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/CallSite.h"
19 #include "llvm/IR/Constant.h"
20 #include "llvm/IR/Constants.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/DerivedTypes.h"
23 #include "llvm/IR/GetElementPtrTypeIterator.h"
24 #include "llvm/IR/InstrTypes.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/LeakDetector.h"
27 #include "llvm/IR/Module.h"
28 #include "llvm/IR/Operator.h"
29 #include "llvm/IR/ValueHandle.h"
30 #include "llvm/IR/ValueSymbolTable.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/ManagedStatic.h"
37 //===----------------------------------------------------------------------===//
39 //===----------------------------------------------------------------------===//
41 static inline Type *checkType(Type *Ty) {
42 assert(Ty && "Value defined with a null type: Error!");
46 Value::Value(Type *ty, unsigned scid)
47 : VTy(checkType(ty)), UseList(nullptr), Name(nullptr), SubclassID(scid),
48 HasValueHandle(0), SubclassOptionalData(0), SubclassData(0) {
49 // FIXME: Why isn't this in the subclass gunk??
50 // Note, we cannot call isa<CallInst> before the CallInst has been
52 if (SubclassID == Instruction::Call || SubclassID == Instruction::Invoke)
53 assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) &&
54 "invalid CallInst type!");
55 else if (SubclassID != BasicBlockVal &&
56 (SubclassID < ConstantFirstVal || SubclassID > ConstantLastVal))
57 assert((VTy->isFirstClassType() || VTy->isVoidTy()) &&
58 "Cannot create non-first-class values except for constants!");
62 // Notify all ValueHandles (if present) that this value is going away.
64 ValueHandleBase::ValueIsDeleted(this);
66 #ifndef NDEBUG // Only in -g mode...
67 // Check to make sure that there are no uses of this value that are still
68 // around when the value is destroyed. If there are, then we have a dangling
69 // reference and something is wrong. This code is here to print out what is
70 // still being referenced. The value in question should be printed as
74 dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n";
75 for (use_iterator I = use_begin(), E = use_end(); I != E; ++I)
76 dbgs() << "Use still stuck around after Def is destroyed:"
80 assert(use_empty() && "Uses remain when a value is destroyed!");
82 // If this value is named, destroy the name. This should not be in a symtab
84 if (Name && SubclassID != MDStringVal)
87 // There should be no uses of this object anymore, remove it.
88 LeakDetector::removeGarbageObject(this);
91 bool Value::hasNUses(unsigned N) const {
92 const_use_iterator UI = use_begin(), E = use_end();
95 if (UI == E) return false; // Too few.
99 bool Value::hasNUsesOrMore(unsigned N) const {
100 const_use_iterator UI = use_begin(), E = use_end();
103 if (UI == E) return false; // Too few.
108 bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
109 // This can be computed either by scanning the instructions in BB, or by
110 // scanning the use list of this Value. Both lists can be very long, but
111 // usually one is quite short.
113 // Scan both lists simultaneously until one is exhausted. This limits the
114 // search to the shorter list.
115 BasicBlock::const_iterator BI = BB->begin(), BE = BB->end();
116 const_user_iterator UI = user_begin(), UE = user_end();
117 for (; BI != BE && UI != UE; ++BI, ++UI) {
118 // Scan basic block: Check if this Value is used by the instruction at BI.
119 if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end())
121 // Scan use list: Check if the use at UI is in BB.
122 const Instruction *User = dyn_cast<Instruction>(*UI);
123 if (User && User->getParent() == BB)
129 unsigned Value::getNumUses() const {
130 return (unsigned)std::distance(use_begin(), use_end());
133 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
135 if (Instruction *I = dyn_cast<Instruction>(V)) {
136 if (BasicBlock *P = I->getParent())
137 if (Function *PP = P->getParent())
138 ST = &PP->getValueSymbolTable();
139 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
140 if (Function *P = BB->getParent())
141 ST = &P->getValueSymbolTable();
142 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
143 if (Module *P = GV->getParent())
144 ST = &P->getValueSymbolTable();
145 } else if (Argument *A = dyn_cast<Argument>(V)) {
146 if (Function *P = A->getParent())
147 ST = &P->getValueSymbolTable();
148 } else if (isa<MDString>(V))
151 assert(isa<Constant>(V) && "Unknown value type!");
152 return true; // no name is setable for this.
