Provide malloc-free sentinels for the SparseBitVector internals.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164823 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 0 deletions

diff --git a/include/llvm/ADT/SparseBitVector.h b/include/llvm/ADT/SparseBitVector.h
index 791f1082c2..306e92832f 100644
--- a/include/llvm/ADT/SparseBitVector.h
+++ b/include/llvm/ADT/SparseBitVector.h
@@ -262,6 +262,22 @@ public:
   }
 };
 
+template <unsigned ElementSize>
+struct ilist_traits<SparseBitVectorElement<ElementSize> >
+  : public ilist_default_traits<SparseBitVectorElement<ElementSize> > {
+  typedef SparseBitVectorElement<ElementSize> Element;
+
+  Element *createSentinel() const { return static_cast<Element *>(&Sentinel); }
+  static void destroySentinel(Element *) {}
+
+  Element *provideInitialHead() const { return createSentinel(); }
+  Element *ensureHead(Element *) const { return createSentinel(); }
+  static void noteHead(Element *, Element *) {}
+
+private:
+  mutable ilist_half_node<Element> Sentinel;
+};
+
 template <unsigned ElementSize = 128>
 class SparseBitVector {
   typedef ilist<SparseBitVectorElement<ElementSize> > ElementList;