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 // Start by scanning over the instructions looking for a use before we start
116 // the expensive use iteration.
117 unsigned MaxBlockSize = 3;
118 for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
119 if (std::find(I->op_begin(), I->op_end(), this) != I->op_end())
121 if (MaxBlockSize-- == 0) // If the block is larger fall back to use_iterator
125 if (MaxBlockSize != 0) // We scanned the entire block and found no use.
128 for (const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) {
129 const Instruction *User = dyn_cast<Instruction>(*I);
130 if (User && User->getParent() == BB)
137 /// getNumUses - This method computes the number of uses of this Value. This
138 /// is a linear time operation. Use hasOneUse or hasNUses to check for specific
140 unsigned Value::getNumUses() const {
141 return (unsigned)std::distance(use_begin(), use_end());
144 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
146 if (Instruction *I = dyn_cast<Instruction>(V)) {
147 if (BasicBlock *P = I->getParent())
148 if (Function *PP = P->getParent())
149 ST = &PP->getValueSymbolTable();
150 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
151 if (Function *P = BB->getParent())
152 ST = &P->getValueSymbolTable();
153 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
154 if (Module *P = GV->getParent())
155 ST = &P->getValueSymbolTable();
156 } else if (Argument *A = dyn_cast<Argument>(V)) {
157 if (Function *P = A->getParent())
158 ST = &P->getValueSymbolTable();
159 } else if (isa<MDString>(V))
162 assert(isa<Constant>(V) && "Unknown value type!");
163 return true; // no name is setable for this.
168 StringRef Value::getName() const {
169 // Make sure the empty string is still a C string. For historical reasons,
170 // some clients want to call .data() on the result and expect it to be null
172 if (!Name) return StringRef("", 0);
173 return Name->getKey();
176 void Value::setName(const Twine &NewName) {
177 assert(SubclassID != MDStringVal &&
178 "Cannot set the name of MDString with this method!");
180 // Fast path for common IRBuilder case of setName("") when there is no name.
181 if (NewName.isTriviallyEmpty() && !hasName())
184 SmallString<256> NameData;
185 StringRef NameRef = NewName.toStringRef(NameData);
187 // Name isn't changing?
188 if (getName() == NameRef)
191 assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
193 // Get the symbol table to update for this object.
194 ValueSymbolTable *ST;
195 if (getSymTab(this, ST))
196 return; // Cannot set a name on this value (e.g. constant).
198 if (!ST) { // No symbol table to update? Just do the change.
199 if (NameRef.empty()) {
200 // Free the name for this value.
209 // NOTE: Could optimize for the case the name is shrinking to not deallocate
212 // Create the new name.
213 Name = ValueName::Create(NameRef.begin(), NameRef.end());
214 Name->setValue(this);
218 // NOTE: Could optimize for the case the name is shrinking to not deallocate
222 ST->removeValueName(Name);
230 // Name is changing to something new.
231 Name = ST->createValueName(NameRef, this);
235 /// takeName - transfer the name from V to this value, setting V's name to
236 /// empty. It is an error to call V->takeName(V).
237 void Value::takeName(Value *V) {
238 assert(SubclassID != MDStringVal && "Cannot take the name of an MDString!");
240 ValueSymbolTable *ST = 0;
241 // If this value has a name, drop it.
243 // Get the symtab this is in.
244 if (getSymTab(this, ST)) {
245 // We can't set a name on this value, but we need to clear V's name if
247 if (V->hasName()) V->setName("");
248 return; // Cannot set a name on this value (e.g. constant).
253 ST->removeValueName(Name);
258 // Now we know that this has no name.
260 // If V has no name either, we're done.
261 if (!V->hasName()) return;
263 // Get this's symtab if we didn't before.
265 if (getSymTab(this, ST)) {
268 return; // Cannot set a name on this value (e.g. constant).
272 // Get V's ST, this should always succed, because V has a name.
273 ValueSymbolTable *VST;
274 bool Failure = getSymTab(V, VST);
275 assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
277 // If these values are both in the same symtab, we can do this very fast.
278 // This works even if both values have no symtab yet.
283 Name->setValue(this);
287 // Otherwise, things are slightly more complex. Remove V's name from VST and
288 // then reinsert it into ST.
291 VST->removeValueName(V->Name);
294 Name->setValue(this);
297 ST->reinsertValue(this);
301 void Value::replaceAllUsesWith(Value *New) {
302 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
303 assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!");
304 assert(New->getType() == getType() &&
305 "replaceAllUses of value with new value of different type!");
307 // Notify all ValueHandles (if present) that this value is going away.
309 ValueHandleBase::ValueIsRAUWd(this, New);
311 while (!use_empty()) {
313 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
314 // constant because they are uniqued.
315 if (Constant *C = dyn_cast<Constant>(U.getUser())) {
316 if (!isa<GlobalValue>(C)) {
317 C->replaceUsesOfWithOnConstant(this, New, &U);
325 if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
326 BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
330 // Various metrics for how much to strip off of pointers.
