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/Module.h"
27 #include "llvm/IR/Operator.h"
28 #include "llvm/IR/ValueHandle.h"
29 #include "llvm/IR/ValueSymbolTable.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/ErrorHandling.h"
32 #include "llvm/Support/ManagedStatic.h"
36 //===----------------------------------------------------------------------===//
38 //===----------------------------------------------------------------------===//
40 static inline Type *checkType(Type *Ty) {
41 assert(Ty && "Value defined with a null type: Error!");
45 Value::Value(Type *ty, unsigned scid)
46 : VTy(checkType(ty)), UseList(nullptr), SubclassID(scid), HasValueHandle(0),
47 SubclassOptionalData(0), SubclassData(0), NumOperands(0) {
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);
64 if (isUsedByMetadata())
65 ValueAsMetadata::handleDeletion(this);
67 #ifndef NDEBUG // Only in -g mode...
68 // Check to make sure that there are no uses of this value that are still
69 // around when the value is destroyed. If there are, then we have a dangling
70 // reference and something is wrong. This code is here to print out what is
71 // still being referenced. The value in question should be printed as
75 dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n";
76 for (use_iterator I = use_begin(), E = use_end(); I != E; ++I)
77 dbgs() << "Use still stuck around after Def is destroyed:"
81 assert(use_empty() && "Uses remain when a value is destroyed!");
83 // If this value is named, destroy the name. This should not be in a symtab
88 void Value::destroyValueName() {
89 ValueName *Name = getValueName();
92 setValueName(nullptr);
95 bool Value::hasNUses(unsigned N) const {
96 const_use_iterator UI = use_begin(), E = use_end();
99 if (UI == E) return false; // Too few.
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 bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
113 // This can be computed either by scanning the instructions in BB, or by
114 // scanning the use list of this Value. Both lists can be very long, but
115 // usually one is quite short.
117 // Scan both lists simultaneously until one is exhausted. This limits the
118 // search to the shorter list.
119 BasicBlock::const_iterator BI = BB->begin(), BE = BB->end();
120 const_user_iterator UI = user_begin(), UE = user_end();
121 for (; BI != BE && UI != UE; ++BI, ++UI) {
122 // Scan basic block: Check if this Value is used by the instruction at BI.
123 if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end())
125 // Scan use list: Check if the use at UI is in BB.
126 const Instruction *User = dyn_cast<Instruction>(*UI);
127 if (User && User->getParent() == BB)
133 unsigned Value::getNumUses() const {
134 return (unsigned)std::distance(use_begin(), use_end());
137 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
139 if (Instruction *I = dyn_cast<Instruction>(V)) {
140 if (BasicBlock *P = I->getParent())
141 if (Function *PP = P->getParent())
142 ST = &PP->getValueSymbolTable();
143 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
144 if (Function *P = BB->getParent())
145 ST = &P->getValueSymbolTable();
146 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
147 if (Module *P = GV->getParent())
148 ST = &P->getValueSymbolTable();
149 } else if (Argument *A = dyn_cast<Argument>(V)) {
150 if (Function *P = A->getParent())
151 ST = &P->getValueSymbolTable();
153 assert(isa<Constant>(V) && "Unknown value type!");
154 return true; // no name is setable for this.
159 StringRef Value::getName() const {
160 // Make sure the empty string is still a C string. For historical reasons,
161 // some clients want to call .data() on the result and expect it to be null
164 return StringRef("", 0);
165 return getValueName()->getKey();
168 void Value::setName(const Twine &NewName) {
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.
199 // NOTE: Could optimize for the case the name is shrinking to not deallocate
203 // Create the new name.
204 setValueName(ValueName::Create(NameRef));
205 getValueName()->setValue(this);
209 // NOTE: Could optimize for the case the name is shrinking to not deallocate
213 ST->removeValueName(getValueName());
220 // Name is changing to something new.
221 setValueName(ST->createValueName(NameRef, this));
224 void Value::takeName(Value *V) {
225 ValueSymbolTable *ST = nullptr;
226 // If this value has a name, drop it.
228 // Get the symtab this is in.
229 if (getSymTab(this, ST)) {
230 // We can't set a name on this value, but we need to clear V's name if
232 if (V->hasName()) V->setName("");
233 return; // Cannot set a name on this value (e.g. constant).
