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/IntrinsicInst.h"
27 #include "llvm/IR/Module.h"
28 #include "llvm/IR/Operator.h"
29 #include "llvm/IR/Statepoint.h"
30 #include "llvm/IR/ValueHandle.h"
31 #include "llvm/IR/ValueSymbolTable.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/ManagedStatic.h"
35 #include "llvm/Support/raw_ostream.h"
40 //===----------------------------------------------------------------------===//
42 //===----------------------------------------------------------------------===//
43 static inline Type *checkType(Type *Ty) {
44 assert(Ty && "Value defined with a null type: Error!");
48 Value::Value(Type *ty, unsigned scid)
49 : VTy(checkType(ty)), UseList(nullptr), SubclassID(scid),
50 HasValueHandle(0), SubclassOptionalData(0), SubclassData(0),
51 NumUserOperands(0), IsUsedByMD(false), HasName(false) {
52 // FIXME: Why isn't this in the subclass gunk??
53 // Note, we cannot call isa<CallInst> before the CallInst has been
55 if (SubclassID == Instruction::Call || SubclassID == Instruction::Invoke)
56 assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) &&
57 "invalid CallInst type!");
58 else if (SubclassID != BasicBlockVal &&
59 (SubclassID < ConstantFirstVal || SubclassID > ConstantLastVal))
60 assert((VTy->isFirstClassType() || VTy->isVoidTy()) &&
61 "Cannot create non-first-class values except for constants!");
62 static_assert(sizeof(Value) == 3 * sizeof(void *) + 2 * sizeof(unsigned),
67 // Notify all ValueHandles (if present) that this value is going away.
69 ValueHandleBase::ValueIsDeleted(this);
70 if (isUsedByMetadata())
71 ValueAsMetadata::handleDeletion(this);
73 #ifndef NDEBUG // Only in -g mode...
74 // Check to make sure that there are no uses of this value that are still
75 // around when the value is destroyed. If there are, then we have a dangling
76 // reference and something is wrong. This code is here to print out where
77 // the value is still being referenced.
80 dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n";
81 for (auto *U : users())
82 dbgs() << "Use still stuck around after Def is destroyed:" << *U << "\n";
85 assert(use_empty() && "Uses remain when a value is destroyed!");
87 // If this value is named, destroy the name. This should not be in a symtab
92 void Value::destroyValueName() {
93 ValueName *Name = getValueName();
96 setValueName(nullptr);
99 bool Value::hasNUses(unsigned N) const {
100 const_use_iterator UI = use_begin(), E = use_end();
103 if (UI == E) return false; // Too few.
107 bool Value::hasNUsesOrMore(unsigned N) const {
108 const_use_iterator UI = use_begin(), E = use_end();
111 if (UI == E) return false; // Too few.
116 bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
117 // This can be computed either by scanning the instructions in BB, or by
118 // scanning the use list of this Value. Both lists can be very long, but
119 // usually one is quite short.
121 // Scan both lists simultaneously until one is exhausted. This limits the
122 // search to the shorter list.
123 BasicBlock::const_iterator BI = BB->begin(), BE = BB->end();
124 const_user_iterator UI = user_begin(), UE = user_end();
125 for (; BI != BE && UI != UE; ++BI, ++UI) {
126 // Scan basic block: Check if this Value is used by the instruction at BI.
127 if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end())
129 // Scan use list: Check if the use at UI is in BB.
130 const Instruction *User = dyn_cast<Instruction>(*UI);
131 if (User && User->getParent() == BB)
137 unsigned Value::getNumUses() const {
138 return (unsigned)std::distance(use_begin(), use_end());
141 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
143 if (Instruction *I = dyn_cast<Instruction>(V)) {
144 if (BasicBlock *P = I->getParent())
145 if (Function *PP = P->getParent())
146 ST = &PP->getValueSymbolTable();
147 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
148 if (Function *P = BB->getParent())
149 ST = &P->getValueSymbolTable();
150 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
151 if (Module *P = GV->getParent())
152 ST = &P->getValueSymbolTable();
153 } else if (Argument *A = dyn_cast<Argument>(V)) {
154 if (Function *P = A->getParent())
155 ST = &P->getValueSymbolTable();
157 assert(isa<Constant>(V) && "Unknown value type!");
158 return true; // no name is setable for this.
