1 //===- SampleProfileLoaderBaseUtil.cpp - Profile loader Util func ---------===//
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 implements the SampleProfileLoader base utility functions.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/Transforms/Utils/SampleProfileLoaderBaseUtil.h"
14 #include "llvm/Analysis/ProfileSummaryInfo.h"
15 #include "llvm/IR/Constants.h"
16 #include "llvm/IR/Module.h"
17 #include "llvm/Transforms/Utils/ModuleUtils.h"
18 
19 namespace llvm {
20 
21 cl::opt<unsigned> SampleProfileMaxPropagateIterations(
22     "sample-profile-max-propagate-iterations", cl::init(100),
23     cl::desc("Maximum number of iterations to go through when propagating "
24              "sample block/edge weights through the CFG."));
25 
26 cl::opt<unsigned> SampleProfileRecordCoverage(
27     "sample-profile-check-record-coverage", cl::init(0), cl::value_desc("N"),
28     cl::desc("Emit a warning if less than N% of records in the input profile "
29              "are matched to the IR."));
30 
31 cl::opt<unsigned> SampleProfileSampleCoverage(
32     "sample-profile-check-sample-coverage", cl::init(0), cl::value_desc("N"),
33     cl::desc("Emit a warning if less than N% of samples in the input profile "
34              "are matched to the IR."));
35 
36 cl::opt<bool> NoWarnSampleUnused(
37     "no-warn-sample-unused", cl::init(false), cl::Hidden,
38     cl::desc("Use this option to turn off/on warnings about function with "
39              "samples but without debug information to use those samples. "));
40 
41 cl::opt<bool> SampleProfileUseProfi(
42     "sample-profile-use-profi", cl::Hidden,
43     cl::desc("Use profi to infer block and edge counts."));
44 
45 cl::opt<bool> SampleProfileInferEntryCount(
46     "sample-profile-infer-entry-count", cl::init(true), cl::Hidden,
47     cl::desc("Use profi to infer function entry count."));
48 
49 namespace sampleprofutil {
50 
51 /// Return true if the given callsite is hot wrt to hot cutoff threshold.
52 ///
53 /// Functions that were inlined in the original binary will be represented
54 /// in the inline stack in the sample profile. If the profile shows that
55 /// the original inline decision was "good" (i.e., the callsite is executed
56 /// frequently), then we will recreate the inline decision and apply the
57 /// profile from the inlined callsite.
58 ///
59 /// To decide whether an inlined callsite is hot, we compare the callsite
60 /// sample count with the hot cutoff computed by ProfileSummaryInfo, it is
61 /// regarded as hot if the count is above the cutoff value.
62 ///
63 /// When ProfileAccurateForSymsInList is enabled and profile symbol list
64 /// is present, functions in the profile symbol list but without profile will
65 /// be regarded as cold and much less inlining will happen in CGSCC inlining
66 /// pass, so we tend to lower the hot criteria here to allow more early
67 /// inlining to happen for warm callsites and it is helpful for performance.
68 bool callsiteIsHot(const FunctionSamples *CallsiteFS, ProfileSummaryInfo *PSI,
69                    bool ProfAccForSymsInList) {
70   if (!CallsiteFS)
71     return false; // The callsite was not inlined in the original binary.
72 
73   assert(PSI && "PSI is expected to be non null");
74   uint64_t CallsiteTotalSamples = CallsiteFS->getTotalSamples();
75   if (ProfAccForSymsInList)
76     return !PSI->isColdCount(CallsiteTotalSamples);
77   else
78     return PSI->isHotCount(CallsiteTotalSamples);
79 }
80 
81 /// Mark as used the sample record for the given function samples at
82 /// (LineOffset, Discriminator).
83 ///
84 /// \returns true if this is the first time we mark the given record.
85 bool SampleCoverageTracker::markSamplesUsed(const FunctionSamples *FS,
86                                             uint32_t LineOffset,
87                                             uint32_t Discriminator,
88                                             uint64_t Samples) {
89   LineLocation Loc(LineOffset, Discriminator);
90   unsigned &Count = SampleCoverage[FS][Loc];
91   bool FirstTime = (++Count == 1);
92   if (FirstTime)
93     TotalUsedSamples += Samples;
94   return FirstTime;
95 }
96 
97 /// Return the number of sample records that were applied from this profile.
