[Bug target/99083] Big run-time regressions of 519.lbm_r with LTO

[ubizjak at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99083

--- Comment #5 from Uroš Bizjak <ubizjak at gmail dot com> ---
Martin, can you please benchmark the patch from Comment #4?

The patch is not totally trivial, because it introduces HONOR_REG_ALLOC_ORDER
to x86 and this define disables some other code in ira-color.c,
assign_hard_reg:

      if (!HONOR_REG_ALLOC_ORDER)
        {
          if ((saved_nregs = calculate_saved_nregs (hard_regno, mode)) != 0)
          /* We need to save/restore the hard register in
             epilogue/prologue.  Therefore we increase the cost.  */
          {
            rclass = REGNO_REG_CLASS (hard_regno);
            add_cost = ((ira_memory_move_cost[mode][rclass][0]
                         + ira_memory_move_cost[mode][rclass][1])
                        * saved_nregs / hard_regno_nregs (hard_regno,
                                                          mode) - 1);
            cost += add_cost;
            full_cost += add_cost;
          }
        }