[llvm] r278974 - ADT: Remove UB in ilist (and use a circular linked list)
Diana Picus via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 19 03:27:57 PDT 2016
Hi Duncan,
Sorry about that, our machines are currently a bit busy bisecting
another bot failure / running tests for the release candidate. As soon
as those are done, I'll give it a run.
Thanks,
Diana
On 19 August 2016 at 03:14, Duncan P. N. Exon Smith
<dexonsmith at apple.com> wrote:
> Hi Diana, any update? Are you able to test pre-commit, or should I just commit and let the bots do the work?
>
>> On 2016-Aug-18, at 11:09, Duncan P. N. Exon Smith via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>
>> Hi Diana,
>>
>> I fixed PR29035 in r279104. Are you able to test that revision with r278974 cherry-picked on top to be sure the assertion isn't firing elsewhere?
>>
>> Thanks,
>> Duncan
>>
>>> On 2016-Aug-18, at 06:19, Duncan Exon Smith via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>>
>>> Please attach the reproducer mentioned in the log message:
>>>
>>> clang-4.0: note: diagnostic msg: PLEASE submit a bug report to http://llvm.org/bugs/ and include the crash backtrace, preprocessed source, and associated run script.
>>> clang-4.0: note: diagnostic msg:
>>> ********************
>>> PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
>>> Preprocessed source(s) and associated run script(s) are located at:
>>> clang-4.0: note: diagnostic msg: /tmp/gtest-all-78e9e5.cpp
>>> clang-4.0: note: diagnostic msg: /tmp/gtest-all-78e9e5.sh
>>> clang-4.0: note: diagnostic msg:
>>> ********************
>>>
>>> -- dpnes
>>>
>>> On Aug 18, 2016, at 04:32, Diana Picus <diana.picus at linaro.org> wrote:
>>>
>>>> Hi,
>>>>
>>>> I had to revert this because it was breaking some of the bots. I also
>>>> reverted r279012 because it was in the way (and it looked like a fixup
>>>> for this revision anyway).
>>>> I've attached a log of the failure to this bug:
>>>> https://llvm.org/bugs/show_bug.cgi?id=29035
>>>> Please let me know if you need anything else to debug this.
>>>>
>>>> Thanks,
>>>> Diana
>>>>
>>>>
>>>>
>>>> On 17 August 2016 at 23:44, Duncan P. N. Exon Smith via llvm-commits
>>>> <llvm-commits at lists.llvm.org> wrote:
>>>>> Author: dexonsmith
>>>>> Date: Wed Aug 17 15:44:33 2016
>>>>> New Revision: 278974
>>>>>
>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=278974&view=rev
>>>>> Log:
>>>>> ADT: Remove UB in ilist (and use a circular linked list)
>>>>>
>>>>> This removes the undefined behaviour (UB) in ilist/ilist_node/etc.,
>>>>> mainly by removing (gutting) the ilist_sentinel_traits customization
>>>>> point and canonicalizing on a single, efficient memory layout. This
>>>>> fixes PR26753.
>>>>>
>>>>> The new ilist is a doubly-linked circular list.
>>>>> - ilist_node_base has two ilist_node_base*: Next and Prev. Size-of: two
>>>>> pointers.
>>>>> - ilist_node<T> (size-of: two pointers) is a type-safe wrapper around
>>>>> ilist_node_base.
>>>>> - ilist_iterator<T> (size-of: two pointers) operates on an
>>>>> ilist_node<T>*, and downcasts to T* on dereference.
>>>>> - ilist_sentinel<T> (size-of: two pointers) is a wrapper around
>>>>> ilist_node<T> that has some extra API for list management.
>>>>> - ilist<T> (size-of: two pointers) has an ilist_sentinel<T>, whose
>>>>> address is returned for end().
>>>>>
>>>>> The new memory layout matches ilist_half_embedded_sentinel_traits<T>
>>>>> exactly. The Head pointer that previously lived in ilist<T> is
>>>>> effectively glued to the ilist_half_node<T> that lived in
>>>>> ilist_half_embedded_sentinel_traits<T>, becoming the Next and Prev in
>>>>> the ilist_sentinel_node<T>, respectively. sizeof(ilist<T>) is now the
>>>>> size of two pointers, and there is never any additional storage for a
>>>>> sentinel.
>>>>>
>>>>> This is a much simpler design for a doubly-linked list, removing most of
>>>>> the corner cases of list manipulation (add, remove, etc.). In follow-up
>>>>> commits, I intend to move as many algorithms as possible into a
>>>>> non-templated base class (ilist_base) to reduce code size.
>>>>>
>>>>> Moreover, this fixes the UB in ilist_iterator/getNext/getPrev
>>>>> operations. Previously, ilist_iterator<T> operated on a T*, even when
>>>>> the sentinel was not of type T (i.e., ilist_embedded_sentinel_traits and
>>>>> ilist_half_embedded_sentinel_traits). This added UB to all operations
>>>>> involving end(). Now, ilist_iterator<T> operates on an ilist_node<T>*,
>>>>> and only downcasts when the full type is guaranteed to be T*.
