1 //===- ProfileSummaryInfo.cpp - Global profile summary information --------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file contains a pass that provides access to the global profile summary
10 // information.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Analysis/ProfileSummaryInfo.h"
15 #include "llvm/Analysis/BlockFrequencyInfo.h"
16 #include "llvm/IR/BasicBlock.h"
17 #include "llvm/IR/Instructions.h"
18 #include "llvm/IR/Module.h"
19 #include "llvm/IR/ProfileSummary.h"
20 #include "llvm/InitializePasses.h"
21 #include "llvm/ProfileData/ProfileCommon.h"
22 #include "llvm/Support/CommandLine.h"
23 using namespace llvm;
24 
25 // Knobs for profile summary based thresholds.
26 extern cl::opt<int> ProfileSummaryCutoffHot;
27 extern cl::opt<int> ProfileSummaryCutoffCold;
28 extern cl::opt<unsigned> ProfileSummaryHugeWorkingSetSizeThreshold;
29 extern cl::opt<unsigned> ProfileSummaryLargeWorkingSetSizeThreshold;
30 extern cl::opt<int> ProfileSummaryHotCount;
31 extern cl::opt<int> ProfileSummaryColdCount;
32 
33 static cl::opt<bool> PartialProfile(
34     "partial-profile", cl::Hidden, cl::init(false),
35     cl::desc("Specify the current profile is used as a partial profile."));
36 
37 cl::opt<bool> ScalePartialSampleProfileWorkingSetSize(
38     "scale-partial-sample-profile-working-set-size", cl::Hidden, cl::init(true),
39     cl::desc(
40         "If true, scale the working set size of the partial sample profile "
41         "by the partial profile ratio to reflect the size of the program "
42         "being compiled."));
43 
44 static cl::opt<double> PartialSampleProfileWorkingSetSizeScaleFactor(
45     "partial-sample-profile-working-set-size-scale-factor", cl::Hidden,
46     cl::init(0.008),
47     cl::desc("The scale factor used to scale the working set size of the "
48              "partial sample profile along with the partial profile ratio. "
49              "This includes the factor of the profile counter per block "
50              "and the factor to scale the working set size to use the same "
51              "shared thresholds as PGO."));
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.
57 void ProfileSummaryInfo::refresh() {
58   if (hasProfileSummary())
59     return;
60   // First try to get context sensitive ProfileSummary.
61   auto *SummaryMD = M->getProfileSummary(/* IsCS */ true);
62   if (SummaryMD)
63     Summary.reset(ProfileSummary::getFromMD(SummaryMD));
64 
65   if (!hasProfileSummary()) {
66     // This will actually return PSK_Instr or PSK_Sample summary.
67     SummaryMD = M->getProfileSummary(/* IsCS */ false);
68     if (SummaryMD)
69       Summary.reset(ProfileSummary::getFromMD(SummaryMD));
70   }
71   if (!hasProfileSummary())
72     return;
73   computeThresholds();
74 }
75 
76 Optional<uint64_t> ProfileSummaryInfo::getProfileCount(
77     const CallBase &Call, BlockFrequencyInfo *BFI, bool AllowSynthetic) const {
78   assert((isa<CallInst>(Call) || isa<InvokeInst>(Call)) &&
79          "We can only get profile count for call/invoke instruction.");
80   if (hasSampleProfile()) {
81     // In sample PGO mode, check if there is a profile metadata on the
82     // instruction. If it is present, determine hotness solely based on that,
83     // since the sampled entry count may not be accurate. If there is no
84     // annotated on the instruction, return None.
85     uint64_t TotalCount;
86     if (Call.extractProfTotalWeight(TotalCount))
87       return TotalCount;
88     return None;
89   }
90   if (BFI)
91     return BFI->getBlockProfileCount(Call.getParent(), AllowSynthetic);
92   return None;
93 }
94 
95 /// Returns true if the function's entry is hot. If it returns false, it
96 /// either means it is not hot or it is unknown whether it is hot or not (for
97 /// example, no profile data is available).
98 bool ProfileSummaryInfo::isFunctionEntryHot(const Function *F) const {
99   if (!F || !hasProfileSummary())
100     return false;
101   auto FunctionCount = F->getEntryCount();
102   // FIXME: The heuristic used below for determining hotness is based on
103   // preliminary SPEC tuning for inliner. This will eventually be a
104   // convenience method that calls isHotCount.
105   return FunctionCount && isHotCount(FunctionCount->getCount());
106 }
107 
108 /// Returns true if the function contains hot code. This can include a hot
109 /// function entry count, hot basic block, or (in the case of Sample PGO)
110 /// hot total call edge count.
111 /// If it returns false, it either means it is not hot or it is unknown
112 /// (for example, no profile data is available).
