1 //===- llvm/Support/Casting.h - Allow flexible, checked, casts --*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file defines the isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(), 10 // and dyn_cast_or_null<X>() templates. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_SUPPORT_CASTING_H 15 #define LLVM_SUPPORT_CASTING_H 16 17 #include "llvm/Support/Compiler.h" 18 #include "llvm/Support/type_traits.h" 19 #include <cassert> 20 #include <memory> 21 #include <type_traits> 22 23 namespace llvm { 24 25 //===----------------------------------------------------------------------===// 26 // isa<x> Support Templates 27 //===----------------------------------------------------------------------===// 28 29 // Define a template that can be specialized by smart pointers to reflect the 30 // fact that they are automatically dereferenced, and are not involved with the 31 // template selection process... the default implementation is a noop. 32 // 33 template<typename From> struct simplify_type { 34 using SimpleType = From; // The real type this represents... 35 36 // An accessor to get the real value... 37 static SimpleType &getSimplifiedValue(From &Val) { return Val; } 38 }; 39 40 template<typename From> struct simplify_type<const From> { 41 using NonConstSimpleType = typename simplify_type<From>::SimpleType; 42 using SimpleType = 43 typename add_const_past_pointer<NonConstSimpleType>::type; 44 using RetType = 45 typename add_lvalue_reference_if_not_pointer<SimpleType>::type; 46 47 static RetType getSimplifiedValue(const From& Val) { 48 return simplify_type<From>::getSimplifiedValue(const_cast<From&>(Val)); 49 } 50 }; 51 52 // The core of the implementation of isa<X> is here; To and From should be 53 // the names of classes. This template can be specialized to customize the 54 // implementation of isa<> without rewriting it from scratch. 55 template <typename To, typename From, typename Enabler = void> 56 struct isa_impl { 57 static inline bool doit(const From &Val) { 58 return To::classof(&Val); 59 } 60 }; 61 62 /// Always allow upcasts, and perform no dynamic check for them. 63 template <typename To, typename From> 64 struct isa_impl< 65 To, From, typename std::enable_if<std::is_base_of<To, From>::value>::type> { 66 static inline bool doit(const From &) { return true; } 67 }; 68 69 template <typename To, typename From> struct isa_impl_cl { 70 static inline bool doit(const From &Val) { 71 return isa_impl<To, From>::doit(Val); 72 } 73 }; 74 75 template <typename To, typename From> struct isa_impl_cl<To, const From> { 76 static inline bool doit(const From &Val) { 77 return isa_impl<To, From>::doit(Val); 78 } 79 }; 80 81 template <typename To, typename From> 82 struct isa_impl_cl<To, const std::unique_ptr<From>> { 83 static inline bool doit(const std::unique_ptr<From> &Val) { 84 assert(Val && "isa<> used on a null pointer"); 85 return isa_impl_cl<To, From>::doit(*Val); 86 } 87 }; 88 89 template <typename To, typename From> struct isa_impl_cl<To, From*> { 90 static inline bool doit(const From *Val) { 91 assert(Val && "isa<> used on a null pointer"); 92 return isa_impl<To, From>::doit(*Val); 93 } 94 }; 95 96 template <typename To, typename From> struct isa_impl_cl<To, From*const> { 97 static inline bool doit(const From *Val) { 98 assert(Val && "isa<> used on a null pointer"); 99 return isa_impl<To, From>::doit(*Val); 100 } 101 }; 102 103 template <typename To, typename From> struct isa_impl_cl<To, const From*> { 104 static inline bool doit(const From *Val) { 105 assert(Val && "isa<> used on a null pointer"); 106 return isa_impl<To, From>::doit(*Val); 107 } 108 }; 109 110 template <typename To, typename From> struct isa_impl_cl<To, const From*const> { 111 static inline bool doit(const From *Val) { 112 assert(Val && "isa<> used on a null pointer"); 113 return isa_impl<To, From>::doit(*Val); 114 } 115 }; 116 117 template<typename To, typename From, typename SimpleFrom> 118 struct isa_impl_wrap { 119 // When From != SimplifiedType, we can simplify the type some more by using 120 // the simplify_type template. 121 static bool doit(const From &Val) { 122 return isa_impl_wrap<To, SimpleFrom, 123 typename simplify_type<SimpleFrom>::SimpleType>::doit( 124 simplify_type<const From>::getSimplifiedValue(Val)); 125 } 126 }; 127 128 template<typename To, typename FromTy> 129 struct isa_impl_wrap<To, FromTy, FromTy> { 130 // When From == SimpleType, we are as simple as we are going to get. 131 static bool doit(const FromTy &Val) { 132 return isa_impl_cl<To,FromTy>::doit(Val); 133 } 134 }; 135 136 // isa<X> - Return true if the parameter to the template is an instance of the 137 // template type argument. Used like this: 138 // 139 // if (isa<Type>(myVal)) { ... } 140 // 141 template <class X, class Y> LLVM_NODISCARD inline bool isa(const Y &Val) { 142 return isa_impl_wrap<X, const Y, 143 typename simplify_type<const Y>::SimpleType>::doit(Val); 144 } 145 146 // isa_and_nonnull<X> - Functionally identical to isa, except that a null value 147 // is accepted. 