1 //===-- Value.cpp - Implement the Value class -----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the Value, ValueHandle, and User classes.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/IR/Value.h"
15 #include "LLVMContextImpl.h"
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/IR/Constant.h"
19 #include "llvm/IR/Constants.h"
20 #include "llvm/IR/DerivedTypes.h"
21 #include "llvm/IR/InstrTypes.h"
22 #include "llvm/IR/Instructions.h"
23 #include "llvm/IR/Module.h"
24 #include "llvm/IR/Operator.h"
25 #include "llvm/IR/ValueSymbolTable.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/GetElementPtrTypeIterator.h"
29 #include "llvm/Support/LeakDetector.h"
30 #include "llvm/Support/ManagedStatic.h"
31 #include "llvm/Support/ValueHandle.h"
35 //===----------------------------------------------------------------------===//
37 //===----------------------------------------------------------------------===//
39 static inline Type *checkType(Type *Ty) {
40 assert(Ty && "Value defined with a null type: Error!");
41 return const_cast<Type*>(Ty);
44 Value::Value(Type *ty, unsigned scid)
45 : SubclassID(scid), HasValueHandle(0),
46 SubclassOptionalData(0), SubclassData(0), VTy((Type*)checkType(ty)),
48 // FIXME: Why isn't this in the subclass gunk??
49 // Note, we cannot call isa<CallInst> before the CallInst has been
51 if (SubclassID == Instruction::Call || SubclassID == Instruction::Invoke)
52 assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) &&
53 "invalid CallInst type!");
54 else if (SubclassID != BasicBlockVal &&
55 (SubclassID < ConstantFirstVal || SubclassID > ConstantLastVal))
56 assert((VTy->isFirstClassType() || VTy->isVoidTy()) &&
57 "Cannot create non-first-class values except for constants!");
61 // Notify all ValueHandles (if present) that this value is going away.
63 ValueHandleBase::ValueIsDeleted(this);
65 #ifndef NDEBUG // Only in -g mode...
66 // Check to make sure that there are no uses of this value that are still
67 // around when the value is destroyed. If there are, then we have a dangling
68 // reference and something is wrong. This code is here to print out what is
69 // still being referenced. The value in question should be printed as
73 dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n";
74 for (use_iterator I = use_begin(), E = use_end(); I != E; ++I)
75 dbgs() << "Use still stuck around after Def is destroyed:"
79 assert(use_empty() && "Uses remain when a value is destroyed!");
81 // If this value is named, destroy the name. This should not be in a symtab
83 if (Name && SubclassID != MDStringVal)
86 // There should be no uses of this object anymore, remove it.
87 LeakDetector::removeGarbageObject(this);
90 /// hasNUses - Return true if this Value has exactly N users.
92 bool Value::hasNUses(unsigned N) const {
93 const_use_iterator UI = use_begin(), E = use_end();
96 if (UI == E) return false; // Too few.
100 /// hasNUsesOrMore - Return true if this value has N users or more. This is
101 /// logically equivalent to getNumUses() >= N.
103 bool Value::hasNUsesOrMore(unsigned N) const {
104 const_use_iterator UI = use_begin(), E = use_end();
107 if (UI == E) return false; // Too few.
112 /// isUsedInBasicBlock - Return true if this value is used in the specified
114 bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
115 // This can be computed either by scanning the instructions in BB, or by
116 // scanning the use list of this Value. Both lists can be very long, but
117 // usually one is quite short.
119 // Scan both lists simultaneously until one is exhausted. This limits the
120 // search to the shorter list.
121 BasicBlock::const_iterator BI = BB->begin(), BE = BB->end();
122 const_use_iterator UI = use_begin(), UE = use_end();
123 for (; BI != BE && UI != UE; ++BI, ++UI) {
124 // Scan basic block: Check if this Value is used by the instruction at BI.
125 if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end())
127 // Scan use list: Check if the use at UI is in BB.
