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//===- ScopedHashTable.h - A simple scoped hash table -----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements an efficient scoped hash table, which is useful for
// things like dominator-based optimizations. This allows clients to do things
// like this:
//
// ScopedHashTable<int, int> HT;
// {
// ScopedHashTableScope<int, int> Scope1(HT);
// HT.insert(0, 0);
// HT.insert(1, 1);
// {
// ScopedHashTableScope<int, int> Scope2(HT);
// HT.insert(0, 42);
// }
// }
//
// Looking up the value for "0" in the Scope2 block will return 42. Looking
// up the value for 0 before 42 is inserted or after Scope2 is popped will
// return 0.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_SCOPEDHASHTABLE_H
#define LLVM_ADT_SCOPEDHASHTABLE_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/Support/AllocatorBase.h"
#include <cassert>
#include <new>
namespace llvm {
template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
typename AllocatorTy = MallocAllocator>
class ScopedHashTable;
template <typename K, typename V>
class ScopedHashTableVal {
ScopedHashTableVal *NextInScope;
ScopedHashTableVal *NextForKey;
K Key;
V Val;
ScopedHashTableVal(const K &key, const V &val) : Key(key), Val(val) {}
public:
const K &getKey() const { return Key; }
const V &getValue() const { return Val; }
V &getValue() { return Val; }
ScopedHashTableVal *getNextForKey() { return NextForKey; }
const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
ScopedHashTableVal *getNextInScope() { return NextInScope; }
template <typename AllocatorTy>
static ScopedHashTableVal *Create(ScopedHashTableVal *nextInScope,
ScopedHashTableVal *nextForKey,
const K &key, const V &val,
AllocatorTy &Allocator) {
ScopedHashTableVal *New = Allocator.template Allocate<ScopedHashTableVal>();
// Set up the value.
new (New) ScopedHashTableVal(key, val);
New->NextInScope = nextInScope;
New->NextForKey = nextForKey;
return New;
}
template <typename AllocatorTy> void Destroy(AllocatorTy &Allocator) {
// Free memory referenced by the item.
this->~ScopedHashTableVal();
Allocator.Deallocate(this);
}
};
template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
typename AllocatorTy = MallocAllocator>
class ScopedHashTableScope {
/// HT - The hashtable that we are active for.
ScopedHashTable<K, V, KInfo, AllocatorTy> &HT;
/// PrevScope - This is the scope that we are shadowing in HT.
ScopedHashTableScope *PrevScope;
/// LastValInScope - This is the last value that was inserted for this scope
/// or null if none have been inserted yet.
ScopedHashTableVal<K, V> *LastValInScope;
public:
ScopedHashTableScope(ScopedHashTable<K, V, KInfo, AllocatorTy> &HT);
ScopedHashTableScope(ScopedHashTableScope &) = delete;
ScopedHashTableScope &operator=(ScopedHashTableScope &) = delete;
~ScopedHashTableScope();
ScopedHashTableScope *getParentScope() { return PrevScope; }
const ScopedHashTableScope *getParentScope() const { return PrevScope; }
private:
friend class ScopedHashTable<K, V, KInfo, AllocatorTy>;
ScopedHashTableVal<K, V> *getLastValInScope() {
return LastValInScope;
}
void setLastValInScope(ScopedHashTableVal<K, V> *Val) {
LastValInScope = Val;
}
};
template <typename K, typename V, typename KInfo = DenseMapInfo<K>>
class ScopedHashTableIterator {
ScopedHashTableVal<K, V> *Node;
public:
ScopedHashTableIterator(ScopedHashTableVal<K, V> *node) : Node(node) {}
V &operator*() const {
assert(Node && "Dereference end()");
return Node->getValue();
}
V *operator->() const {
return &Node->getValue();
}
bool operator==(const ScopedHashTableIterator &RHS) const {
return Node == RHS.Node;
}
bool operator!=(const ScopedHashTableIterator &RHS) const {
return Node != RHS.Node;
}
inline ScopedHashTableIterator& operator++() { // Preincrement
assert(Node && "incrementing past end()");
Node = Node->getNextForKey();
return *this;
}
ScopedHashTableIterator operator++(int) { // Postincrement
ScopedHashTableIterator tmp = *this; ++*this; return tmp;
}
};
template <typename K, typename V, typename KInfo, typename AllocatorTy>
class ScopedHashTable : detail::AllocatorHolder<AllocatorTy> {
using AllocTy = detail::AllocatorHolder<AllocatorTy>;
public:
/// ScopeTy - This is a helpful typedef that allows clients to get easy access
/// to the name of the scope for this hash table.
