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8b8fa7b2f4
Additionally, all such cases are handled with no dynamic check.
All `classof()` of the form
class Foo {
[...]
static bool classof(const Bar *) { return true; }
[...]
}
where Foo is an ancestor of Bar are no longer necessary.
Don't write them!
Note: The exact test is `is_base_of<Foo, Bar>`, which is non-strict, so
that Foo is considered an ancestor of itself.
This leads to the following rule of thumb for LLVM-style RTTI:
The argument type of `classof()` should be a strict ancestor.
For more information about implementing LLVM-style RTTI, see
docs/HowToSetUpLLVMStyleRTTI.rst
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165765 91177308-0d34-0410-b5e6-96231b3b80d8
248 lines
8.5 KiB
C++
248 lines
8.5 KiB
C++
//===-- llvm/Support/Casting.h - Allow flexible, checked, casts -*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(),
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// and dyn_cast_or_null<X>() templates.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_CASTING_H
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#define LLVM_SUPPORT_CASTING_H
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#include "llvm/Support/type_traits.h"
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#include <cassert>
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namespace llvm {
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//===----------------------------------------------------------------------===//
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// isa<x> Support Templates
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//===----------------------------------------------------------------------===//
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// Define a template that can be specialized by smart pointers to reflect the
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// fact that they are automatically dereferenced, and are not involved with the
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// template selection process... the default implementation is a noop.
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//
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template<typename From> struct simplify_type {
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typedef From SimpleType; // The real type this represents...
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// An accessor to get the real value...
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static SimpleType &getSimplifiedValue(From &Val) { return Val; }
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};
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template<typename From> struct simplify_type<const From> {
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typedef const From SimpleType;
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static SimpleType &getSimplifiedValue(const From &Val) {
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return simplify_type<From>::getSimplifiedValue(static_cast<From&>(Val));
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}
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};
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// The core of the implementation of isa<X> is here; To and From should be
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// the names of classes. This template can be specialized to customize the
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// implementation of isa<> without rewriting it from scratch.
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template <typename To, typename From, typename Enabler = void>
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struct isa_impl {
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static inline bool doit(const From &Val) {
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return To::classof(&Val);
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}
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};
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/// \brief Always allow upcasts, and perform no dynamic check for them.
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template <typename To, typename From>
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struct isa_impl<To, From,
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typename llvm::enable_if_c<
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llvm::is_base_of<To, From>::value
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>::type
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> {
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static inline bool doit(const From &) { return true; }
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};
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template <typename To, typename From> struct isa_impl_cl {
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static inline bool doit(const From &Val) {
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return isa_impl<To, From>::doit(Val);
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}
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};
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template <typename To, typename From> struct isa_impl_cl<To, const From> {
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static inline bool doit(const From &Val) {
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return isa_impl<To, From>::doit(Val);
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}
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};
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template <typename To, typename From> struct isa_impl_cl<To, From*> {
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static inline bool doit(const From *Val) {
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assert(Val && "isa<> used on a null pointer");
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return isa_impl<To, From>::doit(*Val);
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}
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};
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template <typename To, typename From> struct isa_impl_cl<To, const From*> {
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static inline bool doit(const From *Val) {
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assert(Val && "isa<> used on a null pointer");
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return isa_impl<To, From>::doit(*Val);
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}
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};
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template <typename To, typename From> struct isa_impl_cl<To, const From*const> {
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static inline bool doit(const From *Val) {
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assert(Val && "isa<> used on a null pointer");
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return isa_impl<To, From>::doit(*Val);
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}
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};
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template<typename To, typename From, typename SimpleFrom>
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struct isa_impl_wrap {
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// When From != SimplifiedType, we can simplify the type some more by using
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// the simplify_type template.
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static bool doit(const From &Val) {
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return isa_impl_wrap<To, SimpleFrom,
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typename simplify_type<SimpleFrom>::SimpleType>::doit(
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simplify_type<From>::getSimplifiedValue(Val));
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}
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};
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template<typename To, typename FromTy>
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struct isa_impl_wrap<To, FromTy, FromTy> {
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// When From == SimpleType, we are as simple as we are going to get.
