PointerUnion.h revision 38297f5f760de604258aaa9000e5aadb43c78921 
1//===- llvm/ADT/PointerUnion.h - Discriminated Union of 2 Ptrs --*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines the PointerUnion class, which is a discriminated union of
11// pointer types.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_ADT_POINTERUNION_H
16#define LLVM_ADT_POINTERUNION_H
17
18#include "llvm/ADT/PointerIntPair.h"
19
20namespace llvm {
21
22  /// getPointerUnionTypeNum - If the argument has type PT1* or PT2* return
23  /// false or true respectively.
24  template <typename PT1, typename PT2>
25  static inline int getPointerUnionTypeNum(PT1 *P) { return 0; }
26  template <typename PT1, typename PT2>
27  static inline int getPointerUnionTypeNum(PT2 *P) { return 1; }
28  template <typename PT1, typename PT2>
29  static inline int getPointerUnionTypeNum(...) { return -1; }
30
31
32  /// Provide PointerLikeTypeTraits for void* that is used by PointerUnion
33  /// for the two template arguments.
34  template <typename PT1, typename PT2>
35  class PointerUnionUIntTraits {
36  public:
37    static inline void *getAsVoidPointer(void *P) { return P; }
38    static inline void *getFromVoidPointer(void *P) { return P; }
39    enum {
40      PT1BitsAv = PointerLikeTypeTraits<PT1>::NumLowBitsAvailable,
41      PT2BitsAv = PointerLikeTypeTraits<PT2>::NumLowBitsAvailable,
42      NumLowBitsAvailable = PT1BitsAv < PT2BitsAv ? PT1BitsAv : PT2BitsAv
43    };
44  };
45
46  /// PointerUnion - This implements a discriminated union of two pointer types,
47  /// and keeps the discriminator bit-mangled into the low bits of the pointer.
48  /// This allows the implementation to be extremely efficient in space, but
49  /// permits a very natural and type-safe API.
50  ///
51  /// Common use patterns would be something like this:
52  ///    PointerUnion<int*, float*> P;
53  ///    P = (int*)0;
54  ///    printf("%d %d", P.is<int*>(), P.is<float*>());  // prints "1 0"
55  ///    X = P.get<int*>();     // ok.
56  ///    Y = P.get<float*>();   // runtime assertion failure.
57  ///    Z = P.get<double*>();  // runtime assertion failure (regardless of tag)
58  ///    P = (float*)0;
59  ///    Y = P.get<float*>();   // ok.
60  ///    X = P.get<int*>();     // runtime assertion failure.
61  template <typename PT1, typename PT2>
62  class PointerUnion {
63  public:
64    typedef PointerIntPair<void*, 1, bool,
65                           PointerUnionUIntTraits<PT1,PT2> > ValTy;
66  private:
67    ValTy Val;
68  public:
69    PointerUnion() {}
70
71    PointerUnion(PT1 V) {
72      Val.setPointer(
73         const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(V)));
74      Val.setInt(0);
75    }
76    PointerUnion(PT2 V) {
77      Val.setPointer(
78         const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(V)));
79      Val.setInt(1);
80    }
81
82    /// isNull - Return true if the pointer held in the union is null,
83    /// regardless of which type it is.
84    bool isNull() const { return Val.getPointer() == 0; }
85    operator bool() const { return !isNull(); }
86
87    /// is<T>() return true if the Union currently holds the type matching T.
88    template<typename T>
89    int is() const {
90      int TyNo = ::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0);
91      assert(TyNo != -1 && "Type query could never succeed on PointerUnion!");
92      return static_cast<int>(Val.getInt()) == TyNo;
93    }
94
95    /// get<T>() - Return the value of the specified pointer type. If the
96    /// specified pointer type is incorrect, assert.
97    template<typename T>
98    T get() const {
99      assert(is<T>() && "Invalid accessor called");
100      return PointerLikeTypeTraits<T>::getFromVoidPointer(Val.getPointer());
101    }
102
103    /// dyn_cast<T>() - If the current value is of the specified pointer type,
104    /// return it, otherwise return null.
105    template<typename T>
106    T dyn_cast() const {
107      if (is<T>()) return get<T>();
108      return T();
109    }
110
111    /// \brief If the union is set to the first pointer type we can get an
112    /// address pointing to it.
113    template <typename T>
114    PT1 const *getAddrOf() const {
115      assert(is<PT1>() && "Val is not the first pointer");
116      assert(get<PT1>() == Val.getPointer() &&
117         "Can't get the address because PointerLikeTypeTraits changes the ptr");
118      T const *can_only_get_address_of_first_pointer_type
119                        = reinterpret_cast<PT1 const *>(Val.getAddrOfPointer());
120      return can_only_get_address_of_first_pointer_type;
121    }
122
123    /// Assignment operators - Allow assigning into this union from either
124    /// pointer type, setting the discriminator to remember what it came from.
