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//==-- llvm/ADT/ilist.h - Intrusive Linked List Template ---------*- 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 classes to implement an intrusive doubly linked list class
// (i.e. each node of the list must contain a next and previous field for the
// list.
// The ilist_traits trait class is used to gain access to the next and previous
// fields of the node type that the list is instantiated with. If it is not
// specialized, the list defaults to using the getPrev(), getNext() method calls
// to get the next and previous pointers.
// The ilist class itself, should be a plug in replacement for list, assuming
// that the nodes contain next/prev pointers. This list replacement does not
// provide a constant time size() method, so be careful to use empty() when you
// really want to know if it's empty.
// The ilist class is implemented by allocating a 'tail' node when the list is
// created (using ilist_traits<>::createSentinel()). This tail node is
// absolutely required because the user must be able to compute end()-1. Because
// of this, users of the direct next/prev links will see an extra link on the
// end of the list, which should be ignored.
// Requirements for a user of this list:
// 1. The user must provide {g|s}et{Next|Prev} methods, or specialize
// ilist_traits to provide an alternate way of getting and setting next and
// prev links.
#include "llvm/Support/Compiler.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <iterator>
namespace llvm {
template<typename NodeTy, typename Traits> class iplist;
template<typename NodeTy> class ilist_iterator;
/// ilist_nextprev_traits - A fragment for template traits for intrusive list
/// that provides default next/prev implementations for common operations.
template<typename NodeTy>
struct ilist_nextprev_traits {
static NodeTy *getPrev(NodeTy *N) { return N->getPrev(); }
static NodeTy *getNext(NodeTy *N) { return N->getNext(); }
static const NodeTy *getPrev(const NodeTy *N) { return N->getPrev(); }
static const NodeTy *getNext(const NodeTy *N) { return N->getNext(); }
static void setPrev(NodeTy *N, NodeTy *Prev) { N->setPrev(Prev); }
static void setNext(NodeTy *N, NodeTy *Next) { N->setNext(Next); }
template<typename NodeTy>
struct ilist_traits;
/// ilist_sentinel_traits - A fragment for template traits for intrusive list
/// that provides default sentinel implementations for common operations.
/// ilist_sentinel_traits implements a lazy dynamic sentinel allocation
/// strategy. The sentinel is stored in the prev field of ilist's Head.
template<typename NodeTy>
struct ilist_sentinel_traits {
/// createSentinel - create the dynamic sentinel
static NodeTy *createSentinel() { return new NodeTy(); }
/// destroySentinel - deallocate the dynamic sentinel
static void destroySentinel(NodeTy *N) { delete N; }
/// provideInitialHead - when constructing an ilist, provide a starting
/// value for its Head
/// @return null node to indicate that it needs to be allocated later
static NodeTy *provideInitialHead() { return nullptr; }
/// ensureHead - make sure that Head is either already
/// initialized or assigned a fresh sentinel
/// @return the sentinel
static NodeTy *ensureHead(NodeTy *&Head) {
if (!Head) {
Head = ilist_traits<NodeTy>::createSentinel();
ilist_traits<NodeTy>::noteHead(Head, Head);
ilist_traits<NodeTy>::setNext(Head, nullptr);
return Head;
return ilist_traits<NodeTy>::getPrev(Head);
/// noteHead - stash the sentinel into its default location
static void noteHead(NodeTy *NewHead, NodeTy *Sentinel) {
ilist_traits<NodeTy>::setPrev(NewHead, Sentinel);
/// ilist_node_traits - A fragment for template traits for intrusive list
/// that provides default node related operations.
template<typename NodeTy>
struct ilist_node_traits {
static NodeTy *createNode(const NodeTy &V) { return new NodeTy(V); }
static void deleteNode(NodeTy *V) { delete V; }
void addNodeToList(NodeTy *) {}
void removeNodeFromList(NodeTy *) {}
void transferNodesFromList(ilist_node_traits & /*SrcTraits*/,
ilist_iterator<NodeTy> /*first*/,
ilist_iterator<NodeTy> /*last*/) {}
/// ilist_default_traits - Default template traits for intrusive list.
