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 "LLVMContextImpl.h"
15 #include "llvm/Constant.h"
16 #include "llvm/Constants.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/InstrTypes.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Operator.h"
21 #include "llvm/Module.h"
22 #include "llvm/ValueSymbolTable.h"
23 #include "llvm/ADT/SmallString.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/Support/GetElementPtrTypeIterator.h"
26 #include "llvm/Support/ErrorHandling.h"
27 #include "llvm/Support/LeakDetector.h"
28 #include "llvm/Support/ManagedStatic.h"
29 #include "llvm/Support/ValueHandle.h"
30 #include "llvm/ADT/DenseMap.h"
34 //===----------------------------------------------------------------------===//
36 //===----------------------------------------------------------------------===//
38 static inline Type *checkType(Type *Ty) {
39 assert(Ty && "Value defined with a null type: Error!");
40 return const_cast<Type*>(Ty);
43 Value::Value(Type *ty, unsigned scid)
44 : SubclassID(scid), HasValueHandle(0),
45 SubclassOptionalData(0), SubclassData(0), VTy((Type*)checkType(ty)),
47 // FIXME: Why isn't this in the subclass gunk??
48 if (isa<CallInst>(this) || isa<InvokeInst>(this))
49 assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) &&
50 "invalid CallInst type!");
51 else if (!isa<Constant>(this) && !isa<BasicBlock>(this))
52 assert((VTy->isFirstClassType() || VTy->isVoidTy()) &&
53 "Cannot create non-first-class values except for constants!");
57 // Notify all ValueHandles (if present) that this value is going away.
59 ValueHandleBase::ValueIsDeleted(this);
61 #ifndef NDEBUG // Only in -g mode...
62 // Check to make sure that there are no uses of this value that are still
63 // around when the value is destroyed. If there are, then we have a dangling
64 // reference and something is wrong. This code is here to print out what is
65 // still being referenced. The value in question should be printed as
69 dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n";
70 for (use_iterator I = use_begin(), E = use_end(); I != E; ++I)
71 dbgs() << "Use still stuck around after Def is destroyed:"
75 assert(use_empty() && "Uses remain when a value is destroyed!");
77 // If this value is named, destroy the name. This should not be in a symtab
82 // There should be no uses of this object anymore, remove it.
83 LeakDetector::removeGarbageObject(this);
86 /// hasNUses - Return true if this Value has exactly N users.
88 bool Value::hasNUses(unsigned N) const {
89 const_use_iterator UI = use_begin(), E = use_end();
92 if (UI == E) return false; // Too few.
96 /// hasNUsesOrMore - Return true if this value has N users or more. This is
97 /// logically equivalent to getNumUses() >= N.
99 bool Value::hasNUsesOrMore(unsigned N) const {
100 const_use_iterator UI = use_begin(), E = use_end();
103 if (UI == E) return false; // Too few.
108 /// isUsedInBasicBlock - Return true if this value is used in the specified
110 bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
111 // Start by scanning over the instructions looking for a use before we start
112 // the expensive use iteration.
113 unsigned MaxBlockSize = 3;
114 for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
115 if (std::find(I->op_begin(), I->op_end(), this) != I->op_end())
117 if (MaxBlockSize-- == 0) // If the block is larger fall back to use_iterator
121 if (MaxBlockSize != 0) // We scanned the entire block and found no use.
124 for (const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) {
125 const Instruction *User = dyn_cast<Instruction>(*I);
126 if (User && User->getParent() == BB)
133 /// getNumUses - This method computes the number of uses of this Value. This
134 /// is a linear time operation. Use hasOneUse or hasNUses to check for specific
136 unsigned Value::getNumUses() const {
137 return (unsigned)std::distance(use_begin(), use_end());
140 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
142 if (Instruction *I = dyn_cast<Instruction>(V)) {
143 if (BasicBlock *P = I->getParent())
144 if (Function *PP = P->getParent())
145 ST = &PP->getValueSymbolTable();
146 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
147 if (Function *P = BB->getParent())
148 ST = &P->getValueSymbolTable();
149 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
150 if (Module *P = GV->getParent())
151 ST = &P->getValueSymbolTable();
152 } else if (Argument *A = dyn_cast<Argument>(V)) {
153 if (Function *P = A->getParent())
154 ST = &P->getValueSymbolTable();
155 } else if (isa<MDString>(V))
158 assert(isa<Constant>(V) && "Unknown value type!");
159 return true; // no name is setable for this.
