Fix PR94443 with gsi_insert_seq_before [PR94443]

This patch is to fix the stupid mistake by using
gsi_insert_seq_before instead of gsi_insert_before.

BTW, the regression testing on one x86_64 machine from CFarm is
unable to reveal it (I guess due to native arch sandybridge?), so I
specified additional option -march=znver2 and verified the coverage.

Bootstrapped/regtested on powerpc64le-linux-gnu (P9) and
x86_64-pc-linux-gnu, also verified the fail cases in related PRs.

2020-04-03  Kewen Lin  <linkw@gcc.gnu.org>

gcc/
    PR tree-optimization/94443
    * tree-vect-loop.c (vectorizable_live_operation): Use
    gsi_insert_seq_before to replace gsi_insert_before.

gcc/testsuite/
    PR tree-optimization/94443
    * gcc.dg/vect/pr94443.c: New test.

gcc/ChangeLog

+2020-04-03  Kewen Lin  <linkw@gcc.gnu.org>
+
+	PR tree-optimization/94443
+	* tree-vect-loop.c (vectorizable_live_operation): Use
+	gsi_insert_seq_before to replace gsi_insert_before.
+
 2020-04-03  Martin Liska  <mliska@suse.cz>
 
 	PR ipa/94445

gcc/testsuite/ChangeLog

+2020-04-03  Kewen Lin  <linkw@gcc.gnu.org>
+
+	PR tree-optimization/94443
+	* gcc.dg/vect/pr94443.c: New test.
+
 2020-04-02  Sandra Loosemore  <sandra@codesourcery.com>
 
 	* lib/target-supports.exp (check_effective_target_sigsetjmp): Test

gcc/testsuite/gcc.dg/vect/pr94443.c

+/* { dg-do compile } */
+/* { dg-additional-options "-march=znver2" { target { x86_64-*-* i?86-*-* } } } */
+
+/* Check it to be compiled successfully without any ICE.  */
+
+int a;
+unsigned *b;
+
+void foo()
+{
+  for (unsigned i; i <= a; ++i, ++b)
+    ;
+}

gcc/tree-vect-loop.c

@@ -8050,7 +8050,7 @@ vectorizable_live_operation (stmt_vec_info stmt_info,
   if (stmts)
     {
       gimple_stmt_iterator exit_gsi = gsi_after_labels (exit_bb);
-      gsi_insert_before (&exit_gsi, stmts, GSI_CONTINUE_LINKING);
+      gsi_insert_seq_before (&exit_gsi, stmts, GSI_SAME_STMT);
 
       /* Remove existing phi from lhs and create one copy from new_tree.  */
       tree lhs_phi = NULL_TREE;
@@ -8063,7 +8063,7 @@ vectorizable_live_operation (stmt_vec_info stmt_info,
 	      remove_phi_node (&gsi, false);
 	      lhs_phi = gimple_phi_result (phi);
 	      gimple *copy = gimple_build_assign (lhs_phi, new_tree);
-	      gsi_insert_after (&exit_gsi, copy, GSI_CONTINUE_LINKING);
+	      gsi_insert_before (&exit_gsi, copy, GSI_SAME_STMT);
 	      break;
 	    }
 	}