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    LLVM_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  // Teach SmallPtrSet that PointerUnion is "basically a pointer", that has
199  // # low bits available = min(PT1bits,PT2bits)-1.
200  template<typename PT1, typename PT2>
201  class PointerLikeTypeTraits<PointerUnion<PT1, PT2> > {
202  public:
203    static inline void *
204    getAsVoidPointer(const PointerUnion<PT1, PT2> &P) {
205      return P.getOpaqueValue();
206    }
207    static inline PointerUnion<PT1, PT2>
208    getFromVoidPointer(void *P) {
209      return PointerUnion<PT1, PT2>::getFromOpaqueValue(P);
210    }
211
212    // The number of bits available are the min of the two pointer types.
213    enum {
214      NumLowBitsAvailable =
215        PointerLikeTypeTraits<typename PointerUnion<PT1,PT2>::ValTy>
216          ::NumLowBitsAvailable
217    };
218  };
219
220
221  /// PointerUnion3 - This is a pointer union of three pointer types.  See
222  /// documentation for PointerUnion for usage.
223  template <typename PT1, typename PT2, typename PT3>
224  class PointerUnion3 {
225  public:
226    typedef PointerUnion<PT1, PT2> InnerUnion;
227    typedef PointerUnion<InnerUnion, PT3> ValTy;
228  private:
229    ValTy Val;
230
231    struct IsInnerUnion {
232      ValTy Val;
233      IsInnerUnion(ValTy val) : Val(val) { }
234      template<typename T>
235      int is() const {
236        return Val.template is<InnerUnion>() &&
237               Val.template get<InnerUnion>().template is<T>();
238      }
239      template<typename T>
240      T get() const {
241        return Val.template get<InnerUnion>().template get<T>();
242      }
243    };
244
245    struct IsPT3 {
246      ValTy Val;
247      IsPT3(ValTy val) : Val(val) { }
248      template<typename T>
249      int is() const {
250        return Val.template is<T>();
251      }
252      template<typename T>
253      T get() const {
254        return Val.template get<T>();
255      }
256    };
257
258  public:
259    PointerUnion3() {}
260
261    PointerUnion3(PT1 V) {
262      Val = InnerUnion(V);
263    }
264    PointerUnion3(PT2 V) {
265      Val = InnerUnion(V);
266    }
267    PointerUnion3(PT3 V) {
268      Val = V;
269    }
270
271    /// isNull - Return true if the pointer held in the union is null,
272    /// regardless of which type it is.
273    bool isNull() const { return Val.isNull(); }
274    LLVM_EXPLICIT operator bool() const { return !isNull(); }
275
276    /// is<T>() return true if the Union currently holds the type matching T.
277    template<typename T>
278    int is() const {
279      // If T is PT1/PT2 choose IsInnerUnion otherwise choose IsPT3.
280      typedef typename
281        ::llvm::PointerUnionTypeSelector<PT1, T, IsInnerUnion,
282          ::llvm::PointerUnionTypeSelector<PT2, T, IsInnerUnion, IsPT3 >
283                                                                   >::Return Ty;
284      return Ty(Val).template is<T>();
285    }
286
287    /// get<T>() - Return the value of the specified pointer type. If the
288    /// specified pointer type is incorrect, assert.
289    template<typename T>
290    T get() const {
291      assert(is<T>() && "Invalid accessor called");
292      // If T is PT1/PT2 choose IsInnerUnion otherwise choose IsPT3.
293      typedef typename
294        ::llvm::PointerUnionTypeSelector<PT1, T, IsInnerUnion,
295          ::llvm::PointerUnionTypeSelector<PT2, T, IsInnerUnion, IsPT3 >
296                                                                   >::Return Ty;
297      return Ty(Val).template get<T>();
298    }
299
300    /// dyn_cast<T>() - If the current value is of the specified pointer type,
301    /// return it, otherwise return null.
302    template<typename T>
303    T dyn_cast() const {
304      if (is<T>()) return get<T>();
305      return T();
306    }
307
308    /// \brief Assignment from nullptr which just clears the union.