128 const Instruction *User = dyn_cast<Instruction>(*UI);
129 if (User && User->getParent() == BB)
136 /// getNumUses - This method computes the number of uses of this Value. This
137 /// is a linear time operation. Use hasOneUse or hasNUses to check for specific
139 unsigned Value::getNumUses() const {
140 return (unsigned)std::distance(use_begin(), use_end());
143 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
145 if (Instruction *I = dyn_cast<Instruction>(V)) {
146 if (BasicBlock *P = I->getParent())
147 if (Function *PP = P->getParent())
148 ST = &PP->getValueSymbolTable();
149 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
150 if (Function *P = BB->getParent())
151 ST = &P->getValueSymbolTable();
152 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
153 if (Module *P = GV->getParent())
154 ST = &P->getValueSymbolTable();
155 } else if (Argument *A = dyn_cast<Argument>(V)) {
156 if (Function *P = A->getParent())
157 ST = &P->getValueSymbolTable();
158 } else if (isa<MDString>(V))
161 assert(isa<Constant>(V) && "Unknown value type!");
162 return true; // no name is setable for this.
167 StringRef Value::getName() const {
168 // Make sure the empty string is still a C string. For historical reasons,
169 // some clients want to call .data() on the result and expect it to be null
171 if (!Name) return StringRef("", 0);
172 return Name->getKey();
175 void Value::setName(const Twine &NewName) {
176 assert(SubclassID != MDStringVal &&
177 "Cannot set the name of MDString with this method!");
179 // Fast path for common IRBuilder case of setName("") when there is no name.
180 if (NewName.isTriviallyEmpty() && !hasName())
183 SmallString<256> NameData;
184 StringRef NameRef = NewName.toStringRef(NameData);
186 // Name isn't changing?
187 if (getName() == NameRef)
190 assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
192 // Get the symbol table to update for this object.
193 ValueSymbolTable *ST;
194 if (getSymTab(this, ST))
195 return; // Cannot set a name on this value (e.g. constant).
197 if (Function *F = dyn_cast<Function>(this))
198 getContext().pImpl->IntrinsicIDCache.erase(F);
200 if (!ST) { // No symbol table to update? Just do the change.
201 if (NameRef.empty()) {
202 // Free the name for this value.
211 // NOTE: Could optimize for the case the name is shrinking to not deallocate
214 // Create the new name.
215 Name = ValueName::Create(NameRef.begin(), NameRef.end());
216 Name->setValue(this);
220 // NOTE: Could optimize for the case the name is shrinking to not deallocate
224 ST->removeValueName(Name);
232 // Name is changing to something new.
233 Name = ST->createValueName(NameRef, this);
237 /// takeName - transfer the name from V to this value, setting V's name to
238 /// empty. It is an error to call V->takeName(V).
239 void Value::takeName(Value *V) {
240 assert(SubclassID != MDStringVal && "Cannot take the name of an MDString!");
242 ValueSymbolTable *ST = 0;
243 // If this value has a name, drop it.
245 // Get the symtab this is in.
246 if (getSymTab(this, ST)) {
247 // We can't set a name on this value, but we need to clear V's name if
249 if (V->hasName()) V->setName("");
250 return; // Cannot set a name on this value (e.g. constant).
255 ST->removeValueName(Name);
260 // Now we know that this has no name.
262 // If V has no name either, we're done.
263 if (!V->hasName()) return;
265 // Get this's symtab if we didn't before.
267 if (getSymTab(this, ST)) {
270 return; // Cannot set a name on this value (e.g. constant).
274 // Get V's ST, this should always succed, because V has a name.
275 ValueSymbolTable *VST;
276 bool Failure = getSymTab(V, VST);
277 assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
279 // If these values are both in the same symtab, we can do this very fast.
280 // This works even if both values have no symtab yet.
285 Name->setValue(this);
289 // Otherwise, things are slightly more complex. Remove V's name from VST and
290 // then reinsert it into ST.
293 VST->removeValueName(V->Name);
296 Name->setValue(this);
299 ST->reinsertValue(this);
303 void Value::replaceAllUsesWith(Value *New) {
304 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
305 assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!");
306 assert(New->getType() == getType() &&
307 "replaceAllUses of value with new value of different type!");
309 // Notify all ValueHandles (if present) that this value is going away.
