Fix noreturn discovery.

Fix ipa-pure-const handling of noreturn flags.  It is not safe to set it for
interposable symbols and we should also set it for aliases (just like we do for
other flags).  This patch merely copies other flag handling and implements it
here.

gcc/ChangeLog:

2021-11-11  Jan Hubicka  <hubicka@ucw.cz>

	* cgraph.c (set_noreturn_flag_1): New function.
	(cgraph_node::set_noreturn_flag): New member function
	* cgraph.h (cgraph_node::set_noreturn_flags): Declare.
	* ipa-pure-const.c (pass_local_pure_const::execute): Use it.

1 files changed, 47 insertions, 0 deletions

diff --git a/gcc/cgraph.c b/gcc/cgraph.c
index c67d300..466b66d 100644
--- a/gcc/cgraph.c
+++ b/gcc/cgraph.c
@@ -2614,6 +2614,53 @@ cgraph_node::set_malloc_flag (bool malloc_p)
   return changed;
 }
 
+/* Worker to set noreturng flag.  */
+static void
+set_noreturn_flag_1 (cgraph_node *node, bool noreturn_p, bool *changed)
+{
+  if (noreturn_p && !TREE_THIS_VOLATILE (node->decl))
+    {
+      TREE_THIS_VOLATILE (node->decl) = true;
+      *changed = true;
+    }
+
+  ipa_ref *ref;
+  FOR_EACH_ALIAS (node, ref)
+    {
+      cgraph_node *alias = dyn_cast<cgraph_node *> (ref->referring);
+      if (!noreturn_p || alias->get_availability () > AVAIL_INTERPOSABLE)
+	set_noreturn_flag_1 (alias, noreturn_p, changed);
+    }
+
+  for (cgraph_edge *e = node->callers; e; e = e->next_caller)
+    if (e->caller->thunk
+	&& (!noreturn_p || e->caller->get_availability () > AVAIL_INTERPOSABLE))
+      set_noreturn_flag_1 (e->caller, noreturn_p, changed);
+}
+
+/* Set TREE_THIS_VOLATILE on NODE's decl and on NODE's aliases if any.  */
+
+bool
+cgraph_node::set_noreturn_flag (bool noreturn_p)
+{
+  bool changed = false;
+
+  if (!noreturn_p || get_availability () > AVAIL_INTERPOSABLE)
+    set_noreturn_flag_1 (this, noreturn_p, &changed);
+  else
+    {
+      ipa_ref *ref;
+
+      FOR_EACH_ALIAS (this, ref)
+	{
+	  cgraph_node *alias = dyn_cast<cgraph_node *> (ref->referring);
+	  if (!noreturn_p || alias->get_availability () > AVAIL_INTERPOSABLE)
+	    set_noreturn_flag_1 (alias, noreturn_p, &changed);
+	}
+    }
+  return changed;
+}
+
 /* Worker to set_const_flag.  */
 
 static void