[Bug middle-end/106870] New: ctrl_altering flag is not set correctly

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106870

            Bug ID: 106870
           Summary: ctrl_altering flag is not set correctly
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

When trying to add the following verification I run into various issues with
the gimple_ctrl_altering_p flag which stmt_ends_bb_p which sets found_ctrl_stmt
ultimatively relies on for the noreturn case.

diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index bbe08357d6e..a939a11d8bb 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -5708,6 +5709,14 @@ gimple_verify_flow_info (void)
            seen_nondebug_stmt = true;
        }

+      if (!found_ctrl_stmt && EDGE_COUNT (bb->succs) != 1)
+       {
+         error ("basic block %d has no control altering stmt but %d "
+                "outgoing edges",
+                bb->index, EDGE_COUNT (bb->succs));
+         err = 1;
+       }
+
       gsi = gsi_last_nondebug_bb (bb);
       if (gsi_end_p (gsi))
        continue;