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... 35 static SimpleType &getSimplifiedValue(From &Val) { return Val; } 36 }; 37 38 template<typename From> struct simplify_type<const From> { 39 typedef typename simplify_type<From>::SimpleType NonConstSimpleType; 40 typedef typename add_const_past_pointer<NonConstSimpleType>::type 41 SimpleType; 42 typedef typename add_lvalue_reference_if_not_pointer<SimpleType>::type 43 RetType; 44 static RetType getSimplifiedValue(const From& Val) { 45 return simplify_type<From>::getSimplifiedValue(const_cast<From&>(Val)); 46 } 47 }; 48 49 // The core of the implementation of isa<X> is here; To and From should be 50 // the names of classes. This template can be specialized to customize the 51 // implementation of isa<> without rewriting it from scratch. 52 template <typename To, typename From, typename Enabler = void> 53 struct isa_impl { 54 static inline bool doit(const From &Val) { 55 return To::classof(&Val); 56 } 57 }; 58 59 /// \brief Always allow upcasts, and perform no dynamic check for them. 60 template <typename To, typename From> 61 struct isa_impl<To, From, 62 typename enable_if< 63 llvm::is_base_of<To, From> 64 >::type 65 > { 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> struct isa_impl_cl<To, From*> { 82 static inline bool doit(const From *Val) { 83 assert(Val && "isa<> used on a null pointer"); 84 return isa_impl<To, From>::doit(*Val); 85 } 86 }; 87 88 template <typename To, typename From> struct isa_impl_cl<To, From*const> { 89 static inline bool doit(const From *Val) { 90 assert(Val && "isa<> used on a null pointer"); 91 return isa_impl<To, From>::doit(*Val); 92 } 93 }; 94 95 template <typename To, typename From> struct isa_impl_cl<To, const From*> { 96 static inline bool doit(const From *Val) { 97 assert(Val && "isa<> used on a null pointer"); 98 return isa_impl<To, From>::doit(*Val); 99 } 100 }; 101 102 template <typename To, typename From> struct isa_impl_cl<To, const From*const> { 103 static inline bool doit(const From *Val) { 104 assert(Val && "isa<> used on a null pointer"); 105 return isa_impl<To, From>::doit(*Val); 106 } 107 }; 108 109 template<typename To, typename From, typename SimpleFrom> 110 struct isa_impl_wrap { 111 // When From != SimplifiedType, we can simplify the type some more by using 112 // the simplify_type template. 113 static bool doit(const From &Val) { 114 return isa_impl_wrap<To, SimpleFrom, 115 typename simplify_type<SimpleFrom>::SimpleType>::doit( 116 simplify_type<const From>::getSimplifiedValue(Val)); 117 } 118 }; 119 120 template<typename To, typename FromTy> 121 struct isa_impl_wrap<To, FromTy, FromTy> { 122 // When From == SimpleType, we are as simple as we are going to get. 123 static bool doit(const FromTy &Val) { 124 return isa_impl_cl<To,FromTy>::doit(Val); 125 } 126 }; 127 128 // isa<X> - Return true if the parameter to the template is an instance of the 129 // template type argument. Used like this: 130 // 131 // if (isa<Type>(myVal)) { ... } 132 // 133 template <class X, class Y> 134 inline bool isa(const Y &Val) { 135 return isa_impl_wrap<X, const Y, 136 typename simplify_type<const Y>::SimpleType>::doit(Val); 137 } 138 139 //===----------------------------------------------------------------------===// 140 // cast<x> Support Templates 141 //===----------------------------------------------------------------------===// 142 143 template<class To, class From> struct cast_retty; 144 145 146 // Calculate what type the 'cast' function should return, based on a requested 147 // type of To and a source type of From. 148 template<class To, class From> struct cast_retty_impl { 149 typedef To& ret_type; // Normal case, return Ty& 150 }; 151 template<class To, class From> struct cast_retty_impl<To, const From> { 152 typedef const To &ret_type; // Normal case, return Ty& 153 }; 154 155 template<class To, class From> struct cast_retty_impl<To, From*> { 156 typedef To* ret_type; // Pointer arg case, return Ty* 157 }; 158 159 template<class To, class From> struct cast_retty_impl<To, const From*> { 160 typedef const To* ret_type; // Constant pointer arg case, return const Ty* 161 }; 162 163 template<class To, class From> struct cast_retty_impl<To, const From*const> { 164 typedef const To* ret_type; // Constant pointer arg case, return const Ty* 165 }; 166 167 168 template<class To, class From, class SimpleFrom> 169 struct cast_retty_wrap { 170 // When the simplified type and the from type are not the same, use the type 171 // simplifier to reduce the type, then reuse cast_retty_impl to get the 172 // resultant type. 173 typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type; 174 }; 175 176 template<class To, class FromTy> 177 struct cast_retty_wrap<To, FromTy, FromTy> { 178 // When the simplified type is equal to the from type, use it directly. 