148 // 149 template <class X, class Y> 150 LLVM_NODISCARD inline bool isa_and_nonnull(const Y &Val) { 151 if (!Val) 152 return false; 153 return isa<X>(Val); 154 } 155 156 //===----------------------------------------------------------------------===// 157 // cast<x> Support Templates 158 //===----------------------------------------------------------------------===// 159 160 template<class To, class From> struct cast_retty; 161 162 // Calculate what type the 'cast' function should return, based on a requested 163 // type of To and a source type of From. 164 template<class To, class From> struct cast_retty_impl { 165 using ret_type = To &; // Normal case, return Ty& 166 }; 167 template<class To, class From> struct cast_retty_impl<To, const From> { 168 using ret_type = const To &; // Normal case, return Ty& 169 }; 170 171 template<class To, class From> struct cast_retty_impl<To, From*> { 172 using ret_type = To *; // Pointer arg case, return Ty* 173 }; 174 175 template<class To, class From> struct cast_retty_impl<To, const From*> { 176 using ret_type = const To *; // Constant pointer arg case, return const Ty* 177 }; 178 179 template<class To, class From> struct cast_retty_impl<To, const From*const> { 180 using ret_type = const To *; // Constant pointer arg case, return const Ty* 181 }; 182 183 template <class To, class From> 184 struct cast_retty_impl<To, std::unique_ptr<From>> { 185 private: 186 using PointerType = typename cast_retty_impl<To, From *>::ret_type; 187 using ResultType = typename std::remove_pointer<PointerType>::type; 188 189 public: 190 using ret_type = std::unique_ptr<ResultType>; 191 }; 192 193 template<class To, class From, class SimpleFrom> 194 struct cast_retty_wrap { 195 // When the simplified type and the from type are not the same, use the type 196 // simplifier to reduce the type, then reuse cast_retty_impl to get the 197 // resultant type. 198 using ret_type = typename cast_retty<To, SimpleFrom>::ret_type; 199 }; 200 201 template<class To, class FromTy> 202 struct cast_retty_wrap<To, FromTy, FromTy> { 203 // When the simplified type is equal to the from type, use it directly. 204 using ret_type = typename cast_retty_impl<To,FromTy>::ret_type; 205 }; 206 207 template<class To, class From> 208 struct cast_retty { 209 using ret_type = typename cast_retty_wrap< 210 To, From, typename simplify_type<From>::SimpleType>::ret_type; 211 }; 212 213 // Ensure the non-simple values are converted using the simplify_type template 214 // that may be specialized by smart pointers... 215 // 216 template<class To, class From, class SimpleFrom> struct cast_convert_val { 217 // This is not a simple type, use the template to simplify it... 218 static typename cast_retty<To, From>::ret_type doit(From &Val) { 219 return cast_convert_val<To, SimpleFrom, 220 typename simplify_type<SimpleFrom>::SimpleType>::doit( 221 simplify_type<From>::getSimplifiedValue(Val)); 222 } 223 }; 224 225 template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> { 226 // This _is_ a simple type, just cast it. 227 static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) { 228 typename cast_retty<To, FromTy>::ret_type Res2 229 = (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val); 230 return Res2; 231 } 232 }; 233 234 template <class X> struct is_simple_type { 235 static const bool value = 236 std::is_same<X, typename simplify_type<X>::SimpleType>::value; 237 }; 238 239 // cast<X> - Return the argument parameter cast to the specified type. This 240 // casting operator asserts that the type is correct, so it does not return null 241 // on failure. It does not allow a null argument (use cast_or_null for that). 242 // It is typically used like this: 243 // 244 // cast<Instruction>(myVal)->getParent() 245 // 246 template <class X, class Y> 247 inline typename std::enable_if<!is_simple_type<Y>::value, 248 typename cast_retty<X, const Y>::ret_type>::type 249 cast(const Y &Val) { 250 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!"); 251 return cast_convert_val< 252 X, const Y, typename simplify_type<const Y>::SimpleType>::doit(Val); 253 } 254 255 template <class X, class Y> 256 inline typename cast_retty<X, Y>::ret_type cast(Y &Val) { 257 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!"); 258 return cast_convert_val<X, Y, 259 typename simplify_type<Y>::SimpleType>::doit(Val); 260 } 261 262 template <class X, class Y> 263 inline typename cast_retty<X, Y *>::ret_type cast(Y *Val) { 264 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!"); 265 return cast_convert_val<X, Y*, 266 typename simplify_type<Y*>::SimpleType>::doit(Val); 267 } 268 269 template <class X, class Y> 270 inline typename cast_retty<X, std::unique_ptr<Y>>::ret_type 271 cast(std::unique_ptr<Y> &&Val) { 272 assert(isa<X>(Val.get()) && "cast<Ty>() argument of incompatible type!"); 273 using ret_type = typename cast_retty<X, std::unique_ptr<Y>>::ret_type; 274 return ret_type( 275 cast_convert_val<X, Y *, typename simplify_type<Y *>::SimpleType>::doit( 276 Val.release())); 277 } 278 279 // cast_or_null<X> - Functionally identical to cast, except that a null value is 280 // accepted. 