LLVM  6.0.0svn
Casting.h
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1 //===- llvm/Support/Casting.h - Allow flexible, checked, casts --*- 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 isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(),
11 // and dyn_cast_or_null<X>() templates.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_SUPPORT_CASTING_H
16 #define LLVM_SUPPORT_CASTING_H
17 
18 #include "llvm/Support/Compiler.h"
20 #include <cassert>
21 #include <memory>
22 #include <type_traits>
23 
24 namespace llvm {
25 
26 //===----------------------------------------------------------------------===//
27 // isa<x> Support Templates
28 //===----------------------------------------------------------------------===//
29 
30 // Define a template that can be specialized by smart pointers to reflect the
31 // fact that they are automatically dereferenced, and are not involved with the
32 // template selection process... the default implementation is a noop.
33 //
34 template<typename From> struct simplify_type {
35  using SimpleType = From; // The real type this represents...
36 
37  // An accessor to get the real value...
38  static SimpleType &getSimplifiedValue(From &Val) { return Val; }
39 };
40 
41 template<typename From> struct simplify_type<const From> {
43  using SimpleType =
45  using RetType =
47 
48  static RetType getSimplifiedValue(const From& Val) {
49  return simplify_type<From>::getSimplifiedValue(const_cast<From&>(Val));
50  }
51 };
52 
53 // The core of the implementation of isa<X> is here; To and From should be
54 // the names of classes. This template can be specialized to customize the
55 // implementation of isa<> without rewriting it from scratch.
56 template <typename To, typename From, typename Enabler = void>
57 struct isa_impl {
58  static inline bool doit(const From &Val) {
59  return To::classof(&Val);
60  }
61 };
62 
63 /// \brief Always allow upcasts, and perform no dynamic check for them.
64 template <typename To, typename From>
65 struct isa_impl<
66  To, From, typename std::enable_if<std::is_base_of<To, From>::value>::type> {
67  static inline bool doit(const From &) { return true; }
68 };
69 
70 template <typename To, typename From> struct isa_impl_cl {
71  static inline bool doit(const From &Val) {
72  return isa_impl<To, From>::doit(Val);
73  }
74 };
75 
76 template <typename To, typename From> struct isa_impl_cl<To, const From> {
77  static inline bool doit(const From &Val) {
78  return isa_impl<To, From>::doit(Val);
79  }
80 };
81 
82 template <typename To, typename From>
83 struct isa_impl_cl<To, const std::unique_ptr<From>> {
84  static inline bool doit(const std::unique_ptr<From> &Val) {
85  assert(Val && "isa<> used on a null pointer");
86  return isa_impl_cl<To, From>::doit(*Val);
87  }
88 };
89 
90 template <typename To, typename From> struct isa_impl_cl<To, From*> {
91  static inline bool doit(const From *Val) {
92  assert(Val && "isa<> used on a null pointer");
93  return isa_impl<To, From>::doit(*Val);
94  }
95 };
96 
97 template <typename To, typename From> struct isa_impl_cl<To, From*const> {
98  static inline bool doit(const From *Val) {
99  assert(Val && "isa<> used on a null pointer");
100  return isa_impl<To, From>::doit(*Val);
101  }
102 };
103 
104 template <typename To, typename From> struct isa_impl_cl<To, const From*> {
105  static inline bool doit(const From *Val) {
106  assert(Val && "isa<> used on a null pointer");
107  return isa_impl<To, From>::doit(*Val);
108  }
109 };
110 
111 template <typename To, typename From> struct isa_impl_cl<To, const From*const> {
112  static inline bool doit(const From *Val) {
113  assert(Val && "isa<> used on a null pointer");
114  return isa_impl<To, From>::doit(*Val);
115  }
116 };
117 
118 template<typename To, typename From, typename SimpleFrom>
120  // When From != SimplifiedType, we can simplify the type some more by using
121  // the simplify_type template.
122  static bool doit(const From &Val) {
123  return isa_impl_wrap<To, SimpleFrom,
126  }
127 };
128 
129 template<typename To, typename FromTy>
130 struct isa_impl_wrap<To, FromTy, FromTy> {
131  // When From == SimpleType, we are as simple as we are going to get.
132  static bool doit(const FromTy &Val) {
133  return isa_impl_cl<To,FromTy>::doit(Val);
134  }
135 };
136 
137 // isa<X> - Return true if the parameter to the template is an instance of the
138 // template type argument. Used like this:
139 //
140 // if (isa<Type>(myVal)) { ... }
141 //
142 template <class X, class Y> LLVM_NODISCARD inline bool isa(const Y &Val) {
143  return isa_impl_wrap<X, const Y,
144  typename simplify_type<const Y>::SimpleType>::doit(Val);
145 }
146 
147 //===----------------------------------------------------------------------===//
148 // cast<x> Support Templates
149 //===----------------------------------------------------------------------===//
150 
151 template<class To, class From> struct cast_retty;
152 
153 // Calculate what type the 'cast' function should return, based on a requested
154 // type of To and a source type of From.