125    const PointerUnion &operator=(const PT1 &RHS) {
126      Val.setPointer(
127         const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(RHS)));
128      Val.setInt(0);
129      return *this;
130    }
131    const PointerUnion &operator=(const PT2 &RHS) {
132      Val.setPointer(
133        const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(RHS)));
134      Val.setInt(1);
135      return *this;
136    }
137
138    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
139    static inline PointerUnion getFromOpaqueValue(void *VP) {
140      PointerUnion V;
141      V.Val = ValTy::getFromOpaqueValue(VP);
142      return V;
143    }
144  };
145
146  // Teach SmallPtrSet that PointerUnion is "basically a pointer", that has
147  // # low bits available = min(PT1bits,PT2bits)-1.
148  template<typename PT1, typename PT2>
149  class PointerLikeTypeTraits<PointerUnion<PT1, PT2> > {
150  public:
151    static inline void *
152    getAsVoidPointer(const PointerUnion<PT1, PT2> &P) {
153      return P.getOpaqueValue();
154    }
155    static inline PointerUnion<PT1, PT2>
156    getFromVoidPointer(void *P) {
157      return PointerUnion<PT1, PT2>::getFromOpaqueValue(P);
158    }
159
160    // The number of bits available are the min of the two pointer types.
161    enum {
162      NumLowBitsAvailable =
163        PointerLikeTypeTraits<typename PointerUnion<PT1,PT2>::ValTy>
164          ::NumLowBitsAvailable
165    };
166  };
167
168
169  /// PointerUnion3 - This is a pointer union of three pointer types.  See
170  /// documentation for PointerUnion for usage.
171  template <typename PT1, typename PT2, typename PT3>
172  class PointerUnion3 {
173  public:
174    typedef PointerUnion<PT1, PT2> InnerUnion;
175    typedef PointerUnion<InnerUnion, PT3> ValTy;
176  private:
177    ValTy Val;
178  public:
179    PointerUnion3() {}
180
181    PointerUnion3(PT1 V) {
182      Val = InnerUnion(V);
183    }
184    PointerUnion3(PT2 V) {
185      Val = InnerUnion(V);
186    }
187    PointerUnion3(PT3 V) {
188      Val = V;
189    }
190
191    /// isNull - Return true if the pointer held in the union is null,
192    /// regardless of which type it is.
193    bool isNull() const { return Val.isNull(); }
194    operator bool() const { return !isNull(); }
195
196    /// is<T>() return true if the Union currently holds the type matching T.
197    template<typename T>
198    int is() const {
199      // Is it PT1/PT2?
200      if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
201        return Val.template is<InnerUnion>() &&
202               Val.template get<InnerUnion>().template is<T>();
203      return Val.template is<T>();
204    }
205
206    /// get<T>() - Return the value of the specified pointer type. If the
207    /// specified pointer type is incorrect, assert.
208    template<typename T>
209    T get() const {
210      assert(is<T>() && "Invalid accessor called");
211      // Is it PT1/PT2?
212      if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
213        return Val.template get<InnerUnion>().template get<T>();
214
215      return Val.template get<T>();
216    }
217
218    /// dyn_cast<T>() - If the current value is of the specified pointer type,
219    /// return it, otherwise return null.
220    template<typename T>
221    T dyn_cast() const {
222      if (is<T>()) return get<T>();
223      return T();
224    }
225
226    /// Assignment operators - Allow assigning into this union from either
227    /// pointer type, setting the discriminator to remember what it came from.
228    const PointerUnion3 &operator=(const PT1 &RHS) {
229      Val = InnerUnion(RHS);
230      return *this;
231    }
232    const PointerUnion3 &operator=(const PT2 &RHS) {
233      Val = InnerUnion(RHS);
234      return *this;
235    }
236    const PointerUnion3 &operator=(const PT3 &RHS) {
237      Val = RHS;
238      return *this;
239    }
240
241    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
242    static inline PointerUnion3 getFromOpaqueValue(void *VP) {
243      PointerUnion3 V;
244      V.Val = ValTy::getFromOpaqueValue(VP);
245      return V;
246    }
247  };
248
249  // Teach SmallPtrSet that PointerUnion3 is "basically a pointer", that has
250  // # low bits available = min(PT1bits,PT2bits,PT2bits)-2.
251  template<typename PT1, typename PT2, typename PT3>
252  class PointerLikeTypeTraits<PointerUnion3<PT1, PT2, PT3> > {
253  public:
254    static inline void *
255    getAsVoidPointer(const PointerUnion3<PT1, PT2, PT3> &P) {
256      return P.getOpaqueValue();
257    }
258    static inline PointerUnion3<PT1, PT2, PT3>
259    getFromVoidPointer(void *P) {
260      return PointerUnion3<PT1, PT2, PT3>::getFromOpaqueValue(P);
261    }
262
263    // The number of bits available are the min of the two pointer types.
