LLVM  4.0.0
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 
22 namespace llvm {
23 
24 //===----------------------------------------------------------------------===//
25 // isa<x> Support Templates
26 //===----------------------------------------------------------------------===//
27 
28 // Define a template that can be specialized by smart pointers to reflect the
29 // fact that they are automatically dereferenced, and are not involved with the
30 // template selection process... the default implementation is a noop.
31 //
32 template<typename From> struct simplify_type {
33  typedef From SimpleType; // The real type this represents...
34 
35  // An accessor to get the real value...
36  static SimpleType &getSimplifiedValue(From &Val) { return Val; }
37 };
38 
39 template<typename From> struct simplify_type<const From> {
45  static RetType getSimplifiedValue(const From& Val) {
46  return simplify_type<From>::getSimplifiedValue(const_cast<From&>(Val));
47  }
48 };
49 
50 // The core of the implementation of isa<X> is here; To and From should be
51 // the names of classes. This template can be specialized to customize the
52 // implementation of isa<> without rewriting it from scratch.
53 template <typename To, typename From, typename Enabler = void>
54 struct isa_impl {
55  static inline bool doit(const From &Val) {
56  return To::classof(&Val);
57  }
58 };
59 
60 /// \brief Always allow upcasts, and perform no dynamic check for them.
61 template <typename To, typename From>
62 struct isa_impl<
63  To, From, typename std::enable_if<std::is_base_of<To, From>::value>::type> {
64  static inline bool doit(const From &) { return true; }
65 };
66 
67 template <typename To, typename From> struct isa_impl_cl {
68  static inline bool doit(const From &Val) {
69  return isa_impl<To, From>::doit(Val);
70  }
71 };
72 
73 template <typename To, typename From> struct isa_impl_cl<To, const From> {
74  static inline bool doit(const From &Val) {
75  return isa_impl<To, From>::doit(Val);
76  }
77 };
78 
79 template <typename To, typename From> struct isa_impl_cl<To, From*> {
80  static inline bool doit(const From *Val) {
81  assert(Val && "isa<> used on a null pointer");
82  return isa_impl<To, From>::doit(*Val);
83  }
84 };
85 
86 template <typename To, typename From> struct isa_impl_cl<To, From*const> {
87  static inline bool doit(const From *Val) {
88  assert(Val && "isa<> used on a null pointer");
89  return isa_impl<To, From>::doit(*Val);
90  }
91 };
92 
93 template <typename To, typename From> struct isa_impl_cl<To, const From*> {
94  static inline bool doit(const From *Val) {
95  assert(Val && "isa<> used on a null pointer");
96  return isa_impl<To, From>::doit(*Val);
97  }
98 };
99 
100 template <typename To, typename From> struct isa_impl_cl<To, const From*const> {
101  static inline bool doit(const From *Val) {
102  assert(Val && "isa<> used on a null pointer");
103  return isa_impl<To, From>::doit(*Val);
104  }
105 };
106 
107 template<typename To, typename From, typename SimpleFrom>
109  // When From != SimplifiedType, we can simplify the type some more by using
110  // the simplify_type template.
111  static bool doit(const From &Val) {
112  return isa_impl_wrap<To, SimpleFrom,
115  }
116 };
117 
118 template<typename To, typename FromTy>
119 struct isa_impl_wrap<To, FromTy, FromTy> {
120  // When From == SimpleType, we are as simple as we are going to get.
121  static bool doit(const FromTy &Val) {
122  return isa_impl_cl<To,FromTy>::doit(Val);
123  }
124 };
125 
126 // isa<X> - Return true if the parameter to the template is an instance of the
127 // template type argument. Used like this:
128 //
129 // if (isa<Type>(myVal)) { ... }
130 //
131 template <class X, class Y> LLVM_NODISCARD inline bool isa(const Y &Val) {
132  return isa_impl_wrap<X, const Y,
133  typename simplify_type<const Y>::SimpleType>::doit(Val);
134 }
135 
136 //===----------------------------------------------------------------------===//
137 // cast<x> Support Templates
138 //===----------------------------------------------------------------------===//
139 
140 template<class To, class From> struct cast_retty;
141 
142 
143 // Calculate what type the 'cast' function should return, based on a requested
144 // type of To and a source type of From.
