1//===--- TransAutoreleasePool.cpp - Transformations to ARC mode -----------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// rewriteAutoreleasePool:
10//
11// Calls to NSAutoreleasePools will be rewritten as an @autorelease scope.
12//
13// NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
14// ...
15// [pool release];
16// ---->
17// @autorelease {
18// ...
19// }
20//
21// An NSAutoreleasePool will not be touched if:
22// - There is not a corresponding -release/-drain in the same scope
23// - Not all references of the NSAutoreleasePool variable can be removed
24// - There is a variable that is declared inside the intended @autorelease scope
25// which is also used outside it.
26//
27//===----------------------------------------------------------------------===//
28
29#include "Transforms.h"
30#include "Internals.h"
31#include "clang/AST/ASTContext.h"
32#include "clang/Basic/SourceManager.h"
33#include "clang/Sema/SemaDiagnostic.h"
34#include <map>
35
36using namespace clang;
37using namespace arcmt;
38using namespace trans;
39
40namespace {
41
42class ReleaseCollector : public RecursiveASTVisitor<ReleaseCollector> {
43 Decl *Dcl;
44 SmallVectorImpl<ObjCMessageExpr *> &Releases;
45
46public:
47 ReleaseCollector(Decl *D, SmallVectorImpl<ObjCMessageExpr *> &releases)
48 : Dcl(D), Releases(releases) { }
49
50 bool VisitObjCMessageExpr(ObjCMessageExpr *E) {
51 if (!E->isInstanceMessage())
52 return true;
53 if (E->getMethodFamily() != OMF_release)
54 return true;
55 Expr *instance = E->getInstanceReceiver()->IgnoreParenCasts();
56 if (DeclRefExpr *DE = dyn_cast<DeclRefExpr>(Val: instance)) {
57 if (DE->getDecl() == Dcl)
58 Releases.push_back(Elt: E);
59 }
60 return true;
61 }
62};
63
64}
65
66namespace {
67
68class AutoreleasePoolRewriter
69 : public RecursiveASTVisitor<AutoreleasePoolRewriter> {
70public:
71 AutoreleasePoolRewriter(MigrationPass &pass)
72 : Body(nullptr), Pass(pass) {
73 PoolII = &pass.Ctx.Idents.get(Name: "NSAutoreleasePool");
74 DrainSel = pass.Ctx.Selectors.getNullarySelector(
75 ID: &pass.Ctx.Idents.get(Name: "drain"));
76 }
77
78 void transformBody(Stmt *body, Decl *ParentD) {
79 Body = body;
80 TraverseStmt(S: body);
81 }
82
83 ~AutoreleasePoolRewriter() {
84 SmallVector<VarDecl *, 8> VarsToHandle;
85
86 for (std::map<VarDecl *, PoolVarInfo>::iterator
87 I = PoolVars.begin(), E = PoolVars.end(); I != E; ++I) {
88 VarDecl *var = I->first;
89 PoolVarInfo &info = I->second;
90
91 // Check that we can handle/rewrite all references of the pool.
92
93 clearRefsIn(S: info.Dcl, refs&: info.Refs);
94 for (SmallVectorImpl<PoolScope>::iterator
95 scpI = info.Scopes.begin(),
96 scpE = info.Scopes.end(); scpI != scpE; ++scpI) {
97 PoolScope &scope = *scpI;
98 clearRefsIn(S: *scope.Begin, refs&: info.Refs);
99 clearRefsIn(S: *scope.End, refs&: info.Refs);
100 clearRefsIn(begin: scope.Releases.begin(), end: scope.Releases.end(), refs&: info.Refs);
101 }
102
103 // Even if one reference is not handled we will not do anything about that
104 // pool variable.
105 if (info.Refs.empty())
106 VarsToHandle.push_back(Elt: var);
107 }
108
109 for (unsigned i = 0, e = VarsToHandle.size(); i != e; ++i) {
110 PoolVarInfo &info = PoolVars[VarsToHandle[i]];
111
112 Transaction Trans(Pass.TA);
113
114 clearUnavailableDiags(S: info.Dcl);
115 Pass.TA.removeStmt(S: info.Dcl);
116
117 // Add "@autoreleasepool { }"
118 for (SmallVectorImpl<PoolScope>::iterator
119 scpI = info.Scopes.begin(),
120 scpE = info.Scopes.end(); scpI != scpE; ++scpI) {
121 PoolScope &scope = *scpI;
122 clearUnavailableDiags(S: *scope.Begin);
123 clearUnavailableDiags(S: *scope.End);
124 if (scope.IsFollowedBySimpleReturnStmt) {
125 // Include the return in the scope.
