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 << " %" << getNameStr() << "\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 for (const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) {
112 const Instruction *User = dyn_cast<Instruction>(*I);
113 if (User && User->getParent() == BB)
120 /// getNumUses - This method computes the number of uses of this Value. This
121 /// is a linear time operation. Use hasOneUse or hasNUses to check for specific
123 unsigned Value::getNumUses() const {
124 return (unsigned)std::distance(use_begin(), use_end());
127 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
129 if (Instruction *I = dyn_cast<Instruction>(V)) {
130 if (BasicBlock *P = I->getParent())
131 if (Function *PP = P->getParent())
132 ST = &PP->getValueSymbolTable();
133 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
134 if (Function *P = BB->getParent())
135 ST = &P->getValueSymbolTable();
136 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
137 if (Module *P = GV->getParent())
138 ST = &P->getValueSymbolTable();
139 } else if (Argument *A = dyn_cast<Argument>(V)) {
140 if (Function *P = A->getParent())
141 ST = &P->getValueSymbolTable();
142 } else if (isa<MDString>(V))
145 assert(isa<Constant>(V) && "Unknown value type!");
146 return true; // no name is setable for this.
151 StringRef Value::getName() const {
152 // Make sure the empty string is still a C string. For historical reasons,
153 // some clients want to call .data() on the result and expect it to be null
155 if (!Name) return StringRef("", 0);
156 return Name->getKey();
159 std::string Value::getNameStr() const {
160 return getName().str();
163 void Value::setName(const Twine &NewName) {
164 // Fast path for common IRBuilder case of setName("") when there is no name.
165 if (NewName.isTriviallyEmpty() && !hasName())
168 SmallString<256> NameData;
169 StringRef NameRef = NewName.toStringRef(NameData);
171 // Name isn't changing?
172 if (getName() == NameRef)
175 assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
177 // Get the symbol table to update for this object.
178 ValueSymbolTable *ST;
179 if (getSymTab(this, ST))
180 return; // Cannot set a name on this value (e.g. constant).
182 if (!ST) { // No symbol table to update? Just do the change.
183 if (NameRef.empty()) {
184 // Free the name for this value.
193 // NOTE: Could optimize for the case the name is shrinking to not deallocate
196 // Create the new name.
197 Name = ValueName::Create(NameRef.begin(), NameRef.end());
198 Name->setValue(this);
202 // NOTE: Could optimize for the case the name is shrinking to not deallocate
206 ST->removeValueName(Name);
214 // Name is changing to something new.
215 Name = ST->createValueName(NameRef, this);
219 /// takeName - transfer the name from V to this value, setting V's name to
220 /// empty. It is an error to call V->takeName(V).
221 void Value::takeName(Value *V) {
222 ValueSymbolTable *ST = 0;
223 // If this value has a name, drop it.
225 // Get the symtab this is in.
226 if (getSymTab(this, ST)) {
227 // We can't set a name on this value, but we need to clear V's name if
229 if (V->hasName()) V->setName("");
230 return; // Cannot set a name on this value (e.g. constant).
235 ST->removeValueName(Name);
240 // Now we know that this has no name.
242 // If V has no name either, we're done.
243 if (!V->hasName()) return;
245 // Get this's symtab if we didn't before.
247 if (getSymTab(this, ST)) {
250 return; // Cannot set a name on this value (e.g. constant).
254 // Get V's ST, this should always succed, because V has a name.
255 ValueSymbolTable *VST;
256 bool Failure = getSymTab(V, VST);
257 assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
259 // If these values are both in the same symtab, we can do this very fast.
260 // This works even if both values have no symtab yet.
265 Name->setValue(this);
269 // Otherwise, things are slightly more complex. Remove V's name from VST and
270 // then reinsert it into ST.
273 VST->removeValueName(V->Name);
276 Name->setValue(this);
279 ST->reinsertValue(this);
283 void Value::replaceAllUsesWith(Value *New) {
284 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
285 assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!");
286 assert(New->getType() == getType() &&
287 "replaceAllUses of value with new value of different type!");
289 // Notify all ValueHandles (if present) that this value is going away.
291 ValueHandleBase::ValueIsRAUWd(this, New);
293 while (!use_empty()) {
295 // Must handle Constants specially, we cannot call replaceUsesOfWith on a
296 // constant because they are uniqued.
297 if (Constant *C = dyn_cast<Constant>(U.getUser())) {
298 if (!isa<GlobalValue>(C)) {
299 C->replaceUsesOfWithOnConstant(this, New, &U);
307 if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
308 BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
311 Value *Value::stripPointerCasts() {
312 if (!getType()->isPointerTy())
315 // Even though we don't look through PHI nodes, we could be called on an
316 // instruction in an unreachable block, which may be on a cycle.
