Don't use native atomics on ivars whose size is not a power of two,

even on architectures that support unaligned access (which is the
only way this is otherwise legal, given that ivars apparently do
not honor alignment attributes).

llvm-svn: 139590

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index ca04a7b1785..ddf6e1f98a7 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -527,6 +527,14 @@ PropertyImplStrategy::PropertyImplStrategy(CodeGenModule &CGM,
 
   // Otherwise, this is target-dependent and based on the size and
   // alignment of the ivar.
+
+  // If the size of the ivar is not a power of two, give up.  We don't
+  // want to get into the business of doing compare-and-swaps.
+  if (!IvarSize.isPowerOfTwo()) {
+    Kind = CopyStruct;
+    return;
+  }
+
   llvm::Triple::ArchType arch =
     CGM.getContext().getTargetInfo().getTriple().getArch();