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
  14 namespace llvm {
  15 class BasicBlock;
  16
  17 //===----------------------------------------------------------------------===//
  18 //                                 User Class
  19 //===----------------------------------------------------------------------===//
  20
  21 void User::replaceUsesOfWith(Value *From, Value *To) {
  22   if (From == To) return;   // Duh what?
  23
  24   assert((!isa<Constant>(this) || isa<GlobalValue>(this)) &&
  25          "Cannot call User::replaceUsesOfWith on a constant!");
  26
  27   for (unsigned i = 0, E = getNumOperands(); i != E; ++i)
  28     if (getOperand(i) == From) {  // Is This operand is pointing to oldval?
  29       // The side effects of this setOperand call include linking to
  30       // "To", adding "this" to the uses list of To, and
  31       // most importantly, removing "this" from the use list of "From".
  32       setOperand(i, To); // Fix it now...
  33     }
  34 }
  35
  36 //===----------------------------------------------------------------------===//
  37 //                         User allocHungoffUses Implementation
  38 //===----------------------------------------------------------------------===//
  39
  40 void User::allocHungoffUses(unsigned N, bool IsPhi) {
  41   assert(HasHungOffUses && "alloc must have hung off uses");
  42
  43   static_assert(alignof(Use) >= alignof(Use::UserRef),
  44                 "Alignment is insufficient for 'hung-off-uses' pieces");
  45   static_assert(alignof(Use::UserRef) >= alignof(BasicBlock *),
  46                 "Alignment is insufficient for 'hung-off-uses' pieces");
  47
  48   // Allocate the array of Uses, followed by a pointer (with bottom bit set) to
  49   // the User.
  50   size_t size = N * sizeof(Use) + sizeof(Use::UserRef);
  51   if (IsPhi)
  52     size += N * sizeof(BasicBlock *);
  53   Use *Begin = static_cast<Use*>(::operator new(size));
  54   Use *End = Begin + N;
  55   (void) new(End) Use::UserRef(const_cast<User*>(this), 1);
  56   setOperandList(Use::initTags(Begin, End));
  57 }
  58
  59 void User::growHungoffUses(unsigned NewNumUses, bool IsPhi) {
  60   assert(HasHungOffUses && "realloc must have hung off uses");
  61
  62   unsigned OldNumUses = getNumOperands();
  63
  64   // We don't support shrinking the number of uses.  We wouldn't have enough
  65   // space to copy the old uses in to the new space.
  66   assert(NewNumUses > OldNumUses && "realloc must grow num uses");
  67
  68   Use *OldOps = getOperandList();
  69   allocHungoffUses(NewNumUses, IsPhi);
  70   Use *NewOps = getOperandList();
  71
  72   // Now copy from the old operands list to the new one.
  73   std::copy(OldOps, OldOps + OldNumUses, NewOps);
  74
  75   // If this is a Phi, then we need to copy the BB pointers too.
  76   if (IsPhi) {
  77     auto *OldPtr =
  78         reinterpret_cast<char *>(OldOps + OldNumUses) + sizeof(Use::UserRef);
  79     auto *NewPtr =
  80         reinterpret_cast<char *>(NewOps + NewNumUses) + sizeof(Use::UserRef);
  81     std::copy(OldPtr, OldPtr + (OldNumUses * sizeof(BasicBlock *)), NewPtr);
  82   }
  83   Use::zap(OldOps, OldOps + OldNumUses, true);
  84 }
  85
  86
  87 // This is a private struct used by `User` to track the co-allocated descriptor
  88 // section.
