include/llvm/Support/Casting.h

   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