317 SmallPtrSet<Value *, 4> Visited;
322 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
323 if (!GEP->hasAllZeroIndices())
325 V = GEP->getPointerOperand();
326 } else if (Operator::getOpcode(V) == Instruction::BitCast) {
327 V = cast<Operator>(V)->getOperand(0);
328 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
329 if (GA->mayBeOverridden())
331 V = GA->getAliasee();
335 assert(V->getType()->isPointerTy() && "Unexpected operand type!");
336 } while (Visited.insert(V));
341 /// isDereferenceablePointer - Test if this value is always a pointer to
342 /// allocated and suitably aligned memory for a simple load or store.
343 bool Value::isDereferenceablePointer() const {
344 // Note that it is not safe to speculate into a malloc'd region because
345 // malloc may return null.
346 // It's also not always safe to follow a bitcast, for example:
347 // bitcast i8* (alloca i8) to i32*
348 // would result in a 4-byte load from a 1-byte alloca. Some cases could
349 // be handled using TargetData to check sizes and alignments though.
351 // These are obviously ok.
352 if (isa<AllocaInst>(this)) return true;
354 // Global variables which can't collapse to null are ok.
355 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
356 return !GV->hasExternalWeakLinkage();
358 // byval arguments are ok.
359 if (const Argument *A = dyn_cast<Argument>(this))
360 return A->hasByValAttr();
362 // For GEPs, determine if the indexing lands within the allocated object.
363 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(this)) {
364 // Conservatively require that the base pointer be fully dereferenceable.
365 if (!GEP->getOperand(0)->isDereferenceablePointer())
367 // Check the indices.
368 gep_type_iterator GTI = gep_type_begin(GEP);
369 for (User::const_op_iterator I = GEP->op_begin()+1,
370 E = GEP->op_end(); I != E; ++I) {
373 // Struct indices can't be out of bounds.
374 if (isa<StructType>(Ty))
376 ConstantInt *CI = dyn_cast<ConstantInt>(Index);
379 // Zero is always ok.
382 // Check to see that it's within the bounds of an array.
383 ArrayType *ATy = dyn_cast<ArrayType>(Ty);
386 if (CI->getValue().getActiveBits() > 64)
388 if (CI->getZExtValue() >= ATy->getNumElements())
391 // Indices check out; this is dereferenceable.
395 // If we don't know, assume the worst.
399 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
400 /// return the value in the PHI node corresponding to PredBB. If not, return
401 /// ourself. This is useful if you want to know the value something has in a
402 /// predecessor block.
403 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
404 const BasicBlock *PredBB) {
405 PHINode *PN = dyn_cast<PHINode>(this);
406 if (PN && PN->getParent() == CurBB)
407 return PN->getIncomingValueForBlock(PredBB);
411 LLVMContext &Value::getContext() const { return VTy->getContext(); }
413 //===----------------------------------------------------------------------===//
414 // ValueHandleBase Class
415 //===----------------------------------------------------------------------===//
417 /// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
418 /// List is known to point into the existing use list.
419 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
420 assert(List && "Handle list is null?");
422 // Splice ourselves into the list.
427 Next->setPrevPtr(&Next);
428 assert(VP == Next->VP && "Added to wrong list?");
432 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
433 assert(List && "Must insert after existing node");
436 setPrevPtr(&List->Next);
439 Next->setPrevPtr(&Next);
442 /// AddToUseList - Add this ValueHandle to the use list for VP.
443 void ValueHandleBase::AddToUseList() {
444 assert(VP && "Null pointer doesn't have a use list!");
446 LLVMContextImpl *pImpl = VP->getContext().pImpl;
448 if (VP->HasValueHandle) {
449 // If this value already has a ValueHandle, then it must be in the
450 // ValueHandles map already.
451 ValueHandleBase *&Entry = pImpl->ValueHandles[VP];
452 assert(Entry != 0 && "Value doesn't have any handles?");
453 AddToExistingUseList(&Entry);
457 // Ok, it doesn't have any handles yet, so we must insert it into the
458 // DenseMap. However, doing this insertion could cause the DenseMap to
459 // reallocate itself, which would invalidate all of the PrevP pointers that
460 // point into the old table. Handle this by checking for reallocation and
461 // updating the stale pointers only if needed.
462 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
463 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
465 ValueHandleBase *&Entry = Handles[VP];
466 assert(Entry == 0 && "Value really did already have handles?");
467 AddToExistingUseList(&Entry);
468 VP->HasValueHandle = true;
470 // If reallocation didn't happen or if this was the first insertion, don't
472 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
473 Handles.size() == 1) {
477 // Okay, reallocation did happen. Fix the Prev Pointers.