  89 struct DescriptorInfo {
  90   intptr_t SizeInBytes;
  91 };
  92
  93 ArrayRef<const uint8_t> User::getDescriptor() const {
  94   auto MutableARef = const_cast<User *>(this)->getDescriptor();
  95   return {MutableARef.begin(), MutableARef.end()};
  96 }
  97
  98 MutableArrayRef<uint8_t> User::getDescriptor() {
  99   assert(HasDescriptor && "Don't call otherwise!");
 100   assert(!HasHungOffUses && "Invariant!");
 101
 102   auto *DI = reinterpret_cast<DescriptorInfo *>(getIntrusiveOperands()) - 1;
 103   assert(DI->SizeInBytes != 0 && "Should not have had a descriptor otherwise!");
 104
 105   return MutableArrayRef<uint8_t>(
 106       reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes, DI->SizeInBytes);
 107 }
 108
 109 //===----------------------------------------------------------------------===//
 110 //                         User operator new Implementations
 111 //===----------------------------------------------------------------------===//
 112
 113 void *User::allocateFixedOperandUser(size_t Size, unsigned Us,
 114                                      unsigned DescBytes) {
 115   assert(Us < (1u << NumUserOperandsBits) && "Too many operands");
 116
 117   static_assert(sizeof(DescriptorInfo) % sizeof(void *) == 0, "Required below");
 118
 119   unsigned DescBytesToAllocate =
 120       DescBytes == 0 ? 0 : (DescBytes + sizeof(DescriptorInfo));
 121   assert(DescBytesToAllocate % sizeof(void *) == 0 &&
 122          "We need this to satisfy alignment constraints for Uses");
 123
 124   uint8_t *Storage = static_cast<uint8_t *>(
 125       ::operator new(Size + sizeof(Use) * Us + DescBytesToAllocate));
 126   Use *Start = reinterpret_cast<Use *>(Storage + DescBytesToAllocate);
 127   Use *End = Start + Us;
 128   User *Obj = reinterpret_cast<User*>(End);
 129   Obj->NumUserOperands = Us;
 130   Obj->HasHungOffUses = false;
 131   Obj->HasDescriptor = DescBytes != 0;
 132   Use::initTags(Start, End);
 133
 134   if (DescBytes != 0) {
 135     auto *DescInfo = reinterpret_cast<DescriptorInfo *>(Storage + DescBytes);
 136     DescInfo->SizeInBytes = DescBytes;
 137   }
 138
 139   return Obj;
 140 }
 141
 142 void *User::operator new(size_t Size, unsigned Us) {
 143   return allocateFixedOperandUser(Size, Us, 0);
 144 }
 145
 146 void *User::operator new(size_t Size, unsigned Us, unsigned DescBytes) {
 147   return allocateFixedOperandUser(Size, Us, DescBytes);
 148 }
 149
 150 void *User::operator new(size_t Size) {
 151   // Allocate space for a single Use*
 152   void *Storage = ::operator new(Size + sizeof(Use *));
 153   Use **HungOffOperandList = static_cast<Use **>(Storage);
 154   User *Obj = reinterpret_cast<User *>(HungOffOperandList + 1);
 155   Obj->NumUserOperands = 0;
 156   Obj->HasHungOffUses = true;
 157   Obj->HasDescriptor = false;
 158   *HungOffOperandList = nullptr;
 159   return Obj;
 160 }
 161
 162 //===----------------------------------------------------------------------===//
 163 //                         User operator delete Implementation
 164 //===----------------------------------------------------------------------===//
 165
 166 void User::operator delete(void *Usr) {
 167   // Hung off uses use a single Use* before the User, while other subclasses
 168   // use a Use[] allocated prior to the user.
 169   User *Obj = static_cast<User *>(Usr);
 170   if (Obj->HasHungOffUses) {
 171     assert(!Obj->HasDescriptor && "not supported!");
 172
 173     Use **HungOffOperandList = static_cast<Use **>(Usr) - 1;
 174     // drop the hung off uses.
 175     Use::zap(*HungOffOperandList, *HungOffOperandList + Obj->NumUserOperands,
 176              /* Delete */ true);
 177     ::operator delete(HungOffOperandList);
 178   } else if (Obj->HasDescriptor) {
 179     Use *UseBegin = static_cast<Use *>(Usr) - Obj->NumUserOperands;
 180     Use::zap(UseBegin, UseBegin + Obj->NumUserOperands, /* Delete */ false);
 181
 182     auto *DI = reinterpret_cast<DescriptorInfo *>(UseBegin) - 1;
 183     uint8_t *Storage = reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes;
 184     ::operator delete(Storage);
 185   } else {
 186     Use *Storage = static_cast<Use *>(Usr) - Obj->NumUserOperands;
 187     Use::zap(Storage, Storage + Obj->NumUserOperands,
 188              /* Delete */ false);
 189     ::operator delete(Storage);
 190   }
 191 }
 192
 193 } // End llvm namespace