lib/VMCore/Use.cpp

   1 //===-- Use.cpp - Implement the Use class ---------------------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the algorithm for finding the User of a Use.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/User.h"
  15
  16 namespace llvm {
  17
  18 //===----------------------------------------------------------------------===//
  19 //                         Use swap Implementation
  20 //===----------------------------------------------------------------------===//
  21
  22 void Use::swap(Use &RHS) {
  23   Value *V1(Val);
  24   Value *V2(RHS.Val);
  25   if (V1 != V2) {
  26     if (V1) {
  27       removeFromList();
  28     }
  29
  30     if (V2) {
  31       RHS.removeFromList();
  32       Val = V2;
  33       V2->addUse(*this);
  34     } else {
  35       Val = 0;
  36     }
  37
  38     if (V1) {
  39       RHS.Val = V1;
  40       V1->addUse(RHS);
  41     } else {
  42       RHS.Val = 0;
  43     }
  44   }
  45 }
  46
  47 //===----------------------------------------------------------------------===//
  48 //                         Use getImpliedUser Implementation
  49 //===----------------------------------------------------------------------===//
  50
  51 const Use *Use::getImpliedUser() const {
  52   const Use *Current = this;
  53
  54   while (true) {
  55     unsigned Tag = (Current++)->Prev.getInt();
  56     switch (Tag) {
  57       case zeroDigitTag:
  58       case oneDigitTag:
  59         continue;
  60
  61       case stopTag: {
  62         ++Current;
  63         ptrdiff_t Offset = 1;
  64         while (true) {
  65           unsigned Tag = Current->Prev.getInt();
  66           switch (Tag) {
  67             case zeroDigitTag:
  68             case oneDigitTag:
  69               ++Current;
  70               Offset = (Offset << 1) + Tag;
  71               continue;
  72             default:
  73               return Current + Offset;
  74           }
  75         }
  76       }
  77
  78       case fullStopTag:
  79         return Current;
  80     }
  81   }
  82 }
  83
  84 //===----------------------------------------------------------------------===//
  85 //                         Use initTags Implementation
  86 //===----------------------------------------------------------------------===//
  87
  88 Use *Use::initTags(Use * const Start, Use *Stop, ptrdiff_t Done) {
  89   ptrdiff_t Count = Done;
  90   while (Start != Stop) {
  91     --Stop;
  92     Stop->Val = 0;
  93     if (!Count) {
  94       Stop->Prev.setFromOpaqueValue(reinterpret_cast<Use**>(Done == 0
  95                                                             ? fullStopTag
  96                                                             : stopTag));
  97       ++Done;
  98       Count = Done;
  99     } else {
 100       Stop->Prev.setFromOpaqueValue(reinterpret_cast<Use**>(Count & 1));
 101       Count >>= 1;
 102       ++Done;
 103     }
 104   }
 105
 106   return Start;
 107 }
 108
 109 //===----------------------------------------------------------------------===//
 110 //                         Use zap Implementation
 111 //===----------------------------------------------------------------------===//
 112
 113 void Use::zap(Use *Start, const Use *Stop, bool del) {
 114   if (del) {
 115     while (Start != Stop) {
 116       (--Stop)->~Use();
 117     }
 118     ::operator delete(Start);
 119     return;
 120   }
 121
 122   while (Start != Stop) {
 123     (Start++)->set(0);
 124   }
 125 }
 126
 127 //===----------------------------------------------------------------------===//
 128 //                         AugmentedUse layout struct
 129 //===----------------------------------------------------------------------===//
 130
 131 struct AugmentedUse : Use {
 132   PointerIntPair<User*, 1, Tag> ref;
 133   AugmentedUse(); // not implemented
 134 };
 135
 136
 137 //===----------------------------------------------------------------------===//
