llvm-6502/include/llvm/ADT/DenseMap.h
Jakob Stoklund Olesen b843d9f833 Optimize empty DenseMap iteration.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103962 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 20:01:24 +00:00

509 lines
16 KiB
C++

//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the DenseMap class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_DENSEMAP_H
#define LLVM_ADT_DENSEMAP_H
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/PointerLikeTypeTraits.h"
#include "llvm/Support/type_traits.h"
#include "llvm/ADT/DenseMapInfo.h"
#include <iterator>
#include <new>
#include <utility>
#include <cassert>
#include <cstring>
namespace llvm {
template<typename KeyT, typename ValueT,
typename KeyInfoT = DenseMapInfo<KeyT>,
typename ValueInfoT = DenseMapInfo<ValueT>, bool IsConst = false>
class DenseMapIterator;
template<typename KeyT, typename ValueT,
typename KeyInfoT = DenseMapInfo<KeyT>,
typename ValueInfoT = DenseMapInfo<ValueT> >
class DenseMap {
typedef std::pair<KeyT, ValueT> BucketT;
unsigned NumBuckets;
BucketT *Buckets;
unsigned NumEntries;
unsigned NumTombstones;
public:
typedef KeyT key_type;
typedef ValueT mapped_type;
typedef BucketT value_type;
DenseMap(const DenseMap &other) {
NumBuckets = 0;
CopyFrom(other);
}
explicit DenseMap(unsigned NumInitBuckets = 64) {
init(NumInitBuckets);
}
template<typename InputIt>
DenseMap(const InputIt &I, const InputIt &E) {
init(64);
insert(I, E);
}
~DenseMap() {
const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
!KeyInfoT::isEqual(P->first, TombstoneKey))
P->second.~ValueT();
P->first.~KeyT();
}
#ifndef NDEBUG
memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets);
#endif
operator delete(Buckets);
}
typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
typedef DenseMapIterator<KeyT, ValueT,
KeyInfoT, ValueInfoT, true> const_iterator;
inline iterator begin() {
// When the map is empty, avoid the overhead of AdvancePastEmptyBuckets().
return empty() ? end() : iterator(Buckets, Buckets+NumBuckets);
}
inline iterator end() {
return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
}
inline const_iterator begin() const {
return empty() ? end() : const_iterator(Buckets, Buckets+NumBuckets);
}
inline const_iterator end() const {
return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
}
bool empty() const { return NumEntries == 0; }
unsigned size() const { return NumEntries; }
/// Grow the densemap so that it has at least Size buckets. Does not shrink
void resize(size_t Size) { grow(Size); }
void clear() {
if (NumEntries == 0 && NumTombstones == 0) return;
// If the capacity of the array is huge, and the # elements used is small,
// shrink the array.
if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
shrink_and_clear();
return;
}
const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
if (!KeyInfoT::isEqual(P->first, EmptyKey)) {
if (!KeyInfoT::isEqual(P->first, TombstoneKey)) {
P->second.~ValueT();
--NumEntries;
}
P->first = EmptyKey;
}
}
assert(NumEntries == 0 && "Node count imbalance!");
NumTombstones = 0;
}
/// count - Return true if the specified key is in the map.
bool count(const KeyT &Val) const {
BucketT *TheBucket;
return LookupBucketFor(Val, TheBucket);
}
iterator find(const KeyT &Val) {
BucketT *TheBucket;
if (LookupBucketFor(Val, TheBucket))
return iterator(TheBucket, Buckets+NumBuckets);
return end();
}
const_iterator find(const KeyT &Val) const {
BucketT *TheBucket;
if (LookupBucketFor(Val, TheBucket))
return const_iterator(TheBucket, Buckets+NumBuckets);
return end();
}
/// lookup - Return the entry for the specified key, or a default
/// constructed value if no such entry exists.
ValueT lookup(const KeyT &Val) const {
BucketT *TheBucket;
if (LookupBucketFor(Val, TheBucket))
return TheBucket->second;
return ValueT();
}
// Inserts key,value pair into the map if the key isn't already in the map.
// If the key is already in the map, it returns false and doesn't update the
// value.
std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {
BucketT *TheBucket;
if (LookupBucketFor(KV.first, TheBucket))
return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
false); // Already in map.
// Otherwise, insert the new element.
TheBucket = InsertIntoBucket(KV.first, KV.second, TheBucket);
return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
true);
}
/// insert - Range insertion of pairs.
template<typename InputIt>
void insert(InputIt I, InputIt E) {
for (; I != E; ++I)
insert(*I);
}
bool erase(const KeyT &Val) {
BucketT *TheBucket;
if (!LookupBucketFor(Val, TheBucket))
return false; // not in map.