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static bool doit(const FromTy &Val) {
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return isa_impl_cl<To,FromTy>::doit(Val);
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}
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};
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// isa<X> - Return true if the parameter to the template is an instance of the
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// template type argument. Used like this:
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//
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// if (isa<Type>(myVal)) { ... }
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//
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template <class X, class Y>
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inline bool isa(const Y &Val) {
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return isa_impl_wrap<X, Y, typename simplify_type<Y>::SimpleType>::doit(Val);
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}
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//===----------------------------------------------------------------------===//
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// cast<x> Support Templates
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//===----------------------------------------------------------------------===//
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template<class To, class From> struct cast_retty;
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// Calculate what type the 'cast' function should return, based on a requested
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// type of To and a source type of From.
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template<class To, class From> struct cast_retty_impl {
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typedef To& ret_type; // Normal case, return Ty&
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};
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template<class To, class From> struct cast_retty_impl<To, const From> {
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typedef const To &ret_type; // Normal case, return Ty&
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};
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template<class To, class From> struct cast_retty_impl<To, From*> {
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typedef To* ret_type; // Pointer arg case, return Ty*
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};
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template<class To, class From> struct cast_retty_impl<To, const From*> {
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typedef const To* ret_type; // Constant pointer arg case, return const Ty*
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};
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template<class To, class From> struct cast_retty_impl<To, const From*const> {
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typedef const To* ret_type; // Constant pointer arg case, return const Ty*
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};
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template<class To, class From, class SimpleFrom>
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struct cast_retty_wrap {
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// When the simplified type and the from type are not the same, use the type
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// simplifier to reduce the type, then reuse cast_retty_impl to get the
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// resultant type.
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typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type;
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};
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template<class To, class FromTy>
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struct cast_retty_wrap<To, FromTy, FromTy> {
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// When the simplified type is equal to the from type, use it directly.
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typedef typename cast_retty_impl<To,FromTy>::ret_type ret_type;
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};
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template<class To, class From>
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struct cast_retty {
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typedef typename cast_retty_wrap<To, From,
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typename simplify_type<From>::SimpleType>::ret_type ret_type;
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};
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// Ensure the non-simple values are converted using the simplify_type template
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// that may be specialized by smart pointers...
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//
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template<class To, class From, class SimpleFrom> struct cast_convert_val {
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// This is not a simple type, use the template to simplify it...
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static typename cast_retty<To, From>::ret_type doit(const From &Val) {
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return cast_convert_val<To, SimpleFrom,
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typename simplify_type<SimpleFrom>::SimpleType>::doit(
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simplify_type<From>::getSimplifiedValue(Val));
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}
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};
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template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> {
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// This _is_ a simple type, just cast it.
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static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
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typename cast_retty<To, FromTy>::ret_type Res2
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= (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val);
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return Res2;
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}
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};
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// cast<X> - Return the argument parameter cast to the specified type. This
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// casting operator asserts that the type is correct, so it does not return null
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// on failure. It does not allow a null argument (use cast_or_null for that).
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// It is typically used like this:
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//
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// cast<Instruction>(myVal)->getParent()
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//
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template <class X, class Y>
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inline typename cast_retty<X, Y>::ret_type cast(const Y &Val) {
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assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
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return cast_convert_val<X, Y,
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typename simplify_type<Y>::SimpleType>::doit(Val);
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}
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// cast_or_null<X> - Functionally identical to cast, except that a null value is
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// accepted.
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//
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template <class X, class Y>
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inline typename cast_retty<X, Y*>::ret_type cast_or_null(Y *Val) {
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if (Val == 0) return 0;
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assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
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return cast<X>(Val);
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}
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// dyn_cast<X> - Return the argument parameter cast to the specified type. This
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// casting operator returns null if the argument is of the wrong type, so it can
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// be used to test for a type as well as cast if successful. This should be
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// used in the context of an if statement like this:
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//
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// if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
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//
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template <class X, class Y>
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inline typename cast_retty<X, Y>::ret_type dyn_cast(const Y &Val) {
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return isa<X>(Val) ? cast<X, Y>(Val) : 0;
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}
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// dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
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// value is accepted.
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//
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template <class X, class Y>
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inline typename cast_retty<X, Y*>::ret_type dyn_cast_or_null(Y *Val) {
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return (Val && isa<X>(Val)) ? cast<X>(Val) : 0;
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}
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} // End llvm namespace
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#endif
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