179 typedef typename cast_retty_impl<To,FromTy>::ret_type ret_type; 180 }; 181 182 template<class To, class From> 183 struct cast_retty { 184 typedef typename cast_retty_wrap<To, From, 185 typename simplify_type<From>::SimpleType>::ret_type ret_type; 186 }; 187 188 // Ensure the non-simple values are converted using the simplify_type template 189 // that may be specialized by smart pointers... 190 // 191 template<class To, class From, class SimpleFrom> struct cast_convert_val { 192 // This is not a simple type, use the template to simplify it... 193 static typename cast_retty<To, From>::ret_type doit(From &Val) { 194 return cast_convert_val<To, SimpleFrom, 195 typename simplify_type<SimpleFrom>::SimpleType>::doit( 196 simplify_type<From>::getSimplifiedValue(Val)); 197 } 198 }; 199 200 template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> { 201 // This _is_ a simple type, just cast it. 202 static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) { 203 typename cast_retty<To, FromTy>::ret_type Res2 204 = (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val); 205 return Res2; 206 } 207 }; 208 209 template <class X> struct is_simple_type { 210 static const bool value = 211 is_same<X, typename simplify_type<X>::SimpleType>::value; 212 }; 213 214 // cast<X> - Return the argument parameter cast to the specified type. This 215 // casting operator asserts that the type is correct, so it does not return null 216 // on failure. It does not allow a null argument (use cast_or_null for that). 217 // It is typically used like this: 218 // 219 // cast<Instruction>(myVal)->getParent() 220 // 221 template <class X, class Y> 222 inline typename enable_if_c<!is_simple_type<Y>::value, 223 typename cast_retty<X, const Y>::ret_type>::type 224 cast(const Y &Val) { 225 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!"); 226 return cast_convert_val< 227 X, const Y, typename simplify_type<const Y>::SimpleType>::doit(Val); 228 } 229 230 template <class X, class Y> 231 inline typename cast_retty<X, Y>::ret_type cast(Y &Val) { 232 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!"); 233 return cast_convert_val<X, Y, 234 typename simplify_type<Y>::SimpleType>::doit(Val); 235 } 236 237 template <class X, class Y> 238 inline typename cast_retty<X, Y *>::ret_type cast(Y *Val) { 239 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!"); 240 return cast_convert_val<X, Y*, 241 typename simplify_type<Y*>::SimpleType>::doit(Val); 242 } 243 244 // cast_or_null<X> - Functionally identical to cast, except that a null value is 245 // accepted. 246 // 247 template <class X, class Y> 248 inline typename cast_retty<X, Y*>::ret_type cast_or_null(Y *Val) { 249 if (Val == 0) return 0; 250 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!"); 251 return cast<X>(Val); 252 } 253 254 255 // dyn_cast<X> - Return the argument parameter cast to the specified type. This 256 // casting operator returns null if the argument is of the wrong type, so it can 257 // be used to test for a type as well as cast if successful. This should be 258 // used in the context of an if statement like this: 259 // 260 // if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... } 261 // 262 263 template <class X, class Y> 264 inline typename enable_if_c<!is_simple_type<Y>::value, 265 typename cast_retty<X, const Y>::ret_type>::type 266 dyn_cast(const Y &Val) { 267 return isa<X>(Val) ? cast<X>(Val) : 0; 268 } 269 270 template <class X, class Y> 271 inline typename cast_retty<X, Y>::ret_type dyn_cast(Y &Val) { 272 return isa<X>(Val) ? cast<X>(Val) : 0; 273 } 274 275 template <class X, class Y> 276 inline typename cast_retty<X, Y *>::ret_type dyn_cast(Y *Val) { 277 return isa<X>(Val) ? cast<X>(Val) : 0; 278 } 279 280 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null 281 // value is accepted. 282 // 283 template <class X, class Y> 284 inline typename cast_retty<X, Y*>::ret_type dyn_cast_or_null(Y *Val) { 285 return (Val && isa<X>(Val)) ? cast<X>(Val) : 0; 286 } 287 288 } // End llvm namespace 289 290 #endif 291
