Document the existing objc_precise_lifetime attribute.

Introduce and document a new objc_returns_inner_pointer
attribute, and consume it by performing a retain+autorelease
on message receivers when they're not immediately loaded from
an object with precise lifetime.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@135764 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 31 insertions, 0 deletions

diff --git a/lib/Sema/AttributeList.cpp b/lib/Sema/AttributeList.cpp
index 5a8330bbfd..21068538e8 100644
--- a/lib/Sema/AttributeList.cpp
+++ b/lib/Sema/AttributeList.cpp
@@ -163,6 +163,7 @@ AttributeList::Kind AttributeList::getKind(const IdentifierInfo *Name) {
     .Case("vec_type_hint", IgnoredAttribute)
     .Case("objc_exception", AT_objc_exception)
     .Case("objc_method_family", AT_objc_method_family)
+    .Case("objc_returns_inner_pointer", AT_objc_returns_inner_pointer)
     .Case("ext_vector_type", AT_ext_vector_type)
     .Case("neon_vector_type", AT_neon_vector_type)
     .Case("neon_polyvector_type", AT_neon_polyvector_type)
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 61b7b3ee05..ad9b6ddba9 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -2767,6 +2767,33 @@ static void handleNSReturnsRetainedAttr(Sema &S, Decl *D,
   };
 }
 
+static void handleObjCReturnsInnerPointerAttr(Sema &S, Decl *D,
+                                              const AttributeList &attr) {
+  SourceLocation loc = attr.getLoc();
+
+  ObjCMethodDecl *method = dyn_cast<ObjCMethodDecl>(D);
+
+  if (!isa<ObjCMethodDecl>(method)) {
+    S.Diag(method->getLocStart(), diag::err_attribute_wrong_decl_type)
+      << SourceRange(loc, loc) << attr.getName() << 13 /* methods */;
+    return;
+  }
+
+  // Check that the method returns a normal pointer.
+  QualType resultType = method->getResultType();
+  if (!resultType->isPointerType() || resultType->isObjCRetainableType()) {
+    S.Diag(method->getLocStart(), diag::warn_ns_attribute_wrong_return_type)
+      << SourceRange(loc)
+      << attr.getName() << /*method*/ 1 << /*non-retainable pointer*/ 2;
+
+    // Drop the attribute.
+    return;
+  }
+
+  method->addAttr(
+    ::new (S.Context) ObjCReturnsInnerPointerAttr(loc, S.Context));
+}
+
 static void handleObjCOwnershipAttr(Sema &S, Decl *D,
                                     const AttributeList &Attr) {
   if (hasDeclarator(D)) return;
@@ -2969,6 +2996,9 @@ static void ProcessInheritableDeclAttr(Sema &S, Scope *scope, Decl *D,
   case AttributeList::AT_objc_precise_lifetime:
     handleObjCPreciseLifetimeAttr(S, D, Attr); break;
 
+  case AttributeList::AT_objc_returns_inner_pointer:
+    handleObjCReturnsInnerPointerAttr(S, D, Attr); break;
+
   // Checker-specific.
   case AttributeList::AT_cf_consumed:
   case AttributeList::AT_ns_consumed: handleNSConsumedAttr  (S, D, Attr); break;