1 //===- PDBStringTableBuilder.cpp - PDB String Table -------------*- C++ -*-===// 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 #include "llvm/DebugInfo/PDB/Native/PDBStringTableBuilder.h" 10 11 #include "llvm/ADT/ArrayRef.h" 12 #include "llvm/DebugInfo/PDB/Native/Hash.h" 13 #include "llvm/DebugInfo/PDB/Native/RawTypes.h" 14 #include "llvm/Support/BinaryStreamWriter.h" 15 #include "llvm/Support/Endian.h" 16 17 #include <map> 18 19 using namespace llvm; 20 using namespace llvm::msf; 21 using namespace llvm::support; 22 using namespace llvm::support::endian; 23 using namespace llvm::pdb; 24 25 StringTableHashTraits::StringTableHashTraits(PDBStringTableBuilder &Table) 26 : Table(&Table) {} 27 28 uint32_t StringTableHashTraits::hashLookupKey(StringRef S) const { 29 // The reference implementation doesn't include code for /src/headerblock 30 // handling, but it can only read natvis entries lld's PDB files if 31 // this hash function truncates the hash to 16 bit. 32 // PDB/include/misc.h in the reference implementation has a hashSz() function 33 // that returns an unsigned short, that seems what's being used for 34 // /src/headerblock. 35 return static_cast<uint16_t>(Table->getIdForString(S)); 36 } 37 38 StringRef StringTableHashTraits::storageKeyToLookupKey(uint32_t Offset) const { 39 return Table->getStringForId(Offset); 40 } 41 42 uint32_t StringTableHashTraits::lookupKeyToStorageKey(StringRef S) { 43 return Table->insert(S); 44 } 45 46 uint32_t PDBStringTableBuilder::insert(StringRef S) { 47 return Strings.insert(S); 48 } 49 50 uint32_t PDBStringTableBuilder::getIdForString(StringRef S) const { 51 return Strings.getIdForString(S); 52 } 53 54 StringRef PDBStringTableBuilder::getStringForId(uint32_t Id) const { 55 return Strings.getStringForId(Id); 56 } 57 58 static uint32_t computeBucketCount(uint32_t NumStrings) { 59 // This is a precomputed list of Buckets given the specified number of 60 // strings. Matching the reference algorithm exactly is not strictly 61 // necessary for correctness, but it helps when comparing LLD's PDBs with 62 // Microsoft's PDBs so as to eliminate superfluous differences. 63 // The reference implementation does (in nmt.h, NMT::grow()): 64 // unsigned StringCount = 0; 65 // unsigned BucketCount = 1; 66 // fn insert() { 67 // ++StringCount; 68 // if (BucketCount * 3 / 4 < StringCount) 69 // BucketCount = BucketCount * 3 / 2 + 1; 70 // } 71 // This list contains all StringCount, BucketCount pairs where BucketCount was 72 // just incremented. It ends before the first BucketCount entry where 73 // BucketCount * 3 would overflow a 32-bit unsigned int. 74 static const std::pair<uint32_t, uint32_t> StringsToBuckets[] = { 75 {0, 1}, 76 {1, 2}, 77 {2, 4}, 78 {4, 7}, 79 {6, 11}, 80 {9, 17}, 81 {13, 26}, 82 {20, 40}, 83 {31, 61}, 84 {46, 92}, 85 {70, 139}, 86 {105, 209}, 87 {157, 314}, 88 {236, 472}, 89 {355, 709}, 90 {532, 1064}, 91 {799, 1597}, 92 {1198, 2396}, 93 {1798, 3595}, 94 {2697, 5393}, 95 {4045, 8090}, 96 {6068, 12136}, 97 {9103, 18205}, 98 {13654, 27308}, 99 {20482, 40963}, 100 {30723, 61445}, 101 {46084, 92168}, 102 {69127, 138253}, 103 {103690, 207380}, 104 {155536, 311071}, 105 {233304, 466607}, 106 {349956, 699911}, 107 {524934, 1049867}, 108 {787401, 1574801}, 109 {1181101, 2362202}, 110 {1771652, 3543304}, 111 {2657479, 5314957}, 112 {3986218, 7972436}, 113 {5979328, 11958655}, 114 {8968992, 17937983}, 115 {13453488, 26906975}, 116 {20180232, 40360463}, 117 {30270348, 60540695}, 118 {45405522, 90811043}, 119 {68108283, 136216565}, 