281 // 282 template <class X, class Y> 283 LLVM_NODISCARD inline 284 typename std::enable_if<!is_simple_type<Y>::value, 285 typename cast_retty<X, const Y>::ret_type>::type 286 cast_or_null(const Y &Val) { 287 if (!Val) 288 return nullptr; 289 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!"); 290 return cast<X>(Val); 291 } 292 293 template <class X, class Y> 294 LLVM_NODISCARD inline 295 typename std::enable_if<!is_simple_type<Y>::value, 296 typename cast_retty<X, Y>::ret_type>::type 297 cast_or_null(Y &Val) { 298 if (!Val) 299 return nullptr; 300 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!"); 301 return cast<X>(Val); 302 } 303 304 template <class X, class Y> 305 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type 306 cast_or_null(Y *Val) { 307 if (!Val) return nullptr; 308 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!"); 309 return cast<X>(Val); 310 } 311 312 template <class X, class Y> 313 inline typename cast_retty<X, std::unique_ptr<Y>>::ret_type 314 cast_or_null(std::unique_ptr<Y> &&Val) { 315 if (!Val) 316 return nullptr; 317 return cast<X>(std::move(Val)); 318 } 319 320 // dyn_cast<X> - Return the argument parameter cast to the specified type. This 321 // casting operator returns null if the argument is of the wrong type, so it can 322 // be used to test for a type as well as cast if successful. This should be 323 // used in the context of an if statement like this: 324 // 325 // if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... } 326 // 327 328 template <class X, class Y> 329 LLVM_NODISCARD inline 330 typename std::enable_if<!is_simple_type<Y>::value, 331 typename cast_retty<X, const Y>::ret_type>::type 332 dyn_cast(const Y &Val) { 333 return isa<X>(Val) ? cast<X>(Val) : nullptr; 334 } 335 336 template <class X, class Y> 337 LLVM_NODISCARD inline typename cast_retty<X, Y>::ret_type dyn_cast(Y &Val) { 338 return isa<X>(Val) ? cast<X>(Val) : nullptr; 339 } 340 341 template <class X, class Y> 342 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type dyn_cast(Y *Val) { 343 return isa<X>(Val) ? cast<X>(Val) : nullptr; 344 } 345 346 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null 347 // value is accepted. 348 // 349 template <class X, class Y> 350 LLVM_NODISCARD inline 351 typename std::enable_if<!is_simple_type<Y>::value, 352 typename cast_retty<X, const Y>::ret_type>::type 353 dyn_cast_or_null(const Y &Val) { 354 return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr; 355 } 356 357 template <class X, class Y> 358 LLVM_NODISCARD inline 359 typename std::enable_if<!is_simple_type<Y>::value, 360 typename cast_retty<X, Y>::ret_type>::type 361 dyn_cast_or_null(Y &Val) { 362 return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr; 363 } 364 365 template <class X, class Y> 366 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type 367 dyn_cast_or_null(Y *Val) { 368 return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr; 369 } 370 371 // unique_dyn_cast<X> - Given a unique_ptr<Y>, try to return a unique_ptr<X>, 372 // taking ownership of the input pointer iff isa<X>(Val) is true. If the 373 // cast is successful, From refers to nullptr on exit and the casted value 374 // is returned. If the cast is unsuccessful, the function returns nullptr 375 // and From is unchanged. 376 template <class X, class Y> 377 LLVM_NODISCARD inline auto unique_dyn_cast(std::unique_ptr<Y> &Val) 378 -> decltype(cast<X>(Val)) { 379 if (!isa<X>(Val)) 380 return nullptr; 381 return cast<X>(std::move(Val)); 382 } 383 384 template <class X, class Y> 385 LLVM_NODISCARD inline auto unique_dyn_cast(std::unique_ptr<Y> &&Val) 386 -> decltype(cast<X>(Val)) { 387 return unique_dyn_cast<X, Y>(Val); 388 } 389 390 // dyn_cast_or_null<X> - Functionally identical to unique_dyn_cast, except that 391 // a null value is accepted. 392 template <class X, class Y> 393 LLVM_NODISCARD inline auto unique_dyn_cast_or_null(std::unique_ptr<Y> &Val) 394 -> decltype(cast<X>(Val)) { 395 if (!Val) 396 return nullptr; 397 return unique_dyn_cast<X, Y>(Val); 398 } 399 400 template <class X, class Y> 401 LLVM_NODISCARD inline auto unique_dyn_cast_or_null(std::unique_ptr<Y> &&Val) 402 -> decltype(cast<X>(Val)) { 403 return unique_dyn_cast_or_null<X, Y>(Val); 404 } 405 406 } // end namespace llvm 407 408 #endif // LLVM_SUPPORT_CASTING_H 409