/// By inheriting from this, you can easily use default implementations
/// for all common operations.
template<typename NodeTy>
struct ilist_default_traits : public ilist_nextprev_traits<NodeTy>,
public ilist_sentinel_traits<NodeTy>,
public ilist_node_traits<NodeTy> {
// Template traits for intrusive list. By specializing this template class, you
// can change what next/prev fields are used to store the links...
template<typename NodeTy>
struct ilist_traits : public ilist_default_traits<NodeTy> {};
// Const traits are the same as nonconst traits...
template<typename Ty>
struct ilist_traits<const Ty> : public ilist_traits<Ty> {};
// ilist_iterator<Node> - Iterator for intrusive list.
template<typename NodeTy>
class ilist_iterator
: public std::iterator<std::bidirectional_iterator_tag, NodeTy, ptrdiff_t> {
typedef ilist_traits<NodeTy> Traits;
typedef std::iterator<std::bidirectional_iterator_tag,
NodeTy, ptrdiff_t> super;
typedef typename super::value_type value_type;
typedef typename super::difference_type difference_type;
typedef typename super::pointer pointer;
typedef typename super::reference reference;
pointer NodePtr;
// ilist_iterator is not a random-access iterator, but it has an
// implicit conversion to pointer-type, which is. Declare (but
// don't define) these functions as private to help catch
// accidental misuse.
void operator[](difference_type) const;
void operator+(difference_type) const;
void operator-(difference_type) const;
void operator+=(difference_type) const;
void operator-=(difference_type) const;
template<class T> void operator<(T) const;
template<class T> void operator<=(T) const;
template<class T> void operator>(T) const;
template<class T> void operator>=(T) const;
template<class T> void operator-(T) const;
ilist_iterator(pointer NP) : NodePtr(NP) {}
ilist_iterator(reference NR) : NodePtr(&NR) {}
ilist_iterator() : NodePtr(nullptr) {}
// This is templated so that we can allow constructing a const iterator from
// a nonconst iterator...
template<class node_ty>
ilist_iterator(const ilist_iterator<node_ty> &RHS)
: NodePtr(RHS.getNodePtrUnchecked()) {}
// This is templated so that we can allow assigning to a const iterator from
// a nonconst iterator...
template<class node_ty>
const ilist_iterator &operator=(const ilist_iterator<node_ty> &RHS) {
NodePtr = RHS.getNodePtrUnchecked();
return *this;
// Accessors...
operator pointer() const {
return NodePtr;
reference operator*() const {
return *NodePtr;
pointer operator->() const { return &operator*(); }
// Comparison operators
bool operator==(const ilist_iterator &RHS) const {
return NodePtr == RHS.NodePtr;
bool operator!=(const ilist_iterator &RHS) const {
return NodePtr != RHS.NodePtr;
// Increment and decrement operators...
ilist_iterator &operator--() { // predecrement - Back up
NodePtr = Traits::getPrev(NodePtr);
assert(NodePtr && "--'d off the beginning of an ilist!");
return *this;
ilist_iterator &operator++() { // preincrement - Advance
NodePtr = Traits::getNext(NodePtr);
return *this;
ilist_iterator operator--(int) { // postdecrement operators...
ilist_iterator tmp = *this;
return tmp;
ilist_iterator operator++(int) { // postincrement operators...
ilist_iterator tmp = *this;
return tmp;
// Internal interface, do not use...
pointer getNodePtrUnchecked() const { return NodePtr; }
// These are to catch errors when people try to use them as random access
// iterators.
template<typename T>
void operator-(int, ilist_iterator<T>) LLVM_DELETED_FUNCTION;
template<typename T>
void operator-(ilist_iterator<T>,int) LLVM_DELETED_FUNCTION;
template<typename T>
void operator+(int, ilist_iterator<T>) LLVM_DELETED_FUNCTION;
template<typename T>
void operator+(ilist_iterator<T>,int) LLVM_DELETED_FUNCTION;
// operator!=/operator== - Allow mixed comparisons without dereferencing
// the iterator, which could very likely be pointing to end().
template<typename T>
bool operator!=(const T* LHS, const ilist_iterator<const T> &RHS) {
return LHS != RHS.getNodePtrUnchecked();
template<typename T>
bool operator==(const T* LHS, const ilist_iterator<const T> &RHS) {
return LHS == RHS.getNodePtrUnchecked();
template<typename T>
bool operator!=(T* LHS, const ilist_iterator<T> &RHS) {
return LHS != RHS.getNodePtrUnchecked();
template<typename T>
bool operator==(T* LHS, const ilist_iterator<T> &RHS) {
return LHS == RHS.getNodePtrUnchecked();
// Allow ilist_iterators to convert into pointers to a node automatically when
// used by the dyn_cast, cast, isa mechanisms...
