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>
62 struct isa_impl<To, From,
64 llvm::is_base_of<To, From>
67 static inline bool doit(const From &) { return true; }
70 template <typename To, typename From> struct isa_impl_cl {
71 static inline bool doit(const From &Val) {
72 return isa_impl<To, From>::doit(Val);
76 template <typename To, typename From> struct isa_impl_cl<To, const From> {
77 static inline bool doit(const From &Val) {
78 return isa_impl<To, From>::doit(Val);
82 template <typename To, typename From> struct isa_impl_cl<To, From*> {
83 static inline bool doit(const From *Val) {
84 assert(Val && "isa<> used on a null pointer");
85 return isa_impl<To, From>::doit(*Val);
89 template <typename To, typename From> struct isa_impl_cl<To, From*const> {
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);
96 template <typename To, typename From> struct isa_impl_cl<To, const From*> {
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);
103 template <typename To, typename From> struct isa_impl_cl<To, const From*const> {
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);
110 template<typename To, typename From, typename SimpleFrom>
111 struct isa_impl_wrap {
112 // When From != SimplifiedType, we can simplify the type some more by using
113 // the simplify_type template.
114 static bool doit(const From &Val) {
115 return isa_impl_wrap<To, SimpleFrom,
116 typename simplify_type<SimpleFrom>::SimpleType>::doit(
117 simplify_type<const From>::getSimplifiedValue(Val));
121 template<typename To, typename FromTy>
122 struct isa_impl_wrap<To, FromTy, FromTy> {
123 // When From == SimpleType, we are as simple as we are going to get.
124 static bool doit(const FromTy &Val) {
125 return isa_impl_cl<To,FromTy>::doit(Val);
129 // isa<X> - Return true if the parameter to the template is an instance of the
130 // template type argument. Used like this:
132 // if (isa<Type>(myVal)) { ... }
134 template <class X, class Y>
135 LLVM_ATTRIBUTE_UNUSED_RESULT inline bool isa(const Y &Val) {
136 return isa_impl_wrap<X, const Y,
137 typename simplify_type<const Y>::SimpleType>::doit(Val);
140 //===----------------------------------------------------------------------===//
141 // cast<x> Support Templates
142 //===----------------------------------------------------------------------===//
144 template<class To, class From> struct cast_retty;
147 // Calculate what type the 'cast' function should return, based on a requested
148 // type of To and a source type of From.
149 template<class To, class From> struct cast_retty_impl {
150 typedef To& ret_type; // Normal case, return Ty&
152 template<class To, class From> struct cast_retty_impl<To, const From> {
153 typedef const To &ret_type; // Normal case, return Ty&
156 template<class To, class From> struct cast_retty_impl<To, From*> {
157 typedef To* ret_type; // Pointer arg case, return Ty*
160 template<class To, class From> struct cast_retty_impl<To, const From*> {
161 typedef const To* ret_type; // Constant pointer arg case, return const Ty*
164 template<class To, class From> struct cast_retty_impl<To, const From*const> {
165 typedef const To* ret_type; // Constant pointer arg case, return const Ty*
169 template<class To, class From, class SimpleFrom>
170 struct cast_retty_wrap {
171 // When the simplified type and the from type are not the same, use the type
172 // simplifier to reduce the type, then reuse cast_retty_impl to get the
174 typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type;
177 template<class To, class FromTy>
178 struct cast_retty_wrap<To, FromTy, FromTy> {
179 // When the simplified type is equal to the from type, use it directly.
180 typedef typename cast_retty_impl<To,FromTy>::ret_type ret_type;
183 template<class To, class From>
185 typedef typename cast_retty_wrap<To, From,
186 typename simplify_type<From>::SimpleType>::ret_type ret_type;
189 // Ensure the non-simple values are converted using the simplify_type template
190 // that may be specialized by smart pointers...
192 template<class To, class From, class SimpleFrom> struct cast_convert_val {
193 // This is not a simple type, use the template to simplify it...
194 static typename cast_retty<To, From>::ret_type doit(From &Val) {
195 return cast_convert_val<To, SimpleFrom,
196 typename simplify_type<SimpleFrom>::SimpleType>::doit(
197 simplify_type<From>::getSimplifiedValue(Val));
201 template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> {
202 // This _is_ a simple type, just cast it.
203 static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
204 typename cast_retty<To, FromTy>::ret_type Res2
205 = (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val);
210 template <class X> struct is_simple_type {
211 static const bool value =
212 is_same<X, typename simplify_type<X>::SimpleType>::value;
215 // cast<X> - Return the argument parameter cast to the specified type. This
216 // casting operator asserts that the type is correct, so it does not return null
217 // on failure. It does not allow a null argument (use cast_or_null for that).
218 // It is typically used like this:
220 // cast<Instruction>(myVal)->getParent()
222 template <class X, class Y>
223 inline typename enable_if_c<!is_simple_type<Y>::value,
224 typename cast_retty<X, const Y>::ret_type>::type
226 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
227 return cast_convert_val<
228 X, const Y, typename simplify_type<const Y>::SimpleType>::doit(Val);
231 template <class X, class Y>
232 inline typename cast_retty<X, Y>::ret_type cast(Y &Val) {
233 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
234 return cast_convert_val<X, Y,
235 typename simplify_type<Y>::SimpleType>::doit(Val);
238 template <class X, class Y>
239 inline typename cast_retty<X, Y *>::ret_type cast(Y *Val) {
240 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
241 return cast_convert_val<X, Y*,
242 typename simplify_type<Y*>::SimpleType>::doit(Val);
245 // cast_or_null<X> - Functionally identical to cast, except that a null value is
248 template <class X, class Y>
249 LLVM_ATTRIBUTE_UNUSED_RESULT inline typename cast_retty<X, Y *>::ret_type
250 cast_or_null(Y *Val) {
251 if (Val == 0) return 0;
252 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
257 // dyn_cast<X> - Return the argument parameter cast to the specified type. This
258 // casting operator returns null if the argument is of the wrong type, so it can
259 // be used to test for a type as well as cast if successful. This should be
260 // used in the context of an if statement like this:
262 // if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
265 template <class X, class Y>
266 LLVM_ATTRIBUTE_UNUSED_RESULT inline typename enable_if_c<
267 !is_simple_type<Y>::value, typename cast_retty<X, const Y>::ret_type>::type
268 dyn_cast(const Y &Val) {
269 return isa<X>(Val) ? cast<X>(Val) : 0;
272 template <class X, class Y>
273 LLVM_ATTRIBUTE_UNUSED_RESULT inline typename cast_retty<X, Y>::ret_type
275 return isa<X>(Val) ? cast<X>(Val) : 0;
278 template <class X, class Y>
279 LLVM_ATTRIBUTE_UNUSED_RESULT inline typename cast_retty<X, Y *>::ret_type
281 return isa<X>(Val) ? cast<X>(Val) : 0;
284 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
285 // value is accepted.
287 template <class X, class Y>
288 LLVM_ATTRIBUTE_UNUSED_RESULT inline typename cast_retty<X, Y *>::ret_type
289 dyn_cast_or_null(Y *Val) {
290 return (Val && isa<X>(Val)) ? cast<X>(Val) : 0;
293 } // End llvm namespace