From b7b89b5ebc7c9c74e071607cc2952d6096ac1b03 Mon Sep 17 00:00:00 2001
From: Argyrios Kyrtzidis <akyrtzi@gmail.com>
Date: Fri, 4 Jan 2013 18:29:59 +0000
Subject: [PATCH] [arcmt] Don't error if an autoreleased variable is returned
 after the -autorelease.

rdar://12952025

llvm-svn: 171482
---
 .../ARCMigrate/TransRetainReleaseDealloc.cpp  | 88 +++++++++++++++----
 clang/test/ARCMT/autoreleases.m               |  5 ++
 clang/test/ARCMT/autoreleases.m.result        |  4 +
 3 files changed, 79 insertions(+), 18 deletions(-)

diff --git a/clang/lib/ARCMigrate/TransRetainReleaseDealloc.cpp b/clang/lib/ARCMigrate/TransRetainReleaseDealloc.cpp
index aa7e25b39abf..97d9bffda274 100644
--- a/clang/lib/ARCMigrate/TransRetainReleaseDealloc.cpp
+++ b/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;
@@ -177,6 +190,46 @@ private:
     if (!RefD)
       return false;
 
+    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;
+
+    // Check for "RefD = [+1 retained object];".
+
+    if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(nextStmt)) {
+      if (RefD != getReferencedDecl(Bop->getLHS()))
+        return false;
+      if (isPlusOneAssign(Bop))
+        return true;
+    }
+    return false;
+  }
+
+  Stmt *getNextStmt(Expr *E) {
+    if (!E)
+      return 0;
+
     Stmt *OuterS = E, *InnerS;
     do {
       InnerS = OuterS;
@@ -187,9 +240,7 @@ private:
                       isa<ExprWithCleanups>(OuterS)));
     
     if (!OuterS)
-      return false;
-
-    // Find next statement after the -autorelease.
+      return 0;
 
     Stmt::child_iterator currChildS = OuterS->child_begin();
     Stmt::child_iterator childE = OuterS->child_end();
@@ -198,25 +249,15 @@ private:
         break;
     }
     if (currChildS == childE)
-      return false;
+      return 0;
     ++currChildS;
     if (currChildS == childE)
-      return false;
+      return 0;
 
     Stmt *nextStmt = *currChildS;
     if (!nextStmt)
-      return false;
-    nextStmt = nextStmt->IgnoreImplicit();
-
-    // Check for "RefD = [+1 retained object];".
-    
-    if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(nextStmt)) {
-      if (RefD != getReferencedDecl(Bop->getLHS()))
-        return false;
-      if (isPlusOneAssign(Bop))
-        return true;
-    }
-    return false;
+      return 0;
+    return nextStmt->IgnoreImplicit();
   }
 
   Decl *getReferencedDecl(Expr *E) {
@@ -224,6 +265,17 @@ private:
       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))
diff --git a/clang/test/ARCMT/autoreleases.m b/clang/test/ARCMT/autoreleases.m
index a131bc53391d..d4913943b1cc 100644
--- a/clang/test/ARCMT/autoreleases.m
+++ b/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;
+}
diff --git a/clang/test/ARCMT/autoreleases.m.result b/clang/test/ARCMT/autoreleases.m.result
index 6593fc9199a0..76ce8cfb5107 100644
--- a/clang/test/ARCMT/autoreleases.m.result
+++ b/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;
+}