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 /// hasNUses - Return true if this Value has exactly N users.
93 bool Value::hasNUses(unsigned N) const {
94 const_use_iterator UI = use_begin(), E = use_end();
97 if (UI == E) return false; // Too few.
101 /// hasNUsesOrMore - Return true if this value has N users or more. This is
102 /// logically equivalent to getNumUses() >= N.
104 bool Value::hasNUsesOrMore(unsigned N) const {
105 const_use_iterator UI = use_begin(), E = use_end();
108 if (UI == E) return false; // Too few.
113 /// isUsedInBasicBlock - Return true if this value is used in the specified
115 bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
116 // This can be computed either by scanning the instructions in BB, or by
117 // scanning the use list of this Value. Both lists can be very long, but
118 // usually one is quite short.
120 // Scan both lists simultaneously until one is exhausted. This limits the
121 // search to the shorter list.
122 BasicBlock::const_iterator BI = BB->begin(), BE = BB->end();
123 const_user_iterator UI = user_begin(), UE = user_end();
124 for (; BI != BE && UI != UE; ++BI, ++UI) {
125 // Scan basic block: Check if this Value is used by the instruction at BI.
126 if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end())
128 // Scan use list: Check if the use at UI is in BB.
129 const Instruction *User = dyn_cast<Instruction>(*UI);
130 if (User && User->getParent() == BB)
137 /// getNumUses - This method computes the number of uses of this Value. This
138 /// is a linear time operation. Use hasOneUse or hasNUses to check for specific
140 unsigned Value::getNumUses() const {
141 return (unsigned)std::distance(use_begin(), use_end());
144 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
146 if (Instruction *I = dyn_cast<Instruction>(V)) {
147 if (BasicBlock *P = I->getParent())
148 if (Function *PP = P->getParent())
149 ST = &PP->getValueSymbolTable();
150 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
151 if (Function *P = BB->getParent())
152 ST = &P->getValueSymbolTable();
153 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
154 if (Module *P = GV->getParent())
155 ST = &P->getValueSymbolTable();
156 } else if (Argument *A = dyn_cast<Argument>(V)) {
157 if (Function *P = A->getParent())
158 ST = &P->getValueSymbolTable();
159 } else if (isa<MDString>(V))
162 assert(isa<Constant>(V) && "Unknown value type!");
163 return true; // no name is setable for this.
168 StringRef Value::getName() const {
169 // Make sure the empty string is still a C string. For historical reasons,
170 // some clients want to call .data() on the result and expect it to be null
172 if (!Name) return StringRef("", 0);
173 return Name->getKey();
176 void Value::setName(const Twine &NewName) {
177 assert(SubclassID != MDStringVal &&
178 "Cannot set the name of MDString with this method!");
180 // Fast path for common IRBuilder case of setName("") when there is no name.
181 if (NewName.isTriviallyEmpty() && !hasName())
184 SmallString<256> NameData;
185 StringRef NameRef = NewName.toStringRef(NameData);
186 assert(NameRef.find_first_of(0) == StringRef::npos &&
187 "Null bytes are not allowed in names");
189 // Name isn't changing?
190 if (getName() == NameRef)
193 assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
195 // Get the symbol table to update for this object.
196 ValueSymbolTable *ST;
197 if (getSymTab(this, ST))
198 return; // Cannot set a name on this value (e.g. constant).
200 if (Function *F = dyn_cast<Function>(this))
201 getContext().pImpl->IntrinsicIDCache.erase(F);
203 if (!ST) { // No symbol table to update? Just do the change.
204 if (NameRef.empty()) {
205 // Free the name for this value.
214 // NOTE: Could optimize for the case the name is shrinking to not deallocate
217 // Create the new name.
218 Name = ValueName::Create(NameRef);
219 Name->setValue(this);
223 // NOTE: Could optimize for the case the name is shrinking to not deallocate
227 ST->removeValueName(Name);
235 // Name is changing to something new.
236 Name = ST->createValueName(NameRef, this);
240 /// takeName - transfer the name from V to this value, setting V's name to
241 /// empty. It is an error to call V->takeName(V).