>>>>>
>>>>> What did we lose? There used to be a crash (in some configurations) on
>>>>> ++end(). Curiously (via UB), ++end() would return begin() for users of
>>>>> ilist_half_embedded_sentinel_traits<T>, but otherwise ++end() would
>>>>> cause a nice dependable nullptr dereference, crashing instead of a
>>>>> possible infinite loop. Options:
>>>>> 1. Lose that behaviour.
>>>>> 2. Keep it, by stealing a bit from Prev in asserts builds.
>>>>> 3. Crash on dereference instead, using the same technique.
>>>>>
>>>>> Hans convinced me (because of the number of problems this and r278532
>>>>> exposed on Windows) that we really need some assertion here, at least in
>>>>> the short term. I've opted for #3 since I think it catches more bugs.
>>>>>
>>>>> I added only a couple of unit tests to root out specific bugs I hit
>>>>> during bring-up, but otherwise this is tested implicitly via the
>>>>> extensive usage throughout LLVM.
>>>>>
>>>>> Planned follow-ups:
>>>>> - Remove ilist_*sentinel_traits<T>. Here I've just gutted them to
>>>>> prevent build failures in sub-projects. Once I stop referring to them
>>>>> in sub-projects, I'll come back and delete them.
>>>>> - Add ilist_base and move algorithms there.
>>>>> - Check and fix move construction and assignment.
>>>>>
>>>>> Eventually, there are other interesting directions:
>>>>> - Rewrite reverse iterators, so that rbegin().getNodePtr()==&*rbegin().
>>>>> This allows much simpler logic when erasing elements during a reverse
>>>>> traversal.
>>>>> - Remove ilist_traits::createNode, by deleting the remaining API that
>>>>> creates nodes. Intrusive lists shouldn't be creating nodes
>>>>> themselves.
>>>>> - Remove ilist_traits::deleteNode, by (1) asserting that lists are empty
>>>>> on destruction and (2) changing API that calls it to take a Deleter
>>>>> functor (intrusive lists shouldn't be in the memory management
>>>>> business).
>>>>> - Reconfigure the remaining callback traits (addNodeToList, etc.) to be
>>>>> higher-level, pulling out a simple_ilist<T> that is much easier to
>>>>> read and understand.
>>>>> - Allow tags (e.g., ilist_node<T,tag1> and ilist_node<T,tag2>) so that T
>>>>> can be a member of multiple intrusive lists.
>>>>>
>>>>> Modified:
>>>>> llvm/trunk/include/llvm/ADT/ilist.h
>>>>> llvm/trunk/include/llvm/ADT/ilist_node.h
>>>>> llvm/trunk/unittests/ADT/ilistTest.cpp
>>>>>
>>>>> Modified: llvm/trunk/include/llvm/ADT/ilist.h
>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/ilist.h?rev=278974&r1=278973&r2=278974&view=diff
>>>>> ==============================================================================
>>>>> --- llvm/trunk/include/llvm/ADT/ilist.h (original)
>>>>> +++ llvm/trunk/include/llvm/ADT/ilist.h Wed Aug 17 15:44:33 2016
>>>>> @@ -15,17 +15,16 @@
>>>>> // 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.
>>>>> +// The ilist class is implemented as a circular list. The list itself contains
>>>>> +// a sentinel node, whose Next points at begin() and whose Prev points at
>>>>> +// rbegin(). The sentinel node itself serves as end() and rend().
>>>>> //
>>>>> //===----------------------------------------------------------------------===//
>>>>>
>>>>> #ifndef LLVM_ADT_ILIST_H
>>>>> #define LLVM_ADT_ILIST_H
>>>>>
>>>>> +#include "llvm/ADT/ilist_node.h"
>>>>> #include "llvm/Support/Compiler.h"
>>>>> #include <algorithm>
>>>>> #include <cassert>
>>>>> @@ -38,37 +37,42 @@ namespace llvm {
>>>>> template<typename NodeTy, typename Traits> class iplist;
>>>>> template<typename NodeTy> class ilist_iterator;
>>>>>
>>>>> -/// An access class for next/prev on ilist_nodes.
>>>>> +/// An access class for ilist_node private API.
>>>>> ///
>>>>> /// This gives access to the private parts of ilist nodes. Nodes for an ilist
>>>>> /// should friend this class if they inherit privately from ilist_node.
>>>>> ///
>>>>> -/// It's strongly discouraged to *use* this class outside of ilist
>>>>> +/// It's strongly discouraged to *use* this class outside of the ilist
>>>>> /// implementation.
