diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index 4927fc0a8d9..a94dc3c2eea 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -6802,6 +6802,32 @@ bb_part_of_region_p (basic_block bb, basic_block* bbs, unsigned n_region)
   return false;
 }
 
+
+/* For each PHI in BB, copy the argument associated with SRC_E to TGT_E.
+   Assuming the argument exists, just does not have a value.  */
+
+void
+copy_phi_arg_into_existing_phi (edge src_e, edge tgt_e)
+{
+  int src_idx = src_e->dest_idx;
+  int tgt_idx = tgt_e->dest_idx;
+
+  /* Iterate over each PHI in e->dest.  */
+  for (gphi_iterator gsi = gsi_start_phis (src_e->dest),
+			   gsi2 = gsi_start_phis (tgt_e->dest);
+       !gsi_end_p (gsi);
+       gsi_next (&gsi), gsi_next (&gsi2))
+    {
+      gphi *src_phi = gsi.phi ();
+      gphi *dest_phi = gsi2.phi ();
+      tree val = gimple_phi_arg_def (src_phi, src_idx);
+      location_t locus = gimple_phi_arg_location (src_phi, src_idx);
+
+      SET_PHI_ARG_DEF (dest_phi, tgt_idx, val);
+      gimple_phi_arg_set_location (dest_phi, tgt_idx, locus);
+    }
+}
+
 /* Duplicates REGION consisting of N_REGION blocks.  The new blocks
    are stored to REGION_COPY in the same order in that they appear
    in REGION, if REGION_COPY is not NULL.  ENTRY is the entry to
@@ -6847,9 +6873,6 @@ gimple_duplicate_sese_tail (edge entry, edge exit,
   gimple_stmt_iterator gsi;
   edge sorig, snew;
   basic_block exit_bb;
-  gphi_iterator psi;
-  gphi *phi;
-  tree def;
   class loop *target, *aloop, *cloop;
 
   gcc_assert (EDGE_COUNT (exit->src->succs) == 2);
@@ -6947,14 +6970,7 @@ gimple_duplicate_sese_tail (edge entry, edge exit,
 	gcc_assert (single_succ_edge (region_copy[i]));
 	e = redirect_edge_and_branch (single_succ_edge (region_copy[i]), exit_bb);
 	PENDING_STMT (e) = NULL;
-	for (psi = gsi_start_phis (exit_bb);
-	     !gsi_end_p (psi);
-	     gsi_next (&psi))
-	  {
-	    phi = psi.phi ();
-	    def = PHI_ARG_DEF (phi, nexits[0]->dest_idx);
-	    add_phi_arg (phi, def, e, gimple_phi_arg_location_from_edge (phi, e));
-	  }
+	copy_phi_arg_into_existing_phi (nexits[0], e);
       }
   e = redirect_edge_and_branch (nexits[1], nexits[0]->dest);
   PENDING_STMT (e) = NULL;
diff --git a/gcc/tree-cfg.h b/gcc/tree-cfg.h
index 9b56a68fe9d..9a1605be305 100644
--- a/gcc/tree-cfg.h
+++ b/gcc/tree-cfg.h
@@ -113,6 +113,7 @@ extern basic_block gimple_switch_default_bb (function *, gswitch *);
 extern edge gimple_switch_edge (function *, gswitch *, unsigned);
 extern edge gimple_switch_default_edge (function *, gswitch *);
 extern bool cond_only_block_p (basic_block);
+extern void copy_phi_arg_into_existing_phi (edge, edge);
 
 /* Return true if the LHS of a call should be removed.  */
 
diff --git a/gcc/tree-cfgcleanup.cc b/gcc/tree-cfgcleanup.cc
index 42b25312122..193d87e3278 100644
--- a/gcc/tree-cfgcleanup.cc
+++ b/gcc/tree-cfgcleanup.cc
@@ -610,17 +610,9 @@ remove_forwarder_block (basic_block bb)
 
       if (s == e)
 	{
-	  /* Create arguments for the phi nodes, since the edge was not
+	  /* Copy arguments for the phi nodes, since the edge was not
 	     here before.  */
-	  for (gphi_iterator psi = gsi_start_phis (dest);
-	       !gsi_end_p (psi);
-	       gsi_next (&psi))
-	    {
-	      gphi *phi = psi.phi ();
-	      location_t l = gimple_phi_arg_location_from_edge (phi, succ);
-	      tree def = gimple_phi_arg_def (phi, succ->dest_idx);
-	      add_phi_arg (phi, unshare_expr (def), s, l);
-	    }
+	  copy_phi_arg_into_existing_phi (succ, s);
 	}
     }
 
diff --git a/gcc/tree-ssa-threadupdate.cc b/gcc/tree-ssa-threadupdate.cc
index 33a91063638..d5416b21a78 100644
--- a/gcc/tree-ssa-threadupdate.cc
+++ b/gcc/tree-ssa-threadupdate.cc
@@ -511,31 +511,6 @@ fwd_jt_path_registry::lookup_redirection_data (edge e, insert_option insert)
     }
 }
 
-/* Similar to copy_phi_args, except that the PHI arg exists, it just
-   does not have a value associated with it.  */
-
-static void
-copy_phi_arg_into_existing_phi (edge src_e, edge tgt_e)
-{
-  int src_idx = src_e->dest_idx;
-  int tgt_idx = tgt_e->dest_idx;
-
-  /* Iterate over each PHI in e->dest.  */
-  for (gphi_iterator gsi = gsi_start_phis (src_e->dest),
-			   gsi2 = gsi_start_phis (tgt_e->dest);
-       !gsi_end_p (gsi);
-       gsi_next (&gsi), gsi_next (&gsi2))
-    {
-      gphi *src_phi = gsi.phi ();
-      gphi *dest_phi = gsi2.phi ();
-      tree val = gimple_phi_arg_def (src_phi, src_idx);
-      location_t locus = gimple_phi_arg_location (src_phi, src_idx);
-
-      SET_PHI_ARG_DEF (dest_phi, tgt_idx, val);
-      gimple_phi_arg_set_location (dest_phi, tgt_idx, locus);
-    }
-}
-
 /* Given ssa_name DEF, backtrack jump threading PATH from node IDX
    to see if it has constant value in a flow sensitive manner.  Set
    LOCUS to location of the constant phi arg and return the value.