TheBucket->second.~ValueT();
TheBucket->first = getTombstoneKey();
--NumEntries;
++NumTombstones;
return true;
}
bool erase(iterator I) {
BucketT *TheBucket = &*I;
TheBucket->second.~ValueT();
TheBucket->first = getTombstoneKey();
--NumEntries;
++NumTombstones;
return true;
}
void swap(DenseMap& RHS) {
std::swap(NumBuckets, RHS.NumBuckets);
std::swap(Buckets, RHS.Buckets);
std::swap(NumEntries, RHS.NumEntries);
std::swap(NumTombstones, RHS.NumTombstones);
}
value_type& FindAndConstruct(const KeyT &Key) {
BucketT *TheBucket;
if (LookupBucketFor(Key, TheBucket))
return *TheBucket;
return *InsertIntoBucket(Key, ValueT(), TheBucket);
}
ValueT &operator[](const KeyT &Key) {
return FindAndConstruct(Key).second;
}
DenseMap& operator=(const DenseMap& other) {
CopyFrom(other);
return *this;
}
/// isPointerIntoBucketsArray - Return true if the specified pointer points
/// somewhere into the DenseMap's array of buckets (i.e. either to a key or
/// value in the DenseMap).
bool isPointerIntoBucketsArray(const void *Ptr) const {
return Ptr >= Buckets && Ptr < Buckets+NumBuckets;
}
/// getPointerIntoBucketsArray() - Return an opaque pointer into the buckets
/// array. In conjunction with the previous method, this can be used to
/// determine whether an insertion caused the DenseMap to reallocate.
const void *getPointerIntoBucketsArray() const { return Buckets; }
private:
void CopyFrom(const DenseMap& other) {
if (NumBuckets != 0 &&
(!isPodLike<KeyInfoT>::value || !isPodLike<ValueInfoT>::value)) {
const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
!KeyInfoT::isEqual(P->first, TombstoneKey))
P->second.~ValueT();
P->first.~KeyT();
}
}
NumEntries = other.NumEntries;
NumTombstones = other.NumTombstones;
if (NumBuckets) {
#ifndef NDEBUG
memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets);
#endif
operator delete(Buckets);
}
Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT) *
other.NumBuckets));
if (isPodLike<KeyInfoT>::value && isPodLike<ValueInfoT>::value)
memcpy(Buckets, other.Buckets, other.NumBuckets * sizeof(BucketT));
else
for (size_t i = 0; i < other.NumBuckets; ++i) {
new (&Buckets[i].first) KeyT(other.Buckets[i].first);
if (!KeyInfoT::isEqual(Buckets[i].first, getEmptyKey()) &&
!KeyInfoT::isEqual(Buckets[i].first, getTombstoneKey()))
new (&Buckets[i].second) ValueT(other.Buckets[i].second);
}
NumBuckets = other.NumBuckets;
}
BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
BucketT *TheBucket) {
// If the load of the hash table is more than 3/4, or if fewer than 1/8 of
// the buckets are empty (meaning that many are filled with tombstones),
// grow the table.
//
// The later case is tricky. For example, if we had one empty bucket with
// tons of tombstones, failing lookups (e.g. for insertion) would have to
// probe almost the entire table until it found the empty bucket. If the
// table completely filled with tombstones, no lookup would ever succeed,
// causing infinite loops in lookup.
++NumEntries;
if (NumEntries*4 >= NumBuckets*3 ||
NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
this->grow(NumBuckets * 2);
LookupBucketFor(Key, TheBucket);
}
// If we are writing over a tombstone, remember this.
if (!KeyInfoT::isEqual(TheBucket->first, getEmptyKey()))
--NumTombstones;
TheBucket->first = Key;
new (&TheBucket->second) ValueT(Value);
return TheBucket;
}
static unsigned getHashValue(const KeyT &Val) {
return KeyInfoT::getHashValue(Val);
}
static const KeyT getEmptyKey() {
return KeyInfoT::getEmptyKey();
}
static const KeyT getTombstoneKey() {
return KeyInfoT::getTombstoneKey();
}
/// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
/// FoundBucket. If the bucket contains the key and a value, this returns
/// true, otherwise it returns a bucket with an empty marker or tombstone and
/// returns false.
bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
unsigned BucketNo = getHashValue(Val);
unsigned ProbeAmt = 1;
BucketT *BucketsPtr = Buckets;
// FoundTombstone - Keep track of whether we find a tombstone while probing.
BucketT *FoundTombstone = 0;
const KeyT EmptyKey = getEmptyKey();
const KeyT TombstoneKey = getTombstoneKey();
assert(!KeyInfoT::isEqual(Val, EmptyKey) &&
!KeyInfoT::isEqual(Val, TombstoneKey) &&
"Empty/Tombstone value shouldn't be inserted into map!");
while (1) {
BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
// Found Val's bucket? If so, return it.
if (KeyInfoT::isEqual(ThisBucket->first, Val)) {
FoundBucket = ThisBucket;
return true;
}
// If we found an empty bucket, the key doesn't exist in the set.
// Insert it and return the default value.
if (KeyInfoT::isEqual(ThisBucket->first, EmptyKey)) {
// If we've already seen a tombstone while probing, fill it in instead
// of the empty bucket we eventually probed to.
if (FoundTombstone) ThisBucket = FoundTombstone;
FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
return false;
}
// If this is a tombstone, remember it. If Val ends up not in the map, we
// prefer to return it than something that would require more probing.
if (KeyInfoT::isEqual(ThisBucket->first, TombstoneKey) && !FoundTombstone)
FoundTombstone = ThisBucket; // Remember the first tombstone found.
