260 lines
8.6 KiB
C++
260 lines
8.6 KiB
C++
//===- llvm/ADT/PointerUnion.h - Discriminated Union of 2 Ptrs --*- 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 defines the PointerUnion class, which is a discriminated union of
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// pointer types.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_POINTERUNION_H
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#define LLVM_ADT_POINTERUNION_H
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#include "llvm/ADT/PointerIntPair.h"
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namespace llvm {
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/// getPointerUnionTypeNum - If the argument has type PT1* or PT2* return
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/// false or true respectively.
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template <typename PT1, typename PT2>
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static inline int getPointerUnionTypeNum(PT1 *P) { return 0; }
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template <typename PT1, typename PT2>
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static inline int getPointerUnionTypeNum(PT2 *P) { return 1; }
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template <typename PT1, typename PT2>
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static inline int getPointerUnionTypeNum(...) { return -1; }
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/// Provide PointerLikeTypeTraits for void* that is used by PointerUnion
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/// for the two template arguments.
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template <typename PT1, typename PT2>
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class PointerUnionUIntTraits {
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public:
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static inline void *getAsVoidPointer(void *P) { return P; }
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static inline void *getFromVoidPointer(void *P) { return P; }
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enum {
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PT1BitsAv = PointerLikeTypeTraits<PT1>::NumLowBitsAvailable,
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PT2BitsAv = PointerLikeTypeTraits<PT2>::NumLowBitsAvailable,
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NumLowBitsAvailable = PT1BitsAv < PT2BitsAv ? PT1BitsAv : PT2BitsAv
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};
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};
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/// PointerUnion - This implements a discriminated union of two pointer types,
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/// and keeps the discriminator bit-mangled into the low bits of the pointer.
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/// This allows the implementation to be extremely efficient in space, but
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/// permits a very natural and type-safe API.
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///
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/// Common use patterns would be something like this:
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/// PointerUnion<int*, float*> P;
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/// P = (int*)0;
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/// printf("%d %d", P.is<int*>(), P.is<float*>()); // prints "1 0"
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/// X = P.get<int*>(); // ok.
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/// Y = P.get<float*>(); // runtime assertion failure.
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/// Z = P.get<double*>(); // runtime assertion failure (regardless of tag)
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/// P = (float*)0;
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/// Y = P.get<float*>(); // ok.
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/// X = P.get<int*>(); // runtime assertion failure.
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template <typename PT1, typename PT2>
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class PointerUnion {
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public:
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typedef PointerIntPair<void*, 1, bool,
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PointerUnionUIntTraits<PT1,PT2> > ValTy;
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private:
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ValTy Val;
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public:
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PointerUnion() {}
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PointerUnion(PT1 V) {
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Val.setPointer(
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const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(V)));
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Val.setInt(0);
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}
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PointerUnion(PT2 V) {
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Val.setPointer(
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const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(V)));
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Val.setInt(1);
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}
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/// isNull - Return true if the pointer help in the union is null,
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/// regardless of which type it is.
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bool isNull() const { return Val.getPointer() == 0; }
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operator bool() const { return !isNull(); }
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/// is<T>() return true if the Union currently holds the type matching T.
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template<typename T>
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int is() const {
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int TyNo = ::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0);
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assert(TyNo != -1 && "Type query could never succeed on PointerUnion!");
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return Val.getInt() == TyNo;
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}
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/// get<T>() - Return the value of the specified pointer type. If the
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/// specified pointer type is incorrect, assert.
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template<typename T>
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T get() const {
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assert(is<T>() && "Invalid accessor called");
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return PointerLikeTypeTraits<T>::getFromVoidPointer(Val.getPointer());
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}
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/// dyn_cast<T>() - If the current value is of the specified pointer type,
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/// return it, otherwise return null.
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template<typename T>
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T dyn_cast() const {
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if (is<T>()) return get<T>();
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return T();
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}
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/// Assignment operators - Allow assigning into this union from either
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/// pointer type, setting the discriminator to remember what it came from.
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const PointerUnion &operator=(const PT1 &RHS) {
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Val.setPointer(
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const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(RHS)));
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Val.setInt(0);
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return *this;
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}
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const PointerUnion &operator=(const PT2 &RHS) {
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Val.setPointer(
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const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(RHS)));
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Val.setInt(1);
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return *this;
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}
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void *getOpaqueValue() const { return Val.getOpaqueValue(); }
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static PointerUnion getFromOpaqueValue(void *VP) {
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PointerUnion V;
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V.Val = ValTy::getFromOpaqueValue(VP);
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return V;
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}
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};
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// Teach SmallPtrSet that PointerUnion is "basically a pointer", that has
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// # low bits available = min(PT1bits,PT2bits)-1.
