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 namespace sampleprofutil {
46
47 /// Return true if the given callsite is hot wrt to hot cutoff threshold.
48 ///
49 /// Functions that were inlined in the original binary will be represented
50 /// in the inline stack in the sample profile. If the profile shows that
51 /// the original inline decision was "good" (i.e., the callsite is executed
52 /// frequently), then we will recreate the inline decision and apply the
53 /// profile from the inlined callsite.
54 ///
55 /// To decide whether an inlined callsite is hot, we compare the callsite
56 /// sample count with the hot cutoff computed by ProfileSummaryInfo, it is
57 /// regarded as hot if the count is above the cutoff value.
58 ///
59 /// When ProfileAccurateForSymsInList is enabled and profile symbol list
60 /// is present, functions in the profile symbol list but without profile will
61 /// be regarded as cold and much less inlining will happen in CGSCC inlining
62 /// pass, so we tend to lower the hot criteria here to allow more early
63 /// inlining to happen for warm callsites and it is helpful for performance.
callsiteIsHot(const FunctionSamples * CallsiteFS,ProfileSummaryInfo * PSI,bool ProfAccForSymsInList)64 bool callsiteIsHot(const FunctionSamples *CallsiteFS, ProfileSummaryInfo *PSI,
65 bool ProfAccForSymsInList) {
66 if (!CallsiteFS)
67 return false; // The callsite was not inlined in the original binary.
68
69 assert(PSI && "PSI is expected to be non null");
70 uint64_t CallsiteTotalSamples = CallsiteFS->getTotalSamples();
71 if (ProfAccForSymsInList)
72 return !PSI->isColdCount(CallsiteTotalSamples);
73 else
74 return PSI->isHotCount(CallsiteTotalSamples);
75 }
76
77 /// Mark as used the sample record for the given function samples at
78 /// (LineOffset, Discriminator).
79 ///
80 /// \returns true if this is the first time we mark the given record.
markSamplesUsed(const FunctionSamples * FS,uint32_t LineOffset,uint32_t Discriminator,uint64_t Samples)81 bool SampleCoverageTracker::markSamplesUsed(const FunctionSamples *FS,
82 uint32_t LineOffset,
83 uint32_t Discriminator,
84 uint64_t Samples) {
85 LineLocation Loc(LineOffset, Discriminator);
86 unsigned &Count = SampleCoverage[FS][Loc];
87 bool FirstTime = (++Count == 1);
88 if (FirstTime)
89 TotalUsedSamples += Samples;
90 return FirstTime;
91 }
92
93 /// Return the number of sample records that were applied from this profile.
94 ///
95 /// This count does not include records from cold inlined callsites.
96 unsigned
countUsedRecords(const FunctionSamples * FS,ProfileSummaryInfo * PSI) const97 SampleCoverageTracker::countUsedRecords(const FunctionSamples *FS,
98 ProfileSummaryInfo *PSI) const {
99 auto I = SampleCoverage.find(FS);
100
101 // The size of the coverage map for FS represents the number of records
102 // that were marked used at least once.
103 unsigned Count = (I != SampleCoverage.end()) ? I->second.size() : 0;
104
105 // If there are inlined callsites in this function, count the samples found
106 // in the respective bodies. However, do not bother counting callees with 0
107 // total samples, these are callees that were never invoked at runtime.
108 for (const auto &I : FS->getCallsiteSamples())
109 for (const auto &J : I.second) {
110 const FunctionSamples *CalleeSamples = &J.second;
111 if (callsiteIsHot(CalleeSamples, PSI, ProfAccForSymsInList))
112 Count += countUsedRecords(CalleeSamples, PSI);
113 }
114
115 return Count;
116 }
117
118 /// Return the number of sample records in the body of this profile.
119 ///
120 /// This count does not include records from cold inlined callsites.
121 unsigned
countBodyRecords(const FunctionSamples * FS,ProfileSummaryInfo * PSI) const122 SampleCoverageTracker::countBodyRecords(const FunctionSamples *FS,
123 ProfileSummaryInfo *PSI) const {
124 unsigned Count = FS->getBodySamples().size();
125
126 // Only count records in hot callsites.
127 for (const auto &I : FS->getCallsiteSamples())
128 for (const auto &J : I.second) {
129 const FunctionSamples *CalleeSamples = &J.second;
130 if (callsiteIsHot(CalleeSamples, PSI, ProfAccForSymsInList))
131 Count += countBodyRecords(CalleeSamples, PSI);
132 }
133
134 return Count;
135 }
136
137 /// Return the number of samples collected in the body of this profile.
138 ///
139 /// This count does not include samples from cold inlined callsites.
140 uint64_t
countBodySamples(const FunctionSamples * FS,ProfileSummaryInfo * PSI) const141 SampleCoverageTracker::countBodySamples(const FunctionSamples *FS,
142 ProfileSummaryInfo *PSI) const {
143 uint64_t Total = 0;
144 for (const auto &I : FS->getBodySamples())
145 Total += I.second.getSamples();
146
147 // Only count samples in hot callsites.
148 for (const auto &I : FS->getCallsiteSamples())
149 for (const auto &J : I.second) {
150 const FunctionSamples *CalleeSamples = &J.second;
151 if (callsiteIsHot(CalleeSamples, PSI, ProfAccForSymsInList))
152 Total += countBodySamples(CalleeSamples, PSI);
153 }
154
155 return Total;
156 }
157
158 /// Return the fraction of sample records used in this profile.
159 ///
160 /// The returned value is an unsigned integer in the range 0-100 indicating
161 /// the percentage of sample records that were used while applying this
162 /// profile to the associated function.
computeCoverage(unsigned Used,unsigned Total) const163 unsigned SampleCoverageTracker::computeCoverage(unsigned Used,
164 unsigned Total) const {
165 assert(Used <= Total &&
166 "number of used records cannot exceed the total number of records");
167 return Total > 0 ? Used * 100 / Total : 100;
168 }
169
170 /// Create a global variable to flag FSDiscriminators are used.
createFSDiscriminatorVariable(Module * M)171 void createFSDiscriminatorVariable(Module *M) {
172 const char *FSDiscriminatorVar = "__llvm_fs_discriminator__";
173 if (M->getGlobalVariable(FSDiscriminatorVar))
174 return;
175
176 auto &Context = M->getContext();
177 // Place this variable to llvm.used so it won't be GC'ed.
178 appendToUsed(*M, {new GlobalVariable(*M, Type::getInt1Ty(Context), true,
179 GlobalValue::WeakODRLinkage,
180 ConstantInt::getTrue(Context),
181 FSDiscriminatorVar)});
182 }
183
184 } // end of namespace sampleprofutil
185 } // end of namespace llvm
186