1 files changed, 74 insertions, 124 deletions

diff --git a/include/llvm/IR/Use.h b/include/llvm/IR/Use.h
index 12cd150af4c8..033cd3e2f5da 100644
--- a/include/llvm/IR/Use.h
+++ b/include/llvm/IR/Use.h
@@ -6,29 +6,29 @@
 // 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
-//
+/// \file
+///
+/// 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_IR_USE_H
 #define LLVM_IR_USE_H
 
+#include "llvm-c/Core.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/Support/CBindingWrapping.h"
 #include "llvm/Support/Compiler.h"
-#include "llvm-c/Core.h"
 #include <cstddef>
 #include <iterator>
 
@@ -37,64 +37,67 @@ namespace llvm {
 class Value;
 class User;
 class Use;
-template<typename>
-struct simplify_type;
+template <typename> struct simplify_type;
 
 // Use** is only 4-byte aligned.
-template<>
-class PointerLikeTypeTraits<Use**> {
+template <> class PointerLikeTypeTraits<Use **> {
 public:
-  static inline void *getAsVoidPointer(Use** P) { return P; }
+  static inline void *getAsVoidPointer(Use **P) { return P; }
   static inline Use **getFromVoidPointer(void *P) {
-    return static_cast<Use**>(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.
+/// \brief A Use represents the edge between a Value definition and its users.
+///
+/// This is notionally a two-dimensional linked list. It supports traversing
+/// all of the uses for a particular value definition. It also supports jumping
+/// directly to the used value when we arrive from the User's operands, and
+/// jumping directly to the User when we arrive from the Value's uses.
+///
+/// The pointer to the used Value is explicit, and the pointer to the User is
+/// implicit. The implicit pointer is found via a waymarking algorithm
+/// described in the programmer's manual:
+///
+///   http://www.llvm.org/docs/ProgrammersManual.html#the-waymarking-algorithm
+///
+/// This is essentially the single most memory intensive object in LLVM because
+/// of the number of uses in the system. At the same time, the constant time
+/// operations it allows are essential to many optimizations having reasonable
+/// time complexity.
 class Use {
 public:
-  /// swap - provide a fast substitute to std::swap<Use>
+  /// \brief 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;
+  typedef PointerIntPair<User *, 1, unsigned> UserRef;
 
 private:
   Use(const Use &U) LLVM_DELETED_FUNCTION;
 
   /// Destructor - Only for zap()
   ~Use() {
-    if (Val) removeFromList();
+    if (Val)
+      removeFromList();
   }
 
-  enum PrevPtrTag { zeroDigitTag
-                  , oneDigitTag
-                  , stopTag
-                  , fullStopTag };
+  enum PrevPtrTag { zeroDigitTag, oneDigitTag, stopTag, fullStopTag };
 
   /// Constructor
-  Use(PrevPtrTag tag) : Val(0) {
-    Prev.setInt(tag);
-  }
+  Use(PrevPtrTag tag) : Val(nullptr) { 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*.
+  operator Value *() const { return Val; }
   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.
+
+  /// \brief 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);
@@ -108,116 +111,63 @@ public:
     return *this;
   }
 
-        Value *operator->()       { return Val; }
+  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.
+  /// \brief Return the operand # of this use in its User.
+  unsigned getOperandNo() const;
+
+  /// \brief Initializes the waymarking tags on an array of Uses.
+  ///
+  /// This sets up the array of Uses such 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
+  /// \brief Destroys 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;
-  
+  const Use *getImpliedUser() const;
+
   Value *Val;
   Use *Next;
-  PointerIntPair<Use**, 2, PrevPtrTag> Prev;
+  PointerIntPair<Use **, 2, PrevPtrTag> Prev;
 
-  void setPrev(Use **NewPrev) {
-    Prev.setPointer(NewPrev);
-  }
+  void setPrev(Use **NewPrev) { Prev.setPointer(NewPrev); }
   void addToList(Use **List) {
     Next = *List;
-    if (Next) Next->setPrev(&Next);
+    if (Next)
+      Next->setPrev(&Next);
     setPrev(List);
     *List = this;
   }
   void removeFromList() {
     Use **StrippedPrev = Prev.getPointer();
     *StrippedPrev = Next;
-    if (Next) Next->setPrev(StrippedPrev);
+    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(Use &Val) {
-    return Val.get();
-  }
+/// \brief Allow clients to treat uses just like values when using
+/// casting operators.
+template <> struct simplify_type<Use> {
+  typedef Value *SimpleType;
+  static SimpleType getSimplifiedValue(Use &Val) { return Val.get(); }
 };
-template<> struct simplify_type<const Use> {
-  typedef /*const*/ Value* SimpleType;
-  static SimpleType getSimplifiedValue(const Use &Val) {
-    return Val.get();
-  }
-};
-
-
-
-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;
-
-  Use *U;
-  explicit value_use_iterator(Use *u) : U(u) {}
-  friend class Value;
-public:
-  typedef typename super::reference reference;
-  typedef typename super::pointer pointer;
-
-  value_use_iterator() {}
-
-  bool operator==(const _Self &x) const {
-    return U == x.U;
-  }
-  bool operator!=(const _Self &x) const {
-    return !operator==(x);
-  }
-
-  /// atEnd - return true if this iterator is equal to use_end() on the value.
-  bool atEnd() const { return U == 0; }
-
-  // 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;
-  }
-
-  // Retrieve a pointer to the current User.
-  UserTy *operator*() const {
-    assert(U && "Cannot dereference end iterator!");
-    return U->getUser();
-  }
-
-  UserTy *operator->() const { return operator*(); }
-
-  Use &getUse() const { return *U; }
-  
-  /// getOperandNo - Return the operand # of this use in its User.  Defined in
-  /// User.h
-  ///
-  unsigned getOperandNo() const;
+template <> struct simplify_type<const Use> {
+  typedef /*const*/ Value *SimpleType;
+  static SimpleType getSimplifiedValue(const Use &Val) { return Val.get(); }
 };
 
 // Create wrappers for C Binding types (see CBindingWrapping.h).
 DEFINE_SIMPLE_CONVERSION_FUNCTIONS(Use, LLVMUseRef)
 
-} // End llvm namespace
+}
 
 #endif