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1//===- Redeclarable.h - Base for Decls that can be redeclared --*- 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 Redeclarable interface.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_AST_REDECLARABLE_H
15#define LLVM_CLANG_AST_REDECLARABLE_H
16
17#include "clang/AST/ExternalASTSource.h"
18#include "llvm/ADT/DenseMapInfo.h"
19#include "llvm/ADT/PointerUnion.h"
20#include "llvm/ADT/iterator_range.h"
21#include "llvm/Support/Casting.h"
22#include <cassert>
23#include <cstddef>
24#include <iterator>
25
26namespace clang {
27
28class ASTContext;
29class Decl;
30
31// Some notes on redeclarables:
32//
33// - Every redeclarable is on a circular linked list.
34//
35// - Every decl has a pointer to the first element of the chain _and_ a
36// DeclLink that may point to one of 3 possible states:
37// - the "previous" (temporal) element in the chain
38// - the "latest" (temporal) element in the chain
39// - the "uninitialized-latest" value (when newly-constructed)
40//
41// - The first element is also often called the canonical element. Every
42// element has a pointer to it so that "getCanonical" can be fast.
43//
44// - Most links in the chain point to previous, except the link out of
45// the first; it points to latest.
46//
47// - Elements are called "first", "previous", "latest" or
48// "most-recent" when referring to temporal order: order of addition
49// to the chain.
50//
51// - It's easiest to just ignore the implementation of DeclLink when making
52// sense of the redeclaration chain.
53//
54// - There's also a "definition" link for several types of
55// redeclarable, where only one definition should exist at any given
56// time (and the defn pointer is stored in the decl's "data" which
57// is copied to every element on the chain when it's changed).
58//
59// Here is some ASCII art:
60//
61// "first" "latest"
62// "canonical" "most recent"
63// +------------+ first +--------------+
64// | | <--------------------------- | |
65// | | | |
66// | | | |
67// | | +--------------+ | |
68// | | first | | | |
69// | | <---- | | | |
70// | | | | | |
71// | @class A | link | @interface A | link | @class A |
72// | seen first | <---- | seen second | <---- | seen third |
73// | | | | | |
74// +------------+ +--------------+ +--------------+
75// | data | defn | data | defn | data |
76// | | ----> | | <---- | |
77// +------------+ +--------------+ +--------------+
78// | | ^ ^
79// | |defn | |
80// | link +-----+ |
81// +-->-------------------------------------------+
82
83/// Provides common interface for the Decls that can be redeclared.
84template<typename decl_type>
85class Redeclarable {
86protected:
87 class DeclLink {
88 /// A pointer to a known latest declaration, either statically known or
89 /// generationally updated as decls are added by an external source.
90 using KnownLatest =
91 LazyGenerationalUpdatePtr<const Decl *, Decl *,
92 &ExternalASTSource::CompleteRedeclChain>;
93
94 /// We store a pointer to the ASTContext in the UninitializedLatest
95 /// pointer, but to avoid circular type dependencies when we steal the low
96 /// bits of this pointer, we use a raw void* here.
97 using UninitializedLatest = const void *;
98
99 using Previous = Decl *;
100
101 /// A pointer to either an uninitialized latest declaration (where either
102 /// we've not yet set the previous decl or there isn't one), or to a known
103 /// previous declaration.
104 using NotKnownLatest = llvm::PointerUnion<Previous, UninitializedLatest>;
105
106 mutable llvm::PointerUnion<NotKnownLatest, KnownLatest> Link;
107
108 public:
109 enum PreviousTag { PreviousLink };
110 enum LatestTag { LatestLink };
111
112 DeclLink(LatestTag, const ASTContext &Ctx)
113 : Link(NotKnownLatest(reinterpret_cast<UninitializedLatest>(&Ctx))) {}
114 DeclLink(PreviousTag, decl_type *D) : Link(NotKnownLatest(Previous(D))) {}
115
116 bool isFirst() const {
117 return Link.is<KnownLatest>() ||
118 // FIXME: 'template' is required on the next line due to an
119 // apparent clang bug.
120 Link.get<NotKnownLatest>().template is<UninitializedLatest>();
121 }
122
123 decl_type *getPrevious(const decl_type *D) const {
124 if (Link.is<NotKnownLatest>()) {
125 NotKnownLatest NKL = Link.get<NotKnownLatest>();
126 if (NKL.is<Previous>())
127 return static_cast<decl_type*>(NKL.get<Previous>());
128
129 // Allocate the generational 'most recent' cache now, if needed.
