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      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
    206