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 24namespace 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// 34template<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 41template<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. 56template <typename To, typename From, typename Enabler = void> 57struct 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. 64template <typename To, typename From> 65struct 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 70template <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 76template <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 82template <typename To, typename From> 83struct 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 90template <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 97template <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 104template <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 111template <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 118template<typename To, typename From, typename SimpleFrom> 119struct 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 129template<typename To, typename FromTy> 130struct 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// 142template <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 151template<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. 155template<class To, class From> struct cast_retty_impl { 156 using ret_type = To &; // Normal case, return Ty& 157}; 158template<class To, class From> struct cast_retty_impl<To, const From> { 159 using ret_type = const To &; // Normal case, return Ty& 160}; 161 162template<class To, class From> struct cast_retty_impl<To, From*> { 163 using ret_type = To *; // Pointer arg case, return Ty* 164}; 165 166template<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 170template<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 174template <class To, class From> 175struct cast_retty_impl<To, std::unique_ptr<From>> { 176private: 177 using PointerType = typename cast_retty_impl<To, From *>::ret_type; 178 using ResultType = typename std::remove_pointer<PointerType>::type; 179 180public: 181 using ret_type = std::unique_ptr<ResultType>; 182}; 183 184template<class To, class From, class SimpleFrom> 185struct 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 192template<class To, class FromTy> 193struct 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 198template<class To, class From> 199struct 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// 207template<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 216template<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 225template <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// 237template <class X, class Y> 238inline typename std::enable_if<!is_simple_type<Y>::value, 239 typename cast_retty<X, const Y>::ret_type>::type 240cast(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 246template <class X, class Y> 247inline 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 253template <class X, class Y> 254inline 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 260template <class X, class Y> 261inline typename cast_retty<X, std::unique_ptr<Y>>::ret_type 262cast(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// 273template <class X, class Y> 274LLVM_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 284template <class X, class Y> 285LLVM_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 295template <class X, class Y> 296LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type 297cast_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 303template <class X, class Y> 304inline typename cast_retty<X, std::unique_ptr<Y>>::ret_type 305cast_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 319template <class X, class Y> 320LLVM_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 327template <class X, class Y> 328LLVM_NODISCARD inline typename cast_retty<X, Y>::ret_type dyn_cast(Y &Val) { 329 return isa<X>(Val) ? cast<X>(Val) : nullptr; 330} 331 332template <class X, class Y> 333LLVM_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// 340template <class X, class Y> 341LLVM_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 348template <class X, class Y> 349LLVM_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 356template <class X, class Y> 357LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type 358dyn_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. 367template <class X, class Y> 368LLVM_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 375template <class X, class Y> 376LLVM_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. 383template <class X, class Y> 384LLVM_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 391template <class X, class Y> 392LLVM_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