[PATCH] D38659: [Sema][ObjC] Preserve syntactic sugar when removing ARCReclaimReturnedObject cast

[Akira Hatanaka via Phabricator via cfe-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL315261: [Sema][ObjC] Preserve syntactic sugar when removing (authored by ahatanak).

Changed prior to commit:
  https://reviews.llvm.org/D38659?vs=118121&id=118302#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D38659

Files:
  cfe/trunk/lib/Sema/SemaExprObjC.cpp
  cfe/trunk/test/CodeGenObjC/arc-bridged-cast.m


Index: cfe/trunk/test/CodeGenObjC/arc-bridged-cast.m
===================================================================
--- cfe/trunk/test/CodeGenObjC/arc-bridged-cast.m
+++ cfe/trunk/test/CodeGenObjC/arc-bridged-cast.m
@@ -102,5 +102,6 @@
   // CHECK-NOT: call i8* @objc_retainAutoreleasedReturnValue(
   // CHECK-NOT: call void @objc_release(
   CFStringRef r = (__bridge CFStringRef)(CreateNSString());
+  r = (__bridge CFStringRef)((NSString *)(CreateNSString()));
   return r;
 }
Index: cfe/trunk/lib/Sema/SemaExprObjC.cpp
===================================================================
--- cfe/trunk/lib/Sema/SemaExprObjC.cpp
+++ cfe/trunk/lib/Sema/SemaExprObjC.cpp
@@ -4317,14 +4317,37 @@
 
 /// Look for an ObjCReclaimReturnedObject cast and destroy it.
 static Expr *maybeUndoReclaimObject(Expr *e) {
-  // For now, we just undo operands that are *immediately* reclaim
-  // expressions, which prevents the vast majority of potential
-  // problems here.  To catch them all, we'd need to rebuild arbitrary
-  // value-propagating subexpressions --- we can't reliably rebuild
-  // in-place because of expression sharing.
-  if (auto *ice = dyn_cast<ImplicitCastExpr>(e->IgnoreParens()))
-    if (ice->getCastKind() == CK_ARCReclaimReturnedObject)
-      return ice->getSubExpr();
+  Expr *curExpr = e, *prevExpr = nullptr;
+
+  // Walk down the expression until we hit an implicit cast of kind
+  // ARCReclaimReturnedObject or an Expr that is neither a Paren nor a Cast.
+  while (true) {
+    if (auto *pe = dyn_cast<ParenExpr>(curExpr)) {
+      prevExpr = curExpr;
+      curExpr = pe->getSubExpr();
+      continue;
+    }
+
+    if (auto *ce = dyn_cast<CastExpr>(curExpr)) {
+      if (auto *ice = dyn_cast<ImplicitCastExpr>(ce))
+        if (ice->getCastKind() == CK_ARCReclaimReturnedObject) {
+          if (!prevExpr)
+            return ice->getSubExpr();
+          if (auto *pe = dyn_cast<ParenExpr>(prevExpr))
+            pe->setSubExpr(ice->getSubExpr());
+          else
+            cast<CastExpr>(prevExpr)->setSubExpr(ice->getSubExpr());
+          return e;
+        }
+
+      prevExpr = curExpr;
+      curExpr = ce->getSubExpr();
+      continue;
+    }
+
+    // Break out of the loop if curExpr is neither a Paren nor a Cast.
+    break;
+  }
 
   return e;
 }


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