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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/Analysis/BlockFrequencyInfo.h"
17 #include "llvm/IR/BasicBlock.h"
18 #include "llvm/IR/CallSite.h"
19 #include "llvm/IR/Metadata.h"
20 #include "llvm/IR/Module.h"
21 #include "llvm/IR/ProfileSummary.h"
22 using namespace llvm;
23 
24 // The following two parameters determine the threshold for a count to be
25 // considered hot/cold. These two parameters are percentile values (multiplied
26 // by 10000). If the counts are sorted in descending order, the minimum count to
27 // reach ProfileSummaryCutoffHot gives the threshold to determine a hot count.
28 // Similarly, the minimum count to reach ProfileSummaryCutoffCold gives the
29 // threshold for determining cold count (everything <= this threshold is
30 // considered cold).
31 
32 static cl::opt<int> ProfileSummaryCutoffHot(
33     "profile-summary-cutoff-hot", cl::Hidden, cl::init(990000), cl::ZeroOrMore,
34     cl::desc("A count is hot if it exceeds the minimum count to"
35              " reach this percentile of total counts."));
36 
37 static cl::opt<int> ProfileSummaryCutoffCold(
38     "profile-summary-cutoff-cold", cl::Hidden, cl::init(999999), cl::ZeroOrMore,
39     cl::desc("A count is cold if it is below the minimum count"
40              " to reach this percentile of total counts."));
41 
42 static cl::opt<bool> ProfileSampleAccurate(
43     "profile-sample-accurate", cl::Hidden, cl::init(false),
44     cl::desc("If the sample profile is accurate, we will mark all un-sampled "
45              "callsite as cold. Otherwise, treat un-sampled callsites as if "
46              "we have no profile."));
47 static cl::opt<unsigned> ProfileSummaryHugeWorkingSetSizeThreshold(
48     "profile-summary-huge-working-set-size-threshold", cl::Hidden,
49     cl::init(15000), cl::ZeroOrMore,
50     cl::desc("The code working set size is considered huge if the number of"
51              " blocks required to reach the -profile-summary-cutoff-hot"
52              " percentile exceeds this count."));
53 
54 // Find the summary entry for a desired percentile of counts.
getEntryForPercentile(SummaryEntryVector & DS,uint64_t Percentile)55 static const ProfileSummaryEntry &getEntryForPercentile(SummaryEntryVector &DS,
56                                                         uint64_t Percentile) {
57   auto Compare = [](const ProfileSummaryEntry &Entry, uint64_t Percentile) {
58     return Entry.Cutoff < Percentile;
59   };
60   auto It = std::lower_bound(DS.begin(), DS.end(), Percentile, Compare);
61   // The required percentile has to be <= one of the percentiles in the
62   // detailed summary.
63   if (It == DS.end())
64     report_fatal_error("Desired percentile exceeds the maximum cutoff");
65   return *It;
66 }
67 
68 // The profile summary metadata may be attached either by the frontend or by
69 // any backend passes (IR level instrumentation, for example). This method
70 // checks if the Summary is null and if so checks if the summary metadata is now
71 // available in the module and parses it to get the Summary object. Returns true
72 // if a valid Summary is available.
computeSummary()73 bool ProfileSummaryInfo::computeSummary() {
74   if (Summary)
75     return true;
76   auto *SummaryMD = M.getProfileSummary();
77   if (!SummaryMD)
78     return false;
79   Summary.reset(ProfileSummary::getFromMD(SummaryMD));
80   return true;
81 }
82 
83 Optional<uint64_t>
getProfileCount(const Instruction * Inst,BlockFrequencyInfo * BFI)84 ProfileSummaryInfo::getProfileCount(const Instruction *Inst,
85                                     BlockFrequencyInfo *BFI) {
86   if (!Inst)
87     return None;
88   assert((isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) &&
89          "We can only get profile count for call/invoke instruction.");
90   if (hasSampleProfile()) {
91     // In sample PGO mode, check if there is a profile metadata on the
92     // instruction. If it is present, determine hotness solely based on that,
93     // since the sampled entry count may not be accurate. If there is no
94     // annotated on the instruction, return None.
95     uint64_t TotalCount;
96     if (Inst->extractProfTotalWeight(TotalCount))
97       return TotalCount;
98     return None;
99   }
100   if (BFI)
101     return BFI->getBlockProfileCount(Inst->getParent());
102   return None;
103 }
104 
105 /// Returns true if the function's entry is hot. If it returns false, it
106 /// either means it is not hot or it is unknown whether it is hot or not (for
107 /// example, no profile data is available).
isFunctionEntryHot(const Function * F)108 bool ProfileSummaryInfo::isFunctionEntryHot(const Function *F) {
109   if (!F || !computeSummary())
110     return false;
111   auto FunctionCount = F->getEntryCount();
112   // FIXME: The heuristic used below for determining hotness is based on
113   // preliminary SPEC tuning for inliner. This will eventually be a
114   // convenience method that calls isHotCount.
