llvm/lib/IR/User.cpp

   1 //===-- User.cpp - Implement the User class -------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/IR/User.h"
  10 #include "llvm/IR/Constant.h"
  11 #include "llvm/IR/GlobalValue.h"
  12 #include "llvm/IR/IntrinsicInst.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);
  33     }
  34   if (auto DVI = dyn_cast_or_null<DbgVariableIntrinsic>(this)) {
  35     if (is_contained(DVI->location_ops(), From))
  36       DVI->replaceVariableLocationOp(From, To);
  37   }
  38 }
  39
  40 //===----------------------------------------------------------------------===//
  41 //                         User allocHungoffUses Implementation
  42 //===----------------------------------------------------------------------===//
  43
  44 void User::allocHungoffUses(unsigned N, bool IsPhi) {
  45   assert(HasHungOffUses && "alloc must have hung off uses");
  46
  47   static_assert(alignof(Use) >= alignof(BasicBlock *),
  48                 "Alignment is insufficient for 'hung-off-uses' pieces");
  49
  50   // Allocate the array of Uses
  51   size_t size = N * sizeof(Use);
  52   if (IsPhi)
  53     size += N * sizeof(BasicBlock *);
  54   Use *Begin = static_cast<Use*>(::operator new(size));
  55   Use *End = Begin + N;
  56   setOperandList(Begin);
  57   for (; Begin != End; Begin++)
  58     new (Begin) Use(this);
  59 }
  60
  61 void User::growHungoffUses(unsigned NewNumUses, bool IsPhi) {
  62   assert(HasHungOffUses && "realloc must have hung off uses");
  63
  64   unsigned OldNumUses = getNumOperands();
  65
  66   // We don't support shrinking the number of uses.  We wouldn't have enough
  67   // space to copy the old uses in to the new space.
  68   assert(NewNumUses > OldNumUses && "realloc must grow num uses");
  69
  70   Use *OldOps = getOperandList();
  71   allocHungoffUses(NewNumUses, IsPhi);
  72   Use *NewOps = getOperandList();
  73
  74   // Now copy from the old operands list to the new one.
  75   std::copy(OldOps, OldOps + OldNumUses, NewOps);
  76
  77   // If this is a Phi, then we need to copy the BB pointers too.
  78   if (IsPhi) {
  79     auto *OldPtr = reinterpret_cast<char *>(OldOps + OldNumUses);
  80     auto *NewPtr = reinterpret_cast<char *>(NewOps + NewNumUses);
  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 bool User::isDroppable() const {
 110   return isa<AssumeInst>(this);
 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   for (; Start != End; Start++)
 137     new (Start) Use(Obj);
 138
 139   if (DescBytes != 0) {
 140     auto *DescInfo = reinterpret_cast<DescriptorInfo *>(Storage + DescBytes);
 141     DescInfo->SizeInBytes = DescBytes;
 142   }
 143
 144   return Obj;
 145 }
 146
 147 void *User::operator new(size_t Size, unsigned Us) {
 148   return allocateFixedOperandUser(Size, Us, 0);
 149 }
 150
 151 void *User::operator new(size_t Size, unsigned Us, unsigned DescBytes) {
 152   return allocateFixedOperandUser(Size, Us, DescBytes);
 153 }
 154
 155 void *User::operator new(size_t Size) {
 156   // Allocate space for a single Use*
 157   void *Storage = ::operator new(Size + sizeof(Use *));
 158   Use **HungOffOperandList = static_cast<Use **>(Storage);
 159   User *Obj = reinterpret_cast<User *>(HungOffOperandList + 1);
 160   Obj->NumUserOperands = 0;
 161   Obj->HasHungOffUses = true;
 162   Obj->HasDescriptor = false;
 163   *HungOffOperandList = nullptr;
 164   return Obj;
 165 }
 166
 167 //===----------------------------------------------------------------------===//
 168 //                         User operator delete Implementation
 169 //===----------------------------------------------------------------------===//
 170
 171 // Repress memory sanitization, due to use-after-destroy by operator
 172 // delete. Bug report 24578 identifies this issue.
 173 LLVM_NO_SANITIZE_MEMORY_ATTRIBUTE void User::operator delete(void *Usr) {
 174   // Hung off uses use a single Use* before the User, while other subclasses
 175   // use a Use[] allocated prior to the user.
 176   User *Obj = static_cast<User *>(Usr);
 177   if (Obj->HasHungOffUses) {
 178     assert(!Obj->HasDescriptor && "not supported!");
 179
 180     Use **HungOffOperandList = static_cast<Use **>(Usr) - 1;
 181     // drop the hung off uses.
 182     Use::zap(*HungOffOperandList, *HungOffOperandList + Obj->NumUserOperands,
 183              /* Delete */ true);
 184     ::operator delete(HungOffOperandList);
 185   } else if (Obj->HasDescriptor) {
 186     Use *UseBegin = static_cast<Use *>(Usr) - Obj->NumUserOperands;
 187     Use::zap(UseBegin, UseBegin + Obj->NumUserOperands, /* Delete */ false);
 188
 189     auto *DI = reinterpret_cast<DescriptorInfo *>(UseBegin) - 1;
 190     uint8_t *Storage = reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes;
 191     ::operator delete(Storage);
 192   } else {
 193     Use *Storage = static_cast<Use *>(Usr) - Obj->NumUserOperands;
 194     Use::zap(Storage, Storage + Obj->NumUserOperands,
 195              /* Delete */ false);
 196     ::operator delete(Storage);
 197   }
 198 }
 199
 200 } // namespace llvm