>>>>> struct ilist_node_access {
>>>>> - template <typename NodeTy> static NodeTy *getPrev(NodeTy *N) {
>>>>> + template <typename T> static ilist_node<T> *getNodePtr(T *N) { return N; }
>>>>> + template <typename T> static const ilist_node<T> *getNodePtr(const T *N) {
>>>>> + return N;
>>>>> + }
>>>>> +
>>>>> + template <typename T> static ilist_node<T> *getPrev(ilist_node<T> *N) {
>>>>> return N->getPrev();
>>>>> }
>>>>> - template <typename NodeTy> static NodeTy *getNext(NodeTy *N) {
>>>>> + template <typename T> static ilist_node<T> *getNext(ilist_node<T> *N) {
>>>>> return N->getNext();
>>>>> }
>>>>> - template <typename NodeTy> static const NodeTy *getPrev(const NodeTy *N) {
>>>>> + template <typename T> static const ilist_node<T> *getPrev(const ilist_node<T> *N) {
>>>>> return N->getPrev();
>>>>> }
>>>>> - template <typename NodeTy> static const NodeTy *getNext(const NodeTy *N) {
>>>>> + template <typename T> static const ilist_node<T> *getNext(const ilist_node<T> *N) {
>>>>> return N->getNext();
>>>>> }
>>>>>
>>>>> - template <typename NodeTy> static void setPrev(NodeTy *N, NodeTy *Prev) {
>>>>> + template <typename T> static void setPrev(ilist_node<T> *N, ilist_node<T> *Prev) {
>>>>> N->setPrev(Prev);
>>>>> }
>>>>> - template <typename NodeTy> static void setNext(NodeTy *N, NodeTy *Next) {
>>>>> + template <typename T> static void setNext(ilist_node<T> *N, ilist_node<T> *Next) {
>>>>> N->setNext(Next);
>>>>> }
>>>>> - template <typename NodeTy> static void setPrev(NodeTy *N, std::nullptr_t) {
>>>>> + template <typename T> static void setPrev(ilist_node<T> *N, std::nullptr_t) {
>>>>> N->setPrev(nullptr);
>>>>> }
>>>>> - template <typename NodeTy> static void setNext(NodeTy *N, std::nullptr_t) {
>>>>> + template <typename T> static void setNext(ilist_node<T> *N, std::nullptr_t) {
>>>>> N->setNext(nullptr);
>>>>> }
>>>>> };
>>>>> @@ -93,111 +97,31 @@ template <class TraitsT, class NodeT> st
>>>>> static const bool value = sizeof(hasGetNext<TraitsT>(nullptr)) == sizeof(Yes);
>>>>> };
>>>>>
>>>>> -} // end namespace ilist_detail
>>>>> -
>>>>> -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_node_access::setNext(Head, nullptr);
>>>>> - return Head;
>>>>> - }
>>>>> - return ilist_node_access::getPrev(Head);
>>>>> - }
>>>>> -
>>>>> - /// noteHead - stash the sentinel into its default location
>>>>> - static void noteHead(NodeTy *NewHead, NodeTy *Sentinel) {
>>>>> - ilist_node_access::setPrev(NewHead, Sentinel);
>>>>> - }
>>>>> -};
>>>>> -
>>>>> -template <typename NodeTy> class ilist_half_node;
>>>>> -template <typename NodeTy> class ilist_node;
>>>>> +/// Type trait to check for a traits class that has a createSentinel member (as
>>>>> +/// a canary for any of the ilist_sentinel_traits API).
>>>>> +template <class TraitsT> struct HasCreateSentinel {
>>>>> + typedef char Yes[1];
>>>>> + typedef char No[2];
>>>>> + template <size_t N> struct SFINAE {};
>>>>>
>>>>> -/// Traits with an embedded ilist_node as a sentinel.
>>>>> -template <typename NodeTy> struct ilist_embedded_sentinel_traits {
>>>>> - /// Get hold of the node that marks the end of the list.
>>>>> - ///
>>>>> - /// FIXME: This downcast is UB. See llvm.org/PR26753.
>>>>> - LLVM_NO_SANITIZE("object-size")
>>>>> - NodeTy *createSentinel() const {
>>>>> - // Since i(p)lists always publicly derive from their corresponding traits,
>>>>> - // placing a data member in this class will augment the i(p)list. But since
>>>>> - // the NodeTy is expected to be publicly derive from ilist_node<NodeTy>,
>>>>> - // there is a legal viable downcast from it to NodeTy. We use this trick to
>>>>> - // superimpose an i(p)list with a "ghostly" NodeTy, which becomes the
>>>>> - // sentinel. Dereferencing the sentinel is forbidden (save the
>>>>> - // ilist_node<NodeTy>), so no one will ever notice the superposition.
>>>>> - return static_cast<NodeTy *>(&Sentinel);
>>>>> - }
>>>>> - static void destroySentinel(NodeTy *) {}
>>>>> -
>>>>> - NodeTy *provideInitialHead() const { return createSentinel(); }
>>>>> - NodeTy *ensureHead(NodeTy *) const { return createSentinel(); }
>>>>> - static void noteHead(NodeTy *, NodeTy *) {}
>>>>> + template <class U>
>>>>> + static Yes &
>>>>> + hasCreateSentinel(SFINAE<sizeof(make<U>().createSentinel())> * = 0);
>>>>> + template <class U> static No &hasCreateSentinel(...);
>>>>>
>>>>> -private:
>>>>> - mutable ilist_node<NodeTy> Sentinel;
>>>>> + static const bool value =
>>>>> + sizeof(hasCreateSentinel<TraitsT>(nullptr)) == sizeof(Yes);
>>>>> };
>>>>>
>>>>> -/// Trait with an embedded ilist_half_node as a sentinel.