163 ValueName *Value::getValueName() const {
164 if (!HasName) return nullptr;
166 LLVMContext &Ctx = getContext();
167 auto I = Ctx.pImpl->ValueNames.find(this);
168 assert(I != Ctx.pImpl->ValueNames.end() &&
169 "No name entry found!");
174 void Value::setValueName(ValueName *VN) {
175 LLVMContext &Ctx = getContext();
177 assert(HasName == Ctx.pImpl->ValueNames.count(this) &&
178 "HasName bit out of sync!");
182 Ctx.pImpl->ValueNames.erase(this);
188 Ctx.pImpl->ValueNames[this] = VN;
191 StringRef Value::getName() const {
192 // Make sure the empty string is still a C string. For historical reasons,
193 // some clients want to call .data() on the result and expect it to be null
196 return StringRef("", 0);
197 return getValueName()->getKey();
200 void Value::setNameImpl(const Twine &NewName) {
201 // Fast-path: LLVMContext can be set to strip out non-GlobalValue names
202 if (getContext().shouldDiscardValueNames() && !isa<GlobalValue>(this))
205 // Fast path for common IRBuilder case of setName("") when there is no name.
206 if (NewName.isTriviallyEmpty() && !hasName())
209 SmallString<256> NameData;
210 StringRef NameRef = NewName.toStringRef(NameData);
211 assert(NameRef.find_first_of(0) == StringRef::npos &&
212 "Null bytes are not allowed in names");
214 // Name isn't changing?
215 if (getName() == NameRef)
218 assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
220 // Get the symbol table to update for this object.
221 ValueSymbolTable *ST;
222 if (getSymTab(this, ST))
223 return; // Cannot set a name on this value (e.g. constant).
225 if (!ST) { // No symbol table to update? Just do the change.
226 if (NameRef.empty()) {
227 // Free the name for this value.
232 // NOTE: Could optimize for the case the name is shrinking to not deallocate
236 // Create the new name.
237 setValueName(ValueName::Create(NameRef));
238 getValueName()->setValue(this);
242 // NOTE: Could optimize for the case the name is shrinking to not deallocate
246 ST->removeValueName(getValueName());
253 // Name is changing to something new.
254 setValueName(ST->createValueName(NameRef, this));
257 void Value::setName(const Twine &NewName) {
258 setNameImpl(NewName);
259 if (Function *F = dyn_cast<Function>(this))
260 F->recalculateIntrinsicID();
263 void Value::takeName(Value *V) {
264 ValueSymbolTable *ST = nullptr;
265 // If this value has a name, drop it.
267 // Get the symtab this is in.
268 if (getSymTab(this, ST)) {
269 // We can't set a name on this value, but we need to clear V's name if
271 if (V->hasName()) V->setName("");
272 return; // Cannot set a name on this value (e.g. constant).
277 ST->removeValueName(getValueName());
281 // Now we know that this has no name.
283 // If V has no name either, we're done.
284 if (!V->hasName()) return;
286 // Get this's symtab if we didn't before.
288 if (getSymTab(this, ST)) {
291 return; // Cannot set a name on this value (e.g. constant).
295 // Get V's ST, this should always succed, because V has a name.
296 ValueSymbolTable *VST;
297 bool Failure = getSymTab(V, VST);
298 assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
300 // If these values are both in the same symtab, we can do this very fast.
301 // This works even if both values have no symtab yet.
304 setValueName(V->getValueName());
305 V->setValueName(nullptr);
306 getValueName()->setValue(this);
310 // Otherwise, things are slightly more complex. Remove V's name from VST and
311 // then reinsert it into ST.