126 Pass.TA.replaceStmt(S: *scope.Begin, text: "@autoreleasepool {");
127 Pass.TA.removeStmt(S: *scope.End);
128 Stmt::child_iterator retI = scope.End;
129 ++retI;
130 SourceLocation afterSemi =
131 findLocationAfterSemi(loc: (*retI)->getEndLoc(), Ctx&: Pass.Ctx);
132 assert(afterSemi.isValid() &&
133 "Didn't we check before setting IsFollowedBySimpleReturnStmt "
134 "to true?");
135 Pass.TA.insertAfterToken(loc: afterSemi, text: "\n}");
136 Pass.TA.increaseIndentation(
137 range: SourceRange(scope.getIndentedRange().getBegin(),
138 (*retI)->getEndLoc()),
139 parentIndent: scope.CompoundParent->getBeginLoc());
140 } else {
141 Pass.TA.replaceStmt(S: *scope.Begin, text: "@autoreleasepool {");
142 Pass.TA.replaceStmt(S: *scope.End, text: "}");
143 Pass.TA.increaseIndentation(range: scope.getIndentedRange(),
144 parentIndent: scope.CompoundParent->getBeginLoc());
145 }
146 }
147
148 // Remove rest of pool var references.
149 for (SmallVectorImpl<PoolScope>::iterator
150 scpI = info.Scopes.begin(),
151 scpE = info.Scopes.end(); scpI != scpE; ++scpI) {
152 PoolScope &scope = *scpI;
153 for (SmallVectorImpl<ObjCMessageExpr *>::iterator
154 relI = scope.Releases.begin(),
155 relE = scope.Releases.end(); relI != relE; ++relI) {
156 clearUnavailableDiags(S: *relI);
157 Pass.TA.removeStmt(S: *relI);
158 }
159 }
160 }
161 }
162
163 bool VisitCompoundStmt(CompoundStmt *S) {
164 SmallVector<PoolScope, 4> Scopes;
165
166 for (Stmt::child_iterator
167 I = S->body_begin(), E = S->body_end(); I != E; ++I) {
168 Stmt *child = getEssential(S: *I);
169 if (DeclStmt *DclS = dyn_cast<DeclStmt>(Val: child)) {
170 if (DclS->isSingleDecl()) {
171 if (VarDecl *VD = dyn_cast<VarDecl>(Val: DclS->getSingleDecl())) {
172 if (isNSAutoreleasePool(Ty: VD->getType())) {
173 PoolVarInfo &info = PoolVars[VD];
174 info.Dcl = DclS;
175 collectRefs(D: VD, S, refs&: info.Refs);
176 // Does this statement follow the pattern:
177 // NSAutoreleasePool * pool = [NSAutoreleasePool new];
178 if (isPoolCreation(E: VD->getInit())) {
179 Scopes.push_back(Elt: PoolScope());
180 Scopes.back().PoolVar = VD;
181 Scopes.back().CompoundParent = S;
182 Scopes.back().Begin = I;
183 }
184 }
185 }
186 }
187 } else if (BinaryOperator *bop = dyn_cast<BinaryOperator>(Val: child)) {
188 if (DeclRefExpr *dref = dyn_cast<DeclRefExpr>(Val: bop->getLHS())) {
189 if (VarDecl *VD = dyn_cast<VarDecl>(Val: dref->getDecl())) {
190 // Does this statement follow the pattern:
191 // pool = [NSAutoreleasePool new];
192 if (isNSAutoreleasePool(Ty: VD->getType()) &&
193 isPoolCreation(E: bop->getRHS())) {
194 Scopes.push_back(Elt: PoolScope());
195 Scopes.back().PoolVar = VD;
196 Scopes.back().CompoundParent = S;
197 Scopes.back().Begin = I;
198 }
199 }
200 }
201 }
202
203 if (Scopes.empty())
204 continue;
205
206 if (isPoolDrain(poolVar: Scopes.back().PoolVar, S: child)) {
207 PoolScope &scope = Scopes.back();
208 scope.End = I;
209 handlePoolScope(scope, compoundS: S);
210 Scopes.pop_back();
211 }
212 }
213 return true;
214 }
215
216private:
217 void clearUnavailableDiags(Stmt *S) {
218 if (S)
219 Pass.TA.clearDiagnostic(ID1: diag::err_unavailable,
220 ID2: diag::err_unavailable_message,
221 range: S->getSourceRange());
222 }
223
224 struct PoolScope {
225 VarDecl *PoolVar;
226 CompoundStmt *CompoundParent;
227 Stmt::child_iterator Begin;