>>>>> -template <typename NodeTy> struct ilist_half_embedded_sentinel_traits {
>>>>> - /// Get hold of the node that marks the end of the list.
>>>>> - ///
>>>>> - /// FIXME: This downcast is UB. See llvm.org/PR26753.
>>>>> - LLVM_NO_SANITIZE("object-size")
>>>>> - NodeTy *createSentinel() const {
>>>>> - // See comment in ilist_embedded_sentinel_traits::createSentinel().
>>>>> - return static_cast<NodeTy *>(&Sentinel);
>>>>> - }
>>>>> - static void destroySentinel(NodeTy *) {}
>>>>> -
>>>>> - NodeTy *provideInitialHead() const { return createSentinel(); }
>>>>> - NodeTy *ensureHead(NodeTy *) const { return createSentinel(); }
>>>>> - static void noteHead(NodeTy *, NodeTy *) {}
>>>>> -
>>>>> -private:
>>>>> - mutable ilist_half_node<NodeTy> Sentinel;
>>>>> -};
>>>>> +} // end namespace ilist_detail
>>>>>
>>>>> -/// Traits with an embedded full node as a sentinel.
>>>>> -template <typename NodeTy> struct ilist_full_embedded_sentinel_traits {
>>>>> - /// Get hold of the node that marks the end of the list.
>>>>> - NodeTy *createSentinel() const { return &Sentinel; }
>>>>> - static void destroySentinel(NodeTy *) {}
>>>>> -
>>>>> - NodeTy *provideInitialHead() const { return createSentinel(); }
>>>>> - NodeTy *ensureHead(NodeTy *) const { return createSentinel(); }
>>>>> - static void noteHead(NodeTy *, NodeTy *) {}
>>>>> +template <typename NodeTy> struct ilist_traits;
>>>>>
>>>>> -private:
>>>>> - mutable NodeTy Sentinel;
>>>>> -};
>>>>> +// TODO: Delete uses from subprojects, then delete these.
>>>>> +template <typename NodeTy> struct ilist_sentinel_traits {};
>>>>> +template <typename NodeTy> struct ilist_embedded_sentinel_traits {};
>>>>> +template <typename NodeTy> struct ilist_half_embedded_sentinel_traits {};
>>>>> +template <typename NodeTy> struct ilist_full_embedded_sentinel_traits {};
>>>>>
>>>>> /// ilist_node_traits - A fragment for template traits for intrusive list
>>>>> /// that provides default node related operations.
>>>>> @@ -219,8 +143,7 @@ struct ilist_node_traits {
>>>>> /// for all common operations.
>>>>> ///
>>>>> template <typename NodeTy>
>>>>> -struct ilist_default_traits : public ilist_sentinel_traits<NodeTy>,
>>>>> - public ilist_node_traits<NodeTy> {};
>>>>> +struct ilist_default_traits : 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...
>>>>> @@ -263,16 +186,15 @@ public:
>>>>> typedef node_type &node_reference;
>>>>>
>>>>> private:
>>>>> - pointer NodePtr;
>>>>> + node_pointer NodePtr = nullptr;
>>>>>
>>>>> public:
>>>>> /// Create from an ilist_node.
>>>>> - explicit ilist_iterator(node_reference N)
>>>>> - : NodePtr(static_cast<NodeTy *>(&N)) {}
>>>>> + explicit ilist_iterator(node_reference N) : NodePtr(&N) {}
>>>>>
>>>>> explicit ilist_iterator(pointer NP) : NodePtr(NP) {}
>>>>> explicit ilist_iterator(reference NR) : NodePtr(&NR) {}
>>>>> - ilist_iterator() : NodePtr(nullptr) {}
>>>>> + ilist_iterator() = default;
>>>>>
>>>>> // This is templated so that we can allow constructing a const iterator from
>>>>> // a nonconst iterator...
>>>>> @@ -281,20 +203,23 @@ public:
>>>>> const ilist_iterator<node_ty> &RHS,
>>>>> typename std::enable_if<std::is_convertible<node_ty *, NodeTy *>::value,
>>>>> void *>::type = nullptr)
>>>>> - : NodePtr(RHS.getNodePtrUnchecked()) {}
>>>>> + : NodePtr(RHS.getNodePtr()) {}
>>>>>
>>>>> // 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();
>>>>> + NodePtr = RHS.getNodePtr();
>>>>> return *this;
>>>>> }
>>>>>
>>>>> void reset(pointer NP) { NodePtr = NP; }
>>>>>
>>>>> // Accessors...
