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 bool User::replaceUsesOfWith(Value *From, Value *To) {
  22   bool Changed = false;
  23   if (From == To) return Changed;   // Duh what?
  24
  25   assert((!isa<Constant>(this) || isa<GlobalValue>(this)) &&
  26          "Cannot call User::replaceUsesOfWith on a constant!");
  27
  28   for (unsigned i = 0, E = getNumOperands(); i != E; ++i)
  29     if (getOperand(i) == From) {  // Is This operand is pointing to oldval?
  30       // The side effects of this setOperand call include linking to
  31       // "To", adding "this" to the uses list of To, and
  32       // most importantly, removing "this" from the use list of "From".
  33       setOperand(i, To);
  34       Changed = true;
  35     }
  36   if (auto DVI = dyn_cast_or_null<DbgVariableIntrinsic>(this)) {
  37     if (is_contained(DVI->location_ops(), From)) {
  38       DVI->replaceVariableLocationOp(From, To);
  39       Changed = true;
  40     }
  41   }
  42
  43   return Changed;
  44 }
  45
  46 //===----------------------------------------------------------------------===//
  47 //                         User allocHungoffUses Implementation
  48 //===----------------------------------------------------------------------===//
  49
  50 void User::allocHungoffUses(unsigned N, bool IsPhi) {
  51   assert(HasHungOffUses && "alloc must have hung off uses");
  52
  53   static_assert(alignof(Use) >= alignof(BasicBlock *),
  54                 "Alignment is insufficient for 'hung-off-uses' pieces");
  55
  56   // Allocate the array of Uses
  57   size_t size = N * sizeof(Use);
  58   if (IsPhi)
  59     size += N * sizeof(BasicBlock *);
  60   Use *Begin = static_cast<Use*>(::operator new(size));
  61   Use *End = Begin + N;
  62   setOperandList(Begin);
  63   for (; Begin != End; Begin++)
  64     new (Begin) Use(this);
  65 }
  66
  67 void User::growHungoffUses(unsigned NewNumUses, bool IsPhi) {
  68   assert(HasHungOffUses && "realloc must have hung off uses");
  69
  70   unsigned OldNumUses = getNumOperands();
  71
  72   // We don't support shrinking the number of uses.  We wouldn't have enough
  73   // space to copy the old uses in to the new space.
  74   assert(NewNumUses > OldNumUses && "realloc must grow num uses");
  75
  76   Use *OldOps = getOperandList();
  77   allocHungoffUses(NewNumUses, IsPhi);
  78   Use *NewOps = getOperandList();
  79
  80   // Now copy from the old operands list to the new one.
  81   std::copy(OldOps, OldOps + OldNumUses, NewOps);
  82
  83   // If this is a Phi, then we need to copy the BB pointers too.
  84   if (IsPhi) {
  85     auto *OldPtr = reinterpret_cast<char *>(OldOps + OldNumUses);
  86     auto *NewPtr = reinterpret_cast<char *>(NewOps + NewNumUses);
  87     std::copy(OldPtr, OldPtr + (OldNumUses * sizeof(BasicBlock *)), NewPtr);
  88   }
  89   Use::zap(OldOps, OldOps + OldNumUses, true);
  90 }
  91
  92
  93 // This is a private struct used by `User` to track the co-allocated descriptor
  94 // section.
