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

0001-tree-optimization-95717-fix-SSA-update-for-vectorize.patch
d0909f5858ad81e6d8b73fa6193be19cb5e6ed7b

diff -Nurp a/gcc/testsuite/g++.dg/torture/pr95717.C b/gcc/testsuite/g++.dg/torture/pr95717.C
--- a/gcc/testsuite/g++.dg/torture/pr95717.C	1970-01-01 08:00:00.000000000 +0800
+++ b/gcc/testsuite/g++.dg/torture/pr95717.C	2020-08-24 21:45:48.436000000 +0800
@@ -0,0 +1,12 @@
+// { dg-do compile }
+
+bool a;
+extern bool b[];
+long c, d;
+int *f;
+void g(bool h)
+{
+  for (short e = 0; e < c; e = 4)
+    for (; d; d++)
+      b[d] = a = f[d] ? c ? h : 0 : h;
+}
diff -Nurp a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
--- a/gcc/tree-vect-loop-manip.c	2020-08-24 21:45:23.620000000 +0800
+++ b/gcc/tree-vect-loop-manip.c	2020-08-24 21:45:48.436000000 +0800
@@ -1073,6 +1073,10 @@ slpeel_tree_duplicate_loop_to_edge_cfg (
 
   add_phi_args_after_copy (new_bbs, scalar_loop->num_nodes + 1, NULL);
 
+  /* Skip new preheader since it's deleted if copy loop is added at entry.  */
+  for (unsigned i = (at_exit ? 0 : 1); i < scalar_loop->num_nodes + 1; i++)
+    rename_variables_in_bb (new_bbs[i], duplicate_outer_loop);
+
   if (scalar_loop != loop)
     {
       /* If we copied from SCALAR_LOOP rather than LOOP, SSA_NAMEs from
@@ -1150,10 +1154,6 @@ slpeel_tree_duplicate_loop_to_edge_cfg (
 			       loop_preheader_edge (new_loop)->src);
     }
 
-  /* Skip new preheader since it's deleted if copy loop is added at entry.  */
-  for (unsigned i = (at_exit ? 0 : 1); i < scalar_loop->num_nodes + 1; i++)
-    rename_variables_in_bb (new_bbs[i], duplicate_outer_loop);
-
   if (scalar_loop != loop)
     {
       /* Update new_loop->header PHIs, so that on the preheader