This backport contains 1 patch from gcc main stream tree.
The commit id of these patchs list as following in the order of time.

a0aeb7fb93da156b64fd08391c79ff35a69af7ba
0001-tree-vect-stmts.c-vectorizable_comparison-Swap-opera.patch

diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
index e921225b5ec..601a6f55fbf 100644
--- a/gcc/tree-vect-stmts.c
+++ b/gcc/tree-vect-stmts.c
@@ -10369,7 +10369,7 @@ vectorizable_comparison (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 
       if (!slp_node)
 	{
-	  if (swap_p)
+	  if (swap_p && j == 0)
 	    std::swap (vec_rhs1, vec_rhs2);
 	  vec_oprnds0.quick_push (vec_rhs1);
 	  vec_oprnds1.quick_push (vec_rhs2);