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/DenseMapInfo.h"
19#include "llvm/ADT/PointerIntPair.h"
20#include "llvm/Support/Compiler.h"
21
22namespace llvm {
23
24  template <typename T>
25  struct PointerUnionTypeSelectorReturn {
26    typedef T Return;
27  };
28
29  /// \brief Get a type based on whether two types are the same or not. For:
30  /// @code
31  /// typedef typename PointerUnionTypeSelector<T1, T2, EQ, NE>::Return Ret;
32  /// @endcode
33  /// Ret will be EQ type if T1 is same as T2 or NE type otherwise.
34  template <typename T1, typename T2, typename RET_EQ, typename RET_NE>
35  struct PointerUnionTypeSelector {
36    typedef typename PointerUnionTypeSelectorReturn<RET_NE>::Return Return;
37  };
38
39  template <typename T, typename RET_EQ, typename RET_NE>
40  struct PointerUnionTypeSelector<T, T, RET_EQ, RET_NE> {
41    typedef typename PointerUnionTypeSelectorReturn<RET_EQ>::Return Return;
42  };
43
44  template <typename T1, typename T2, typename RET_EQ, typename RET_NE>
45  struct PointerUnionTypeSelectorReturn<
46                            PointerUnionTypeSelector<T1, T2, RET_EQ, RET_NE> > {
47    typedef typename PointerUnionTypeSelector<T1, T2, RET_EQ, RET_NE>::Return
48        Return;
49  };
50
51  /// Provide PointerLikeTypeTraits for void* that is used by PointerUnion
52  /// for the two template arguments.
53  template <typename PT1, typename PT2>
54  class PointerUnionUIntTraits {
55  public:
56    static inline void *getAsVoidPointer(void *P) { return P; }
57    static inline void *getFromVoidPointer(void *P) { return P; }
58    enum {
59      PT1BitsAv = (int)(PointerLikeTypeTraits<PT1>::NumLowBitsAvailable),
60      PT2BitsAv = (int)(PointerLikeTypeTraits<PT2>::NumLowBitsAvailable),
61      NumLowBitsAvailable = PT1BitsAv < PT2BitsAv ? PT1BitsAv : PT2BitsAv
62    };
63  };
64
65  /// PointerUnion - This implements a discriminated union of two pointer types,
66  /// and keeps the discriminator bit-mangled into the low bits of the pointer.
67  /// This allows the implementation to be extremely efficient in space, but
68  /// permits a very natural and type-safe API.
69  ///
70  /// Common use patterns would be something like this:
71  ///    PointerUnion<int*, float*> P;
72  ///    P = (int*)0;
73  ///    printf("%d %d", P.is<int*>(), P.is<float*>());  // prints "1 0"
74  ///    X = P.get<int*>();     // ok.
75  ///    Y = P.get<float*>();   // runtime assertion failure.
76  ///    Z = P.get<double*>();  // compile time failure.
77  ///    P = (float*)0;
78  ///    Y = P.get<float*>();   // ok.
79  ///    X = P.get<int*>();     // runtime assertion failure.
80  template <typename PT1, typename PT2>
81  class PointerUnion {
82  public:
83    typedef PointerIntPair<void*, 1, bool,
84                           PointerUnionUIntTraits<PT1,PT2> > ValTy;
85  private:
86    ValTy Val;
87
88    struct IsPT1 {
89      static const int Num = 0;
90    };
91    struct IsPT2 {
92      static const int Num = 1;
93    };
94    template <typename T>
95    struct UNION_DOESNT_CONTAIN_TYPE { };
96
97  public:
98    PointerUnion() {}
99
100    PointerUnion(PT1 V) : Val(
101      const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(V))) {
102    }
103    PointerUnion(PT2 V) : Val(
104      const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(V)), 1) {
105    }
106
107    /// isNull - Return true if the pointer held in the union is null,
108    /// regardless of which type it is.