314 VST->removeValueName(V->getValueName());
315 setValueName(V->getValueName());
316 V->setValueName(nullptr);
317 getValueName()->setValue(this);
320 ST->reinsertValue(this);
323 void Value::assertModuleIsMaterialized() const {
325 const GlobalValue *GV = dyn_cast<GlobalValue>(this);
328 const Module *M = GV->getParent();
331 assert(M->isMaterialized());
336 static bool contains(SmallPtrSetImpl<ConstantExpr *> &Cache, ConstantExpr *Expr,
338 if (!Cache.insert(Expr).second)
341 for (auto &O : Expr->operands()) {
344 auto *CE = dyn_cast<ConstantExpr>(O);
347 if (contains(Cache, CE, C))
353 static bool contains(Value *Expr, Value *V) {
357 auto *C = dyn_cast<Constant>(V);
361 auto *CE = dyn_cast<ConstantExpr>(Expr);
365 SmallPtrSet<ConstantExpr *, 4> Cache;
366 return contains(Cache, CE, C);
370 void Value::replaceAllUsesWith(Value *New) {
371 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
372 assert(!contains(New, this) &&
373 "this->replaceAllUsesWith(expr(this)) is NOT valid!");
374 assert(New->getType() == getType() &&
375 "replaceAllUses of value with new value of different type!");
377 // Notify all ValueHandles (if present) that this value is going away.
379 ValueHandleBase::ValueIsRAUWd(this, New);
380 if (isUsedByMetadata())
381 ValueAsMetadata::handleRAUW(this, New);
383 while (!use_empty()) {
385 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
386 // constant because they are uniqued.
387 if (auto *C = dyn_cast<Constant>(U.getUser())) {
388 if (!isa<GlobalValue>(C)) {
389 C->handleOperandChange(this, New);
397 if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
398 BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
401 // Like replaceAllUsesWith except it does not handle constants or basic blocks.
402 // This routine leaves uses within BB.
403 void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) {
404 assert(New && "Value::replaceUsesOutsideBlock(<null>, BB) is invalid!");
405 assert(!contains(New, this) &&
406 "this->replaceUsesOutsideBlock(expr(this), BB) is NOT valid!");
407 assert(New->getType() == getType() &&
408 "replaceUses of value with new value of different type!");
409 assert(BB && "Basic block that may contain a use of 'New' must be defined\n");
411 use_iterator UI = use_begin(), E = use_end();
415 auto *Usr = dyn_cast<Instruction>(U.getUser());
416 if (Usr && Usr->getParent() == BB)
423 // Various metrics for how much to strip off of pointers.
424 enum PointerStripKind {
426 PSK_ZeroIndicesAndAliases,
427 PSK_InBoundsConstantIndices,
431 template <PointerStripKind StripKind>
432 static Value *stripPointerCastsAndOffsets(Value *V) {
433 if (!V->getType()->isPointerTy())
436 // Even though we don't look through PHI nodes, we could be called on an
437 // instruction in an unreachable block, which may be on a cycle.
438 SmallPtrSet<Value *, 4> Visited;
442 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
444 case PSK_ZeroIndicesAndAliases:
445 case PSK_ZeroIndices:
446 if (!GEP->hasAllZeroIndices())
449 case PSK_InBoundsConstantIndices:
450 if (!GEP->hasAllConstantIndices())
454 if (!GEP->isInBounds())
458 V = GEP->getPointerOperand();
459 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
460 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
461 V = cast<Operator>(V)->getOperand(0);
462 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
463 if (StripKind == PSK_ZeroIndices || GA->isInterposable())
465 V = GA->getAliasee();
467 if (auto CS = CallSite(V))
468 if (Value *RV = CS.getReturnedArgOperand()) {
475 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
476 } while (Visited.insert(V).second);
480 } // end anonymous namespace
482 Value *Value::stripPointerCasts() {
483 return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
486 Value *Value::stripPointerCastsNoFollowAliases() {
487 return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
490 Value *Value::stripInBoundsConstantOffsets() {
491 return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
494 Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
496 if (!getType()->isPointerTy())
499 assert(Offset.getBitWidth() == DL.getPointerSizeInBits(cast<PointerType>(
500 getType())->getAddressSpace()) &&
501 "The offset must have exactly as many bits as our pointer.");
503 // Even though we don't look through PHI nodes, we could be called on an
504 // instruction in an unreachable block, which may be on a cycle.
