[Bug tree-optimization/68654] [6 Regression] CoreMark Pro performance degradation

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68654

--- Comment #16 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 37474
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37474&action=edit
patch for SSA name management

This patch changes SSA name freelist management to keep the freelist sorted
and at flush_ssaname_freelist shrink num_ssa_names as much as possible.

The goal is to make used SSA names as dense as possible.

Does this patch fix the Coremark regression by chance?  (I'll note that a
proper fix would change the important coalesce cost so it is carried out
regardless of SSA name order).