98 ///
99 /// This count does not include records from cold inlined callsites.
100 unsigned
101 SampleCoverageTracker::countUsedRecords(const FunctionSamples *FS,
102                                         ProfileSummaryInfo *PSI) const {
103   auto I = SampleCoverage.find(FS);
104 
105   // The size of the coverage map for FS represents the number of records
106   // that were marked used at least once.
107   unsigned Count = (I != SampleCoverage.end()) ? I->second.size() : 0;
108 
109   // If there are inlined callsites in this function, count the samples found
110   // in the respective bodies. However, do not bother counting callees with 0
111   // total samples, these are callees that were never invoked at runtime.
112   for (const auto &I : FS->getCallsiteSamples())
113     for (const auto &J : I.second) {
114       const FunctionSamples *CalleeSamples = &J.second;
115       if (callsiteIsHot(CalleeSamples, PSI, ProfAccForSymsInList))
116         Count += countUsedRecords(CalleeSamples, PSI);
117     }
118 
119   return Count;
120 }
121 
122 /// Return the number of sample records in the body of this profile.
123 ///
124 /// This count does not include records from cold inlined callsites.
125 unsigned
126 SampleCoverageTracker::countBodyRecords(const FunctionSamples *FS,
127                                         ProfileSummaryInfo *PSI) const {
128   unsigned Count = FS->getBodySamples().size();
129 
130   // Only count records in hot callsites.
131   for (const auto &I : FS->getCallsiteSamples())
132     for (const auto &J : I.second) {
133       const FunctionSamples *CalleeSamples = &J.second;
134       if (callsiteIsHot(CalleeSamples, PSI, ProfAccForSymsInList))
135         Count += countBodyRecords(CalleeSamples, PSI);
136     }
137 
138   return Count;
139 }
140 
141 /// Return the number of samples collected in the body of this profile.
142 ///
143 /// This count does not include samples from cold inlined callsites.
144 uint64_t
145 SampleCoverageTracker::countBodySamples(const FunctionSamples *FS,
146                                         ProfileSummaryInfo *PSI) const {
147   uint64_t Total = 0;
148   for (const auto &I : FS->getBodySamples())
149     Total += I.second.getSamples();
150 
151   // Only count samples in hot callsites.
152   for (const auto &I : FS->getCallsiteSamples())
153     for (const auto &J : I.second) {
154       const FunctionSamples *CalleeSamples = &J.second;
155       if (callsiteIsHot(CalleeSamples, PSI, ProfAccForSymsInList))
156         Total += countBodySamples(CalleeSamples, PSI);
157     }
158 
159   return Total;
160 }
161 
162 /// Return the fraction of sample records used in this profile.
163 ///
164 /// The returned value is an unsigned integer in the range 0-100 indicating
165 /// the percentage of sample records that were used while applying this
166 /// profile to the associated function.
167 unsigned SampleCoverageTracker::computeCoverage(unsigned Used,
168                                                 unsigned Total) const {
169   assert(Used <= Total &&
170          "number of used records cannot exceed the total number of records");
171   return Total > 0 ? Used * 100 / Total : 100;
172 }
173 
174 /// Create a global variable to flag FSDiscriminators are used.
175 void createFSDiscriminatorVariable(Module *M) {
176   const char *FSDiscriminatorVar = "__llvm_fs_discriminator__";
177   if (M->getGlobalVariable(FSDiscriminatorVar))
178     return;
179 
180   auto &Context = M->getContext();
181   // Place this variable to llvm.used so it won't be GC'ed.
182   appendToUsed(*M, {new GlobalVariable(*M, Type::getInt1Ty(Context), true,
183                                        GlobalValue::WeakODRLinkage,
184                                        ConstantInt::getTrue(Context),
185                                        FSDiscriminatorVar)});
186 }
187 
188 } // end of namespace sampleprofutil
189 } // end of namespace llvm
190