X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FUse.h;h=80804459cc339e017d0073dc47519d5dc941a1fe;hb=1b005075b6f0b698eeca69e108688d112bd44519;hp=b116e8c3b508db07d53a1409a0389e7eebb27d1f;hpb=6c2c95d0acd867add034d93d4b909ddd75d61b14;p=oota-llvm.git

diff --git a/include/llvm/Use.h b/include/llvm/Use.h
index b116e8c3b50..80804459cc3 100644
--- a/include/llvm/Use.h
+++ b/include/llvm/Use.h
@@ -11,117 +11,90 @@
 // 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 "llvm/Support/Compiler.h"
+#include <cstddef>
+#include <iterator>
 
 namespace llvm {
 
 class Value;
 class User;
+class Use;
+template<typename>
+struct simplify_type;
 
-
-//===----------------------------------------------------------------------===//
-//                          Generic Tagging Functions
-//===----------------------------------------------------------------------===//
-
-/// Tag - generic tag type for (at least 32 bit) pointers
-enum Tag { noTag, tagOne, tagTwo, tagThree };
-
-/// addTag - insert tag bits into an (untagged) pointer
-template <typename T, typename TAG>
-inline T *addTag(const T *P, TAG Tag) {
-    return reinterpret_cast<T*>(ptrdiff_t(P) | Tag);
-}
-
-/// stripTag - remove tag bits from a pointer,
-/// making it dereferencable
-template <ptrdiff_t MASK, typename T>
-inline T *stripTag(const T *P) {
-  return reinterpret_cast<T*>(ptrdiff_t(P) & ~MASK);
-}
-
-/// extractTag - extract tag bits from a pointer
-template <typename TAG, TAG MASK, typename T>
-inline TAG extractTag(const T *P) {
-  return TAG(ptrdiff_t(P) & MASK);
-}
-
-/// transferTag - transfer tag bits from a pointer,
-/// to an untagged pointer
-template <ptrdiff_t MASK, typename T>
-inline T *transferTag(const T *From, const T *To) {
-  return reinterpret_cast<T*>((ptrdiff_t(From) & MASK) | ptrdiff_t(To));
-}
-
+// 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
 //===----------------------------------------------------------------------===//
 
-// Use is here to make keeping the "use" list of a Value up-to-date really easy.
-//
+/// Use is here to make keeping the "use" list of a Value up-to-date really
+/// easy.
 class Use {
-  class UseWaymark;
-  friend class UseWaymark;
-  Value *getValue() const;
-  /// nilUse - returns a 'token' that marks the end of the def/use chain
-  static Use *nilUse(const Value *V) {
-    return addTag((Use*)V, fullStopTagN);
-  }
-  static bool isNil(Use *U) { return extractTag<NextPtrTag, tagMaskN>(U) == fullStopTagN; }
-  void showWaymarks() const;
-  static bool isStop(Use *U) {
-    return isStopTag(extractTag<NextPtrTag, tagMaskN>(U));
-  }
 public:
-  /// init - specify Value and User
-  /// @deprecated in 2.4, will be removed soon
-  inline void init(Value *V, User *U);
   /// swap - provide a fast substitute to std::swap<Use>
   /// that also works with less standard-compliant compilers
   void swap(Use &RHS);
 
+  // A type for the word following an array of hung-off Uses in memory, which is
+  // a pointer back to their User with the bottom bit set.
+  typedef PointerIntPair<User*, 1, unsigned> UserRef;
+
 private:
   /// Copy ctor - do not implement
-  Use(const Use &U);
+  Use(const Use &U) LLVM_DELETED_FUNCTION;
 
   /// Destructor - Only for zap()
-  inline ~Use() {
-    if (Val1) removeFromList();
+  ~Use() {
+    if (Val) removeFromList();
   }
 
-  /// Default ctor - This leaves the Use completely uninitialized.  The only thing
-  /// that is valid to do with this use is to call the "init" method.
-
-  inline Use() {}
-  enum PrevPtrTag { zeroDigitTag = noTag
-                  , oneDigitTag = tagOne
-                  , stopTag = tagTwo
-                  , fullStopTag = tagThree
-                  , tagMask = tagThree };
-
-  enum NextPtrTag { zeroDigitTagN = tagTwo
-                  , oneDigitTagN = tagOne
-                  , stopTagN = noTag
-                  , fullStopTagN = tagThree
-                  , tagMaskN = tagThree };
-
-  static bool isStopTag(NextPtrTag T) {
-    bool P[] = { true, false, false, true };
-    return P[T];
+  enum PrevPtrTag { zeroDigitTag
+                  , oneDigitTag
+                  , stopTag
+                  , fullStopTag };
+
+  /// Constructor
+  Use(PrevPtrTag tag) : Val(0) {
+    Prev.setInt(tag);
   }
+
 public:
-  operator Value*() const { return get(); }
-  inline Value *get() const;
+  /// Normally Use will just implicitly convert to a Value* that it holds.
+  operator Value*() const { return Val; }
+  
+  /// If implicit conversion to Value* doesn't work, the get() method returns
+  /// the Value*.
+  Value *get() const { return Val; }
+  
+  /// getUser - This returns the User that contains this Use.  For an
+  /// instruction operand, for example, this will return the instruction.
   User *getUser() const;
-  const Use* getImpliedUser() const;
-  static Use *initTags(Use *Start, Use *Stop, ptrdiff_t Done = 0);
-  static void zap(Use *Start, const Use *Stop, bool del = false);
 
   inline void set(Value *Val);
 