505 SmallPtrSet<Value *, 4> Visited;
506 Visited.insert(this);
509 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
510 if (!GEP->isInBounds())
512 APInt GEPOffset(Offset);
513 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
516 V = GEP->getPointerOperand();
517 } else if (Operator::getOpcode(V) == Instruction::BitCast) {
518 V = cast<Operator>(V)->getOperand(0);
519 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
520 V = GA->getAliasee();
522 if (auto CS = CallSite(V))
523 if (Value *RV = CS.getReturnedArgOperand()) {
530 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
531 } while (Visited.insert(V).second);
536 Value *Value::stripInBoundsOffsets() {
537 return stripPointerCastsAndOffsets<PSK_InBounds>(this);
540 unsigned Value::getPointerDereferenceableBytes(const DataLayout &DL,
541 bool &CanBeNull) const {
542 assert(getType()->isPointerTy() && "must be pointer");
544 unsigned DerefBytes = 0;
546 if (const Argument *A = dyn_cast<Argument>(this)) {
547 DerefBytes = A->getDereferenceableBytes();
548 if (DerefBytes == 0 && A->hasByValAttr() && A->getType()->isSized()) {
549 DerefBytes = DL.getTypeStoreSize(A->getType());
552 if (DerefBytes == 0) {
553 DerefBytes = A->getDereferenceableOrNullBytes();
556 } else if (auto CS = ImmutableCallSite(this)) {
557 DerefBytes = CS.getDereferenceableBytes(0);
558 if (DerefBytes == 0) {
559 DerefBytes = CS.getDereferenceableOrNullBytes(0);
562 } else if (const LoadInst *LI = dyn_cast<LoadInst>(this)) {
563 if (MDNode *MD = LI->getMetadata(LLVMContext::MD_dereferenceable)) {
564 ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
565 DerefBytes = CI->getLimitedValue();
567 if (DerefBytes == 0) {
569 LI->getMetadata(LLVMContext::MD_dereferenceable_or_null)) {
570 ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
571 DerefBytes = CI->getLimitedValue();
575 } else if (auto *AI = dyn_cast<AllocaInst>(this)) {
576 if (AI->getAllocatedType()->isSized()) {
577 DerefBytes = DL.getTypeStoreSize(AI->getAllocatedType());
580 } else if (auto *GV = dyn_cast<GlobalVariable>(this)) {
581 if (GV->getValueType()->isSized() && !GV->hasExternalWeakLinkage()) {
582 // TODO: Don't outright reject hasExternalWeakLinkage but set the
584 DerefBytes = DL.getTypeStoreSize(GV->getValueType());
591 unsigned Value::getPointerAlignment(const DataLayout &DL) const {
592 assert(getType()->isPointerTy() && "must be pointer");
595 if (auto *GO = dyn_cast<GlobalObject>(this)) {
596 Align = GO->getAlignment();
598 if (auto *GVar = dyn_cast<GlobalVariable>(GO)) {
599 Type *ObjectType = GVar->getValueType();
600 if (ObjectType->isSized()) {
601 // If the object is defined in the current Module, we'll be giving
602 // it the preferred alignment. Otherwise, we have to assume that it
603 // may only have the minimum ABI alignment.