>>>>> - reference operator*() const { return *NodePtr; }
>>>>> + reference operator*() const {
>>>>> + assert(!NodePtr->isKnownSentinel());
>>>>> + return static_cast<NodeTy &>(*getNodePtr());
>>>>> + }
>>>>> pointer operator->() const { return &operator*(); }
>>>>>
>>>>> // Comparison operators
>>>>> @@ -328,9 +253,6 @@ public:
>>>>>
>>>>> /// Get the underlying ilist_node.
>>>>> node_pointer getNodePtr() const { return static_cast<node_pointer>(NodePtr); }
>>>>> -
>>>>> - // Internal interface, do not use...
>>>>> - pointer getNodePtrUnchecked() const { return NodePtr; }
>>>>> };
>>>>>
>>>>> // Allow ilist_iterators to convert into pointers to a node automatically when
>>>>> @@ -356,56 +278,33 @@ template<typename NodeTy> struct simplif
>>>>>
>>>>> //===----------------------------------------------------------------------===//
>>>>> //
>>>>> -/// 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.
>>>>> -///
>>>>> +/// 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 an
>>>>> +/// ilist_sentinel, which holds pointers to the first and last nodes in the
>>>>> +/// list.
>>>>> template <typename NodeTy, typename Traits = ilist_traits<NodeTy>>
>>>>> class iplist : public Traits, ilist_node_access {
>>>>> + // TODO: Drop these assertions anytime after 4.0 is branched (keep them for
>>>>> + // one release to help out-of-tree code update).
>>>>> #if !defined(_MSC_VER)
>>>>> // FIXME: This fails in MSVC, but it's worth keeping around to help
>>>>> // non-Windows users root out bugs in their ilist_traits.
>>>>> static_assert(!ilist_detail::HasGetNext<Traits, NodeTy>::value,
>>>>> "ilist next and prev links are not customizable!");
>>>>> + static_assert(!ilist_detail::HasCreateSentinel<Traits>::value,
>>>>> + "ilist sentinel is not customizable!");
>>>>> #endif
>>>>>
>>>>> - mutable NodeTy *Head;
>>>>> + ilist_sentinel<NodeTy> Sentinel;
>>>>>
>>>>> - // 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 {
>>>>> - this->ensureHead(Head);
>>>>> - }
>>>>> + typedef ilist_node<NodeTy> node_type;
>>>>> + typedef const ilist_node<NodeTy> const_node_type;
>>>>>
>>>>> 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.
>>>>> + // Copying intrusively linked nodes doesn't make sense.
>>>>> iplist(const iplist &) = delete;
>>>>> void operator=(const iplist &) = delete;
>>>>>
>>>>> @@ -422,30 +321,14 @@ public:
>>>>> typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
>>>>> typedef std::reverse_iterator<iterator> reverse_iterator;
>>>>>
>>>>> - iplist() : Head(this->provideInitialHead()) {}
>>>>> - ~iplist() {
>>>>> - if (!Head) return;
>>>>> - clear();
>>>>> - Traits::destroySentinel(getTail());
>>>>> - }
>>>>> + iplist() = default;
>>>>> + ~iplist() { clear(); }
>>>>>
>>>>> // Iterator creation methods.
>>>>> - iterator begin() {
>>>>> - CreateLazySentinel();
>>>>> - return iterator(Head);
>>>>> - }
>>>>> - const_iterator begin() const {
>>>>> - CreateLazySentinel();
>>>>> - return const_iterator(Head);
>>>>> - }
>>>>> - iterator end() {
>>>>> - CreateLazySentinel();
>>>>> - return iterator(getTail());
>>>>> - }
>>>>> - const_iterator end() const {
>>>>> - CreateLazySentinel();
>>>>> - return const_iterator(getTail());
>>>>> - }
>>>>> + iterator begin() { return ++iterator(Sentinel); }
>>>>> + const_iterator begin() const { return ++const_iterator(Sentinel); }
>>>>> + iterator end() { return iterator(Sentinel); }
>>>>> + const_iterator end() const { return const_iterator(Sentinel); }
>>>>>
>>>>> // reverse iterator creation methods.
>>>>> reverse_iterator rbegin() { return reverse_iterator(end()); }
>>>>> @@ -456,44 +339,39 @@ public:
>>>>>
>>>>> // Miscellaneous inspection routines.
>>>>> size_type max_size() const { return size_type(-1); }
>>>>> - bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const {
>>>>> - return !Head || Head == getTail();
>>>>> - }
>>>>> + bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { return Sentinel.empty(); }
>>>>>
>>>>> // Front and back accessor functions...
