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//===-- llvm/Support/Casting.h - Allow flexible, checked, casts -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(),
// and dyn_cast_or_null<X>() templates.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_CASTING_H
#define LLVM_SUPPORT_CASTING_H
#include <cassert>
namespace llvm {
//===----------------------------------------------------------------------===//
// isa<x> Support Templates
//===----------------------------------------------------------------------===//
// Define a template that can be specialized by smart pointers to reflect the
// fact that they are automatically dereferenced, and are not involved with the
// template selection process... the default implementation is a noop.
//
template<typename From> struct simplify_type {
typedef From SimpleType; // The real type this represents...
// An accessor to get the real value...
static SimpleType &getSimplifiedValue(From &Val) { return Val; }
};
template<typename From> struct simplify_type<const From> {
typedef const From SimpleType;
static SimpleType &getSimplifiedValue(const From &Val) {
return simplify_type<From>::getSimplifiedValue(static_cast<From&>(Val));
}
};
// The core of the implementation of isa<X> is here; To and From should be
// the names of classes. This template can be specialized to customize the
// implementation of isa<> without rewriting it from scratch.
template <typename To, typename From>
struct isa_impl {
static inline bool doit(const From &Val) {
return To::classof(&Val);
}
};
template <typename To, typename From> struct isa_impl_cl {
static inline bool doit(const From &Val) {
return isa_impl<To, From>::doit(Val);
}
};
template <typename To, typename From> struct isa_impl_cl<To, const From> {
static inline bool doit(const From &Val) {
return isa_impl<To, From>::doit(Val);
}
};
template <typename To, typename From> struct isa_impl_cl<To, From*> {
static inline bool doit(const From *Val) {
return isa_impl<To, From>::doit(*Val);
}
};
template <typename To, typename From> struct isa_impl_cl<To, const From*> {
static inline bool doit(const From *Val) {
return isa_impl<To, From>::doit(*Val);
}
};
template <typename To, typename From> struct isa_impl_cl<To, const From*const> {
static inline bool doit(const From *Val) {
return isa_impl<To, From>::doit(*Val);
}
};
template<typename To, typename From, typename SimpleFrom>
struct isa_impl_wrap {
// When From != SimplifiedType, we can simplify the type some more by using
// the simplify_type template.
static bool doit(const From &Val) {
return isa_impl_wrap<To, SimpleFrom,
typename simplify_type<SimpleFrom>::SimpleType>::doit(
simplify_type<From>::getSimplifiedValue(Val));
}
};
template<typename To, typename FromTy>
struct isa_impl_wrap<To, FromTy, FromTy> {
// When From == SimpleType, we are as simple as we are going to get.
static bool doit(const FromTy &Val) {
return isa_impl_cl<To,FromTy>::doit(Val);
}
};
// isa<X> - Return true if the parameter to the template is an instance of the
// template type argument. Used like this:
//
// if (isa<Type>(myVal)) { ... }
//
template <class X, class Y>
inline bool isa(const Y &Val) {
return isa_impl_wrap<X, Y, typename simplify_type<Y>::SimpleType>::doit(Val);
}
//===----------------------------------------------------------------------===//
// cast<x> Support Templates
//===----------------------------------------------------------------------===//
template<class To, class From> struct cast_retty;
// Calculate what type the 'cast' function should return, based on a requested
// type of To and a source type of From.
template<class To, class From> struct cast_retty_impl {
typedef To& ret_type; // Normal case, return Ty&
};
template<class To, class From> struct cast_retty_impl<To, const From> {
typedef const To &ret_type; // Normal case, return Ty&
};
template<class To, class From> struct cast_retty_impl<To, From*> {
typedef To* ret_type; // Pointer arg case, return Ty*
};
template<class To, class From> struct cast_retty_impl<To, const From*> {
typedef const To* ret_type; // Constant pointer arg case, return const Ty*
};
template<class To, class From> struct cast_retty_impl<To, const From*const> {
typedef const To* ret_type; // Constant pointer arg case, return const Ty*
};
template<class To, class From, class SimpleFrom>
struct cast_retty_wrap {
// When the simplified type and the from type are not the same, use the type
// simplifier to reduce the type, then reuse cast_retty_impl to get the
// resultant type.
typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type;
};
template<class To, class FromTy>
struct cast_retty_wrap<To, FromTy, FromTy> {
// When the simplified type is equal to the from type, use it directly.
typedef typename cast_retty_impl<To,FromTy>::ret_type ret_type;
};
template<class To, class From>
struct cast_retty {
typedef typename cast_retty_wrap<To, From,
typename simplify_type<From>::SimpleType>::ret_type ret_type;
};
// Ensure the non-simple values are converted using the simplify_type template
// that may be specialized by smart pointers...
//
template<class To, class From, class SimpleFrom> struct cast_convert_val {
// This is not a simple type, use the template to simplify it...
static typename cast_retty<To, From>::ret_type doit(const From &Val) {
return cast_convert_val<To, SimpleFrom,
typename simplify_type<SimpleFrom>::SimpleType>::doit(
simplify_type<From>::getSimplifiedValue(Val));
}
};
template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> {
// This _is_ a simple type, just cast it.
static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
typename cast_retty<To, FromTy>::ret_type Res2
= (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val);
return Res2;
}
};
// cast<X> - Return the argument parameter cast to the specified type. This
// casting operator asserts that the type is correct, so it does not return null
// on failure. It does not allow a null argument (use cast_or_null for that).
// It is typically used like this:
//
// cast<Instruction>(myVal)->getParent()
//
template <class X, class Y>
inline typename cast_retty<X, Y>::ret_type cast(const Y &Val) {
assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
return cast_convert_val<X, Y,
typename simplify_type<Y>::SimpleType>::doit(Val);
}
// cast_or_null<X> - Functionally identical to cast, except that a null value is
// accepted.
//
template <class X, class Y>
inline typename cast_retty<X, Y*>::ret_type cast_or_null(Y *Val) {
if (Val == 0) return 0;
assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
return cast<X>(Val);
}
// dyn_cast<X> - Return the argument parameter cast to the specified type. This
// casting operator returns null if the argument is of the wrong type, so it can
// be used to test for a type as well as cast if successful. This should be
// used in the context of an if statement like this:
//
// if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
//
template <class X, class Y>
inline typename cast_retty<X, Y>::ret_type dyn_cast(const Y &Val) {
return isa<X>(Val) ? cast<X, Y>(Val) : 0;
}
// dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
// value is accepted.
//
template <class X, class Y>
inline typename cast_retty<X, Y*>::ret_type dyn_cast_or_null(Y *Val) {
return (Val && isa<X>(Val)) ? cast<X>(Val) : 0;
}
} // End llvm namespace
#endif
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