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+//===- ValueHandle.h - Value Smart Pointer classes --------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the ValueHandle class and its sub-classes.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_VALUEHANDLE_H
+#define LLVM_IR_VALUEHANDLE_H
+
+#include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/IR/Value.h"
+
+namespace llvm {
+class ValueHandleBase;
+template<typename From> struct simplify_type;
+
+// ValueHandleBase** is only 4-byte aligned.
+template<>
+class PointerLikeTypeTraits<ValueHandleBase**> {
+public:
+ static inline void *getAsVoidPointer(ValueHandleBase** P) { return P; }
+ static inline ValueHandleBase **getFromVoidPointer(void *P) {
+ return static_cast<ValueHandleBase**>(P);
+ }
+ enum { NumLowBitsAvailable = 2 };
+};
+
+/// ValueHandleBase - This is the common base class of value handles.
+/// ValueHandle's are smart pointers to Value's that have special behavior when
+/// the value is deleted or ReplaceAllUsesWith'd. See the specific handles
+/// below for details.
+///
+class ValueHandleBase {
+ friend class Value;
+protected:
+ /// HandleBaseKind - This indicates what sub class the handle actually is.
+ /// This is to avoid having a vtable for the light-weight handle pointers. The
+ /// fully general Callback version does have a vtable.
+ enum HandleBaseKind {
+ Assert,
+ Callback,
+ Tracking,
+ Weak
+ };
+
+private:
+ PointerIntPair<ValueHandleBase**, 2, HandleBaseKind> PrevPair;
+ ValueHandleBase *Next;
+
+ // A subclass may want to store some information along with the value
+ // pointer. Allow them to do this by making the value pointer a pointer-int
+ // pair. The 'setValPtrInt' and 'getValPtrInt' methods below give them this
+ // access.
+ PointerIntPair<Value*, 2> VP;
+
+ ValueHandleBase(const ValueHandleBase&) LLVM_DELETED_FUNCTION;
+public:
+ explicit ValueHandleBase(HandleBaseKind Kind)
+ : PrevPair(0, Kind), Next(0), VP(0, 0) {}
+ ValueHandleBase(HandleBaseKind Kind, Value *V)
+ : PrevPair(0, Kind), Next(0), VP(V, 0) {
+ if (isValid(VP.getPointer()))
+ AddToUseList();
+ }
+ ValueHandleBase(HandleBaseKind Kind, const ValueHandleBase &RHS)
+ : PrevPair(0, Kind), Next(0), VP(RHS.VP) {
+ if (isValid(VP.getPointer()))
+ AddToExistingUseList(RHS.getPrevPtr());
+ }
+ ~ValueHandleBase() {
+ if (isValid(VP.getPointer()))
+ RemoveFromUseList();
+ }
+
+ Value *operator=(Value *RHS) {
+ if (VP.getPointer() == RHS) return RHS;
+ if (isValid(VP.getPointer())) RemoveFromUseList();
+ VP.setPointer(RHS);
+ if (isValid(VP.getPointer())) AddToUseList();
+ return RHS;
+ }
+
+ Value *operator=(const ValueHandleBase &RHS) {
+ if (VP.getPointer() == RHS.VP.getPointer()) return RHS.VP.getPointer();
+ if (isValid(VP.getPointer())) RemoveFromUseList();
+ VP.setPointer(RHS.VP.getPointer());
+ if (isValid(VP.getPointer())) AddToExistingUseList(RHS.getPrevPtr());
+ return VP.getPointer();
+ }
+
+ Value *operator->() const { return getValPtr(); }
+ Value &operator*() const { return *getValPtr(); }
+
+protected:
+ Value *getValPtr() const { return VP.getPointer(); }
+
+ void setValPtrInt(unsigned K) { VP.setInt(K); }
+ unsigned getValPtrInt() const { return VP.getInt(); }
+
+ static bool isValid(Value *V) {
+ return V &&
+ V != DenseMapInfo<Value *>::getEmptyKey() &&
+ V != DenseMapInfo<Value *>::getTombstoneKey();
+ }
+
+public:
+ // Callbacks made from Value.
+ static void ValueIsDeleted(Value *V);
+ static void ValueIsRAUWd(Value *Old, Value *New);
+
+private:
+ // Internal implementation details.
+ ValueHandleBase **getPrevPtr() const { return PrevPair.getPointer(); }
+ HandleBaseKind getKind() const { return PrevPair.getInt(); }
+ void setPrevPtr(ValueHandleBase **Ptr) { PrevPair.setPointer(Ptr); }
+
+ /// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
+ /// List is the address of either the head of the list or a Next node within
+ /// the existing use list.
+ void AddToExistingUseList(ValueHandleBase **List);
+
+ /// AddToExistingUseListAfter - Add this ValueHandle to the use list after
+ /// Node.