145 template<class To, class From> struct cast_retty_impl {
146  typedef To& ret_type; // Normal case, return Ty&
147 };
148 template<class To, class From> struct cast_retty_impl<To, const From> {
149  typedef const To &ret_type; // Normal case, return Ty&
150 };
151 
152 template<class To, class From> struct cast_retty_impl<To, From*> {
153  typedef To* ret_type; // Pointer arg case, return Ty*
154 };
155 
156 template<class To, class From> struct cast_retty_impl<To, const From*> {
157  typedef const To* ret_type; // Constant pointer arg case, return const Ty*
158 };
159 
160 template<class To, class From> struct cast_retty_impl<To, const From*const> {
161  typedef const To* ret_type; // Constant pointer arg case, return const Ty*
162 };
163 
164 
165 template<class To, class From, class SimpleFrom>
167  // When the simplified type and the from type are not the same, use the type
168  // simplifier to reduce the type, then reuse cast_retty_impl to get the
169  // resultant type.
171 };
172 
173 template<class To, class FromTy>
174 struct cast_retty_wrap<To, FromTy, FromTy> {
175  // When the simplified type is equal to the from type, use it directly.
177 };
178 
179 template<class To, class From>
180 struct cast_retty {
181  typedef typename cast_retty_wrap<To, From,
183 };
184 
185 // Ensure the non-simple values are converted using the simplify_type template
186 // that may be specialized by smart pointers...
187 //
188 template<class To, class From, class SimpleFrom> struct cast_convert_val {
189  // This is not a simple type, use the template to simplify it...
190  static typename cast_retty<To, From>::ret_type doit(From &Val) {
191  return cast_convert_val<To, SimpleFrom,
194  }
195 };
196 
197 template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> {
198  // This _is_ a simple type, just cast it.
199  static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
201  = (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val);
202  return Res2;
203  }
204 };
205 
206 template <class X> struct is_simple_type {
207  static const bool value =
208  std::is_same<X, typename simplify_type<X>::SimpleType>::value;
209 };
210 
211 // cast<X> - Return the argument parameter cast to the specified type. This
212 // casting operator asserts that the type is correct, so it does not return null
213 // on failure. It does not allow a null argument (use cast_or_null for that).
214 // It is typically used like this:
215 //
216 // cast<Instruction>(myVal)->getParent()
217 //
218 template <class X, class Y>
219 inline typename std::enable_if<!is_simple_type<Y>::value,
220  typename cast_retty<X, const Y>::ret_type>::type
221 cast(const Y &Val) {
222  assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
223  return cast_convert_val<
224  X, const Y, typename simplify_type<const Y>::SimpleType>::doit(Val);
225 }
226 
227 template <class X, class Y>
228 inline typename cast_retty<X, Y>::ret_type cast(Y &Val) {
229  assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
230  return cast_convert_val<X, Y,
231  typename simplify_type<Y>::SimpleType>::doit(Val);
232 }
233 
234 template <class X, class Y>
235 inline typename cast_retty<X, Y *>::ret_type cast(Y *Val) {
236  assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
237  return cast_convert_val<X, Y*,
238  typename simplify_type<Y*>::SimpleType>::doit(Val);
239 }
240 
241 // cast_or_null<X> - Functionally identical to cast, except that a null value is
242 // accepted.
