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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109154] [13 regression] jump threading
 de-optimizes nested floating point comparisons
Date: Fri, 14 Apr 2023 19:09:56 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: missed-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109154

--- Comment #51 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Dumb untested patch which saves 2 instructions from each of those testcases:

--- gcc/tree-if-conv.cc.jj      2023-04-12 08:53:58.264496474 +0200
+++ gcc/tree-if-conv.cc 2023-04-14 21:02:42.403826690 +0200
@@ -2071,7 +2071,7 @@ predicate_scalar_phi (gphi *phi, gimple_
     }

   /* Put element with max number of occurences to the end of ARGS.  */
-  if (max_ind !=3D -1 && max_ind +1 !=3D (int) args_len)
+  if (max_ind !=3D -1 && max_ind + 1 !=3D (int) args_len)
     std::swap (args[args_len - 1], args[max_ind]);

   /* Handle one special case when number of arguments with different values
@@ -2116,12 +2116,12 @@ predicate_scalar_phi (gphi *phi, gimple_
       vec<int> *indexes;
       tree type =3D TREE_TYPE (gimple_phi_result (phi));
       tree lhs;
-      arg1 =3D args[1];
-      for (i =3D 0; i < args_len; i++)
+      arg1 =3D args[args_len - 1];
+      for (i =3D args_len - 1; i > 0; i--)
        {
-         arg0 =3D args[i];
-         indexes =3D phi_arg_map.get (args[i]);
-         if (i !=3D args_len - 1)
+         arg0 =3D args[i - 1];
+         indexes =3D phi_arg_map.get (args[i - 1]);
+         if (i !=3D 1)
            lhs =3D make_temp_ssa_name (type, NULL, "_ifc_");
          else
            lhs =3D res;=