//===- Redeclarable.h - Base for Decls that can be redeclared --*- 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
//
//===----------------------------------------------------------------------===//
//
// This file defines the Redeclarable interface.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_AST_REDECLARABLE_H
#define LLVM_CLANG_AST_REDECLARABLE_H
#include "clang/AST/ExternalASTSource.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Support/Casting.h"
#include <cassert>
#include <cstddef>
#include <iterator>
namespace clang {
class ASTContext;
class Decl;
// Some notes on redeclarables:
//
// - Every redeclarable is on a circular linked list.
//
// - Every decl has a pointer to the first element of the chain _and_ a
// DeclLink that may point to one of 3 possible states:
// - the "previous" (temporal) element in the chain
// - the "latest" (temporal) element in the chain
// - the "uninitialized-latest" value (when newly-constructed)
//
// - The first element is also often called the canonical element. Every
// element has a pointer to it so that "getCanonical" can be fast.
//
// - Most links in the chain point to previous, except the link out of
// the first; it points to latest.
//
// - Elements are called "first", "previous", "latest" or
// "most-recent" when referring to temporal order: order of addition
// to the chain.
//
// - It's easiest to just ignore the implementation of DeclLink when making
// sense of the redeclaration chain.
//
// - There's also a "definition" link for several types of
// redeclarable, where only one definition should exist at any given
// time (and the defn pointer is stored in the decl's "data" which
// is copied to every element on the chain when it's changed).
//
// Here is some ASCII art:
//
// "first" "latest"
// "canonical" "most recent"
// +------------+ first +--------------+
// | | <--------------------------- | |
// | | | |
// | | | |
// | | +--------------+ | |
// | | first | | | |
// | | <---- | | | |
// | | | | | |
// | @class A | link | @interface A | link | @class A |
// | seen first | <---- | seen second | <---- | seen third |
// | | | | | |
// +------------+ +--------------+ +--------------+
// | data | defn | data | defn | data |
// | | ----> | | <---- | |
// +------------+ +--------------+ +--------------+
// | | ^ ^
// | |defn | |
// | link +-----+ |
// +-->-------------------------------------------+
/// Provides common interface for the Decls that can be redeclared.
template<typename decl_type>
class Redeclarable {
protected:
class DeclLink {
/// A pointer to a known latest declaration, either statically known or
/// generationally updated as decls are added by an external source.
using KnownLatest =
LazyGenerationalUpdatePtr<const Decl *, Decl *,
&ExternalASTSource::CompleteRedeclChain>;
/// We store a pointer to the ASTContext in the UninitializedLatest
/// pointer, but to avoid circular type dependencies when we steal the low
/// bits of this pointer, we use a raw void* here.
using UninitializedLatest = const void *;
using Previous = Decl *;
/// A pointer to either an uninitialized latest declaration (where either
/// we've not yet set the previous decl or there isn't one), or to a known
/// previous declaration.
using NotKnownLatest = llvm::PointerUnion<Previous, UninitializedLatest>;
mutable llvm::PointerUnion<NotKnownLatest, KnownLatest> Link;
public:
enum PreviousTag { PreviousLink };
enum LatestTag { LatestLink };
DeclLink(LatestTag, const ASTContext &Ctx)
: Link(NotKnownLatest(reinterpret_cast<UninitializedLatest>(&Ctx))) {}
DeclLink(PreviousTag, decl_type *D) : Link(NotKnownLatest(Previous(D))) {}
bool isFirst() const {
return Link.is<KnownLatest>() ||
// FIXME: 'template' is required on the next line due to an
// apparent clang bug.
Link.get<NotKnownLatest>().template is<UninitializedLatest>();
}
decl_type *getPrevious(const decl_type *D) const {
if (Link.is<NotKnownLatest>()) {
NotKnownLatest NKL = Link.get<NotKnownLatest>();
if (NKL.is<Previous>())
return static_cast<decl_type*>(NKL.get<Previous>());
// Allocate the generational 'most recent' cache now, if needed.