157 StringRef Value::getName() const {
158 // Make sure the empty string is still a C string. For historical reasons,
159 // some clients want to call .data() on the result and expect it to be null
161 if (!Name) return StringRef("", 0);
162 return Name->getKey();
165 void Value::setName(const Twine &NewName) {
166 assert(SubclassID != MDStringVal &&
167 "Cannot set the name of MDString with this method!");
169 // Fast path for common IRBuilder case of setName("") when there is no name.
170 if (NewName.isTriviallyEmpty() && !hasName())
173 SmallString<256> NameData;
174 StringRef NameRef = NewName.toStringRef(NameData);
175 assert(NameRef.find_first_of(0) == StringRef::npos &&
176 "Null bytes are not allowed in names");
178 // Name isn't changing?
179 if (getName() == NameRef)
182 assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
184 // Get the symbol table to update for this object.
185 ValueSymbolTable *ST;
186 if (getSymTab(this, ST))
187 return; // Cannot set a name on this value (e.g. constant).
189 if (Function *F = dyn_cast<Function>(this))
190 getContext().pImpl->IntrinsicIDCache.erase(F);
192 if (!ST) { // No symbol table to update? Just do the change.
193 if (NameRef.empty()) {
194 // Free the name for this value.
203 // NOTE: Could optimize for the case the name is shrinking to not deallocate
206 // Create the new name.
207 Name = ValueName::Create(NameRef);
208 Name->setValue(this);
212 // NOTE: Could optimize for the case the name is shrinking to not deallocate
216 ST->removeValueName(Name);
224 // Name is changing to something new.
225 Name = ST->createValueName(NameRef, this);
228 void Value::takeName(Value *V) {
229 assert(SubclassID != MDStringVal && "Cannot take the name of an MDString!");
231 ValueSymbolTable *ST = nullptr;
232 // If this value has a name, drop it.
234 // Get the symtab this is in.
235 if (getSymTab(this, ST)) {
236 // We can't set a name on this value, but we need to clear V's name if
238 if (V->hasName()) V->setName("");
239 return; // Cannot set a name on this value (e.g. constant).
244 ST->removeValueName(Name);
249 // Now we know that this has no name.
251 // If V has no name either, we're done.
252 if (!V->hasName()) return;
254 // Get this's symtab if we didn't before.
256 if (getSymTab(this, ST)) {
259 return; // Cannot set a name on this value (e.g. constant).
263 // Get V's ST, this should always succed, because V has a name.
264 ValueSymbolTable *VST;
265 bool Failure = getSymTab(V, VST);
266 assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
268 // If these values are both in the same symtab, we can do this very fast.
269 // This works even if both values have no symtab yet.
274 Name->setValue(this);
278 // Otherwise, things are slightly more complex. Remove V's name from VST and
279 // then reinsert it into ST.
282 VST->removeValueName(V->Name);
285 Name->setValue(this);
288 ST->reinsertValue(this);
292 static bool contains(SmallPtrSetImpl<ConstantExpr *> &Cache, ConstantExpr *Expr,
294 if (!Cache.insert(Expr))
297 for (auto &O : Expr->operands()) {
300 auto *CE = dyn_cast<ConstantExpr>(O);
303 if (contains(Cache, CE, C))
309 static bool contains(Value *Expr, Value *V) {
313 auto *C = dyn_cast<Constant>(V);
317 auto *CE = dyn_cast<ConstantExpr>(Expr);
321 SmallPtrSet<ConstantExpr *, 4> Cache;
322 return contains(Cache, CE, C);
326 void Value::replaceAllUsesWith(Value *New) {
327 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
328 assert(!contains(New, this) &&
329 "this->replaceAllUsesWith(expr(this)) is NOT valid!");
330 assert(New->getType() == getType() &&
331 "replaceAllUses of value with new value of different type!");
333 // Notify all ValueHandles (if present) that this value is going away.
335 ValueHandleBase::ValueIsRAUWd(this, New);
337 while (!use_empty()) {
339 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
340 // constant because they are uniqued.
341 if (auto *C = dyn_cast<Constant>(U.getUser())) {
342 if (!isa<GlobalValue>(C)) {
343 C->replaceUsesOfWithOnConstant(this, New, &U);
351 if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
352 BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
356 // Various metrics for how much to strip off of pointers.
357 enum PointerStripKind {
359 PSK_ZeroIndicesAndAliases,
360 PSK_InBoundsConstantIndices,
364 template <PointerStripKind StripKind>
365 static Value *stripPointerCastsAndOffsets(Value *V) {
366 if (!V->getType()->isPointerTy())
369 // Even though we don't look through PHI nodes, we could be called on an
370 // instruction in an unreachable block, which may be on a cycle.
