[Bug middle-end/105028] [11/12 Regression] gcc.dg/long_branch.c compilation time increases by 10x on BE system after r11-5648

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105028

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
                 CC|                            |vmakarov at gcc dot gnu.org
   Last reconfirmed|                            |2022-03-23
             Status|UNCONFIRMED                 |NEW
           Priority|P3                          |P2

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.

Samples: 42K of event 'cycles', Event count (approx.): 46707220159              
Overhead       Samples  Command  Shared Object     Symbol                       
  48.06%         20480  cc1      cc1               [.] form_threads_from_copies

and all the overhead is in the tail copying:

      /* Collect the rest of copies.  */
      for (n = 0; i < cp_num; i++)
        {
          cp = sorted_copies[i];
          if (ALLOCNO_COLOR_DATA (cp->first)->first_thread_allocno
              != ALLOCNO_COLOR_DATA (cp->second)->first_thread_allocno)
            sorted_copies[n++] = cp;
        }

for the slow case cp_num is 55100.