309    const PointerUnion3 &operator=(std::nullptr_t) {
310      Val = nullptr;
311      return *this;
312    }
313
314    /// Assignment operators - Allow assigning into this union from either
315    /// pointer type, setting the discriminator to remember what it came from.
316    const PointerUnion3 &operator=(const PT1 &RHS) {
317      Val = InnerUnion(RHS);
318      return *this;
319    }
320    const PointerUnion3 &operator=(const PT2 &RHS) {
321      Val = InnerUnion(RHS);
322      return *this;
323    }
324    const PointerUnion3 &operator=(const PT3 &RHS) {
325      Val = RHS;
326      return *this;
327    }
328
329    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
330    static inline PointerUnion3 getFromOpaqueValue(void *VP) {
331      PointerUnion3 V;
332      V.Val = ValTy::getFromOpaqueValue(VP);
333      return V;
334    }
335  };
336
337  // Teach SmallPtrSet that PointerUnion3 is "basically a pointer", that has
338  // # low bits available = min(PT1bits,PT2bits,PT2bits)-2.
339  template<typename PT1, typename PT2, typename PT3>
340  class PointerLikeTypeTraits<PointerUnion3<PT1, PT2, PT3> > {
341  public:
342    static inline void *
343    getAsVoidPointer(const PointerUnion3<PT1, PT2, PT3> &P) {
344      return P.getOpaqueValue();
345    }
346    static inline PointerUnion3<PT1, PT2, PT3>
347    getFromVoidPointer(void *P) {
348      return PointerUnion3<PT1, PT2, PT3>::getFromOpaqueValue(P);
349    }
350
351    // The number of bits available are the min of the two pointer types.
352    enum {
353      NumLowBitsAvailable =
354        PointerLikeTypeTraits<typename PointerUnion3<PT1, PT2, PT3>::ValTy>
355          ::NumLowBitsAvailable
356    };
357  };
358
359  /// PointerUnion4 - This is a pointer union of four pointer types.  See
360  /// documentation for PointerUnion for usage.
361  template <typename PT1, typename PT2, typename PT3, typename PT4>
362  class PointerUnion4 {
363  public:
364    typedef PointerUnion<PT1, PT2> InnerUnion1;
365    typedef PointerUnion<PT3, PT4> InnerUnion2;
366    typedef PointerUnion<InnerUnion1, InnerUnion2> ValTy;
367  private:
368    ValTy Val;
369  public:
370    PointerUnion4() {}
371
372    PointerUnion4(PT1 V) {
373      Val = InnerUnion1(V);
374    }
375    PointerUnion4(PT2 V) {
376      Val = InnerUnion1(V);
377    }
378    PointerUnion4(PT3 V) {
379      Val = InnerUnion2(V);
380    }
381    PointerUnion4(PT4 V) {
382      Val = InnerUnion2(V);
383    }
384
385    /// isNull - Return true if the pointer held in the union is null,
386    /// regardless of which type it is.
387    bool isNull() const { return Val.isNull(); }
388    LLVM_EXPLICIT operator bool() const { return !isNull(); }
389
390    /// is<T>() return true if the Union currently holds the type matching T.
391    template<typename T>
392    int is() const {
393      // If T is PT1/PT2 choose InnerUnion1 otherwise choose InnerUnion2.
394      typedef typename
395        ::llvm::PointerUnionTypeSelector<PT1, T, InnerUnion1,
396          ::llvm::PointerUnionTypeSelector<PT2, T, InnerUnion1, InnerUnion2 >
397                                                                   >::Return Ty;
398      return Val.template is<Ty>() &&
399             Val.template get<Ty>().template is<T>();
400    }
401
402    /// get<T>() - Return the value of the specified pointer type. If the
403    /// specified pointer type is incorrect, assert.
404    template<typename T>
405    T get() const {
406      assert(is<T>() && "Invalid accessor called");
407      // If T is PT1/PT2 choose InnerUnion1 otherwise choose InnerUnion2.