478 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
479 E = Handles.end(); I != E; ++I) {
480 assert(I->second && I->first == I->second->VP && "List invariant broken!");
481 I->second->setPrevPtr(&I->second);
485 /// RemoveFromUseList - Remove this ValueHandle from its current use list.
486 void ValueHandleBase::RemoveFromUseList() {
487 assert(VP && VP->HasValueHandle && "Pointer doesn't have a use list!");
489 // Unlink this from its use list.
490 ValueHandleBase **PrevPtr = getPrevPtr();
491 assert(*PrevPtr == this && "List invariant broken");
495 assert(Next->getPrevPtr() == &Next && "List invariant broken");
496 Next->setPrevPtr(PrevPtr);
500 // If the Next pointer was null, then it is possible that this was the last
501 // ValueHandle watching VP. If so, delete its entry from the ValueHandles
503 LLVMContextImpl *pImpl = VP->getContext().pImpl;
504 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
505 if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
507 VP->HasValueHandle = false;
512 void ValueHandleBase::ValueIsDeleted(Value *V) {
513 assert(V->HasValueHandle && "Should only be called if ValueHandles present");
515 // Get the linked list base, which is guaranteed to exist since the
516 // HasValueHandle flag is set.
517 LLVMContextImpl *pImpl = V->getContext().pImpl;
518 ValueHandleBase *Entry = pImpl->ValueHandles[V];
519 assert(Entry && "Value bit set but no entries exist");
521 // We use a local ValueHandleBase as an iterator so that ValueHandles can add
522 // and remove themselves from the list without breaking our iteration. This
523 // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
524 // Note that we deliberately do not the support the case when dropping a value
525 // handle results in a new value handle being permanently added to the list
526 // (as might occur in theory for CallbackVH's): the new value handle will not
527 // be processed and the checking code will mete out righteous punishment if
528 // the handle is still present once we have finished processing all the other
529 // value handles (it is fine to momentarily add then remove a value handle).
530 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
531 Iterator.RemoveFromUseList();
532 Iterator.AddToExistingUseListAfter(Entry);
533 assert(Entry->Next == &Iterator && "Loop invariant broken.");
535 switch (Entry->getKind()) {
539 // Mark that this value has been deleted by setting it to an invalid Value
541 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
544 // Weak just goes to null, which will unlink it from the list.
548 // Forward to the subclass's implementation.
549 static_cast<CallbackVH*>(Entry)->deleted();
554 // All callbacks, weak references, and assertingVHs should be dropped by now.
555 if (V->HasValueHandle) {
556 #ifndef NDEBUG // Only in +Asserts mode...
557 dbgs() << "While deleting: " << *V->getType() << " %" << V->getNameStr()
559 if (pImpl->ValueHandles[V]->getKind() == Assert)
560 llvm_unreachable("An asserting value handle still pointed to this"
564 llvm_unreachable("All references to V were not removed?");
569 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
570 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
571 assert(Old != New && "Changing value into itself!");
573 // Get the linked list base, which is guaranteed to exist since the
574 // HasValueHandle flag is set.
575 LLVMContextImpl *pImpl = Old->getContext().pImpl;
576 ValueHandleBase *Entry = pImpl->ValueHandles[Old];
578 assert(Entry && "Value bit set but no entries exist");
580 // We use a local ValueHandleBase as an iterator so that
581 // ValueHandles can add and remove themselves from the list without
582 // breaking our iteration. This is not really an AssertingVH; we
583 // just have to give ValueHandleBase some kind.
584 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
585 Iterator.RemoveFromUseList();
586 Iterator.AddToExistingUseListAfter(Entry);
587 assert(Entry->Next == &Iterator && "Loop invariant broken.");
589 switch (Entry->getKind()) {
591 // Asserting handle does not follow RAUW implicitly.
594 // Tracking goes to new value like a WeakVH. Note that this may make it
595 // something incompatible with its templated type. We don't want to have a
596 // virtual (or inline) interface to handle this though, so instead we make
597 // the TrackingVH accessors guarantee that a client never sees this value.
601 // Weak goes to the new value, which will unlink it from Old's list.
602 Entry->operator=(New);
605 // Forward to the subclass's implementation.
606 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
612 // If any new tracking or weak value handles were added while processing the
613 // list, then complain about it now.
614 if (Old->HasValueHandle)
615 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
616 switch (Entry->getKind()) {
619 dbgs() << "After RAUW from " << *Old->getType() << " %"
620 << Old->getNameStr() << " to " << *New->getType() << " %"
621 << New->getNameStr() << "\n";
622 llvm_unreachable("A tracking or weak value handle still pointed to the"
630 /// ~CallbackVH. Empty, but defined here to avoid emitting the vtable
632 CallbackVH::~CallbackVH() {}