1 //===--- TransEmptyStatements.cpp - Tranformations to ARC mode ------------===//
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 // removeEmptyStatementsAndDealloc:
11 //
12 // Removes empty statements that are leftovers from previous transformations.
13 // e.g for
14 //
15 //  [x retain];
16 //
17 // removeRetainReleaseDealloc will leave an empty ";" that removeEmptyStatements
18 // will remove.
19 //
20 //===----------------------------------------------------------------------===//
21 
22 #include "Transforms.h"
23 #include "Internals.h"
24 #include "clang/AST/StmtVisitor.h"
25 
26 using namespace clang;
27 using namespace arcmt;
28 using namespace trans;
29 
30 namespace {
31 
32 /// \brief Returns true if the statement became empty due to previous
33 /// transformations.
34 class EmptyChecker : public StmtVisitor<EmptyChecker, bool> {
35   ASTContext &Ctx;
36   llvm::DenseSet<unsigned> &MacroLocs;
37 
38 public:
39   EmptyChecker(ASTContext &ctx, llvm::DenseSet<unsigned> &macroLocs)
40     : Ctx(ctx), MacroLocs(macroLocs) { }
41 
42   bool VisitNullStmt(NullStmt *S) {
43     return isMacroLoc(S->getLeadingEmptyMacroLoc());
44   }
45   bool VisitCompoundStmt(CompoundStmt *S) {
46     if (S->body_empty())
47       return false; // was already empty, not because of transformations.
48     for (CompoundStmt::body_iterator
49            I = S->body_begin(), E = S->body_end(); I != E; ++I)
50       if (!Visit(*I))
51         return false;
52     return true;
53   }
54   bool VisitIfStmt(IfStmt *S) {
55     if (S->getConditionVariable())
56       return false;
57     Expr *condE = S->getCond();
58     if (!condE)
59       return false;
60     if (hasSideEffects(condE, Ctx))
61       return false;
62     if (!S->getThen() || !Visit(S->getThen()))
63       return false;
64     if (S->getElse() && !Visit(S->getElse()))
65       return false;
66     return true;
67   }
68   bool VisitWhileStmt(WhileStmt *S) {
69     if (S->getConditionVariable())
70       return false;
71     Expr *condE = S->getCond();
72     if (!condE)
73       return false;
74     if (hasSideEffects(condE, Ctx))
75       return false;
76     if (!S->getBody())
77       return false;
78     return Visit(S->getBody());
79   }
80   bool VisitDoStmt(DoStmt *S) {
81     Expr *condE = S->getCond();
82     if (!condE)
83       return false;
84     if (hasSideEffects(condE, Ctx))
85       return false;
86     if (!S->getBody())
87       return false;
88     return Visit(S->getBody());
89   }
90   bool VisitObjCForCollectionStmt(ObjCForCollectionStmt *S) {
91     Expr *Exp = S->getCollection();
92     if (!Exp)
93       return false;
94     if (hasSideEffects(Exp, Ctx))
95       return false;
96     if (!S->getBody())
97       return false;
98     return Visit(S->getBody());
99   }
100   bool VisitObjCAutoreleasePoolStmt(ObjCAutoreleasePoolStmt *S) {
101     if (!S->getSubStmt())
102       return false;
103     return Visit(S->getSubStmt());
104   }
105 
106 private:
107   bool isMacroLoc(SourceLocation loc) {
108     if (loc.isInvalid()) return false;
109     return MacroLocs.count(loc.getRawEncoding());
110   }
111 };
112 
113 class EmptyStatementsRemover :
114                             public RecursiveASTVisitor<EmptyStatementsRemover> {
115   MigrationPass &Pass;
116   llvm::DenseSet<unsigned> &MacroLocs;
117 
118 public:
119   EmptyStatementsRemover(MigrationPass &pass,
120                          llvm::DenseSet<unsigned> &macroLocs)
121     : Pass(pass), MacroLocs(macroLocs) { }
122 
123   bool TraverseStmtExpr(StmtExpr *E) {
124     CompoundStmt *S = E->getSubStmt();
125     for (CompoundStmt::body_iterator
126            I = S->body_begin(), E = S->body_end(); I != E; ++I) {
127       if (I != E - 1)
128         check(*I);
129       TraverseStmt(*I);
130     }
131     return true;
132   }
133 
134   bool VisitCompoundStmt(CompoundStmt *S) {
135     for (CompoundStmt::body_iterator
136            I = S->body_begin(), E = S->body_end(); I != E; ++I)
137       check(*I);
138     return true;
139   }
140 
141   bool isMacroLoc(SourceLocation loc) {
142     if (loc.isInvalid()) return false;
143     return MacroLocs.count(loc.getRawEncoding());
144   }
145 
146   ASTContext &getContext() { return Pass.Ctx; }
147 
148 private:
149   void check(Stmt *S) {
150     if (!S) return;
151     if (EmptyChecker(Pass.Ctx, MacroLocs).Visit(S)) {
152       Transaction Trans(Pass.TA);
153       Pass.TA.removeStmt(S);
154     }
155   }
156 };
157 
158 } // anonymous namespace
159 
160 static bool isBodyEmpty(CompoundStmt *body,
161                         ASTContext &Ctx, llvm::DenseSet<unsigned> &MacroLocs) {
162   for (CompoundStmt::body_iterator
163          I = body->body_begin(), E = body->body_end(); I != E; ++I)
164     if (!EmptyChecker(Ctx, MacroLocs).Visit(*I))
165       return false;
166 
167   return true;
168 }
169 
170 static void removeDeallocMethod(MigrationPass &pass,
171                                 llvm::DenseSet<unsigned> &MacroLocs) {
172   ASTContext &Ctx = pass.Ctx;
173   TransformActions &TA = pass.TA;
174   DeclContext *DC = Ctx.getTranslationUnitDecl();
175 
176   typedef DeclContext::specific_decl_iterator<ObjCImplementationDecl>
177     impl_iterator;
178   for (impl_iterator I = impl_iterator(DC->decls_begin()),
179                      E = impl_iterator(DC->decls_end()); I != E; ++I) {
180     for (ObjCImplementationDecl::instmeth_iterator
181            MI = (*I)->instmeth_begin(),
182            ME = (*I)->instmeth_end(); MI != ME; ++MI) {
183       ObjCMethodDecl *MD = *MI;
184       if (MD->getMethodFamily() == OMF_dealloc) {
185         if (MD->hasBody() &&
186             isBodyEmpty(MD->getCompoundBody(), Ctx, MacroLocs)) {
187           Transaction Trans(TA);
188           TA.remove(MD->getSourceRange());
189         }
190         break;
191       }
192     }
193   }
194 }
195 
196 void trans::removeEmptyStatementsAndDealloc(MigrationPass &pass) {
197   llvm::DenseSet<unsigned> MacroLocs;
198   for (unsigned i = 0, e = pass.ARCMTMacroLocs.size(); i != e; ++i)
199     MacroLocs.insert(pass.ARCMTMacroLocs[i].getRawEncoding());
200 
201   EmptyStatementsRemover(pass, MacroLocs)
202     .TraverseDecl(pass.Ctx.getTranslationUnitDecl());
203 
204   removeDeallocMethod(pass, MacroLocs);
205 
206   for (unsigned i = 0, e = pass.ARCMTMacroLocs.size(); i != e; ++i) {
207     Transaction Trans(pass.TA);
208     pass.TA.remove(pass.ARCMTMacroLocs[i]);
209   }
210 }
211