X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FUse.h;h=970f69b9da883553e2fbb8a664839fa8162295b8;hb=9e6d1d1f5034347d237941f1bf08fba5c1583cd3;hp=a2774c802ff743b168e158ea647fb6f07bdd85e3;hpb=84fb959489a07f032208deb8bf32776867aaeab2;p=oota-llvm.git

diff --git a/include/llvm/Use.h b/include/llvm/Use.h
index a2774c802ff..970f69b9da8 100644
--- a/include/llvm/Use.h
+++ b/include/llvm/Use.h
@@ -11,24 +11,43 @@
 // instruction or some other User instance which refers to a Value.  The Use
 // class keeps the "use list" of the referenced value up to date.
 //
+// Pointer tagging is used to efficiently find the User corresponding
+// to a Use without having to store a User pointer in every Use. A
+// User is preceded in memory by all the Uses corresponding to its
+// operands, and the low bits of one of the fields (Prev) of the Use
+// class are used to encode offsets to be able to find that User given
+// a pointer to any Use. For details, see:
+//
+//   http://www.llvm.org/docs/ProgrammersManual.html#UserLayout
+//
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_USE_H
 #define LLVM_USE_H
 
 #include "llvm/Support/Casting.h"
-#include "llvm/ADT/iterator.h"
 #include "llvm/ADT/PointerIntPair.h"
+#include <iterator>
 
 namespace llvm {
 
 class Value;
 class User;
-
+class Use;
 
 /// Tag - generic tag type for (at least 32 bit) pointers
 enum Tag { noTag, tagOne, tagTwo, tagThree };
 
+// Use** is only 4-byte aligned.
+template<>
+class PointerLikeTypeTraits<Use**> {
+public:
+  static inline void *getAsVoidPointer(Use** P) { return P; }
+  static inline Use **getFromVoidPointer(void *P) {
+    return static_cast<Use**>(P);
+  }
+  enum { NumLowBitsAvailable = 2 };
+};
 
 //===----------------------------------------------------------------------===//
 //                                  Use Class
@@ -92,6 +111,8 @@ public:
   /// a User changes.
   static void zap(Use *Start, const Use *Stop, bool del = false);
 
+  /// getPrefix - Return deletable pointer if appropriate
+  Use *getPrefix();
 private:
   const Use* getImpliedUser() const;
   static Use *initTags(Use *Start, Use *Stop, ptrdiff_t Done = 0);
@@ -137,8 +158,9 @@ template<> struct simplify_type<const Use> {
 
 
 template<typename UserTy>  // UserTy == 'User' or 'const User'
-class value_use_iterator : public forward_iterator<UserTy*, ptrdiff_t> {
-  typedef forward_iterator<UserTy*, ptrdiff_t> super;
+class value_use_iterator : public std::iterator<std::forward_iterator_tag,
+                                                UserTy*, ptrdiff_t> {
+  typedef std::iterator<std::forward_iterator_tag, UserTy*, ptrdiff_t> super;
   typedef value_use_iterator<UserTy> _Self;
 
   Use *U;
@@ -210,7 +232,7 @@ template<> struct simplify_type<value_use_iterator<const User> > {
 
 template<> struct simplify_type<const value_use_iterator<const User> >
   : public simplify_type<value_use_iterator<const User> > {};
-
+ 
 } // End llvm namespace
 
 #endif