[llvm] r278974 - ADT: Remove UB in ilist (and use a circular linked list)
Duncan P. N. Exon Smith via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 19 12:50:56 PDT 2016
I doubt that makes a big difference. But if it does, it's easy to revert! These bugs are also fairly easy to fix quickly with detailed backtrace.
I'll recommit when I get a chance (probably in an hour or two).
> On 2016-Aug-19, at 12:39, Diana Picus <diana.picus at linaro.org> wrote:
>
> Hi Duncan,
>
> It passed all the tests + test-suite in a config similar to
> aarch64-full. The caveat is that it's a 48-bit VMA machine, whereas
> the buildbots are 42- and 39-bit VMA. If you think it matters, I can
> do another run on one of our 39-bit VMA machines (since it's done with
> the release testing).
>
> Thanks for your patience,
> Diana
>
> On 19 August 2016 at 16:12, Duncan Exon Smith <dexonsmith at apple.com> wrote:
>> Thanks! (And sorry for the quick ping earlier: it looks like we must be in
>> different time zones.)
>>
>> -- dpnes
>>
>> On Aug 19, 2016, at 04:26, Diana Picus <diana.picus at linaro.org> wrote:
>>
>> Finally got hold of a machine to run this on. It's currently in
>> progress, I'll let you know how it goes.
>>
>> On 19 August 2016 at 13:27, Diana Picus <diana.picus at linaro.org> wrote:
>>
>> 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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>>
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>>
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>>
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>>
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>>
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>>
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>>
>>
>> _______________________________________________
>>
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>>
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>>
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>>
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