242 void Value::takeName(Value *V) {
243 assert(SubclassID != MDStringVal && "Cannot take the name of an MDString!");
245 ValueSymbolTable *ST = nullptr;
246 // If this value has a name, drop it.
248 // Get the symtab this is in.
249 if (getSymTab(this, ST)) {
250 // We can't set a name on this value, but we need to clear V's name if
252 if (V->hasName()) V->setName("");
253 return; // Cannot set a name on this value (e.g. constant).
258 ST->removeValueName(Name);
263 // Now we know that this has no name.
265 // If V has no name either, we're done.
266 if (!V->hasName()) return;
268 // Get this's symtab if we didn't before.
270 if (getSymTab(this, ST)) {
273 return; // Cannot set a name on this value (e.g. constant).
277 // Get V's ST, this should always succed, because V has a name.
278 ValueSymbolTable *VST;
279 bool Failure = getSymTab(V, VST);
280 assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
282 // If these values are both in the same symtab, we can do this very fast.
283 // This works even if both values have no symtab yet.
288 Name->setValue(this);
292 // Otherwise, things are slightly more complex. Remove V's name from VST and
293 // then reinsert it into ST.
296 VST->removeValueName(V->Name);
299 Name->setValue(this);
302 ST->reinsertValue(this);
306 static bool contains(SmallPtrSetImpl<ConstantExpr *> &Cache, ConstantExpr *Expr,
308 if (!Cache.insert(Expr))
311 for (auto &O : Expr->operands()) {
314 auto *CE = dyn_cast<ConstantExpr>(O);
317 if (contains(Cache, CE, C))
323 static bool contains(Value *Expr, Value *V) {
327 auto *C = dyn_cast<Constant>(V);
331 auto *CE = dyn_cast<ConstantExpr>(Expr);
335 SmallPtrSet<ConstantExpr *, 4> Cache;
336 return contains(Cache, CE, C);
340 void Value::replaceAllUsesWith(Value *New) {
341 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
342 assert(!contains(New, this) &&
343 "this->replaceAllUsesWith(expr(this)) is NOT valid!");
344 assert(New->getType() == getType() &&
345 "replaceAllUses of value with new value of different type!");
347 // Notify all ValueHandles (if present) that this value is going away.
349 ValueHandleBase::ValueIsRAUWd(this, New);
351 while (!use_empty()) {
353 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
354 // constant because they are uniqued.
355 if (auto *C = dyn_cast<Constant>(U.getUser())) {
356 if (!isa<GlobalValue>(C)) {
357 C->replaceUsesOfWithOnConstant(this, New, &U);
365 if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
366 BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
370 // Various metrics for how much to strip off of pointers.
371 enum PointerStripKind {
373 PSK_ZeroIndicesAndAliases,
374 PSK_InBoundsConstantIndices,
378 template <PointerStripKind StripKind>
379 static Value *stripPointerCastsAndOffsets(Value *V) {
380 if (!V->getType()->isPointerTy())
383 // Even though we don't look through PHI nodes, we could be called on an
384 // instruction in an unreachable block, which may be on a cycle.
385 SmallPtrSet<Value *, 4> Visited;
389 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
391 case PSK_ZeroIndicesAndAliases:
392 case PSK_ZeroIndices:
393 if (!GEP->hasAllZeroIndices())
396 case PSK_InBoundsConstantIndices:
397 if (!GEP->hasAllConstantIndices())
401 if (!GEP->isInBounds())
405 V = GEP->getPointerOperand();
406 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
407 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
408 V = cast<Operator>(V)->getOperand(0);
409 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
410 if (StripKind == PSK_ZeroIndices || GA->mayBeOverridden())
412 V = GA->getAliasee();
416 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
417 } while (Visited.insert(V));
423 Value *Value::stripPointerCasts() {
424 return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
427 Value *Value::stripPointerCastsNoFollowAliases() {
428 return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
431 Value *Value::stripInBoundsConstantOffsets() {
432 return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
435 Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
437 if (!getType()->isPointerTy())
440 assert(Offset.getBitWidth() == DL.getPointerSizeInBits(cast<PointerType>(
441 getType())->getAddressSpace()) &&
442 "The offset must have exactly as many bits as our pointer.");
444 // Even though we don't look through PHI nodes, we could be called on an
445 // instruction in an unreachable block, which may be on a cycle.