408      typedef typename
409        ::llvm::PointerUnionTypeSelector<PT1, T, InnerUnion1,
410          ::llvm::PointerUnionTypeSelector<PT2, T, InnerUnion1, InnerUnion2 >
411                                                                   >::Return Ty;
412      return Val.template get<Ty>().template get<T>();
413    }
414
415    /// dyn_cast<T>() - If the current value is of the specified pointer type,
416    /// return it, otherwise return null.
417    template<typename T>
418    T dyn_cast() const {
419      if (is<T>()) return get<T>();
420      return T();
421    }
422
423    /// \brief Assignment from nullptr which just clears the union.
424    const PointerUnion4 &operator=(std::nullptr_t) {
425      Val = nullptr;
426      return *this;
427    }
428
429    /// Assignment operators - Allow assigning into this union from either
430    /// pointer type, setting the discriminator to remember what it came from.
431    const PointerUnion4 &operator=(const PT1 &RHS) {
432      Val = InnerUnion1(RHS);
433      return *this;
434    }
435    const PointerUnion4 &operator=(const PT2 &RHS) {
436      Val = InnerUnion1(RHS);
437      return *this;
438    }
439    const PointerUnion4 &operator=(const PT3 &RHS) {
440      Val = InnerUnion2(RHS);
441      return *this;
442    }
443    const PointerUnion4 &operator=(const PT4 &RHS) {
444      Val = InnerUnion2(RHS);
445      return *this;
446    }
447
448    void *getOpaqueValue() const { return Val.getOpaqueValue(); }
449    static inline PointerUnion4 getFromOpaqueValue(void *VP) {
450      PointerUnion4 V;
451      V.Val = ValTy::getFromOpaqueValue(VP);
452      return V;
453    }
454  };
455
456  // Teach SmallPtrSet that PointerUnion4 is "basically a pointer", that has
457  // # low bits available = min(PT1bits,PT2bits,PT2bits)-2.
458  template<typename PT1, typename PT2, typename PT3, typename PT4>
459  class PointerLikeTypeTraits<PointerUnion4<PT1, PT2, PT3, PT4> > {
460  public:
461    static inline void *
462    getAsVoidPointer(const PointerUnion4<PT1, PT2, PT3, PT4> &P) {
463      return P.getOpaqueValue();
464    }
465    static inline PointerUnion4<PT1, PT2, PT3, PT4>
466    getFromVoidPointer(void *P) {
467      return PointerUnion4<PT1, PT2, PT3, PT4>::getFromOpaqueValue(P);
468    }
469
470    // The number of bits available are the min of the two pointer types.
471    enum {
472      NumLowBitsAvailable =
473        PointerLikeTypeTraits<typename PointerUnion4<PT1, PT2, PT3, PT4>::ValTy>
474          ::NumLowBitsAvailable
475    };
476  };
477
478  // Teach DenseMap how to use PointerUnions as keys.
479  template<typename T, typename U>
480  struct DenseMapInfo<PointerUnion<T, U> > {
481    typedef PointerUnion<T, U> Pair;
482    typedef DenseMapInfo<T> FirstInfo;
483    typedef DenseMapInfo<U> SecondInfo;
484
485    static inline Pair getEmptyKey() {
486      return Pair(FirstInfo::getEmptyKey());
487    }
488    static inline Pair getTombstoneKey() {
489      return Pair(FirstInfo::getTombstoneKey());
490    }
491    static unsigned getHashValue(const Pair &PairVal) {
492      intptr_t key = (intptr_t)PairVal.getOpaqueValue();
493      return DenseMapInfo<intptr_t>::getHashValue(key);
494    }
495    static bool isEqual(const Pair &LHS, const Pair &RHS) {
496      return LHS.template is<T>() == RHS.template is<T>() &&
497             (LHS.template is<T>() ?
498              FirstInfo::isEqual(LHS.template get<T>(),
499                                 RHS.template get<T>()) :
500              SecondInfo::isEqual(LHS.template get<U>(),
501                                  RHS.template get<U>()));
502    }
503  };
504}
505
506#endif
507