+ void AddToExistingUseListAfter(ValueHandleBase *Node);
+
+ /// AddToUseList - Add this ValueHandle to the use list for VP.
+ void AddToUseList();
+ /// RemoveFromUseList - Remove this ValueHandle from its current use list.
+ void RemoveFromUseList();
+};
+
+/// WeakVH - This is a value handle that tries hard to point to a Value, even
+/// across RAUW operations, but will null itself out if the value is destroyed.
+/// this is useful for advisory sorts of information, but should not be used as
+/// the key of a map (since the map would have to rearrange itself when the
+/// pointer changes).
+class WeakVH : public ValueHandleBase {
+public:
+ WeakVH() : ValueHandleBase(Weak) {}
+ WeakVH(Value *P) : ValueHandleBase(Weak, P) {}
+ WeakVH(const WeakVH &RHS)
+ : ValueHandleBase(Weak, RHS) {}
+
+ Value *operator=(Value *RHS) {
+ return ValueHandleBase::operator=(RHS);
+ }
+ Value *operator=(const ValueHandleBase &RHS) {
+ return ValueHandleBase::operator=(RHS);
+ }
+
+ operator Value*() const {
+ return getValPtr();
+ }
+};
+
+// Specialize simplify_type to allow WeakVH to participate in
+// dyn_cast, isa, etc.
+template<> struct simplify_type<WeakVH> {
+ typedef Value* SimpleType;
+ static SimpleType getSimplifiedValue(WeakVH &WVH) {
+ return WVH;
+ }
+};
+
+/// AssertingVH - This is a Value Handle that points to a value and asserts out
+/// if the value is destroyed while the handle is still live. This is very
+/// useful for catching dangling pointer bugs and other things which can be
+/// non-obvious. One particularly useful place to use this is as the Key of a
+/// map. Dangling pointer bugs often lead to really subtle bugs that only occur
+/// if another object happens to get allocated to the same address as the old
+/// one. Using an AssertingVH ensures that an assert is triggered as soon as
+/// the bad delete occurs.
+///
+/// Note that an AssertingVH handle does *not* follow values across RAUW
+/// operations. This means that RAUW's need to explicitly update the
+/// AssertingVH's as it moves. This is required because in non-assert mode this
+/// class turns into a trivial wrapper around a pointer.
+template <typename ValueTy>
+class AssertingVH
+#ifndef NDEBUG
+ : public ValueHandleBase
+#endif
+ {
+
+#ifndef NDEBUG
+ ValueTy *getValPtr() const {
+ return static_cast<ValueTy*>(ValueHandleBase::getValPtr());
+ }
+ void setValPtr(ValueTy *P) {
+ ValueHandleBase::operator=(GetAsValue(P));
+ }
+#else
+ ValueTy *ThePtr;
+ ValueTy *getValPtr() const { return ThePtr; }
+ void setValPtr(ValueTy *P) { ThePtr = P; }
+#endif
+
+ // Convert a ValueTy*, which may be const, to the type the base
+ // class expects.
+ static Value *GetAsValue(Value *V) { return V; }
+ static Value *GetAsValue(const Value *V) { return const_cast<Value*>(V); }
+
+public:
+#ifndef NDEBUG
+ AssertingVH() : ValueHandleBase(Assert) {}
+ AssertingVH(ValueTy *P) : ValueHandleBase(Assert, GetAsValue(P)) {}
+ AssertingVH(const AssertingVH &RHS) : ValueHandleBase(Assert, RHS) {}
+#else
+ AssertingVH() : ThePtr(0) {}
+ AssertingVH(ValueTy *P) : ThePtr(P) {}
+#endif
+
+ operator ValueTy*() const {
+ return getValPtr();
+ }
+
+ ValueTy *operator=(ValueTy *RHS) {
+ setValPtr(RHS);
+ return getValPtr();
+ }
+ ValueTy *operator=(const AssertingVH<ValueTy> &RHS) {
+ setValPtr(RHS.getValPtr());
+ return getValPtr();
+ }
+
+ ValueTy *operator->() const { return getValPtr(); }
+ ValueTy &operator*() const { return *getValPtr(); }
+};
+
+// Specialize DenseMapInfo to allow AssertingVH to participate in DenseMap.
+template<typename T>
+struct DenseMapInfo<AssertingVH<T> > {
+ typedef DenseMapInfo<T*> PointerInfo;
+ static inline AssertingVH<T> getEmptyKey() {
+ return AssertingVH<T>(PointerInfo::getEmptyKey());
+ }
+ static inline T* getTombstoneKey() {
+ return AssertingVH<T>(PointerInfo::getTombstoneKey());
+ }
+ static unsigned getHashValue(const AssertingVH<T> &Val) {
+ return PointerInfo::getHashValue(Val);
+ }
+ static bool isEqual(const AssertingVH<T> &LHS, const AssertingVH<T> &RHS) {
+ return LHS == RHS;
+ }
+};
+
+template <typename T>
+struct isPodLike<AssertingVH<T> > {
+#ifdef NDEBUG
+ static const bool value = true;
+#else
+ static const bool value = false;
+#endif
+};
+
+
+/// TrackingVH - This is a value handle that tracks a Value (or Value subclass),
+/// even across RAUW operations.
