X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FVMCore%2FValue.cpp;h=207c06d22311fe876c3a3f48ec6a6155145c73d3;hb=2a82d82936729b02fe1bbdcbfe764a61b8999be1;hp=bc5b7a9f81cb5d4b892740f4a85790bbe3b87dab;hpb=6f4266506bca785828bacda55bd5db9172f990c6;p=oota-llvm.git diff --git a/lib/VMCore/Value.cpp b/lib/VMCore/Value.cpp index bc5b7a9f81c..207c06d2231 100644 --- a/lib/VMCore/Value.cpp +++ b/lib/VMCore/Value.cpp @@ -7,19 +7,27 @@ // //===----------------------------------------------------------------------===// // -// This file implements the Value and User classes. +// This file implements the Value, ValueHandle, and User classes. // //===----------------------------------------------------------------------===// +#include "LLVMContextImpl.h" #include "llvm/Constant.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/InstrTypes.h" #include "llvm/Instructions.h" +#include "llvm/Operator.h" #include "llvm/Module.h" #include "llvm/ValueSymbolTable.h" +#include "llvm/ADT/SmallString.h" #include "llvm/Support/Debug.h" +#include "llvm/Support/GetElementPtrTypeIterator.h" +#include "llvm/Support/ErrorHandling.h" #include "llvm/Support/LeakDetector.h" +#include "llvm/Support/ManagedStatic.h" +#include "llvm/Support/ValueHandle.h" +#include "llvm/ADT/DenseMap.h" #include using namespace llvm; @@ -27,25 +35,29 @@ using namespace llvm; // Value Class //===----------------------------------------------------------------------===// -static inline const Type *checkType(const Type *Ty) { +static inline Type *checkType(Type *Ty) { assert(Ty && "Value defined with a null type: Error!"); - return Ty; + return const_cast(Ty); } -Value::Value(const Type *ty, unsigned scid) - : SubclassID(scid), SubclassData(0), VTy(checkType(ty)), +Value::Value(Type *ty, unsigned scid) + : SubclassID(scid), HasValueHandle(0), + SubclassOptionalData(0), SubclassData(0), VTy((Type*)checkType(ty)), UseList(0), Name(0) { + // FIXME: Why isn't this in the subclass gunk?? if (isa(this) || isa(this)) - assert((VTy->isFirstClassType() || VTy == Type::VoidTy || - isa(ty) || VTy->getTypeID() == Type::StructTyID) && - "invalid CallInst type!"); + assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) && + "invalid CallInst type!"); else if (!isa(this) && !isa(this)) - assert((VTy->isFirstClassType() || VTy == Type::VoidTy || - isa(ty)) && + assert((VTy->isFirstClassType() || VTy->isVoidTy()) && "Cannot create non-first-class values except for constants!"); } Value::~Value() { + // Notify all ValueHandles (if present) that this value is going away. + if (HasValueHandle) + ValueHandleBase::ValueIsDeleted(this); + #ifndef NDEBUG // Only in -g mode... // Check to make sure that there are no uses of this value that are still // around when the value is destroyed. If there are, then we have a dangling @@ -54,9 +66,9 @@ Value::~Value() { // a // if (!use_empty()) { - DOUT << "While deleting: " << *VTy << " %" << getNameStr() << "\n"; + dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n"; for (use_iterator I = use_begin(), E = use_end(); I != E; ++I) - DOUT << "Use still stuck around after Def is destroyed:" + dbgs() << "Use still stuck around after Def is destroyed:" << **I << "\n"; } #endif @@ -66,7 +78,7 @@ Value::~Value() { // at this point. if (Name) Name->Destroy(); - + // There should be no uses of this object anymore, remove it. LeakDetector::removeGarbageObject(this); } @@ -74,7 +86,7 @@ Value::~Value() { /// hasNUses - Return true if this Value has exactly N users. /// bool Value::hasNUses(unsigned N) const { - use_const_iterator UI = use_begin(), E = use_end(); + const_use_iterator UI = use_begin(), E = use_end(); for (; N; --N, ++UI) if (UI == E) return false; // Too few. @@ -85,7 +97,7 @@ bool Value::hasNUses(unsigned N) const { /// logically equivalent to getNumUses() >= N. /// bool Value::hasNUsesOrMore(unsigned N) const { - use_const_iterator UI = use_begin(), E = use_end(); + const_use_iterator UI = use_begin(), E = use_end(); for (; N; --N, ++UI) if (UI == E) return false; // Too few. @@ -95,8 +107,21 @@ bool Value::hasNUsesOrMore(unsigned N) const { /// isUsedInBasicBlock - Return true if this value is used in the specified /// basic block. -bool Value::isUsedInBasicBlock(BasicBlock *BB) const { - for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I) { +bool Value::isUsedInBasicBlock(const BasicBlock *BB) const { + // Start by scanning over the instructions looking for a use before we start + // the expensive use iteration. + unsigned MaxBlockSize = 3; + for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) { + if (std::find(I->op_begin(), I->op_end(), this) != I->op_end()) + return true; + if (MaxBlockSize-- == 0) // If the block is larger fall back to use_iterator + break; + } + + if (MaxBlockSize != 0) // We scanned the entire block and found no use. + return false; + + for (const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) { const Instruction *User = dyn_cast(*I); if (User && User->getParent() == BB) return true; @@ -119,115 +144,89 @@ static bool getSymTab(Value *V, ValueSymbolTable *&ST) { if (Function *PP = P->getParent()) ST = &PP->getValueSymbolTable(); } else if (BasicBlock *BB = dyn_cast(V)) { - if (Function *P = BB->getParent()) + if (Function *P = BB->getParent()) ST = &P->getValueSymbolTable(); } else if (GlobalValue *GV = dyn_cast(V)) { - if (Module *P = GV->getParent()) + if (Module *P = GV->getParent()) ST = &P->getValueSymbolTable(); } else if (Argument *A = dyn_cast(V)) { - if (Function *P = A->getParent()) + if (Function *P = A->getParent()) ST = &P->getValueSymbolTable(); - } else { + } else if (isa(V)) + return true; + else { assert(isa(V) && "Unknown value type!"); return true; // no name is setable for this. } return false; } -/// getNameStart - Return a pointer to a null terminated string for this name. -/// Note that names can have null characters within the string as well as at -/// their end. This always returns a non-null pointer. -const char *Value::getNameStart() const { - if (Name == 0) return ""; - return Name->getKeyData(); +StringRef Value::getName() const { + // Make sure the empty string is still a C string. For historical reasons, + // some clients want to call .data() on the result and expect it to be null + // terminated. + if (!Name) return StringRef("", 0); + return Name->getKey(); } -/// getNameLen - Return the length of the string, correctly handling nul -/// characters embedded into them. -unsigned Value::getNameLen() const { - return Name ? Name->getKeyLength() : 0; -} - -/// isName - Return true if this value has the name specified by the provided -/// nul terminated string. -bool Value::isName(const char *N) const { - unsigned InLen = strlen(N); - return InLen == getNameLen() && memcmp(getNameStart(), N, InLen) == 0; -} +void Value::setName(const Twine &NewName) { + // Fast path for common IRBuilder case of setName("") when there is no name. + if (NewName.isTriviallyEmpty() && !hasName()) + return; + SmallString<256> NameData; + StringRef NameRef = NewName.toStringRef(NameData); -std::string Value::getNameStr() const { - if (Name == 0) return ""; - return std::string(Name->getKeyData(), - Name->getKeyData()+Name->getKeyLength()); -} + // Name isn't changing? + if (getName() == NameRef) + return; -void Value::setName(const std::string &name) { - setName(&name[0], name.size()); -} + assert(!getType()->isVoidTy() && "Cannot assign a name to void values!"); -void Value::setName(const char *Name) { - setName(Name, Name ? strlen(Name) : 0); -} - -void Value::setName(const char *NameStr, unsigned NameLen) { - if (NameLen == 0 && !hasName()) return; - assert(getType() != Type::VoidTy && "Cannot assign a name to void values!"); - // Get the symbol table to update for this object. ValueSymbolTable *ST; if (getSymTab(this, ST)) return; // Cannot set a name on this value (e.g. constant). if (!ST) { // No symbol table to update? Just do the change. - if (NameLen == 0) { + if (NameRef.empty()) { // Free the name for this value. Name->Destroy(); Name = 0; return; } - - if (Name) { - // Name isn't changing? - if (NameLen == Name->getKeyLength() && - !memcmp(Name->getKeyData(), NameStr, NameLen)) - return; + + if (Name) Name->Destroy(); - } - + // NOTE: Could optimize for the case the name is shrinking to not deallocate // then reallocated. - + // Create the new name. - Name = ValueName::Create(NameStr, NameStr+NameLen); + Name = ValueName::Create(NameRef.begin(), NameRef.end()); Name->setValue(this); return; } - + // NOTE: Could optimize for the case the name is shrinking to not deallocate // then reallocated. if (hasName()) { - // Name isn't changing? - if (NameLen == Name->getKeyLength() && - !memcmp(Name->getKeyData(), NameStr, NameLen)) - return; - // Remove old name. ST->removeValueName(Name); Name->Destroy(); Name = 0; - if (NameLen == 0) + if (NameRef.empty()) return; } // Name is changing to something new. - Name = ST->createValueName(NameStr, NameLen, this); + Name = ST->createValueName(NameRef, this); } /// takeName - transfer the name from V to this value, setting V's name to -/// empty. It is an error to call V->takeName(V). +/// empty. It is an error to call V->takeName(V). void Value::takeName(Value *V) { ValueSymbolTable *ST = 0; // If this value has a name, drop it. @@ -236,36 +235,36 @@ void Value::takeName(Value *V) { if (getSymTab(this, ST)) { // We can't set a name on this value, but we need to clear V's name if // it has one. - if (V->hasName()) V->setName(0, 0); + if (V->hasName()) V->setName(""); return; // Cannot set a name on this value (e.g. constant). } - + // Remove old name. if (ST) ST->removeValueName(Name); Name->Destroy(); Name = 0; - } - + } + // Now we know that this has no name. - + // If V has no name either, we're done. if (!V->hasName()) return; - + // Get this's symtab if we didn't before. if (!ST) { if (getSymTab(this, ST)) { // Clear V's name. - V->setName(0, 0); + V->setName(""); return; // Cannot set a name on this value (e.g. constant). } } - + // Get V's ST, this should always succed, because V has a name. ValueSymbolTable *VST; bool Failure = getSymTab(V, VST); - assert(!Failure && "V has a name, so it should have a ST!"); Failure=Failure; - + assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure; + // If these values are both in the same symtab, we can do this very fast. // This works even if both values have no symtab yet. if (ST == VST) { @@ -275,28 +274,31 @@ void Value::takeName(Value *V) { Name->setValue(this); return; } - + // Otherwise, things are slightly more complex. Remove V's name from VST and // then reinsert it into ST. - + if (VST) VST->removeValueName(V->Name); Name = V->Name; V->Name = 0; Name->setValue(this); - + if (ST) ST->reinsertValue(this); } -// uncheckedReplaceAllUsesWith - This is exactly the same as replaceAllUsesWith, -// except that it doesn't have all of the asserts. The asserts fail because we -// are half-way done resolving types, which causes some types to exist as two -// different Type*'s at the same time. This is a sledgehammer to work around -// this problem. -// -void Value::uncheckedReplaceAllUsesWith(Value *New) { +void Value::replaceAllUsesWith(Value *New) { + assert(New && "Value::replaceAllUsesWith() is invalid!"); + assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!"); + assert(New->getType() == getType() && + "replaceAllUses of value with new value of different type!"); + + // Notify all ValueHandles (if present) that this value is going away. + if (HasValueHandle) + ValueHandleBase::ValueIsRAUWd(this, New); + while (!use_empty()) { Use &U = *UseList; // Must handle Constants specially, we cannot call replaceUsesOfWith on a @@ -310,78 +312,340 @@ void Value::uncheckedReplaceAllUsesWith(Value *New) { U.set(New); } + + if (BasicBlock *BB = dyn_cast(this)) + BB->replaceSuccessorsPhiUsesWith(cast(New)); } -void Value::replaceAllUsesWith(Value *New) { - assert(New && "Value::replaceAllUsesWith() is invalid!"); - assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!"); - assert(New->getType() == getType() && - "replaceAllUses of value with new value of different type!"); +Value *Value::stripPointerCasts() { + if (!getType()->isPointerTy()) + return this; - uncheckedReplaceAllUsesWith(New); + // Even though we don't look through PHI nodes, we could be called on an + // instruction in an unreachable block, which may be on a cycle. + SmallPtrSet Visited; + + Value *V = this; + Visited.insert(V); + do { + if (GEPOperator *GEP = dyn_cast(V)) { + if (!GEP->hasAllZeroIndices()) + return V; + V = GEP->getPointerOperand(); + } else if (Operator::getOpcode(V) == Instruction::BitCast) { + V = cast(V)->getOperand(0); + } else if (GlobalAlias *GA = dyn_cast(V)) { + if (GA->mayBeOverridden()) + return V; + V = GA->getAliasee(); + } else { + return V; + } + assert(V->getType()->isPointerTy() && "Unexpected operand type!"); + } while (Visited.insert(V)); + + return V; } -Value *Value::stripPointerCasts() { - if (ConstantExpr *CE = dyn_cast(this)) { - if (CE->getOpcode() == Instruction::BitCast) { - if (isa(CE->getOperand(0)->getType())) - return CE->getOperand(0)->stripPointerCasts(); - } else if (CE->getOpcode() == Instruction::GetElementPtr) { - for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) - if (!CE->getOperand(i)->isNullValue()) - return this; - return CE->getOperand(0)->stripPointerCasts(); +/// isDereferenceablePointer - Test if this value is always a pointer to +/// allocated and suitably aligned memory for a simple load or store. +static bool isDereferenceablePointer(const Value *V, + SmallPtrSet &Visited) { + // Note that it is not safe to speculate into a malloc'd region because + // malloc may return null. + // It's also not always safe to follow a bitcast, for example: + // bitcast i8* (alloca i8) to i32* + // would result in a 4-byte load from a 1-byte alloca. Some cases could + // be handled using TargetData to check sizes and alignments though. + + // These are obviously ok. + if (isa(V)) return true; + + // Global variables which can't collapse to null are ok. + if (const GlobalVariable *GV = dyn_cast(V)) + return !GV->hasExternalWeakLinkage(); + + // byval arguments are ok. + if (const Argument *A = dyn_cast(V)) + return A->hasByValAttr(); + + // For GEPs, determine if the indexing lands within the allocated object. + if (const GEPOperator *GEP = dyn_cast(V)) { + // Conservatively require that the base pointer be fully dereferenceable. + if (!Visited.insert(GEP->getOperand(0))) + return false; + if (!isDereferenceablePointer(GEP->getOperand(0), Visited)) + return false; + // Check the indices. + gep_type_iterator GTI = gep_type_begin(GEP); + for (User::const_op_iterator I = GEP->op_begin()+1, + E = GEP->op_end(); I != E; ++I) { + Value *Index = *I; + Type *Ty = *GTI++; + // Struct indices can't be out of bounds. + if (isa(Ty)) + continue; + ConstantInt *CI = dyn_cast(Index); + if (!CI) + return false; + // Zero is always ok. + if (CI->isZero()) + continue; + // Check to see that it's within the bounds of an array. + ArrayType *ATy = dyn_cast(Ty); + if (!ATy) + return false; + if (CI->getValue().getActiveBits() > 64) + return false; + if (CI->getZExtValue() >= ATy->getNumElements()) + return false; } - return this; + // Indices check out; this is dereferenceable. + return true; } - if (BitCastInst *CI = dyn_cast(this)) { - if (isa(CI->getOperand(0)->getType())) - return CI->getOperand(0)->stripPointerCasts(); - } else if (GetElementPtrInst *GEP = dyn_cast(this)) { - if (GEP->hasAllZeroIndices()) - return GEP->getOperand(0)->stripPointerCasts(); - } + // If we don't know, assume the worst. + return false; +} + +/// isDereferenceablePointer - Test if this value is always a pointer to +/// allocated and suitably aligned memory for a simple load or store. +bool Value::isDereferenceablePointer() const { + SmallPtrSet Visited; + return ::isDereferenceablePointer(this, Visited); +} + +/// DoPHITranslation - If this value is a PHI node with CurBB as its parent, +/// return the value in the PHI node corresponding to PredBB. If not, return +/// ourself. This is useful if you want to know the value something has in a +/// predecessor block. +Value *Value::DoPHITranslation(const BasicBlock *CurBB, + const BasicBlock *PredBB) { + PHINode *PN = dyn_cast(this); + if (PN && PN->getParent() == CurBB) + return PN->getIncomingValueForBlock(PredBB); return this; } +LLVMContext &Value::getContext() const { return VTy->getContext(); } + //===----------------------------------------------------------------------===// -// User Class +// ValueHandleBase Class //===----------------------------------------------------------------------===// -// replaceUsesOfWith - Replaces all references to the "From" definition with -// references to the "To" definition. -// -void User::replaceUsesOfWith(Value *From, Value *To) { - if (From == To) return; // Duh what? - - assert((!isa(this) || isa(this)) && - "Cannot call User::replaceUsesofWith on a