>>>>> reference front() {
>>>>> assert(!empty() && "Called front() on empty list!");
>>>>> - return *Head;
>>>>> + return *begin();
>>>>> }
>>>>> const_reference front() const {
>>>>> assert(!empty() && "Called front() on empty list!");
>>>>> - return *Head;
>>>>> + return *begin();
>>>>> }
>>>>> reference back() {
>>>>> assert(!empty() && "Called back() on empty list!");
>>>>> - return *this->getPrev(getTail());
>>>>> + return *--end();
>>>>> }
>>>>> const_reference back() const {
>>>>> assert(!empty() && "Called back() on empty list!");
>>>>> - return *this->getPrev(getTail());
>>>>> + return *--end();
>>>>> }
>>>>>
>>>>> void swap(iplist &RHS) {
>>>>> assert(0 && "Swap does not use list traits callback correctly yet!");
>>>>> - std::swap(Head, RHS.Head);
>>>>> + std::swap(Sentinel, RHS.Sentinel);
>>>>> }
>>>>>
>>>>> 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);
>>>>> - else
>>>>> - Head = New;
>>>>> - this->setPrev(CurNode, New);
>>>>> + node_type *NewN = this->getNodePtr(New);
>>>>> + node_type *Next = where.getNodePtr();
>>>>> + node_type *Prev = this->getPrev(Next);
>>>>> + this->setNext(NewN, Next);
>>>>> + this->setPrev(NewN, Prev);
>>>>> + this->setNext(Prev, NewN);
>>>>> + this->setPrev(Next, NewN);
>>>>>
>>>>> this->addNodeToList(New); // Notify traits that we added a node...
>>>>> return iterator(New);
>>>>> @@ -513,24 +391,23 @@ public:
>>>>> 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);
>>>>> - else
>>>>> - Head = NextNode;
>>>>> - this->setPrev(NextNode, PrevNode);
>>>>> - IT.reset(NextNode);
>>>>> + node_type *Base = this->getNodePtr(Node);
>>>>> + node_type *Next = this->getNext(Base);
>>>>> + node_type *Prev = this->getPrev(Base);
>>>>> +
>>>>> + this->setNext(Prev, Next);
>>>>> + this->setPrev(Next, Prev);
>>>>> + IT = iterator(*Next);
>>>>> 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);
>>>>> + // After those iterators are incremented or decremented, they become
>>>>> + // default-constructed iterators, and will assert on increment, decrement,
>>>>> + // and dereference instead of "usually working".
>>>>> + this->setNext(Base, nullptr);
>>>>> + this->setPrev(Base, nullptr);
>>>>> return Node;
>>>>> }
>>>>>
>>>>> @@ -556,12 +433,7 @@ public:
>>>>> ///
>>>>> /// 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);
>>>>> - }
>>>>> - }
>>>>> + void clearAndLeakNodesUnsafely() { Sentinel.reset(); }
>>>>>
>>>>> private:
>>>>> // transfer - The heart of the splice function. Move linked list nodes from
>>>>> @@ -570,48 +442,34 @@ private:
>>>>> 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 &&
>>>>> + // Check for the most common mistake.
>>>>> "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();
>>>>> - setTail(nullptr);
>>>>> - NodeTy *L2Sentinel = L2.getTail();
>>>>> - L2.setTail(nullptr);
>>>>> -
>>>>> - // 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);
>>>>> - else
>>>>> - 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);
>>>>> - else
>>>>> - Head = First;
>>>>> - this->setPrev(First, PosPrev);
>>>>> -
>>>>> - // Fix end of list...
>>>>> - this->setNext(Last, PosNext);
>>>>> - this->setPrev(PosNext, Last);
>>>>> -
>>>>> - this->transferNodesFromList(L2, iterator(First), iterator(PosNext));
>>>>> -
>>>>> - // Now that everything is set, restore the pointers to the list sentinels.
>>>>> - L2.setTail(L2Sentinel);
>>>>> - setTail(ThisSentinel);
>>>>> - }
>>>>> + if (position == last)
>>>>> + return;
>>>>> +
>>>>> + // Get raw hooks to the first and final nodes being transferred.
>>>>> + node_type *First = first.getNodePtr();
>>>>> + node_type *Final = (--last).getNodePtr();
>>>>> +
>>>>> + // Detach from old list/position.
>>>>> + node_type *Prev = this->getPrev(First);
>>>>> + node_type *Next = this->getNext(Final);
>>>>> + this->setNext(Prev, Next);
>>>>> + this->setPrev(Next, Prev);
>>>>> +
>>>>> + // Splice [First, Final] into its new list/position.
>>>>> + Next = position.getNodePtr();
>>>>> + Prev = this->getPrev(Next);
>>>>> + this->setNext(Final, Next);
>>>>> + this->setPrev(First, Prev);
>>>>> + this->setNext(Prev, First);
>>>>> + this->setPrev(Next, Final);
>>>>> +
>>>>> + // Callback. Note that the nodes have moved from before-last to
>>>>> + // before-position.
>>>>> + this->transferNodesFromList(L2, first, position);
>>>>> }
>>>>>
>>>>> public:
>>>>> @@ -621,7 +479,6 @@ public:
>>>>> //
>>>>>
>>>>> 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());
>>>>> }
>>>>>
>>>>> @@ -631,7 +488,7 @@ public:
>>>>> return last;
>>>>> }
>>>>>
>>>>> - void clear() { if (Head) erase(begin(), end()); }
>>>>> + void clear() { erase(begin(), end()); }
>>>>>
>>>>> // Front and back inserters...