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template<typename PT1, typename PT2>
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class PointerLikeTypeTraits<PointerUnion<PT1, PT2> > {
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public:
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static inline void *
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getAsVoidPointer(const PointerUnion<PT1, PT2> &P) {
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return P.getOpaqueValue();
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}
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static inline PointerUnion<PT1, PT2>
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getFromVoidPointer(void *P) {
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return PointerUnion<PT1, PT2>::getFromOpaqueValue(P);
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}
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// The number of bits available are the min of the two pointer types.
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enum {
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NumLowBitsAvailable =
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PointerLikeTypeTraits<typename PointerUnion<PT1,PT2>::ValTy>
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::NumLowBitsAvailable
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};
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};
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/// PointerUnion3 - This is a pointer union of three pointer types. See
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/// documentation for PointerUnion for usage.
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template <typename PT1, typename PT2, typename PT3>
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class PointerUnion3 {
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public:
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typedef PointerUnion<PT1, PT2> InnerUnion;
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typedef PointerUnion<InnerUnion, PT3> ValTy;
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private:
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ValTy Val;
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public:
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PointerUnion3() {}
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PointerUnion3(PT1 V) {
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Val = InnerUnion(V);
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}
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PointerUnion3(PT2 V) {
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Val = InnerUnion(V);
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}
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PointerUnion3(PT3 V) {
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Val = V;
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}
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/// isNull - Return true if the pointer help in the union is null,
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/// regardless of which type it is.
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bool isNull() const { return Val.isNull(); }
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operator bool() const { return !isNull(); }
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/// is<T>() return true if the Union currently holds the type matching T.
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template<typename T>
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int is() const {
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// Is it PT1/PT2?
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if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
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return Val.is<InnerUnion>() && Val.get<InnerUnion>().is<T>();
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return Val.is<T>();
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}
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/// get<T>() - Return the value of the specified pointer type. If the
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/// specified pointer type is incorrect, assert.
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template<typename T>
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T get() const {
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assert(is<T>() && "Invalid accessor called");
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// Is it PT1/PT2?
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if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
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return Val.get<InnerUnion>().get<T>();
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return Val.get<T>();
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}
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/// dyn_cast<T>() - If the current value is of the specified pointer type,
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/// return it, otherwise return null.
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template<typename T>
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T dyn_cast() const {
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if (is<T>()) return get<T>();
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return T();
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}
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/// Assignment operators - Allow assigning into this union from either
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/// pointer type, setting the discriminator to remember what it came from.
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const PointerUnion3 &operator=(const PT1 &RHS) {
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Val = InnerUnion(RHS);
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return *this;
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}
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const PointerUnion3 &operator=(const PT2 &RHS) {
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Val = InnerUnion(RHS);
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return *this;
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}
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const PointerUnion3 &operator=(const PT3 &RHS) {
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Val = RHS;
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return *this;
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}
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void *getOpaqueValue() const { return Val.getOpaqueValue(); }
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static PointerUnion3 getFromOpaqueValue(void *VP) {
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PointerUnion3 V;
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V.Val = ValTy::getFromOpaqueValue(VP);
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return V;
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}
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};
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// Teach SmallPtrSet that PointerUnion3 is "basically a pointer", that has
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// # low bits available = min(PT1bits,PT2bits,PT2bits)-2.
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template<typename PT1, typename PT2, typename PT3>
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class PointerLikeTypeTraits<PointerUnion3<PT1, PT2, PT3> > {
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public:
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static inline void *
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getAsVoidPointer(const PointerUnion3<PT1, PT2, PT3> &P) {
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return P.getOpaqueValue();
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}
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static inline PointerUnion3<PT1, PT2, PT3>
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getFromVoidPointer(void *P) {
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return PointerUnion3<PT1, PT2, PT3>::getFromOpaqueValue(P);
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}
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// The number of bits available are the min of the two pointer types.
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enum {
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NumLowBitsAvailable =
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PointerLikeTypeTraits<typename PointerUnion3<PT1, PT2, PT3>::ValTy>
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::NumLowBitsAvailable
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};
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};
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}
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#endif
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