lib/IR/User.cpp

   1 //===-- User.cpp - Implement the User 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 #include "llvm/IR/User.h"
  11 #include "llvm/IR/Constant.h"
  12 #include "llvm/IR/GlobalValue.h"
  13 #include "llvm/IR/Operator.h"
  14
  15 namespace llvm {
  16 class BasicBlock;
  17
  18 //===----------------------------------------------------------------------===//
  19 //                                 User Class
  20 //===----------------------------------------------------------------------===//
  21
  22 void User::anchor() {}
  23
  24 void User::replaceUsesOfWith(Value *From, Value *To) {
  25   if (From == To) return;   // Duh what?
  26
  27   assert((!isa<Constant>(this) || isa<GlobalValue>(this)) &&
  28          "Cannot call User::replaceUsesOfWith on a constant!");
  29
  30   for (unsigned i = 0, E = getNumOperands(); i != E; ++i)
  31     if (getOperand(i) == From) {  // Is This operand is pointing to oldval?
  32       // The side effects of this setOperand call include linking to
  33       // "To", adding "this" to the uses list of To, and
  34       // most importantly, removing "this" from the use list of "From".
  35       setOperand(i, To); // Fix it now...
  36     }
  37 }
  38
  39 //===----------------------------------------------------------------------===//
  40 //                         User allocHungoffUses Implementation
  41 //===----------------------------------------------------------------------===//
  42
  43 void User::allocHungoffUses(unsigned N, bool IsPhi) {
  44   assert(HasHungOffUses && "alloc must have hung off uses");
  45
  46   static_assert(AlignOf<Use>::Alignment >= AlignOf<Use::UserRef>::Alignment,
  47                 "Alignment is insufficient for 'hung-off-uses' pieces");
  48   static_assert(AlignOf<Use::UserRef>::Alignment >=
  49                     AlignOf<BasicBlock *>::Alignment,
  50                 "Alignment is insufficient for 'hung-off-uses' pieces");
  51
  52   // Allocate the array of Uses, followed by a pointer (with bottom bit set) to
  53   // the User.
  54   size_t size = N * sizeof(Use) + sizeof(Use::UserRef);
  55   if (IsPhi)
  56     size += N * sizeof(BasicBlock *);
  57   Use *Begin = static_cast<Use*>(::operator new(size));
  58   Use *End = Begin + N;
  59   (void) new(End) Use::UserRef(const_cast<User*>(this), 1);
  60   setOperandList(Use::initTags(Begin, End));
  61 }
  62
  63 void User::growHungoffUses(unsigned NewNumUses, bool IsPhi) {
  64   assert(HasHungOffUses && "realloc must have hung off uses");
  65
  66   unsigned OldNumUses = getNumOperands();
  67
  68   // We don't support shrinking the number of uses.  We wouldn't have enough
  69   // space to copy the old uses in to the new space.
  70   assert(NewNumUses > OldNumUses && "realloc must grow num uses");
  71
  72   Use *OldOps = getOperandList();
  73   allocHungoffUses(NewNumUses, IsPhi);
  74   Use *NewOps = getOperandList();
  75
  76   // Now copy from the old operands list to the new one.
  77   std::copy(OldOps, OldOps + OldNumUses, NewOps);
  78
  79   // If this is a Phi, then we need to copy the BB pointers too.
  80   if (IsPhi) {
  81     auto *OldPtr =
  82         reinterpret_cast<char *>(OldOps + OldNumUses) + sizeof(Use::UserRef);
  83     auto *NewPtr =
  84         reinterpret_cast<char *>(NewOps + NewNumUses) + sizeof(Use::UserRef);
  85     std::copy(OldPtr, OldPtr + (OldNumUses * sizeof(BasicBlock *)), NewPtr);
  86   }
  87   Use::zap(OldOps, OldOps + OldNumUses, true);
  88 }
  89
  90
  91 // This is a private struct used by `User` to track the co-allocated descriptor
  92 // section.
