Move copy_phi_arg_into_existing_phi to common location and use it

While improving replace_phi_edge_with_variable for the diamond formed bb
case, I need a way to copy phi entries from one edge to another as I am
removing a forwarding bb inbetween. I was pointed out that jump threading
code had copy_phi_arg_into_existing_phi which I can use.
I also noticed that both gimple_duplicate_sese_tail and
remove_forwarder_block have similar code so it makes sense to use that function
in those two locations too.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

gcc/ChangeLog:

	* tree-ssa-threadupdate.cc (copy_phi_arg_into_existing_phi): Move to ...
	* tree-cfg.cc (copy_phi_arg_into_existing_phi): Here and remove static.
	(gimple_duplicate_sese_tail): Use copy_phi_arg_into_existing_phi instead
	of an inline version of it.
	* tree-cfgcleanup.cc (remove_forwarder_block): Likewise.
	* tree-cfg.h (copy_phi_arg_into_existing_phi): New declaration.

1 files changed, 27 insertions, 11 deletions

diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index 21cf6fc..0aeebb6 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;