371 SmallPtrSet<Value *, 4> Visited;
375 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
377 case PSK_ZeroIndicesAndAliases:
378 case PSK_ZeroIndices:
379 if (!GEP->hasAllZeroIndices())
382 case PSK_InBoundsConstantIndices:
383 if (!GEP->hasAllConstantIndices())
387 if (!GEP->isInBounds())
391 V = GEP->getPointerOperand();
392 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
393 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
394 V = cast<Operator>(V)->getOperand(0);
395 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
396 if (StripKind == PSK_ZeroIndices || GA->mayBeOverridden())
398 V = GA->getAliasee();
402 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
403 } while (Visited.insert(V));
409 Value *Value::stripPointerCasts() {
410 return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
413 Value *Value::stripPointerCastsNoFollowAliases() {
414 return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
417 Value *Value::stripInBoundsConstantOffsets() {
418 return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
421 Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
423 if (!getType()->isPointerTy())
426 assert(Offset.getBitWidth() == DL.getPointerSizeInBits(cast<PointerType>(
427 getType())->getAddressSpace()) &&
428 "The offset must have exactly as many bits as our pointer.");
430 // Even though we don't look through PHI nodes, we could be called on an
431 // instruction in an unreachable block, which may be on a cycle.
432 SmallPtrSet<Value *, 4> Visited;
433 Visited.insert(this);
436 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
437 if (!GEP->isInBounds())
439 APInt GEPOffset(Offset);
440 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
443 V = GEP->getPointerOperand();
444 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
445 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
446 V = cast<Operator>(V)->getOperand(0);
447 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
448 V = GA->getAliasee();
452 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
453 } while (Visited.insert(V));
458 Value *Value::stripInBoundsOffsets() {
459 return stripPointerCastsAndOffsets<PSK_InBounds>(this);
462 /// \brief Check if Value is always a dereferenceable pointer.
464 /// Test if V is always a pointer to allocated and suitably aligned memory for
465 /// a simple load or store.
466 static bool isDereferenceablePointer(const Value *V, const DataLayout *DL,
467 SmallPtrSetImpl<const Value *> &Visited) {
468 // Note that it is not safe to speculate into a malloc'd region because
469 // malloc may return null.
471 // These are obviously ok.
472 if (isa<AllocaInst>(V)) return true;
474 // It's not always safe to follow a bitcast, for example:
475 // bitcast i8* (alloca i8) to i32*
476 // would result in a 4-byte load from a 1-byte alloca. However,
477 // if we're casting from a pointer from a type of larger size
478 // to a type of smaller size (or the same size), and the alignment
479 // is at least as large as for the resulting pointer type, then
480 // we can look through the bitcast.
482 if (const BitCastInst* BC = dyn_cast<BitCastInst>(V)) {
483 Type *STy = BC->getSrcTy()->getPointerElementType(),
484 *DTy = BC->getDestTy()->getPointerElementType();
485 if (STy->isSized() && DTy->isSized() &&
486 (DL->getTypeStoreSize(STy) >=
487 DL->getTypeStoreSize(DTy)) &&
488 (DL->getABITypeAlignment(STy) >=
489 DL->getABITypeAlignment(DTy)))
490 return isDereferenceablePointer(BC->getOperand(0), DL, Visited);
493 // Global variables which can't collapse to null are ok.
494 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
495 return !GV->hasExternalWeakLinkage();
497 // byval arguments are okay. Arguments specifically marked as
498 // dereferenceable are okay too.
499 if (const Argument *A = dyn_cast<Argument>(V)) {
500 if (A->hasByValAttr())
502 else if (uint64_t Bytes = A->getDereferenceableBytes()) {
503 Type *Ty = V->getType()->getPointerElementType();
504 if (Ty->isSized() && DL && DL->getTypeStoreSize(Ty) <= Bytes)
511 // Return values from call sites specifically marked as dereferenceable are
513 if (ImmutableCallSite CS = V) {
514 if (uint64_t Bytes = CS.getDereferenceableBytes(0)) {
515 Type *Ty = V->getType()->getPointerElementType();
516 if (Ty->isSized() && DL && DL->getTypeStoreSize(Ty) <= Bytes)
521 // For GEPs, determine if the indexing lands within the allocated object.
522 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
523 // Conservatively require that the base pointer be fully dereferenceable.
