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From: "luoxhu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/106126] [12 Regression] tree check fail in
 useless_type_conversion_p, at gimple-expr.cc:87 since
 r13-1184-g57424087e82db140
Date: Thu, 30 Jun 2022 03:34:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106126

--- Comment #13 from luoxhu at gcc dot gnu.org ---
Otherwise we need record first_bb when conditions_in_bbs->is_empty, then ch=
eck
that in is_beneficial, ordered_remove the info entry if that bb is not the
first "if condition" with side_effect statement in it, the fix would be as
below, but I am not sure whether it is worth&correct way doing this to hand=
le
both PR105740 and PR106126?


git diff
diff --git a/gcc/gimple-if-to-switch.cc b/gcc/gimple-if-to-switch.cc
index f7b0b02628b..44bb0228856 100644
--- a/gcc/gimple-if-to-switch.cc
+++ b/gcc/gimple-if-to-switch.cc
@@ -63,7 +63,7 @@ struct condition_info

   condition_info (gcond *cond): m_cond (cond), m_bb (gimple_bb (cond)),
     m_forwarder_bb (NULL), m_ranges (), m_true_edge (NULL), m_false_edge
(NULL),
-    m_true_edge_phi_mapping (), m_false_edge_phi_mapping ()
+    m_true_edge_phi_mapping (), m_false_edge_phi_mapping (), first_bb(fals=
e)
   {
     m_ranges.create (0);
   }
@@ -80,6 +80,7 @@ struct condition_info
   edge m_false_edge;
   mapping_vec m_true_edge_phi_mapping;
   mapping_vec m_false_edge_phi_mapping;
+  bool first_bb;
 };

 /* Recond PHI mapping for an original edge E and save these into vector VE=
C.=20
*/
@@ -194,6 +195,16 @@ if_chain::is_beneficial ()
   auto_vec<cluster *> clusters;
   clusters.create (m_entries.length ());

+  for (unsigned i =3D 0; i < m_entries.length (); i++)
+    {
+      condition_info *info =3D m_entries[i];
+      if (info->first_bb && i !=3D 0 && !no_side_effect_bb (info->m_bb))
+       {
+         m_entries.ordered_remove (i);
+         break;
+       }
+    }
+
   for (unsigned i =3D 0; i < m_entries.length (); i++)
     {
       condition_info *info =3D m_entries[i];
@@ -397,6 +408,8 @@ find_conditions (basic_block bb,
   tree_code code =3D gimple_cond_code (cond);

   condition_info *info =3D new condition_info (cond);
+  if (conditions_in_bbs->is_empty ())
+    info->first_bb =3D true;=