Subzero: Implement InstList in terms of llvm::ilist<> .

src/IceInst.h

 //===- subzero/src/IceInst.h - High-level instructions ----------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the Inst class and its target-independent
@@ skipping 16 matching lines @@
 // Most of the validity checking will be done in the bitcode reader.
 // We need a list of everything that should be validated, and tests
 // for each.
 
 namespace Ice {
 
 // Base instruction class for ICE.  Inst has two subclasses:
 // InstHighLevel and InstTarget.  High-level ICE instructions inherit
 // from InstHighLevel, and low-level (target-specific) ICE
 // instructions inherit from InstTarget.
-class Inst {
+class Inst : public llvm::ilist_node<Inst> {
   Inst(const Inst &) = delete;
   Inst &operator=(const Inst &) = delete;
 
 public:
   enum InstKind {
     // Arbitrary (alphabetical) order, except put Unreachable first.
     Unreachable,
     Alloca,
     Arithmetic,
     Assign, // not part of LLVM/PNaCl bitcode
@@ skipping 783 matching lines @@
 protected:
   InstTarget(Cfg *Func, InstKind Kind, SizeT MaxSrcs, Variable *Dest)
       : Inst(Func, Kind, MaxSrcs, Dest) {
     assert(Kind >= Target);
   }
   ~InstTarget() override {}
 };
 
 } // end of namespace Ice
 
+// Override the default ilist traits so that Inst's private ctor and
+// deleted dtor aren't invoked.
+template <>
+struct llvm::ilist_traits<Ice::Inst> : public llvm::ilist_default_traits<
+                                           Ice::Inst> {
+  Ice::Inst *createSentinel() const {
+    return static_cast<Ice::Inst *>(&Sentinel);
+  }
+  static void destroySentinel(Ice::Inst *) {}
+  Ice::Inst *provideInitialHead() const { return createSentinel(); }
+  Ice::Inst *ensureHead(Ice::Inst *) const { return createSentinel(); }
+  static void noteHead(Ice::Inst *, Ice::Inst *) {}
+  void deleteNode(Ice::Inst *) {}
+
+private:
+  mutable ilist_half_node<Ice::Inst> Sentinel;
+};
+
 #endif // SUBZERO_SRC_ICEINST_H