[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 12:39:57 PDT 2016
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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