1 //===-- Value.cpp - Implement the Value class -----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the Value, ValueHandle, and User classes.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/IR/Value.h"
15 #include "LLVMContextImpl.h"
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/IR/Constant.h"
19 #include "llvm/IR/Constants.h"
20 #include "llvm/IR/DerivedTypes.h"
21 #include "llvm/IR/GetElementPtrTypeIterator.h"
22 #include "llvm/IR/InstrTypes.h"
23 #include "llvm/IR/Instructions.h"
24 #include "llvm/IR/LeakDetector.h"
25 #include "llvm/IR/Module.h"
26 #include "llvm/IR/Operator.h"
27 #include "llvm/IR/ValueHandle.h"
28 #include "llvm/IR/ValueSymbolTable.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/ManagedStatic.h"
35 //===----------------------------------------------------------------------===//
37 //===----------------------------------------------------------------------===//
39 static inline Type *checkType(Type *Ty) {
40 assert(Ty && "Value defined with a null type: Error!");
41 return const_cast<Type*>(Ty);
44 Value::Value(Type *ty, unsigned scid)
45 : SubclassID(scid), HasValueHandle(0),
46 SubclassOptionalData(0), SubclassData(0), VTy((Type*)checkType(ty)),
47 UseList(nullptr), Name(nullptr) {
48 // FIXME: Why isn't this in the subclass gunk??
49 // Note, we cannot call isa<CallInst> before the CallInst has been
51 if (SubclassID == Instruction::Call || SubclassID == Instruction::Invoke)
52 assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) &&
53 "invalid CallInst type!");
54 else if (SubclassID != BasicBlockVal &&
55 (SubclassID < ConstantFirstVal || SubclassID > ConstantLastVal))
56 assert((VTy->isFirstClassType() || VTy->isVoidTy()) &&
57 "Cannot create non-first-class values except for constants!");
61 // Notify all ValueHandles (if present) that this value is going away.
63 ValueHandleBase::ValueIsDeleted(this);
65 #ifndef NDEBUG // Only in -g mode...
66 // Check to make sure that there are no uses of this value that are still
67 // around when the value is destroyed. If there are, then we have a dangling
68 // reference and something is wrong. This code is here to print out what is
69 // still being referenced. The value in question should be printed as
73 dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n";
74 for (use_iterator I = use_begin(), E = use_end(); I != E; ++I)
75 dbgs() << "Use still stuck around after Def is destroyed:"
79 assert(use_empty() && "Uses remain when a value is destroyed!");
81 // If this value is named, destroy the name. This should not be in a symtab
83 if (Name && SubclassID != MDStringVal)
86 // There should be no uses of this object anymore, remove it.
87 LeakDetector::removeGarbageObject(this);
90 /// hasNUses - Return true if this Value has exactly N users.
92 bool Value::hasNUses(unsigned N) const {
93 const_use_iterator UI = use_begin(), E = use_end();
96 if (UI == E) return false; // Too few.
100 /// hasNUsesOrMore - Return true if this value has N users or more. This is
101 /// logically equivalent to getNumUses() >= N.
103 bool Value::hasNUsesOrMore(unsigned N) const {
104 const_use_iterator UI = use_begin(), E = use_end();
107 if (UI == E) return false; // Too few.
112 /// isUsedInBasicBlock - Return true if this value is used in the specified
114 bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
115 // This can be computed either by scanning the instructions in BB, or by
116 // scanning the use list of this Value. Both lists can be very long, but
117 // usually one is quite short.
119 // Scan both lists simultaneously until one is exhausted. This limits the
120 // search to the shorter list.
121 BasicBlock::const_iterator BI = BB->begin(), BE = BB->end();
122 const_user_iterator UI = user_begin(), UE = user_end();
123 for (; BI != BE && UI != UE; ++BI, ++UI) {
124 // Scan basic block: Check if this Value is used by the instruction at BI.
125 if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end())
127 // Scan use list: Check if the use at UI is in BB.