311 ValueHandleBase::ValueIsRAUWd(this, New);
313 while (!use_empty()) {
315 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
316 // constant because they are uniqued.
317 if (Constant *C = dyn_cast<Constant>(U.getUser())) {
318 if (!isa<GlobalValue>(C)) {
319 C->replaceUsesOfWithOnConstant(this, New, &U);
327 if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
328 BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
332 // Various metrics for how much to strip off of pointers.
333 enum PointerStripKind {
335 PSK_ZeroIndicesAndAliases,
336 PSK_InBoundsConstantIndices,
340 template <PointerStripKind StripKind>
341 static Value *stripPointerCastsAndOffsets(Value *V) {
342 if (!V->getType()->isPointerTy())
345 // Even though we don't look through PHI nodes, we could be called on an
346 // instruction in an unreachable block, which may be on a cycle.
347 SmallPtrSet<Value *, 4> Visited;
351 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
353 case PSK_ZeroIndicesAndAliases:
354 case PSK_ZeroIndices:
355 if (!GEP->hasAllZeroIndices())
358 case PSK_InBoundsConstantIndices:
359 if (!GEP->hasAllConstantIndices())
363 if (!GEP->isInBounds())
367 V = GEP->getPointerOperand();
368 } else if (Operator::getOpcode(V) == Instruction::BitCast ||
369 Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
370 V = cast<Operator>(V)->getOperand(0);
371 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
372 if (StripKind == PSK_ZeroIndices || GA->mayBeOverridden())
374 V = GA->getAliasee();
378 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
379 } while (Visited.insert(V));
385 Value *Value::stripPointerCasts() {
386 return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
389 Value *Value::stripPointerCastsNoFollowAliases() {
390 return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
393 Value *Value::stripInBoundsConstantOffsets() {
394 return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
397 Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
399 if (!getType()->isPointerTy())
402 assert(Offset.getBitWidth() == DL.getPointerSizeInBits(cast<PointerType>(
403 getType())->getAddressSpace()) &&
404 "The offset must have exactly as many bits as our pointer.");
406 // Even though we don't look through PHI nodes, we could be called on an
407 // instruction in an unreachable block, which may be on a cycle.
408 SmallPtrSet<Value *, 4> Visited;
409 Visited.insert(this);
412 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
413 if (!GEP->isInBounds())
415 APInt GEPOffset(Offset);
416 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
419 V = GEP->getPointerOperand();
420 } else if (Operator::getOpcode(V) == Instruction::BitCast) {
421 V = cast<Operator>(V)->getOperand(0);
422 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
423 V = GA->getAliasee();
427 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
428 } while (Visited.insert(V));
433 Value *Value::stripInBoundsOffsets() {
434 return stripPointerCastsAndOffsets<PSK_InBounds>(this);
437 /// isDereferenceablePointer - Test if this value is always a pointer to
438 /// allocated and suitably aligned memory for a simple load or store.
439 static bool isDereferenceablePointer(const Value *V,
440 SmallPtrSet<const Value *, 32> &Visited) {
441 // Note that it is not safe to speculate into a malloc'd region because
442 // malloc may return null.
443 // It's also not always safe to follow a bitcast, for example:
444 // bitcast i8* (alloca i8) to i32*
445 // would result in a 4-byte load from a 1-byte alloca. Some cases could
446 // be handled using DataLayout to check sizes and alignments though.
448 // These are obviously ok.
449 if (isa<AllocaInst>(V)) return true;
451 // Global variables which can't collapse to null are ok.
452 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
453 return !GV->hasExternalWeakLinkage();
455 // byval arguments are ok.
456 if (const Argument *A = dyn_cast<Argument>(V))
457 return A->hasByValAttr();
459 // For GEPs, determine if the indexing lands within the allocated object.
460 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
461 // Conservatively require that the base pointer be fully dereferenceable.
