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//=== Registry.h - Linker-supported plugin registries -----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Defines a registry template for discovering pluggable modules.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_REGISTRY_H
#define LLVM_SUPPORT_REGISTRY_H
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/DynamicLibrary.h"
#include <memory>
namespace llvm {
/// A simple registry entry which provides only a name, description, and
/// no-argument constructor.
template <typename T>
class SimpleRegistryEntry {
StringRef Name, Desc;
std::unique_ptr<T> (*Ctor)();
public:
SimpleRegistryEntry(StringRef N, StringRef D, std::unique_ptr<T> (*C)())
: Name(N), Desc(D), Ctor(C) {}
StringRef getName() const { return Name; }
StringRef getDesc() const { return Desc; }
std::unique_ptr<T> instantiate() const { return Ctor(); }
};
/// A global registry used in conjunction with static constructors to make
/// pluggable components (like targets or garbage collectors) "just work" when
/// linked with an executable.
template <typename T>
class Registry {
public:
typedef T type;
typedef SimpleRegistryEntry<T> entry;
class node;
class iterator;
private:
Registry() = delete;
friend class node;
static node *Head, *Tail;
public:
/// Node in linked list of entries.
///
class node {
friend class iterator;
friend Registry<T>;
node *Next;
const entry& Val;
public:
node(const entry &V) : Next(nullptr), Val(V) {}
};
/// Add a node to the Registry: this is the interface between the plugin and
/// the executable.
///
/// This function is exported by the executable and called by the plugin to
/// add a node to the executable's registry. Therefore it's not defined here
/// to avoid it being instantiated in the plugin and is instead defined in
/// the executable (see LLVM_INSTANTIATE_REGISTRY below).
static void add_node(node *N);
/// Iterators for registry entries.
///
class iterator
: public llvm::iterator_facade_base<iterator, std::forward_iterator_tag,
const entry> {
const node *Cur;
public:
explicit iterator(const node *N) : Cur(N) {}
bool operator==(const iterator &That) const { return Cur == That.Cur; }
iterator &operator++() { Cur = Cur->Next; return *this; }
const entry &operator*() const { return Cur->Val; }
};
// begin is not defined here in order to avoid usage of an undefined static
// data member, instead it's instantiated by LLVM_INSTANTIATE_REGISTRY.
static iterator begin();
static iterator end() { return iterator(nullptr); }
static iterator_range<iterator> entries() {
return make_range(begin(), end());
}
/// A static registration template. Use like such:
///
/// Registry<Collector>::Add<FancyGC>
/// X("fancy-gc", "Newfangled garbage collector.");
///
/// Use of this template requires that:
///
/// 1. The registered subclass has a default constructor.
template <typename V>
class Add {
entry Entry;
node Node;
static std::unique_ptr<T> CtorFn() { return std::make_unique<V>(); }
public:
Add(StringRef Name, StringRef Desc)
: Entry(Name, Desc, CtorFn), Node(Entry) {
add_node(&Node);
}
};
};
} // end namespace llvm
/// Instantiate a registry class.
///
/// This provides template definitions of add_node, begin, and the Head and Tail
/// pointers, then explicitly instantiates them. We could explicitly specialize
/// them, instead of the two-step process of define then instantiate, but
/// strictly speaking that's not allowed by the C++ standard (we would need to
/// have explicit specialization declarations in all translation units where the
/// specialization is used) so we don't.
#define LLVM_INSTANTIATE_REGISTRY(REGISTRY_CLASS) \
namespace llvm { \
template<typename T> typename Registry<T>::node *Registry<T>::Head = nullptr;\
template<typename T> typename Registry<T>::node *Registry<T>::Tail = nullptr;\
template<typename T> \
void Registry<T>::add_node(typename Registry<T>::node *N) { \
if (Tail) \
Tail->Next = N; \
else \
Head = N; \
Tail = N; \
} \
template<typename T> typename Registry<T>::iterator Registry<T>::begin() { \
return iterator(Head); \
} \
template REGISTRY_CLASS::node *Registry<REGISTRY_CLASS::type>::Head; \
template REGISTRY_CLASS::node *Registry<REGISTRY_CLASS::type>::Tail; \
template \
void Registry<REGISTRY_CLASS::type>::add_node(REGISTRY_CLASS::node*); \
template REGISTRY_CLASS::iterator Registry<REGISTRY_CLASS::type>::begin(); \
}
#endif // LLVM_SUPPORT_REGISTRY_H
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