128 const Instruction *User = dyn_cast<Instruction>(*UI);
129 if (User && User->getParent() == BB)
136 /// getNumUses - This method computes the number of uses of this Value. This
137 /// is a linear time operation. Use hasOneUse or hasNUses to check for specific
139 unsigned Value::getNumUses() const {
140 return (unsigned)std::distance(use_begin(), use_end());
143 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
145 if (Instruction *I = dyn_cast<Instruction>(V)) {
146 if (BasicBlock *P = I->getParent())
147 if (Function *PP = P->getParent())
148 ST = &PP->getValueSymbolTable();
149 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
150 if (Function *P = BB->getParent())
151 ST = &P->getValueSymbolTable();
152 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
153 if (Module *P = GV->getParent())
154 ST = &P->getValueSymbolTable();
155 } else if (Argument *A = dyn_cast<Argument>(V)) {
156 if (Function *P = A->getParent())
157 ST = &P->getValueSymbolTable();
158 } else if (isa<MDString>(V))
161 assert(isa<Constant>(V) && "Unknown value type!");
162 return true; // no name is setable for this.
167 StringRef Value::getName() const {
168 // Make sure the empty string is still a C string. For historical reasons,
169 // some clients want to call .data() on the result and expect it to be null
171 if (!Name) return StringRef("", 0);
172 return Name->getKey();
175 void Value::setName(const Twine &NewName) {
176 assert(SubclassID != MDStringVal &&
177 "Cannot set the name of MDString with this method!");
179 // Fast path for common IRBuilder case of setName("") when there is no name.
180 if (NewName.isTriviallyEmpty() && !hasName())
183 SmallString<256> NameData;
184 StringRef NameRef = NewName.toStringRef(NameData);
185 assert(NameRef.find_first_of(0) == StringRef::npos &&
186 "Null bytes are not allowed in names");
188 // Name isn't changing?
189 if (getName() == NameRef)
192 assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
194 // Get the symbol table to update for this object.
195 ValueSymbolTable *ST;
196 if (getSymTab(this, ST))
197 return; // Cannot set a name on this value (e.g. constant).
199 if (Function *F = dyn_cast<Function>(this))
200 getContext().pImpl->IntrinsicIDCache.erase(F);
202 if (!ST) { // No symbol table to update? Just do the change.
203 if (NameRef.empty()) {
204 // Free the name for this value.
213 // NOTE: Could optimize for the case the name is shrinking to not deallocate
216 // Create the new name.
217 Name = ValueName::Create(NameRef.begin(), NameRef.end());
218 Name->setValue(this);
222 // NOTE: Could optimize for the case the name is shrinking to not deallocate
226 ST->removeValueName(Name);
234 // Name is changing to something new.
235 Name = ST->createValueName(NameRef, this);
239 /// takeName - transfer the name from V to this value, setting V's name to
240 /// empty. It is an error to call V->takeName(V).
241 void Value::takeName(Value *V) {
242 assert(SubclassID != MDStringVal && "Cannot take the name of an MDString!");
244 ValueSymbolTable *ST = nullptr;
245 // If this value has a name, drop it.
247 // Get the symtab this is in.
248 if (getSymTab(this, ST)) {
249 // We can't set a name on this value, but we need to clear V's name if
251 if (V->hasName()) V->setName("");
252 return; // Cannot set a name on this value (e.g. constant).
257 ST->removeValueName(Name);
262 // Now we know that this has no name.
264 // If V has no name either, we're done.
265 if (!V->hasName()) return;
267 // Get this's symtab if we didn't before.
269 if (getSymTab(this, ST)) {
272 return; // Cannot set a name on this value (e.g. constant).
276 // Get V's ST, this should always succed, because V has a name.
277 ValueSymbolTable *VST;
278 bool Failure = getSymTab(V, VST);
279 assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
281 // If these values are both in the same symtab, we can do this very fast.
282 // This works even if both values have no symtab yet.
287 Name->setValue(this);
291 // Otherwise, things are slightly more complex. Remove V's name from VST and
292 // then reinsert it into ST.
