1//===- MultiOnDiskHashTable.h - Merged set of hash tables -------*- 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// This file provides a hash table data structure suitable for incremental and
10// distributed storage across a set of files.
11//
12// Multiple hash tables from different files are implicitly merged to improve
13// performance, and on reload the merged table will override those from other
14// files.
15//
16//===----------------------------------------------------------------------===//
17
18#ifndef LLVM_CLANG_LIB_SERIALIZATION_MULTIONDISKHASHTABLE_H
19#define LLVM_CLANG_LIB_SERIALIZATION_MULTIONDISKHASHTABLE_H
20
21#include "llvm/ADT/DenseMap.h"
22#include "llvm/ADT/DenseSet.h"
23#include "llvm/ADT/PointerUnion.h"
24#include "llvm/ADT/STLExtras.h"
25#include "llvm/ADT/SmallVector.h"
26#include "llvm/ADT/TinyPtrVector.h"
27#include "llvm/ADT/iterator_range.h"
28#include "llvm/Support/Endian.h"
29#include "llvm/Support/EndianStream.h"
30#include "llvm/Support/OnDiskHashTable.h"
31#include "llvm/Support/raw_ostream.h"
32#include <algorithm>
33#include <cstdint>
34#include <vector>
35
36namespace clang {
37namespace serialization {
38
39/// A collection of on-disk hash tables, merged when relevant for performance.
40template<typename Info> class MultiOnDiskHashTable {
41public:
42 /// A handle to a file, used when overriding tables.
43 using file_type = typename Info::file_type;
44
45 /// A pointer to an on-disk representation of the hash table.
46 using storage_type = const unsigned char *;
47
48 using external_key_type = typename Info::external_key_type;
49 using internal_key_type = typename Info::internal_key_type;
50 using data_type = typename Info::data_type;
51 using data_type_builder = typename Info::data_type_builder;
52 using hash_value_type = unsigned;
53
54private:
55 /// The generator is permitted to read our merged table.
56 template<typename ReaderInfo, typename WriterInfo>
57 friend class MultiOnDiskHashTableGenerator;
58
59 /// A hash table stored on disk.
60 struct OnDiskTable {
61 using HashTable = llvm::OnDiskIterableChainedHashTable<Info>;
62
63 file_type File;
64 HashTable Table;
65
66 OnDiskTable(file_type File, unsigned NumBuckets, unsigned NumEntries,
67 storage_type Buckets, storage_type Payload, storage_type Base,
68 const Info &InfoObj)
69 : File(File),
70 Table(NumBuckets, NumEntries, Buckets, Payload, Base, InfoObj) {}
71 };
72
73 struct MergedTable {
74 std::vector<file_type> Files;
75 llvm::DenseMap<internal_key_type, data_type> Data;
76 };
77
78 using Table = llvm::PointerUnion<OnDiskTable *, MergedTable *>;
79 using TableVector = llvm::TinyPtrVector<void *>;
80
81 /// The current set of on-disk and merged tables.
82 /// We manually store the opaque value of the Table because TinyPtrVector
83 /// can't cope with holding a PointerUnion directly.
84 /// There can be at most one MergedTable in this vector, and if present,
85 /// it is the first table.
86 TableVector Tables;
87
88 /// Files corresponding to overridden tables that we've not yet
89 /// discarded.
90 llvm::TinyPtrVector<file_type> PendingOverrides;
91
92 struct AsOnDiskTable {
93 using result_type = OnDiskTable *;
94
95 result_type operator()(void *P) const {
96 return llvm::cast<OnDiskTable *>(Table::getFromOpaqueValue(P));
97 }
98 };
99
100 using table_iterator =
101 llvm::mapped_iterator<TableVector::iterator, AsOnDiskTable>;
102 using table_range = llvm::iterator_range<table_iterator>;
103
104 /// The current set of on-disk tables.
105 table_range tables() {
106 unsigned DropBegin = getMergedTable() ? 1 : 0;
107 return llvm::map_range(llvm::drop_begin(RangeOrContainer&: Tables, N: DropBegin),
108 AsOnDiskTable());
109 }
110
111 MergedTable *getMergedTable() const {
112 // If we already have a merged table, it's the first one.
113 return Tables.empty() ? nullptr : Table::getFromOpaqueValue(*Tables.begin())
114 .template dyn_cast<MergedTable*>();
115 }
116
117 /// Delete all our current on-disk tables.
