1//===-- llvm/Support/Casting.h - Allow flexible, checked, casts -*- C++ -*-===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines the isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(),
11// and dyn_cast_or_null<X>() templates.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_SUPPORT_CASTING_H
16#define LLVM_SUPPORT_CASTING_H
17
18#include "llvm/Support/Compiler.h"
19#include "llvm/Support/type_traits.h"
20#include <cassert>
21
22namespace llvm {
23
24//===----------------------------------------------------------------------===//
25// isa<x> Support Templates
26//===----------------------------------------------------------------------===//
27
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.
31//
32template<typename From> struct simplify_type {
33 typedef From SimpleType; // The real type this represents...
34
35 // An accessor to get the real value...
36 static SimpleType &getSimplifiedValue(From &Val) { return Val; }
37};
38
39template<typename From> struct simplify_type<const From> {
40 typedef typename simplify_type<From>::SimpleType NonConstSimpleType;
41 typedef typename add_const_past_pointer<NonConstSimpleType>::type
42 SimpleType;
43 typedef typename add_lvalue_reference_if_not_pointer<SimpleType>::type
44 RetType;
45 static RetType getSimplifiedValue(const From& Val) {
46 return simplify_type<From>::getSimplifiedValue(const_cast<From&>(Val));
47 }
48};
49
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.
53template <typename To, typename From, typename Enabler = void>
54struct isa_impl {
55 static inline bool doit(const From &Val) {
56 return To::classof(&Val);
57 }
58};
59
60/// \brief Always allow upcasts, and perform no dynamic check for them.
61template <typename To, typename From>
62struct isa_impl<
63 To, From, typename std::enable_if<std::is_base_of<To, From>::value>::type> {
64 static inline bool doit(const From &) { return true; }
65};
66
67template <typename To, typename From> struct isa_impl_cl {
68 static inline bool doit(const From &Val) {
69 return isa_impl<To, From>::doit(Val);
70 }
71};
72
73template <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);
76 }
77};
78
79template <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);
83 }
84};
85
86template <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);
90 }
91};
92
93template <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);
97 }
98};
99
100template <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);
104 }
105};
106
107template<typename To, typename From, typename SimpleFrom>
108struct 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));
115 }
116};
117
118template<typename To, typename FromTy>
119struct 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);
123 }
124};
125
126// isa<X> - Return true if the parameter to the template is an instance of the
127// template type argument. Used like this:
128//
129// if (isa<Type>(myVal)) { ... }
130//
131template <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);
134}
135
136//===----------------------------------------------------------------------===//
137// cast<x> Support Templates
138//===----------------------------------------------------------------------===//
139
140template<class To, class From> struct cast_retty;
141
142
143// Calculate what type the 'cast' function should return, based on a requested
144// type of To and a source type of From.
145template<class To, class From> struct cast_retty_impl {
146 typedef To& ret_type; // Normal case, return Ty&
147};
148template<class To, class From> struct cast_retty_impl<To, const From> {
149 typedef const To &ret_type; // Normal case, return Ty&
150};
151
152template<class To, class From> struct cast_retty_impl<To, From*> {
153 typedef To* ret_type; // Pointer arg case, return Ty*
154};
155
156template<class To, class From> struct cast_retty_impl<To, const From*> {
157 typedef const To* ret_type; // Constant pointer arg case, return const Ty*
158};
159
160template<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*
162};
163
164
165template<class To, class From, class SimpleFrom>
166struct 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
169 // resultant type.
170 typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type;
171};
172
173template<class To, class FromTy>
174struct 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;
177};
178
179template<class To, class From>
180struct cast_retty {
181 typedef typename cast_retty_wrap<To, From,
182 typename simplify_type<From>::SimpleType>::ret_type ret_type;
183};
184
185// Ensure the non-simple values are converted using the simplify_type template
186// that may be specialized by smart pointers...
187//
188template<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));
194 }
195};
196
197template<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);
202 return Res2;
203 }
204};
205
206template <class X> struct is_simple_type {
207 static const bool value =
208 std::is_same<X, typename simplify_type<X>::SimpleType>::value;
209};
210
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:
215//
216// cast<Instruction>(myVal)->getParent()
217//
218template <class X, class Y>
219inline typename std::enable_if<!is_simple_type<Y>::value,
220 typename cast_retty<X, const Y>::ret_type>::type
221cast(const Y &Val) {
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);
225}
226
227template <class X, class Y>
228inline 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);
232}
233
234template <class X, class Y>
235inline 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);
239}
240
241// cast_or_null<X> - Functionally identical to cast, except that a null value is
242// accepted.
243//
244template <class X, class Y>
245LLVM_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) {
249 if (!Val)
250 return nullptr;
251 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
252 return cast<X>(Val);
253}
254
255template <class X, class Y>
256LLVM_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) {
260 if (!Val)
261 return nullptr;
262 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
263 return cast<X>(Val);
264}
265
266template <class X, class Y>
267LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type
268cast_or_null(Y *Val) {
269 if (!Val) return nullptr;
270 assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
271 return cast<X>(Val);
272}
273
274
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:
279//
280// if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
281//
282
283template <class X, class Y>
284LLVM_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;
289}
290
291template <class X, class Y>
292LLVM_NODISCARD inline typename cast_retty<X, Y>::ret_type dyn_cast(Y &Val) {
293 return isa<X>(Val) ? cast<X>(Val) : nullptr;
294}
295
296template <class X, class Y>
297LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type dyn_cast(Y *Val) {
298 return isa<X>(Val) ? cast<X>(Val) : nullptr;
299}
300
301// dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
302// value is accepted.
303//
304template <class X, class Y>
305LLVM_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;
310}
311
312template <class X, class Y>
313LLVM_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;
318}
319
320template <class X, class Y>
321LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type
322dyn_cast_or_null(Y *Val) {
323 return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
324}
325
326} // End llvm namespace
327
328#endif
329