113 bool ProfileSummaryInfo::isFunctionHotInCallGraph(
114     const Function *F, BlockFrequencyInfo &BFI) const {
115   if (!F || !hasProfileSummary())
116     return false;
117   if (auto FunctionCount = F->getEntryCount())
118     if (isHotCount(FunctionCount->getCount()))
119       return true;
120 
121   if (hasSampleProfile()) {
122     uint64_t TotalCallCount = 0;
123     for (const auto &BB : *F)
124       for (const auto &I : BB)
125         if (isa<CallInst>(I) || isa<InvokeInst>(I))
126           if (auto CallCount = getProfileCount(cast<CallBase>(I), nullptr))
127             TotalCallCount += *CallCount;
128     if (isHotCount(TotalCallCount))
129       return true;
130   }
131   for (const auto &BB : *F)
132     if (isHotBlock(&BB, &BFI))
133       return true;
134   return false;
135 }
136 
137 /// Returns true if the function only contains cold code. This means that
138 /// the function entry and blocks are all cold, and (in the case of Sample PGO)
139 /// the total call edge count is cold.
140 /// If it returns false, it either means it is not cold or it is unknown
141 /// (for example, no profile data is available).
142 bool ProfileSummaryInfo::isFunctionColdInCallGraph(
143     const Function *F, BlockFrequencyInfo &BFI) const {
144   if (!F || !hasProfileSummary())
145     return false;
146   if (auto FunctionCount = F->getEntryCount())
147     if (!isColdCount(FunctionCount->getCount()))
148       return false;
149 
150   if (hasSampleProfile()) {
151     uint64_t TotalCallCount = 0;
152     for (const auto &BB : *F)
153       for (const auto &I : BB)
154         if (isa<CallInst>(I) || isa<InvokeInst>(I))
155           if (auto CallCount = getProfileCount(cast<CallBase>(I), nullptr))
156             TotalCallCount += *CallCount;
157     if (!isColdCount(TotalCallCount))
158       return false;
159   }
160   for (const auto &BB : *F)
161     if (!isColdBlock(&BB, &BFI))
162       return false;
163   return true;
164 }
165 
166 bool ProfileSummaryInfo::isFunctionHotnessUnknown(const Function &F) const {
167   assert(hasPartialSampleProfile() && "Expect partial sample profile");
168   return !F.getEntryCount();
169 }
170 
171 template <bool isHot>
172 bool ProfileSummaryInfo::isFunctionHotOrColdInCallGraphNthPercentile(
173     int PercentileCutoff, const Function *F, BlockFrequencyInfo &BFI) const {
174   if (!F || !hasProfileSummary())
175     return false;
176   if (auto FunctionCount = F->getEntryCount()) {
177     if (isHot &&
178         isHotCountNthPercentile(PercentileCutoff, FunctionCount->getCount()))
179       return true;
180     if (!isHot &&
181         !isColdCountNthPercentile(PercentileCutoff, FunctionCount->getCount()))
182       return false;
183   }
184   if (hasSampleProfile()) {
185     uint64_t TotalCallCount = 0;
186     for (const auto &BB : *F)
187       for (const auto &I : BB)
188         if (isa<CallInst>(I) || isa<InvokeInst>(I))
189           if (auto CallCount = getProfileCount(cast<CallBase>(I), nullptr))
190             TotalCallCount += *CallCount;
191     if (isHot && isHotCountNthPercentile(PercentileCutoff, TotalCallCount))
192       return true;
193     if (!isHot && !isColdCountNthPercentile(PercentileCutoff, TotalCallCount))
194       return false;
195   }
196   for (const auto &BB : *F) {
197     if (isHot && isHotBlockNthPercentile(PercentileCutoff, &BB, &BFI))
198       return true;
199     if (!isHot && !isColdBlockNthPercentile(PercentileCutoff, &BB, &BFI))
200       return false;
201   }
202   return !isHot;
203 }
204 
205 // Like isFunctionHotInCallGraph but for a given cutoff.
206 bool ProfileSummaryInfo::isFunctionHotInCallGraphNthPercentile(
207     int PercentileCutoff, const Function *F, BlockFrequencyInfo &BFI) const {
208   return isFunctionHotOrColdInCallGraphNthPercentile<true>(
209       PercentileCutoff, F, BFI);
210 }
211 
212 bool ProfileSummaryInfo::isFunctionColdInCallGraphNthPercentile(
213     int PercentileCutoff, const Function *F, BlockFrequencyInfo &BFI) const {
214   return isFunctionHotOrColdInCallGraphNthPercentile<false>(
215       PercentileCutoff, F, BFI);
216 }
217 
218 /// Returns true if the function's entry is a cold. If it returns false, it
219 /// either means it is not cold or it is unknown whether it is cold or not (for
220 /// example, no profile data is available).
