1//===- ScopedHashTable.h - A simple scoped hash 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// This file implements an efficient scoped hash table, which is useful for
10// things like dominator-based optimizations. This allows clients to do things
11// like this:
12//
13// ScopedHashTable<int, int> HT;
14// {
15// ScopedHashTableScope<int, int> Scope1(HT);
16// HT.insert(0, 0);
17// HT.insert(1, 1);
18// {
19// ScopedHashTableScope<int, int> Scope2(HT);
20// HT.insert(0, 42);
21// }
22// }
23//
24// Looking up the value for "0" in the Scope2 block will return 42. Looking
25// up the value for 0 before 42 is inserted or after Scope2 is popped will
26// return 0.
27//
28//===----------------------------------------------------------------------===//
29
30#ifndef LLVM_ADT_SCOPEDHASHTABLE_H
31#define LLVM_ADT_SCOPEDHASHTABLE_H
32
33#include "llvm/ADT/DenseMap.h"
34#include "llvm/ADT/DenseMapInfo.h"
35#include "llvm/Support/AllocatorBase.h"
36#include <cassert>
37#include <new>
38
39namespace llvm {
40
41template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
42 typename AllocatorTy = MallocAllocator>
43class ScopedHashTable;
44
45template <typename K, typename V>
46class ScopedHashTableVal {
47 ScopedHashTableVal *NextInScope;
48 ScopedHashTableVal *NextForKey;
49 K Key;
50 V Val;
51
52 ScopedHashTableVal(const K &key, const V &val) : Key(key), Val(val) {}
53
54public:
55 const K &getKey() const { return Key; }
56 const V &getValue() const { return Val; }
57 V &getValue() { return Val; }
58
59 ScopedHashTableVal *getNextForKey() { return NextForKey; }
60 const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
61 ScopedHashTableVal *getNextInScope() { return NextInScope; }
62
63 template <typename AllocatorTy>
64 static ScopedHashTableVal *Create(ScopedHashTableVal *nextInScope,
65 ScopedHashTableVal *nextForKey,
66 const K &key, const V &val,
67 AllocatorTy &Allocator) {
68 ScopedHashTableVal *New = Allocator.template Allocate<ScopedHashTableVal>();
69 // Set up the value.
70 new (New) ScopedHashTableVal(key, val);
71 New->NextInScope = nextInScope;
72 New->NextForKey = nextForKey;
73 return New;
74 }
75
76 template <typename AllocatorTy> void Destroy(AllocatorTy &Allocator) {
77 // Free memory referenced by the item.
78 this->~ScopedHashTableVal();
79 Allocator.Deallocate(this);
80 }
81};
82
83template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
84 typename AllocatorTy = MallocAllocator>
85class ScopedHashTableScope {
86 /// HT - The hashtable that we are active for.
87 ScopedHashTable<K, V, KInfo, AllocatorTy> &HT;
88
89 /// PrevScope - This is the scope that we are shadowing in HT.
90 ScopedHashTableScope *PrevScope;
91
92 /// LastValInScope - This is the last value that was inserted for this scope
93 /// or null if none have been inserted yet.
94 ScopedHashTableVal<K, V> *LastValInScope;
95
96public:
97 ScopedHashTableScope(ScopedHashTable<K, V, KInfo, AllocatorTy> &HT);
98 ScopedHashTableScope(ScopedHashTableScope &) = delete;
99 ScopedHashTableScope &operator=(ScopedHashTableScope &) = delete;
100 ~ScopedHashTableScope();
101
102 ScopedHashTableScope *getParentScope() { return PrevScope; }
103 const ScopedHashTableScope *getParentScope() const { return PrevScope; }
104
105private:
106 friend class ScopedHashTable<K, V, KInfo, AllocatorTy>;
107
108 ScopedHashTableVal<K, V> *getLastValInScope() {
109 return LastValInScope;
110 }
111
112 void setLastValInScope(ScopedHashTableVal<K, V> *Val) {
113 LastValInScope = Val;
114 }
115};
116
117template <typename K, typename V, typename KInfo = DenseMapInfo<K>>
118class ScopedHashTableIterator {
119 ScopedHashTableVal<K, V> *Node;
120
121public:
122 ScopedHashTableIterator(ScopedHashTableVal<K, V> *node) : Node(node) {}
123
124 V &operator*() const {
125 assert(Node && "Dereference end()");
126 return Node->getValue();
127 }
128 V *operator->() const {
129 return &Node->getValue();
130 }
131
132 bool operator==(const ScopedHashTableIterator &RHS) const {
133 return Node == RHS.Node;
134 }
135 bool operator!=(const ScopedHashTableIterator &RHS) const {
136 return Node != RHS.Node;
137 }
138
139 inline ScopedHashTableIterator& operator++() { // Preincrement
140 assert(Node && "incrementing past end()");
141 Node = Node->getNextForKey();
142 return *this;
143 }
144 ScopedHashTableIterator operator++(int) { // Postincrement
145 ScopedHashTableIterator tmp = *this; ++*this; return tmp;
146 }
147};
148
149template <typename K, typename V, typename KInfo, typename AllocatorTy>
150class ScopedHashTable {
151public:
152 /// ScopeTy - This is a helpful typedef that allows clients to get easy access
153 /// to the name of the scope for this hash table.