118 void clear() {
119 for (auto *T : tables())
120 delete T;
121 if (auto *M = getMergedTable())
122 delete M;
123 Tables.clear();
124 }
125
126 void removeOverriddenTables() {
127 llvm::DenseSet<file_type> Files;
128 Files.insert_range(PendingOverrides);
129 // Explicitly capture Files to work around an MSVC 2015 rejects-valid bug.
130 auto ShouldRemove = [&Files](void *T) -> bool {
131 auto *ODT = llvm::cast<OnDiskTable *>(Table::getFromOpaqueValue(T));
132 bool Remove = Files.count(ODT->File);
133 if (Remove)
134 delete ODT;
135 return Remove;
136 };
137 Tables.erase(std::remove_if(tables().begin().getCurrent(), Tables.end(),
138 ShouldRemove),
139 Tables.end());
140 PendingOverrides.clear();
141 }
142
143 void condense() {
144 MergedTable *Merged = getMergedTable();
145 if (!Merged)
146 Merged = new MergedTable;
147
148 // Read in all the tables and merge them together.
149 // FIXME: Be smarter about which tables we merge.
150 for (auto *ODT : tables()) {
151 auto &HT = ODT->Table;
152 Info &InfoObj = HT.getInfoObj();
153
154 for (auto I = HT.data_begin(), E = HT.data_end(); I != E; ++I) {
155 auto *LocalPtr = I.getItem();
156
157 // FIXME: Don't rely on the OnDiskHashTable format here.
158 auto L = InfoObj.ReadKeyDataLength(LocalPtr);
159 const internal_key_type &Key = InfoObj.ReadKey(LocalPtr, L.first);
160 data_type_builder ValueBuilder(Merged->Data[Key]);
161 InfoObj.ReadDataInto(Key, LocalPtr + L.first, L.second,
162 ValueBuilder);
163 }
164
165 Merged->Files.push_back(ODT->File);
166 delete ODT;
167 }
168
169 Tables.clear();
170 Tables.push_back(NewVal: Table(Merged).getOpaqueValue());
171 }
172
173public:
174 MultiOnDiskHashTable() = default;
175
176 MultiOnDiskHashTable(MultiOnDiskHashTable &&O)
177 : Tables(std::move(O.Tables)),
178 PendingOverrides(std::move(O.PendingOverrides)) {
179 O.Tables.clear();
180 }
181
182 MultiOnDiskHashTable &operator=(MultiOnDiskHashTable &&O) {
183 if (&O == this)
184 return *this;
185 clear();
186 Tables = std::move(O.Tables);
187 O.Tables.clear();
188 PendingOverrides = std::move(O.PendingOverrides);
189 return *this;
190 }
191
192 ~MultiOnDiskHashTable() { clear(); }
193
194 /// Add the table \p Data loaded from file \p File.
195 void add(file_type File, storage_type Data, Info InfoObj = Info()) {
196 using namespace llvm::support;
197
198 storage_type Ptr = Data;
199
200 uint32_t BucketOffset =
201 endian::readNext<uint32_t, llvm::endianness::little>(memory&: Ptr);
202
203 // Read the list of overridden files.
204 uint32_t NumFiles =
205 endian::readNext<uint32_t, llvm::endianness::little>(memory&: Ptr);
206 // FIXME: Add a reserve() to TinyPtrVector so that we don't need to make
207 // an additional copy.
208 llvm::SmallVector<file_type, 16> OverriddenFiles;
209 OverriddenFiles.reserve(NumFiles);
210 for (/**/; NumFiles != 0; --NumFiles)
211 OverriddenFiles.push_back(InfoObj.ReadFileRef(Ptr));
212 llvm::append_range(PendingOverrides, OverriddenFiles);
213
214 // Read the OnDiskChainedHashTable header.
215 storage_type Buckets = Data + BucketOffset;
216 auto NumBucketsAndEntries =
217 OnDiskTable::HashTable::readNumBucketsAndEntries(Buckets);
218
219 // Register the table.
220 Table NewTable = new OnDiskTable(File, NumBucketsAndEntries.first,
221 NumBucketsAndEntries.second,
222 Buckets, Ptr, Data, std::move(InfoObj));
223 Tables.push_back(NewVal: NewTable.getOpaqueValue());
224 }
225
226 /// Find and read the lookup results for \p EKey.