  95 struct DescriptorInfo {
  96   intptr_t SizeInBytes;
  97 };
  98
  99 ArrayRef<const uint8_t> User::getDescriptor() const {
 100   auto MutableARef = const_cast<User *>(this)->getDescriptor();
 101   return {MutableARef.begin(), MutableARef.end()};
 102 }
 103
 104 MutableArrayRef<uint8_t> User::getDescriptor() {
 105   assert(HasDescriptor && "Don't call otherwise!");
 106   assert(!HasHungOffUses && "Invariant!");
 107
 108   auto *DI = reinterpret_cast<DescriptorInfo *>(getIntrusiveOperands()) - 1;
 109   assert(DI->SizeInBytes != 0 && "Should not have had a descriptor otherwise!");
 110
 111   return MutableArrayRef<uint8_t>(
 112       reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes, DI->SizeInBytes);
 113 }
 114
 115 bool User::isDroppable() const {
 116   return isa<AssumeInst>(this) || isa<PseudoProbeInst>(this);
 117 }
 118
 119 //===----------------------------------------------------------------------===//
 120 //                         User operator new Implementations
 121 //===----------------------------------------------------------------------===//
 122
 123 void *User::allocateFixedOperandUser(size_t Size, unsigned Us,
 124                                      unsigned DescBytes) {
 125   assert(Us < (1u << NumUserOperandsBits) && "Too many operands");
 126
 127   static_assert(sizeof(DescriptorInfo) % sizeof(void *) == 0, "Required below");
 128
 129   unsigned DescBytesToAllocate =
 130       DescBytes == 0 ? 0 : (DescBytes + sizeof(DescriptorInfo));
 131   assert(DescBytesToAllocate % sizeof(void *) == 0 &&
 132          "We need this to satisfy alignment constraints for Uses");
 133
 134   uint8_t *Storage = static_cast<uint8_t *>(
 135       ::operator new(Size + sizeof(Use) * Us + DescBytesToAllocate));
 136   Use *Start = reinterpret_cast<Use *>(Storage + DescBytesToAllocate);
 137   Use *End = Start + Us;
 138   User *Obj = reinterpret_cast<User*>(End);
 139   Obj->NumUserOperands = Us;
 140   Obj->HasHungOffUses = false;
 141   Obj->HasDescriptor = DescBytes != 0;
 142   for (; Start != End; Start++)
 143     new (Start) Use(Obj);
 144
 145   if (DescBytes != 0) {
 146     auto *DescInfo = reinterpret_cast<DescriptorInfo *>(Storage + DescBytes);
 147     DescInfo->SizeInBytes = DescBytes;
 148   }
 149
 150   return Obj;
 151 }
 152
 153 void *User::operator new(size_t Size, unsigned Us) {
 154   return allocateFixedOperandUser(Size, Us, 0);
 155 }
 156
 157 void *User::operator new(size_t Size, unsigned Us, unsigned DescBytes) {
 158   return allocateFixedOperandUser(Size, Us, DescBytes);
 159 }
 160
 161 void *User::operator new(size_t Size) {
 162   // Allocate space for a single Use*
 163   void *Storage = ::operator new(Size + sizeof(Use *));
 164   Use **HungOffOperandList = static_cast<Use **>(Storage);
 165   User *Obj = reinterpret_cast<User *>(HungOffOperandList + 1);
 166   Obj->NumUserOperands = 0;
 167   Obj->HasHungOffUses = true;
 168   Obj->HasDescriptor = false;
 169   *HungOffOperandList = nullptr;
 170   return Obj;
 171 }
 172
 173 //===----------------------------------------------------------------------===//
 174 //                         User operator delete Implementation
 175 //===----------------------------------------------------------------------===//
 176
 177 // Repress memory sanitization, due to use-after-destroy by operator
 178 // delete. Bug report 24578 identifies this issue.
 179 LLVM_NO_SANITIZE_MEMORY_ATTRIBUTE void User::operator delete(void *Usr) {
 180   // Hung off uses use a single Use* before the User, while other subclasses
 181   // use a Use[] allocated prior to the user.
 182   User *Obj = static_cast<User *>(Usr);
 183   if (Obj->HasHungOffUses) {
 184     assert(!Obj->HasDescriptor && "not supported!");
 185
 186     Use **HungOffOperandList = static_cast<Use **>(Usr) - 1;
 187     // drop the hung off uses.
 188     Use::zap(*HungOffOperandList, *HungOffOperandList + Obj->NumUserOperands,
 189              /* Delete */ true);
 190     ::operator delete(HungOffOperandList);
 191   } else if (Obj->HasDescriptor) {
 192     Use *UseBegin = static_cast<Use *>(Usr) - Obj->NumUserOperands;
 193     Use::zap(UseBegin, UseBegin + Obj->NumUserOperands, /* Delete */ false);
 194
 195     auto *DI = reinterpret_cast<DescriptorInfo *>(UseBegin) - 1;
 196     uint8_t *Storage = reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes;
 197     ::operator delete(Storage);
 198   } else {
 199     Use *Storage = static_cast<Use *>(Usr) - Obj->NumUserOperands;
 200     Use::zap(Storage, Storage + Obj->NumUserOperands,
 201              /* Delete */ false);
 202     ::operator delete(Storage);
 203   }
 204 }
 205
 206 } // namespace llvm