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Diffstat (limited to 'lib/IR/Value.cpp')
| -rw-r--r-- | lib/IR/Value.cpp | 698 |
1 files changed, 698 insertions, 0 deletions
diff --git a/lib/IR/Value.cpp b/lib/IR/Value.cpp new file mode 100644 index 0000000000..04ae441513 --- /dev/null +++ b/lib/IR/Value.cpp @@ -0,0 +1,698 @@ +//===-- Value.cpp - Implement the Value class -----------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements the Value, ValueHandle, and User classes. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Value.h" +#include "LLVMContextImpl.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/SmallString.h" +#include "llvm/Constant.h" +#include "llvm/Constants.h" +#include "llvm/DerivedTypes.h" +#include "llvm/InstrTypes.h" +#include "llvm/Instructions.h" +#include "llvm/Module.h" +#include "llvm/Operator.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/GetElementPtrTypeIterator.h" +#include "llvm/Support/LeakDetector.h" +#include "llvm/Support/ManagedStatic.h" +#include "llvm/Support/ValueHandle.h" +#include "llvm/ValueSymbolTable.h" +#include <algorithm> +using namespace llvm; + +//===----------------------------------------------------------------------===// +// Value Class +//===----------------------------------------------------------------------===// + +static inline Type *checkType(Type *Ty) { + assert(Ty && "Value defined with a null type: Error!"); + return const_cast<Type*>(Ty); +} + +Value::Value(Type *ty, unsigned scid) + : SubclassID(scid), HasValueHandle(0), + SubclassOptionalData(0), SubclassData(0), VTy((Type*)checkType(ty)), + UseList(0), Name(0) { + // FIXME: Why isn't this in the subclass gunk?? + // Note, we cannot call isa<CallInst> before the CallInst has been + // constructed. + if (SubclassID == Instruction::Call || SubclassID == Instruction::Invoke) + assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) && + "invalid CallInst type!"); + else if (SubclassID != BasicBlockVal && + (SubclassID < ConstantFirstVal || SubclassID > ConstantLastVal)) + assert((VTy->isFirstClassType() || VTy->isVoidTy()) && + "Cannot create non-first-class values except for constants!"); +} + +Value::~Value() { + // Notify all ValueHandles (if present) that this value is going away. + if (HasValueHandle) + ValueHandleBase::ValueIsDeleted(this); + +#ifndef NDEBUG // Only in -g mode... + // Check to make sure that there are no uses of this value that are still + // around when the value is destroyed. If there are, then we have a dangling + // reference and something is wrong. This code is here to print out what is + // still being referenced. The value in question should be printed as + // a <badref> + // + if (!use_empty()) { + dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n"; + for (use_iterator I = use_begin(), E = use_end(); I != E; ++I) + dbgs() << "Use still stuck around after Def is destroyed:" + << **I << "\n"; + } +#endif + assert(use_empty() && "Uses remain when a value is destroyed!"); + + // If this value is named, destroy the name. This should not be in a symtab + // at this point. + if (Name && SubclassID != MDStringVal) + Name->Destroy(); + + // There should be no uses of this object anymore, remove it. + LeakDetector::removeGarbageObject(this); +} + +/// hasNUses - Return true if this Value has exactly N users. +/// +bool Value::hasNUses(unsigned N) const { + const_use_iterator UI = use_begin(), E = use_end(); + + for (; N; --N, ++UI) + if (UI == E) return false; // Too few. + return UI == E; +} + +/// hasNUsesOrMore - Return true if this value has N users or more. This is +/// logically equivalent to getNumUses() >= N. +/// +bool Value::hasNUsesOrMore(unsigned N) const { + const_use_iterator UI = use_begin(), E = use_end(); + + for (; N; --N, ++UI) + if (UI == E) return false; // Too few. + + return true; +} + +/// isUsedInBasicBlock - Return true if this value is used in the specified +/// basic block. +bool Value::isUsedInBasicBlock(const BasicBlock *BB) const { + // Start by scanning over the instructions looking for a use before we start + // the expensive use iteration. + unsigned MaxBlockSize = 3; + for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) { + if (std::find(I->op_begin(), I->op_end(), this) != I->op_end()) + return true; + if (MaxBlockSize-- == 0) // If the block is larger fall back to use_iterator + break; + } + + if (MaxBlockSize != 0) // We scanned the entire block and found no use. + return false; + + for (const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) { + const