>>>>> void push_front(NodeTy *val) { insert(begin(), val); }
>>>>>
>>>>> Modified: llvm/trunk/include/llvm/ADT/ilist_node.h
>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/ilist_node.h?rev=278974&r1=278973&r2=278974&view=diff
>>>>> ==============================================================================
>>>>> --- llvm/trunk/include/llvm/ADT/ilist_node.h (original)
>>>>> +++ llvm/trunk/include/llvm/ADT/ilist_node.h Wed Aug 17 15:44:33 2016
>>>>> @@ -15,6 +15,8 @@
>>>>> #ifndef LLVM_ADT_ILIST_NODE_H
>>>>> #define LLVM_ADT_ILIST_NODE_H
>>>>>
>>>>> +#include <llvm/ADT/PointerIntPair.h>
>>>>> +
>>>>> namespace llvm {
>>>>>
>>>>> template<typename NodeTy>
>>>>> @@ -22,46 +24,81 @@ struct ilist_traits;
>>>>> template <typename NodeTy> struct ilist_embedded_sentinel_traits;
>>>>> template <typename NodeTy> struct ilist_half_embedded_sentinel_traits;
>>>>>
>>>>> -/// ilist_half_node - Base class that provides prev services for sentinels.
>>>>> -///
>>>>> -template<typename NodeTy>
>>>>> -class ilist_half_node {
>>>>> - friend struct ilist_traits<NodeTy>;
>>>>> - friend struct ilist_half_embedded_sentinel_traits<NodeTy>;
>>>>> - NodeTy *Prev;
>>>>> -protected:
>>>>> - NodeTy *getPrev() { return Prev; }
>>>>> - const NodeTy *getPrev() const { return Prev; }
>>>>> - void setPrev(NodeTy *P) { Prev = P; }
>>>>> - ilist_half_node() : Prev(nullptr) {}
>>>>> +/// Base class for ilist nodes.
>>>>> +struct ilist_node_base {
>>>>> +#ifdef LLVM_ENABLE_ABI_BREAKING_CHECKS
>>>>> + PointerIntPair<ilist_node_base *, 1> PrevAndSentinel;
>>>>> +
>>>>> + void setPrev(ilist_node_base *Prev) { PrevAndSentinel.setPointer(Prev); }
>>>>> + ilist_node_base *getPrev() const { return PrevAndSentinel.getPointer(); }
>>>>> +
>>>>> + bool isKnownSentinel() const { return PrevAndSentinel.getInt(); }
>>>>> + void initializeSentinel() { PrevAndSentinel.setInt(true); }
>>>>> +#else
>>>>> + ilist_node_base *Prev = nullptr;
>>>>> +
>>>>> + void setPrev(ilist_node_base *Prev) { this->Prev = Prev; }
>>>>> + ilist_node_base *getPrev() const { return Prev; }
>>>>> +
>>>>> + bool isKnownSentinel() const { return false; }
>>>>> + void initializeSentinel() {}
>>>>> +#endif
>>>>> +
>>>>> + ilist_node_base *Next = nullptr;
>>>>> };
>>>>>
>>>>> struct ilist_node_access;
>>>>> template <typename NodeTy> class ilist_iterator;
>>>>> +template <typename NodeTy> class ilist_sentinel;
>>>>>
>>>>> -/// Base class that provides next/prev services for ilist nodes.
>>>>> -template<typename NodeTy>
>>>>> -class ilist_node : private ilist_half_node<NodeTy> {
>>>>> +/// Templated wrapper class.
>>>>> +template <typename NodeTy> class ilist_node : ilist_node_base {
>>>>> friend struct ilist_node_access;
>>>>> friend struct ilist_traits<NodeTy>;
>>>>> friend struct ilist_half_embedded_sentinel_traits<NodeTy>;
>>>>> friend struct ilist_embedded_sentinel_traits<NodeTy>;
>>>>> - NodeTy *Next;
>>>>> - NodeTy *getNext() { return Next; }
>>>>> - const NodeTy *getNext() const { return Next; }
>>>>> - void setNext(NodeTy *N) { Next = N; }
>>>>> + friend class ilist_iterator<NodeTy>;
>>>>> + friend class ilist_sentinel<NodeTy>;
>>>>> +
>>>>> protected:
>>>>> - ilist_node() : Next(nullptr) {}
>>>>> + ilist_node() = default;
>>>>>
>>>>> -public:
>>>>> - ilist_iterator<NodeTy> getIterator() {
>>>>> - // FIXME: Stop downcasting to create the iterator (potential UB).