120 {102162424, 204324848}, 121 {153243637, 306487273}, 122 {229865455, 459730910}, 123 {344798183, 689596366}, 124 {517197275, 1034394550}, 125 {775795913, 1551591826}, 126 {1163693870, 2327387740}}; 127 const auto *Entry = llvm::lower_bound( 128 StringsToBuckets, std::make_pair(NumStrings, 0U), llvm::less_first()); 129 assert(Entry != std::end(StringsToBuckets)); 130 return Entry->second; 131 } 132 133 uint32_t PDBStringTableBuilder::calculateHashTableSize() const { 134 uint32_t Size = sizeof(uint32_t); // Hash table begins with 4-byte size field. 135 Size += sizeof(uint32_t) * computeBucketCount(Strings.size()); 136 137 return Size; 138 } 139 140 uint32_t PDBStringTableBuilder::calculateSerializedSize() const { 141 uint32_t Size = 0; 142 Size += sizeof(PDBStringTableHeader); 143 Size += Strings.calculateSerializedSize(); 144 Size += calculateHashTableSize(); 145 Size += sizeof(uint32_t); // The /names stream ends with the string count. 146 return Size; 147 } 148 149 void PDBStringTableBuilder::setStrings( 150 const codeview::DebugStringTableSubsection &Strings) { 151 this->Strings = Strings; 152 } 153 154 Error PDBStringTableBuilder::writeHeader(BinaryStreamWriter &Writer) const { 155 // Write a header 156 PDBStringTableHeader H; 157 H.Signature = PDBStringTableSignature; 158 H.HashVersion = 1; 159 H.ByteSize = Strings.calculateSerializedSize(); 160 if (auto EC = Writer.writeObject(H)) 161 return EC; 162 assert(Writer.bytesRemaining() == 0); 163 return Error::success(); 164 } 165 166 Error PDBStringTableBuilder::writeStrings(BinaryStreamWriter &Writer) const { 167 if (auto EC = Strings.commit(Writer)) 168 return EC; 169 170 assert(Writer.bytesRemaining() == 0); 171 return Error::success(); 172 } 173 174 Error PDBStringTableBuilder::writeHashTable(BinaryStreamWriter &Writer) const { 175 // Write a hash table. 176 uint32_t BucketCount = computeBucketCount(Strings.size()); 177 if (auto EC = Writer.writeInteger(BucketCount)) 178 return EC; 179 std::vector<ulittle32_t> Buckets(BucketCount); 180 181 for (const auto &Pair : Strings) { 182 StringRef S = Pair.getKey(); 183 uint32_t Offset = Pair.getValue(); 184 uint32_t Hash = hashStringV1(S); 185 186 for (uint32_t I = 0; I != BucketCount; ++I) { 187 uint32_t Slot = (Hash + I) % BucketCount; 188 if (Buckets[Slot] != 0) 189 continue; 190 Buckets[Slot] = Offset; 191 break; 192 } 193 } 194 195 if (auto EC = Writer.writeArray(ArrayRef<ulittle32_t>(Buckets))) 196 return EC; 197 198 assert(Writer.bytesRemaining() == 0); 199 return Error::success(); 200 } 201 202 Error PDBStringTableBuilder::writeEpilogue(BinaryStreamWriter &Writer) const { 203 if (auto EC = Writer.writeInteger<uint32_t>(Strings.size())) 204 return EC; 205 assert(Writer.bytesRemaining() == 0); 206 return Error::success(); 207 } 208 209 Error PDBStringTableBuilder::commit(BinaryStreamWriter &Writer) const { 210 BinaryStreamWriter SectionWriter; 211 212 std::tie(SectionWriter, Writer) = Writer.split(sizeof(PDBStringTableHeader)); 213 if (auto EC = writeHeader(SectionWriter)) 214 return EC; 215 216 std::tie(SectionWriter, Writer) = 217 Writer.split(Strings.calculateSerializedSize()); 218 if (auto EC = writeStrings(SectionWriter)) 219 return EC; 220 221 std::tie(SectionWriter, Writer) = Writer.split(calculateHashTableSize()); 222 if (auto EC = writeHashTable(SectionWriter)) 223 return EC; 224 225 std::tie(SectionWriter, Writer) = Writer.split(sizeof(uint32_t)); 226 if (auto EC = writeEpilogue(SectionWriter)) 227 return EC; 228 229 return Error::success(); 230 } 231