1 //===- CoverageMappingWriter.cpp - Code coverage mapping writer -----------===//
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 support for writing coverage mapping data for
10 // instrumentation based coverage.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/ProfileData/InstrProf.h"
15 #include "llvm/ProfileData/Coverage/CoverageMappingWriter.h"
16 #include "llvm/ADT/ArrayRef.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/Support/Compression.h"
19 #include "llvm/Support/LEB128.h"
20 #include "llvm/Support/raw_ostream.h"
21 #include <algorithm>
22 #include <cassert>
23 #include <limits>
24 #include <vector>
25 
26 using namespace llvm;
27 using namespace coverage;
28 
29 CoverageFilenamesSectionWriter::CoverageFilenamesSectionWriter(
30     ArrayRef<std::string> Filenames)
31     : Filenames(Filenames) {
32 #ifndef NDEBUG
33   StringSet<> NameSet;
34   for (StringRef Name : Filenames)
35     assert(NameSet.insert(Name).second && "Duplicate filename");
36 #endif
37 }
38 
39 void CoverageFilenamesSectionWriter::write(raw_ostream &OS, bool Compress) {
40   std::string FilenamesStr;
41   {
42     raw_string_ostream FilenamesOS{FilenamesStr};
43     for (const auto &Filename : Filenames) {
44       encodeULEB128(Filename.size(), FilenamesOS);
45       FilenamesOS << Filename;
46     }
47   }
48 
49   SmallVector<uint8_t, 128> CompressedStr;
50   bool doCompression = Compress && compression::zlib::isAvailable() &&
51                        DoInstrProfNameCompression;
52   if (doCompression)
53     compression::zlib::compress(arrayRefFromStringRef(FilenamesStr),
54                                 CompressedStr,
55                                 compression::zlib::BestSizeCompression);
56 
57   // ::= <num-filenames>
58   //     <uncompressed-len>
59   //     <compressed-len-or-zero>
60   //     (<compressed-filenames> | <uncompressed-filenames>)
61   encodeULEB128(Filenames.size(), OS);
62   encodeULEB128(FilenamesStr.size(), OS);
63   encodeULEB128(doCompression ? CompressedStr.size() : 0U, OS);
64   OS << (doCompression ? toStringRef(CompressedStr) : StringRef(FilenamesStr));
65 }
66 
67 namespace {
68 
69 /// Gather only the expressions that are used by the mapping
70 /// regions in this function.
71 class CounterExpressionsMinimizer {
72   ArrayRef<CounterExpression> Expressions;
73   SmallVector<CounterExpression, 16> UsedExpressions;
74   std::vector<unsigned> AdjustedExpressionIDs;
75 
76 public:
77   CounterExpressionsMinimizer(ArrayRef<CounterExpression> Expressions,
78                               ArrayRef<CounterMappingRegion> MappingRegions)
79       : Expressions(Expressions) {
80     AdjustedExpressionIDs.resize(Expressions.size(), 0);
81     for (const auto &I : MappingRegions) {
82       mark(I.Count);
83       mark(I.FalseCount);
84     }
85     for (const auto &I : MappingRegions) {
86       gatherUsed(I.Count);
87       gatherUsed(I.FalseCount);
88     }
89   }
90 
91   void mark(Counter C) {
92     if (!C.isExpression())
93       return;
94     unsigned ID = C.getExpressionID();
95     AdjustedExpressionIDs[ID] = 1;
96     mark(Expressions[ID].LHS);
97     mark(Expressions[ID].RHS);
98   }
99 
100   void gatherUsed(Counter C) {
101     if (!C.isExpression() || !AdjustedExpressionIDs[C.getExpressionID()])
102       return;
103     AdjustedExpressionIDs[C.getExpressionID()] = UsedExpressions.size();
104     const auto &E = Expressions[C.getExpressionID()];
105     UsedExpressions.push_back(E);
106     gatherUsed(E.LHS);
107     gatherUsed(E.RHS);
108   }
109 
110   ArrayRef<CounterExpression> getExpressions() const { return UsedExpressions; }
111 
112   /// Adjust the given counter to correctly transition from the old
113   /// expression ids to the new expression ids.
114   Counter adjust(Counter C) const {
115     if (C.isExpression())
116       C = Counter::getExpression(AdjustedExpressionIDs[C.getExpressionID()]);
117     return C;
118   }
119 };
120 
121 } // end anonymous namespace
122 
123 /// Encode the counter.
124 ///
125 /// The encoding uses the following format:
126 /// Low 2 bits - Tag:
127 ///   Counter::Zero(0) - A Counter with kind Counter::Zero
128 ///   Counter::CounterValueReference(1) - A counter with kind
129 ///     Counter::CounterValueReference
130 ///   Counter::Expression(2) + CounterExpression::Subtract(0) -
131 ///     A counter with kind Counter::Expression and an expression
132 ///     with kind CounterExpression::Subtract
133 ///   Counter::Expression(2) + CounterExpression::Add(1) -
134 ///     A counter with kind Counter::Expression and an expression
135 ///     with kind CounterExpression::Add
136 /// Remaining bits - Counter/Expression ID.