template<typename From> struct simplify_type;
template<typename NodeTy> struct simplify_type<ilist_iterator<NodeTy> > {
typedef NodeTy* SimpleType;
static SimpleType getSimplifiedValue(ilist_iterator<NodeTy> &Node) {
return &*Node;
template<typename NodeTy> struct simplify_type<const ilist_iterator<NodeTy> > {
typedef /*const*/ NodeTy* SimpleType;
static SimpleType getSimplifiedValue(const ilist_iterator<NodeTy> &Node) {
return &*Node;
/// iplist - The subset of list functionality that can safely be used on nodes
/// of polymorphic types, i.e. a heterogeneous list with a common base class that
/// holds the next/prev pointers. The only state of the list itself is a single
/// pointer to the head of the list.
/// This list can be in one of three interesting states:
/// 1. The list may be completely unconstructed. In this case, the head
/// pointer is null. When in this form, any query for an iterator (e.g.
/// begin() or end()) causes the list to transparently change to state #2.
/// 2. The list may be empty, but contain a sentinel for the end iterator. This
/// sentinel is created by the Traits::createSentinel method and is a link
/// in the list. When the list is empty, the pointer in the iplist points
/// to the sentinel. Once the sentinel is constructed, it
/// is not destroyed until the list is.
/// 3. The list may contain actual objects in it, which are stored as a doubly
/// linked list of nodes. One invariant of the list is that the predecessor
/// of the first node in the list always points to the last node in the list,
/// and the successor pointer for the sentinel (which always stays at the
/// end of the list) is always null.
template<typename NodeTy, typename Traits=ilist_traits<NodeTy> >
class iplist : public Traits {
mutable NodeTy *Head;
// Use the prev node pointer of 'head' as the tail pointer. This is really a
// circularly linked list where we snip the 'next' link from the sentinel node
// back to the first node in the list (to preserve assertions about going off
// the end of the list).
NodeTy *getTail() { return this->ensureHead(Head); }
const NodeTy *getTail() const { return this->ensureHead(Head); }
void setTail(NodeTy *N) const { this->noteHead(Head, N); }
/// CreateLazySentinel - This method verifies whether the sentinel for the
/// list has been created and lazily makes it if not.
void CreateLazySentinel() const {
static bool op_less(NodeTy &L, NodeTy &R) { return L < R; }
static bool op_equal(NodeTy &L, NodeTy &R) { return L == R; }
// No fundamental reason why iplist can't be copyable, but the default
// copy/copy-assign won't do.
iplist(const iplist &) LLVM_DELETED_FUNCTION;
void operator=(const iplist &) LLVM_DELETED_FUNCTION;
typedef NodeTy *pointer;
typedef const NodeTy *const_pointer;
typedef NodeTy &reference;
typedef const NodeTy &const_reference;
typedef NodeTy value_type;
typedef ilist_iterator<NodeTy> iterator;
typedef ilist_iterator<const NodeTy> const_iterator;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
typedef std::reverse_iterator<iterator> reverse_iterator;
iplist() : Head(this->provideInitialHead()) {}
~iplist() {
if (!Head) return;
// Iterator creation methods.
iterator begin() {
return iterator(Head);
const_iterator begin() const {
return const_iterator(Head);
iterator end() {
return iterator(getTail());
const_iterator end() const {
return const_iterator(getTail());
// reverse iterator creation methods.
reverse_iterator rbegin() { return reverse_iterator(end()); }
const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); }
reverse_iterator rend() { return reverse_iterator(begin()); }
const_reverse_iterator rend() const { return const_reverse_iterator(begin());}
// Miscellaneous inspection routines.
size_type max_size() const { return size_type(-1); }
return !Head || Head == getTail();
// Front and back accessor functions...
