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 V = cast<Operator>(V)->getOperand(0);
370 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
371 if (StripKind == PSK_ZeroIndices || GA->mayBeOverridden())
373 V = GA->getAliasee();
377 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
378 } while (Visited.insert(V));
384 Value *Value::stripPointerCasts() {
385 return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
388 Value *Value::stripPointerCastsNoFollowAliases() {
389 return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
392 Value *Value::stripInBoundsConstantOffsets() {
393 return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
396 Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
398 if (!getType()->isPointerTy())
401 assert(Offset.getBitWidth() == DL.getPointerSizeInBits(cast<PointerType>(
402 getType())->getAddressSpace()) &&
403 "The offset must have exactly as many bits as our pointer.");
405 // Even though we don't look through PHI nodes, we could be called on an
406 // instruction in an unreachable block, which may be on a cycle.
407 SmallPtrSet<Value *, 4> Visited;
408 Visited.insert(this);
411 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
412 if (!GEP->isInBounds())
414 APInt GEPOffset(Offset);
415 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
418 V = GEP->getPointerOperand();
419 } else if (Operator::getOpcode(V) == Instruction::BitCast) {
420 V = cast<Operator>(V)->getOperand(0);
421 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
422 V = GA->getAliasee();
426 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
427 } while (Visited.insert(V));
432 Value *Value::stripInBoundsOffsets() {
433 return stripPointerCastsAndOffsets<PSK_InBounds>(this);
436 /// isDereferenceablePointer - Test if this value is always a pointer to
437 /// allocated and suitably aligned memory for a simple load or store.
438 static bool isDereferenceablePointer(const Value *V,
439 SmallPtrSet<const Value *, 32> &Visited) {
440 // Note that it is not safe to speculate into a malloc'd region because
441 // malloc may return null.
442 // It's also not always safe to follow a bitcast, for example:
443 // bitcast i8* (alloca i8) to i32*
444 // would result in a 4-byte load from a 1-byte alloca. Some cases could
445 // be handled using DataLayout to check sizes and alignments though.
447 // These are obviously ok.
448 if (isa<AllocaInst>(V)) return true;
450 // Global variables which can't collapse to null are ok.
451 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
452 return !GV->hasExternalWeakLinkage();
454 // byval arguments are ok.
455 if (const Argument *A = dyn_cast<Argument>(V))
456 return A->hasByValAttr();
458 // For GEPs, determine if the indexing lands within the allocated object.
459 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
460 // Conservatively require that the base pointer be fully dereferenceable.
461 if (!Visited.insert(GEP->getOperand(0)))
463 if (!isDereferenceablePointer(GEP->getOperand(0), Visited))
465 // Check the indices.
466 gep_type_iterator GTI = gep_type_begin(GEP);
467 for (User::const_op_iterator I = GEP->op_begin()+1,
468 E = GEP->op_end(); I != E; ++I) {
471 // Struct indices can't be out of bounds.
472 if (isa<StructType>(Ty))
474 ConstantInt *CI = dyn_cast<ConstantInt>(Index);
477 // Zero is always ok.
480 // Check to see that it's within the bounds of an array.
481 ArrayType *ATy = dyn_cast<ArrayType>(Ty);
484 if (CI->getValue().getActiveBits() > 64)
486 if (CI->getZExtValue() >= ATy->getNumElements())
489 // Indices check out; this is dereferenceable.
493 // If we don't know, assume the worst.
497 /// isDereferenceablePointer - Test if this value is always a pointer to
498 /// allocated and suitably aligned memory for a simple load or store.
499 bool Value::isDereferenceablePointer() const {
500 SmallPtrSet<const Value *, 32> Visited;
501 return ::isDereferenceablePointer(this, Visited);
504 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
505 /// return the value in the PHI node corresponding to PredBB. If not, return
506 /// ourself. This is useful if you want to know the value something has in a
507 /// predecessor block.
508 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
509 const BasicBlock *PredBB) {
510 PHINode *PN = dyn_cast<PHINode>(this);
511 if (PN && PN->getParent() == CurBB)
512 return PN->getIncomingValueForBlock(PredBB);
516 LLVMContext &Value::getContext() const { return VTy->getContext(); }
518 //===----------------------------------------------------------------------===//
519 // ValueHandleBase Class
520 //===----------------------------------------------------------------------===//
522 /// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
523 /// List is known to point into the existing use list.
524 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
525 assert(List && "Handle list is null?");
527 // Splice ourselves into the list.
532 Next->setPrevPtr(&Next);
533 assert(VP.getPointer() == Next->VP.getPointer() && "Added to wrong list?");
537 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
538 assert(List && "Must insert after existing node");
541 setPrevPtr(&List->Next);
544 Next->setPrevPtr(&Next);
547 /// AddToUseList - Add this ValueHandle to the use list for VP.
548 void ValueHandleBase::AddToUseList() {
549 assert(VP.getPointer() && "Null pointer doesn't have a use list!");
551 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
553 if (VP.getPointer()->HasValueHandle) {
554 // If this value already has a ValueHandle, then it must be in the
555 // ValueHandles map already.