295 VST->removeValueName(V->Name);
298 Name->setValue(this);
301 ST->reinsertValue(this);
304 static GlobalObject &findReplacementForAliasUse(Value &C) {
305 if (auto *GO = dyn_cast<GlobalObject>(&C))
307 if (auto *GA = dyn_cast<GlobalAlias>(&C))
308 return *GA->getAliasee();
309 auto *CE = cast<ConstantExpr>(&C);
310 assert(CE->getOpcode() == Instruction::BitCast ||
311 CE->getOpcode() == Instruction::GetElementPtr ||
312 CE->getOpcode() == Instruction::AddrSpaceCast);
313 if (CE->getOpcode() == Instruction::GetElementPtr)
314 assert(cast<GEPOperator>(CE)->hasAllZeroIndices());
315 return findReplacementForAliasUse(*CE->getOperand(0));
318 static void replaceAliasUseWith(Use &U, Value *New) {
319 GlobalObject &Replacement = findReplacementForAliasUse(*New);
320 auto *Old = &cast<GlobalObject>(*U);
321 assert(Old != &Replacement &&
322 "replaceAliasUseWith cannot form an alias cycle");
327 static bool contains(SmallPtrSet<ConstantExpr *, 4> &Cache, ConstantExpr *Expr,
329 if (!Cache.insert(Expr))
332 for (auto &O : Expr->operands()) {
335 auto *CE = dyn_cast<ConstantExpr>(O);
338 if (contains(Cache, CE, C))
344 static bool contains(Value *Expr, Value *V) {
348 auto *C = dyn_cast<Constant>(V);
352 auto *CE = dyn_cast<ConstantExpr>(Expr);
356 SmallPtrSet<ConstantExpr *, 4> Cache;
357 return contains(Cache, CE, C);
361 void Value::replaceAllUsesWith(Value *New) {
362 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
363 assert(!contains(New, this) &&
364 "this->replaceAllUsesWith(expr(this)) is NOT valid!");
365 assert(New->getType() == getType() &&
366 "replaceAllUses of value with new value of different type!");
368 // Notify all ValueHandles (if present) that this value is going away.
370 ValueHandleBase::ValueIsRAUWd(this, New);
372 while (!use_empty()) {
374 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
375 // constant because they are uniqued.
376 if (auto *C = dyn_cast<Constant>(U.getUser())) {
377 if (isa<GlobalAlias>(C)) {
378 replaceAliasUseWith(U, New);
381 if (!isa<GlobalValue>(C)) {
382 C->replaceUsesOfWithOnConstant(this, New, &U);
390 if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
391 BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
395 // Various metrics for how much to strip off of pointers.
396 enum PointerStripKind {
398 PSK_ZeroIndicesAndAliases,
399 PSK_InBoundsConstantIndices,
403 template <PointerStripKind StripKind>
404 static Value *stripPointerCastsAndOffsets(Value *V) {
405 if (!V->getType()->isPointerTy())
408 // Even though we don't look through PHI nodes, we could be called on an
409 // instruction in an unreachable block, which may be on a cycle.
410 SmallPtrSet<Value *, 4> Visited;
414 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
416 case PSK_ZeroIndicesAndAliases:
417 case PSK_ZeroIndices:
418 if (!GEP->hasAllZeroIndices())
421 case PSK_InBoundsConstantIndices:
422 if (!GEP->hasAllConstantIndices())
426 if (!GEP->isInBounds())
430 V = GEP->getPointerOperand();
431 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
432 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
433 V = cast<Operator>(V)->getOperand(0);
434 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
435 if (StripKind == PSK_ZeroIndices || GA->mayBeOverridden())
437 V = GA->getAliasee();
441 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
442 } while (Visited.insert(V));
448 Value *Value::stripPointerCasts() {
449 return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
452 Value *Value::stripPointerCastsNoFollowAliases() {
453 return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
456 Value *Value::stripInBoundsConstantOffsets() {
457 return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
460 Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
462 if (!getType()->isPointerTy())
465 assert(Offset.getBitWidth() == DL.getPointerSizeInBits(cast<PointerType>(
466 getType())->getAddressSpace()) &&
467 "The offset must have exactly as many bits as our pointer.");
469 // Even though we don't look through PHI nodes, we could be called on an
470 // instruction in an unreachable block, which may be on a cycle.
471 SmallPtrSet<Value *, 4> Visited;
472 Visited.insert(this);
475 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
476 if (!GEP->isInBounds())
478 APInt GEPOffset(Offset);
479 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
482 V = GEP->getPointerOperand();
483 } else if (Operator::getOpcode(V) == Instruction::BitCast) {
484 V = cast<Operator>(V)->getOperand(0);
485 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
486 V = GA->getAliasee();
490 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
491 } while (Visited.insert(V));
496 Value *Value::stripInBoundsOffsets() {
497 return stripPointerCastsAndOffsets<PSK_InBounds>(this);
500 /// isDereferenceablePointer - Test if this value is always a pointer to
501 /// allocated and suitably aligned memory for a simple load or store.
502 static bool isDereferenceablePointer(const Value *V,
503 SmallPtrSet<const Value *, 32> &Visited) {
504 // Note that it is not safe to speculate into a malloc'd region because
505 // malloc may return null.