243 //
244 template <class X, class Y>
245 LLVM_NODISCARD inline
246  typename std::enable_if<!is_simple_type<Y>::value,
247  typename cast_retty<X, const Y>::ret_type>::type
248  cast_or_null(const Y &Val) {
249  if (!Val)
250  return nullptr;
251  assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
252  return cast<X>(Val);
253 }
254 
255 template <class X, class Y>
256 LLVM_NODISCARD inline
257  typename std::enable_if<!is_simple_type<Y>::value,
258  typename cast_retty<X, Y>::ret_type>::type
259  cast_or_null(Y &Val) {
260  if (!Val)
261  return nullptr;
262  assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
263  return cast<X>(Val);
264 }
265 
266 template <class X, class Y>
267 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type
269  if (!Val) return nullptr;
270  assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
271  return cast<X>(Val);
272 }
273 
274 
275 // dyn_cast<X> - Return the argument parameter cast to the specified type. This
276 // casting operator returns null if the argument is of the wrong type, so it can
277 // be used to test for a type as well as cast if successful. This should be
278 // used in the context of an if statement like this:
279 //
280 // if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
281 //
282 
283 template <class X, class Y>
284 LLVM_NODISCARD inline
285  typename std::enable_if<!is_simple_type<Y>::value,
286  typename cast_retty<X, const Y>::ret_type>::type
287  dyn_cast(const Y &Val) {
288  return isa<X>(Val) ? cast<X>(Val) : nullptr;
289 }
290 
291 template <class X, class Y>
293  return isa<X>(Val) ? cast<X>(Val) : nullptr;
294 }
295 
296 template <class X, class Y>
298  return isa<X>(Val) ? cast<X>(Val) : nullptr;
299 }
300 
301 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
302 // value is accepted.
303 //
304 template <class X, class Y>
305 LLVM_NODISCARD inline
306  typename std::enable_if<!is_simple_type<Y>::value,
307  typename cast_retty<X, const Y>::ret_type>::type
308  dyn_cast_or_null(const Y &Val) {
309  return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
310 }
311 
312 template <class X, class Y>
313 LLVM_NODISCARD inline
314  typename std::enable_if<!is_simple_type<Y>::value,
315  typename cast_retty<X, Y>::ret_type>::type
317  return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
318 }
319 
320 template <class X, class Y>
321 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type
323  return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
324 }
325 
326 } // End llvm namespace
327 
328 #endif
static bool doit(const From *Val)
Definition: Casting.h:87
static cast_retty< To, FromTy >::ret_type doit(const FromTy &Val)
Definition: Casting.h:199
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:248
static RetType getSimplifiedValue(const From &Val)
Definition: Casting.h:45
static bool doit(const From &Val)
Definition: Casting.h:74
static bool doit(const From *Val)
Definition: Casting.h:94
static bool doit(const From &Val)
Definition: Casting.h:68
std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type cast(const Y &Val)
Definition: Casting.h:221
static cast_retty< To, From >::ret_type doit(From &Val)
Definition: Casting.h:190
static bool doit(const From *Val)
Definition: Casting.h:101
simplify_type< From >::SimpleType NonConstSimpleType
Definition: Casting.h:40
static bool doit(const From &Val)
Definition: Casting.h:111
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang","erlang-compatible garbage collector")
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast_or_null(const Y &Val)
Definition: Casting.h:308
static bool doit(const From &Val)
Definition: Casting.h:55
add_lvalue_reference_if_not_pointer< SimpleType >::type RetType
Definition: Casting.h:44
LLVM_NODISCARD bool isa(const Y &Val)
Definition: Casting.h:131
static bool doit(const FromTy &Val)
Definition: Casting.h:121
add_const_past_pointer< NonConstSimpleType >::type SimpleType
Definition: Casting.h:42
cast_retty_wrap< To, From, typename simplify_type< From >::SimpleType >::ret_type ret_type
Definition: Casting.h:182
cast_retty_impl< To, FromTy >::ret_type ret_type
Definition: Casting.h:176
cast_retty< To, SimpleFrom >::ret_type ret_type
Definition: Casting.h:170
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:287
static SimpleType & getSimplifiedValue(From &Val)
Definition: Casting.h:36
#define LLVM_NODISCARD
LLVM_NODISCARD - Warn if a type or return value is discarded.
Definition: Compiler.h:132
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
aarch64 promote const
static GCMetadataPrinterRegistry::Add< OcamlGCMetadataPrinter > Y("ocaml","ocaml 3.10-compatible collector")
static const bool value
Definition: Casting.h:207
static bool doit(const From *Val)
Definition: Casting.h:80