PointerUnion.h revision 6a66b388469f045c9fcff839595900c9f1512177 
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    /// Assignment operators - Allow assigning into this union from either
112    /// pointer type, setting the discriminator to remember what it came from.
113    const PointerUnion &operator=(const PT1 &RHS) {
114      Val.setPointer(
115         const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(RHS)));
116      Val.setInt(0);
117      return *this;
118    }
119    const PointerUnion &operator=(const PT2 &RHS) {
120      Val.setPointer(
121        const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(RHS)));
122      Val.setInt(1);
123      return *this;
124    }
125
126    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
127    static PointerUnion getFromOpaqueValue(void *VP) {
128      PointerUnion V;
129      V.Val = ValTy::getFromOpaqueValue(VP);
130      return V;
131    }
132  };
133
134  // Teach SmallPtrSet that PointerUnion is "basically a pointer", that has
135  // # low bits available = min(PT1bits,PT2bits)-1.
136  template<typename PT1, typename PT2>
137  class PointerLikeTypeTraits<PointerUnion<PT1, PT2> > {
138  public:
139    static inline void *
140    getAsVoidPointer(const PointerUnion<PT1, PT2> &P) {
141      return P.getOpaqueValue();
142    }
143    static inline PointerUnion<PT1, PT2>
144    getFromVoidPointer(void *P) {
145      return PointerUnion<PT1, PT2>::getFromOpaqueValue(P);
146    }
147
148    // The number of bits available are the min of the two pointer types.
149    enum {
150      NumLowBitsAvailable =
151        PointerLikeTypeTraits<typename PointerUnion<PT1,PT2>::ValTy>
152          ::NumLowBitsAvailable
153    };
154  };
155
156
157  /// PointerUnion3 - This is a pointer union of three pointer types.  See
158  /// documentation for PointerUnion for usage.
159  template <typename PT1, typename PT2, typename PT3>
160  class PointerUnion3 {
161  public:
162    typedef PointerUnion<PT1, PT2> InnerUnion;
163    typedef PointerUnion<InnerUnion, PT3> ValTy;
164  private:
165    ValTy Val;
166  public:
167    PointerUnion3() {}
168
169    PointerUnion3(PT1 V) {
170      Val = InnerUnion(V);
171    }
172    PointerUnion3(PT2 V) {
173      Val = InnerUnion(V);
174    }
175    PointerUnion3(PT3 V) {
176      Val = V;
177    }
178
179    /// isNull - Return true if the pointer held in the union is null,
180    /// regardless of which type it is.
181    bool isNull() const { return Val.isNull(); }
182    operator bool() const { return !isNull(); }
183
184    /// is<T>() return true if the Union currently holds the type matching T.
185    template<typename T>
186    int is() const {
187      // Is it PT1/PT2?
188      if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
189        return Val.template is<InnerUnion>() &&
190               Val.template get<InnerUnion>().template is<T>();
191      return Val.template is<T>();
192    }
193
194    /// get<T>() - Return the value of the specified pointer type. If the
195    /// specified pointer type is incorrect, assert.
196    template<typename T>
197    T get() const {
198      assert(is<T>() && "Invalid accessor called");
199      // Is it PT1/PT2?
200      if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
201        return Val.template get<InnerUnion>().template get<T>();
202
203      return Val.template get<T>();
204    }
205
206    /// dyn_cast<T>() - If the current value is of the specified pointer type,
207    /// return it, otherwise return null.
208    template<typename T>
209    T dyn_cast() const {
210      if (is<T>()) return get<T>();
211      return T();
212    }
213
214    /// Assignment operators - Allow assigning into this union from either
215    /// pointer type, setting the discriminator to remember what it came from.
216    const PointerUnion3 &operator=(const PT1 &RHS) {
217      Val = InnerUnion(RHS);
218      return *this;
219    }
220    const PointerUnion3 &operator=(const PT2 &RHS) {
221      Val = InnerUnion(RHS);
222      return *this;
223    }
224    const PointerUnion3 &operator=(const PT3 &RHS) {
225      Val = RHS;
226      return *this;
227    }
228
229    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
230    static PointerUnion3 getFromOpaqueValue(void *VP) {
231      PointerUnion3 V;
232      V.Val = ValTy::getFromOpaqueValue(VP);
233      return V;
234    }
235  };
236
237  // Teach SmallPtrSet that PointerUnion3 is "basically a pointer", that has
238  // # low bits available = min(PT1bits,PT2bits,PT2bits)-2.
239  template<typename PT1, typename PT2, typename PT3>
240  class PointerLikeTypeTraits<PointerUnion3<PT1, PT2, PT3> > {
241  public:
242    static inline void *
243    getAsVoidPointer(const PointerUnion3<PT1, PT2, PT3> &P) {
244      return P.getOpaqueValue();
245    }
246    static inline PointerUnion3<PT1, PT2, PT3>
247    getFromVoidPointer(void *P) {
248      return PointerUnion3<PT1, PT2, PT3>::getFromOpaqueValue(P);
249    }
250
251    // The number of bits available are the min of the two pointer types.
