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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207083 91177308-0d34-0410-b5e6-96231b3b80d8
381 lines
13 KiB
C++
381 lines
13 KiB
C++
//===- ValueHandle.h - Value Smart Pointer classes --------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the ValueHandle class and its sub-classes.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_IR_VALUEHANDLE_H
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#define LLVM_IR_VALUEHANDLE_H
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#include "llvm/ADT/DenseMapInfo.h"
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#include "llvm/ADT/PointerIntPair.h"
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#include "llvm/IR/Value.h"
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namespace llvm {
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class ValueHandleBase;
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template<typename From> struct simplify_type;
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// ValueHandleBase** is only 4-byte aligned.
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template<>
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class PointerLikeTypeTraits<ValueHandleBase**> {
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public:
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static inline void *getAsVoidPointer(ValueHandleBase** P) { return P; }
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static inline ValueHandleBase **getFromVoidPointer(void *P) {
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return static_cast<ValueHandleBase**>(P);
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}
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enum { NumLowBitsAvailable = 2 };
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};
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/// ValueHandleBase - This is the common base class of value handles.
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/// ValueHandle's are smart pointers to Value's that have special behavior when
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/// the value is deleted or ReplaceAllUsesWith'd. See the specific handles
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/// below for details.
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///
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class ValueHandleBase {
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friend class Value;
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protected:
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/// HandleBaseKind - This indicates what sub class the handle actually is.
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/// This is to avoid having a vtable for the light-weight handle pointers. The
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/// fully general Callback version does have a vtable.
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enum HandleBaseKind {
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Assert,
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Callback,
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Tracking,
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Weak
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};
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private:
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PointerIntPair<ValueHandleBase**, 2, HandleBaseKind> PrevPair;
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ValueHandleBase *Next;
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// A subclass may want to store some information along with the value
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// pointer. Allow them to do this by making the value pointer a pointer-int
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// pair. The 'setValPtrInt' and 'getValPtrInt' methods below give them this
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// access.
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PointerIntPair<Value*, 2> VP;
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ValueHandleBase(const ValueHandleBase&) LLVM_DELETED_FUNCTION;
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public:
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explicit ValueHandleBase(HandleBaseKind Kind)
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: PrevPair(nullptr, Kind), Next(nullptr), VP(nullptr, 0) {}
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ValueHandleBase(HandleBaseKind Kind, Value *V)
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: PrevPair(nullptr, Kind), Next(nullptr), VP(V, 0) {
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if (isValid(VP.getPointer()))
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AddToUseList();
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}
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ValueHandleBase(HandleBaseKind Kind, const ValueHandleBase &RHS)
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: PrevPair(nullptr, Kind), Next(nullptr), VP(RHS.VP) {
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if (isValid(VP.getPointer()))
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AddToExistingUseList(RHS.getPrevPtr());
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}
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~ValueHandleBase() {
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if (isValid(VP.getPointer()))
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RemoveFromUseList();
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}
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Value *operator=(Value *RHS) {
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if (VP.getPointer() == RHS) return RHS;
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if (isValid(VP.getPointer())) RemoveFromUseList();
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VP.setPointer(RHS);
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if (isValid(VP.getPointer())) AddToUseList();
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return RHS;
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}
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Value *operator=(const ValueHandleBase &RHS) {
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if (VP.getPointer() == RHS.VP.getPointer()) return RHS.VP.getPointer();
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if (isValid(VP.getPointer())) RemoveFromUseList();
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VP.setPointer(RHS.VP.getPointer());
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if (isValid(VP.getPointer())) AddToExistingUseList(RHS.getPrevPtr());
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return VP.getPointer();
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}
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Value *operator->() const { return getValPtr(); }
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Value &operator*() const { return *getValPtr(); }
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protected:
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Value *getValPtr() const { return VP.getPointer(); }
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void setValPtrInt(unsigned K) { VP.setInt(K); }
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unsigned getValPtrInt() const { return VP.getInt(); }
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static bool isValid(Value *V) {
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return V &&
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V != DenseMapInfo<Value *>::getEmptyKey() &&
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V != DenseMapInfo<Value *>::getTombstoneKey();
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}
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public:
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// Callbacks made from Value.
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static void ValueIsDeleted(Value *V);
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static void ValueIsRAUWd(Value *Old, Value *New);
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private:
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// Internal implementation details.
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ValueHandleBase **getPrevPtr() const { return PrevPair.getPointer(); }
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HandleBaseKind getKind() const { return PrevPair.getInt(); }
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void setPrevPtr(ValueHandleBase **Ptr) { PrevPair.setPointer(Ptr); }
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/// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
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/// List is the address of either the head of the list or a Next node within
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/// the existing use list.
