1 //===-- llvm/Support/Casting.h - Allow flexible, checked, casts -*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(),
11 // and dyn_cast_or_null<X>() templates.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_SUPPORT_CASTING_H
16 #define LLVM_SUPPORT_CASTING_H
18 #include "llvm/Support/Compiler.h"
19 #include "llvm/Support/type_traits.h"
24 //===----------------------------------------------------------------------===//
25 // isa<x> Support Templates
26 //===----------------------------------------------------------------------===//
28 // Define a template that can be specialized by smart pointers to reflect the
29 // fact that they are automatically dereferenced, and are not involved with the
30 // template selection process... the default implementation is a noop.
32 template<typename From> struct simplify_type {
33 typedef From SimpleType; // The real type this represents...
35 // An accessor to get the real value...
36 static SimpleType &getSimplifiedValue(From &Val) { return Val; }
39 template<typename From> struct simplify_type<const From> {
40 typedef typename simplify_type<From>::SimpleType NonConstSimpleType;
41 typedef typename add_const_past_pointer<NonConstSimpleType>::type
43 typedef typename add_lvalue_reference_if_not_pointer<SimpleType>::type
45 static RetType getSimplifiedValue(const From& Val) {
46 return simplify_type<From>::getSimplifiedValue(const_cast<From&>(Val));
50 // The core of the implementation of isa<X> is here; To and From should be
51 // the names of classes. This template can be specialized to customize the
52 // implementation of isa<> without rewriting it from scratch.
53 template <typename To, typename From, typename Enabler = void>
55 static inline bool doit(const From &Val) {
56 return To::classof(&Val);
60 /// \brief Always allow upcasts, and perform no dynamic check for them.
61 template <typename To, typename From>
63 To, From, typename std::enable_if<std::is_base_of<To, From>::value>::type> {
64 static inline bool doit(const From &) { return true; }
67 template <typename To, typename From> struct isa_impl_cl {
68 static inline bool doit(const From &Val) {
69 return isa_impl<To, From>::doit(Val);
73 template <typename To, typename From> struct isa_impl_cl<To, const From> {
74 static inline bool doit(const From &Val) {
75 return isa_impl<To, From>::doit(Val);
79 template <typename To, typename From> struct isa_impl_cl<To, From*> {
80 static inline bool doit(const From *Val) {
81 assert(Val && "isa<> used on a null pointer");
82 return isa_impl<To, From>::doit(*Val);
86 template <typename To, typename From> struct isa_impl_cl<To, From*const> {
87 static inline bool doit(const From *Val) {
88 assert(Val && "isa<> used on a null pointer");
89 return isa_impl<To, From>::doit(*Val);
93 template <typename To, typename From> struct isa_impl_cl<To, const From*> {
94 static inline bool doit(const From *Val) {
95 assert(Val && "isa<> used on a null pointer");
96 return isa_impl<To, From>::doit(*Val);
100 template <typename To, typename From> struct isa_impl_cl<To, const From*const> {
101 static inline bool doit(const From *Val) {
102 assert(Val && "isa<> used on a null pointer");
103 return isa_impl<To, From>::doit(*Val);
107 template<typename To, typename From, typename SimpleFrom>
108 struct isa_impl_wrap {
109 // When From != SimplifiedType, we can simplify the type some more by using
110 // the simplify_type template.
111 static bool doit(const From &Val) {
112 return isa_impl_wrap<To, SimpleFrom,
113 typename simplify_type<SimpleFrom>::SimpleType>::doit(
114 simplify_type<const From>::getSimplifiedValue(Val));
118 template<typename To, typename FromTy>
119 struct isa_impl_wrap<To, FromTy, FromTy> {
120 // When From == SimpleType, we are as simple as we are going to get.
121 static bool doit(const FromTy &Val) {
122 return isa_impl_cl<To,FromTy>::doit(Val);
126 // isa<X> - Return true if the parameter to the template is an instance of the
127 // template type argument. Used like this:
129 // if (isa<Type>(myVal)) { ... }
131 template <class X, class Y> LLVM_NODISCARD inline bool isa(const Y &Val) {
132 return isa_impl_wrap<X, const Y,
133 typename simplify_type<const Y>::SimpleType>::doit(Val);
136 //===----------------------------------------------------------------------===//
137 // cast<x> Support Templates
138 //===----------------------------------------------------------------------===//
140 template<class To, class From> struct cast_retty;
143 // Calculate what type the 'cast' function should return, based on a requested
144 // type of To and a source type of From.