137 static unsigned encodeCounter(ArrayRef<CounterExpression> Expressions,
138                               Counter C) {
139   unsigned Tag = unsigned(C.getKind());
140   if (C.isExpression())
141     Tag += Expressions[C.getExpressionID()].Kind;
142   unsigned ID = C.getCounterID();
143   assert(ID <=
144          (std::numeric_limits<unsigned>::max() >> Counter::EncodingTagBits));
145   return Tag | (ID << Counter::EncodingTagBits);
146 }
147 
148 static void writeCounter(ArrayRef<CounterExpression> Expressions, Counter C,
149                          raw_ostream &OS) {
150   encodeULEB128(encodeCounter(Expressions, C), OS);
151 }
152 
153 void CoverageMappingWriter::write(raw_ostream &OS) {
154   // Check that we don't have any bogus regions.
155   assert(all_of(MappingRegions,
156                 [](const CounterMappingRegion &CMR) {
157                   return CMR.startLoc() <= CMR.endLoc();
158                 }) &&
159          "Source region does not begin before it ends");
160 
161   // Sort the regions in an ascending order by the file id and the starting
162   // location. Sort by region kinds to ensure stable order for tests.
163   llvm::stable_sort(MappingRegions, [](const CounterMappingRegion &LHS,
164                                        const CounterMappingRegion &RHS) {
165     if (LHS.FileID != RHS.FileID)
166       return LHS.FileID < RHS.FileID;
167     if (LHS.startLoc() != RHS.startLoc())
168       return LHS.startLoc() < RHS.startLoc();
169     return LHS.Kind < RHS.Kind;
170   });
171 
172   // Write out the fileid -> filename mapping.
173   encodeULEB128(VirtualFileMapping.size(), OS);
174   for (const auto &FileID : VirtualFileMapping)
175     encodeULEB128(FileID, OS);
176 
177   // Write out the expressions.
178   CounterExpressionsMinimizer Minimizer(Expressions, MappingRegions);
179   auto MinExpressions = Minimizer.getExpressions();
180   encodeULEB128(MinExpressions.size(), OS);
181   for (const auto &E : MinExpressions) {
182     writeCounter(MinExpressions, Minimizer.adjust(E.LHS), OS);
183     writeCounter(MinExpressions, Minimizer.adjust(E.RHS), OS);
184   }
185 
186   // Write out the mapping regions.
187   // Split the regions into subarrays where each region in a
188   // subarray has a fileID which is the index of that subarray.
189   unsigned PrevLineStart = 0;
190   unsigned CurrentFileID = ~0U;
191   for (auto I = MappingRegions.begin(), E = MappingRegions.end(); I != E; ++I) {
192     if (I->FileID != CurrentFileID) {
193       // Ensure that all file ids have at least one mapping region.
194       assert(I->FileID == (CurrentFileID + 1));
195       // Find the number of regions with this file id.
196       unsigned RegionCount = 1;
197       for (auto J = I + 1; J != E && I->FileID == J->FileID; ++J)
198         ++RegionCount;
199       // Start a new region sub-array.
200       encodeULEB128(RegionCount, OS);
201 
202       CurrentFileID = I->FileID;
203       PrevLineStart = 0;
204     }
205     Counter Count = Minimizer.adjust(I->Count);
206     Counter FalseCount = Minimizer.adjust(I->FalseCount);
207     switch (I->Kind) {
208     case CounterMappingRegion::CodeRegion:
209     case CounterMappingRegion::GapRegion:
210       writeCounter(MinExpressions, Count, OS);
211       break;
212     case CounterMappingRegion::ExpansionRegion: {
213       assert(Count.isZero());
214       assert(I->ExpandedFileID <=
215              (std::numeric_limits<unsigned>::max() >>
216               Counter::EncodingCounterTagAndExpansionRegionTagBits));
217       // Mark an expansion region with a set bit that follows the counter tag,
218       // and pack the expanded file id into the remaining bits.
219       unsigned EncodedTagExpandedFileID =
220           (1 << Counter::EncodingTagBits) |
221           (I->ExpandedFileID
222            << Counter::EncodingCounterTagAndExpansionRegionTagBits);
223       encodeULEB128(EncodedTagExpandedFileID, OS);
224       break;
225     }
226     case CounterMappingRegion::SkippedRegion:
227       assert(Count.isZero());
228       encodeULEB128(unsigned(I->Kind)
229                         << Counter::EncodingCounterTagAndExpansionRegionTagBits,
230                     OS);
231       break;
232     case CounterMappingRegion::BranchRegion:
233       encodeULEB128(unsigned(I->Kind)
234                         << Counter::EncodingCounterTagAndExpansionRegionTagBits,
235                     OS);
236       writeCounter(MinExpressions, Count, OS);
237       writeCounter(MinExpressions, FalseCount, OS);
238       break;
239     }
240     assert(I->LineStart >= PrevLineStart);
241     encodeULEB128(I->LineStart - PrevLineStart, OS);
242     encodeULEB128(I->ColumnStart, OS);
243     assert(I->LineEnd >= I->LineStart);
244     encodeULEB128(I->LineEnd - I->LineStart, OS);
245     encodeULEB128(I->ColumnEnd, OS);
246     PrevLineStart = I->LineStart;
247   }
248   // Ensure that all file ids have at least one mapping region.
249   assert(CurrentFileID == (VirtualFileMapping.size() - 1));
250 }
251