130 Link = KnownLatest(*reinterpret_cast<const ASTContext *>(
131 NKL.get<UninitializedLatest>()),
132 const_cast<decl_type *>(D));
133 }
134
135 return static_cast<decl_type*>(Link.get<KnownLatest>().get(D));
136 }
137
138 void setPrevious(decl_type *D) {
139 assert(!isFirst() && "decl became non-canonical unexpectedly");
140 Link = Previous(D);
141 }
142
143 void setLatest(decl_type *D) {
144 assert(isFirst() && "decl became canonical unexpectedly");
145 if (Link.is<NotKnownLatest>()) {
146 NotKnownLatest NKL = Link.get<NotKnownLatest>();
147 Link = KnownLatest(*reinterpret_cast<const ASTContext *>(
148 NKL.get<UninitializedLatest>()),
149 D);
150 } else {
151 auto Latest = Link.get<KnownLatest>();
152 Latest.set(D);
153 Link = Latest;
154 }
155 }
156
157 void markIncomplete() { Link.get<KnownLatest>().markIncomplete(); }
158
159 Decl *getLatestNotUpdated() const {
160 assert(isFirst() && "expected a canonical decl");
161 if (Link.is<NotKnownLatest>())
162 return nullptr;
163 return Link.get<KnownLatest>().getNotUpdated();
164 }
165 };
166
167 static DeclLink PreviousDeclLink(decl_type *D) {
168 return DeclLink(DeclLink::PreviousLink, D);
169 }
170
171 static DeclLink LatestDeclLink(const ASTContext &Ctx) {
172 return DeclLink(DeclLink::LatestLink, Ctx);
173 }
174
175 /// Points to the next redeclaration in the chain.
176 ///
177 /// If isFirst() is false, this is a link to the previous declaration
178 /// of this same Decl. If isFirst() is true, this is the first
179 /// declaration and Link points to the latest declaration. For example:
180 ///
181 /// #1 int f(int x, int y = 1); // <pointer to #3, true>
182 /// #2 int f(int x = 0, int y); // <pointer to #1, false>
183 /// #3 int f(int x, int y) { return x + y; } // <pointer to #2, false>
184 ///
185 /// If there is only one declaration, it is <pointer to self, true>
186 DeclLink RedeclLink;
187
188 decl_type *First;
189
190 decl_type *getNextRedeclaration() const {
191 return RedeclLink.getPrevious(static_cast<const decl_type *>(this));
192 }
193
194public:
195 friend class ASTDeclReader;
196 friend class ASTDeclWriter;
197
198 Redeclarable(const ASTContext &Ctx)
199 : RedeclLink(LatestDeclLink(Ctx)),
200 First(static_cast<decl_type *>(this)) {}
201
202 /// Return the previous declaration of this declaration or NULL if this
203 /// is the first declaration.
204 decl_type *getPreviousDecl() {
205 if (!RedeclLink.isFirst())
206 return getNextRedeclaration();
207 return nullptr;
208 }
209 const decl_type *getPreviousDecl() const {
210 return const_cast<decl_type *>(
211 static_cast<const decl_type*>(this))->getPreviousDecl();
212 }
213
214 /// Return the first declaration of this declaration or itself if this
215 /// is the only declaration.
216 decl_type *getFirstDecl() { return First; }
217
218 /// Return the first declaration of this declaration or itself if this
219 /// is the only declaration.
220 const decl_type *getFirstDecl() const { return First; }
221
222 /// True if this is the first declaration in its redeclaration chain.
223 bool isFirstDecl() const { return RedeclLink.isFirst(); }
224
225 /// Returns the most recent (re)declaration of this declaration.
226 decl_type *getMostRecentDecl() {
227 return getFirstDecl()->getNextRedeclaration();
228 }
229
230 /// Returns the most recent (re)declaration of this declaration.
231 const decl_type *getMostRecentDecl() const {
232 return getFirstDecl()->getNextRedeclaration();
233 }
234
235 /// Set the previous declaration. If PrevDecl is NULL, set this as the
236 /// first and only declaration.
237 void setPreviousDecl(decl_type *PrevDecl);
238
239 /// Iterates through all the redeclarations of the same decl.
240 class redecl_iterator {
241 /// Current - The current declaration.
242 decl_type *Current = nullptr;
243 decl_type *Starter;
244 bool PassedFirst = false;
245
246 public:
247 using value_type = decl_type *;
248 using reference = decl_type *;
249 using pointer = decl_type *;
250 using iterator_category = std::forward_iterator_tag;
251 using difference_type = std::ptrdiff_t;
252
253 redecl_iterator() = default;
254 explicit redecl_iterator(decl_type *C) : Current(C), Starter(C) {}
255
256 reference operator*() const { return Current; }
257 pointer operator->() const { return Current; }
258
259 redecl_iterator& operator++() {
260 assert(Current && "Advancing while iterator has reached end");
261 // Sanity check to avoid infinite loop on invalid redecl chain.
262 if (Current->isFirstDecl()) {
263 if (PassedFirst) {
264 assert(0 && "Passed first decl twice, invalid redecl chain!");
265 Current = nullptr;
266 return *this;
267 }
268 PassedFirst = true;
269 }
270
271 // Get either previous decl or latest decl.