>>>>> - return ilist_iterator<NodeTy>(static_cast<NodeTy *>(this));
>>>>> +private:
>>>>> + ilist_node *getPrev() {
>>>>> + return static_cast<ilist_node *>(ilist_node_base::getPrev());
>>>>> + }
>>>>> + ilist_node *getNext() { return static_cast<ilist_node *>(Next); }
>>>>> +
>>>>> + const ilist_node *getPrev() const {
>>>>> + return static_cast<ilist_node *>(ilist_node_base::getPrev());
>>>>> }
>>>>> + const ilist_node *getNext() const { return static_cast<ilist_node *>(Next); }
>>>>> +
>>>>> + void setPrev(ilist_node *N) { ilist_node_base::setPrev(N); }
>>>>> + void setNext(ilist_node *N) { Next = N; }
>>>>> +
>>>>> +public:
>>>>> + ilist_iterator<NodeTy> getIterator() { return ilist_iterator<NodeTy>(*this); }
>>>>> ilist_iterator<const NodeTy> getIterator() const {
>>>>> - // FIXME: Stop downcasting to create the iterator (potential UB).
>>>>> - return ilist_iterator<const NodeTy>(static_cast<const NodeTy *>(this));
>>>>> + return ilist_iterator<const NodeTy>(*this);
>>>>> }
>>>>> +
>>>>> + using ilist_node_base::isKnownSentinel;
>>>>> +};
>>>>> +
>>>>> +template <typename NodeTy> class ilist_sentinel : public ilist_node<NodeTy> {
>>>>> +public:
>>>>> + ilist_sentinel() {
>>>>> + ilist_node_base::initializeSentinel();
>>>>> + reset();
>>>>> + }
>>>>> +
>>>>> + void reset() {
>>>>> + this->setPrev(this);
>>>>> + this->setNext(this);
>>>>> + }
>>>>> +
>>>>> + bool empty() const { return this == this->getPrev(); }
>>>>> };
>>>>>
>>>>> /// An ilist node that can access its parent list.
>>>>>
>>>>> Modified: llvm/trunk/unittests/ADT/ilistTest.cpp
>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/ilistTest.cpp?rev=278974&r1=278973&r2=278974&view=diff
>>>>> ==============================================================================
>>>>> --- llvm/trunk/unittests/ADT/ilistTest.cpp (original)
>>>>> +++ llvm/trunk/unittests/ADT/ilistTest.cpp Wed Aug 17 15:44:33 2016
>>>>> @@ -128,4 +128,66 @@ TEST(ilistTest, UnsafeClear) {
>>>>> EXPECT_EQ(6, List.back().Value);
>>>>> }
>>>>>
>>>>> +struct NodeWithCallback : ilist_node<NodeWithCallback> {
>>>>> + int Value = 0;
>>>>> + bool IsInList = false;
>>>>> +
>>>>> + NodeWithCallback() = default;
>>>>> + NodeWithCallback(int Value) : Value(Value) {}
>>>>> + NodeWithCallback(const NodeWithCallback &) = delete;
>>>>> +};
>>>>> +
>>>>> +} // end namespace
>>>>> +
>>>>> +namespace llvm {
>>>>> +template <>
>>>>> +struct ilist_traits<NodeWithCallback>
>>>>> + : public ilist_node_traits<NodeWithCallback> {
>>>>> + void addNodeToList(NodeWithCallback *N) { N->IsInList = true; }
>>>>> + void removeNodeFromList(NodeWithCallback *N) { N->IsInList = false; }
>>>>> +};
>>>>> +} // end namespace llvm
>>>>> +
>>>>> +namespace {
>>>>> +
>>>>> +TEST(ilistTest, addNodeToList) {
>>>>> + ilist<NodeWithCallback> L;
>>>>> + NodeWithCallback N(7);
>>>>> + ASSERT_FALSE(N.IsInList);
>>>>> +
>>>>> + L.insert(L.begin(), &N);
>>>>> + ASSERT_EQ(1u, L.size());
>>>>> + ASSERT_EQ(&N, &*L.begin());
>>>>> + ASSERT_TRUE(N.IsInList);
>>>>> +
>>>>> + L.remove(&N);
>>>>> + ASSERT_EQ(0u, L.size());
>>>>> + ASSERT_FALSE(N.IsInList);
>>>>> }
>>>>> +
>>>>> +struct PrivateNode : private ilist_node<PrivateNode> {
>>>>> + friend struct llvm::ilist_node_access;
>>>>> +
>>>>> + int Value = 0;
>>>>> +
>>>>> + PrivateNode() = default;
>>>>> + PrivateNode(int Value) : Value(Value) {}
>>>>> + PrivateNode(const PrivateNode &) = delete;
>>>>> +};
>>>>> +
>>>>> +TEST(ilistTest, privateNode) {
>>>>> + // Instantiate various APIs to be sure they're callable when ilist_node is
>>>>> + // inherited privately.
>>>>> + ilist<NodeWithCallback> L;
>>>>> + NodeWithCallback N(7);
>>>>> + L.insert(L.begin(), &N);
>>>>> + ++L.begin();
>>>>> + (void)*L.begin();
>>>>> + (void)(L.begin() == L.end());
>>>>> +
>>>>> + ilist<NodeWithCallback> L2;
>>>>> + L2.splice(L2.end(), L);
>>>>> + L2.remove(&N);
>>>>> +}
>>>>> +
>>>>> +} // end namespace
>>>>>
>>>>>
>>>>> _______________________________________________
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