• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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