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/Value.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) {
  89   ptrdiff_t Done = 0;
  90   while (Done < 20) {
  91     if (Start == Stop--)
  92       return Start;
  93     static const PrevPtrTag tags[20] = { fullStopTag, oneDigitTag, stopTag,
  94                                          oneDigitTag, oneDigitTag, stopTag,
  95                                          zeroDigitTag, oneDigitTag, oneDigitTag,
  96                                          stopTag, zeroDigitTag, oneDigitTag,
  97                                          zeroDigitTag, oneDigitTag, stopTag,
  98                                          oneDigitTag, oneDigitTag, oneDigitTag,
  99                                          oneDigitTag, stopTag
 100                                        };
 101     new(Stop) Use(tags[Done++]);
 102   }
 103
 104   ptrdiff_t Count = Done;
 105   while (Start != Stop) {
 106     --Stop;
 107     if (!Count) {
 108       new(Stop) Use(stopTag);
 109       ++Done;
 110       Count = Done;
 111     } else {
 112       new(Stop) Use(PrevPtrTag(Count & 1));
 113       Count >>= 1;
 114       ++Done;
 115     }
 116   }
 117
 118   return Start;
 119 }
 120
 121 //===----------------------------------------------------------------------===//
 122 //                         Use zap Implementation
 123 //===----------------------------------------------------------------------===//
 124
 125 void Use::zap(Use *Start, const Use *Stop, bool del) {
 126   while (Start != Stop)
 127     (--Stop)->~Use();
 128   if (del)
 129     ::operator delete(Start);
 130 }
 131
 132 //===----------------------------------------------------------------------===//
 133 //                         Use getUser Implementation
 134 //===----------------------------------------------------------------------===//
 135
 136 User *Use::getUser() const {
 137   const Use *End = getImpliedUser();
 138   const PointerIntPair<User*, 1, unsigned>&
 139     ref(static_cast<const AugmentedUse*>(End - 1)->ref);
 140   User *She = ref.getPointer();
 141   return ref.getInt()
 142     ? She
 143     : (User*)End;
 144 }
 145
 146 } // End llvm namespace