+//===- llvm/Support/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_SUPPORT_VALUEHANDLE_H
+#define LLVM_SUPPORT_VALUEHANDLE_H
+
+#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/Value.h"
+
+namespace llvm {
+
+/// 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 base class the handle actually is.
+ /// This is to avoid having a vtable for the light-weight handle pointers. The
+ /// fully generally Callback version does have a vtable.
+ enum HandleBaseKind {
+ Assert,
+ Weak,
+ Callback
+ };
+private:
+
+ PointerIntPair<ValueHandleBase**, 2, HandleBaseKind> PrevPair;
+ ValueHandleBase *Next;
+ Value *VP;
+public:
+ ValueHandleBase(HandleBaseKind Kind) : PrevPair(0, Kind), Next(0), VP(0) {}
+ ValueHandleBase(HandleBaseKind Kind, Value *V)
+ : PrevPair(0, Kind), Next(0), VP(V) {
+ if (V)
+ AddToUseList();
+ }
+ ValueHandleBase(HandleBaseKind Kind, const ValueHandleBase &RHS)
+ : PrevPair(0, Kind), Next(0), VP(RHS.VP) {
+ if (VP)
+ AddToExistingUseList(RHS.getPrevPtr());
+ }
+ ~ValueHandleBase() {
+ if (VP)
+ RemoveFromUseList();
+ }
+
+ Value *operator=(Value *RHS) {
+ if (VP == RHS) return RHS;
+ if (VP) RemoveFromUseList();
+ VP = RHS;
+ if (VP) AddToUseList();
+ return RHS;
+ }
+
+ Value *operator=(const ValueHandleBase &RHS) {
+ if (VP == RHS.VP) return RHS.VP;
+ if (VP) RemoveFromUseList();
+ VP = RHS.VP;
+ if (VP) AddToExistingUseList(RHS.getPrevPtr());
+ return VP;
+ }
+
+ Value *operator->() const { return getValPtr(); }
+ Value &operator*() const { return *getValPtr(); }
+
+ bool operator==(const Value *RHS) const { return VP == RHS; }
+ bool operator==(const ValueHandleBase &RHS) const { return VP == RHS.VP; }
+ bool operator!=(const Value *RHS) const { return VP != RHS; }
+ bool operator!=(const ValueHandleBase &RHS) const { return VP != RHS.VP; }
+ bool operator<(const Value *RHS) const { return VP < RHS; }
+ bool operator<(const ValueHandleBase &RHS) const { return VP < RHS.VP; }
+ bool operator>(const Value *RHS) const { return VP > RHS; }
+ bool operator>(const ValueHandleBase &RHS) const { return VP > RHS.VP; }
+ bool operator<=(const Value *RHS) const { return VP <= RHS; }
+ bool operator<=(const ValueHandleBase &RHS) const { return VP <= RHS.VP; }
+ bool operator>=(const Value *RHS) const { return VP >= RHS; }
+ bool operator>=(const ValueHandleBase &RHS) const { return VP >= RHS.VP; }
+
+protected:
+ Value *getValPtr() const { return VP; }
+private:
+ // Callbacks made from Value.
+ static void ValueIsDeleted(Value *V);
+ static void ValueIsRAUWd(Value *Old, Value *New);
+
+ // Internal implementation details.
+ ValueHandleBase **getPrevPtr() const { return PrevPair.getPointer(); }
+ HandleBaseKind getKind() const { return PrevPair.getInt(); }
+ void setPrevPtr(ValueHandleBase **Ptr) { PrevPair.setPointer(Ptr); }
+
+ /// AddToUseList - Add this ValueHandle to the use list for VP, where List is
+ /// known to point into the existing use list.
+ void AddToExistingUseList(ValueHandleBase **List);
+
+ /// 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) {}
+
+};
+
+/// 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 = Value>
+class AssertingVH
+#ifndef NDEBUG
+ : public ValueHandleBase
+#endif
+ {
+
+#ifndef NDEBUG
+ ValueTy *getValPtr() const {
+ return static_cast<ValueTy*>(ValueHandleBase::getValPtr());
+ }
+ void setValPtr(ValueTy *P) {
+ ValueHandleBase::operator=(P);
+ }
+#else
+ ValueTy *ThePtr;
+ ValueTy *getValPtr() const { return ThePtr; }
+ void setValPtr(ValueTy *P) { ThePtr = P; }
+#endif
+
+public:
+#ifndef NDEBUG
+ AssertingVH() : ValueHandleBase(Assert) {}
+ AssertingVH(ValueTy *P) : ValueHandleBase(Assert, 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=(AssertingVH<ValueTy> &RHS) {
+ setValPtr(RHS.getValPtr());
+ return getValPtr();
+ }
+
+ ValueTy *operator->() const { return getValPtr(); }
+ ValueTy &operator*() const { return getValPtr(); }
+
+ // Duplicate these from the base class so that they work when assertions are
+ // off.
+ bool operator==(const Value *RHS) const { return getValPtr() == RHS; }
+ bool operator!=(const Value *RHS) const { return getValPtr() != RHS; }
+ bool operator<(const Value *RHS) const { return getValPtr() < RHS; }
+ bool operator>(const Value *RHS) const { return getValPtr() > RHS; }
+ bool operator<=(const Value *RHS) const { return getValPtr() <= RHS; }
+ bool operator>=(const Value *RHS) const { return getValPtr() >= RHS; }
+ bool operator==(const AssertingVH &RHS) const {
+ return getValPtr() == RHS.getValPtr();
+ }
+ bool operator!=(const AssertingVH &RHS) const {
+ return getValPtr() != RHS.getValPtr();
+ }
+ bool operator<(const AssertingVH &RHS) const {
+ return getValPtr() < RHS.getValPtr();
+ }
+ bool operator>(const AssertingVH &RHS) const {
+ return getValPtr() > RHS.getValPtr();
+ }
+ bool operator<=(const AssertingVH &RHS) const {
+ return getValPtr() <= RHS.getValPtr();
+ }
+ bool operator>=(const AssertingVH &RHS) const {
+ return getValPtr() >= RHS.getValPtr();
+ }
+};
+
+} // End llvm namespace
+
+#endif