115   return FunctionCount && isHotCount(FunctionCount.getCount());
116 }
117 
118 /// Returns true if the function contains hot code. This can include a hot
119 /// function entry count, hot basic block, or (in the case of Sample PGO)
120 /// hot total call edge count.
121 /// If it returns false, it either means it is not hot or it is unknown
122 /// (for example, no profile data is available).
isFunctionHotInCallGraph(const Function * F,BlockFrequencyInfo & BFI)123 bool ProfileSummaryInfo::isFunctionHotInCallGraph(const Function *F,
124                                                   BlockFrequencyInfo &BFI) {
125   if (!F || !computeSummary())
126     return false;
127   if (auto FunctionCount = F->getEntryCount())
128     if (isHotCount(FunctionCount.getCount()))
129       return true;
130 
131   if (hasSampleProfile()) {
132     uint64_t TotalCallCount = 0;
133     for (const auto &BB : *F)
134       for (const auto &I : BB)
135         if (isa<CallInst>(I) || isa<InvokeInst>(I))
136           if (auto CallCount = getProfileCount(&I, nullptr))
137             TotalCallCount += CallCount.getValue();
138     if (isHotCount(TotalCallCount))
139       return true;
140   }
141   for (const auto &BB : *F)
142     if (isHotBB(&BB, &BFI))
143       return true;
144   return false;
145 }
146 
147 /// Returns true if the function only contains cold code. This means that
148 /// the function entry and blocks are all cold, and (in the case of Sample PGO)
149 /// the total call edge count is cold.
150 /// If it returns false, it either means it is not cold or it is unknown
151 /// (for example, no profile data is available).
isFunctionColdInCallGraph(const Function * F,BlockFrequencyInfo & BFI)152 bool ProfileSummaryInfo::isFunctionColdInCallGraph(const Function *F,
153                                                    BlockFrequencyInfo &BFI) {
154   if (!F || !computeSummary())
155     return false;
156   if (auto FunctionCount = F->getEntryCount())
157     if (!isColdCount(FunctionCount.getCount()))
158       return false;
159 
160   if (hasSampleProfile()) {
161     uint64_t TotalCallCount = 0;
162     for (const auto &BB : *F)
163       for (const auto &I : BB)
164         if (isa<CallInst>(I) || isa<InvokeInst>(I))
165           if (auto CallCount = getProfileCount(&I, nullptr))
166             TotalCallCount += CallCount.getValue();
167     if (!isColdCount(TotalCallCount))
168       return false;
169   }
170   for (const auto &BB : *F)
171     if (!isColdBB(&BB, &BFI))
172       return false;
173   return true;
174 }
175 
176 /// Returns true if the function's entry is a cold. If it returns false, it
177 /// either means it is not cold or it is unknown whether it is cold or not (for
178 /// example, no profile data is available).
isFunctionEntryCold(const Function * F)179 bool ProfileSummaryInfo::isFunctionEntryCold(const Function *F) {
180   if (!F)
181     return false;
182   if (F->hasFnAttribute(Attribute::Cold))
183     return true;
184   if (!computeSummary())
185     return false;
186   auto FunctionCount = F->getEntryCount();
187   // FIXME: The heuristic used below for determining coldness is based on
188   // preliminary SPEC tuning for inliner. This will eventually be a
189   // convenience method that calls isHotCount.
190   return FunctionCount && isColdCount(FunctionCount.getCount());
191 }
192 
193 /// Compute the hot and cold thresholds.