Instruction *User = dyn_cast<Instruction>(*I); + if (User && User->getParent() == BB) + return true; + } + return false; +} + + +/// getNumUses - This method computes the number of uses of this Value. This +/// is a linear time operation. Use hasOneUse or hasNUses to check for specific +/// values. +unsigned Value::getNumUses() const { + return (unsigned)std::distance(use_begin(), use_end()); +} + +static bool getSymTab(Value *V, ValueSymbolTable *&ST) { + ST = 0; + if (Instruction *I = dyn_cast<Instruction>(V)) { + if (BasicBlock *P = I->getParent()) + if (Function *PP = P->getParent()) + ST = &PP->getValueSymbolTable(); + } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) { + if (Function *P = BB->getParent()) + ST = &P->getValueSymbolTable(); + } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) { + if (Module *P = GV->getParent()) + ST = &P->getValueSymbolTable(); + } else if (Argument *A = dyn_cast<Argument>(V)) { + if (Function *P = A->getParent()) + ST = &P->getValueSymbolTable(); + } else if (isa<MDString>(V)) + return true; + else { + assert(isa<Constant>(V) && "Unknown value type!"); + return true; // no name is setable for this. + } + return false; +} + +StringRef Value::getName() const { + // Make sure the empty string is still a C string. For historical reasons, + // some clients want to call .data() on the result and expect it to be null + // terminated. + if (!Name) return StringRef("", 0); + return Name->getKey(); +} + +void Value::setName(const Twine &NewName) { + assert(SubclassID != MDStringVal && + "Cannot set the name of MDString with this method!"); + + // Fast path for common IRBuilder case of setName("") when there is no name. + if (NewName.isTriviallyEmpty() && !hasName()) + return; + + SmallString<256> NameData; + StringRef NameRef = NewName.toStringRef(NameData); + + // Name isn't changing? + if (getName() == NameRef) + return; + + assert(!getType()->isVoidTy() && "Cannot assign a name to void values!"); + + // Get the symbol table to update for this object. + ValueSymbolTable *ST; + if (getSymTab(this, ST)) + return; // Cannot set a name on this value (e.g. constant). + + if (!ST) { // No symbol table to update? Just do the change. + if (NameRef.empty()) { + // Free the name for this value. + Name->Destroy(); + Name = 0; + return; + } + + if (Name) + Name->Destroy(); + + // NOTE: Could optimize for the case the name is shrinking to not deallocate + // then reallocated. + + // Create the new name. + Name = ValueName::Create(NameRef.begin(), NameRef.end()); + Name->setValue(this); + return; + } + + // NOTE: Could optimize for the case the name is shrinking to not deallocate + // then reallocated. + if (hasName()) { + // Remove old name. + ST->removeValueName(Name); + Name->Destroy(); + Name = 0; + + if (NameRef.empty()) + return; + } + + // Name is changing to something new. + Name = ST->createValueName(NameRef, this); +} + + +/// takeName - transfer the name from V to this value, setting V's name to +/// empty. It is an error to call V->takeName(V). +void Value::takeName(Value *V) { + assert(SubclassID != MDStringVal && "Cannot take the name of an MDString!"); + + ValueSymbolTable *ST = 0; + // If this value has a name, drop it. + if (hasName()) { + // Get the symtab this is in. + if (getSymTab(this, ST)) { + // We can't set a name on this value, but we need to clear V's name if + // it has one. + if (V->hasName()) V->setName(""); + return; // Cannot set a name on this value (e.g. constant). + } + + // Remove old name. + if (ST) + ST->removeValueName(Name); + Name->Destroy(); + Name = 0; + } + + // Now we know that this has no name. + + // If V has no name either, we're done. + if (!V->hasName()) return; + + // Get this's symtab if we didn't before. + if (!ST) { + if (getSymTab(this, ST)) { + // Clear V's name. + V->setName(""); + return; // Cannot set a name on this value (e.g. constant). + } + } + + // Get V's ST, this should always succed, because V has a name. + ValueSymbolTable *VST; + bool Failure = getSymTab(V, VST); + assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure; + + // If these values are both in the same symtab, we can do this very fast. + // This works even if both values have no symtab yet. + if (ST == VST) { + // Take the name! + Name = V->Name; + V->Name = 0; + Name->setValue(this); + return; + } + + // Otherwise, things are slightly more complex. Remove V's name from VST and + // then reinsert it into ST. + + if (VST) + VST->removeValueName(V->Name); + Name = V->Name; + V->Name = 0; + Name->setValue(this); + + if (ST) + ST->reinsertValue(this); +} + + +void Value::replaceAllUsesWith(Value *New) { + assert(New && "Value::replaceAllUsesWith(<null>) is invalid!"); + assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!"); + assert(New->getType() == getType() && + "replaceAllUses of value with new value of different type!"); + + // Notify all ValueHandles (if present) that this value is going away. + if (HasValueHandle) + ValueHandleBase::ValueIsRAUWd(this, New); + + while (!use_empty()) { + Use &U = *UseList; + // Must handle Constants specially, we cannot call replaceUsesOfWith on a + // constant because they are uniqued. + if (Constant *C = dyn_cast<Constant>(U.getUser())) { + if (!isa<GlobalValue>(C)) { + C->replaceUsesOfWithOnConstant(this, New, &U); + continue; + } + } + + U.set(New); + } + + if (BasicBlock *BB = dyn_cast<BasicBlock>(this)) + BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New)); +} + +namespace { +// Various metrics for how much to strip off of pointers. +enum PointerStripKind { + PSK_ZeroIndices, + PSK_InBoundsConstantIndices, + PSK_InBounds +}; + +template <PointerStripKind StripKind> +static Value *stripPointerCastsAndOffsets(Value *V) { + if (!V->getType()->isPointerTy()) + return V; + + // Even though we don't look through PHI nodes, we could be called on an + // instruction in an unreachable block, which may be on a cycle. + SmallPtrSet<Value *, 4> Visited; + + Visited.insert(V); + do { + if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { + switch (StripKind) { + case PSK_ZeroIndices: + if (!GEP->hasAllZeroIndices()) + return V; + break; + case PSK_InBoundsConstantIndices: + if (!GEP->hasAllConstantIndices()) + return V; + // fallthrough + case PSK_InBounds: + if (!GEP->isInBounds()) + return V; + break; + } + V = GEP->getPointerOperand(); + } else if (Operator::getOpcode(V) == Instruction::BitCast) { + V = cast<Operator>(V)->getOperand(0); + } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) { + if (GA->mayBeOverridden()) + return V; + V = GA->getAliasee(); + } else { + return V; + } + assert(V->getType()->isPointerTy() && "Unexpected operand type!"); + } while (Visited.insert(V)); + + return V; +} +} // namespace + +Value *Value::stripPointerCasts() { + return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this); +} + +Value *Value::stripInBoundsConstantOffsets() { + return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this); +} + +Value *Value::stripInBoundsOffsets() { + return stripPointerCastsAndOffsets<PSK_InBounds>(this); +} + +/// isDereferenceablePointer - Test if this value is always a pointer to +/// allocated and suitably aligned memory for a simple load or store. +static bool isDereferenceablePointer(const Value *V, + SmallPtrSet<const Value *, 32> &Visited) { + // Note that it is not safe to speculate into a malloc'd region because + // malloc may return null. + // It's also not always safe to follow a bitcast, for example: + // bitcast i8* (alloca i8) to i32* + // would result in a 4-byte load from a 1-byte alloca. Some cases could + // be handled using DataLayout to check sizes and alignments though. + + // These are obviously ok. + if (isa<AllocaInst>(V)) return true; + + // Global variables which can't collapse to null are ok. + if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) + return !GV->hasExternalWeakLinkage(); + + // byval arguments are ok. + if (const Argument *A = dyn_cast<Argument>(V)) + return A->hasByValAttr(); + + // For GEPs, determine if the indexing lands within the allocated object. + if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { + // Conservatively require that the base pointer be fully dereferenceable. + if (!Visited.insert(GEP->getOperand(0))) + return false; + if (!isDereferenceablePointer(GEP->getOperand(0), Visited)) + return false; + // Check the indices. + gep_type_iterator GTI = gep_type_begin(GEP); + for (User::const_op_iterator I = GEP->op_begin()+1, + E = GEP->op_end(); I != E; ++I) { + Value *Index = *I; + Type *Ty = *GTI++; + // Struct indices can't be out of bounds. + if (isa<StructType>(Ty)) + continue; + ConstantInt *CI = dyn_cast<ConstantInt>(Index); + if (!CI) + return false; + // Zero is always ok. + if (CI->isZero()) + continue; + // Check to see that it's within the bounds of an array. + ArrayType *ATy = dyn_cast<ArrayType>(Ty); + if (!ATy) + return false; + if (CI->getValue().getActiveBits() > 64) + return false; + if (CI->getZExtValue() >= ATy->getNumElements()) + return false; + } + // Indices