using ScopeTy = ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
using size_type = unsigned;
private:
friend class ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
using ValTy = ScopedHashTableVal<K, V>;
DenseMap<K, ValTy*, KInfo> TopLevelMap;
ScopeTy *CurScope = nullptr;
public:
ScopedHashTable() = default;
ScopedHashTable(AllocatorTy A) : AllocTy(A) {}
ScopedHashTable(const ScopedHashTable &) = delete;
ScopedHashTable &operator=(const ScopedHashTable &) = delete;
~ScopedHashTable() {
assert(!CurScope && TopLevelMap.empty() && "Scope imbalance!");
}
/// Access to the allocator.
using AllocTy::getAllocator;
/// Return 1 if the specified key is in the table, 0 otherwise.
size_type count(const K &Key) const {
return TopLevelMap.count(Key);
}
V lookup(const K &Key) const {
auto I = TopLevelMap.find(Key);
if (I != TopLevelMap.end())
return I->second->getValue();
return V();
}
void insert(const K &Key, const V &Val) {
insertIntoScope(CurScope, Key, Val);
}
using iterator = ScopedHashTableIterator<K, V, KInfo>;
iterator end() { return iterator(nullptr); }
iterator begin(const K &Key) {
typename DenseMap<K, ValTy*, KInfo>::iterator I =
TopLevelMap.find(Key);
if (I == TopLevelMap.end()) return end();
return iterator(I->second);
}
ScopeTy *getCurScope() { return CurScope; }
const ScopeTy *getCurScope() const { return CurScope; }
/// insertIntoScope - This inserts the specified key/value at the specified
/// (possibly not the current) scope. While it is ok to insert into a scope
/// that isn't the current one, it isn't ok to insert *underneath* an existing
/// value of the specified key.
void insertIntoScope(ScopeTy *S, const K &Key, const V &Val) {
assert(S && "No scope active!");
ScopedHashTableVal<K, V> *&KeyEntry = TopLevelMap[Key];
KeyEntry = ValTy::Create(S->getLastValInScope(), KeyEntry, Key, Val,
getAllocator());
S->setLastValInScope(KeyEntry);
}
};
/// ScopedHashTableScope ctor - Install this as the current scope for the hash
/// table.
template <typename K, typename V, typename KInfo, typename Allocator>
ScopedHashTableScope<K, V, KInfo, Allocator>::
ScopedHashTableScope(ScopedHashTable<K, V, KInfo, Allocator> &ht) : HT(ht) {
PrevScope = HT.CurScope;
HT.CurScope = this;
LastValInScope = nullptr;
}
template <typename K, typename V, typename KInfo, typename Allocator>
ScopedHashTableScope<K, V, KInfo, Allocator>::~ScopedHashTableScope() {
assert(HT.CurScope == this && "Scope imbalance!");
HT.CurScope = PrevScope;
// Pop and delete all values corresponding to this scope.
while (ScopedHashTableVal<K, V> *ThisEntry = LastValInScope) {
// Pop this value out of the TopLevelMap.
if (!ThisEntry->getNextForKey()) {
assert(HT.TopLevelMap[ThisEntry->getKey()] == ThisEntry &&
"Scope imbalance!");
HT.TopLevelMap.erase(ThisEntry->getKey());
} else {
ScopedHashTableVal<K, V> *&KeyEntry = HT.TopLevelMap[ThisEntry->getKey()];
assert(KeyEntry == ThisEntry && "Scope imbalance!");
KeyEntry = ThisEntry->getNextForKey();
}
// Pop this value out of the scope.
LastValInScope = ThisEntry->getNextInScope();
// Delete this entry.
ThisEntry->Destroy(HT.getAllocator());
}
}
} // end namespace llvm
#endif // LLVM_ADT_SCOPEDHASHTABLE_H
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