164 StringRef Value::getName() const {
165 // Make sure the empty string is still a C string. For historical reasons,
166 // some clients want to call .data() on the result and expect it to be null
168 if (!Name) return StringRef("", 0);
169 return Name->getKey();
172 void Value::setName(const Twine &NewName) {
173 // Fast path for common IRBuilder case of setName("") when there is no name.
174 if (NewName.isTriviallyEmpty() && !hasName())
177 SmallString<256> NameData;
178 StringRef NameRef = NewName.toStringRef(NameData);
180 // Name isn't changing?
181 if (getName() == NameRef)
184 assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
186 // Get the symbol table to update for this object.
187 ValueSymbolTable *ST;
188 if (getSymTab(this, ST))
189 return; // Cannot set a name on this value (e.g. constant).
191 if (!ST) { // No symbol table to update? Just do the change.
192 if (NameRef.empty()) {
193 // Free the name for this value.
202 // NOTE: Could optimize for the case the name is shrinking to not deallocate
205 // Create the new name.
206 Name = ValueName::Create(NameRef.begin(), NameRef.end());
207 Name->setValue(this);
211 // NOTE: Could optimize for the case the name is shrinking to not deallocate
215 ST->removeValueName(Name);
223 // Name is changing to something new.
224 Name = ST->createValueName(NameRef, this);
228 /// takeName - transfer the name from V to this value, setting V's name to
229 /// empty. It is an error to call V->takeName(V).
230 void Value::takeName(Value *V) {
231 ValueSymbolTable *ST = 0;
232 // If this value has a name, drop it.
234 // Get the symtab this is in.
235 if (getSymTab(this, ST)) {
236 // We can't set a name on this value, but we need to clear V's name if
238 if (V->hasName()) V->setName("");
239 return; // Cannot set a name on this value (e.g. constant).
244 ST->removeValueName(Name);
249 // Now we know that this has no name.
251 // If V has no name either, we're done.
252 if (!V->hasName()) return;
254 // Get this's symtab if we didn't before.
256 if (getSymTab(this, ST)) {
259 return; // Cannot set a name on this value (e.g. constant).
263 // Get V's ST, this should always succed, because V has a name.
264 ValueSymbolTable *VST;
265 bool Failure = getSymTab(V, VST);
266 assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
268 // If these values are both in the same symtab, we can do this very fast.
269 // This works even if both values have no symtab yet.
274 Name->setValue(this);
278 // Otherwise, things are slightly more complex. Remove V's name from VST and
279 // then reinsert it into ST.
282 VST->removeValueName(V->Name);
285 Name->setValue(this);
288 ST->reinsertValue(this);
292 void Value::replaceAllUsesWith(Value *New) {
293 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
294 assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!");
295 assert(New->getType() == getType() &&
296 "replaceAllUses of value with new value of different type!");
298 // Notify all ValueHandles (if present) that this value is going away.
300 ValueHandleBase::ValueIsRAUWd(this, New);
302 while (!use_empty()) {
304 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
305 // constant because they are uniqued.
306 if (Constant *C = dyn_cast<Constant>(U.getUser())) {
307 if (!isa<GlobalValue>(C)) {
308 C->replaceUsesOfWithOnConstant(this, New, &U);
316 if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
317 BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
321 // Various metrics for how much to strip off of pointers.
322 enum PointerStripKind {
324 PSK_InBoundsConstantIndices,
328 template <PointerStripKind StripKind>
329 static Value *stripPointerCastsAndOffsets(Value *V) {
330 if (!V->getType()->isPointerTy())
333 // Even though we don't look through PHI nodes, we could be called on an
334 // instruction in an unreachable block, which may be on a cycle.
335 SmallPtrSet<Value *, 4> Visited;
339 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
341 case PSK_ZeroIndices:
342 if (!GEP->hasAllZeroIndices())
345 case PSK_InBoundsConstantIndices:
346 if (!GEP->hasAllConstantIndices())
350 if (!GEP->isInBounds())
354 V = GEP->getPointerOperand();
355 } else if (Operator::getOpcode(V) == Instruction::BitCast) {
356 V = cast<Operator>(V)->getOperand(0);
357 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
358 if (GA->mayBeOverridden())
360 V = GA->getAliasee();
364 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
365 } while (Visited.insert(V));
371 Value *Value::stripPointerCasts() {
372 return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
375 Value *Value::stripInBoundsConstantOffsets() {
376 return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
379 Value *Value::stripInBoundsOffsets() {
380 return stripPointerCastsAndOffsets<PSK_InBounds>(this);
383 /// isDereferenceablePointer - Test if this value is always a pointer to
384 /// allocated and suitably aligned memory for a simple load or store.