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void AddToExistingUseList(ValueHandleBase **List);
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/// AddToExistingUseListAfter - Add this ValueHandle to the use list after
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/// Node.
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void AddToExistingUseListAfter(ValueHandleBase *Node);
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/// AddToUseList - Add this ValueHandle to the use list for VP.
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void AddToUseList();
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/// RemoveFromUseList - Remove this ValueHandle from its current use list.
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void RemoveFromUseList();
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};
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/// WeakVH - This is a value handle that tries hard to point to a Value, even
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/// across RAUW operations, but will null itself out if the value is destroyed.
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/// this is useful for advisory sorts of information, but should not be used as
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/// the key of a map (since the map would have to rearrange itself when the
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/// pointer changes).
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class WeakVH : public ValueHandleBase {
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public:
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WeakVH() : ValueHandleBase(Weak) {}
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WeakVH(Value *P) : ValueHandleBase(Weak, P) {}
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WeakVH(const WeakVH &RHS)
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: ValueHandleBase(Weak, RHS) {}
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Value *operator=(Value *RHS) {
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return ValueHandleBase::operator=(RHS);
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}
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Value *operator=(const ValueHandleBase &RHS) {
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return ValueHandleBase::operator=(RHS);
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}
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operator Value*() const {
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return getValPtr();
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}
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};
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// Specialize simplify_type to allow WeakVH to participate in
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// dyn_cast, isa, etc.
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template<> struct simplify_type<WeakVH> {
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typedef Value* SimpleType;
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static SimpleType getSimplifiedValue(WeakVH &WVH) {
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return WVH;
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}
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};
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/// AssertingVH - This is a Value Handle that points to a value and asserts out
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/// if the value is destroyed while the handle is still live. This is very
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/// useful for catching dangling pointer bugs and other things which can be
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/// non-obvious. One particularly useful place to use this is as the Key of a
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/// map. Dangling pointer bugs often lead to really subtle bugs that only occur
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/// if another object happens to get allocated to the same address as the old
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/// one. Using an AssertingVH ensures that an assert is triggered as soon as
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/// the bad delete occurs.
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///
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/// Note that an AssertingVH handle does *not* follow values across RAUW
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/// operations. This means that RAUW's need to explicitly update the
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/// AssertingVH's as it moves. This is required because in non-assert mode this
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/// class turns into a trivial wrapper around a pointer.
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template <typename ValueTy>
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class AssertingVH
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#ifndef NDEBUG
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: public ValueHandleBase
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#endif
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{
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#ifndef NDEBUG
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ValueTy *getValPtr() const {
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return static_cast<ValueTy*>(ValueHandleBase::getValPtr());
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}
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void setValPtr(ValueTy *P) {
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ValueHandleBase::operator=(GetAsValue(P));
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}
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#else
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ValueTy *ThePtr;
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ValueTy *getValPtr() const { return ThePtr; }
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void setValPtr(ValueTy *P) { ThePtr = P; }
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#endif
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// Convert a ValueTy*, which may be const, to the type the base
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// class expects.
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static Value *GetAsValue(Value *V) { return V; }
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static Value *GetAsValue(const Value *V) { return const_cast<Value*>(V); }
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public:
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#ifndef NDEBUG
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AssertingVH() : ValueHandleBase(Assert) {}
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AssertingVH(ValueTy *P) : ValueHandleBase(Assert, GetAsValue(P)) {}
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AssertingVH(const AssertingVH &RHS) : ValueHandleBase(Assert, RHS) {}
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#else
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AssertingVH() : ThePtr(nullptr) {}
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AssertingVH(ValueTy *P) : ThePtr(P) {}
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#endif
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operator ValueTy*() const {
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return getValPtr();
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}
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ValueTy *operator=(ValueTy *RHS) {
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setValPtr(RHS);
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return getValPtr();
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}
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ValueTy *operator=(const AssertingVH<ValueTy> &RHS) {
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setValPtr(RHS.getValPtr());
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return getValPtr();
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}
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ValueTy *operator->() const { return getValPtr(); }
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ValueTy &operator*() const { return *getValPtr(); }
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};
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// Specialize DenseMapInfo to allow AssertingVH to participate in DenseMap.
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template<typename T>
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struct DenseMapInfo<AssertingVH<T> > {
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typedef DenseMapInfo<T*> PointerInfo;
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static inline AssertingVH<T> getEmptyKey() {
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return AssertingVH<T>(PointerInfo::getEmptyKey());
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}
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static inline T* getTombstoneKey() {
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return AssertingVH<T>(PointerInfo::getTombstoneKey());
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}
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static unsigned getHashValue(const AssertingVH<T> &Val) {
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return PointerInfo::getHashValue(Val);
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}
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static bool isEqual(const AssertingVH<T> &LHS, const AssertingVH<T> &RHS) {
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return LHS == RHS;
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}
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};
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template <typename T>
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struct isPodLike<AssertingVH<T> > {
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#ifdef NDEBUG
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static const bool value = true;
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#else
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static const bool value = false;
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#endif
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};
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/// TrackingVH - This is a value handle that tracks a Value (or Value subclass),
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/// even across RAUW operations.
