[gcc r14-145] Fix latent bug in loop header copying which forgets to update the loop header pointer

[gcc r14-145] Fix latent bug in loop header copying which forgets to update the loop header pointer

[Jan Hubicka]

https://gcc.gnu.org/g:2f4e45101dd812a6fcc1e5d96efedc60b8735432

commit r14-145-g2f4e45101dd812a6fcc1e5d96efedc60b8735432
Author: Jan Hubicka <jh@suse.cz>
Date:   Fri Apr 21 15:53:21 2023 +0200

    Fix latent bug in loop header copying which forgets to update the loop header pointer
    
    gcc/ChangeLog:
    
    2023-04-21  Jan Hubicka  <hubicka@ucw.cz>
                Ondrej Kubanek  <kubanek0ondrej@gmail.com>
    
            * tree-ssa-loop-ch.cc (ch_base::copy_headers): Update loop header and
            latch.

Diff:
---
 gcc/tree-ssa-loop-ch.cc | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/gcc/tree-ssa-loop-ch.cc b/gcc/tree-ssa-loop-ch.cc
index ddf025c0cfd..560df39893e 100644
--- a/gcc/tree-ssa-loop-ch.cc
+++ b/gcc/tree-ssa-loop-ch.cc
@@ -542,6 +542,17 @@ ch_base::copy_headers (function *fun)
 	    }
 	}
 
+      /* Update header of the loop.  */
+      loop->header = header;
+      /* Find correct latch.  We only duplicate chain of conditionals so
+	 there should be precisely two edges to the new header.  One entry
+	 edge and one to latch.  */
+      FOR_EACH_EDGE (e, ei, loop->header->preds)
+	if (header != e->src)
+	  {
+	    loop->latch = e->src;
+	    break;
+	  }
       /* Ensure that the latch and the preheader is simple (we know that they
 	 are not now, since there was the loop exit condition.  */
       split_edge (loop_preheader_edge (loop));
@@ -561,6 +572,8 @@ ch_base::copy_headers (function *fun)
 
   if (changed)
     {
+      if (flag_checking)
+	verify_loop_structure ();
       update_ssa (TODO_update_ssa);
       /* After updating SSA form perform CSE on the loop header
 	 copies.  This is esp. required for the pass before