109    bool isNull() const {
110      // Convert from the void* to one of the pointer types, to make sure that
111      // we recursively strip off low bits if we have a nested PointerUnion.
112      return !PointerLikeTypeTraits<PT1>::getFromVoidPointer(Val.getPointer());
113    }
114    explicit operator bool() const { return !isNull(); }
115
116    /// is<T>() return true if the Union currently holds the type matching T.
117    template<typename T>
118    int is() const {
119      typedef typename
120        ::llvm::PointerUnionTypeSelector<PT1, T, IsPT1,
121          ::llvm::PointerUnionTypeSelector<PT2, T, IsPT2,
122                                    UNION_DOESNT_CONTAIN_TYPE<T> > >::Return Ty;
123      int TyNo = Ty::Num;
124      return static_cast<int>(Val.getInt()) == TyNo;
125    }
126
127    /// get<T>() - Return the value of the specified pointer type. If the
128    /// specified pointer type is incorrect, assert.
129    template<typename T>
130    T get() const {
131      assert(is<T>() && "Invalid accessor called");
132      return PointerLikeTypeTraits<T>::getFromVoidPointer(Val.getPointer());
133    }
134
135    /// dyn_cast<T>() - If the current value is of the specified pointer type,
136    /// return it, otherwise return null.
137    template<typename T>
138    T dyn_cast() const {
139      if (is<T>()) return get<T>();
140      return T();
141    }
142
143    /// \brief If the union is set to the first pointer type get an address
144    /// pointing to it.
145    PT1 const *getAddrOfPtr1() const {
146      return const_cast<PointerUnion *>(this)->getAddrOfPtr1();
147    }
148
149    /// \brief If the union is set to the first pointer type get an address
150    /// pointing to it.
151    PT1 *getAddrOfPtr1() {
152      assert(is<PT1>() && "Val is not the first pointer");
153      assert(get<PT1>() == Val.getPointer() &&
154         "Can't get the address because PointerLikeTypeTraits changes the ptr");
155      return (PT1 *)Val.getAddrOfPointer();
156    }
157
158    /// \brief Assignment from nullptr which just clears the union.
159    const PointerUnion &operator=(std::nullptr_t) {
160      Val.initWithPointer(nullptr);
161      return *this;
162    }
163
164    /// Assignment operators - Allow assigning into this union from either
165    /// pointer type, setting the discriminator to remember what it came from.
166    const PointerUnion &operator=(const PT1 &RHS) {
167      Val.initWithPointer(
168         const_cast<void *>(PointerLikeTypeTraits<PT1>::getAsVoidPointer(RHS)));
169      return *this;
170    }
171    const PointerUnion &operator=(const PT2 &RHS) {
172      Val.setPointerAndInt(
173        const_cast<void *>(PointerLikeTypeTraits<PT2>::getAsVoidPointer(RHS)),
174        1);
175      return *this;
176    }
177
178    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
179    static inline PointerUnion getFromOpaqueValue(void *VP) {
180      PointerUnion V;
181      V.Val = ValTy::getFromOpaqueValue(VP);
182      return V;
183    }
184  };
185
186  template<typename PT1, typename PT2>
187  static bool operator==(PointerUnion<PT1, PT2> lhs,
188                         PointerUnion<PT1, PT2> rhs) {
189    return lhs.getOpaqueValue() == rhs.getOpaqueValue();
190  }
191
192  template<typename PT1, typename PT2>
193  static bool operator!=(PointerUnion<PT1, PT2> lhs,
194                         PointerUnion<PT1, PT2> rhs) {
195    return lhs.getOpaqueValue() != rhs.getOpaqueValue();
196  }
197
198  template<typename PT1, typename PT2>
199  static bool operator<(PointerUnion<PT1, PT2> lhs,
200                        PointerUnion<PT1, PT2> rhs) {
201    return lhs.getOpaqueValue() < rhs.getOpaqueValue();
202  }
203
204  // Teach SmallPtrSet that PointerUnion is "basically a pointer", that has
205  // # low bits available = min(PT1bits,PT2bits)-1.