  93 struct DescriptorInfo {
  94   intptr_t SizeInBytes;
  95 };
  96
  97 ArrayRef<const uint8_t> User::getDescriptor() const {
  98   auto MutableARef = const_cast<User *>(this)->getDescriptor();
  99   return {MutableARef.begin(), MutableARef.end()};
 100 }
 101
 102 MutableArrayRef<uint8_t> User::getDescriptor() {
 103   assert(HasDescriptor && "Don't call otherwise!");
 104   assert(!HasHungOffUses && "Invariant!");
 105
 106   auto *DI = reinterpret_cast<DescriptorInfo *>(getIntrusiveOperands()) - 1;
 107   assert(DI->SizeInBytes != 0 && "Should not have had a descriptor otherwise!");
 108
 109   return MutableArrayRef<uint8_t>(
 110       reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes, DI->SizeInBytes);
 111 }
 112
 113 //===----------------------------------------------------------------------===//
 114 //                         User operator new Implementations
 115 //===----------------------------------------------------------------------===//
 116
 117 void *User::allocateFixedOperandUser(size_t Size, unsigned Us,
 118                                      unsigned DescBytes) {
 119   assert(Us < (1u << NumUserOperandsBits) && "Too many operands");
 120
 121   static_assert(sizeof(DescriptorInfo) % sizeof(void *) == 0, "Required below");
 122
 123   unsigned DescBytesToAllocate =
 124       DescBytes == 0 ? 0 : (DescBytes + sizeof(DescriptorInfo));
 125   assert(DescBytesToAllocate % sizeof(void *) == 0 &&
 126          "We need this to satisfy alignment constraints for Uses");
 127
 128   uint8_t *Storage = static_cast<uint8_t *>(
 129       ::operator new(Size + sizeof(Use) * Us + DescBytesToAllocate));
 130   Use *Start = reinterpret_cast<Use *>(Storage + DescBytesToAllocate);
 131   Use *End = Start + Us;
 132   User *Obj = reinterpret_cast<User*>(End);
 133   Obj->NumUserOperands = Us;
 134   Obj->HasHungOffUses = false;
 135   Obj->HasDescriptor = DescBytes != 0;
 136   Use::initTags(Start, End);
 137
 138   if (DescBytes != 0) {
 139     auto *DescInfo = reinterpret_cast<DescriptorInfo *>(Storage + DescBytes);
 140     DescInfo->SizeInBytes = DescBytes;
 141   }
 142
 143   return Obj;
 144 }
 145
 146 void *User::operator new(size_t Size, unsigned Us) {
 147   return allocateFixedOperandUser(Size, Us, 0);
 148 }
 149
 150 void *User::operator new(size_t Size, unsigned Us, unsigned DescBytes) {
 151   return allocateFixedOperandUser(Size, Us, DescBytes);
 152 }
 153
 154 void *User::operator new(size_t Size) {
 155   // Allocate space for a single Use*
 156   void *Storage = ::operator new(Size + sizeof(Use *));
 157   Use **HungOffOperandList = static_cast<Use **>(Storage);
 158   User *Obj = reinterpret_cast<User *>(HungOffOperandList + 1);
 159   Obj->NumUserOperands = 0;
 160   Obj->HasHungOffUses = true;
 161   Obj->HasDescriptor = false;
 162   *HungOffOperandList = nullptr;
 163   return Obj;
 164 }
 165
 166 //===----------------------------------------------------------------------===//
 167 //                         User operator delete Implementation
 168 //===----------------------------------------------------------------------===//
 169
 170 void User::operator delete(void *Usr) {
 171   // Hung off uses use a single Use* before the User, while other subclasses
 172   // use a Use[] allocated prior to the user.
 173   User *Obj = static_cast<User *>(Usr);
 174   if (Obj->HasHungOffUses) {
 175     assert(!Obj->HasDescriptor && "not supported!");
 176
 177     Use **HungOffOperandList = static_cast<Use **>(Usr) - 1;
 178     // drop the hung off uses.
 179     Use::zap(*HungOffOperandList, *HungOffOperandList + Obj->NumUserOperands,
 180              /* Delete */ true);
 181     ::operator delete(HungOffOperandList);
 182   } else if (Obj->HasDescriptor) {
 183     Use *UseBegin = static_cast<Use *>(Usr) - Obj->NumUserOperands;
 184     Use::zap(UseBegin, UseBegin + Obj->NumUserOperands, /* Delete */ false);
 185
 186     auto *DI = reinterpret_cast<DescriptorInfo *>(UseBegin) - 1;
 187     uint8_t *Storage = reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes;
 188     ::operator delete(Storage);
 189   } else {
 190     Use *Storage = static_cast<Use *>(Usr) - Obj->NumUserOperands;
 191     Use::zap(Storage, Storage + Obj->NumUserOperands,
 192              /* Delete */ false);
 193     ::operator delete(Storage);
 194   }
 195 }
 196
 197 //===----------------------------------------------------------------------===//
 198 //                             Operator Class
 199 //===----------------------------------------------------------------------===//
 200
 201 Operator::~Operator() {
 202   llvm_unreachable("should never destroy an Operator");
 203 }
 204
 205 } // End llvm namespace