Link = KnownLatest(*reinterpret_cast<const ASTContext *>(
NKL.get<UninitializedLatest>()),
const_cast<decl_type *>(D));
}
return static_cast<decl_type*>(Link.get<KnownLatest>().get(D));
}
void setPrevious(decl_type *D) {
assert(!isFirst() && "decl became non-canonical unexpectedly");
Link = Previous(D);
}
void setLatest(decl_type *D) {
assert(isFirst() && "decl became canonical unexpectedly");
if (Link.is<NotKnownLatest>()) {
NotKnownLatest NKL = Link.get<NotKnownLatest>();
Link = KnownLatest(*reinterpret_cast<const ASTContext *>(
NKL.get<UninitializedLatest>()),
D);
} else {
auto Latest = Link.get<KnownLatest>();
Latest.set(D);
Link = Latest;
}
}
void markIncomplete() { Link.get<KnownLatest>().markIncomplete(); }
Decl *getLatestNotUpdated() const {
assert(isFirst() && "expected a canonical decl");
if (Link.is<NotKnownLatest>())
return nullptr;
return Link.get<KnownLatest>().getNotUpdated();
}
};
static DeclLink PreviousDeclLink(decl_type *D) {
return DeclLink(DeclLink::PreviousLink, D);
}
static DeclLink LatestDeclLink(const ASTContext &Ctx) {
return DeclLink(DeclLink::LatestLink, Ctx);
}
/// Points to the next redeclaration in the chain.
///
/// If isFirst() is false, this is a link to the previous declaration
/// of this same Decl. If isFirst() is true, this is the first
/// declaration and Link points to the latest declaration. For example:
///
/// #1 int f(int x, int y = 1); // <pointer to #3, true>
/// #2 int f(int x = 0, int y); // <pointer to #1, false>
/// #3 int f(int x, int y) { return x + y; } // <pointer to #2, false>
///
/// If there is only one declaration, it is <pointer to self, true>
DeclLink RedeclLink;
decl_type *First;
decl_type *getNextRedeclaration() const {
return RedeclLink.getPrevious(static_cast<const decl_type *>(this));
}
public:
friend class ASTDeclReader;
friend class ASTDeclWriter;
friend class IncrementalParser;
Redeclarable(const ASTContext &Ctx)
: RedeclLink(LatestDeclLink(Ctx)),
First(static_cast<decl_type *>(this)) {}
/// Return the previous declaration of this declaration or NULL if this
/// is the first declaration.
decl_type *getPreviousDecl() {
if (!RedeclLink.isFirst())
return getNextRedeclaration();
return nullptr;
}
const decl_type *getPreviousDecl() const {
return const_cast<decl_type *>(
static_cast<const decl_type*>(this))->getPreviousDecl();
}
/// Return the first declaration of this declaration or itself if this
/// is the only declaration.
decl_type *getFirstDecl() { return First; }
/// Return the first declaration of this declaration or itself if this
/// is the only declaration.
const decl_type *getFirstDecl() const { return First; }
/// True if this is the first declaration in its redeclaration chain.
bool isFirstDecl() const { return RedeclLink.isFirst(); }
/// Returns the most recent (re)declaration of this declaration.
decl_type *getMostRecentDecl() {
return getFirstDecl()->getNextRedeclaration();
}
/// Returns the most recent (re)declaration of this declaration.
const decl_type *getMostRecentDecl() const {
return getFirstDecl()->getNextRedeclaration();
}
/// Set the previous declaration. If PrevDecl is NULL, set this as the
/// first and only declaration.
void setPreviousDecl(decl_type *PrevDecl);
/// Iterates through all the redeclarations of the same decl.
class redecl_iterator {
/// Current - The current declaration.
decl_type *Current = nullptr;
decl_type *Starter;
bool PassedFirst = false;
public:
using value_type = decl_type *;
using reference = decl_type *;
using pointer = decl_type *;
using iterator_category = std::forward_iterator_tag;
using difference_type = std::ptrdiff_t;
redecl_iterator() = default;
explicit redecl_iterator(decl_type *C) : Current(C), Starter(C) {}
reference operator*() const { return Current; }
pointer operator->() const { return Current; }
redecl_iterator& operator++() {
assert(Current && "Advancing while iterator has reached end");
// Make sure we don't infinitely loop on an invalid redecl chain. This
// should never happen.
if (Current->isFirstDecl()) {
if (PassedFirst) {
assert(0 && "Passed first decl twice, invalid redecl chain!");
Current = nullptr;
return *this;
}
PassedFirst = true;
}
// Get either previous decl or latest decl.
decl_type *Next = Current->getNextRedeclaration();
Current = (Next != Starter) ? Next : nullptr;
return *this;
}
redecl_iterator operator++(int) {
redecl_iterator tmp(*this);
++(*this);
return tmp;
}
friend bool operator==(redecl_iterator x, redecl_iterator y) {
return x.Current == y.Current;
}
friend bool operator!=(redecl_iterator x, redecl_iterator y) {
return x.Current != y.Current;
}
};
using redecl_range = llvm::iterator_range<redecl_iterator>;
/// Returns an iterator range for all the redeclarations of the same
/// decl. It will iterate at least once (when this decl is the only one).
redecl_range redecls() const {
return redecl_range(redecl_iterator(const_cast<decl_type *>(
static_cast<const decl_type *>(this))),
redecl_iterator());
}
redecl_iterator redecls_begin() const { return redecls().begin(); }
redecl_iterator redecls_end() const { return redecls().end(); }
};
/// Get the primary declaration for a declaration from an AST file. That
/// will be the first-loaded declaration.
