diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index ccdf14a..ace9ef9 100644
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -965,6 +965,13 @@ propagate_necessity (struct edge_list *el)
                    mark_aliased_reaching_defs_necessary (stmt, op);
                }
            }
+         else if (gimple_code (stmt) == GIMPLE_TRANSACTION)
+           {
+             /* The beginning of a transaction is a memory barrier.  */
+             /* ??? If we were really cool, we'd only be a barrier
+                for the memories touched within the transaction.  */
+             mark_all_reaching_defs_necessary (stmt);
+           }
          else
            gcc_unreachable ();