155 template<class To, class From> struct cast_retty_impl {
156  using ret_type = To &; // Normal case, return Ty&
157 };
158 template<class To, class From> struct cast_retty_impl<To, const From> {
159  using ret_type = const To &; // Normal case, return Ty&
160 };
161 
162 template<class To, class From> struct cast_retty_impl<To, From*> {
163  using ret_type = To *; // Pointer arg case, return Ty*
164 };
165 
166 template<class To, class From> struct cast_retty_impl<To, const From*> {
167  using ret_type = const To *; // Constant pointer arg case, return const Ty*
168 };
169 
170 template<class To, class From> struct cast_retty_impl<To, const From*const> {
171  using ret_type = const To *; // Constant pointer arg case, return const Ty*
172 };
173 
174 template <class To, class From>
175 struct cast_retty_impl<To, std::unique_ptr<From>> {
176 private:
177  using PointerType = typename cast_retty_impl<To, From *>::ret_type;
178  using ResultType = typename std::remove_pointer<PointerType>::type;
179 
180 public:
181  using ret_type = std::unique_ptr<ResultType>;
182 };
183 
184 template<class To, class From, class SimpleFrom>
186  // When the simplified type and the from type are not the same, use the type
187  // simplifier to reduce the type, then reuse cast_retty_impl to get the
188  // resultant type.
190 };
191 
192 template<class To, class FromTy>
193 struct cast_retty_wrap<To, FromTy, FromTy> {
194  // When the simplified type is equal to the from type, use it directly.
196 };
197 
198 template<class To, class From>
199 struct cast_retty {
200  using ret_type = typename cast_retty_wrap<
202 };
203 
204 // Ensure the non-simple values are converted using the simplify_type template
205 // that may be specialized by smart pointers...
206 //
207 template<class To, class From, class SimpleFrom> struct cast_convert_val {
208  // This is not a simple type, use the template to simplify it...
209  static typename cast_retty<To, From>::ret_type doit(From &Val) {
210  return cast_convert_val<To, SimpleFrom,
213  }
214 };
215 
216 template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> {
217  // This _is_ a simple type, just cast it.
218  static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
220  = (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val);
221  return Res2;
222  }
223 };
224 
225 template <class X> struct is_simple_type {
226  static const bool value =
227  std::is_same<X, typename simplify_type<X>::SimpleType>::value;
228 };
229 
230 // cast<X> - Return the argument parameter cast to the specified type. This
231 // casting operator asserts that the type is correct, so it does not return null
232 // on failure. It does not allow a null argument (use cast_or_null for that).
233 // It is typically used like this:
234 //
235 // cast<Instruction>(myVal)->getParent()
236 //
237 template <class X, class Y>
238 inline typename std::enable_if<!is_simple_type<Y>::value,
239  typename cast_retty<X, const Y>::ret_type>::type
240 cast(const Y &Val) {
241  assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
242  return cast_convert_val<
243  X, const Y, typename simplify_type<const Y>::SimpleType>::doit(Val);
244 }
245 
246 template <class X, class Y>
247 inline typename cast_retty<X, Y>::ret_type cast(Y &Val) {
248  assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
249  return cast_convert_val<X, Y,
250  typename simplify_type<Y>::SimpleType>::doit(Val);
251 }
252 
253 template <class X, class Y>
254 inline typename cast_retty<X, Y *>::ret_type cast(Y *Val) {
255  assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
256  return cast_convert_val<X, Y*,
257  typename simplify_type<Y*>::SimpleType>::doit(Val);
258 }
259 
260 template <class X, class Y>
261 inline typename cast_retty<X, std::unique_ptr<Y>>::ret_type
262 cast(std::unique_ptr<Y> &&Val) {
263  assert(isa<X>(Val.get()) && "cast<Ty>() argument of incompatible type!");
264  using ret_type = typename cast_retty<X, std::unique_ptr<Y>>::ret_type;
265  return ret_type(
267  Val.release()));
268 }
269 
270 // cast_or_null<X> - Functionally identical to cast, except that a null value is
271 // accepted.