206  template<typename PT1, typename PT2>
207  class PointerLikeTypeTraits<PointerUnion<PT1, PT2> > {
208  public:
209    static inline void *
210    getAsVoidPointer(const PointerUnion<PT1, PT2> &P) {
211      return P.getOpaqueValue();
212    }
213    static inline PointerUnion<PT1, PT2>
214    getFromVoidPointer(void *P) {
215      return PointerUnion<PT1, PT2>::getFromOpaqueValue(P);
216    }
217
218    // The number of bits available are the min of the two pointer types.
219    enum {
220      NumLowBitsAvailable =
221        PointerLikeTypeTraits<typename PointerUnion<PT1,PT2>::ValTy>
222          ::NumLowBitsAvailable
223    };
224  };
225
226
227  /// PointerUnion3 - This is a pointer union of three pointer types.  See
228  /// documentation for PointerUnion for usage.
229  template <typename PT1, typename PT2, typename PT3>
230  class PointerUnion3 {
231  public:
232    typedef PointerUnion<PT1, PT2> InnerUnion;
233    typedef PointerUnion<InnerUnion, PT3> ValTy;
234  private:
235    ValTy Val;
236
237    struct IsInnerUnion {
238      ValTy Val;
239      IsInnerUnion(ValTy val) : Val(val) { }
240      template<typename T>
241      int is() const {
242        return Val.template is<InnerUnion>() &&
243               Val.template get<InnerUnion>().template is<T>();
244      }
245      template<typename T>
246      T get() const {
247        return Val.template get<InnerUnion>().template get<T>();
248      }
249    };
250
251    struct IsPT3 {
252      ValTy Val;
253      IsPT3(ValTy val) : Val(val) { }
254      template<typename T>
255      int is() const {
256        return Val.template is<T>();
257      }
258      template<typename T>
259      T get() const {
260        return Val.template get<T>();
261      }
262    };
263
264  public:
265    PointerUnion3() {}
266
267    PointerUnion3(PT1 V) {
268      Val = InnerUnion(V);
269    }
270    PointerUnion3(PT2 V) {
271      Val = InnerUnion(V);
272    }
273    PointerUnion3(PT3 V) {
274      Val = V;
275    }
276
277    /// isNull - Return true if the pointer held in the union is null,
278    /// regardless of which type it is.
279    bool isNull() const { return Val.isNull(); }
280    explicit operator bool() const { return !isNull(); }
281
282    /// is<T>() return true if the Union currently holds the type matching T.
283    template<typename T>
284    int is() const {
285      // If T is PT1/PT2 choose IsInnerUnion otherwise choose IsPT3.
286      typedef typename
287        ::llvm::PointerUnionTypeSelector<PT1, T, IsInnerUnion,
288          ::llvm::PointerUnionTypeSelector<PT2, T, IsInnerUnion, IsPT3 >
289                                                                   >::Return Ty;
290      return Ty(Val).template is<T>();
291    }
292
293    /// get<T>() - Return the value of the specified pointer type. If the
294    /// specified pointer type is incorrect, assert.
295    template<typename T>
296    T get() const {
297      assert(is<T>() && "Invalid accessor called");
298      // If T is PT1/PT2 choose IsInnerUnion otherwise choose IsPT3.
299      typedef typename
300        ::llvm::PointerUnionTypeSelector<PT1, T, IsInnerUnion,
301          ::llvm::PointerUnionTypeSelector<PT2, T, IsInnerUnion, IsPT3 >
302                                                                   >::Return Ty;
303      return Ty(Val).template get<T>();
304    }
305
306    /// dyn_cast<T>() - If the current value is of the specified pointer type,
307    /// return it, otherwise return null.
308    template<typename T>
309    T dyn_cast() const {
310      if (is<T>()) return get<T>();
311      return T();
312    }
313
314    /// \brief Assignment from nullptr which just clears the union.