385 static bool isDereferenceablePointer(const Value *V,
386 SmallPtrSet<const Value *, 32> &Visited) {
387 // Note that it is not safe to speculate into a malloc'd region because
388 // malloc may return null.
389 // It's also not always safe to follow a bitcast, for example:
390 // bitcast i8* (alloca i8) to i32*
391 // would result in a 4-byte load from a 1-byte alloca. Some cases could
392 // be handled using TargetData to check sizes and alignments though.
394 // These are obviously ok.
395 if (isa<AllocaInst>(V)) return true;
397 // Global variables which can't collapse to null are ok.
398 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
399 return !GV->hasExternalWeakLinkage();
401 // byval arguments are ok.
402 if (const Argument *A = dyn_cast<Argument>(V))
403 return A->hasByValAttr();
405 // For GEPs, determine if the indexing lands within the allocated object.
406 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
407 // Conservatively require that the base pointer be fully dereferenceable.
408 if (!Visited.insert(GEP->getOperand(0)))
410 if (!isDereferenceablePointer(GEP->getOperand(0), Visited))
412 // Check the indices.
413 gep_type_iterator GTI = gep_type_begin(GEP);
414 for (User::const_op_iterator I = GEP->op_begin()+1,
415 E = GEP->op_end(); I != E; ++I) {
418 // Struct indices can't be out of bounds.
419 if (isa<StructType>(Ty))
421 ConstantInt *CI = dyn_cast<ConstantInt>(Index);
424 // Zero is always ok.
427 // Check to see that it's within the bounds of an array.
428 ArrayType *ATy = dyn_cast<ArrayType>(Ty);
431 if (CI->getValue().getActiveBits() > 64)
433 if (CI->getZExtValue() >= ATy->getNumElements())
436 // Indices check out; this is dereferenceable.
440 // If we don't know, assume the worst.
444 /// isDereferenceablePointer - Test if this value is always a pointer to
445 /// allocated and suitably aligned memory for a simple load or store.
446 bool Value::isDereferenceablePointer() const {
447 SmallPtrSet<const Value *, 32> Visited;
448 return ::isDereferenceablePointer(this, Visited);
451 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
452 /// return the value in the PHI node corresponding to PredBB. If not, return
453 /// ourself. This is useful if you want to know the value something has in a
454 /// predecessor block.
455 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
456 const BasicBlock *PredBB) {
457 PHINode *PN = dyn_cast<PHINode>(this);
458 if (PN && PN->getParent() == CurBB)
459 return PN->getIncomingValueForBlock(PredBB);
463 LLVMContext &Value::getContext() const { return VTy->getContext(); }
465 //===----------------------------------------------------------------------===//
466 // ValueHandleBase Class
467 //===----------------------------------------------------------------------===//
469 /// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
470 /// List is known to point into the existing use list.
471 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
472 assert(List && "Handle list is null?");
474 // Splice ourselves into the list.
479 Next->setPrevPtr(&Next);
480 assert(VP == Next->VP && "Added to wrong list?");
484 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
485 assert(List && "Must insert after existing node");
488 setPrevPtr(&List->Next);
491 Next->setPrevPtr(&Next);
494 /// AddToUseList - Add this ValueHandle to the use list for VP.
495 void ValueHandleBase::AddToUseList() {
496 assert(VP && "Null pointer doesn't have a use list!");
498 LLVMContextImpl *pImpl = VP->getContext().pImpl;
500 if (VP->HasValueHandle) {
501 // If this value already has a ValueHandle, then it must be in the
502 // ValueHandles map already.
503 ValueHandleBase *&Entry = pImpl->ValueHandles[VP];
504 assert(Entry != 0 && "Value doesn't have any handles?");
505 AddToExistingUseList(&Entry);
509 // Ok, it doesn't have any handles yet, so we must insert it into the
510 // DenseMap. However, doing this insertion could cause the DenseMap to
511 // reallocate itself, which would invalidate all of the PrevP pointers that
512 // point into the old table. Handle this by checking for reallocation and
513 // updating the stale pointers only if needed.
514 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
515 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
517 ValueHandleBase *&Entry = Handles[VP];
518 assert(Entry == 0 && "Value really did already have handles?");
519 AddToExistingUseList(&Entry);
520 VP->HasValueHandle = true;
522 // If reallocation didn't happen or if this was the first insertion, don't
524 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
525 Handles.size() == 1) {
529 // Okay, reallocation did happen. Fix the Prev Pointers.
