clang 19.0.0git
TransBlockObjCVariable.cpp
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1//===--- TransBlockObjCVariable.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// rewriteBlockObjCVariable:
10//
11// Adding __block to an obj-c variable could be either because the variable
12// is used for output storage or the user wanted to break a retain cycle.
13// This transformation checks whether a reference of the variable for the block
14// is actually needed (it is assigned to or its address is taken) or not.
15// If the reference is not needed it will assume __block was added to break a
16// cycle so it will remove '__block' and add __weak/__unsafe_unretained.
17// e.g
18//
19// __block Foo *x;
20// bar(^ { [x cake]; });
21// ---->
22// __weak Foo *x;
23// bar(^ { [x cake]; });
24//
25//===----------------------------------------------------------------------===//
26
27#include "Transforms.h"
28#include "Internals.h"
30#include "clang/AST/Attr.h"
32
33using namespace clang;
34using namespace arcmt;
35using namespace trans;
36
37namespace {
38
39class RootBlockObjCVarRewriter :
40 public RecursiveASTVisitor<RootBlockObjCVarRewriter> {
41 llvm::DenseSet<VarDecl *> &VarsToChange;
42
43 class BlockVarChecker : public RecursiveASTVisitor<BlockVarChecker> {
44 VarDecl *Var;
45
47 public:
48 BlockVarChecker(VarDecl *var) : Var(var) { }
49
50 bool TraverseImplicitCastExpr(ImplicitCastExpr *castE) {
51 if (DeclRefExpr *
52 ref = dyn_cast<DeclRefExpr>(castE->getSubExpr())) {
53 if (ref->getDecl() == Var) {
54 if (castE->getCastKind() == CK_LValueToRValue)
55 return true; // Using the value of the variable.
56 if (castE->getCastKind() == CK_NoOp && castE->isLValue() &&
57 Var->getASTContext().getLangOpts().CPlusPlus)
58 return true; // Binding to const C++ reference.
59 }
60 }
61
62 return base::TraverseImplicitCastExpr(castE);
63 }
64
65 bool VisitDeclRefExpr(DeclRefExpr *E) {
66 if (E->getDecl() == Var)
67 return false; // The reference of the variable, and not just its value,
68 // is needed.
69 return true;
70 }
71 };
72
73public:
74 RootBlockObjCVarRewriter(llvm::DenseSet<VarDecl *> &VarsToChange)
75 : VarsToChange(VarsToChange) { }
76
77 bool VisitBlockDecl(BlockDecl *block) {
79
80 for (const auto &I : block->captures()) {
81 VarDecl *var = I.getVariable();
82 if (I.isByRef() &&
83 var->getType()->isObjCObjectPointerType() &&
84 isImplicitStrong(var->getType())) {
85 BlockVars.push_back(var);
86 }
87 }
88
89 for (unsigned i = 0, e = BlockVars.size(); i != e; ++i) {
90 VarDecl *var = BlockVars[i];
91
92 BlockVarChecker checker(var);
93 bool onlyValueOfVarIsNeeded = checker.TraverseStmt(block->getBody());
94 if (onlyValueOfVarIsNeeded)
95 VarsToChange.insert(var);
96 else
97 VarsToChange.erase(var);
98 }
99
100 return true;
101 }
102
103private:
104 bool isImplicitStrong(QualType ty) {
105 if (isa<AttributedType>(ty.getTypePtr()))
106 return false;
108 }
109};
110
111class BlockObjCVarRewriter : public RecursiveASTVisitor<BlockObjCVarRewriter> {
112 llvm::DenseSet<VarDecl *> &VarsToChange;
113
114public:
115 BlockObjCVarRewriter(llvm::DenseSet<VarDecl *> &VarsToChange)
116 : VarsToChange(VarsToChange) { }
117
118 bool TraverseBlockDecl(BlockDecl *block) {
119 RootBlockObjCVarRewriter(VarsToChange).TraverseDecl(block);
120 return true;
121 }
122};
123
124} // anonymous namespace
125
127 MigrationPass &Pass = BodyCtx.getMigrationContext().Pass;
128 llvm::DenseSet<VarDecl *> VarsToChange;
129
130 BlockObjCVarRewriter trans(VarsToChange);
131 trans.TraverseStmt(BodyCtx.getTopStmt());
132
134 I = VarsToChange.begin(), E = VarsToChange.end(); I != E; ++I) {
135 VarDecl *var = *I;
136 BlocksAttr *attr = var->getAttr<BlocksAttr>();
137 if(!attr)
138 continue;
139 bool useWeak = canApplyWeak(Pass.Ctx, var->getType());
141 Transaction Trans(Pass.TA);
142 Pass.TA.replaceText(SM.getExpansionLoc(attr->getLocation()),
143 "__block",
144 useWeak ? "__weak" : "__unsafe_unretained");
145 }
146}
Defines the clang::ASTContext interface.
#define SM(sm)
Definition: Cuda.cpp:84
Defines the SourceManager interface.
SourceManager & getSourceManager()
Definition: ASTContext.h:708
const LangOptions & getLangOpts() const
Definition: ASTContext.h:778
Represents a block literal declaration, which is like an unnamed FunctionDecl.
Definition: Decl.h:4496
Stmt * getBody() const override
getBody - If this Decl represents a declaration for a body of code, such as a function or method defi...
Definition: Decl.h:4575
ArrayRef< Capture > captures() const
Definition: Decl.h:4623
CastKind getCastKind() const
Definition: Expr.h:3527
Expr * getSubExpr()
Definition: Expr.h:3533
A reference to a declared variable, function, enum, etc.
Definition: Expr.h:1260
ValueDecl * getDecl()
Definition: Expr.h:1328
ASTContext & getASTContext() const LLVM_READONLY
Definition: DeclBase.cpp:523
bool isLValue() const
isLValue - True if this expression is an "l-value" according to the rules of the current language.
Definition: Expr.h:277
ImplicitCastExpr - Allows us to explicitly represent implicit type conversions, which have no direct ...
Definition: Expr.h:3655
A (possibly-)qualified type.
Definition: Type.h:940
const Type * getTypePtr() const
Retrieves a pointer to the underlying (unqualified) type.
Definition: Type.h:7375
Qualifiers getLocalQualifiers() const
Retrieve the set of qualifiers local to this particular QualType instance, not including any qualifie...
Definition: Type.h:7407
@ OCL_Strong
Assigning into this object requires the old value to be released and the new value to be retained.
Definition: Type.h:347
ObjCLifetime getObjCLifetime() const
Definition: Type.h:531
A class that does preorder or postorder depth-first traversal on the entire Clang AST and visits each...
This class handles loading and caching of source files into memory.
Represents a variable declaration or definition.
Definition: Decl.h:918
TransformActions & TA
Definition: Internals.h:152
void replaceText(SourceLocation loc, StringRef text, StringRef replacementText)
MigrationContext & getMigrationContext()
Definition: Transforms.h:54
bool canApplyWeak(ASTContext &Ctx, QualType type, bool AllowOnUnknownClass=false)
Determine whether we can add weak to the given type.
Definition: Transforms.cpp:39
const internal::VariadicAllOfMatcher< Attr > attr
Matches attributes.
constexpr Variable var(Literal L)
Returns the variable of L.
Definition: CNFFormula.h:64
The JSON file list parser is used to communicate input to InstallAPI.