238 ST->removeValueName(getValueName());
242 // Now we know that this has no name.
244 // If V has no name either, we're done.
245 if (!V->hasName()) return;
247 // Get this's symtab if we didn't before.
249 if (getSymTab(this, ST)) {
252 return; // Cannot set a name on this value (e.g. constant).
256 // Get V's ST, this should always succed, because V has a name.
257 ValueSymbolTable *VST;
258 bool Failure = getSymTab(V, VST);
259 assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
261 // If these values are both in the same symtab, we can do this very fast.
262 // This works even if both values have no symtab yet.
265 setValueName(V->getValueName());
266 V->setValueName(nullptr);
267 getValueName()->setValue(this);
271 // Otherwise, things are slightly more complex. Remove V's name from VST and
272 // then reinsert it into ST.
275 VST->removeValueName(V->getValueName());
276 setValueName(V->getValueName());
277 V->setValueName(nullptr);
278 getValueName()->setValue(this);
281 ST->reinsertValue(this);
285 static bool contains(SmallPtrSetImpl<ConstantExpr *> &Cache, ConstantExpr *Expr,
287 if (!Cache.insert(Expr).second)
290 for (auto &O : Expr->operands()) {
293 auto *CE = dyn_cast<ConstantExpr>(O);
296 if (contains(Cache, CE, C))
302 static bool contains(Value *Expr, Value *V) {
306 auto *C = dyn_cast<Constant>(V);
310 auto *CE = dyn_cast<ConstantExpr>(Expr);
314 SmallPtrSet<ConstantExpr *, 4> Cache;
315 return contains(Cache, CE, C);
319 void Value::replaceAllUsesWith(Value *New) {
320 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
321 assert(!contains(New, this) &&
322 "this->replaceAllUsesWith(expr(this)) is NOT valid!");
323 assert(New->getType() == getType() &&
324 "replaceAllUses of value with new value of different type!");
326 // Notify all ValueHandles (if present) that this value is going away.
328 ValueHandleBase::ValueIsRAUWd(this, New);
329 if (isUsedByMetadata())
330 ValueAsMetadata::handleRAUW(this, New);
332 while (!use_empty()) {
334 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
335 // constant because they are uniqued.
336 if (auto *C = dyn_cast<Constant>(U.getUser())) {
337 if (!isa<GlobalValue>(C)) {
338 C->replaceUsesOfWithOnConstant(this, New, &U);
346 if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
347 BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
350 // Like replaceAllUsesWith except it does not handle constants or basic blocks.
351 // This routine leaves uses within BB.
352 void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) {
353 assert(New && "Value::replaceUsesOutsideBlock(<null>, BB) is invalid!");
354 assert(!contains(New, this) &&
355 "this->replaceUsesOutsideBlock(expr(this), BB) is NOT valid!");
356 assert(New->getType() == getType() &&
357 "replaceUses of value with new value of different type!");
358 assert(BB && "Basic block that may contain a use of 'New' must be defined\n");
360 use_iterator UI = use_begin(), E = use_end();
364 auto *Usr = dyn_cast<Instruction>(U.getUser());
365 if (Usr && Usr->getParent() == BB)
373 // Various metrics for how much to strip off of pointers.
374 enum PointerStripKind {
376 PSK_ZeroIndicesAndAliases,
377 PSK_InBoundsConstantIndices,
381 template <PointerStripKind StripKind>
382 static Value *stripPointerCastsAndOffsets(Value *V) {
383 if (!V->getType()->isPointerTy())
386 // Even though we don't look through PHI nodes, we could be called on an
387 // instruction in an unreachable block, which may be on a cycle.