constant!"); - - for (unsigned i = 0, E = getNumOperands(); i != E; ++i) - if (getOperand(i) == From) { // Is This operand is pointing to oldval? - // The side effects of this setOperand call include linking to - // "To", adding "this" to the uses list of To, and - // most importantly, removing "this" from the use list of "From". - setOperand(i, To); // Fix it now... - } +/// AddToExistingUseList - Add this ValueHandle to the use list for VP, where +/// List is known to point into the existing use list. +void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) { + assert(List && "Handle list is null?"); + + // Splice ourselves into the list. + Next = *List; + *List = this; + setPrevPtr(List); + if (Next) { + Next->setPrevPtr(&Next); + assert(VP == Next->VP && "Added to wrong list?"); + } +} + +void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) { + assert(List && "Must insert after existing node"); + + Next = List->Next; + setPrevPtr(&List->Next); + List->Next = this; + if (Next) + Next->setPrevPtr(&Next); +} + +/// AddToUseList - Add this ValueHandle to the use list for VP. +void ValueHandleBase::AddToUseList() { + assert(VP && "Null pointer doesn't have a use list!"); + + LLVMContextImpl *pImpl = VP->getContext().pImpl; + + if (VP->HasValueHandle) { + // If this value already has a ValueHandle, then it must be in the + // ValueHandles map already. + ValueHandleBase *&Entry = pImpl->ValueHandles[VP]; + assert(Entry != 0 && "Value doesn't have any handles?"); + AddToExistingUseList(&Entry); + return; + } + + // Ok, it doesn't have any handles yet, so we must insert it into the + // DenseMap. However, doing this insertion could cause the DenseMap to + // reallocate itself, which would invalidate all of the PrevP pointers that + // point into the old table. Handle this by checking for reallocation and + // updating the stale pointers only if needed. + DenseMap &Handles = pImpl->ValueHandles; + const void *OldBucketPtr = Handles.getPointerIntoBucketsArray(); + + ValueHandleBase *&Entry = Handles[VP]; + assert(Entry == 0 && "Value really did already have handles?"); + AddToExistingUseList(&Entry); + VP->HasValueHandle = true; + + // If reallocation didn't happen or if this was the first insertion, don't + // walk the table. + if (Handles.isPointerIntoBucketsArray(OldBucketPtr) || + Handles.size() == 1) { + return; + } + + // Okay, reallocation did happen. Fix the Prev Pointers. + for (DenseMap::iterator I = Handles.begin(), + E = Handles.end(); I != E; ++I) { + assert(I->second && I->first == I->second->VP && "List invariant broken!"); + I->second->setPrevPtr(&I->second); + } +} + +/// RemoveFromUseList - Remove this ValueHandle from its current use list. +void ValueHandleBase::RemoveFromUseList() { + assert(VP && VP->HasValueHandle && "Pointer doesn't have a use list!"); + + // Unlink this from its use list. + ValueHandleBase **PrevPtr = getPrevPtr(); + assert(*PrevPtr == this && "List invariant broken"); + + *PrevPtr = Next; + if (Next) { + assert(Next->getPrevPtr() == &Next && "List invariant broken"); + Next->setPrevPtr(PrevPtr); + return; + } + + // If the Next pointer was null, then it is possible that this was the last + // ValueHandle watching VP. If so, delete its entry from the ValueHandles + // map. + LLVMContextImpl *pImpl = VP->getContext().pImpl; + DenseMap &Handles = pImpl->ValueHandles; + if (Handles.isPointerIntoBucketsArray(PrevPtr)) { + Handles.erase(VP); + VP->HasValueHandle = false; + } } -void *User::operator new(size_t s, unsigned Us) { - void *Storage = ::operator new(s + sizeof(Use) * Us); - Use *Start = static_cast(Storage); - Use *End = Start + Us; - User *Obj = reinterpret_cast(End); - Obj->OperandList = Start; - Obj->NumOperands = Us; - Use::initTags(Start, End); - return Obj; + +void ValueHandleBase::ValueIsDeleted(Value *V) { + assert(V->HasValueHandle && "Should only be called if ValueHandles present"); + + // Get the linked list base, which is guaranteed to exist since the + // HasValueHandle flag is set. + LLVMContextImpl *pImpl = V->getContext().pImpl; + ValueHandleBase *Entry = pImpl->ValueHandles[V]; + assert(Entry && "Value bit set but no entries exist"); + + // We use a local ValueHandleBase as an iterator so that ValueHandles