604 if (GVar->isStrongDefinitionForLinker())
605 Align = DL.getPreferredAlignment(GVar);
607 Align = DL.getABITypeAlignment(ObjectType);
611 } else if (const Argument *A = dyn_cast<Argument>(this)) {
612 Align = A->getParamAlignment();
614 if (!Align && A->hasStructRetAttr()) {
615 // An sret parameter has at least the ABI alignment of the return type.
616 Type *EltTy = cast<PointerType>(A->getType())->getElementType();
617 if (EltTy->isSized())
618 Align = DL.getABITypeAlignment(EltTy);
620 } else if (const AllocaInst *AI = dyn_cast<AllocaInst>(this)) {
621 Align = AI->getAlignment();
623 Type *AllocatedType = AI->getAllocatedType();
624 if (AllocatedType->isSized())
625 Align = DL.getPrefTypeAlignment(AllocatedType);
627 } else if (auto CS = ImmutableCallSite(this))
628 Align = CS.getAttributes().getParamAlignment(AttributeSet::ReturnIndex);
629 else if (const LoadInst *LI = dyn_cast<LoadInst>(this))
630 if (MDNode *MD = LI->getMetadata(LLVMContext::MD_align)) {
631 ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
632 Align = CI->getLimitedValue();
638 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
639 const BasicBlock *PredBB) {
640 PHINode *PN = dyn_cast<PHINode>(this);
641 if (PN && PN->getParent() == CurBB)
642 return PN->getIncomingValueForBlock(PredBB);
646 LLVMContext &Value::getContext() const { return VTy->getContext(); }
648 void Value::reverseUseList() {
649 if (!UseList || !UseList->Next)
650 // No need to reverse 0 or 1 uses.
654 Use *Current = UseList->Next;
655 Head->Next = nullptr;
657 Use *Next = Current->Next;
658 Current->Next = Head;
659 Head->setPrev(&Current->Next);
664 Head->setPrev(&UseList);
667 //===----------------------------------------------------------------------===//
668 // ValueHandleBase Class
669 //===----------------------------------------------------------------------===//
671 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
672 assert(List && "Handle list is null?");
674 // Splice ourselves into the list.
679 Next->setPrevPtr(&Next);
680 assert(V == Next->V && "Added to wrong list?");
684 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
685 assert(List && "Must insert after existing node");
688 setPrevPtr(&List->Next);
691 Next->setPrevPtr(&Next);
694 void ValueHandleBase::AddToUseList() {
695 assert(V && "Null pointer doesn't have a use list!");
697 LLVMContextImpl *pImpl = V->getContext().pImpl;
699 if (V->HasValueHandle) {
700 // If this value already has a ValueHandle, then it must be in the
701 // ValueHandles map already.
702 ValueHandleBase *&Entry = pImpl->ValueHandles[V];
703 assert(Entry && "Value doesn't have any handles?");
704 AddToExistingUseList(&Entry);
708 // Ok, it doesn't have any handles yet, so we must insert it into the
709 // DenseMap. However, doing this insertion could cause the DenseMap to
710 // reallocate itself, which would invalidate all of the PrevP pointers that
711 // point into the old table. Handle this by checking for reallocation and
712 // updating the stale pointers only if needed.
713 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
714 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
716 ValueHandleBase *&Entry = Handles[V];
717 assert(!Entry && "Value really did already have handles?");
718 AddToExistingUseList(&Entry);
719 V->HasValueHandle = true;
721 // If reallocation didn't happen or if this was the first insertion, don't
723 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
724 Handles.size() == 1) {
728 // Okay, reallocation did happen. Fix the Prev Pointers.
729 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
730 E = Handles.end(); I != E; ++I) {
731 assert(I->second && I->first == I->second->V &&
732 "List invariant broken!");
733 I->second->setPrevPtr(&I->second);
737 void ValueHandleBase::RemoveFromUseList() {
738 assert(V && V->HasValueHandle &&
739 "Pointer doesn't have a use list!");
741 // Unlink this from its use list.