315    const PointerUnion3 &operator=(std::nullptr_t) {
316      Val = nullptr;
317      return *this;
318    }
319
320    /// Assignment operators - Allow assigning into this union from either
321    /// pointer type, setting the discriminator to remember what it came from.
322    const PointerUnion3 &operator=(const PT1 &RHS) {
323      Val = InnerUnion(RHS);
324      return *this;
325    }
326    const PointerUnion3 &operator=(const PT2 &RHS) {
327      Val = InnerUnion(RHS);
328      return *this;
329    }
330    const PointerUnion3 &operator=(const PT3 &RHS) {
331      Val = RHS;
332      return *this;
333    }
334
335    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
336    static inline PointerUnion3 getFromOpaqueValue(void *VP) {
337      PointerUnion3 V;
338      V.Val = ValTy::getFromOpaqueValue(VP);
339      return V;
340    }
341  };
342
343  // Teach SmallPtrSet that PointerUnion3 is "basically a pointer", that has
344  // # low bits available = min(PT1bits,PT2bits,PT2bits)-2.
345  template<typename PT1, typename PT2, typename PT3>
346  class PointerLikeTypeTraits<PointerUnion3<PT1, PT2, PT3> > {
347  public:
348    static inline void *
349    getAsVoidPointer(const PointerUnion3<PT1, PT2, PT3> &P) {
350      return P.getOpaqueValue();
351    }
352    static inline PointerUnion3<PT1, PT2, PT3>
353    getFromVoidPointer(void *P) {
354      return PointerUnion3<PT1, PT2, PT3>::getFromOpaqueValue(P);
355    }
356
357    // The number of bits available are the min of the two pointer types.
358    enum {
359      NumLowBitsAvailable =
360        PointerLikeTypeTraits<typename PointerUnion3<PT1, PT2, PT3>::ValTy>
361          ::NumLowBitsAvailable
362    };
363  };
364
365  /// PointerUnion4 - This is a pointer union of four pointer types.  See
366  /// documentation for PointerUnion for usage.
367  template <typename PT1, typename PT2, typename PT3, typename PT4>
368  class PointerUnion4 {
369  public:
370    typedef PointerUnion<PT1, PT2> InnerUnion1;
371    typedef PointerUnion<PT3, PT4> InnerUnion2;
372    typedef PointerUnion<InnerUnion1, InnerUnion2> ValTy;
373  private:
374    ValTy Val;
375  public:
376    PointerUnion4() {}
377
378    PointerUnion4(PT1 V) {
379      Val = InnerUnion1(V);
380    }
381    PointerUnion4(PT2 V) {
382      Val = InnerUnion1(V);
383    }
384    PointerUnion4(PT3 V) {
385      Val = InnerUnion2(V);
386    }
387    PointerUnion4(PT4 V) {
388      Val = InnerUnion2(V);
389    }
390
391    /// isNull - Return true if the pointer held in the union is null,
392    /// regardless of which type it is.
393    bool isNull() const { return Val.isNull(); }
394    explicit operator bool() const { return !isNull(); }
395
396    /// is<T>() return true if the Union currently holds the type matching T.
397    template<typename T>
398    int is() const {
399      // If T is PT1/PT2 choose InnerUnion1 otherwise choose InnerUnion2.
400      typedef typename
401        ::llvm::PointerUnionTypeSelector<PT1, T, InnerUnion1,
402          ::llvm::PointerUnionTypeSelector<PT2, T, InnerUnion1, InnerUnion2 >
403                                                                   >::Return Ty;
404      return Val.template is<Ty>() &&
405             Val.template get<Ty>().template is<T>();
406    }
407
408    /// get<T>() - Return the value of the specified pointer type. If the
409    /// specified pointer type is incorrect, assert.
410    template<typename T>
411    T get() const {
412      assert(is<T>() && "Invalid accessor called");
413      // If T is PT1/PT2 choose InnerUnion1 otherwise choose InnerUnion2.