446 SmallPtrSet<Value *, 4> Visited;
447 Visited.insert(this);
450 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
451 if (!GEP->isInBounds())
453 APInt GEPOffset(Offset);
454 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
457 V = GEP->getPointerOperand();
458 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
459 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
460 V = cast<Operator>(V)->getOperand(0);
461 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
462 V = GA->getAliasee();
466 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
467 } while (Visited.insert(V));
472 Value *Value::stripInBoundsOffsets() {
473 return stripPointerCastsAndOffsets<PSK_InBounds>(this);
476 /// isDereferenceablePointer - Test if this value is always a pointer to
477 /// allocated and suitably aligned memory for a simple load or store.
478 static bool isDereferenceablePointer(const Value *V, const DataLayout *DL,
479 SmallPtrSetImpl<const Value *> &Visited) {
480 // Note that it is not safe to speculate into a malloc'd region because
481 // malloc may return null.
483 // These are obviously ok.
484 if (isa<AllocaInst>(V)) return true;
486 // It's not always safe to follow a bitcast, for example:
487 // bitcast i8* (alloca i8) to i32*
488 // would result in a 4-byte load from a 1-byte alloca. However,
489 // if we're casting from a pointer from a type of larger size
490 // to a type of smaller size (or the same size), and the alignment
491 // is at least as large as for the resulting pointer type, then
492 // we can look through the bitcast.
494 if (const BitCastInst* BC = dyn_cast<BitCastInst>(V)) {
495 Type *STy = BC->getSrcTy()->getPointerElementType(),
496 *DTy = BC->getDestTy()->getPointerElementType();
497 if (STy->isSized() && DTy->isSized() &&
498 (DL->getTypeStoreSize(STy) >=
499 DL->getTypeStoreSize(DTy)) &&
500 (DL->getABITypeAlignment(STy) >=
501 DL->getABITypeAlignment(DTy)))
502 return isDereferenceablePointer(BC->getOperand(0), DL, Visited);
505 // Global variables which can't collapse to null are ok.
506 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
507 return !GV->hasExternalWeakLinkage();
509 // byval arguments are okay. Arguments specifically marked as
510 // dereferenceable are okay too.
511 if (const Argument *A = dyn_cast<Argument>(V)) {
512 if (A->hasByValAttr())
514 else if (uint64_t Bytes = A->getDereferenceableBytes()) {
515 Type *Ty = V->getType()->getPointerElementType();
516 if (Ty->isSized() && DL && DL->getTypeStoreSize(Ty) <= Bytes)
523 // Return values from call sites specifically marked as dereferenceable are
525 if (ImmutableCallSite CS = V) {
526 if (uint64_t Bytes = CS.getDereferenceableBytes(0)) {
527 Type *Ty = V->getType()->getPointerElementType();
528 if (Ty->isSized() && DL && DL->getTypeStoreSize(Ty) <= Bytes)
533 // For GEPs, determine if the indexing lands within the allocated object.
534 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
535 // Conservatively require that the base pointer be fully dereferenceable.
536 if (!Visited.insert(GEP->getOperand(0)))
538 if (!isDereferenceablePointer(GEP->getOperand(0), DL, Visited))
540 // Check the indices.
541 gep_type_iterator GTI = gep_type_begin(GEP);
542 for (User::const_op_iterator I = GEP->op_begin()+1,
543 E = GEP->op_end(); I != E; ++I) {
546 // Struct indices can't be out of bounds.
547 if (isa<StructType>(Ty))
549 ConstantInt *CI = dyn_cast<ConstantInt>(Index);
552 // Zero is always ok.
555 // Check to see that it's within the bounds of an array.
556 ArrayType *ATy = dyn_cast<ArrayType>(Ty);
559 if (CI->getValue().getActiveBits() > 64)
561 if (CI->getZExtValue() >= ATy->getNumElements())
564 // Indices check out; this is dereferenceable.
568 if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
569 return isDereferenceablePointer(ASC->getOperand(0), DL, Visited);
571 // If we don't know, assume the worst.