462 if (!Visited.insert(GEP->getOperand(0)))
464 if (!isDereferenceablePointer(GEP->getOperand(0), Visited))
466 // Check the indices.
467 gep_type_iterator GTI = gep_type_begin(GEP);
468 for (User::const_op_iterator I = GEP->op_begin()+1,
469 E = GEP->op_end(); I != E; ++I) {
472 // Struct indices can't be out of bounds.
473 if (isa<StructType>(Ty))
475 ConstantInt *CI = dyn_cast<ConstantInt>(Index);
478 // Zero is always ok.
481 // Check to see that it's within the bounds of an array.
482 ArrayType *ATy = dyn_cast<ArrayType>(Ty);
485 if (CI->getValue().getActiveBits() > 64)
487 if (CI->getZExtValue() >= ATy->getNumElements())
490 // Indices check out; this is dereferenceable.
494 // If we don't know, assume the worst.
498 /// isDereferenceablePointer - Test if this value is always a pointer to
499 /// allocated and suitably aligned memory for a simple load or store.
500 bool Value::isDereferenceablePointer() const {
501 SmallPtrSet<const Value *, 32> Visited;
502 return ::isDereferenceablePointer(this, Visited);
505 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
506 /// return the value in the PHI node corresponding to PredBB. If not, return
507 /// ourself. This is useful if you want to know the value something has in a
508 /// predecessor block.
509 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
510 const BasicBlock *PredBB) {
511 PHINode *PN = dyn_cast<PHINode>(this);
512 if (PN && PN->getParent() == CurBB)
513 return PN->getIncomingValueForBlock(PredBB);
517 LLVMContext &Value::getContext() const { return VTy->getContext(); }
519 //===----------------------------------------------------------------------===//
520 // ValueHandleBase Class
521 //===----------------------------------------------------------------------===//
523 /// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
524 /// List is known to point into the existing use list.
525 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
526 assert(List && "Handle list is null?");
528 // Splice ourselves into the list.
533 Next->setPrevPtr(&Next);
534 assert(VP.getPointer() == Next->VP.getPointer() && "Added to wrong list?");
538 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
539 assert(List && "Must insert after existing node");
542 setPrevPtr(&List->Next);
545 Next->setPrevPtr(&Next);
548 /// AddToUseList - Add this ValueHandle to the use list for VP.
549 void ValueHandleBase::AddToUseList() {
550 assert(VP.getPointer() && "Null pointer doesn't have a use list!");
552 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
554 if (VP.getPointer()->HasValueHandle) {
555 // If this value already has a ValueHandle, then it must be in the
556 // ValueHandles map already.
557 ValueHandleBase *&Entry = pImpl->ValueHandles[VP.getPointer()];
558 assert(Entry != 0 && "Value doesn't have any handles?");
559 AddToExistingUseList(&Entry);
563 // Ok, it doesn't have any handles yet, so we must insert it into the
564 // DenseMap. However, doing this insertion could cause the DenseMap to
565 // reallocate itself, which would invalidate all of the PrevP pointers that
566 // point into the old table. Handle this by checking for reallocation and
567 // updating the stale pointers only if needed.
568 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
569 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
571 ValueHandleBase *&Entry = Handles[VP.getPointer()];
572 assert(Entry == 0 && "Value really did already have handles?");
573 AddToExistingUseList(&Entry);
574 VP.getPointer()->HasValueHandle = true;
576 // If reallocation didn't happen or if this was the first insertion, don't
578 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
579 Handles.size() == 1) {
583 // Okay, reallocation did happen. Fix the Prev Pointers.
584 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
585 E = Handles.end(); I != E; ++I) {
586 assert(I->second && I->first == I->second->VP.getPointer() &&
587 "List invariant broken!");
588 I->second->setPrevPtr(&I->second);
592 /// RemoveFromUseList - Remove this ValueHandle from its current use list.
593 void ValueHandleBase::RemoveFromUseList() {
594 assert(VP.getPointer() && VP.getPointer()->HasValueHandle &&
595 "Pointer doesn't have a use list!");
597 // Unlink this from its use list.
