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" 19 #include "llvm/Support/type_traits.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> { 42 using NonConstSimpleType = typename simplify_type<From>::SimpleType; 43 using SimpleType = 44 typename add_const_past_pointer<NonConstSimpleType>::type; 45 using RetType = 46 typename add_lvalue_reference_if_not_pointer<SimpleType>::type; 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> 119 struct isa_impl_wrap { 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, 124 typename simplify_type<SimpleFrom>::SimpleType>::doit( 125 simplify_type<const From>::getSimplifiedValue(Val)); 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> 185 struct cast_retty_wrap { 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. 189 using ret_type = typename cast_retty<To, SimpleFrom>::ret_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. 195 using ret_type = typename cast_retty_impl<To,FromTy>::ret_type; 196 }; 197 198 template<class To, class From> 199 struct cast_retty { 200 using ret_type = typename cast_retty_wrap< 201 To, From, typename simplify_type<From>::SimpleType>::ret_type; 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, 211 typename simplify_type<SimpleFrom>::SimpleType>::doit( 212 simplify_type<From>::getSimplifiedValue(Val)); 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) { 219 typename cast_retty<To, FromTy>::ret_type Res2 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( 266 cast_convert_val<X, Y *, typename simplify_type<Y *>::SimpleType>::doit( 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> 296 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type 297 cast_or_null(Y *Val) { 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> 328 LLVM_NODISCARD inline typename cast_retty<X, Y>::ret_type dyn_cast(Y &Val) { 329 return isa<X>(Val) ? cast<X>(Val) : nullptr; 330 } 331 332 template <class X, class Y> 333 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type dyn_cast(Y *Val) { 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 352 dyn_cast_or_null(Y &Val) { 353 return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr; 354 } 355 356 template <class X, class Y> 357 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type 358 dyn_cast_or_null(Y *Val) { 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 400