@@ -130,38 +103,44 @@ public:
     return RHS;
   }
   const Use &operator=(const Use &RHS) {
-    set(RHS.Val1);
+    set(RHS.Val);
     return *this;
   }
 
-        Value *operator->()       { return get(); }
-  const Value *operator->() const { return get(); }
+        Value *operator->()       { return Val; }
+  const Value *operator->() const { return Val; }
+
+  Use *getNext() const { return Next; }
+
+  
+  /// initTags - initialize the waymarking tags on an array of Uses, so that
+  /// getUser() can find the User from any of those Uses.
+  static Use *initTags(Use *Start, Use *Stop);
+
+  /// zap - This is used to destroy Use operands when the number of operands of
+  /// a User changes.
+  static void zap(Use *Start, const Use *Stop, bool del = false);
 
-  Use *getNext() const { return extractTag<NextPtrTag, tagMaskN>(Next) == fullStopTagN
-			   ? 0
-			   : stripTag<tagMaskN>(Next); }
 private:
-  Value *Val1;
-  Use *Next, **Prev;
+  const Use* getImpliedUser() const;
+  
+  Value *Val;
+  Use *Next;
+  PointerIntPair<Use**, 2, PrevPtrTag> Prev;
 
   void setPrev(Use **NewPrev) {
-    Prev = transferTag<tagMask>(Prev, NewPrev);
+    Prev.setPointer(NewPrev);
   }
   void addToList(Use **List) {
     Next = *List;
-    Use *StrippedNext(getNext());
-    if (StrippedNext) StrippedNext->setPrev(&Next);
+    if (Next) Next->setPrev(&Next);
     setPrev(List);
     *List = this;
   }
   void removeFromList() {
-    // __builtin_prefetch(Next);
-    Use **StrippedPrev = stripTag<tagMask>(Prev);
-    Use *StrippedNext(getNext());
-    if (isStop(Next))
-      assert((isStop(*StrippedPrev) || (StrippedNext ? isStop(StrippedNext->Next) : true)) && "joining digits?");
+    Use **StrippedPrev = Prev.getPointer();
     *StrippedPrev = Next;
-    if (StrippedNext) StrippedNext->setPrev(StrippedPrev);
+    if (Next) Next->setPrev(StrippedPrev);
   }
 
   friend class Value;
@@ -185,15 +164,13 @@ 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;
-  explicit value_use_iterator(Use *u) : U(extractTag<Use::NextPtrTag, Use::tagMaskN>(u)
-					  == Use::fullStopTagN
-					  ? 0
-					  : stripTag<Use::tagMaskN>(u)) {}
+  explicit value_use_iterator(Use *u) : U(u) {}
   friend class Value;
 public:
   typedef typename super::reference reference;
@@ -210,11 +187,11 @@ public:
   }
 
   /// atEnd - return true if this iterator is equal to use_end() on the value.
-  bool atEnd() const { return !U; }
+  bool atEnd() const { return U == 0; }
 
   // Iterator traversal: forward iteration only
   _Self &operator++() {          // Preincrement
-    assert(!atEnd() && "Cannot increment end iterator!");
+    assert(U && "Cannot increment end iterator!");
     U = U->getNext();
     return *this;
   }
@@ -222,9 +199,9 @@ public:
     _Self tmp = *this; ++*this; return tmp;
   }
 
-  // Retrieve a reference to the current User
+  // Retrieve a pointer to the current User.
   UserTy *operator*() const {
-    assert(!atEnd() && "Cannot dereference end iterator!");
+    assert(U && "Cannot dereference end iterator!");
     return U->getUser();
   }
 
@@ -238,35 +215,6 @@ public:
   unsigned getOperandNo() const;
 };
 
-Value *Use::get() const {
-  return fullStopTagN == extractTag<NextPtrTag, tagMaskN>(Next)
-    ? reinterpret_cast<Value*>(stripTag<tagMaskN>(Next))
-    : (Val1 == getValue() ? Val1 : 0); // should crash if not equal!
-}
-
-template<> struct simplify_type<value_use_iterator<User> > {
-  typedef User* SimpleType;
-  
-  static SimpleType getSimplifiedValue(const value_use_iterator<User> &Val) {
-    return *Val;
-  }
-};
-
-template<> struct simplify_type<const value_use_iterator<User> >
- : public simplify_type<value_use_iterator<User> > {};
-
-template<> struct simplify_type<value_use_iterator<const User> > {
-  typedef const User* SimpleType;
-  
-  static SimpleType getSimplifiedValue(const 
-                                       value_use_iterator<const User> &Val) {
-    return *Val;
-  }
-};
-
-template<> struct simplify_type<const value_use_iterator<const User> >
-  : public simplify_type<value_use_iterator<const User> > {};
-
 } // End llvm namespace
 
 #endif