145 template<class To, class From> struct cast_retty_impl {
146 typedef To& ret_type; // Normal case, return Ty&
148 template<class To, class From> struct cast_retty_impl<To, const From> {
149 typedef const To &ret_type; // Normal case, return Ty&
152 template<class To, class From> struct cast_retty_impl<To, From*> {
153 typedef To* ret_type; // Pointer arg case, return Ty*
156 template<class To, class From> struct cast_retty_impl<To, const From*> {
157 typedef const To* ret_type; // Constant pointer arg case, return const Ty*
160 template<class To, class From> struct cast_retty_impl<To, const From*const> {
161 typedef const To* ret_type; // Constant pointer arg case, return const Ty*
165 template<class To, class From, class SimpleFrom>
166 struct cast_retty_wrap {
167 // When the simplified type and the from type are not the same, use the type
168 // simplifier to reduce the type, then reuse cast_retty_impl to get the
170 typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type;
173 template<class To, class FromTy>
174 struct cast_retty_wrap<To, FromTy, FromTy> {
175 // When the simplified type is equal to the from type, use it directly.
176 typedef typename cast_retty_impl<To,FromTy>::ret_type ret_type;
179 template<class To, class From>
181 typedef typename cast_retty_wrap<To, From,
182 typename simplify_type<From>::SimpleType>::ret_type ret_type;
185 // Ensure the non-simple values are converted using the simplify_type template
186 // that may be specialized by smart pointers...
188 template<class To, class From, class SimpleFrom> struct cast_convert_val {
189 // This is not a simple type, use the template to simplify it...
190 static typename cast_retty<To, From>::ret_type doit(From &Val) {
191 return cast_convert_val<To, SimpleFrom,
192 typename simplify_type<SimpleFrom>::SimpleType>::doit(
193 simplify_type<From>::getSimplifiedValue(Val));
197 template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> {
198 // This _is_ a simple type, just cast it.
199 static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
200 typename cast_retty<To, FromTy>::ret_type Res2
201 = (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val);
206 template <class X> struct is_simple_type {
207 static const bool value =
208 std::is_same<X, typename simplify_type<X>::SimpleType>::value;
211 // cast<X> - Return the argument parameter cast to the specified type. This
212 // casting operator asserts that the type is correct, so it does not return null
213 // on failure. It does not allow a null argument (use cast_or_null for that).
214 // It is typically used like this:
216 // cast<Instruction>(myVal)->getParent()
218 template <class X, class Y>
219 inline typename std::enable_if<!is_simple_type<Y>::value,
220 typename cast_retty<X, const Y>::ret_type>::type
222 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
223 return cast_convert_val<
224 X, const Y, typename simplify_type<const Y>::SimpleType>::doit(Val);
227 template <class X, class Y>
228 inline typename cast_retty<X, Y>::ret_type cast(Y &Val) {
229 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
230 return cast_convert_val<X, Y,
231 typename simplify_type<Y>::SimpleType>::doit(Val);
234 template <class X, class Y>
235 inline typename cast_retty<X, Y *>::ret_type cast(Y *Val) {
236 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
237 return cast_convert_val<X, Y*,
238 typename simplify_type<Y*>::SimpleType>::doit(Val);
241 // cast_or_null<X> - Functionally identical to cast, except that a null value is
244 template <class X, class Y>
245 LLVM_NODISCARD inline
246 typename std::enable_if<!is_simple_type<Y>::value,
247 typename cast_retty<X, const Y>::ret_type>::type
248 cast_or_null(const Y &Val) {
251 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
255 template <class X, class Y>
256 LLVM_NODISCARD inline
257 typename std::enable_if<!is_simple_type<Y>::value,
258 typename cast_retty<X, Y>::ret_type>::type
259 cast_or_null(Y &Val) {
262 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
266 template <class X, class Y>
267 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type
268 cast_or_null(Y *Val) {
269 if (!Val) return nullptr;
270 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
275 // dyn_cast<X> - Return the argument parameter cast to the specified type. This
276 // casting operator returns null if the argument is of the wrong type, so it can
277 // be used to test for a type as well as cast if successful. This should be
278 // used in the context of an if statement like this:
280 // if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
283 template <class X, class Y>
284 LLVM_NODISCARD inline
285 typename std::enable_if<!is_simple_type<Y>::value,
286 typename cast_retty<X, const Y>::ret_type>::type
287 dyn_cast(const Y &Val) {
288 return isa<X>(Val) ? cast<X>(Val) : nullptr;
291 template <class X, class Y>
292 LLVM_NODISCARD inline typename cast_retty<X, Y>::ret_type dyn_cast(Y &Val) {
293 return isa<X>(Val) ? cast<X>(Val) : nullptr;
296 template <class X, class Y>
297 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type dyn_cast(Y *Val) {
298 return isa<X>(Val) ? cast<X>(Val) : nullptr;
301 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
302 // value is accepted.
304 template <class X, class Y>
305 LLVM_NODISCARD inline
306 typename std::enable_if<!is_simple_type<Y>::value,
307 typename cast_retty<X, const Y>::ret_type>::type
308 dyn_cast_or_null(const Y &Val) {
309 return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
312 template <class X, class Y>
313 LLVM_NODISCARD inline
314 typename std::enable_if<!is_simple_type<Y>::value,
315 typename cast_retty<X, Y>::ret_type>::type
316 dyn_cast_or_null(Y &Val) {
317 return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
320 template <class X, class Y>
321 LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type
322 dyn_cast_or_null(Y *Val) {
323 return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
326 } // End llvm namespace