252    enum {
253      NumLowBitsAvailable =
254        PointerLikeTypeTraits<typename PointerUnion3<PT1, PT2, PT3>::ValTy>
255          ::NumLowBitsAvailable
256    };
257  };
258
259  /// PointerUnion4 - This is a pointer union of four pointer types.  See
260  /// documentation for PointerUnion for usage.
261  template <typename PT1, typename PT2, typename PT3, typename PT4>
262  class PointerUnion4 {
263  public:
264    typedef PointerUnion<PT1, PT2> InnerUnion1;
265    typedef PointerUnion<PT3, PT4> InnerUnion2;
266    typedef PointerUnion<InnerUnion1, InnerUnion2> ValTy;
267  private:
268    ValTy Val;
269  public:
270    PointerUnion4() {}
271
272    PointerUnion4(PT1 V) {
273      Val = InnerUnion1(V);
274    }
275    PointerUnion4(PT2 V) {
276      Val = InnerUnion1(V);
277    }
278    PointerUnion4(PT3 V) {
279      Val = InnerUnion2(V);
280    }
281    PointerUnion4(PT4 V) {
282      Val = InnerUnion2(V);
283    }
284
285    /// isNull - Return true if the pointer held in the union is null,
286    /// regardless of which type it is.
287    bool isNull() const { return Val.isNull(); }
288    operator bool() const { return !isNull(); }
289
290    /// is<T>() return true if the Union currently holds the type matching T.
291    template<typename T>
292    int is() const {
293      // Is it PT1/PT2?
294      if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
295        return Val.template is<InnerUnion1>() &&
296               Val.template get<InnerUnion1>().template is<T>();
297      return Val.template is<InnerUnion2>() &&
298             Val.template get<InnerUnion2>().template is<T>();
299    }
300
301    /// get<T>() - Return the value of the specified pointer type. If the
302    /// specified pointer type is incorrect, assert.
303    template<typename T>
304    T get() const {
305      assert(is<T>() && "Invalid accessor called");
306      // Is it PT1/PT2?
307      if (::llvm::getPointerUnionTypeNum<PT1, PT2>((T*)0) != -1)
308        return Val.template get<InnerUnion1>().template get<T>();
309
310      return Val.template get<InnerUnion2>().template get<T>();
311    }
312
313    /// dyn_cast<T>() - If the current value is of the specified pointer type,
314    /// return it, otherwise return null.
315    template<typename T>
316    T dyn_cast() const {
317      if (is<T>()) return get<T>();
318      return T();
319    }
320
321    /// Assignment operators - Allow assigning into this union from either
322    /// pointer type, setting the discriminator to remember what it came from.
323    const PointerUnion4 &operator=(const PT1 &RHS) {
324      Val = InnerUnion1(RHS);
325      return *this;
326    }
327    const PointerUnion4 &operator=(const PT2 &RHS) {
328      Val = InnerUnion1(RHS);
329      return *this;
330    }
331    const PointerUnion4 &operator=(const PT3 &RHS) {
332      Val = InnerUnion2(RHS);
333      return *this;
334    }
335    const PointerUnion4 &operator=(const PT4 &RHS) {
336      Val = InnerUnion2(RHS);
337      return *this;
338    }
339
340    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
341    static PointerUnion4 getFromOpaqueValue(void *VP) {
342      PointerUnion4 V;
343      V.Val = ValTy::getFromOpaqueValue(VP);
344      return V;
345    }
346  };
347
348  // Teach SmallPtrSet that PointerUnion4 is "basically a pointer", that has
349  // # low bits available = min(PT1bits,PT2bits,PT2bits)-2.
350  template<typename PT1, typename PT2, typename PT3, typename PT4>
351  class PointerLikeTypeTraits<PointerUnion4<PT1, PT2, PT3, PT4> > {
352  public:
353    static inline void *
354    getAsVoidPointer(const PointerUnion4<PT1, PT2, PT3, PT4> &P) {
355      return P.getOpaqueValue();
356    }
357    static inline PointerUnion4<PT1, PT2, PT3, PT4>
358    getFromVoidPointer(void *P) {
359      return PointerUnion4<PT1, PT2, PT3, PT4>::getFromOpaqueValue(P);
360    }
361
362    // The number of bits available are the min of the two pointer types.
363    enum {
364      NumLowBitsAvailable =
365        PointerLikeTypeTraits<typename PointerUnion4<PT1, PT2, PT3, PT4>::ValTy>
366          ::NumLowBitsAvailable
367    };
368  };
369}
370
371#endif
372