228 Stmt::child_iterator End;
229 bool IsFollowedBySimpleReturnStmt;
230 SmallVector<ObjCMessageExpr *, 4> Releases;
231
232 PoolScope()
233 : PoolVar(nullptr), CompoundParent(nullptr),
234 IsFollowedBySimpleReturnStmt(false) {}
235
236 SourceRange getIndentedRange() const {
237 Stmt::child_iterator rangeS = Begin;
238 ++rangeS;
239 if (rangeS == End)
240 return SourceRange();
241 Stmt::child_iterator rangeE = Begin;
242 for (Stmt::child_iterator I = rangeS; I != End; ++I)
243 ++rangeE;
244 return SourceRange((*rangeS)->getBeginLoc(), (*rangeE)->getEndLoc());
245 }
246 };
247
248 class NameReferenceChecker : public RecursiveASTVisitor<NameReferenceChecker>{
249 ASTContext &Ctx;
250 SourceRange ScopeRange;
251 SourceLocation &referenceLoc, &declarationLoc;
252
253 public:
254 NameReferenceChecker(ASTContext &ctx, PoolScope &scope,
255 SourceLocation &referenceLoc,
256 SourceLocation &declarationLoc)
257 : Ctx(ctx), referenceLoc(referenceLoc),
258 declarationLoc(declarationLoc) {
259 ScopeRange = SourceRange((*scope.Begin)->getBeginLoc(),
260 (*scope.End)->getBeginLoc());
261 }
262
263 bool VisitDeclRefExpr(DeclRefExpr *E) {
264 return checkRef(refLoc: E->getLocation(), declLoc: E->getDecl()->getLocation());
265 }
266
267 bool VisitTypedefTypeLoc(TypedefTypeLoc TL) {
268 return checkRef(refLoc: TL.getBeginLoc(), declLoc: TL.getTypedefNameDecl()->getLocation());
269 }
270
271 bool VisitTagTypeLoc(TagTypeLoc TL) {
272 return checkRef(refLoc: TL.getBeginLoc(), declLoc: TL.getDecl()->getLocation());
273 }
274
275 private:
276 bool checkRef(SourceLocation refLoc, SourceLocation declLoc) {
277 if (isInScope(loc: declLoc)) {
278 referenceLoc = refLoc;
279 declarationLoc = declLoc;
280 return false;
281 }
282 return true;
283 }
284
285 bool isInScope(SourceLocation loc) {
286 if (loc.isInvalid())
287 return false;
288
289 SourceManager &SM = Ctx.getSourceManager();
290 if (SM.isBeforeInTranslationUnit(LHS: loc, RHS: ScopeRange.getBegin()))
291 return false;
292 return SM.isBeforeInTranslationUnit(LHS: loc, RHS: ScopeRange.getEnd());
293 }
294 };
295
296 void handlePoolScope(PoolScope &scope, CompoundStmt *compoundS) {
297 // Check that all names declared inside the scope are not used
298 // outside the scope.
299 {
300 bool nameUsedOutsideScope = false;
301 SourceLocation referenceLoc, declarationLoc;
302 Stmt::child_iterator SI = scope.End, SE = compoundS->body_end();
303 ++SI;
304 // Check if the autoreleasepool scope is followed by a simple return
305 // statement, in which case we will include the return in the scope.
306 if (SI != SE)
307 if (ReturnStmt *retS = dyn_cast<ReturnStmt>(Val: *SI))
308 if ((retS->getRetValue() == nullptr ||
309 isa<DeclRefExpr>(Val: retS->getRetValue()->IgnoreParenCasts())) &&
310 findLocationAfterSemi(loc: retS->getEndLoc(), Ctx&: Pass.Ctx).isValid()) {
311 scope.IsFollowedBySimpleReturnStmt = true;
312 ++SI; // the return will be included in scope, don't check it.
313 }
314
315 for (; SI != SE; ++SI) {
316 nameUsedOutsideScope = !NameReferenceChecker(Pass.Ctx, scope,
317 referenceLoc,
318 declarationLoc).TraverseStmt(S: *SI);
319 if (nameUsedOutsideScope)
320 break;
321 }
322
323 // If not all references were cleared it means some variables/typenames/etc
324 // declared inside the pool scope are used outside of it.