272 //
273 template <class X, class Y>
274 LLVM_NODISCARD inline
275  typename std::enable_if<!is_simple_type<Y>::value,
276  typename cast_retty<X, const Y>::ret_type>::type
277  cast_or_null(const Y &Val) {
278  if (!Val)
279  return nullptr;
280  assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
281  return cast<X>(Val);
282 }
283 
284 template <class X, class Y>
285 LLVM_NODISCARD inline
286  typename std::enable_if<!is_simple_type<Y>::value,
287  typename cast_retty<X, Y>::ret_type>::type
288  cast_or_null(Y &Val) {
289  if (!Val)
290  return nullptr;
291  assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
292  return cast<X>(Val);
293 }
294 
295 template <class X, class Y>
298  if (!Val) return nullptr;
299  assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
300  return cast<X>(Val);
301 }
302 
303 template <class X, class Y>
304 inline typename cast_retty<X, std::unique_ptr<Y>>::ret_type
305 cast_or_null(std::unique_ptr<Y> &&Val) {
306  if (!Val)
307  return nullptr;
308  return cast<X>(std::move(Val));
309 }
310 
311 // dyn_cast<X> - Return the argument parameter cast to the specified type. This
312 // casting operator returns null if the argument is of the wrong type, so it can
313 // be used to test for a type as well as cast if successful. This should be
314 // used in the context of an if statement like this:
315 //
316 // if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
317 //
318 
319 template <class X, class Y>
320 LLVM_NODISCARD inline
321  typename std::enable_if<!is_simple_type<Y>::value,
322  typename cast_retty<X, const Y>::ret_type>::type
323  dyn_cast(const Y &Val) {
324  return isa<X>(Val) ? cast<X>(Val) : nullptr;
325 }
326 
327 template <class X, class Y>
329  return isa<X>(Val) ? cast<X>(Val) : nullptr;
330 }
331 
332 template <class X, class Y>
334  return isa<X>(Val) ? cast<X>(Val) : nullptr;
335 }
336 
337 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
338 // value is accepted.
339 //
340 template <class X, class Y>
341 LLVM_NODISCARD inline
342  typename std::enable_if<!is_simple_type<Y>::value,
343  typename cast_retty<X, const Y>::ret_type>::type
344  dyn_cast_or_null(const Y &Val) {
345  return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
346 }
347 
348 template <class X, class Y>
349 LLVM_NODISCARD inline
350  typename std::enable_if<!is_simple_type<Y>::value,
351  typename cast_retty<X, Y>::ret_type>::type
353  return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
354 }
355 
356 template <class X, class Y>
359  return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
360 }
361 
362 // unique_dyn_cast<X> - Given a unique_ptr<Y>, try to return a unique_ptr<X>,
363 // taking ownership of the input pointer iff isa<X>(Val) is true. If the
364 // cast is successful, From refers to nullptr on exit and the casted value
365 // is returned. If the cast is unsuccessful, the function returns nullptr
366 // and From is unchanged.
367 template <class X, class Y>
368 LLVM_NODISCARD inline auto unique_dyn_cast(std::unique_ptr<Y> &Val)
369  -> decltype(cast<X>(Val)) {
370  if (!isa<X>(Val))
371  return nullptr;
372  return cast<X>(std::move(Val));
373 }
374 
375 template <class X, class Y>
376 LLVM_NODISCARD inline auto unique_dyn_cast(std::unique_ptr<Y> &&Val)
377  -> decltype(cast<X>(Val)) {
378  return unique_dyn_cast<X, Y>(Val);
379 }
380 
381 // dyn_cast_or_null<X> - Functionally identical to unique_dyn_cast, except that
382 // a null value is accepted.
383 template <class X, class Y>
384 LLVM_NODISCARD inline auto unique_dyn_cast_or_null(std::unique_ptr<Y> &Val)
385  -> decltype(cast<X>(Val)) {
386  if (!Val)
387  return nullptr;
388  return unique_dyn_cast<X, Y>(Val);
389 }
390 
391 template <class X, class Y>
392 LLVM_NODISCARD inline auto unique_dyn_cast_or_null(std::unique_ptr<Y> &&Val)
393  -> decltype(cast<X>(Val)) {
394  return unique_dyn_cast_or_null<X, Y>(Val);
395 }
396 
397 } // end namespace llvm
398 
399 #endif // LLVM_SUPPORT_CASTING_H
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Definition: Casting.h:218
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type cast_or_null(const Y &Val)
Definition: Casting.h:277
LLVM_NODISCARD auto unique_dyn_cast(std::unique_ptr< Y > &Val) -> decltype(cast< X >(Val))
Definition: Casting.h:368
static RetType getSimplifiedValue(const From &Val)
Definition: Casting.h:48
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Definition: Casting.h:384
static bool doit(const From &Val)
Definition: Casting.h:77
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Definition: Casting.h:195
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Definition: Casting.h:105
static bool doit(const From &Val)
Definition: Casting.h:71
std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type cast(const Y &Val)
Definition: Casting.h:240
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Definition: Casting.h:209
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Definition: Casting.h:84
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Definition: Casting.h:46
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Definition: Casting.h:122
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Definition: Casting.h:181
static bool doit(const From *Val)
Definition: Casting.h:112
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Definition: Casting.h:201
static bool doit(const From *Val)
Definition: Casting.h:98
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Definition: Casting.h:344
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Definition: Casting.h:58
LLVM_NODISCARD bool isa(const Y &Val)
Definition: Casting.h:142
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Definition: Casting.h:42
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Definition: Casting.h:132
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
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Definition: Casting.h:38
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Definition: Casting.h:189
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Definition: Casting.h:44
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Definition: Casting.h:91