506 // It's also not always safe to follow a bitcast, for example:
507 // bitcast i8* (alloca i8) to i32*
508 // would result in a 4-byte load from a 1-byte alloca. Some cases could
509 // be handled using DataLayout to check sizes and alignments though.
511 // These are obviously ok.
512 if (isa<AllocaInst>(V)) return true;
514 // Global variables which can't collapse to null are ok.
515 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
516 return !GV->hasExternalWeakLinkage();
518 // byval arguments are ok.
519 if (const Argument *A = dyn_cast<Argument>(V))
520 return A->hasByValAttr();
522 // For GEPs, determine if the indexing lands within the allocated object.
523 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
524 // Conservatively require that the base pointer be fully dereferenceable.
525 if (!Visited.insert(GEP->getOperand(0)))
527 if (!isDereferenceablePointer(GEP->getOperand(0), Visited))
529 // Check the indices.
530 gep_type_iterator GTI = gep_type_begin(GEP);
531 for (User::const_op_iterator I = GEP->op_begin()+1,
532 E = GEP->op_end(); I != E; ++I) {
535 // Struct indices can't be out of bounds.
536 if (isa<StructType>(Ty))
538 ConstantInt *CI = dyn_cast<ConstantInt>(Index);
541 // Zero is always ok.
544 // Check to see that it's within the bounds of an array.
545 ArrayType *ATy = dyn_cast<ArrayType>(Ty);
548 if (CI->getValue().getActiveBits() > 64)
550 if (CI->getZExtValue() >= ATy->getNumElements())
553 // Indices check out; this is dereferenceable.
557 // If we don't know, assume the worst.
561 /// isDereferenceablePointer - Test if this value is always a pointer to
562 /// allocated and suitably aligned memory for a simple load or store.
563 bool Value::isDereferenceablePointer() const {
564 SmallPtrSet<const Value *, 32> Visited;
565 return ::isDereferenceablePointer(this, Visited);
568 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
569 /// return the value in the PHI node corresponding to PredBB. If not, return
570 /// ourself. This is useful if you want to know the value something has in a
571 /// predecessor block.
572 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
573 const BasicBlock *PredBB) {
574 PHINode *PN = dyn_cast<PHINode>(this);
575 if (PN && PN->getParent() == CurBB)
576 return PN->getIncomingValueForBlock(PredBB);
580 LLVMContext &Value::getContext() const { return VTy->getContext(); }
582 //===----------------------------------------------------------------------===//
583 // ValueHandleBase Class
584 //===----------------------------------------------------------------------===//
586 /// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
587 /// List is known to point into the existing use list.
588 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
589 assert(List && "Handle list is null?");
591 // Splice ourselves into the list.
596 Next->setPrevPtr(&Next);
597 assert(VP.getPointer() == Next->VP.getPointer() && "Added to wrong list?");
601 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
602 assert(List && "Must insert after existing node");
605 setPrevPtr(&List->Next);
608 Next->setPrevPtr(&Next);
611 /// AddToUseList - Add this ValueHandle to the use list for VP.
612 void ValueHandleBase::AddToUseList() {
613 assert(VP.getPointer() && "Null pointer doesn't have a use list!");
615 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
617 if (VP.getPointer()->HasValueHandle) {
618 // If this value already has a ValueHandle, then it must be in the
619 // ValueHandles map already.
620 ValueHandleBase *&Entry = pImpl->ValueHandles[VP.getPointer()];
621 assert(Entry && "Value doesn't have any handles?");
622 AddToExistingUseList(&Entry);
626 // Ok, it doesn't have any handles yet, so we must insert it into the
627 // DenseMap. However, doing this insertion could cause the DenseMap to
628 // reallocate itself, which would invalidate all of the PrevP pointers that
629 // point into the old table. Handle this by checking for reallocation and
630 // updating the stale pointers only if needed.
631 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
632 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
634 ValueHandleBase *&Entry = Handles[VP.getPointer()];
635 assert(!Entry && "Value really did already have handles?");
636 AddToExistingUseList(&Entry);
637 VP.getPointer()->HasValueHandle = true;
639 // If reallocation didn't happen or if this was the first insertion, don't
641 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
642 Handles.size() == 1) {
646 // Okay, reallocation did happen. Fix the Prev Pointers.