154 using ScopeTy = ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
155 using size_type = unsigned;
156
157private:
158 friend class ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
159
160 using ValTy = ScopedHashTableVal<K, V>;
161
162 DenseMap<K, ValTy*, KInfo> TopLevelMap;
163 ScopeTy *CurScope = nullptr;
164
165 AllocatorTy Allocator;
166
167public:
168 ScopedHashTable() = default;
169 ScopedHashTable(AllocatorTy A) : Allocator(A) {}
170 ScopedHashTable(const ScopedHashTable &) = delete;
171 ScopedHashTable &operator=(const ScopedHashTable &) = delete;
172
173 ~ScopedHashTable() {
174 assert(!CurScope && TopLevelMap.empty() && "Scope imbalance!");
175 }
176
177 /// Access to the allocator.
178 AllocatorTy &getAllocator() { return Allocator; }
179 const AllocatorTy &getAllocator() const { return Allocator; }
180
181 /// Return 1 if the specified key is in the table, 0 otherwise.
182 size_type count(const K &Key) const {
183 return TopLevelMap.count(Key);
184 }
185
186 V lookup(const K &Key) const {
187 auto I = TopLevelMap.find(Key);
188 if (I != TopLevelMap.end())
189 return I->second->getValue();
190
191 return V();
192 }
193
194 void insert(const K &Key, const V &Val) {
195 insertIntoScope(CurScope, Key, Val);
196 }
197
198 using iterator = ScopedHashTableIterator<K, V, KInfo>;
199
200 iterator end() { return iterator(0); }
201
202 iterator begin(const K &Key) {
203 typename DenseMap<K, ValTy*, KInfo>::iterator I =
204 TopLevelMap.find(Key);
205 if (I == TopLevelMap.end()) return end();
206 return iterator(I->second);
207 }
208
209 ScopeTy *getCurScope() { return CurScope; }
210 const ScopeTy *getCurScope() const { return CurScope; }
211
212 /// insertIntoScope - This inserts the specified key/value at the specified
213 /// (possibly not the current) scope. While it is ok to insert into a scope
214 /// that isn't the current one, it isn't ok to insert *underneath* an existing
215 /// value of the specified key.
216 void insertIntoScope(ScopeTy *S, const K &Key, const V &Val) {
217 assert(S && "No scope active!");
218 ScopedHashTableVal<K, V> *&KeyEntry = TopLevelMap[Key];
219 KeyEntry = ValTy::Create(S->getLastValInScope(), KeyEntry, Key, Val,
220 Allocator);
221 S->setLastValInScope(KeyEntry);
222 }
223};
224
225/// ScopedHashTableScope ctor - Install this as the current scope for the hash
226/// table.
227template <typename K, typename V, typename KInfo, typename Allocator>
228ScopedHashTableScope<K, V, KInfo, Allocator>::
229 ScopedHashTableScope(ScopedHashTable<K, V, KInfo, Allocator> &ht) : HT(ht) {
230 PrevScope = HT.CurScope;
231 HT.CurScope = this;
232 LastValInScope = nullptr;
233}
234
235template <typename K, typename V, typename KInfo, typename Allocator>
236ScopedHashTableScope<K, V, KInfo, Allocator>::~ScopedHashTableScope() {
237 assert(HT.CurScope == this && "Scope imbalance!");
238 HT.CurScope = PrevScope;
239
240 // Pop and delete all values corresponding to this scope.
241 while (ScopedHashTableVal<K, V> *ThisEntry = LastValInScope) {
242 // Pop this value out of the TopLevelMap.
243 if (!ThisEntry->getNextForKey()) {
244 assert(HT.TopLevelMap[ThisEntry->getKey()] == ThisEntry &&
245 "Scope imbalance!");
246 HT.TopLevelMap.erase(ThisEntry->getKey());
247 } else {
248 ScopedHashTableVal<K, V> *&KeyEntry = HT.TopLevelMap[ThisEntry->getKey()];
249 assert(KeyEntry == ThisEntry && "Scope imbalance!");
250 KeyEntry = ThisEntry->getNextForKey();
251 }
252
253 // Pop this value out of the scope.
254 LastValInScope = ThisEntry->getNextInScope();
255
256 // Delete this entry.
257 ThisEntry->Destroy(HT.getAllocator());
258 }
259}
260
261} // end namespace llvm
262
263#endif // LLVM_ADT_SCOPEDHASHTABLE_H
264