264    enum {
265      NumLowBitsAvailable =
266        PointerLikeTypeTraits<typename PointerUnion3<PT1, PT2, PT3>::ValTy>
267          ::NumLowBitsAvailable
268    };
269  };
270
271  /// PointerUnion4 - This is a pointer union of four pointer types.  See
272  /// documentation for PointerUnion for usage.
273  template <typename PT1, typename PT2, typename PT3, typename PT4>
274  class PointerUnion4 {
275  public:
276    typedef PointerUnion<PT1, PT2> InnerUnion1;
277    typedef PointerUnion<PT3, PT4> InnerUnion2;
278    typedef PointerUnion<InnerUnion1, InnerUnion2> ValTy;
279  private:
280    ValTy Val;
281  public:
282    PointerUnion4() {}
283
284    PointerUnion4(PT1 V) {
285      Val = InnerUnion1(V);
286    }
287    PointerUnion4(PT2 V) {
288      Val = InnerUnion1(V);
289    }
290    PointerUnion4(PT3 V) {
291      Val = InnerUnion2(V);
292    }
293    PointerUnion4(PT4 V) {
294      Val = InnerUnion2(V);
295    }
296
297    /// isNull - Return true if the pointer held in the union is null,
298    /// regardless of which type it is.
299    bool isNull() const { return Val.isNull(); }
300    operator bool() const { return !isNull(); }
301
302    /// is<T>() return true if the Union currently holds the type matching T.
303    template<typename T>
304    int is() const {
305      // Is it PT1/PT2?
306      if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
307        return Val.template is<InnerUnion1>() &&
308               Val.template get<InnerUnion1>().template is<T>();
309      return Val.template is<InnerUnion2>() &&
310             Val.template get<InnerUnion2>().template is<T>();
311    }
312
313    /// get<T>() - Return the value of the specified pointer type. If the
314    /// specified pointer type is incorrect, assert.
315    template<typename T>
316    T get() const {
317      assert(is<T>() && "Invalid accessor called");
318      // Is it PT1/PT2?
319      if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
320        return Val.template get<InnerUnion1>().template get<T>();
321
322      return Val.template get<InnerUnion2>().template get<T>();
323    }
324
325    /// dyn_cast<T>() - If the current value is of the specified pointer type,
326    /// return it, otherwise return null.
327    template<typename T>
328    T dyn_cast() const {
329      if (is<T>()) return get<T>();
330      return T();
331    }
332
333    /// Assignment operators - Allow assigning into this union from either
334    /// pointer type, setting the discriminator to remember what it came from.
335    const PointerUnion4 &operator=(const PT1 &RHS) {
336      Val = InnerUnion1(RHS);
337      return *this;
338    }
339    const PointerUnion4 &operator=(const PT2 &RHS) {
340      Val = InnerUnion1(RHS);
341      return *this;
342    }
343    const PointerUnion4 &operator=(const PT3 &RHS) {
344      Val = InnerUnion2(RHS);
345      return *this;
346    }
347    const PointerUnion4 &operator=(const PT4 &RHS) {
348      Val = InnerUnion2(RHS);
349      return *this;
350    }
351
352    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
353    static inline PointerUnion4 getFromOpaqueValue(void *VP) {
354      PointerUnion4 V;
355      V.Val = ValTy::getFromOpaqueValue(VP);
356      return V;
357    }
358  };
359
360  // Teach SmallPtrSet that PointerUnion4 is "basically a pointer", that has
361  // # low bits available = min(PT1bits,PT2bits,PT2bits)-2.
362  template<typename PT1, typename PT2, typename PT3, typename PT4>
363  class PointerLikeTypeTraits<PointerUnion4<PT1, PT2, PT3, PT4> > {
364  public:
365    static inline void *
366    getAsVoidPointer(const PointerUnion4<PT1, PT2, PT3, PT4> &P) {
367      return P.getOpaqueValue();
368    }
369    static inline PointerUnion4<PT1, PT2, PT3, PT4>
370    getFromVoidPointer(void *P) {
371      return PointerUnion4<PT1, PT2, PT3, PT4>::getFromOpaqueValue(P);
372    }
373
374    // The number of bits available are the min of the two pointer types.
375    enum {
376      NumLowBitsAvailable =
377        PointerLikeTypeTraits<typename PointerUnion4<PT1, PT2, PT3, PT4>::ValTy>
378          ::NumLowBitsAvailable
379    };
380  };
381}
382
383#endif
384