X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FUse.h;h=80804459cc339e017d0073dc47519d5dc941a1fe;hb=8b8fa7b2f403ae2f342413239c4151e075022c97;hp=fb5eafb7122c00e5a02d57aba14a78967f1d7540;hpb=8b70b78ba489b090d9866e6a4084ab1e8613b527;p=oota-llvm.git

diff --git a/include/llvm/Use.h b/include/llvm/Use.h
index fb5eafb7122..80804459cc3 100644
--- a/include/llvm/Use.h
+++ b/include/llvm/Use.h
@@ -1,49 +1,100 @@
 //===-- llvm/Use.h - Definition of the Use class ----------------*- C++ -*-===//
-// 
+//
 //                     The LLVM Compiler Infrastructure
 //
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-// 
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
 //===----------------------------------------------------------------------===//
 //
 // This defines the Use class.  The Use class represents the operand of an
 // 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 "Support/ilist"
+#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/Support/Compiler.h"
+#include <cstddef>
+#include <iterator>
 
 namespace llvm {
 
-template<typename NodeTy> struct ilist_traits;
 class Value;
 class User;
+class Use;
+template<typename>
+struct simplify_type;
 
+// 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 {
-  Value *Val;
-  User *U;
-  Use *Prev, *Next;
-  friend class ilist_traits<Use>;
 public:
-  inline Use(Value *v, User *user);
-  inline Use(const Use &u);
-  inline ~Use();
+  /// 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) LLVM_DELETED_FUNCTION;
+
+  /// Destructor - Only for zap()
+  ~Use() {
+    if (Val) removeFromList();
+  }
+
+  enum PrevPtrTag { zeroDigitTag
+                  , oneDigitTag
+                  , stopTag
+                  , fullStopTag };
+
+  /// Constructor
+  Use(PrevPtrTag tag) : Val(0) {
+    Prev.setInt(tag);
+  }
+
+public:
+  /// 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; }
-  User *getUser() const { return U; }
+  
+  /// getUser - This returns the User that contains this Use.  For an
+  /// instruction operand, for example, this will return the instruction.
+  User *getUser() const;
 
   inline void set(Value *Val);
 
@@ -58,28 +109,45 @@ public:
 
         Value *operator->()       { return Val; }
   const Value *operator->() const { return Val; }
-};
 
-template<>
-struct ilist_traits<Use> {
-  static Use *getPrev(Use *N) { return N->Prev; }
-  static Use *getNext(Use *N) { return N->Next; }
-  static const Use *getPrev(const Use *N) { return N->Prev; }
-  static const Use *getNext(const Use *N) { return N->Next; }
-  static void setPrev(Use *N, Use *Prev) { N->Prev = Prev; }
-  static void setNext(Use *N, Use *Next) { N->Next = Next; }
-
-  // createNode - this is used to create the end marker for the use list
-  static Use *createNode() { return new Use(0,0); }
-
-  void addNodeToList(Use *NTy) {}
-  void removeNodeFromList(Use *NTy) {}
-  void transferNodesFromList(iplist<Use, ilist_traits> &L2,
-                             ilist_iterator<Use> first,
-                             ilist_iterator<Use> last) {}
-};
+  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);
+
+private:
+  const Use* getImpliedUser() const;
+  
+  Value *Val;
+  Use *Next;
+  PointerIntPair<Use**, 2, PrevPtrTag> Prev;
 
+  void setPrev(Use **NewPrev) {
+    Prev.setPointer(NewPrev);
+  }
+  void addToList(Use **List) {
+    Next = *List;
+    if (Next) Next->setPrev(&Next);
+    setPrev(List);
+    *List = this;
+  }
+  void removeFromList() {
+    Use **StrippedPrev = Prev.getPointer();
+    *StrippedPrev = Next;
+    if (Next) Next->setPrev(StrippedPrev);
+  }
+
+  friend class Value;
+};
 