can add + // and remove themselves from the list without breaking our iteration. This + // is not really an AssertingVH; we just have to give ValueHandleBase a kind. + // Note that we deliberately do not the support the case when dropping a value + // handle results in a new value handle being permanently added to the list + // (as might occur in theory for CallbackVH's): the new value handle will not + // be processed and the checking code will mete out righteous punishment if + // the handle is still present once we have finished processing all the other + // value handles (it is fine to momentarily add then remove a value handle). + for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) { + Iterator.RemoveFromUseList(); + Iterator.AddToExistingUseListAfter(Entry); + assert(Entry->Next == &Iterator && "Loop invariant broken."); + + switch (Entry->getKind()) { + case Assert: + break; + case Tracking: + // Mark that this value has been deleted by setting it to an invalid Value + // pointer. + Entry->operator=(DenseMapInfo::getTombstoneKey()); + break; + case Weak: + // Weak just goes to null, which will unlink it from the list. + Entry->operator=(0); + break; + case Callback: + // Forward to the subclass's implementation. + static_cast(Entry)->deleted(); + break; + } + } + + // All callbacks, weak references, and assertingVHs should be dropped by now. + if (V->HasValueHandle) { +#ifndef NDEBUG // Only in +Asserts mode... + dbgs() << "While deleting: " << *V->getType() << " %" << V->getName() + << "\n"; + if (pImpl->ValueHandles[V]->getKind() == Assert) + llvm_unreachable("An asserting value handle still pointed to this" + " value!"); + +#endif + llvm_unreachable("All references to V were not removed?"); + } } -void User::operator delete(void *Usr) { - User *Start = static_cast(Usr); - Use *Storage = static_cast(Usr) - Start->NumOperands; - ::operator delete(Storage == Start->OperandList - ? Storage - : Usr); + +void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) { + assert(Old->HasValueHandle &&"Should only be called if ValueHandles present"); + assert(Old != New && "Changing value into itself!"); + + // Get the linked list base, which is guaranteed to exist since the + // HasValueHandle flag is set. + LLVMContextImpl *pImpl = Old->getContext().pImpl; + ValueHandleBase *Entry = pImpl->ValueHandles[Old]; + + assert(Entry && "Value bit set but no entries exist"); + + // We use a local ValueHandleBase as an iterator so that + // ValueHandles can add and remove themselves from the list without + // breaking our iteration. This is not really an AssertingVH; we + // just have to give ValueHandleBase some kind. + for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) { + Iterator.RemoveFromUseList(); + Iterator.AddToExistingUseListAfter(Entry); + assert(Entry->Next == &Iterator && "Loop invariant broken."); + + switch (Entry->getKind()) { + case Assert: + // Asserting handle does not follow RAUW implicitly. + break; + case Tracking: + // Tracking goes to new value like a WeakVH. Note that this may make it + // something incompatible with its templated type. We don't want to have a + // virtual (or inline) interface to handle this though, so instead we make + // the TrackingVH accessors guarantee that a client never sees this value. + + // FALLTHROUGH + case Weak: + // Weak goes to the new value, which will unlink it from Old's list. + Entry->operator=(New); + break; + case Callback: + // Forward to the subclass's implementation. + static_cast(Entry)->allUsesReplacedWith(New); + break; + } + } + +#ifndef NDEBUG + // If any new tracking or weak value handles were added while processing the + // list, then complain about it now. + if (Old->HasValueHandle) + for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next) + switch (Entry->getKind()) { + case Tracking: + case Weak: + dbgs() << "After RAUW from " << *Old->getType() << " %" + << Old->getName() << " to " << *New->getType() << " %" + << New->getName() << "\n"; + llvm_unreachable("A tracking or weak value handle still pointed to the" + " old value!\n"); + default: + break; + } +#endif } + +/// ~CallbackVH. Empty, but defined here to avoid emitting the vtable +/// more than once. +CallbackVH::~CallbackVH() {}