+///
+/// TrackingVH is designed for situations where a client needs to hold a handle
+/// to a Value (or subclass) across some operations which may move that value,
+/// but should never destroy it or replace it with some unacceptable type.
+///
+/// It is an error to do anything with a TrackingVH whose value has been
+/// destroyed, except to destruct it.
+///
+/// It is an error to attempt to replace a value with one of a type which is
+/// incompatible with any of its outstanding TrackingVHs.
+template<typename ValueTy>
+class TrackingVH : public ValueHandleBase {
+ void CheckValidity() const {
+ Value *VP = ValueHandleBase::getValPtr();
+
+ // Null is always ok.
+ if (!VP) return;
+
+ // Check that this value is valid (i.e., it hasn't been deleted). We
+ // explicitly delay this check until access to avoid requiring clients to be
+ // unnecessarily careful w.r.t. destruction.
+ assert(ValueHandleBase::isValid(VP) && "Tracked Value was deleted!");
+
+ // Check that the value is a member of the correct subclass. We would like
+ // to check this property on assignment for better debugging, but we don't
+ // want to require a virtual interface on this VH. Instead we allow RAUW to
+ // replace this value with a value of an invalid type, and check it here.
+ assert(isa<ValueTy>(VP) &&
+ "Tracked Value was replaced by one with an invalid type!");
+ }
+
+ ValueTy *getValPtr() const {
+ CheckValidity();
+ return (ValueTy*)ValueHandleBase::getValPtr();
+ }
+ void setValPtr(ValueTy *P) {
+ CheckValidity();
+ ValueHandleBase::operator=(GetAsValue(P));
+ }
+
+ // Convert a ValueTy*, which may be const, to the type the base
+ // class expects.
+ static Value *GetAsValue(Value *V) { return V; }
+ static Value *GetAsValue(const Value *V) { return const_cast<Value*>(V); }
+
+public:
+ TrackingVH() : ValueHandleBase(Tracking) {}
+ TrackingVH(ValueTy *P) : ValueHandleBase(Tracking, GetAsValue(P)) {}
+ TrackingVH(const TrackingVH &RHS) : ValueHandleBase(Tracking, RHS) {}
+
+ operator ValueTy*() const {
+ return getValPtr();
+ }
+
+ ValueTy *operator=(ValueTy *RHS) {
+ setValPtr(RHS);
+ return getValPtr();
+ }
+ ValueTy *operator=(const TrackingVH<ValueTy> &RHS) {
+ setValPtr(RHS.getValPtr());
+ return getValPtr();
+ }
+
+ ValueTy *operator->() const { return getValPtr(); }
+ ValueTy &operator*() const { return *getValPtr(); }
+};
+
+/// CallbackVH - This is a value handle that allows subclasses to define
+/// callbacks that run when the underlying Value has RAUW called on it or is
+/// destroyed. This class can be used as the key of a map, as long as the user
+/// takes it out of the map before calling setValPtr() (since the map has to
+/// rearrange itself when the pointer changes). Unlike ValueHandleBase, this
+/// class has a vtable and a virtual destructor.
+class CallbackVH : public ValueHandleBase {
+ virtual void anchor();
+protected:
+ CallbackVH(const CallbackVH &RHS)
+ : ValueHandleBase(Callback, RHS) {}
+
+ virtual ~CallbackVH() {}
+
+ void setValPtr(Value *P) {
+ ValueHandleBase::operator=(P);
+ }
+
+public:
+ CallbackVH() : ValueHandleBase(Callback) {}
+ CallbackVH(Value *P) : ValueHandleBase(Callback, P) {}
+
+ operator Value*() const {
+ return getValPtr();
+ }
+
+ /// Called when this->getValPtr() is destroyed, inside ~Value(), so you may
+ /// call any non-virtual Value method on getValPtr(), but no subclass methods.
+ /// If WeakVH were implemented as a CallbackVH, it would use this method to
+ /// call setValPtr(NULL). AssertingVH would use this method to cause an
+ /// assertion failure.
+ ///
+ /// All implementations must remove the reference from this object to the
+ /// Value that's being destroyed.
+ virtual void deleted() { setValPtr(NULL); }
+
+ /// Called when this->getValPtr()->replaceAllUsesWith(new_value) is called,
+ /// _before_ any of the uses have actually been replaced. If WeakVH were
+ /// implemented as a CallbackVH, it would use this method to call
+ /// setValPtr(new_value). AssertingVH would do nothing in this method.
+ virtual void allUsesReplacedWith(Value *) {}
+};
+
+} // End llvm namespace
+
+#endif