524 if (!Visited.insert(GEP->getOperand(0)))
526 if (!isDereferenceablePointer(GEP->getOperand(0), DL, Visited))
528 // Check the indices.
529 gep_type_iterator GTI = gep_type_begin(GEP);
530 for (User::const_op_iterator I = GEP->op_begin()+1,
531 E = GEP->op_end(); I != E; ++I) {
534 // Struct indices can't be out of bounds.
535 if (isa<StructType>(Ty))
537 ConstantInt *CI = dyn_cast<ConstantInt>(Index);
540 // Zero is always ok.
543 // Check to see that it's within the bounds of an array.
544 ArrayType *ATy = dyn_cast<ArrayType>(Ty);
547 if (CI->getValue().getActiveBits() > 64)
549 if (CI->getZExtValue() >= ATy->getNumElements())
552 // Indices check out; this is dereferenceable.
556 if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
557 return isDereferenceablePointer(ASC->getOperand(0), DL, Visited);
559 // If we don't know, assume the worst.
563 bool Value::isDereferenceablePointer(const DataLayout *DL) const {
564 // When dereferenceability information is provided by a dereferenceable
565 // attribute, we know exactly how many bytes are dereferenceable. If we can
566 // determine the exact offset to the attributed variable, we can use that
568 Type *Ty = getType()->getPointerElementType();
569 if (Ty->isSized() && DL) {
570 APInt Offset(DL->getTypeStoreSizeInBits(getType()), 0);
571 const Value *BV = stripAndAccumulateInBoundsConstantOffsets(*DL, Offset);
573 APInt DerefBytes(Offset.getBitWidth(), 0);
574 if (const Argument *A = dyn_cast<Argument>(BV))
575 DerefBytes = A->getDereferenceableBytes();
576 else if (ImmutableCallSite CS = BV)
577 DerefBytes = CS.getDereferenceableBytes(0);
579 if (DerefBytes.getBoolValue() && Offset.isNonNegative()) {
580 if (DerefBytes.uge(Offset + DL->getTypeStoreSize(Ty)))
585 SmallPtrSet<const Value *, 32> Visited;
586 return ::isDereferenceablePointer(this, DL, Visited);
589 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
590 const BasicBlock *PredBB) {
591 PHINode *PN = dyn_cast<PHINode>(this);
592 if (PN && PN->getParent() == CurBB)
593 return PN->getIncomingValueForBlock(PredBB);
597 LLVMContext &Value::getContext() const { return VTy->getContext(); }
599 void Value::reverseUseList() {
600 if (!UseList || !UseList->Next)
601 // No need to reverse 0 or 1 uses.
605 Use *Current = UseList->Next;
606 Head->Next = nullptr;
608 Use *Next = Current->Next;
609 Current->Next = Head;
610 Head->setPrev(&Current->Next);
615 Head->setPrev(&UseList);
618 //===----------------------------------------------------------------------===//
619 // ValueHandleBase Class
620 //===----------------------------------------------------------------------===//
622 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
623 assert(List && "Handle list is null?");
625 // Splice ourselves into the list.
630 Next->setPrevPtr(&Next);
631 assert(VP.getPointer() == Next->VP.getPointer() && "Added to wrong list?");
635 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
636 assert(List && "Must insert after existing node");
639 setPrevPtr(&List->Next);
642 Next->setPrevPtr(&Next);
645 void ValueHandleBase::AddToUseList() {
646 assert(VP.getPointer() && "Null pointer doesn't have a use list!");
648 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
650 if (VP.getPointer()->HasValueHandle) {
651 // If this value already has a ValueHandle, then it must be in the
652 // ValueHandles map already.
653 ValueHandleBase *&Entry = pImpl->ValueHandles[VP.getPointer()];
654 assert(Entry && "Value doesn't have any handles?");
655 AddToExistingUseList(&Entry);
659 // Ok, it doesn't have any handles yet, so we must insert it into the
660 // DenseMap. However, doing this insertion could cause the DenseMap to
661 // reallocate itself, which would invalidate all of the PrevP pointers that
662 // point into the old table. Handle this by checking for reallocation and
663 // updating the stale pointers only if needed.
664 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
665 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
667 ValueHandleBase *&Entry = Handles[VP.getPointer()];
668 assert(!Entry && "Value really did already have handles?");
669 AddToExistingUseList(&Entry);
670 VP.getPointer()->HasValueHandle = true;
672 // If reallocation didn't happen or if this was the first insertion, don't
674 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
675 Handles.size() == 1) {
679 // Okay, reallocation did happen. Fix the Prev Pointers.