325 // We won't try to rewrite the pool.
326 if (nameUsedOutsideScope) {
327 Pass.TA.reportError(error: "a name is referenced outside the "
328 "NSAutoreleasePool scope that it was declared in", loc: referenceLoc);
329 Pass.TA.reportNote(note: "name declared here", loc: declarationLoc);
330 Pass.TA.reportNote(note: "intended @autoreleasepool scope begins here",
331 loc: (*scope.Begin)->getBeginLoc());
332 Pass.TA.reportNote(note: "intended @autoreleasepool scope ends here",
333 loc: (*scope.End)->getBeginLoc());
334 return;
335 }
336 }
337
338 // Collect all releases of the pool; they will be removed.
339 {
340 ReleaseCollector releaseColl(scope.PoolVar, scope.Releases);
341 Stmt::child_iterator I = scope.Begin;
342 ++I;
343 for (; I != scope.End; ++I)
344 releaseColl.TraverseStmt(S: *I);
345 }
346
347 PoolVars[scope.PoolVar].Scopes.push_back(Elt: scope);
348 }
349
350 bool isPoolCreation(Expr *E) {
351 if (!E) return false;
352 E = getEssential(E);
353 ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(Val: E);
354 if (!ME) return false;
355 if (ME->getMethodFamily() == OMF_new &&
356 ME->getReceiverKind() == ObjCMessageExpr::Class &&
357 isNSAutoreleasePool(IDecl: ME->getReceiverInterface()))
358 return true;
359 if (ME->getReceiverKind() == ObjCMessageExpr::Instance &&
360 ME->getMethodFamily() == OMF_init) {
361 Expr *rec = getEssential(E: ME->getInstanceReceiver());
362 if (ObjCMessageExpr *recME = dyn_cast_or_null<ObjCMessageExpr>(Val: rec)) {
363 if (recME->getMethodFamily() == OMF_alloc &&
364 recME->getReceiverKind() == ObjCMessageExpr::Class &&
365 isNSAutoreleasePool(IDecl: recME->getReceiverInterface()))
366 return true;
367 }
368 }
369
370 return false;
371 }
372
373 bool isPoolDrain(VarDecl *poolVar, Stmt *S) {
374 if (!S) return false;
375 S = getEssential(S);
376 ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(Val: S);
377 if (!ME) return false;
378 if (ME->getReceiverKind() == ObjCMessageExpr::Instance) {
379 Expr *rec = getEssential(E: ME->getInstanceReceiver());
380 if (DeclRefExpr *dref = dyn_cast<DeclRefExpr>(Val: rec))
381 if (dref->getDecl() == poolVar)
382 return ME->getMethodFamily() == OMF_release ||
383 ME->getSelector() == DrainSel;
384 }
385
386 return false;
387 }
388
389 bool isNSAutoreleasePool(ObjCInterfaceDecl *IDecl) {
390 return IDecl && IDecl->getIdentifier() == PoolII;
391 }
392
393 bool isNSAutoreleasePool(QualType Ty) {
394 QualType pointee = Ty->getPointeeType();
395 if (pointee.isNull())
396 return false;
397 if (const ObjCInterfaceType *interT = pointee->getAs<ObjCInterfaceType>())
398 return isNSAutoreleasePool(IDecl: interT->getDecl());
399 return false;
400 }
401
402 static Expr *getEssential(Expr *E) {
403 return cast<Expr>(Val: getEssential(S: (Stmt*)E));
404 }
405 static Stmt *getEssential(Stmt *S) {
406 if (FullExpr *FE = dyn_cast<FullExpr>(Val: S))
407 S = FE->getSubExpr();
408 if (Expr *E = dyn_cast<Expr>(Val: S))
409 S = E->IgnoreParenCasts();
410 return S;
411 }
412
413 Stmt *Body;
414 MigrationPass &Pass;
415
416 IdentifierInfo *PoolII;
417 Selector DrainSel;
418
419 struct PoolVarInfo {
420 DeclStmt *Dcl = nullptr;
421 ExprSet Refs;
422 SmallVector<PoolScope, 2> Scopes;
423
424 PoolVarInfo() = default;
425 };
426
427 std::map<VarDecl *, PoolVarInfo> PoolVars;
428};
429
430} // anonymous namespace
431
432void trans::rewriteAutoreleasePool(MigrationPass &pass) {
433 BodyTransform<AutoreleasePoolRewriter> trans(pass);
434 trans.TraverseDecl(D: pass.Ctx.getTranslationUnitDecl());
435}
436