331 enum PointerStripKind {
333 PSK_InBoundsConstantIndices,
337 template <PointerStripKind StripKind>
338 static Value *stripPointerCastsAndOffsets(Value *V) {
339 if (!V->getType()->isPointerTy())
342 // Even though we don't look through PHI nodes, we could be called on an
343 // instruction in an unreachable block, which may be on a cycle.
344 SmallPtrSet<Value *, 4> Visited;
348 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
350 case PSK_ZeroIndices:
351 if (!GEP->hasAllZeroIndices())
354 case PSK_InBoundsConstantIndices:
355 if (!GEP->hasAllConstantIndices())
359 if (!GEP->isInBounds())
363 V = GEP->getPointerOperand();
364 } else if (Operator::getOpcode(V) == Instruction::BitCast) {
365 V = cast<Operator>(V)->getOperand(0);
366 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
367 if (GA->mayBeOverridden())
369 V = GA->getAliasee();
373 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
374 } while (Visited.insert(V));
380 Value *Value::stripPointerCasts() {
381 return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
384 Value *Value::stripInBoundsConstantOffsets() {
385 return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
388 Value *Value::stripInBoundsOffsets() {
389 return stripPointerCastsAndOffsets<PSK_InBounds>(this);
392 /// isDereferenceablePointer - Test if this value is always a pointer to
393 /// allocated and suitably aligned memory for a simple load or store.
394 static bool isDereferenceablePointer(const Value *V,
395 SmallPtrSet<const Value *, 32> &Visited) {
396 // Note that it is not safe to speculate into a malloc'd region because
397 // malloc may return null.
398 // It's also not always safe to follow a bitcast, for example:
399 // bitcast i8* (alloca i8) to i32*
400 // would result in a 4-byte load from a 1-byte alloca. Some cases could
401 // be handled using DataLayout to check sizes and alignments though.
403 // These are obviously ok.
404 if (isa<AllocaInst>(V)) return true;
406 // Global variables which can't collapse to null are ok.
407 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
408 return !GV->hasExternalWeakLinkage();
410 // byval arguments are ok.
411 if (const Argument *A = dyn_cast<Argument>(V))
412 return A->hasByValAttr();
414 // For GEPs, determine if the indexing lands within the allocated object.
415 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
416 // Conservatively require that the base pointer be fully dereferenceable.
417 if (!Visited.insert(GEP->getOperand(0)))
419 if (!isDereferenceablePointer(GEP->getOperand(0), Visited))
421 // Check the indices.
422 gep_type_iterator GTI = gep_type_begin(GEP);
423 for (User::const_op_iterator I = GEP->op_begin()+1,
424 E = GEP->op_end(); I != E; ++I) {
427 // Struct indices can't be out of bounds.
428 if (isa<StructType>(Ty))
430 ConstantInt *CI = dyn_cast<ConstantInt>(Index);
433 // Zero is always ok.
436 // Check to see that it's within the bounds of an array.
437 ArrayType *ATy = dyn_cast<ArrayType>(Ty);
440 if (CI->getValue().getActiveBits() > 64)
442 if (CI->getZExtValue() >= ATy->getNumElements())
445 // Indices check out; this is dereferenceable.
449 // If we don't know, assume the worst.
453 /// isDereferenceablePointer - Test if this value is always a pointer to
454 /// allocated and suitably aligned memory for a simple load or store.
455 bool Value::isDereferenceablePointer() const {
456 SmallPtrSet<const Value *, 32> Visited;
457 return ::isDereferenceablePointer(this, Visited);
460 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
461 /// return the value in the PHI node corresponding to PredBB. If not, return
462 /// ourself. This is useful if you want to know the value something has in a
463 /// predecessor block.
464 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
465 const BasicBlock *PredBB) {
466 PHINode *PN = dyn_cast<PHINode>(this);
467 if (PN && PN->getParent() == CurBB)
468 return PN->getIncomingValueForBlock(PredBB);
472 LLVMContext &Value::getContext() const { return VTy->getContext(); }
474 //===----------------------------------------------------------------------===//
475 // ValueHandleBase Class
476 //===----------------------------------------------------------------------===//
478 /// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
479 /// List is known to point into the existing use list.
480 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
481 assert(List && "Handle list is null?");
483 // Splice ourselves into the list.
488 Next->setPrevPtr(&Next);
489 assert(VP.getPointer() == Next->VP.getPointer() && "Added to wrong list?");
493 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
494 assert(List && "Must insert after existing node");
497 setPrevPtr(&List->Next);
500 Next->setPrevPtr(&Next);
503 /// AddToUseList - Add this ValueHandle to the use list for VP.
504 void ValueHandleBase::AddToUseList() {
505 assert(VP.getPointer() && "Null pointer doesn't have a use list!");
507 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
509 if (VP.getPointer()->HasValueHandle) {
510 // If this value already has a ValueHandle, then it must be in the
511 // ValueHandles map already.
512 ValueHandleBase *&Entry = pImpl->ValueHandles[VP.getPointer()];
513 assert(Entry != 0 && "Value doesn't have any handles?");
514 AddToExistingUseList(&Entry);
518 // Ok, it doesn't have any handles yet, so we must insert it into the
519 // DenseMap. However, doing this insertion could cause the DenseMap to
520 // reallocate itself, which would invalidate all of the PrevP pointers that
521 // point into the old table. Handle this by checking for reallocation and
522 // updating the stale pointers only if needed.