388 SmallPtrSet<Value *, 4> Visited;
392 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
394 case PSK_ZeroIndicesAndAliases:
395 case PSK_ZeroIndices:
396 if (!GEP->hasAllZeroIndices())
399 case PSK_InBoundsConstantIndices:
400 if (!GEP->hasAllConstantIndices())
404 if (!GEP->isInBounds())
408 V = GEP->getPointerOperand();
409 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
410 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
411 V = cast<Operator>(V)->getOperand(0);
412 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
413 if (StripKind == PSK_ZeroIndices || GA->mayBeOverridden())
415 V = GA->getAliasee();
419 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
420 } while (Visited.insert(V).second);
426 Value *Value::stripPointerCasts() {
427 return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
430 Value *Value::stripPointerCastsNoFollowAliases() {
431 return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
434 Value *Value::stripInBoundsConstantOffsets() {
435 return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
438 Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
440 if (!getType()->isPointerTy())
443 assert(Offset.getBitWidth() == DL.getPointerSizeInBits(cast<PointerType>(
444 getType())->getAddressSpace()) &&
445 "The offset must have exactly as many bits as our pointer.");
447 // Even though we don't look through PHI nodes, we could be called on an
448 // instruction in an unreachable block, which may be on a cycle.
449 SmallPtrSet<Value *, 4> Visited;
450 Visited.insert(this);
453 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
454 if (!GEP->isInBounds())
456 APInt GEPOffset(Offset);
457 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
460 V = GEP->getPointerOperand();
461 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
462 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
463 V = cast<Operator>(V)->getOperand(0);
464 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
465 V = GA->getAliasee();
469 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
470 } while (Visited.insert(V).second);
475 Value *Value::stripInBoundsOffsets() {
476 return stripPointerCastsAndOffsets<PSK_InBounds>(this);
479 /// \brief Check if Value is always a dereferenceable pointer.
481 /// Test if V is always a pointer to allocated and suitably aligned memory for
482 /// a simple load or store.
483 static bool isDereferenceablePointer(const Value *V, const DataLayout *DL,
484 SmallPtrSetImpl<const Value *> &Visited) {
485 // Note that it is not safe to speculate into a malloc'd region because
486 // malloc may return null.
488 // These are obviously ok.
489 if (isa<AllocaInst>(V)) return true;
491 // It's not always safe to follow a bitcast, for example:
492 // bitcast i8* (alloca i8) to i32*
493 // would result in a 4-byte load from a 1-byte alloca. However,
494 // if we're casting from a pointer from a type of larger size
495 // to a type of smaller size (or the same size), and the alignment
496 // is at least as large as for the resulting pointer type, then
497 // we can look through the bitcast.
499 if (const BitCastInst* BC = dyn_cast<BitCastInst>(V)) {
500 Type *STy = BC->getSrcTy()->getPointerElementType(),
501 *DTy = BC->getDestTy()->getPointerElementType();
502 if (STy->isSized() && DTy->isSized() &&
503 (DL->getTypeStoreSize(STy) >=
504 DL->getTypeStoreSize(DTy)) &&
505 (DL->getABITypeAlignment(STy) >=
506 DL->getABITypeAlignment(DTy)))
507 return isDereferenceablePointer(BC->getOperand(0), DL, Visited);
510 // Global variables which can't collapse to null are ok.
511 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
512 return !GV->hasExternalWeakLinkage();
514 // byval arguments are okay. Arguments specifically marked as
515 // dereferenceable are okay too.
516 if (const Argument *A = dyn_cast<Argument>(V)) {
517 if (A->hasByValAttr())
519 else if (uint64_t Bytes = A->getDereferenceableBytes()) {
520 Type *Ty = V->getType()->getPointerElementType();
521 if (Ty->isSized() && DL && DL->getTypeStoreSize(Ty) <= Bytes)
528 // Return values from call sites specifically marked as dereferenceable are
530 if (ImmutableCallSite CS = V) {
531 if (uint64_t Bytes = CS.getDereferenceableBytes(0)) {
532 Type *Ty = V->getType()->getPointerElementType();
533 if (Ty->isSized() && DL && DL->getTypeStoreSize(Ty) <= Bytes)
538 // For GEPs, determine if the indexing lands within the allocated object.
539 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
540 // Conservatively require that the base pointer be fully dereferenceable.
541 if (!Visited.insert(GEP->getOperand(0)).second)
543 if (!isDereferenceablePointer(GEP->getOperand(0), DL, Visited))
545 // Check the indices.
546 gep_type_iterator GTI = gep_type_begin(GEP);
547 for (User::const_op_iterator I = GEP->op_begin()+1,
548 E = GEP->op_end(); I != E; ++I) {
551 // Struct indices can't be out of bounds.
