[Bug tree-optimization/109154] [13 regression] jump threading de-optimizes nested floating point comparisons

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109154

--- 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 != -1 && max_ind +1 != (int) args_len)
+  if (max_ind != -1 && max_ind + 1 != (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 = TREE_TYPE (gimple_phi_result (phi));
       tree lhs;
-      arg1 = args[1];
-      for (i = 0; i < args_len; i++)
+      arg1 = args[args_len - 1];
+      for (i = args_len - 1; i > 0; i--)
        {
-         arg0 = args[i];
-         indexes = phi_arg_map.get (args[i]);
-         if (i != args_len - 1)
+         arg0 = args[i - 1];
+         indexes = phi_arg_map.get (args[i - 1]);
+         if (i != 1)
            lhs = make_temp_ssa_name (type, NULL, "_ifc_");
          else
            lhs = res;