check out; this is dereferenceable. + return true; + } + + // If we don't know, assume the worst. + return false; +} + +/// isDereferenceablePointer - Test if this value is always a pointer to +/// allocated and suitably aligned memory for a simple load or store. +bool Value::isDereferenceablePointer() const { + SmallPtrSet<const Value *, 32> Visited; + return ::isDereferenceablePointer(this, Visited); +} + +/// DoPHITranslation - If this value is a PHI node with CurBB as its parent, +/// return the value in the PHI node corresponding to PredBB. If not, return +/// ourself. This is useful if you want to know the value something has in a +/// predecessor block. +Value *Value::DoPHITranslation(const BasicBlock *CurBB, + const BasicBlock *PredBB) { + PHINode *PN = dyn_cast<PHINode>(this); + if (PN && PN->getParent() == CurBB) + return PN->getIncomingValueForBlock(PredBB); + return this; +} + +LLVMContext &Value::getContext() const { return VTy->getContext(); } + +//===----------------------------------------------------------------------===// +// ValueHandleBase Class +//===----------------------------------------------------------------------===// + +/// AddToExistingUseList - Add this ValueHandle to the use list for VP, where +/// List is known to point into the existing use list. +void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) { + assert(List && "Handle list is null?"); + + // Splice ourselves into the list. + Next = *List; + *List = this; + setPrevPtr(List); + if (Next) { + Next->setPrevPtr(&Next); + assert(VP.getPointer() == Next->VP.getPointer() && "Added to wrong list?"); + } +} + +void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) { + assert(List && "Must insert after existing node"); + + Next = List->Next; + setPrevPtr(&List->Next); + List->Next = this; + if (Next) + Next->setPrevPtr(&Next); +} + +/// AddToUseList - Add this ValueHandle to the use list for VP. +void ValueHandleBase::AddToUseList() { + assert(VP.getPointer() && "Null pointer doesn't have a use list!"); + + LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl; + + if (VP.getPointer()->HasValueHandle) { + // If this value already has a ValueHandle, then it must be in the + // ValueHandles map already. + ValueHandleBase *&Entry = pImpl->ValueHandles[VP.getPointer()]; + assert(Entry != 0 && "Value doesn't have any handles?"); + AddToExistingUseList(&Entry); + return; + } + + // Ok, it doesn't have any handles yet, so we must insert it into the + // DenseMap. However, doing this insertion could cause the DenseMap to + // reallocate itself, which would invalidate all of the PrevP pointers that + // point into the old table. Handle this by checking for reallocation and + // updating the stale pointers only if needed. + DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles; + const void *OldBucketPtr = Handles.getPointerIntoBucketsArray(); + + ValueHandleBase *&Entry = Handles[VP.getPointer()]; + assert(Entry == 0 && "Value really did already have handles?"); + AddToExistingUseList(&Entry); + VP.getPointer()->HasValueHandle = true; + + // If reallocation didn't happen or if this was the first insertion, don't + // walk the table. + if (Handles.isPointerIntoBucketsArray(OldBucketPtr) || + Handles.size() == 1) { + return; + } + + // Okay, reallocation did happen. Fix the Prev Pointers. + for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(), + E = Handles.end(); I != E; ++I) { + assert(I->second && I->first == I->second->VP.getPointer() && + "List invariant broken!"); + I->second->setPrevPtr(&I->second); + } +} + +/// RemoveFromUseList - Remove this ValueHandle from its current use list. +void ValueHandleBase::RemoveFromUseList() { + assert(VP.getPointer() && VP.getPointer()->HasValueHandle && + "Pointer doesn't have a use list!"); + + // Unlink this from its use list. + ValueHandleBase **PrevPtr = getPrevPtr(); + assert(*PrevPtr == this && "List invariant broken"); + + *PrevPtr = Next; + if (Next) { + assert(Next->getPrevPtr() == &Next && "List invariant broken"); + Next->setPrevPtr(PrevPtr); + return; + } + + // If the Next pointer was null, then it is possible that this was the last + // ValueHandle watching VP. If so, delete its entry from the ValueHandles + // map. + LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl; + DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles; + if (Handles.isPointerIntoBucketsArray(PrevPtr)) { + Handles.erase(VP.getPointer()); + VP.getPointer()->HasValueHandle = false; + } +} + + +void ValueHandleBase::ValueIsDeleted(Value *V) { + assert(V->HasValueHandle && "Should only be called if ValueHandles present"); + + // Get the linked list base, which is guaranteed to exist since the + // HasValueHandle flag is set. + LLVMContextImpl *pImpl = V->getContext().pImpl; + ValueHandleBase *Entry = pImpl->ValueHandles[V]; + assert(Entry && "Value bit set but no entries exist"); + + // We use a local ValueHandleBase as an iterator so that ValueHandles can add + // and remove themselves from the list without breaking our iteration. This + // is not really an AssertingVH; we just have to give ValueHandleBase a kind. + // Note that we deliberately do not the support the case when dropping a value + // handle results in a new value handle being permanently added to the list + // (as might occur in theory for CallbackVH's): the new value handle will not + // be processed and the checking code will mete out righteous punishment if + // the handle is still present once we have finished processing all the other + // value handles (it is fine to momentarily add then remove a value handle). + for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) { + Iterator.RemoveFromUseList(); + Iterator.AddToExistingUseListAfter(Entry); + assert(Entry->Next == &Iterator && "Loop invariant broken."); + + switch (Entry->getKind()) { + case Assert: + break; + case Tracking: + // Mark that this value has been deleted by setting it to an invalid Value + // pointer. + Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey()); + break; + case Weak: + // Weak just goes to null, which will unlink it from the list. + Entry->operator=(0); + break; + case Callback: + // Forward to the subclass's implementation. + static_cast<CallbackVH*>(Entry)->deleted(); + break; + } + } + + // All callbacks, weak references, and assertingVHs should be dropped by now. + if (V->HasValueHandle) { +#ifndef NDEBUG // Only in +Asserts mode... + dbgs() << "While deleting: " << *V->getType() << " %" << V->getName() + << "\n"; + if (pImpl->ValueHandles[V]->getKind() == Assert) + llvm_unreachable("An asserting value handle still pointed to this" + " value!"); + +#endif + llvm_unreachable("All references to V were not removed?"); + } +} + + +void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) { + assert(Old->HasValueHandle &&"Should only be called if ValueHandles present"); + assert(Old != New && "Changing value into itself!"); + + // Get the linked list base, which is guaranteed to exist since the + // HasValueHandle flag is set. + LLVMContextImpl *pImpl = Old->getContext().pImpl; + ValueHandleBase *Entry = pImpl->ValueHandles[Old]; + + assert(Entry && "Value bit set but no entries exist"); + + // We use a local ValueHandleBase as an iterator so that + // ValueHandles can add and remove themselves from the list without + // breaking our iteration. This is not really an AssertingVH; we + // just have to give ValueHandleBase some kind. + for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) { + Iterator.RemoveFromUseList(); + Iterator.AddToExistingUseListAfter(Entry); + assert(Entry->Next == &Iterator && "Loop invariant broken."); + + switch (Entry->getKind()) { + case Assert: + // Asserting handle does not follow RAUW implicitly. + break; + case Tracking: + // Tracking goes to new value like a WeakVH. Note that this may make it + // something incompatible with its templated type. We don't want to have a + // virtual (or inline) interface to handle this though, so instead we make + // the TrackingVH accessors guarantee that a client never sees this value. + + // FALLTHROUGH + case Weak: + // Weak goes to the new value, which will unlink it from Old's list. + Entry->operator=(New); + break; + case Callback: + // Forward to the subclass's implementation. + static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New); + break; + } + } + +#ifndef NDEBUG + // If any new tracking or weak value handles were added while processing the + // list, then complain about it now. + if (Old->HasValueHandle) + for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next) + switch (Entry->getKind()) { + case Tracking: + case Weak: + dbgs() << "After RAUW from " << *Old->getType() << " %" + << Old->getName() << " to " << *New->getType() << " %" + << New->getName() << "\n"; + llvm_unreachable("A tracking or weak value handle still pointed to the" + " old value!\n"); + default: + break; + } +#endif +} + +// Default implementation for CallbackVH. +void CallbackVH::allUsesReplacedWith(Value *) {} + +void CallbackVH::deleted() { + setValPtr(NULL); +} |