reference front() {
assert(!empty() && "Called front() on empty list!");
return *Head;
const_reference front() const {
assert(!empty() && "Called front() on empty list!");
return *Head;
reference back() {
assert(!empty() && "Called back() on empty list!");
return *this->getPrev(getTail());
const_reference back() const {
assert(!empty() && "Called back() on empty list!");
return *this->getPrev(getTail());
void swap(iplist &RHS) {
assert(0 && "Swap does not use list traits callback correctly yet!");
std::swap(Head, RHS.Head);
iterator insert(iterator where, NodeTy *New) {
NodeTy *CurNode = where.getNodePtrUnchecked();
NodeTy *PrevNode = this->getPrev(CurNode);
this->setNext(New, CurNode);
this->setPrev(New, PrevNode);
if (CurNode != Head) // Is PrevNode off the beginning of the list?
this->setNext(PrevNode, New);
Head = New;
this->setPrev(CurNode, New);
this->addNodeToList(New); // Notify traits that we added a node...
return New;
iterator insertAfter(iterator where, NodeTy *New) {
if (empty())
return insert(begin(), New);
return insert(++where, New);
NodeTy *remove(iterator &IT) {
assert(IT != end() && "Cannot remove end of list!");
NodeTy *Node = &*IT;
NodeTy *NextNode = this->getNext(Node);
NodeTy *PrevNode = this->getPrev(Node);
if (Node != Head) // Is PrevNode off the beginning of the list?
this->setNext(PrevNode, NextNode);
Head = NextNode;
this->setPrev(NextNode, PrevNode);
IT = NextNode;
this->removeNodeFromList(Node); // Notify traits that we removed a node...
// Set the next/prev pointers of the current node to null. This isn't
// strictly required, but this catches errors where a node is removed from
// an ilist (and potentially deleted) with iterators still pointing at it.
// When those iterators are incremented or decremented, they will assert on
// the null next/prev pointer instead of "usually working".
this->setNext(Node, nullptr);
this->setPrev(Node, nullptr);
return Node;
NodeTy *remove(const iterator &IT) {
iterator MutIt = IT;
return remove(MutIt);
// erase - remove a node from the controlled sequence... and delete it.
iterator erase(iterator where) {
return where;
/// Remove all nodes from the list like clear(), but do not call
/// removeNodeFromList() or deleteNode().
/// This should only be used immediately before freeing nodes in bulk to
/// avoid traversing the list and bringing all the nodes into cache.
void clearAndLeakNodesUnsafely() {
if (Head) {
Head = getTail();
this->setPrev(Head, Head);
// transfer - The heart of the splice function. Move linked list nodes from
// [first, last) into position.
void transfer(iterator position, iplist &L2, iterator first, iterator last) {
assert(first != last && "Should be checked by callers");
// Position cannot be contained in the range to be transferred.
// Check for the most common mistake.
assert(position != first &&
"Insertion point can't be one of the transferred nodes");
if (position != last) {
// Note: we have to be careful about the case when we move the first node
// in the list. This node is the list sentinel node and we can't move it.
NodeTy *ThisSentinel = getTail();
NodeTy *L2Sentinel = L2.getTail();
// Remove [first, last) from its old position.
NodeTy *First = &*first, *Prev = this->getPrev(First);
NodeTy *Next = last.getNodePtrUnchecked(), *Last = this->getPrev(Next);
if (Prev)
this->setNext(Prev, Next);
L2.Head = Next;
this->setPrev(Next, Prev);
// Splice [first, last) into its new position.
NodeTy *PosNext = position.getNodePtrUnchecked();
NodeTy *PosPrev = this->getPrev(PosNext);
// Fix head of list...
if (PosPrev)
this->setNext(PosPrev, First);
Head = First;
this->setPrev(First, PosPrev);
// Fix end of list...
this->setNext(Last, PosNext);
this->setPrev(PosNext, Last);
this->transferNodesFromList(L2, First, PosNext);
// Now that everything is set, restore the pointers to the list sentinels.
// Functionality derived from other functions defined above...
size_type LLVM_ATTRIBUTE_UNUSED_RESULT size() const {
if (!Head) return 0; // Don't require construction of sentinel if empty.
return std::distance(begin(), end());
iterator erase(iterator first, iterator last) {
while (first != last)
first = erase(first);
return last;
void clear() { if (Head) erase(begin(), end()); }
// Front and back inserters...
void push_front(NodeTy *val) { insert(begin(), val); }
void push_back(NodeTy *val) { insert(end(), val); }
void pop_front() {
assert(!empty() && "pop_front() on empty list!");
void pop_back() {
assert(!empty() && "pop_back() on empty list!");
iterator t = end(); erase(--t);
// Special forms of insert...