647 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
648 E = Handles.end(); I != E; ++I) {
649 assert(I->second && I->first == I->second->VP.getPointer() &&
650 "List invariant broken!");
651 I->second->setPrevPtr(&I->second);
655 /// RemoveFromUseList - Remove this ValueHandle from its current use list.
656 void ValueHandleBase::RemoveFromUseList() {
657 assert(VP.getPointer() && VP.getPointer()->HasValueHandle &&
658 "Pointer doesn't have a use list!");
660 // Unlink this from its use list.
661 ValueHandleBase **PrevPtr = getPrevPtr();
662 assert(*PrevPtr == this && "List invariant broken");
666 assert(Next->getPrevPtr() == &Next && "List invariant broken");
667 Next->setPrevPtr(PrevPtr);
671 // If the Next pointer was null, then it is possible that this was the last
672 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
674 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
675 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
676 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
677 Handles.erase(VP.getPointer());
678 VP.getPointer()->HasValueHandle = false;
683 void ValueHandleBase::ValueIsDeleted(Value *V) {
684 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
686 // Get the linked list base, which is guaranteed to exist since the
687 // HasValueHandle flag is set.
688 LLVMContextImpl *pImpl = V->getContext().pImpl;
689 ValueHandleBase *Entry = pImpl->ValueHandles[V];
690 assert(Entry && "Value bit set but no entries exist");
692 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
693 // and remove themselves from the list without breaking our iteration. This
694 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
695 // Note that we deliberately do not the support the case when dropping a value
696 // handle results in a new value handle being permanently added to the list
697 // (as might occur in theory for CallbackVH's): the new value handle will not
698 // be processed and the checking code will mete out righteous punishment if
699 // the handle is still present once we have finished processing all the other
700 // value handles (it is fine to momentarily add then remove a value handle).
701 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
702 Iterator.RemoveFromUseList();
703 Iterator.AddToExistingUseListAfter(Entry);
704 assert(Entry->Next == &Iterator && "Loop invariant broken.");
706 switch (Entry->getKind()) {
710 // Mark that this value has been deleted by setting it to an invalid Value
712 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
715 // Weak just goes to null, which will unlink it from the list.
716 Entry->operator=(nullptr);
719 // Forward to the subclass's implementation.
720 static_cast<CallbackVH*>(Entry)->deleted();
725 // All callbacks, weak references, and assertingVHs should be dropped by now.
726 if (V->HasValueHandle) {
727 #ifndef NDEBUG // Only in +Asserts mode...
728 dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
730 if (pImpl->ValueHandles[V]->getKind() == Assert)
731 llvm_unreachable("An asserting value handle still pointed to this"
735 llvm_unreachable("All references to V were not removed?");
740 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
741 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
742 assert(Old != New && "Changing value into itself!");
744 // Get the linked list base, which is guaranteed to exist since the
745 // HasValueHandle flag is set.
746 LLVMContextImpl *pImpl = Old->getContext().pImpl;
747 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
749 assert(Entry && "Value bit set but no entries exist");
751 // We use a local ValueHandleBase as an iterator so that
752 // ValueHandles can add and remove themselves from the list without
753 // breaking our iteration. This is not really an AssertingVH; we
754 // just have to give ValueHandleBase some kind.
755 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
756 Iterator.RemoveFromUseList();
757 Iterator.AddToExistingUseListAfter(Entry);
758 assert(Entry->Next == &Iterator && "Loop invariant broken.");
760 switch (Entry->getKind()) {
762 // Asserting handle does not follow RAUW implicitly.
765 // Tracking goes to new value like a WeakVH. Note that this may make it
766 // something incompatible with its templated type. We don't want to have a
767 // virtual (or inline) interface to handle this though, so instead we make
768 // the TrackingVH accessors guarantee that a client never sees this value.
772 // Weak goes to the new value, which will unlink it from Old's list.
773 Entry->operator=(New);
776 // Forward to the subclass's implementation.
777 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
783 // If any new tracking or weak value handles were added while processing the
784 // list, then complain about it now.
785 if (Old->HasValueHandle)
786 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
787 switch (Entry->getKind()) {
790 dbgs() << "After RAUW from " << *Old->getType() << " %"
791 << Old->getName() << " to " << *New->getType() << " %"
792 << New->getName() << "\n";
793 llvm_unreachable("A tracking or weak value handle still pointed to the"
801 // Pin the vtable to this file.
802 void CallbackVH::anchor() {}