552 if (isa<StructType>(Ty))
554 ConstantInt *CI = dyn_cast<ConstantInt>(Index);
557 // Zero is always ok.
560 // Check to see that it's within the bounds of an array.
561 ArrayType *ATy = dyn_cast<ArrayType>(Ty);
564 if (CI->getValue().getActiveBits() > 64)
566 if (CI->getZExtValue() >= ATy->getNumElements())
569 // Indices check out; this is dereferenceable.
573 if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
574 return isDereferenceablePointer(ASC->getOperand(0), DL, Visited);
576 // If we don't know, assume the worst.
580 bool Value::isDereferenceablePointer(const DataLayout *DL) const {
581 // When dereferenceability information is provided by a dereferenceable
582 // attribute, we know exactly how many bytes are dereferenceable. If we can
583 // determine the exact offset to the attributed variable, we can use that
585 Type *Ty = getType()->getPointerElementType();
586 if (Ty->isSized() && DL) {
587 APInt Offset(DL->getTypeStoreSizeInBits(getType()), 0);
588 const Value *BV = stripAndAccumulateInBoundsConstantOffsets(*DL, Offset);
590 APInt DerefBytes(Offset.getBitWidth(), 0);
591 if (const Argument *A = dyn_cast<Argument>(BV))
592 DerefBytes = A->getDereferenceableBytes();
593 else if (ImmutableCallSite CS = BV)
594 DerefBytes = CS.getDereferenceableBytes(0);
596 if (DerefBytes.getBoolValue() && Offset.isNonNegative()) {
597 if (DerefBytes.uge(Offset + DL->getTypeStoreSize(Ty)))
602 SmallPtrSet<const Value *, 32> Visited;
603 return ::isDereferenceablePointer(this, DL, Visited);
606 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
607 const BasicBlock *PredBB) {
608 PHINode *PN = dyn_cast<PHINode>(this);
609 if (PN && PN->getParent() == CurBB)
610 return PN->getIncomingValueForBlock(PredBB);
614 LLVMContext &Value::getContext() const { return VTy->getContext(); }
616 void Value::reverseUseList() {
617 if (!UseList || !UseList->Next)
618 // No need to reverse 0 or 1 uses.
622 Use *Current = UseList->Next;
623 Head->Next = nullptr;
625 Use *Next = Current->Next;
626 Current->Next = Head;
627 Head->setPrev(&Current->Next);
632 Head->setPrev(&UseList);
635 //===----------------------------------------------------------------------===//
636 // ValueHandleBase Class
637 //===----------------------------------------------------------------------===//
639 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
640 assert(List && "Handle list is null?");
642 // Splice ourselves into the list.
647 Next->setPrevPtr(&Next);
648 assert(V == Next->V && "Added to wrong list?");
652 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
653 assert(List && "Must insert after existing node");
656 setPrevPtr(&List->Next);
659 Next->setPrevPtr(&Next);
662 void ValueHandleBase::AddToUseList() {
663 assert(V && "Null pointer doesn't have a use list!");
665 LLVMContextImpl *pImpl = V->getContext().pImpl;
667 if (V->HasValueHandle) {
668 // If this value already has a ValueHandle, then it must be in the
669 // ValueHandles map already.
670 ValueHandleBase *&Entry = pImpl->ValueHandles[V];
671 assert(Entry && "Value doesn't have any handles?");
672 AddToExistingUseList(&Entry);
676 // Ok, it doesn't have any handles yet, so we must insert it into the
677 // DenseMap. However, doing this insertion could cause the DenseMap to
678 // reallocate itself, which would invalidate all of the PrevP pointers that
679 // point into the old table. Handle this by checking for reallocation and
680 // updating the stale pointers only if needed.
681 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
682 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
684 ValueHandleBase *&Entry = Handles[V];
685 assert(!Entry && "Value really did already have handles?");
686 AddToExistingUseList(&Entry);
687 V->HasValueHandle = true;
689 // If reallocation didn't happen or if this was the first insertion, don't
691 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
692 Handles.size() == 1) {
696 // Okay, reallocation did happen. Fix the Prev Pointers.