221 bool ProfileSummaryInfo::isFunctionEntryCold(const Function *F) const {
222   if (!F)
223     return false;
224   if (F->hasFnAttribute(Attribute::Cold))
225     return true;
226   if (!hasProfileSummary())
227     return false;
228   auto FunctionCount = F->getEntryCount();
229   // FIXME: The heuristic used below for determining coldness is based on
230   // preliminary SPEC tuning for inliner. This will eventually be a
231   // convenience method that calls isHotCount.
232   return FunctionCount && isColdCount(FunctionCount->getCount());
233 }
234 
235 /// Compute the hot and cold thresholds.
236 void ProfileSummaryInfo::computeThresholds() {
237   auto &DetailedSummary = Summary->getDetailedSummary();
238   auto &HotEntry = ProfileSummaryBuilder::getEntryForPercentile(
239       DetailedSummary, ProfileSummaryCutoffHot);
240   HotCountThreshold =
241       ProfileSummaryBuilder::getHotCountThreshold(DetailedSummary);
242   ColdCountThreshold =
243       ProfileSummaryBuilder::getColdCountThreshold(DetailedSummary);
244   assert(ColdCountThreshold <= HotCountThreshold &&
245          "Cold count threshold cannot exceed hot count threshold!");
246   if (!hasPartialSampleProfile() || !ScalePartialSampleProfileWorkingSetSize) {
247     HasHugeWorkingSetSize =
248         HotEntry.NumCounts > ProfileSummaryHugeWorkingSetSizeThreshold;
249     HasLargeWorkingSetSize =
250         HotEntry.NumCounts > ProfileSummaryLargeWorkingSetSizeThreshold;
251   } else {
252     // Scale the working set size of the partial sample profile to reflect the
253     // size of the program being compiled.
254     double PartialProfileRatio = Summary->getPartialProfileRatio();
255     uint64_t ScaledHotEntryNumCounts =
256         static_cast<uint64_t>(HotEntry.NumCounts * PartialProfileRatio *
257                               PartialSampleProfileWorkingSetSizeScaleFactor);
258     HasHugeWorkingSetSize =
259         ScaledHotEntryNumCounts > ProfileSummaryHugeWorkingSetSizeThreshold;
260     HasLargeWorkingSetSize =
261         ScaledHotEntryNumCounts > ProfileSummaryLargeWorkingSetSizeThreshold;
262   }
263 }
264 
265 Optional<uint64_t>
266 ProfileSummaryInfo::computeThreshold(int PercentileCutoff) const {
267   if (!hasProfileSummary())
268     return None;
269   auto iter = ThresholdCache.find(PercentileCutoff);
270   if (iter != ThresholdCache.end()) {
271     return iter->second;
272   }
273   auto &DetailedSummary = Summary->getDetailedSummary();
274   auto &Entry = ProfileSummaryBuilder::getEntryForPercentile(DetailedSummary,
275                                                              PercentileCutoff);
276   uint64_t CountThreshold = Entry.MinCount;
277   ThresholdCache[PercentileCutoff] = CountThreshold;
278   return CountThreshold;
279 }
280 
281 bool ProfileSummaryInfo::hasHugeWorkingSetSize() const {
282   return HasHugeWorkingSetSize && HasHugeWorkingSetSize.value();
283 }
284 
285 bool ProfileSummaryInfo::hasLargeWorkingSetSize() const {
286   return HasLargeWorkingSetSize && HasLargeWorkingSetSize.value();
287 }
288 
289 bool ProfileSummaryInfo::isHotCount(uint64_t C) const {
290   return HotCountThreshold && C >= HotCountThreshold.value();
291 }
292 
293 bool ProfileSummaryInfo::isColdCount(uint64_t C) const {
294   return ColdCountThreshold && C <= ColdCountThreshold.value();
295 }
296 
297 template <bool isHot>
298 bool ProfileSummaryInfo::isHotOrColdCountNthPercentile(int PercentileCutoff,
299                                                        uint64_t C) const {
300   auto CountThreshold = computeThreshold(PercentileCutoff);
301   if (isHot)
302     return CountThreshold && C >= CountThreshold.value();
303   else
304     return CountThreshold && C <= CountThreshold.value();
305 }
306 
307 bool ProfileSummaryInfo::isHotCountNthPercentile(int PercentileCutoff,
308                                                  uint64_t C) const {
309   return isHotOrColdCountNthPercentile<true>(PercentileCutoff, C);
310 }
311 
312 bool ProfileSummaryInfo::isColdCountNthPercentile(int PercentileCutoff,
