[arcmt] Don't error if an autoreleased variable is returned after the -autorelease.

rdar://12952025

llvm-svn: 171482

clang/lib/ARCMigrate/TransRetainReleaseDealloc.cpp

@@ -162,13 +162,26 @@ public:
 private:
   /// \brief Checks for idioms where an unused -autorelease is common.
   ///
-  /// Currently only returns true for this idiom which is common in property
+  /// Returns true for this idiom which is common in property
   /// setters:
   ///
   ///   [backingValue autorelease];
   ///   backingValue = [newValue retain]; // in general a +1 assign
   ///
+  /// For these as well:
+  ///
+  ///   [[var retain] autorelease];
+  ///   return var;
+  ///
   bool isCommonUnusedAutorelease(ObjCMessageExpr *E) {
+    if (isPlusOneAssignAfterAutorelease(E))
+      return true;
+    if (isReturnedAfterAutorelease(E))
+      return true;
+    return false;
+  }
+
+  bool isReturnedAfterAutorelease(ObjCMessageExpr *E) {
     Expr *Rec = E->getInstanceReceiver();
     if (!Rec)
       return false;
@@ -177,36 +190,30 @@ private:
     if (!RefD)
       return false;
 
-    Stmt *OuterS = E, *InnerS;
-    do {
-      InnerS = OuterS;
-      OuterS = StmtMap->getParent(InnerS);
-    }
-    while (OuterS && (isa<ParenExpr>(OuterS) ||
-                      isa<CastExpr>(OuterS) ||
-                      isa<ExprWithCleanups>(OuterS)));
-    
-    if (!OuterS)
-      return false;
-
-    // Find next statement after the -autorelease.
-
-    Stmt::child_iterator currChildS = OuterS->child_begin();
-    Stmt::child_iterator childE = OuterS->child_end();
-    for (; currChildS != childE; ++currChildS) {
-      if (*currChildS == InnerS)
-        break;
-    }
-    if (currChildS == childE)
-      return false;
-    ++currChildS;
-    if (currChildS == childE)
-      return false;
-
-    Stmt *nextStmt = *currChildS;
+    Stmt *nextStmt = getNextStmt(E);
+    if (!nextStmt)
+      return false;
+
+    // Check for "return <variable>;".
+
+    if (ReturnStmt *RetS = dyn_cast<ReturnStmt>(nextStmt))
+      return RefD == getReferencedDecl(RetS->getRetValue());
+
+    return false;
+  }
+
+  bool isPlusOneAssignAfterAutorelease(ObjCMessageExpr *E) {
+    Expr *Rec = E->getInstanceReceiver();
+    if (!Rec)
+      return false;
+
+    Decl *RefD = getReferencedDecl(Rec);
+    if (!RefD)
+      return false;
+
+    Stmt *nextStmt = getNextStmt(E);
     if (!nextStmt)
       return false;
-    nextStmt = nextStmt->IgnoreImplicit();
 
     // Check for "RefD = [+1 retained object];".
 
@@ -219,11 +226,56 @@ private:
     return false;
   }
 
+  Stmt *getNextStmt(Expr *E) {
+    if (!E)
+      return 0;
+
+    Stmt *OuterS = E, *InnerS;
+    do {
+      InnerS = OuterS;
+      OuterS = StmtMap->getParent(InnerS);
+    }
+    while (OuterS && (isa<ParenExpr>(OuterS) ||
+                      isa<CastExpr>(OuterS) ||
+                      isa<ExprWithCleanups>(OuterS)));
+    
+    if (!OuterS)
+      return 0;
+
+    Stmt::child_iterator currChildS = OuterS->child_begin();
+    Stmt::child_iterator childE = OuterS->child_end();
+    for (; currChildS != childE; ++currChildS) {
+      if (*currChildS == InnerS)
+        break;
+    }
+    if (currChildS == childE)
+      return 0;
+    ++currChildS;
+    if (currChildS == childE)
+      return 0;
+
+    Stmt *nextStmt = *currChildS;
+    if (!nextStmt)
+      return 0;
+    return nextStmt->IgnoreImplicit();
+  }
+
   Decl *getReferencedDecl(Expr *E) {
     if (!E)
       return 0;
 
     E = E->IgnoreParenCasts();
+    if (ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(E)) {
+      switch (ME->getMethodFamily()) {
+      case OMF_copy:
+      case OMF_autorelease:
+      case OMF_release:
+      case OMF_retain:
+        return getReferencedDecl(ME->getInstanceReceiver());
+      default:
+        return 0;
+      }
+    }
     if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
       return DRE->getDecl();
     if (MemberExpr *ME = dyn_cast<MemberExpr>(E))

clang/test/ARCMT/autoreleases.m

@@ -64,3 +64,8 @@ void test(A *prevVal, A *newVal) {
   [prevVal autorelease];
   prevVal = [newVal retain];
 }
+
+id test2(A* val) {
+  [[val retain] autorelease];
+  return val;
+}

clang/test/ARCMT/autoreleases.m.result

@@ -60,3 +60,7 @@ int main (int argc, const char * argv[]) {
 void test(A *prevVal, A *newVal) {
   prevVal = newVal;
 }
+
+id test2(A* val) {
+  return val;
+}