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///
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/// TrackingVH is designed for situations where a client needs to hold a handle
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/// to a Value (or subclass) across some operations which may move that value,
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/// but should never destroy it or replace it with some unacceptable type.
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///
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/// It is an error to do anything with a TrackingVH whose value has been
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/// destroyed, except to destruct it.
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///
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/// It is an error to attempt to replace a value with one of a type which is
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/// incompatible with any of its outstanding TrackingVHs.
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template<typename ValueTy>
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class TrackingVH : public ValueHandleBase {
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void CheckValidity() const {
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Value *VP = ValueHandleBase::getValPtr();
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// Null is always ok.
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if (!VP) return;
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// Check that this value is valid (i.e., it hasn't been deleted). We
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// explicitly delay this check until access to avoid requiring clients to be
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// unnecessarily careful w.r.t. destruction.
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assert(ValueHandleBase::isValid(VP) && "Tracked Value was deleted!");
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// Check that the value is a member of the correct subclass. We would like
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// to check this property on assignment for better debugging, but we don't
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// want to require a virtual interface on this VH. Instead we allow RAUW to
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// replace this value with a value of an invalid type, and check it here.
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assert(isa<ValueTy>(VP) &&
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"Tracked Value was replaced by one with an invalid type!");
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}
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ValueTy *getValPtr() const {
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CheckValidity();
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return (ValueTy*)ValueHandleBase::getValPtr();
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}
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void setValPtr(ValueTy *P) {
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CheckValidity();
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ValueHandleBase::operator=(GetAsValue(P));
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}
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// Convert a ValueTy*, which may be const, to the type the base
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// class expects.
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static Value *GetAsValue(Value *V) { return V; }
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static Value *GetAsValue(const Value *V) { return const_cast<Value*>(V); }
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public:
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TrackingVH() : ValueHandleBase(Tracking) {}
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TrackingVH(ValueTy *P) : ValueHandleBase(Tracking, GetAsValue(P)) {}
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TrackingVH(const TrackingVH &RHS) : ValueHandleBase(Tracking, RHS) {}
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operator ValueTy*() const {
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return getValPtr();
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}
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ValueTy *operator=(ValueTy *RHS) {
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setValPtr(RHS);
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return getValPtr();
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}
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ValueTy *operator=(const TrackingVH<ValueTy> &RHS) {
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setValPtr(RHS.getValPtr());
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return getValPtr();
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}
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ValueTy *operator->() const { return getValPtr(); }
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ValueTy &operator*() const { return *getValPtr(); }
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};
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/// CallbackVH - This is a value handle that allows subclasses to define
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/// callbacks that run when the underlying Value has RAUW called on it or is
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/// destroyed. This class can be used as the key of a map, as long as the user
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/// takes it out of the map before calling setValPtr() (since the map has to
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/// rearrange itself when the pointer changes). Unlike ValueHandleBase, this
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/// class has a vtable and a virtual destructor.
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class CallbackVH : public ValueHandleBase {
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virtual void anchor();
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protected:
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CallbackVH(const CallbackVH &RHS)
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: ValueHandleBase(Callback, RHS) {}
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virtual ~CallbackVH() {}
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void setValPtr(Value *P) {
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ValueHandleBase::operator=(P);
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}
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public:
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CallbackVH() : ValueHandleBase(Callback) {}
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CallbackVH(Value *P) : ValueHandleBase(Callback, P) {}
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operator Value*() const {
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return getValPtr();
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}
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/// Called when this->getValPtr() is destroyed, inside ~Value(), so you may
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/// call any non-virtual Value method on getValPtr(), but no subclass methods.
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/// If WeakVH were implemented as a CallbackVH, it would use this method to
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/// call setValPtr(NULL). AssertingVH would use this method to cause an
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/// assertion failure.
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///
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/// All implementations must remove the reference from this object to the
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/// Value that's being destroyed.
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virtual void deleted() { setValPtr(nullptr); }
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/// Called when this->getValPtr()->replaceAllUsesWith(new_value) is called,
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/// _before_ any of the uses have actually been replaced. If WeakVH were
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/// implemented as a CallbackVH, it would use this method to call
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/// setValPtr(new_value). AssertingVH would do nothing in this method.
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virtual void allUsesReplacedWith(Value *) {}
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};
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} // End llvm namespace
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#endif
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