227 data_type find(const external_key_type &EKey) {
228 data_type Result;
229
230 if (!PendingOverrides.empty())
231 removeOverriddenTables();
232
233 if (Tables.size() > static_cast<unsigned>(Info::MaxTables))
234 condense();
235
236 internal_key_type Key = Info::GetInternalKey(EKey);
237 auto KeyHash = Info::ComputeHash(Key);
238
239 if (MergedTable *M = getMergedTable()) {
240 auto It = M->Data.find(Key);
241 if (It != M->Data.end())
242 Result = It->second;
243 }
244
245 data_type_builder ResultBuilder(Result);
246
247 for (auto *ODT : tables()) {
248 auto &HT = ODT->Table;
249 auto It = HT.find_hashed(Key, KeyHash);
250 if (It != HT.end())
251 HT.getInfoObj().ReadDataInto(Key, It.getDataPtr(), It.getDataLen(),
252 ResultBuilder);
253 }
254
255 return Result;
256 }
257
258 /// Read all the lookup results into a single value. This only makes
259 /// sense if merging values across keys is meaningful.
260 data_type findAll() {
261 data_type Result;
262 data_type_builder ResultBuilder(Result);
263
264 if (!PendingOverrides.empty())
265 removeOverriddenTables();
266
267 if (MergedTable *M = getMergedTable()) {
268 for (auto &KV : M->Data)
269 Info::MergeDataInto(KV.second, ResultBuilder);
270 }
271
272 for (auto *ODT : tables()) {
273 auto &HT = ODT->Table;
274 Info &InfoObj = HT.getInfoObj();
275 for (auto I = HT.data_begin(), E = HT.data_end(); I != E; ++I) {
276 auto *LocalPtr = I.getItem();
277
278 // FIXME: Don't rely on the OnDiskHashTable format here.
279 auto L = InfoObj.ReadKeyDataLength(LocalPtr);
280 const internal_key_type &Key = InfoObj.ReadKey(LocalPtr, L.first);
281 InfoObj.ReadDataInto(Key, LocalPtr + L.first, L.second, ResultBuilder);
282 }
283 }
284
285 return Result;
286 }
287};
288
289/// Writer for the on-disk hash table.
290template<typename ReaderInfo, typename WriterInfo>
291class MultiOnDiskHashTableGenerator {
292 using BaseTable = MultiOnDiskHashTable<ReaderInfo>;
293 using Generator = llvm::OnDiskChainedHashTableGenerator<WriterInfo>;
294
295 Generator Gen;
296
297public:
298 MultiOnDiskHashTableGenerator() : Gen() {}
299
300 void insert(typename WriterInfo::key_type_ref Key,
301 typename WriterInfo::data_type_ref Data, WriterInfo &Info) {
302 Gen.insert(Key, Data, Info);
303 }
304
305 void emit(llvm::SmallVectorImpl<char> &Out, WriterInfo &Info,
306 const BaseTable *Base) {
307 using namespace llvm::support;
308
309 llvm::raw_svector_ostream OutStream(Out);
310
311 // Write our header information.
312 {
313 endian::Writer Writer(OutStream, llvm::endianness::little);
314
315 // Reserve four bytes for the bucket offset.
316 Writer.write<uint32_t>(Val: 0);
317
318 if (auto *Merged = Base ? Base->getMergedTable() : nullptr) {
319 // Write list of overridden files.
320 Writer.write<uint32_t>(Merged->Files.size());
321 for (const auto &F : Merged->Files)
322 Info.EmitFileRef(OutStream, F);
323
324 // Add all merged entries from Base to the generator.
325 for (auto &KV : Merged->Data) {
326 if (!Gen.contains(KV.first, Info))
327 Gen.insert(KV.first, Info.ImportData(KV.second), Info);
328 }
329 } else {
330 Writer.write<uint32_t>(Val: 0);
331 }
332 }
333
334 // Write the table itself.
335 uint32_t BucketOffset = Gen.Emit(OutStream, Info);
336
337 // Replace the first four bytes with the bucket offset.
338 endian::write32le(P: Out.data(), V: BucketOffset);
339 }
340};
341
342} // namespace serialization
343} // namespace clang
344
345#endif // LLVM_CLANG_LIB_SERIALIZATION_MULTIONDISKHASHTABLE_H
346