598 ValueHandleBase **PrevPtr = getPrevPtr();
599 assert(*PrevPtr == this && "List invariant broken");
603 assert(Next->getPrevPtr() == &Next && "List invariant broken");
604 Next->setPrevPtr(PrevPtr);
608 // If the Next pointer was null, then it is possible that this was the last
609 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
611 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
612 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
613 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
614 Handles.erase(VP.getPointer());
615 VP.getPointer()->HasValueHandle = false;
620 void ValueHandleBase::ValueIsDeleted(Value *V) {
621 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
623 // Get the linked list base, which is guaranteed to exist since the
624 // HasValueHandle flag is set.
625 LLVMContextImpl *pImpl = V->getContext().pImpl;
626 ValueHandleBase *Entry = pImpl->ValueHandles[V];
627 assert(Entry && "Value bit set but no entries exist");
629 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
630 // and remove themselves from the list without breaking our iteration. This
631 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
632 // Note that we deliberately do not the support the case when dropping a value
633 // handle results in a new value handle being permanently added to the list
634 // (as might occur in theory for CallbackVH's): the new value handle will not
635 // be processed and the checking code will mete out righteous punishment if
636 // the handle is still present once we have finished processing all the other
637 // value handles (it is fine to momentarily add then remove a value handle).
638 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
639 Iterator.RemoveFromUseList();
640 Iterator.AddToExistingUseListAfter(Entry);
641 assert(Entry->Next == &Iterator && "Loop invariant broken.");
643 switch (Entry->getKind()) {
647 // Mark that this value has been deleted by setting it to an invalid Value
649 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
652 // Weak just goes to null, which will unlink it from the list.
656 // Forward to the subclass's implementation.
657 static_cast<CallbackVH*>(Entry)->deleted();
662 // All callbacks, weak references, and assertingVHs should be dropped by now.
663 if (V->HasValueHandle) {
664 #ifndef NDEBUG // Only in +Asserts mode...
665 dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
667 if (pImpl->ValueHandles[V]->getKind() == Assert)
668 llvm_unreachable("An asserting value handle still pointed to this"
672 llvm_unreachable("All references to V were not removed?");
677 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
678 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
679 assert(Old != New && "Changing value into itself!");
681 // Get the linked list base, which is guaranteed to exist since the
682 // HasValueHandle flag is set.
683 LLVMContextImpl *pImpl = Old->getContext().pImpl;
684 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
686 assert(Entry && "Value bit set but no entries exist");
688 // We use a local ValueHandleBase as an iterator so that
689 // ValueHandles can add and remove themselves from the list without
690 // breaking our iteration. This is not really an AssertingVH; we
691 // just have to give ValueHandleBase some kind.
692 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
693 Iterator.RemoveFromUseList();
694 Iterator.AddToExistingUseListAfter(Entry);
695 assert(Entry->Next == &Iterator && "Loop invariant broken.");
697 switch (Entry->getKind()) {
699 // Asserting handle does not follow RAUW implicitly.
702 // Tracking goes to new value like a WeakVH. Note that this may make it
703 // something incompatible with its templated type. We don't want to have a
704 // virtual (or inline) interface to handle this though, so instead we make
705 // the TrackingVH accessors guarantee that a client never sees this value.
709 // Weak goes to the new value, which will unlink it from Old's list.
710 Entry->operator=(New);
713 // Forward to the subclass's implementation.
714 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
720 // If any new tracking or weak value handles were added while processing the
721 // list, then complain about it now.
722 if (Old->HasValueHandle)
723 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
724 switch (Entry->getKind()) {
727 dbgs() << "After RAUW from " << *Old->getType() << " %"
728 << Old->getName() << " to " << *New->getType() << " %"
729 << New->getName() << "\n";
730 llvm_unreachable("A tracking or weak value handle still pointed to the"
738 // Default implementation for CallbackVH.
739 void CallbackVH::allUsesReplacedWith(Value *) {}
741 void CallbackVH::deleted() {