+// simplify_type - Allow clients to treat uses just like values when using
+// casting operators.
 template<> struct simplify_type<Use> {
   typedef Value* SimpleType;
   static SimpleType getSimplifiedValue(const Use &Val) {
@@ -93,64 +161,58 @@ template<> struct simplify_type<const Use> {
   }
 };
 
-struct UseListIteratorWrapper : public iplist<Use>::iterator {
-  typedef iplist<Use>::iterator Super;
-  UseListIteratorWrapper() {}
-  UseListIteratorWrapper(const Super &RHS) : Super(RHS) {}
 
-  UseListIteratorWrapper &operator=(const Super &RHS) {
-    Super::operator=(RHS);
-    return *this;
-  }
 
-  inline User *operator*() const;
-  User *operator->() const { return operator*(); }
+template<typename UserTy>  // UserTy == 'User' or 'const User'
+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;
 
-  UseListIteratorWrapper operator--() { return Super::operator--(); }
-  UseListIteratorWrapper operator++() { return Super::operator++(); }
+  Use *U;
+  explicit value_use_iterator(Use *u) : U(u) {}
+  friend class Value;
+public:
+  typedef typename super::reference reference;
+  typedef typename super::pointer pointer;
 
-  UseListIteratorWrapper operator--(int) {    // postdecrement operators...
-    UseListIteratorWrapper tmp = *this;
-    --*this;
-    return tmp;
+  value_use_iterator(const _Self &I) : U(I.U) {}
+  value_use_iterator() {}
+
+  bool operator==(const _Self &x) const {
+    return U == x.U;
   }
-  UseListIteratorWrapper operator++(int) {    // postincrement operators...
-    UseListIteratorWrapper tmp = *this;
-    ++*this;
-    return tmp;
+  bool operator!=(const _Self &x) const {
+    return !operator==(x);
   }
-};
 
-struct UseListConstIteratorWrapper : public iplist<Use>::const_iterator {
-  typedef iplist<Use>::const_iterator Super;
-  UseListConstIteratorWrapper() {}
-  UseListConstIteratorWrapper(const Super &RHS) : Super(RHS) {}
+  /// atEnd - return true if this iterator is equal to use_end() on the value.
+  bool atEnd() const { return U == 0; }
 
-  // Allow conversion from non-const to const iterators
-  UseListConstIteratorWrapper(const UseListIteratorWrapper &RHS) : Super(RHS) {}
-  UseListConstIteratorWrapper(const iplist<Use>::iterator &RHS) : Super(RHS) {}
-
-  UseListConstIteratorWrapper &operator=(const Super &RHS) {
-    Super::operator=(RHS);
+  // Iterator traversal: forward iteration only
+  _Self &operator++() {          // Preincrement
+    assert(U && "Cannot increment end iterator!");
+    U = U->getNext();
     return *this;
   }
+  _Self operator++(int) {        // Postincrement
+    _Self tmp = *this; ++*this; return tmp;
+  }
 
-  inline const User *operator*() const;
-  const User *operator->() const { return operator*(); }
+  // Retrieve a pointer to the current User.
+  UserTy *operator*() const {
+    assert(U && "Cannot dereference end iterator!");
+    return U->getUser();
+  }
 
-  UseListConstIteratorWrapper operator--() { return Super::operator--(); }
-  UseListConstIteratorWrapper operator++() { return Super::operator++(); }
+  UserTy *operator->() const { return operator*(); }
 
-  UseListConstIteratorWrapper operator--(int) {    // postdecrement operators...
-    UseListConstIteratorWrapper tmp = *this;
-    --*this;
-    return tmp;
-  }
-  UseListConstIteratorWrapper operator++(int) {    // postincrement operators...
-    UseListConstIteratorWrapper tmp = *this;
-    ++*this;
-    return tmp;
-  }
+  Use &getUse() const { return *U; }
+  
+  /// getOperandNo - Return the operand # of this use in its User.  Defined in
+  /// User.h
+  ///
+  unsigned getOperandNo() const;
 };
 
 } // End llvm namespace