- /// \brief Return a node that marks the end of a list.
- ///
- /// The sentinel is relative to this instance, so we use a non-static
- /// method.
- Instruction *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<Instruction*>(&Sentinel);
- }
- static void destroySentinel(Instruction*) {}
+ BasicBlock *createSentinel() const;
+ static void destroySentinel(BasicBlock*) {}
+
+ BasicBlock *provideInitialHead() const { return createSentinel(); }
+ BasicBlock *ensureHead(BasicBlock*) const { return createSentinel(); }
+ static void noteHead(BasicBlock*, BasicBlock*) {}