1 files changed, 150 insertions, 0 deletions
diff --git a/clang/lib/ARCMigrate/TransBlockObjCVariable.cpp b/clang/lib/ARCMigrate/TransBlockObjCVariable.cpp
new file mode 100644
index 0000000..3be8132
--- /dev/null
+++ b/clang/lib/ARCMigrate/TransBlockObjCVariable.cpp
@@ -0,0 +1,150 @@
+//===--- TransBlockObjCVariable.cpp - Tranformations to ARC mode ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// rewriteBlockObjCVariable:
+//
+// Adding __block to an obj-c variable could be either because the the variable
+// is used for output storage or the user wanted to break a retain cycle.
+// This transformation checks whether a reference of the variable for the block
+// is actually needed (it is assigned to or its address is taken) or not.
+// If the reference is not needed it will assume __block was added to break a
+// cycle so it will remove '__block' and add __weak/__unsafe_unretained.
+// e.g
+//
+//   __block Foo *x;
+//   bar(^ { [x cake]; });
+// ---->
+//   __weak Foo *x;
+//   bar(^ { [x cake]; });
+//
+//===----------------------------------------------------------------------===//
+
+#include "Transforms.h"
+#include "Internals.h"
+#include "clang/Basic/SourceManager.h"
+
+using namespace clang;
+using namespace arcmt;
+using namespace trans;
+
+namespace {
+
+class RootBlockObjCVarRewriter :
+                          public RecursiveASTVisitor<RootBlockObjCVarRewriter> {
+  MigrationPass &Pass;
+  llvm::DenseSet<VarDecl *> &VarsToChange;
+
+  class BlockVarChecker : public RecursiveASTVisitor<BlockVarChecker> {
+    VarDecl *Var;
+  
+    typedef RecursiveASTVisitor<BlockVarChecker> base;
+  public:
+    BlockVarChecker(VarDecl *var) : Var(var) { }
+  
+    bool TraverseImplicitCastExpr(ImplicitCastExpr *castE) {
+      if (DeclRefExpr *
+            ref = dyn_cast<DeclRefExpr>(castE->getSubExpr())) {
+        if (ref->getDecl() == Var) {
+          if (castE->getCastKind() == CK_LValueToRValue)
+            return true; // Using the value of the variable.
+          if (castE->getCastKind() == CK_NoOp && castE->isLValue() &&
+              Var->getASTContext().getLangOpts().CPlusPlus)
+            return true; // Binding to const C++ reference.
+        }
+      }
+
+      return base::TraverseImplicitCastExpr(castE);
+    }
+
+    bool VisitDeclRefExpr(DeclRefExpr *E) {
+      if (E->getDecl() == Var)
+        return false; // The reference of the variable, and not just its value,
+                      //  is needed.
+      return true;
+    }
+  };
+
+public:
+  RootBlockObjCVarRewriter(MigrationPass &pass,
+                           llvm::DenseSet<VarDecl *> &VarsToChange)
+    : Pass(pass), VarsToChange(VarsToChange) { }
+
+  bool VisitBlockDecl(BlockDecl *block) {
+    SmallVector<VarDecl *, 4> BlockVars;
+    
+    for (BlockDecl::capture_iterator
+           I = block->capture_begin(), E = block->capture_end(); I != E; ++I) {
+      VarDecl *var = I->getVariable();
+      if (I->isByRef() &&
+          var->getType()->isObjCObjectPointerType() &&
+          isImplicitStrong(var->getType())) {
+        BlockVars.push_back(var);
+      }
+    }
+
+    for (unsigned i = 0, e = BlockVars.size(); i != e; ++i) {
+      VarDecl *var = BlockVars[i];
+
+      BlockVarChecker checker(var);
+      bool onlyValueOfVarIsNeeded = checker.TraverseStmt(block->getBody());
+      if (onlyValueOfVarIsNeeded)
+        VarsToChange.insert(var);
+      else
+        VarsToChange.erase(var);
+    }
+
+    return true;
+  }
+
+private:
+  bool isImplicitStrong(QualType ty) {
+    if (isa<AttributedType>(ty.getTypePtr()))
+      return false;
+    return ty.getLocalQualifiers().getObjCLifetime() == Qualifiers::OCL_Strong;
+  }
+};
+
+class BlockObjCVarRewriter : public RecursiveASTVisitor<BlockObjCVarRewriter> {
+  MigrationPass &Pass;
+  llvm::DenseSet<VarDecl *> &VarsToChange;
+
+public:
+  BlockObjCVarRewriter(MigrationPass &pass,
+                       llvm::DenseSet<VarDecl *> &VarsToChange)
+    : Pass(pass), VarsToChange(VarsToChange) { }
+
+  bool TraverseBlockDecl(BlockDecl *block) {
+    RootBlockObjCVarRewriter(Pass, VarsToChange).TraverseDecl(block);
+    return true;
+  }
+};
+
+} // anonymous namespace
+
+void BlockObjCVariableTraverser::traverseBody(BodyContext &BodyCtx) {
+  MigrationPass &Pass = BodyCtx.getMigrationContext().Pass;
+  llvm::DenseSet<VarDecl *> VarsToChange;
+
+  BlockObjCVarRewriter trans(Pass, VarsToChange);
+  trans.TraverseStmt(BodyCtx.getTopStmt());
+
+  for (llvm::DenseSet<VarDecl *>::iterator
+         I = VarsToChange.begin(), E = VarsToChange.end(); I != E; ++I) {
+    VarDecl *var = *I;
+    BlocksAttr *attr = var->getAttr<BlocksAttr>();
+    if(!attr)
+      continue;
+    bool useWeak = canApplyWeak(Pass.Ctx, var->getType());
+    SourceManager &SM = Pass.Ctx.getSourceManager();
+    Transaction Trans(Pass.TA);
+    Pass.TA.replaceText(SM.getExpansionLoc(attr->getLocation()),
+                        "__block",
+                        useWeak ? "__weak" : "__unsafe_unretained");
+  }
+}