523 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
524 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
526 ValueHandleBase *&Entry = Handles[VP.getPointer()];
527 assert(Entry == 0 && "Value really did already have handles?");
528 AddToExistingUseList(&Entry);
529 VP.getPointer()->HasValueHandle = true;
531 // If reallocation didn't happen or if this was the first insertion, don't
533 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
534 Handles.size() == 1) {
538 // Okay, reallocation did happen. Fix the Prev Pointers.
539 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
540 E = Handles.end(); I != E; ++I) {
541 assert(I->second && I->first == I->second->VP.getPointer() &&
542 "List invariant broken!");
543 I->second->setPrevPtr(&I->second);
547 /// RemoveFromUseList - Remove this ValueHandle from its current use list.
548 void ValueHandleBase::RemoveFromUseList() {
549 assert(VP.getPointer() && VP.getPointer()->HasValueHandle &&
550 "Pointer doesn't have a use list!");
552 // Unlink this from its use list.
553 ValueHandleBase **PrevPtr = getPrevPtr();
554 assert(*PrevPtr == this && "List invariant broken");
558 assert(Next->getPrevPtr() == &Next && "List invariant broken");
559 Next->setPrevPtr(PrevPtr);
563 // If the Next pointer was null, then it is possible that this was the last
564 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
566 LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
567 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
568 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
569 Handles.erase(VP.getPointer());
570 VP.getPointer()->HasValueHandle = false;
575 void ValueHandleBase::ValueIsDeleted(Value *V) {
576 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
578 // Get the linked list base, which is guaranteed to exist since the
579 // HasValueHandle flag is set.
580 LLVMContextImpl *pImpl = V->getContext().pImpl;
581 ValueHandleBase *Entry = pImpl->ValueHandles[V];
582 assert(Entry && "Value bit set but no entries exist");
584 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
585 // and remove themselves from the list without breaking our iteration. This
586 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
587 // Note that we deliberately do not the support the case when dropping a value
588 // handle results in a new value handle being permanently added to the list
589 // (as might occur in theory for CallbackVH's): the new value handle will not
590 // be processed and the checking code will mete out righteous punishment if
591 // the handle is still present once we have finished processing all the other
592 // value handles (it is fine to momentarily add then remove a value handle).
593 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
594 Iterator.RemoveFromUseList();
595 Iterator.AddToExistingUseListAfter(Entry);
596 assert(Entry->Next == &Iterator && "Loop invariant broken.");
598 switch (Entry->getKind()) {
602 // Mark that this value has been deleted by setting it to an invalid Value
604 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
607 // Weak just goes to null, which will unlink it from the list.
611 // Forward to the subclass's implementation.
612 static_cast<CallbackVH*>(Entry)->deleted();
617 // All callbacks, weak references, and assertingVHs should be dropped by now.
618 if (V->HasValueHandle) {
619 #ifndef NDEBUG // Only in +Asserts mode...
620 dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
622 if (pImpl->ValueHandles[V]->getKind() == Assert)
623 llvm_unreachable("An asserting value handle still pointed to this"
627 llvm_unreachable("All references to V were not removed?");
632 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
633 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
634 assert(Old != New && "Changing value into itself!");
636 // Get the linked list base, which is guaranteed to exist since the
637 // HasValueHandle flag is set.
638 LLVMContextImpl *pImpl = Old->getContext().pImpl;
639 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
641 assert(Entry && "Value bit set but no entries exist");
643 // We use a local ValueHandleBase as an iterator so that
644 // ValueHandles can add and remove themselves from the list without
645 // breaking our iteration. This is not really an AssertingVH; we
646 // just have to give ValueHandleBase some kind.
647 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
648 Iterator.RemoveFromUseList();
649 Iterator.AddToExistingUseListAfter(Entry);
650 assert(Entry->Next == &Iterator && "Loop invariant broken.");
652 switch (Entry->getKind()) {
654 // Asserting handle does not follow RAUW implicitly.
657 // Tracking goes to new value like a WeakVH. Note that this may make it
658 // something incompatible with its templated type. We don't want to have a
659 // virtual (or inline) interface to handle this though, so instead we make
660 // the TrackingVH accessors guarantee that a client never sees this value.
664 // Weak goes to the new value, which will unlink it from Old's list.
665 Entry->operator=(New);
668 // Forward to the subclass's implementation.
669 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
675 // If any new tracking or weak value handles were added while processing the
676 // list, then complain about it now.
677 if (Old->HasValueHandle)
678 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
679 switch (Entry->getKind()) {
682 dbgs() << "After RAUW from " << *Old->getType() << " %"
683 << Old->getName() << " to " << *New->getType() << " %"
684 << New->getName() << "\n";
685 llvm_unreachable("A tracking or weak value handle still pointed to the"
693 // Default implementation for CallbackVH.
694 void CallbackVH::allUsesReplacedWith(Value *) {}
696 void CallbackVH::deleted() {