Decl *getPrimaryMergedDecl(Decl *D);
/// Provides common interface for the Decls that cannot be redeclared,
/// but can be merged if the same declaration is brought in from multiple
/// modules.
template<typename decl_type>
class Mergeable {
public:
Mergeable() = default;
/// Return the first declaration of this declaration or itself if this
/// is the only declaration.
decl_type *getFirstDecl() {
auto *D = static_cast<decl_type *>(this);
if (!D->isFromASTFile())
return D;
return cast<decl_type>(getPrimaryMergedDecl(const_cast<decl_type*>(D)));
}
/// Return the first declaration of this declaration or itself if this
/// is the only declaration.
const decl_type *getFirstDecl() const {
const auto *D = static_cast<const decl_type *>(this);
if (!D->isFromASTFile())
return D;
return cast<decl_type>(getPrimaryMergedDecl(const_cast<decl_type*>(D)));
}
/// Returns true if this is the first declaration.
bool isFirstDecl() const { return getFirstDecl() == this; }
};
/// A wrapper class around a pointer that always points to its canonical
/// declaration.
///
/// CanonicalDeclPtr<decl_type> behaves just like decl_type*, except we call
/// decl_type::getCanonicalDecl() on construction.
///
/// This is useful for hashtables that you want to be keyed on a declaration's
/// canonical decl -- if you use CanonicalDeclPtr as the key, you don't need to
/// remember to call getCanonicalDecl() everywhere.
template <typename decl_type> class CanonicalDeclPtr {
public:
CanonicalDeclPtr() = default;
CanonicalDeclPtr(decl_type *Ptr)
: Ptr(Ptr ? Ptr->getCanonicalDecl() : nullptr) {}
CanonicalDeclPtr(const CanonicalDeclPtr &) = default;
CanonicalDeclPtr &operator=(const CanonicalDeclPtr &) = default;
operator decl_type *() { return Ptr; }
operator const decl_type *() const { return Ptr; }
decl_type *operator->() { return Ptr; }
const decl_type *operator->() const { return Ptr; }
decl_type &operator*() { return *Ptr; }
const decl_type &operator*() const { return *Ptr; }
friend bool operator==(CanonicalDeclPtr LHS, CanonicalDeclPtr RHS) {
return LHS.Ptr == RHS.Ptr;
}
friend bool operator!=(CanonicalDeclPtr LHS, CanonicalDeclPtr RHS) {
return LHS.Ptr != RHS.Ptr;
}
private:
friend struct llvm::DenseMapInfo<CanonicalDeclPtr<decl_type>>;
friend struct llvm::PointerLikeTypeTraits<CanonicalDeclPtr<decl_type>>;
decl_type *Ptr = nullptr;
};
} // namespace clang
namespace llvm {
template <typename decl_type>
struct DenseMapInfo<clang::CanonicalDeclPtr<decl_type>> {
using CanonicalDeclPtr = clang::CanonicalDeclPtr<decl_type>;
using BaseInfo = DenseMapInfo<decl_type *>;
static CanonicalDeclPtr getEmptyKey() {
// Construct our CanonicalDeclPtr this way because the regular constructor
// would dereference P.Ptr, which is not allowed.
CanonicalDeclPtr P;
P.Ptr = BaseInfo::getEmptyKey();
return P;
}
static CanonicalDeclPtr getTombstoneKey() {
CanonicalDeclPtr P;
P.Ptr = BaseInfo::getTombstoneKey();
return P;
}
static unsigned getHashValue(const CanonicalDeclPtr &P) {
return BaseInfo::getHashValue(P);
}
static bool isEqual(const CanonicalDeclPtr &LHS,
const CanonicalDeclPtr &RHS) {
return BaseInfo::isEqual(LHS, RHS);
}
};
template <typename decl_type>
struct PointerLikeTypeTraits<clang::CanonicalDeclPtr<decl_type>> {
static inline void *getAsVoidPointer(clang::CanonicalDeclPtr<decl_type> P) {
return P.Ptr;
}
static inline clang::CanonicalDeclPtr<decl_type> getFromVoidPointer(void *P) {
clang::CanonicalDeclPtr<decl_type> C;
C.Ptr = PointerLikeTypeTraits<decl_type *>::getFromVoidPtr(P);
return C;
}
static constexpr int NumLowBitsAvailable =
PointerLikeTypeTraits<decl_type *>::NumLowBitsAvailable;
};
} // namespace llvm
#endif // LLVM_CLANG_AST_REDECLARABLE_H