computeThresholds()194 void ProfileSummaryInfo::computeThresholds() {
195   if (!computeSummary())
196     return;
197   auto &DetailedSummary = Summary->getDetailedSummary();
198   auto &HotEntry =
199       getEntryForPercentile(DetailedSummary, ProfileSummaryCutoffHot);
200   HotCountThreshold = HotEntry.MinCount;
201   auto &ColdEntry =
202       getEntryForPercentile(DetailedSummary, ProfileSummaryCutoffCold);
203   ColdCountThreshold = ColdEntry.MinCount;
204   HasHugeWorkingSetSize =
205       HotEntry.NumCounts > ProfileSummaryHugeWorkingSetSizeThreshold;
206 }
207 
hasHugeWorkingSetSize()208 bool ProfileSummaryInfo::hasHugeWorkingSetSize() {
209   if (!HasHugeWorkingSetSize)
210     computeThresholds();
211   return HasHugeWorkingSetSize && HasHugeWorkingSetSize.getValue();
212 }
213 
isHotCount(uint64_t C)214 bool ProfileSummaryInfo::isHotCount(uint64_t C) {
215   if (!HotCountThreshold)
216     computeThresholds();
217   return HotCountThreshold && C >= HotCountThreshold.getValue();
218 }
219 
isColdCount(uint64_t C)220 bool ProfileSummaryInfo::isColdCount(uint64_t C) {
221   if (!ColdCountThreshold)
222     computeThresholds();
223   return ColdCountThreshold && C <= ColdCountThreshold.getValue();
224 }
225 
getOrCompHotCountThreshold()226 uint64_t ProfileSummaryInfo::getOrCompHotCountThreshold() {
227   if (!HotCountThreshold)
228     computeThresholds();
229   return HotCountThreshold && HotCountThreshold.getValue();
230 }
231 
getOrCompColdCountThreshold()232 uint64_t ProfileSummaryInfo::getOrCompColdCountThreshold() {
233   if (!ColdCountThreshold)
234     computeThresholds();
235   return ColdCountThreshold && ColdCountThreshold.getValue();
236 }
237 
isHotBB(const BasicBlock * B,BlockFrequencyInfo * BFI)238 bool ProfileSummaryInfo::isHotBB(const BasicBlock *B, BlockFrequencyInfo *BFI) {
239   auto Count = BFI->getBlockProfileCount(B);
240   return Count && isHotCount(*Count);
241 }
242 
isColdBB(const BasicBlock * B,BlockFrequencyInfo * BFI)243 bool ProfileSummaryInfo::isColdBB(const BasicBlock *B,
244                                   BlockFrequencyInfo *BFI) {
245   auto Count = BFI->getBlockProfileCount(B);
246   return Count && isColdCount(*Count);
247 }
248 
isHotCallSite(const CallSite & CS,BlockFrequencyInfo * BFI)249 bool ProfileSummaryInfo::isHotCallSite(const CallSite &CS,
250                                        BlockFrequencyInfo *BFI) {
251   auto C = getProfileCount(CS.getInstruction(), BFI);
252   return C && isHotCount(*C);
253 }
254 
isColdCallSite(const CallSite & CS,BlockFrequencyInfo * BFI)255 bool ProfileSummaryInfo::isColdCallSite(const CallSite &CS,
256                                         BlockFrequencyInfo *BFI) {
257   auto C = getProfileCount(CS.getInstruction(), BFI);
258   if (C)
259     return isColdCount(*C);
260 
261   // In SamplePGO, if the caller has been sampled, and there is no profile
262   // annotated on the callsite, we consider the callsite as cold.
263   // If there is no profile for the caller, and we know the profile is
264   // accurate, we consider the callsite as cold.
265   return (hasSampleProfile() &&
266           (CS.getCaller()->hasProfileData() || ProfileSampleAccurate ||
267            CS.getCaller()->hasFnAttribute("profile-sample-accurate")));
268 }
269 
270 INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
271                 "Profile summary info", false, true)
272 
ProfileSummaryInfoWrapperPass()273 ProfileSummaryInfoWrapperPass::ProfileSummaryInfoWrapperPass()
274     : ImmutablePass(ID) {
275   initializeProfileSummaryInfoWrapperPassPass(*PassRegistry::getPassRegistry());
276 }
277 
doInitialization(Module & M)278 bool ProfileSummaryInfoWrapperPass::doInitialization(Module &M) {
279   PSI.reset(new ProfileSummaryInfo(M));
280   return false;
281 }
282 
doFinalization(Module & M)283 bool ProfileSummaryInfoWrapperPass::doFinalization(Module &M) {
284   PSI.reset();
285   return false;
286 }
287 
288 AnalysisKey ProfileSummaryAnalysis::Key;
run(Module & M,ModuleAnalysisManager &)289 ProfileSummaryInfo ProfileSummaryAnalysis::run(Module &M,
290                                                ModuleAnalysisManager &) {
291   return ProfileSummaryInfo(M);
292 }
293 
run(Module & M,ModuleAnalysisManager & AM)294 PreservedAnalyses ProfileSummaryPrinterPass::run(Module &M,
295                                                  ModuleAnalysisManager &AM) {
296   ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
297 
298   OS << "Functions in " << M.getName() << " with hot/cold annotations: \n";
299   for (auto &F : M) {
300     OS << F.getName();
301     if (PSI.isFunctionEntryHot(&F))
302       OS << " :hot entry ";
303     else if (PSI.isFunctionEntryCold(&F))
304       OS << " :cold entry ";
305     OS << "\n";
306   }
307   return PreservedAnalyses::all();
308 }
309 
310 char ProfileSummaryInfoWrapperPass::ID = 0;
311