272 decl_type *Next = Current->getNextRedeclaration();
273 Current = (Next != Starter) ? Next : nullptr;
274 return *this;
275 }
276
277 redecl_iterator operator++(int) {
278 redecl_iterator tmp(*this);
279 ++(*this);
280 return tmp;
281 }
282
283 friend bool operator==(redecl_iterator x, redecl_iterator y) {
284 return x.Current == y.Current;
285 }
286 friend bool operator!=(redecl_iterator x, redecl_iterator y) {
287 return x.Current != y.Current;
288 }
289 };
290
291 using redecl_range = llvm::iterator_range<redecl_iterator>;
292
293 /// Returns an iterator range for all the redeclarations of the same
294 /// decl. It will iterate at least once (when this decl is the only one).
295 redecl_range redecls() const {
296 return redecl_range(redecl_iterator(const_cast<decl_type *>(
297 static_cast<const decl_type *>(this))),
298 redecl_iterator());
299 }
300
301 redecl_iterator redecls_begin() const { return redecls().begin(); }
302 redecl_iterator redecls_end() const { return redecls().end(); }
303};
304
305/// Get the primary declaration for a declaration from an AST file. That
306/// will be the first-loaded declaration.
307Decl *getPrimaryMergedDecl(Decl *D);
308
309/// Provides common interface for the Decls that cannot be redeclared,
310/// but can be merged if the same declaration is brought in from multiple
311/// modules.
312template<typename decl_type>
313class Mergeable {
314public:
315 Mergeable() = default;
316
317 /// Return the first declaration of this declaration or itself if this
318 /// is the only declaration.
319 decl_type *getFirstDecl() {
320 auto *D = static_cast<decl_type *>(this);
321 if (!D->isFromASTFile())
322 return D;
323 return cast<decl_type>(getPrimaryMergedDecl(const_cast<decl_type*>(D)));
324 }
325
326 /// Return the first declaration of this declaration or itself if this
327 /// is the only declaration.
328 const decl_type *getFirstDecl() const {
329 const auto *D = static_cast<const decl_type *>(this);
330 if (!D->isFromASTFile())
331 return D;
332 return cast<decl_type>(getPrimaryMergedDecl(const_cast<decl_type*>(D)));
333 }
334
335 /// Returns true if this is the first declaration.
336 bool isFirstDecl() const { return getFirstDecl() == this; }
337};
338
339/// A wrapper class around a pointer that always points to its canonical
340/// declaration.
341///
342/// CanonicalDeclPtr<decl_type> behaves just like decl_type*, except we call
343/// decl_type::getCanonicalDecl() on construction.
344///
345/// This is useful for hashtables that you want to be keyed on a declaration's
346/// canonical decl -- if you use CanonicalDeclPtr as the key, you don't need to
347/// remember to call getCanonicalDecl() everywhere.
348template <typename decl_type> class CanonicalDeclPtr {
349public:
350 CanonicalDeclPtr() = default;
351 CanonicalDeclPtr(decl_type *Ptr)
352 : Ptr(Ptr ? Ptr->getCanonicalDecl() : nullptr) {}
353 CanonicalDeclPtr(const CanonicalDeclPtr &) = default;
354 CanonicalDeclPtr &operator=(const CanonicalDeclPtr &) = default;
355
356 operator decl_type *() { return Ptr; }
357 operator const decl_type *() const { return Ptr; }
358
359 decl_type *operator->() { return Ptr; }
360 const decl_type *operator->() const { return Ptr; }
361
362 decl_type &operator*() { return *Ptr; }
363 const decl_type &operator*() const { return *Ptr; }
364
365private:
366 friend struct llvm::DenseMapInfo<CanonicalDeclPtr<decl_type>>;
367
368 decl_type *Ptr = nullptr;
369};
370
371} // namespace clang
372
373namespace llvm {
374
375template <typename decl_type>
376struct DenseMapInfo<clang::CanonicalDeclPtr<decl_type>> {
377 using CanonicalDeclPtr = clang::CanonicalDeclPtr<decl_type>;
378 using BaseInfo = DenseMapInfo<decl_type *>;
379
380 static CanonicalDeclPtr getEmptyKey() {
381 // Construct our CanonicalDeclPtr this way because the regular constructor
382 // would dereference P.Ptr, which is not allowed.
383 CanonicalDeclPtr P;
384 P.Ptr = BaseInfo::getEmptyKey();
385 return P;
386 }
387
388 static CanonicalDeclPtr getTombstoneKey() {
389 CanonicalDeclPtr P;
390 P.Ptr = BaseInfo::getTombstoneKey();
391 return P;
392 }
393
394 static unsigned getHashValue(const CanonicalDeclPtr &P) {
395 return BaseInfo::getHashValue(P);
396 }
397
398 static bool isEqual(const CanonicalDeclPtr &LHS,
399 const CanonicalDeclPtr &RHS) {
400 return BaseInfo::isEqual(LHS, RHS);
401 }
402};
403
404} // namespace llvm
405
406#endif // LLVM_CLANG_AST_REDECLARABLE_H
407

Warning: That file was not part of the compilation database. It may have many parsing errors.