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