575 /// isDereferenceablePointer - Test if this value is always a pointer to
576 /// allocated and suitably aligned memory for a simple load or store.
577 bool Value::isDereferenceablePointer(const DataLayout *DL) const {
578 // When dereferenceability information is provided by a dereferenceable
579 // attribute, we know exactly how many bytes are dereferenceable. If we can
580 // determine the exact offset to the attributed variable, we can use that
582 Type *Ty = getType()->getPointerElementType();
583 if (Ty->isSized() && DL) {
584 APInt Offset(DL->getTypeStoreSizeInBits(getType()), 0);
585 const Value *BV = stripAndAccumulateInBoundsConstantOffsets(*DL, Offset);
587 APInt DerefBytes(Offset.getBitWidth(), 0);
588 if (const Argument *A = dyn_cast<Argument>(BV))
589 DerefBytes = A->getDereferenceableBytes();
590 else if (ImmutableCallSite CS = BV)
591 DerefBytes = CS.getDereferenceableBytes(0);
593 if (DerefBytes.getBoolValue() && Offset.isNonNegative()) {
594 if (DerefBytes.uge(Offset + DL->getTypeStoreSize(Ty)))
599 SmallPtrSet<const Value *, 32> Visited;
600 return ::isDereferenceablePointer(this, DL, Visited);
603 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
604 /// return the value in the PHI node corresponding to PredBB. If not, return
605 /// ourself. This is useful if you want to know the value something has in a
606 /// predecessor block.
607 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
608 const BasicBlock *PredBB) {
609 PHINode *PN = dyn_cast<PHINode>(this);
610 if (PN && PN->getParent() == CurBB)
611 return PN->getIncomingValueForBlock(PredBB);
615 LLVMContext &Value::getContext() const { return VTy->getContext(); }
617 void Value::reverseUseList() {
618 if (!UseList || !UseList->Next)
619 // No need to reverse 0 or 1 uses.
623 Use *Current = UseList->Next;
624 Head->Next = nullptr;
626 Use *Next = Current->Next;
627 Current->Next = Head;
628 Head->setPrev(&Current->Next);
633 Head->setPrev(&UseList);
636 //===----------------------------------------------------------------------===//
637 // ValueHandleBase Class
638 //===----------------------------------------------------------------------===//
640 /// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
641 /// List is known to point into the existing use list.
642 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
643 assert(List && "Handle list is null?");
645 // Splice ourselves into the list.
650 Next->setPrevPtr(&Next);
651 assert(VP.getPointer() == Next->VP.getPointer() && "Added to wrong list?");
655 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
656 assert(List && "Must insert after existing node");
659 setPrevPtr(&List->Next);
662 Next->setPrevPtr(&Next);
665 /// AddToUseList - Add this ValueHandle to the use list for VP.
666 void ValueHandleBase::AddToUseList() {
667 assert(VP.getPointer() && "Null pointer doesn't have a use list!");
669 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
671 if (VP.getPointer()->HasValueHandle) {
672 // If this value already has a ValueHandle, then it must be in the
673 // ValueHandles map already.
674 ValueHandleBase *&Entry = pImpl->ValueHandles[VP.getPointer()];
675 assert(Entry && "Value doesn't have any handles?");
676 AddToExistingUseList(&Entry);
680 // Ok, it doesn't have any handles yet, so we must insert it into the
681 // DenseMap. However, doing this insertion could cause the DenseMap to
682 // reallocate itself, which would invalidate all of the PrevP pointers that
683 // point into the old table. Handle this by checking for reallocation and
684 // updating the stale pointers only if needed.
685 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
686 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
688 ValueHandleBase *&Entry = Handles[VP.getPointer()];
689 assert(!Entry && "Value really did already have handles?");
690 AddToExistingUseList(&Entry);
691 VP.getPointer()->HasValueHandle = true;
693 // If reallocation didn't happen or if this was the first insertion, don't
695 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
696 Handles.size() == 1) {
700 // Okay, reallocation did happen. Fix the Prev Pointers.
