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 const From SimpleType;
40 static SimpleType &getSimplifiedValue(const From &Val) {
41 return simplify_type<From>::getSimplifiedValue(static_cast<From&>(Val));
45 // The core of the implementation of isa<X> is here; To and From should be
46 // the names of classes. This template can be specialized to customize the
47 // implementation of isa<> without rewriting it from scratch.
48 template <typename To, typename From, typename Enabler = void>
50 static inline bool doit(const From &Val) {
51 return To::classof(&Val);
55 /// \brief Always allow upcasts, and perform no dynamic check for them.
56 template <typename To, typename From>
57 struct isa_impl<To, From,
58 typename llvm::enable_if_c<
59 llvm::is_base_of<To, From>::value
62 static inline bool doit(const From &) { return true; }
65 template <typename To, typename From> struct isa_impl_cl {
66 static inline bool doit(const From &Val) {
67 return isa_impl<To, From>::doit(Val);
71 template <typename To, typename From> struct isa_impl_cl<To, const From> {
72 static inline bool doit(const From &Val) {
73 return isa_impl<To, From>::doit(Val);
77 template <typename To, typename From> struct isa_impl_cl<To, From*> {
78 static inline bool doit(const From *Val) {
79 assert(Val && "isa<> used on a null pointer");
80 return isa_impl<To, From>::doit(*Val);
84 template <typename To, typename From> struct isa_impl_cl<To, const From*> {
85 static inline bool doit(const From *Val) {
86 assert(Val && "isa<> used on a null pointer");
87 return isa_impl<To, From>::doit(*Val);
91 template <typename To, typename From> struct isa_impl_cl<To, const From*const> {
92 static inline bool doit(const From *Val) {
93 assert(Val && "isa<> used on a null pointer");
94 return isa_impl<To, From>::doit(*Val);
98 template<typename To, typename From, typename SimpleFrom>
99 struct isa_impl_wrap {
100 // When From != SimplifiedType, we can simplify the type some more by using
101 // the simplify_type template.
102 static bool doit(const From &Val) {
103 return isa_impl_wrap<To, SimpleFrom,
104 typename simplify_type<SimpleFrom>::SimpleType>::doit(
105 simplify_type<From>::getSimplifiedValue(Val));
109 template<typename To, typename FromTy>
110 struct isa_impl_wrap<To, FromTy, FromTy> {
111 // When From == SimpleType, we are as simple as we are going to get.
112 static bool doit(const FromTy &Val) {
113 return isa_impl_cl<To,FromTy>::doit(Val);
117 // isa<X> - Return true if the parameter to the template is an instance of the
118 // template type argument. Used like this:
120 // if (isa<Type>(myVal)) { ... }
122 template <class X, class Y>
123 inline bool isa(const Y &Val) {
124 return isa_impl_wrap<X, Y, typename simplify_type<Y>::SimpleType>::doit(Val);
127 //===----------------------------------------------------------------------===//
128 // cast<x> Support Templates
129 //===----------------------------------------------------------------------===//
131 template<class To, class From> struct cast_retty;
134 // Calculate what type the 'cast' function should return, based on a requested
135 // type of To and a source type of From.
136 template<class To, class From> struct cast_retty_impl {
137 typedef To& ret_type; // Normal case, return Ty&
139 template<class To, class From> struct cast_retty_impl<To, const From> {
140 typedef const To &ret_type; // Normal case, return Ty&
143 template<class To, class From> struct cast_retty_impl<To, From*> {
144 typedef To* ret_type; // Pointer arg case, return Ty*
147 template<class To, class From> struct cast_retty_impl<To, const From*> {
148 typedef const To* ret_type; // Constant pointer arg case, return const Ty*
151 template<class To, class From> struct cast_retty_impl<To, const From*const> {
152 typedef const To* ret_type; // Constant pointer arg case, return const Ty*
156 template<class To, class From, class SimpleFrom>
157 struct cast_retty_wrap {
158 // When the simplified type and the from type are not the same, use the type
159 // simplifier to reduce the type, then reuse cast_retty_impl to get the
161 typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type;
164 template<class To, class FromTy>
165 struct cast_retty_wrap<To, FromTy, FromTy> {
166 // When the simplified type is equal to the from type, use it directly.
167 typedef typename cast_retty_impl<To,FromTy>::ret_type ret_type;
170 template<class To, class From>
172 typedef typename cast_retty_wrap<To, From,
173 typename simplify_type<From>::SimpleType>::ret_type ret_type;
176 // Ensure the non-simple values are converted using the simplify_type template
177 // that may be specialized by smart pointers...
179 template<class To, class From, class SimpleFrom> struct cast_convert_val {
180 // This is not a simple type, use the template to simplify it...
181 static typename cast_retty<To, From>::ret_type doit(const From &Val) {
182 return cast_convert_val<To, SimpleFrom,
183 typename simplify_type<SimpleFrom>::SimpleType>::doit(
184 simplify_type<From>::getSimplifiedValue(Val));
188 template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> {
189 // This _is_ a simple type, just cast it.
190 static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
191 typename cast_retty<To, FromTy>::ret_type Res2
192 = (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val);
199 // cast<X> - Return the argument parameter cast to the specified type. This
200 // casting operator asserts that the type is correct, so it does not return null
201 // on failure. It does not allow a null argument (use cast_or_null for that).
202 // It is typically used like this:
204 // cast<Instruction>(myVal)->getParent()
206 template <class X, class Y>
207 inline typename cast_retty<X, Y>::ret_type cast(const Y &Val) {
208 assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
209 return cast_convert_val<X, Y,
210 typename simplify_type<Y>::SimpleType>::doit(Val);
213 // cast_or_null<X> - Functionally identical to cast, except that a null value is
216 template <class X, class Y>
217 inline typename cast_retty<X, Y*>::ret_type cast_or_null(Y *Val) {
218 if (Val == 0) return 0;
219 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
224 // dyn_cast<X> - Return the argument parameter cast to the specified type. This
225 // casting operator returns null if the argument is of the wrong type, so it can
226 // be used to test for a type as well as cast if successful. This should be
227 // used in the context of an if statement like this:
229 // if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
232 template <class X, class Y>
233 inline typename cast_retty<X, Y>::ret_type dyn_cast(const Y &Val) {
234 return isa<X>(Val) ? cast<X, Y>(Val) : 0;
237 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
238 // value is accepted.
240 template <class X, class Y>
241 inline typename cast_retty<X, Y*>::ret_type dyn_cast_or_null(Y *Val) {
242 return (Val && isa<X>(Val)) ? cast<X>(Val) : 0;
245 } // End llvm namespace