[gcc/devel/gccgo] preserve EDGE_DFS_BACK across split_edge

[Ian Lance Taylor]

https://gcc.gnu.org/g:5e3c2d4b238f10e6e6db36810469483334d4bcb0

commit 5e3c2d4b238f10e6e6db36810469483334d4bcb0
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Jan 14 14:14:54 2020 +0100

    preserve EDGE_DFS_BACK across split_edge
    
    This moves EDGE_DFS_BACK to the appropriate edge when the split
    edge had it set.
    
    2020-05-12  Richard Biener  <rguenther@suse.de>
    
            * cfghooks.c (split_edge): Preserve EDGE_DFS_BACK if set.

Diff:
---
 gcc/ChangeLog  | 4 ++++
 gcc/cfghooks.c | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 72b56ad6f2e..b0a9212688a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2020-05-12  Richard Biener  <rguenther@suse.de>
+
+	* cfghooks.c (split_edge): Preserve EDGE_DFS_BACK if set.
+
 2020-05-12  Martin Liska  <mliska@suse.cz>
 
 	PR sanitizer/95033
diff --git a/gcc/cfghooks.c b/gcc/cfghooks.c
index ea558b46947..71c6b63ad3b 100644
--- a/gcc/cfghooks.c
+++ b/gcc/cfghooks.c
@@ -640,6 +640,7 @@ split_edge (edge e)
   profile_count count = e->count ();
   edge f;
   bool irr = (e->flags & EDGE_IRREDUCIBLE_LOOP) != 0;
+  bool back = (e->flags & EDGE_DFS_BACK) != 0;
   class loop *loop;
   basic_block src = e->src, dest = e->dest;
 
@@ -659,6 +660,11 @@ split_edge (edge e)
       single_pred_edge (ret)->flags |= EDGE_IRREDUCIBLE_LOOP;
       single_succ_edge (ret)->flags |= EDGE_IRREDUCIBLE_LOOP;
     }
+  if (back)
+    {
+      single_pred_edge (ret)->flags &= ~EDGE_DFS_BACK;
+      single_succ_edge (ret)->flags |= EDGE_DFS_BACK;
+    }
 
   if (dom_info_available_p (CDI_DOMINATORS))
     set_immediate_dominator (CDI_DOMINATORS, ret, single_pred (ret));