742 ValueHandleBase **PrevPtr = getPrevPtr();
743 assert(*PrevPtr == this && "List invariant broken");
747 assert(Next->getPrevPtr() == &Next && "List invariant broken");
748 Next->setPrevPtr(PrevPtr);
752 // If the Next pointer was null, then it is possible that this was the last
753 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
755 LLVMContextImpl *pImpl = V->getContext().pImpl;
756 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
757 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
759 V->HasValueHandle = false;
763 void ValueHandleBase::ValueIsDeleted(Value *V) {
764 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
766 // Get the linked list base, which is guaranteed to exist since the
767 // HasValueHandle flag is set.
768 LLVMContextImpl *pImpl = V->getContext().pImpl;
769 ValueHandleBase *Entry = pImpl->ValueHandles[V];
770 assert(Entry && "Value bit set but no entries exist");
772 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
773 // and remove themselves from the list without breaking our iteration. This
774 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
775 // Note that we deliberately do not the support the case when dropping a value
776 // handle results in a new value handle being permanently added to the list
777 // (as might occur in theory for CallbackVH's): the new value handle will not
778 // be processed and the checking code will mete out righteous punishment if
779 // the handle is still present once we have finished processing all the other
780 // value handles (it is fine to momentarily add then remove a value handle).
781 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
782 Iterator.RemoveFromUseList();
783 Iterator.AddToExistingUseListAfter(Entry);
784 assert(Entry->Next == &Iterator && "Loop invariant broken.");
786 switch (Entry->getKind()) {
790 // Mark that this value has been deleted by setting it to an invalid Value
792 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
795 // Weak just goes to null, which will unlink it from the list.
796 Entry->operator=(nullptr);
799 // Forward to the subclass's implementation.
800 static_cast<CallbackVH*>(Entry)->deleted();
805 // All callbacks, weak references, and assertingVHs should be dropped by now.
806 if (V->HasValueHandle) {
807 #ifndef NDEBUG // Only in +Asserts mode...
808 dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
810 if (pImpl->ValueHandles[V]->getKind() == Assert)
811 llvm_unreachable("An asserting value handle still pointed to this"
815 llvm_unreachable("All references to V were not removed?");
819 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
820 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
821 assert(Old != New && "Changing value into itself!");
822 assert(Old->getType() == New->getType() &&
823 "replaceAllUses of value with new value of different type!");
825 // Get the linked list base, which is guaranteed to exist since the
826 // HasValueHandle flag is set.
827 LLVMContextImpl *pImpl = Old->getContext().pImpl;
828 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
830 assert(Entry && "Value bit set but no entries exist");
832 // We use a local ValueHandleBase as an iterator so that
833 // ValueHandles can add and remove themselves from the list without
834 // breaking our iteration. This is not really an AssertingVH; we
835 // just have to give ValueHandleBase some kind.
836 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
837 Iterator.RemoveFromUseList();
838 Iterator.AddToExistingUseListAfter(Entry);
839 assert(Entry->Next == &Iterator && "Loop invariant broken.");
841 switch (Entry->getKind()) {
843 // Asserting handle does not follow RAUW implicitly.
846 // Tracking goes to new value like a WeakVH. Note that this may make it
847 // something incompatible with its templated type. We don't want to have a
848 // virtual (or inline) interface to handle this though, so instead we make
849 // the TrackingVH accessors guarantee that a client never sees this value.
853 // Weak goes to the new value, which will unlink it from Old's list.
854 Entry->operator=(New);
857 // Forward to the subclass's implementation.
858 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
864 // If any new tracking or weak value handles were added while processing the
865 // list, then complain about it now.
866 if (Old->HasValueHandle)
867 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
868 switch (Entry->getKind()) {
871 dbgs() << "After RAUW from " << *Old->getType() << " %"
872 << Old->getName() << " to " << *New->getType() << " %"
873 << New->getName() << "\n";
874 llvm_unreachable("A tracking or weak value handle still pointed to the"
882 // Pin the vtable to this file.
883 void CallbackVH::anchor() {}