414      typedef typename
415        ::llvm::PointerUnionTypeSelector<PT1, T, InnerUnion1,
416          ::llvm::PointerUnionTypeSelector<PT2, T, InnerUnion1, InnerUnion2 >
417                                                                   >::Return Ty;
418      return Val.template get<Ty>().template get<T>();
419    }
420
421    /// dyn_cast<T>() - If the current value is of the specified pointer type,
422    /// return it, otherwise return null.
423    template<typename T>
424    T dyn_cast() const {
425      if (is<T>()) return get<T>();
426      return T();
427    }
428
429    /// \brief Assignment from nullptr which just clears the union.
430    const PointerUnion4 &operator=(std::nullptr_t) {
431      Val = nullptr;
432      return *this;
433    }
434
435    /// Assignment operators - Allow assigning into this union from either
436    /// pointer type, setting the discriminator to remember what it came from.
437    const PointerUnion4 &operator=(const PT1 &RHS) {
438      Val = InnerUnion1(RHS);
439      return *this;
440    }
441    const PointerUnion4 &operator=(const PT2 &RHS) {
442      Val = InnerUnion1(RHS);
443      return *this;
444    }
445    const PointerUnion4 &operator=(const PT3 &RHS) {
446      Val = InnerUnion2(RHS);
447      return *this;
448    }
449    const PointerUnion4 &operator=(const PT4 &RHS) {
450      Val = InnerUnion2(RHS);
451      return *this;
452    }
453
454    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
455    static inline PointerUnion4 getFromOpaqueValue(void *VP) {
456      PointerUnion4 V;
457      V.Val = ValTy::getFromOpaqueValue(VP);
458      return V;
459    }
460  };
461
462  // Teach SmallPtrSet that PointerUnion4 is "basically a pointer", that has
463  // # low bits available = min(PT1bits,PT2bits,PT2bits)-2.
464  template<typename PT1, typename PT2, typename PT3, typename PT4>
465  class PointerLikeTypeTraits<PointerUnion4<PT1, PT2, PT3, PT4> > {
466  public:
467    static inline void *
468    getAsVoidPointer(const PointerUnion4<PT1, PT2, PT3, PT4> &P) {
469      return P.getOpaqueValue();
470    }
471    static inline PointerUnion4<PT1, PT2, PT3, PT4>
472    getFromVoidPointer(void *P) {
473      return PointerUnion4<PT1, PT2, PT3, PT4>::getFromOpaqueValue(P);
474    }
475
476    // The number of bits available are the min of the two pointer types.
477    enum {
478      NumLowBitsAvailable =
479        PointerLikeTypeTraits<typename PointerUnion4<PT1, PT2, PT3, PT4>::ValTy>
480          ::NumLowBitsAvailable
481    };
482  };
483
484  // Teach DenseMap how to use PointerUnions as keys.
485  template<typename T, typename U>
486  struct DenseMapInfo<PointerUnion<T, U> > {
487    typedef PointerUnion<T, U> Pair;
488    typedef DenseMapInfo<T> FirstInfo;
489    typedef DenseMapInfo<U> SecondInfo;
490
491    static inline Pair getEmptyKey() {
492      return Pair(FirstInfo::getEmptyKey());
493    }
494    static inline Pair getTombstoneKey() {
495      return Pair(FirstInfo::getTombstoneKey());
496    }
497    static unsigned getHashValue(const Pair &PairVal) {
498      intptr_t key = (intptr_t)PairVal.getOpaqueValue();
499      return DenseMapInfo<intptr_t>::getHashValue(key);
500    }
501    static bool isEqual(const Pair &LHS, const Pair &RHS) {
502      return LHS.template is<T>() == RHS.template is<T>() &&
503             (LHS.template is<T>() ?
504              FirstInfo::isEqual(LHS.template get<T>(),
505                                 RHS.template get<T>()) :
506              SecondInfo::isEqual(LHS.template get<U>(),
507                                  RHS.template get<U>()));
508    }
509  };
510}
511
512#endif
513