 138 //                         Use getUser Implementation
 139 //===----------------------------------------------------------------------===//
 140
 141 User *Use::getUser() const {
 142   const Use *End = getImpliedUser();
 143   const PointerIntPair<User*, 1, Tag>& ref(
 144                                 static_cast<const AugmentedUse*>(End - 1)->ref);
 145   User *She = ref.getPointer();
 146   return ref.getInt()
 147     ? She
 148     : (User*)End;
 149 }
 150
 151 //===----------------------------------------------------------------------===//
 152 //                         User allocHungoffUses Implementation
 153 //===----------------------------------------------------------------------===//
 154
 155 Use *User::allocHungoffUses(unsigned N) const {
 156   Use *Begin = static_cast<Use*>(::operator new(sizeof(Use) * N
 157                                                 + sizeof(AugmentedUse)
 158                                                 - sizeof(Use)));
 159   Use *End = Begin + N;
 160   PointerIntPair<User*, 1, Tag>& ref(static_cast<AugmentedUse&>(End[-1]).ref);
 161   ref.setPointer(const_cast<User*>(this));
 162   ref.setInt(tagOne);
 163   return Use::initTags(Begin, End);
 164 }
 165
 166 //===----------------------------------------------------------------------===//
 167 //                         User operator new Implementations
 168 //===----------------------------------------------------------------------===//
 169
 170 void *User::operator new(size_t s, unsigned Us) {
 171   void *Storage = ::operator new(s + sizeof(Use) * Us);
 172   Use *Start = static_cast<Use*>(Storage);
 173   Use *End = Start + Us;
 174   User *Obj = reinterpret_cast<User*>(End);
 175   Obj->OperandList = Start;
 176   Obj->NumOperands = Us;
 177   Use::initTags(Start, End);
 178   return Obj;
 179 }
 180
 181 /// Prefixed allocation - just before the first Use, allocate a NULL pointer.
 182 /// The destructor can detect its presence and readjust the OperandList
 183 /// for deletition.
 184 ///
 185 void *User::operator new(size_t s, unsigned Us, bool Prefix) {
 186   // currently prefixed allocation only admissible for
 187   // unconditional branch instructions
 188   if (!Prefix)
 189     return operator new(s, Us);
 190
 191   assert(Us == 1 && "Other than one Use allocated?");
 192   typedef PointerIntPair<void*, 2, Use::PrevPtrTag> TaggedPrefix;
 193   void *Raw = ::operator new(s + sizeof(TaggedPrefix) + sizeof(Use) * Us);
 194   TaggedPrefix *Pre = static_cast<TaggedPrefix*>(Raw);
 195   Pre->setFromOpaqueValue(0);
 196   void *Storage = Pre + 1; // skip over prefix
 197   Use *Start = static_cast<Use*>(Storage);
 198   Use *End = Start + Us;
 199   User *Obj = reinterpret_cast<User*>(End);
 200   Obj->OperandList = Start;
 201   Obj->NumOperands = Us;
 202   Use::initTags(Start, End);
 203   return Obj;
 204 }
 205
 206 //===----------------------------------------------------------------------===//
 207 //                         User operator delete Implementation
 208 //===----------------------------------------------------------------------===//
 209
 210 void User::operator delete(void *Usr) {
 211   User *Start = static_cast<User*>(Usr);
 212   Use *Storage = static_cast<Use*>(Usr) - Start->NumOperands;
 213   //
 214   // look for a variadic User
 215   if (Storage == Start->OperandList) {
 216     ::operator delete(Storage);
 217     return;
 218   }
 219   //
 220   // check for the flag whether the destructor has detected a prefixed
 221   // allocation, in which case we remove the flag and delete starting
 222   // at OperandList
 223   if (reinterpret_cast<intptr_t>(Start->OperandList) & 1) {
 224     ::operator delete(reinterpret_cast<char*>(Start->OperandList) - 1);
 225     return;
 226   }
 227   //
 228   // in all other cases just delete the nullary User (covers hung-off
 229   // uses also
 230   ::operator delete(Usr);
 231 }
 232
 233 } // End llvm namespace