701 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
702 E = Handles.end(); I != E; ++I) {
703 assert(I->second && I->first == I->second->VP.getPointer() &&
704 "List invariant broken!");
705 I->second->setPrevPtr(&I->second);
709 /// RemoveFromUseList - Remove this ValueHandle from its current use list.
710 void ValueHandleBase::RemoveFromUseList() {
711 assert(VP.getPointer() && VP.getPointer()->HasValueHandle &&
712 "Pointer doesn't have a use list!");
714 // Unlink this from its use list.
715 ValueHandleBase **PrevPtr = getPrevPtr();
716 assert(*PrevPtr == this && "List invariant broken");
720 assert(Next->getPrevPtr() == &Next && "List invariant broken");
721 Next->setPrevPtr(PrevPtr);
725 // If the Next pointer was null, then it is possible that this was the last
726 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
728 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
729 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
730 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
731 Handles.erase(VP.getPointer());
732 VP.getPointer()->HasValueHandle = false;
737 void ValueHandleBase::ValueIsDeleted(Value *V) {
738 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
740 // Get the linked list base, which is guaranteed to exist since the
741 // HasValueHandle flag is set.
742 LLVMContextImpl *pImpl = V->getContext().pImpl;
743 ValueHandleBase *Entry = pImpl->ValueHandles[V];
744 assert(Entry && "Value bit set but no entries exist");
746 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
747 // and remove themselves from the list without breaking our iteration. This
748 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
749 // Note that we deliberately do not the support the case when dropping a value
750 // handle results in a new value handle being permanently added to the list
751 // (as might occur in theory for CallbackVH's): the new value handle will not
752 // be processed and the checking code will mete out righteous punishment if
753 // the handle is still present once we have finished processing all the other
754 // value handles (it is fine to momentarily add then remove a value handle).
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()) {
764 // Mark that this value has been deleted by setting it to an invalid Value
766 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
769 // Weak just goes to null, which will unlink it from the list.
770 Entry->operator=(nullptr);
773 // Forward to the subclass's implementation.
774 static_cast<CallbackVH*>(Entry)->deleted();
779 // All callbacks, weak references, and assertingVHs should be dropped by now.
780 if (V->HasValueHandle) {
781 #ifndef NDEBUG // Only in +Asserts mode...
782 dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
784 if (pImpl->ValueHandles[V]->getKind() == Assert)
785 llvm_unreachable("An asserting value handle still pointed to this"
789 llvm_unreachable("All references to V were not removed?");
794 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
795 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
796 assert(Old != New && "Changing value into itself!");
798 // Get the linked list base, which is guaranteed to exist since the
799 // HasValueHandle flag is set.
800 LLVMContextImpl *pImpl = Old->getContext().pImpl;
801 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
803 assert(Entry && "Value bit set but no entries exist");
805 // We use a local ValueHandleBase as an iterator so that
806 // ValueHandles can add and remove themselves from the list without
807 // breaking our iteration. This is not really an AssertingVH; we
808 // just have to give ValueHandleBase some kind.
809 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
810 Iterator.RemoveFromUseList();
811 Iterator.AddToExistingUseListAfter(Entry);
812 assert(Entry->Next == &Iterator && "Loop invariant broken.");
814 switch (Entry->getKind()) {
816 // Asserting handle does not follow RAUW implicitly.
819 // Tracking goes to new value like a WeakVH. Note that this may make it
820 // something incompatible with its templated type. We don't want to have a
821 // virtual (or inline) interface to handle this though, so instead we make
822 // the TrackingVH accessors guarantee that a client never sees this value.
826 // Weak goes to the new value, which will unlink it from Old's list.
827 Entry->operator=(New);
830 // Forward to the subclass's implementation.
831 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
837 // If any new tracking or weak value handles were added while processing the
838 // list, then complain about it now.
839 if (Old->HasValueHandle)
840 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
841 switch (Entry->getKind()) {
844 dbgs() << "After RAUW from " << *Old->getType() << " %"
845 << Old->getName() << " to " << *New->getType() << " %"
846 << New->getName() << "\n";
847 llvm_unreachable("A tracking or weak value handle still pointed to the"
855 // Pin the vtable to this file.
856 void CallbackVH::anchor() {}