556 ValueHandleBase *&Entry = pImpl->ValueHandles[VP.getPointer()];
557 assert(Entry != 0 && "Value doesn't have any handles?");
558 AddToExistingUseList(&Entry);
562 // Ok, it doesn't have any handles yet, so we must insert it into the
563 // DenseMap. However, doing this insertion could cause the DenseMap to
564 // reallocate itself, which would invalidate all of the PrevP pointers that
565 // point into the old table. Handle this by checking for reallocation and
566 // updating the stale pointers only if needed.
567 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
568 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
570 ValueHandleBase *&Entry = Handles[VP.getPointer()];
571 assert(Entry == 0 && "Value really did already have handles?");
572 AddToExistingUseList(&Entry);
573 VP.getPointer()->HasValueHandle = true;
575 // If reallocation didn't happen or if this was the first insertion, don't
577 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
578 Handles.size() == 1) {
582 // Okay, reallocation did happen. Fix the Prev Pointers.
583 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
584 E = Handles.end(); I != E; ++I) {
585 assert(I->second && I->first == I->second->VP.getPointer() &&
586 "List invariant broken!");
587 I->second->setPrevPtr(&I->second);
591 /// RemoveFromUseList - Remove this ValueHandle from its current use list.
592 void ValueHandleBase::RemoveFromUseList() {
593 assert(VP.getPointer() && VP.getPointer()->HasValueHandle &&
594 "Pointer doesn't have a use list!");
596 // Unlink this from its use list.
597 ValueHandleBase **PrevPtr = getPrevPtr();
598 assert(*PrevPtr == this && "List invariant broken");
602 assert(Next->getPrevPtr() == &Next && "List invariant broken");
603 Next->setPrevPtr(PrevPtr);
607 // If the Next pointer was null, then it is possible that this was the last
608 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
610 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
611 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
612 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
613 Handles.erase(VP.getPointer());
614 VP.getPointer()->HasValueHandle = false;
619 void ValueHandleBase::ValueIsDeleted(Value *V) {
620 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
622 // Get the linked list base, which is guaranteed to exist since the
623 // HasValueHandle flag is set.
624 LLVMContextImpl *pImpl = V->getContext().pImpl;
625 ValueHandleBase *Entry = pImpl->ValueHandles[V];
626 assert(Entry && "Value bit set but no entries exist");
628 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
629 // and remove themselves from the list without breaking our iteration. This
630 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
631 // Note that we deliberately do not the support the case when dropping a value
632 // handle results in a new value handle being permanently added to the list
633 // (as might occur in theory for CallbackVH's): the new value handle will not
634 // be processed and the checking code will mete out righteous punishment if
635 // the handle is still present once we have finished processing all the other
636 // value handles (it is fine to momentarily add then remove a value handle).
637 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
638 Iterator.RemoveFromUseList();
639 Iterator.AddToExistingUseListAfter(Entry);
640 assert(Entry->Next == &Iterator && "Loop invariant broken.");
642 switch (Entry->getKind()) {
646 // Mark that this value has been deleted by setting it to an invalid Value
648 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
651 // Weak just goes to null, which will unlink it from the list.
655 // Forward to the subclass's implementation.
656 static_cast<CallbackVH*>(Entry)->deleted();
661 // All callbacks, weak references, and assertingVHs should be dropped by now.
662 if (V->HasValueHandle) {
663 #ifndef NDEBUG // Only in +Asserts mode...
664 dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
666 if (pImpl->ValueHandles[V]->getKind() == Assert)
667 llvm_unreachable("An asserting value handle still pointed to this"
671 llvm_unreachable("All references to V were not removed?");
676 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
677 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
678 assert(Old != New && "Changing value into itself!");
680 // Get the linked list base, which is guaranteed to exist since the
681 // HasValueHandle flag is set.
682 LLVMContextImpl *pImpl = Old->getContext().pImpl;
683 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
685 assert(Entry && "Value bit set but no entries exist");
687 // We use a local ValueHandleBase as an iterator so that
688 // ValueHandles can add and remove themselves from the list without
689 // breaking our iteration. This is not really an AssertingVH; we
690 // just have to give ValueHandleBase some kind.
691 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
692 Iterator.RemoveFromUseList();
693 Iterator.AddToExistingUseListAfter(Entry);
694 assert(Entry->Next == &Iterator && "Loop invariant broken.");
696 switch (Entry->getKind()) {
698 // Asserting handle does not follow RAUW implicitly.
701 // Tracking goes to new value like a WeakVH. Note that this may make it
702 // something incompatible with its templated type. We don't want to have a
703 // virtual (or inline) interface to handle this though, so instead we make
704 // the TrackingVH accessors guarantee that a client never sees this value.
708 // Weak goes to the new value, which will unlink it from Old's list.
709 Entry->operator=(New);
712 // Forward to the subclass's implementation.
713 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
719 // If any new tracking or weak value handles were added while processing the
720 // list, then complain about it now.
721 if (Old->HasValueHandle)
722 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
723 switch (Entry->getKind()) {
726 dbgs() << "After RAUW from " << *Old->getType() << " %"
727 << Old->getName() << " to " << *New->getType() << " %"
728 << New->getName() << "\n";
729 llvm_unreachable("A tracking or weak value handle still pointed to the"
737 // Default implementation for CallbackVH.
738 void CallbackVH::allUsesReplacedWith(Value *) {}
740 void CallbackVH::deleted() {