DS,
41 uint64_t Percentile) {
42 auto Compare = [](const ProfileSummaryEntry &Entry, uint64_t Percentile) {
43 return Entry.Cutoff < Percentile;
44 };
45 auto It = std::lower_bound(DS.begin(), DS.end(), Percentile, Compare);
46 // The required percentile has to be <= one of the percentiles in the
47 // detailed summary.
48 if (It == DS.end())
49 report_fatal_error("Desired percentile exceeds the maximum cutoff");
50 return It->MinCount;
51 }
52
53 // The profile summary metadata may be attached either by the frontend or by
54 // any backend passes (IR level instrumentation, for example). This method
55 // checks if the Summary is null and if so checks if the summary metadata is now
56 // available in the module and parses it to get the Summary object.
computeSummary()57 void ProfileSummaryInfo::computeSummary() {
58 if (Summary)
59 return;
60 auto *SummaryMD = M.getProfileSummary();
61 if (!SummaryMD)
62 return;
63 Summary.reset(ProfileSummary::getFromMD(SummaryMD));
64 }
65
66 // Returns true if the function is a hot function. If it returns false, it
67 // either means it is not hot or it is unknown whether F is hot or not (for
68 // example, no profile data is available).
isHotFunction(const Function * F)69 bool ProfileSummaryInfo::isHotFunction(const Function *F) {
70 computeSummary();
71 if (!F || !Summary)
72 return false;
73 auto FunctionCount = F->getEntryCount();
74 // FIXME: The heuristic used below for determining hotness is based on
75 // preliminary SPEC tuning for inliner. This will eventually be a
76 // convenience method that calls isHotCount.
77 return (FunctionCount &&
78 FunctionCount.getValue() >=
79 (uint64_t)(0.3 * (double)Summary->getMaxFunctionCount()));
80 }
81
82 // Returns true if the function is a cold function. If it returns false, it
83 // either means it is not cold or it is unknown whether F is cold or not (for
84 // example, no profile data is available).
isColdFunction(const Function * F)85 bool ProfileSummaryInfo::isColdFunction(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 &&
99 FunctionCount.getValue() <=
100 (uint64_t)(0.01 * (double)Summary->getMaxFunctionCount()));
101 }
102
103 // Compute the hot and cold thresholds.
computeThresholds()104 void ProfileSummaryInfo::computeThresholds() {
105 if (!Summary)
106 computeSummary();
107 if (!Summary)
108 return;
109 auto &DetailedSummary = Summary->getDetailedSummary();
110 HotCountThreshold =
111 getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffHot);
112 ColdCountThreshold =
113 getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffCold);
114 }
115
isHotCount(uint64_t C)116 bool ProfileSummaryInfo::isHotCount(uint64_t C) {
117 if (!HotCountThreshold)
118 computeThresholds();
119 return HotCountThreshold && C >= HotCountThreshold.getValue();
120 }
121
isColdCount(uint64_t C)122 bool ProfileSummaryInfo::isColdCount(uint64_t C) {
123 if (!ColdCountThreshold)
124 computeThresholds();
125 return ColdCountThreshold && C <= ColdCountThreshold.getValue();
126 }
127
getPSI(Module & M)128 ProfileSummaryInfo *ProfileSummaryInfoWrapperPass::getPSI(Module &M) {
129 if (!PSI)
130 PSI.reset(new ProfileSummaryInfo(M));
131 return PSI.get();
132 }
133
134 INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
135 "Profile summary info", false, true)
136
ProfileSummaryInfoWrapperPass()137 ProfileSummaryInfoWrapperPass::ProfileSummaryInfoWrapperPass()
138 : ImmutablePass(ID) {
139 initializeProfileSummaryInfoWrapperPassPass(*PassRegistry::getPassRegistry());
140 }
141
142 char ProfileSummaryAnalysis::PassID;
run(Module & M,ModuleAnalysisManager &)143 ProfileSummaryInfo ProfileSummaryAnalysis::run(Module &M,
144 ModuleAnalysisManager &) {
145 return ProfileSummaryInfo(M);
146 }
147
148 // FIXME: This only tests isHotFunction and isColdFunction and not the
149 // isHotCount and isColdCount calls.
run(Module & M,AnalysisManager<Module> & AM)150 PreservedAnalyses ProfileSummaryPrinterPass::run(Module &M,
151 AnalysisManager<Module> &AM) {
152 ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
153
154 OS << "Functions in " << M.getName() << " with hot/cold annotations: \n";
155 for (auto &F : M) {
156 OS << F.getName();
157 if (PSI.isHotFunction(&F))
158 OS << " :hot ";
159 else if (PSI.isColdFunction(&F))
160 OS << " :cold ";
161 OS << "\n";
162 }
163 return PreservedAnalyses::all();
164 }
165
166 char ProfileSummaryInfoWrapperPass::ID = 0;
167