template<class InIt> void insert(iterator where, InIt first, InIt last) {
for (; first != last; ++first) insert(where, *first);
// Splice members - defined in terms of transfer...
void splice(iterator where, iplist &L2) {
if (!L2.empty())
transfer(where, L2, L2.begin(), L2.end());
void splice(iterator where, iplist &L2, iterator first) {
iterator last = first; ++last;
if (where == first || where == last) return; // No change
transfer(where, L2, first, last);
void splice(iterator where, iplist &L2, iterator first, iterator last) {
if (first != last) transfer(where, L2, first, last);
// High-Level Functionality that shouldn't really be here, but is part of list
// These two functions are actually called remove/remove_if in list<>, but
// they actually do the job of erase, rename them accordingly.
void erase(const NodeTy &val) {
for (iterator I = begin(), E = end(); I != E; ) {
iterator next = I; ++next;
if (*I == val) erase(I);
I = next;
template<class Pr1> void erase_if(Pr1 pred) {
for (iterator I = begin(), E = end(); I != E; ) {
iterator next = I; ++next;
if (pred(*I)) erase(I);
I = next;
template<class Pr2> void unique(Pr2 pred) {
if (empty()) return;
for (iterator I = begin(), E = end(), Next = begin(); ++Next != E;) {
if (pred(*I))
I = Next;
Next = I;
void unique() { unique(op_equal); }
template<class Pr3> void merge(iplist &right, Pr3 pred) {
iterator first1 = begin(), last1 = end();
iterator first2 = right.begin(), last2 = right.end();
while (first1 != last1 && first2 != last2)
if (pred(*first2, *first1)) {
iterator next = first2;
transfer(first1, right, first2, ++next);
first2 = next;
} else {
if (first2 != last2) transfer(last1, right, first2, last2);
void merge(iplist &right) { return merge(right, op_less); }
template<class Pr3> void sort(Pr3 pred);
void sort() { sort(op_less); }
template<typename NodeTy>
struct ilist : public iplist<NodeTy> {
typedef typename iplist<NodeTy>::size_type size_type;
typedef typename iplist<NodeTy>::iterator iterator;
ilist() {}
ilist(const ilist &right) {
insert(this->begin(), right.begin(), right.end());
explicit ilist(size_type count) {
insert(this->begin(), count, NodeTy());
ilist(size_type count, const NodeTy &val) {
insert(this->begin(), count, val);
template<class InIt> ilist(InIt first, InIt last) {
insert(this->begin(), first, last);
// bring hidden functions into scope
using iplist<NodeTy>::insert;
using iplist<NodeTy>::push_front;
using iplist<NodeTy>::push_back;
// Main implementation here - Insert for a node passed by value...
iterator insert(iterator where, const NodeTy &val) {
return insert(where, this->createNode(val));
// Front and back inserters...
void push_front(const NodeTy &val) { insert(this->begin(), val); }
void push_back(const NodeTy &val) { insert(this->end(), val); }
void insert(iterator where, size_type count, const NodeTy &val) {
for (; count != 0; --count) insert(where, val);
// Assign special forms...
void assign(size_type count, const NodeTy &val) {
iterator I = this->begin();
for (; I != this->end() && count != 0; ++I, --count)
*I = val;
if (count != 0)
insert(this->end(), val, val);
erase(I, this->end());
template<class InIt> void assign(InIt first1, InIt last1) {
iterator first2 = this->begin(), last2 = this->end();
for ( ; first1 != last1 && first2 != last2; ++first1, ++first2)
*first1 = *first2;
if (first2 == last2)
erase(first1, last1);
insert(last1, first2, last2);
// Resize members...
void resize(size_type newsize, NodeTy val) {
iterator i = this->begin();
size_type len = 0;
for ( ; i != this->end() && len < newsize; ++i, ++len) /* empty*/ ;
if (len == newsize)
erase(i, this->end());
else // i == end()
insert(this->end(), newsize - len, val);
void resize(size_type newsize) { resize(newsize, NodeTy()); }
} // End llvm namespace
namespace std {
// Ensure that swap uses the fast list swap...
template<class Ty>
void swap(llvm::iplist<Ty> &Left, llvm::iplist<Ty> &Right) {
} // End 'std' extensions...
#endif // LLVM_ADT_ILIST_H