[Bug target/83985] New: Compile time hog for 32-bit BE powerpc targets

["asolokha at gmx dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83985

            Bug ID: 83985
           Summary: Compile time hog for 32-bit BE powerpc targets
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: compile-time-hog
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---
            Target: powerpc-*-linux-gnu

gcc-8.0.0-alpha20180121 snapshot (r256935) takes indefinite time to compile the
following snippet w/ -O2 (-O3, -Ofast):

long long int fb;

void
jm (int nu)
{
  if (nu == 0)
    return;

  while (fb < 2)
    {
      signed char *ug;

      fb /= nu;
      ug = (fb == 0) ? (signed char *)&nu : (signed char *)&fb;
      ++*ug;

      ++fb;
    }

  for (;;)
    {
    }
}

% timeout 5 powerpc-e300c3-linux-gnu-gcc-8.0.0-alpha20180121 -O2 -c mxuzqgpa.c
zsh: exit 124   timeout 5 powerpc-e300c3-linux-gnu-gcc-8.0.0-alpha20180121 -O2
-c mxuzqgpa.c

Top 10 entries captured by perf top:

  10.31%  cc1  [.] volatile_refs_p
   7.31%  cc1  [.] fast_dce
   6.78%  cc1  [.] df_worklist_dataflow
   6.01%  cc1  [.] deletable_insn_p
   5.61%  cc1  [.] bitmap_clear_bit
   5.37%  cc1  [.] bitmap_set_bit
   3.81%  cc1  [.] df_simulate_defs
   3.53%  cc1  [.] find_reg_note
   3.47%  cc1  [.] bitmap_ior_into
   3.41%  cc1  [.] prescan_insns_for_dce
   3.33%  cc1  [.] delete_unmarked_insns
   2.75%  cc1  [.] df_simulate_uses
   2.39%  cc1  [.] noop_move_p
   2.39%  cc1  [.] note_stores
   2.27%  cc1  [.] mark_insn
   2.06%  cc1  [.] bitmap_bit_p
   2.05%  cc1  [.] set_noop_p
   1.90%  cc1  [.] bitmap_copy
   1.60%  cc1  [.] get_eh_region_and_lp_from_rtx
   1.54%  cc1  [.] df_lr_confluence_n