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/type_traits.h"
23 //===----------------------------------------------------------------------===//
24 // isa<x> Support Templates
25 //===----------------------------------------------------------------------===//
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.
31 template<typename From> struct simplify_type {
32 typedef From SimpleType; // The real type this represents...
34 // An accessor to get the real value...
35 static SimpleType &getSimplifiedValue(From &Val) { return Val; }
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
42 typedef typename add_lvalue_reference_if_not_pointer<SimpleType>::type
44 static RetType getSimplifiedValue(const From& Val) {
45 return simplify_type<From>::getSimplifiedValue(const_cast<From&>(Val));
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>
54 static inline bool doit(const From &Val) {
55 return To::classof(&Val);
59 /// \brief Always allow upcasts, and perform no dynamic check for them.
60 template <typename To, typename From>
61 struct isa_impl<To, From,
63 llvm::is_base_of<To, From>
66 static inline bool doit(const From &) { return true; }
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);
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);
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);
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);
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);
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);
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));
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);
128 // isa<X> - Return true if the parameter to the template is an instance of the
129 // template type argument. Used like this:
131 // if (isa<Type>(myVal)) { ... }
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);
139 //===----------------------------------------------------------------------===//
140 // cast<x> Support Templates
141 //===----------------------------------------------------------------------===//
143 template<class To, class From> struct cast_retty;
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&
151 template<class To, class From> struct cast_retty_impl<To, const From> {
152 typedef const To &ret_type; // Normal case, return Ty&
155 template<class To, class From> struct cast_retty_impl<To, From*> {
156 typedef To* ret_type; // Pointer arg case, return Ty*
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*
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*
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
173 typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type;
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;
182 template<class To, class From>
184 typedef typename cast_retty_wrap<To, From,
185 typename simplify_type<From>::SimpleType>::ret_type ret_type;
188 // Ensure the non-simple values are converted using the simplify_type template
189 // that may be specialized by smart pointers...
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));
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);
209 template <class X> struct is_simple_type {
210 static const bool value =
211 is_same<X, typename simplify_type<X>::SimpleType>::value;
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:
219 // cast<Instruction>(myVal)->getParent()
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
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);
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);
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);
244 // cast_or_null<X> - Functionally identical to cast, except that a null value is
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!");
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:
260 // if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
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;
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;
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;
280 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
281 // value is accepted.
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;
288 } // End llvm namespace