// Otherwise, it's a hash collision or a tombstone, continue quadratic
// probing.
BucketNo += ProbeAmt++;
}
}
void init(unsigned InitBuckets) {
NumEntries = 0;
NumTombstones = 0;
NumBuckets = InitBuckets;
assert(InitBuckets && (InitBuckets & (InitBuckets-1)) == 0 &&
"# initial buckets must be a power of two!");
Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*InitBuckets));
// Initialize all the keys to EmptyKey.
const KeyT EmptyKey = getEmptyKey();
for (unsigned i = 0; i != InitBuckets; ++i)
new (&Buckets[i].first) KeyT(EmptyKey);
}
void grow(unsigned AtLeast) {
unsigned OldNumBuckets = NumBuckets;
BucketT *OldBuckets = Buckets;
// Double the number of buckets.
while (NumBuckets < AtLeast)
NumBuckets <<= 1;
NumTombstones = 0;
Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets));
// Initialize all the keys to EmptyKey.
const KeyT EmptyKey = getEmptyKey();
for (unsigned i = 0, e = NumBuckets; i != e; ++i)
new (&Buckets[i].first) KeyT(EmptyKey);
// Insert all the old elements.
const KeyT TombstoneKey = getTombstoneKey();
for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
if (!KeyInfoT::isEqual(B->first, EmptyKey) &&
!KeyInfoT::isEqual(B->first, TombstoneKey)) {
// Insert the key/value into the new table.
BucketT *DestBucket;
bool FoundVal = LookupBucketFor(B->first, DestBucket);
FoundVal = FoundVal; // silence warning.
assert(!FoundVal && "Key already in new map?");
DestBucket->first = B->first;
new (&DestBucket->second) ValueT(B->second);
// Free the value.
B->second.~ValueT();
}
B->first.~KeyT();
}
#ifndef NDEBUG
memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets);
#endif
// Free the old table.
operator delete(OldBuckets);
}
void shrink_and_clear() {
unsigned OldNumBuckets = NumBuckets;
BucketT *OldBuckets = Buckets;
// Reduce the number of buckets.
NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1)
: 64;
NumTombstones = 0;
Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets));
// Initialize all the keys to EmptyKey.
const KeyT EmptyKey = getEmptyKey();
for (unsigned i = 0, e = NumBuckets; i != e; ++i)
new (&Buckets[i].first) KeyT(EmptyKey);
// Free the old buckets.
const KeyT TombstoneKey = getTombstoneKey();
for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
if (!KeyInfoT::isEqual(B->first, EmptyKey) &&
!KeyInfoT::isEqual(B->first, TombstoneKey)) {
// Free the value.
B->second.~ValueT();
}
B->first.~KeyT();
}
#ifndef NDEBUG
memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets);
#endif
// Free the old table.
operator delete(OldBuckets);
NumEntries = 0;
}
};
template<typename KeyT, typename ValueT,
typename KeyInfoT, typename ValueInfoT, bool IsConst>
class DenseMapIterator {
typedef std::pair<KeyT, ValueT> Bucket;
typedef DenseMapIterator<KeyT, ValueT,
KeyInfoT, ValueInfoT, true> ConstIterator;
friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, ValueInfoT, true>;
public:
typedef ptrdiff_t difference_type;
typedef typename conditional<IsConst, const Bucket, Bucket>::type value_type;
typedef value_type *pointer;
typedef value_type &reference;
typedef std::forward_iterator_tag iterator_category;
private:
pointer Ptr, End;
public:
DenseMapIterator() : Ptr(0), End(0) {}
DenseMapIterator(pointer Pos, pointer E) : Ptr(Pos), End(E) {
AdvancePastEmptyBuckets();
}
// If IsConst is true this is a converting constructor from iterator to
// const_iterator and the default copy constructor is used.
// Otherwise this is a copy constructor for iterator.
DenseMapIterator(const DenseMapIterator<KeyT, ValueT,
KeyInfoT, ValueInfoT, false>& I)
: Ptr(I.Ptr), End(I.End) {}
reference operator*() const {
return *Ptr;
}
pointer operator->() const {
return Ptr;
}
bool operator==(const ConstIterator &RHS) const {
return Ptr == RHS.operator->();
}
bool operator!=(const ConstIterator &RHS) const {
return Ptr != RHS.operator->();
}
inline DenseMapIterator& operator++() { // Preincrement
++Ptr;
AdvancePastEmptyBuckets();
return *this;
}
DenseMapIterator operator++(int) { // Postincrement
DenseMapIterator tmp = *this; ++*this; return tmp;
}
private:
void AdvancePastEmptyBuckets() {
const KeyT Empty = KeyInfoT::getEmptyKey();
const KeyT Tombstone = KeyInfoT::getTombstoneKey();
while (Ptr != End &&
(KeyInfoT::isEqual(Ptr->first, Empty) ||
KeyInfoT::isEqual(Ptr->first, Tombstone)))
++Ptr;
}
};
} // end namespace llvm
#endif