[Bug tree-optimization/54146] Very slow compile with attribute((flatten))

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54146

--- Comment #22 from Steven Bosscher <steven at gcc dot gnu.org> 2012-08-06 
19:36:35 UTC ---
IRA/reload spends a rather significant amount of time here:

  FOR_EACH_BB_REVERSE (bb)
    { 
      bitmap_iterator bi;
      rtx insn;

      CLEAR_REG_SET (live_relevant_regs);
-->   memset (live_subregs_used, 0, max_regno * sizeof (int));

This is running with max_regno=O(1e6) and n_basic_blocks=O(1e5) ...