313                                                   uint64_t C) const {
314   return isHotOrColdCountNthPercentile<false>(PercentileCutoff, C);
315 }
316 
317 uint64_t ProfileSummaryInfo::getOrCompHotCountThreshold() const {
318   return HotCountThreshold.value_or(UINT64_MAX);
319 }
320 
321 uint64_t ProfileSummaryInfo::getOrCompColdCountThreshold() const {
322   return ColdCountThreshold.value_or(0);
323 }
324 
325 bool ProfileSummaryInfo::isHotBlock(const BasicBlock *BB,
326                                     BlockFrequencyInfo *BFI) const {
327   auto Count = BFI->getBlockProfileCount(BB);
328   return Count && isHotCount(*Count);
329 }
330 
331 bool ProfileSummaryInfo::isColdBlock(const BasicBlock *BB,
332                                      BlockFrequencyInfo *BFI) const {
333   auto Count = BFI->getBlockProfileCount(BB);
334   return Count && isColdCount(*Count);
335 }
336 
337 template <bool isHot>
338 bool ProfileSummaryInfo::isHotOrColdBlockNthPercentile(
339     int PercentileCutoff, const BasicBlock *BB, BlockFrequencyInfo *BFI) const {
340   auto Count = BFI->getBlockProfileCount(BB);
341   if (isHot)
342     return Count && isHotCountNthPercentile(PercentileCutoff, *Count);
343   else
344     return Count && isColdCountNthPercentile(PercentileCutoff, *Count);
345 }
346 
347 bool ProfileSummaryInfo::isHotBlockNthPercentile(
348     int PercentileCutoff, const BasicBlock *BB, BlockFrequencyInfo *BFI) const {
349   return isHotOrColdBlockNthPercentile<true>(PercentileCutoff, BB, BFI);
350 }
351 
352 bool ProfileSummaryInfo::isColdBlockNthPercentile(
353     int PercentileCutoff, const BasicBlock *BB, BlockFrequencyInfo *BFI) const {
354   return isHotOrColdBlockNthPercentile<false>(PercentileCutoff, BB, BFI);
355 }
356 
357 bool ProfileSummaryInfo::isHotCallSite(const CallBase &CB,
358                                        BlockFrequencyInfo *BFI) const {
359   auto C = getProfileCount(CB, BFI);
360   return C && isHotCount(*C);
361 }
362 
363 bool ProfileSummaryInfo::isColdCallSite(const CallBase &CB,
364                                         BlockFrequencyInfo *BFI) const {
365   auto C = getProfileCount(CB, BFI);
366   if (C)
367     return isColdCount(*C);
368 
369   // In SamplePGO, if the caller has been sampled, and there is no profile
370   // annotated on the callsite, we consider the callsite as cold.
371   return hasSampleProfile() && CB.getCaller()->hasProfileData();
372 }
373 
374 bool ProfileSummaryInfo::hasPartialSampleProfile() const {
375   return hasProfileSummary() &&
376          Summary->getKind() == ProfileSummary::PSK_Sample &&
377          (PartialProfile || Summary->isPartialProfile());
378 }
379 
380 INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
381                 "Profile summary info", false, true)
382 
383 ProfileSummaryInfoWrapperPass::ProfileSummaryInfoWrapperPass()
384     : ImmutablePass(ID) {
385   initializeProfileSummaryInfoWrapperPassPass(*PassRegistry::getPassRegistry());
386 }
387 
388 bool ProfileSummaryInfoWrapperPass::doInitialization(Module &M) {
389   PSI.reset(new ProfileSummaryInfo(M));
390   return false;
391 }
392 
393 bool ProfileSummaryInfoWrapperPass::doFinalization(Module &M) {
394   PSI.reset();
395   return false;
396 }
397 
398 AnalysisKey ProfileSummaryAnalysis::Key;
399 ProfileSummaryInfo ProfileSummaryAnalysis::run(Module &M,
400                                                ModuleAnalysisManager &) {
401   return ProfileSummaryInfo(M);
402 }
403 
404 PreservedAnalyses ProfileSummaryPrinterPass::run(Module &M,
405                                                  ModuleAnalysisManager &AM) {
406   ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
407 
408   OS << "Functions in " << M.getName() << " with hot/cold annotations: \n";
409   for (auto &F : M) {
410     OS << F.getName();
411     if (PSI.isFunctionEntryHot(&F))
412       OS << " :hot entry ";
413     else if (PSI.isFunctionEntryCold(&F))
414       OS << " :cold entry ";
415     OS << "\n";
416   }
417   return PreservedAnalyses::all();
418 }
419 
420 char ProfileSummaryInfoWrapperPass::ID = 0;
421