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/type_traits.h" 19 #include <cassert> 20 21 namespace llvm { 22 23 //===----------------------------------------------------------------------===// 24 // isa<x> Support Templates 25 //===----------------------------------------------------------------------===// 26 27 // Define a template that can be specialized by smart pointers to reflect the 28 // fact that they are automatically dereferenced, and are not involved with the 29 // template selection process... the default implementation is a noop. 30 // 31 template<typename From> struct simplify_type { 32 typedef From SimpleType; // The real type this represents... 33 34 // An accessor to get the real value... getSimplifiedValuesimplify_type35 static SimpleType &getSimplifiedValue(From &Val) { return Val; } 36 }; 37 38 template<typename From> struct simplify_type<const From> { 39 typedef const From SimpleType; 40 static SimpleType &getSimplifiedValue(const From &Val) { 41 return simplify_type<From>::getSimplifiedValue(static_cast<From&>(Val)); 42 } 43 }; 44 45 // The core of the implementation of isa<X> is here; To and From should be 46 // the names of classes. This template can be specialized to customize the 47 // implementation of isa<> without rewriting it from scratch. 48 template <typename To, typename From, typename Enabler = void> 49 struct isa_impl { 50 static inline bool doit(const From &Val) { 51 return To::classof(&Val); 52 } 53 }; 54 55 /// \brief Always allow upcasts, and perform no dynamic check for them. 56 template <typename To, typename From> 57 struct isa_impl<To, From, 58 typename enable_if< 59 llvm::is_base_of<To, From> 60 >::type 61 > { 62 static inline bool doit(const From &) { return true; } 63 }; 64 65 template <typename To, typename From> struct isa_impl_cl { 66 static inline bool doit(const From &Val) { 67 return isa_impl<To, From>::doit(Val); 68 } 69 }; 70 71 template <typename To, typename From> struct isa_impl_cl<To, const From> { 72 static inline bool doit(const From &Val) { 73 return isa_impl<To, From>::doit(Val); 74 } 75 }; 76 77 template <typename To, typename From> struct isa_impl_cl<To, From*> { 78 static inline bool doit(const From *Val) { 79 assert(Val && "isa<> used on a null pointer"); 80 return isa_impl<To, From>::doit(*Val); 81 } 82 }; 83 84 template <typename To, typename From> struct isa_impl_cl<To, const From*> { 85 static inline bool doit(const From *Val) { 86 assert(Val && "isa<> used on a null pointer"); 87 return isa_impl<To, From>::doit(*Val); 88 } 89 }; 90 91 template <typename To, typename From> struct isa_impl_cl<To, const From*const> { 92 static inline bool doit(const From *Val) { 93 assert(Val && "isa<> used on a null pointer"); 94 return isa_impl<To, From>::doit(*Val); 95 } 96 }; 97 98 template<typename To, typename From, typename SimpleFrom> 99 struct isa_impl_wrap { 100 // When From != SimplifiedType, we can simplify the type some more by using 101 // the simplify_type template. 102 static bool doit(const From &Val) { 103 return isa_impl_wrap<To, SimpleFrom, 104 typename simplify_type<SimpleFrom>::SimpleType>::doit( 105 simplify_type<From>::getSimplifiedValue(Val)); 106 } 107 }; 108 109 template<typename To, typename FromTy> 110 struct isa_impl_wrap<To, FromTy, FromTy> { 111 // When From == SimpleType, we are as simple as we are going to get. 112 static bool doit(const FromTy &Val) { 113 return isa_impl_cl<To,FromTy>::doit(Val); 114 } 115 }; 116 117 // isa<X> - Return true if the parameter to the template is an instance of the 118 // template type argument. Used like this: 119 // 120 // if (isa<Type>(myVal)) { ... } 121 // 122 template <class X, class Y> 123 inline bool isa(const Y &Val) { 124 return isa_impl_wrap<X, Y, typename simplify_type<Y>::SimpleType>::doit(Val); 125 } 126 127 //===----------------------------------------------------------------------===// 128 // cast<x> Support Templates 129 //===----------------------------------------------------------------------===// 130 131 template<class To, class From> struct cast_retty; 132 133 134 // Calculate what type the 'cast' function should return, based on a requested 135 // type of To and a source type of From. 136 template<class To, class From> struct cast_retty_impl { 137 typedef To& ret_type; // Normal case, return Ty& 138 }; 139 template<class To, class From> struct cast_retty_impl<To, const From> { 140 typedef const To &ret_type; // Normal case, return Ty& 141 }; 142 143 template<class To, class From> struct cast_retty_impl<To, From*> { 144 typedef To* ret_type; // Pointer arg case, return Ty* 145 }; 146 147 template<class To, class From> struct cast_retty_impl<To, const From*> { 148 typedef const To* ret_type; // Constant pointer arg case, return const Ty* 149 }; 150 151 template<class To, class From> struct cast_retty_impl<To, const From*const> { 152 typedef const To* ret_type; // Constant pointer arg case, return const Ty* 153 }; 154 155 156 template<class To, class From, class SimpleFrom> 157 struct cast_retty_wrap { 158 // When the simplified type and the from type are not the same, use the type 159 // simplifier to reduce the type, then reuse cast_retty_impl to get the 160 // resultant type. 161 typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type; 162 }; 163 164 template<class To, class FromTy> 165 struct cast_retty_wrap<To, FromTy, FromTy> { 166 // When the simplified type is equal to the from type, use it directly. 