680 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
681 E = Handles.end(); I != E; ++I) {
682 assert(I->second && I->first == I->second->VP.getPointer() &&
683 "List invariant broken!");
684 I->second->setPrevPtr(&I->second);
688 void ValueHandleBase::RemoveFromUseList() {
689 assert(VP.getPointer() && VP.getPointer()->HasValueHandle &&
690 "Pointer doesn't have a use list!");
692 // Unlink this from its use list.
693 ValueHandleBase **PrevPtr = getPrevPtr();
694 assert(*PrevPtr == this && "List invariant broken");
698 assert(Next->getPrevPtr() == &Next && "List invariant broken");
699 Next->setPrevPtr(PrevPtr);
703 // If the Next pointer was null, then it is possible that this was the last
704 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
706 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
707 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
708 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
709 Handles.erase(VP.getPointer());
710 VP.getPointer()->HasValueHandle = false;
715 void ValueHandleBase::ValueIsDeleted(Value *V) {
716 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
718 // Get the linked list base, which is guaranteed to exist since the
719 // HasValueHandle flag is set.
720 LLVMContextImpl *pImpl = V->getContext().pImpl;
721 ValueHandleBase *Entry = pImpl->ValueHandles[V];
722 assert(Entry && "Value bit set but no entries exist");
724 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
725 // and remove themselves from the list without breaking our iteration. This
726 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
727 // Note that we deliberately do not the support the case when dropping a value
728 // handle results in a new value handle being permanently added to the list
729 // (as might occur in theory for CallbackVH's): the new value handle will not
730 // be processed and the checking code will mete out righteous punishment if
731 // the handle is still present once we have finished processing all the other
732 // value handles (it is fine to momentarily add then remove a value handle).
733 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
734 Iterator.RemoveFromUseList();
735 Iterator.AddToExistingUseListAfter(Entry);
736 assert(Entry->Next == &Iterator && "Loop invariant broken.");
738 switch (Entry->getKind()) {
742 // Mark that this value has been deleted by setting it to an invalid Value
744 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
747 // Weak just goes to null, which will unlink it from the list.
748 Entry->operator=(nullptr);
751 // Forward to the subclass's implementation.
752 static_cast<CallbackVH*>(Entry)->deleted();
757 // All callbacks, weak references, and assertingVHs should be dropped by now.
758 if (V->HasValueHandle) {
759 #ifndef NDEBUG // Only in +Asserts mode...
760 dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
762 if (pImpl->ValueHandles[V]->getKind() == Assert)
763 llvm_unreachable("An asserting value handle still pointed to this"
767 llvm_unreachable("All references to V were not removed?");
772 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
773 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
774 assert(Old != New && "Changing value into itself!");
776 // Get the linked list base, which is guaranteed to exist since the
777 // HasValueHandle flag is set.
778 LLVMContextImpl *pImpl = Old->getContext().pImpl;
779 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
781 assert(Entry && "Value bit set but no entries exist");
783 // We use a local ValueHandleBase as an iterator so that
784 // ValueHandles can add and remove themselves from the list without
785 // breaking our iteration. This is not really an AssertingVH; we
786 // just have to give ValueHandleBase some kind.
787 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
788 Iterator.RemoveFromUseList();
789 Iterator.AddToExistingUseListAfter(Entry);
790 assert(Entry->Next == &Iterator && "Loop invariant broken.");
792 switch (Entry->getKind()) {
794 // Asserting handle does not follow RAUW implicitly.
797 // Tracking goes to new value like a WeakVH. Note that this may make it
798 // something incompatible with its templated type. We don't want to have a
799 // virtual (or inline) interface to handle this though, so instead we make
800 // the TrackingVH accessors guarantee that a client never sees this value.
804 // Weak goes to the new value, which will unlink it from Old's list.
805 Entry->operator=(New);
808 // Forward to the subclass's implementation.
809 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
815 // If any new tracking or weak value handles were added while processing the
816 // list, then complain about it now.
817 if (Old->HasValueHandle)
818 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
819 switch (Entry->getKind()) {
822 dbgs() << "After RAUW from " << *Old->getType() << " %"
823 << Old->getName() << " to " << *New->getType() << " %"
824 << New->getName() << "\n";
825 llvm_unreachable("A tracking or weak value handle still pointed to the"
833 // Pin the vtable to this file.
834 void CallbackVH::anchor() {}