530 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
531 E = Handles.end(); I != E; ++I) {
532 assert(I->second && I->first == I->second->VP && "List invariant broken!");
533 I->second->setPrevPtr(&I->second);
537 /// RemoveFromUseList - Remove this ValueHandle from its current use list.
538 void ValueHandleBase::RemoveFromUseList() {
539 assert(VP && VP->HasValueHandle && "Pointer doesn't have a use list!");
541 // Unlink this from its use list.
542 ValueHandleBase **PrevPtr = getPrevPtr();
543 assert(*PrevPtr == this && "List invariant broken");
547 assert(Next->getPrevPtr() == &Next && "List invariant broken");
548 Next->setPrevPtr(PrevPtr);
552 // If the Next pointer was null, then it is possible that this was the last
553 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
555 LLVMContextImpl *pImpl = VP->getContext().pImpl;
556 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
557 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
559 VP->HasValueHandle = false;
564 void ValueHandleBase::ValueIsDeleted(Value *V) {
565 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
567 // Get the linked list base, which is guaranteed to exist since the
568 // HasValueHandle flag is set.
569 LLVMContextImpl *pImpl = V->getContext().pImpl;
570 ValueHandleBase *Entry = pImpl->ValueHandles[V];
571 assert(Entry && "Value bit set but no entries exist");
573 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
574 // and remove themselves from the list without breaking our iteration. This
575 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
576 // Note that we deliberately do not the support the case when dropping a value
577 // handle results in a new value handle being permanently added to the list
578 // (as might occur in theory for CallbackVH's): the new value handle will not
579 // be processed and the checking code will mete out righteous punishment if
580 // the handle is still present once we have finished processing all the other
581 // value handles (it is fine to momentarily add then remove a value handle).
582 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
583 Iterator.RemoveFromUseList();
584 Iterator.AddToExistingUseListAfter(Entry);
585 assert(Entry->Next == &Iterator && "Loop invariant broken.");
587 switch (Entry->getKind()) {
591 // Mark that this value has been deleted by setting it to an invalid Value
593 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
596 // Weak just goes to null, which will unlink it from the list.
600 // Forward to the subclass's implementation.
601 static_cast<CallbackVH*>(Entry)->deleted();
606 // All callbacks, weak references, and assertingVHs should be dropped by now.
607 if (V->HasValueHandle) {
608 #ifndef NDEBUG // Only in +Asserts mode...
609 dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
611 if (pImpl->ValueHandles[V]->getKind() == Assert)
612 llvm_unreachable("An asserting value handle still pointed to this"
616 llvm_unreachable("All references to V were not removed?");
621 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
622 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
623 assert(Old != New && "Changing value into itself!");
625 // Get the linked list base, which is guaranteed to exist since the
626 // HasValueHandle flag is set.
627 LLVMContextImpl *pImpl = Old->getContext().pImpl;
628 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
630 assert(Entry && "Value bit set but no entries exist");
632 // We use a local ValueHandleBase as an iterator so that
633 // ValueHandles can add and remove themselves from the list without
634 // breaking our iteration. This is not really an AssertingVH; we
635 // just have to give ValueHandleBase some kind.
636 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
637 Iterator.RemoveFromUseList();
638 Iterator.AddToExistingUseListAfter(Entry);
639 assert(Entry->Next == &Iterator && "Loop invariant broken.");
641 switch (Entry->getKind()) {
643 // Asserting handle does not follow RAUW implicitly.
646 // Tracking goes to new value like a WeakVH. Note that this may make it
647 // something incompatible with its templated type. We don't want to have a
648 // virtual (or inline) interface to handle this though, so instead we make
649 // the TrackingVH accessors guarantee that a client never sees this value.
653 // Weak goes to the new value, which will unlink it from Old's list.
654 Entry->operator=(New);
657 // Forward to the subclass's implementation.
658 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
664 // If any new tracking or weak value handles were added while processing the
665 // list, then complain about it now.
666 if (Old->HasValueHandle)
667 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
668 switch (Entry->getKind()) {
671 dbgs() << "After RAUW from " << *Old->getType() << " %"
672 << Old->getName() << " to " << *New->getType() << " %"
673 << New->getName() << "\n";
674 llvm_unreachable("A tracking or weak value handle still pointed to the"
682 /// ~CallbackVH. Empty, but defined here to avoid emitting the vtable
684 CallbackVH::~CallbackVH() {}