167 typedef typename cast_retty_impl<To,FromTy>::ret_type ret_type; 168 }; 169 170 template<class To, class From> 171 struct cast_retty { 172 typedef typename cast_retty_wrap<To, From, 173 typename simplify_type<From>::SimpleType>::ret_type ret_type; 174 }; 175 176 // Ensure the non-simple values are converted using the simplify_type template 177 // that may be specialized by smart pointers... 178 // 179 template<class To, class From, class SimpleFrom> struct cast_convert_val { 180 // This is not a simple type, use the template to simplify it... 181 static typename cast_retty<To, From>::ret_type doit(const From &Val) { 182 return cast_convert_val<To, SimpleFrom, 183 typename simplify_type<SimpleFrom>::SimpleType>::doit( 184 simplify_type<From>::getSimplifiedValue(Val)); 185 } 186 }; 187 188 template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> { 189 // This _is_ a simple type, just cast it. 190 static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) { 191 typename cast_retty<To, FromTy>::ret_type Res2 192 = (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val); 193 return Res2; 194 } 195 }; 196 197 198 199 // cast<X> - Return the argument parameter cast to the specified type. This 200 // casting operator asserts that the type is correct, so it does not return null 201 // on failure. It does not allow a null argument (use cast_or_null for that). 202 // It is typically used like this: 203 // 204 // cast<Instruction>(myVal)->getParent() 205 // 206 template <class X, class Y> 207 inline typename enable_if_c< 208 !is_same<Y, typename simplify_type<Y>::SimpleType>::value, 209 typename cast_retty<X, Y>::ret_type 210 >::type cast(const Y &Val) { 211 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!"); 212 return cast_convert_val<X, Y, 213 typename simplify_type<Y>::SimpleType>::doit(Val); 214 } 215 216 template <class X, class Y> 217 inline typename enable_if< 218 is_same<Y, typename simplify_type<Y>::SimpleType>, 219 typename cast_retty<X, Y>::ret_type 220 >::type cast(Y &Val) { 221 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!"); 222 return cast_convert_val<X, Y, 223 typename simplify_type<Y>::SimpleType>::doit(Val); 224 } 225 226 template <class X, class Y> 227 inline typename enable_if< 228 is_same<Y, typename simplify_type<Y>::SimpleType>, 229 typename cast_retty<X, Y*>::ret_type 230 >::type cast(Y *Val) { 231 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!"); 232 return cast_convert_val<X, Y*, 233 typename simplify_type<Y*>::SimpleType>::doit(Val); 234 } 235 236 // cast_or_null<X> - Functionally identical to cast, except that a null value is 237 // accepted. 238 // 239 template <class X, class Y> 240 inline typename cast_retty<X, Y*>::ret_type cast_or_null(Y *Val) { 241 if (Val == 0) return 0; 242 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!"); 243 return cast<X>(Val); 244 } 245 246 247 // dyn_cast<X> - Return the argument parameter cast to the specified type. This 248 // casting operator returns null if the argument is of the wrong type, so it can 249 // be used to test for a type as well as cast if successful. This should be 250 // used in the context of an if statement like this: 251 // 252 // if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... } 253 // 254 255 template <class X, class Y> 256 inline typename enable_if_c< 257 !is_same<Y, typename simplify_type<Y>::SimpleType>::value, 258 typename cast_retty<X, Y>::ret_type 259 >::type dyn_cast(const Y &Val) { 260 return isa<X>(Val) ? cast<X>(Val) : 0; 261 } 262 263 template <class X, class Y> 264 inline typename enable_if< 265 is_same<Y, typename simplify_type<Y>::SimpleType>, 266 typename cast_retty<X, Y>::ret_type 267 >::type dyn_cast(Y &Val) { 268 return isa<X>(Val) ? cast<X>(Val) : 0; 269 } 270 271 template <class X, class Y> 272 inline typename enable_if< 273 is_same<Y, typename simplify_type<Y>::SimpleType>, 274 typename cast_retty<X, Y*>::ret_type 275 >::type dyn_cast(Y *Val) { 276 return isa<X>(Val) ? cast<X>(Val) : 0; 277 } 278 279 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null 280 // value is accepted. 281 // 282 template <class X, class Y> 283 inline typename cast_retty<X, Y*>::ret_type dyn_cast_or_null(Y *Val) { 284 return (Val && isa<X>(Val)) ? cast<X>(Val) : 0; 285 } 286 287 } // End llvm namespace 288 289 #endif 290