697 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
698 E = Handles.end(); I != E; ++I) {
699 assert(I->second && I->first == I->second->V &&
700 "List invariant broken!");
701 I->second->setPrevPtr(&I->second);
705 void ValueHandleBase::RemoveFromUseList() {
706 assert(V && V->HasValueHandle &&
707 "Pointer doesn't have a use list!");
709 // Unlink this from its use list.
710 ValueHandleBase **PrevPtr = getPrevPtr();
711 assert(*PrevPtr == this && "List invariant broken");
715 assert(Next->getPrevPtr() == &Next && "List invariant broken");
716 Next->setPrevPtr(PrevPtr);
720 // If the Next pointer was null, then it is possible that this was the last
721 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
723 LLVMContextImpl *pImpl = V->getContext().pImpl;
724 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
725 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
727 V->HasValueHandle = false;
732 void ValueHandleBase::ValueIsDeleted(Value *V) {
733 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
735 // Get the linked list base, which is guaranteed to exist since the
736 // HasValueHandle flag is set.
737 LLVMContextImpl *pImpl = V->getContext().pImpl;
738 ValueHandleBase *Entry = pImpl->ValueHandles[V];
739 assert(Entry && "Value bit set but no entries exist");
741 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
742 // and remove themselves from the list without breaking our iteration. This
743 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
744 // Note that we deliberately do not the support the case when dropping a value
745 // handle results in a new value handle being permanently added to the list
746 // (as might occur in theory for CallbackVH's): the new value handle will not
747 // be processed and the checking code will mete out righteous punishment if
748 // the handle is still present once we have finished processing all the other
749 // value handles (it is fine to momentarily add then remove a value handle).
750 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
751 Iterator.RemoveFromUseList();
752 Iterator.AddToExistingUseListAfter(Entry);
753 assert(Entry->Next == &Iterator && "Loop invariant broken.");
755 switch (Entry->getKind()) {
759 // Mark that this value has been deleted by setting it to an invalid Value
761 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
764 // Weak just goes to null, which will unlink it from the list.
765 Entry->operator=(nullptr);
768 // Forward to the subclass's implementation.
769 static_cast<CallbackVH*>(Entry)->deleted();
774 // All callbacks, weak references, and assertingVHs should be dropped by now.
775 if (V->HasValueHandle) {
776 #ifndef NDEBUG // Only in +Asserts mode...
777 dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
779 if (pImpl->ValueHandles[V]->getKind() == Assert)
780 llvm_unreachable("An asserting value handle still pointed to this"
784 llvm_unreachable("All references to V were not removed?");
789 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
790 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
791 assert(Old != New && "Changing value into itself!");
792 assert(Old->getType() == New->getType() &&
793 "replaceAllUses of value with new value of different type!");
795 // Get the linked list base, which is guaranteed to exist since the
796 // HasValueHandle flag is set.
797 LLVMContextImpl *pImpl = Old->getContext().pImpl;
798 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
800 assert(Entry && "Value bit set but no entries exist");
802 // We use a local ValueHandleBase as an iterator so that
803 // ValueHandles can add and remove themselves from the list without
804 // breaking our iteration. This is not really an AssertingVH; we
805 // just have to give ValueHandleBase some kind.
806 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
807 Iterator.RemoveFromUseList();
808 Iterator.AddToExistingUseListAfter(Entry);
809 assert(Entry->Next == &Iterator && "Loop invariant broken.");
811 switch (Entry->getKind()) {
813 // Asserting handle does not follow RAUW implicitly.
816 // Tracking goes to new value like a WeakVH. Note that this may make it
817 // something incompatible with its templated type. We don't want to have a
818 // virtual (or inline) interface to handle this though, so instead we make
819 // the TrackingVH accessors guarantee that a client never sees this value.
823 // Weak goes to the new value, which will unlink it from Old's list.
824 Entry->operator=(New);
827 // Forward to the subclass's implementation.
828 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
834 // If any new tracking or weak value handles were added while processing the
835 // list, then complain about it now.
836 if (Old->HasValueHandle)
837 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
838 switch (Entry->getKind()) {
841 dbgs() << "After RAUW from " << *Old->getType() << " %"
842 << Old->getName() << " to " << *New->getType() << " %"
843 << New->getName() << "\n";
844 llvm_unreachable("A tracking or weak value handle still pointed to the"
852 // Pin the vtable to this file.
853 void CallbackVH::anchor() {}