[Bug tree-optimization/82591] New: [8 Regression] [graphite] Compile-time hog w/ -O2 -floop-nest-optimize

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82591

            Bug ID: 82591
           Summary: [8 Regression] [graphite] Compile-time hog w/ -O2
                    -floop-nest-optimize
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: compile-time-hog
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

gcc-8.0.0-alpha20171015 snapshot (r253772) takes about 25 s to compile the
following snippet w/ -O2 -floop-nest-optimize on my machine:

unsigned int dd;

unsigned int
hi (unsigned int s1, int w0, int ym, unsigned short int oy)
{
  int *v1;

  if (w0 == 0)
    v1 = &w0;
  else
    {
      int *fr;

      v1 = &ym;

      for (w0 = 0; w0 < 128; ++w0)
        {
          int r8;

          for (r8 = 0; r8 < 3; ++r8)
            {
              fr = (int *)&dd;
              oy -= 0x201;
              s1 = oy <= 1;
              ym += dd;
              if (s1 != 0)
                {
                  int x8;

                  *fr = 0;
                  x8 = ym / *fr;
                }
            }
        }
    }

  if (s1 == (((*v1 != 0) ? s1 : 0) - (1 / 0)))
    s1 = 0;

  return s1;
}

% time gcc-8.0.0-alpha20171015 -O2 -floop-nest-optimize -w -c yaqk7feq.c
gcc-8.0.0-alpha20171015 -O2 -floop-nest-optimize -w -c yaqk7feq.c  21.80s user
0.02s system 92% cpu 23.709 total

On this machine I have gmp 6.1.2 and isl 0.18 installed.

9.37%  libgmp.so.10.3.2  [.] __gmpz_divexact
9.16%  libgmp.so.10.3.2  [.] __gmpz_mul
8.06%  libisl.so.15.3.0  [.] isl_tab_pivot
7.62%  libgmp.so.10.3.2  [.] __gmpz_aorsmul_1
7.59%  libgmp.so.10.3.2  [.] __gmpn_gcd_1
5.28%  libgmp.so.10.3.2  [.] __gmpn_modexact_1_odd
5.17%  libgmp.so.10.3.2  [.] __gmpn_divexact_1
4.51%  libgmp.so.10.3.2  [.] __gmpz_cmpabs
4.27%  libgmp.so.10.3.2  [.] __gmpn_mul_1
4.26%  libgmp.so.10.3.2  [.] __gmpz_gcd
2.75%  libgmp.so.10.3.2  [.] __gmpn_divexact
2.66%  libisl.so.15.3.0  [.] isl_seq_gcd
2.53%  libisl.so.15.3.0  [.] isl_seq_abs_min_non_zero
2.05%  libgmp.so.10.3.2  [.] __gmpz_cmp_ui
1.91%  libgmp.so.10.3.2  [.] __gmpz_addmul
1.31%  libgmp.so.10.3.2  [.] __gmpn_gcd
1.25%  libgmp.so.10.3.2  [.] __gmpn_copyi
1.04%  libisl.so.15.3.0  [.] isl_seq_scale_down
0.91%  libgmp.so.10.3.2  [.] __gmpn_submul_1
0.77%  libisl.so.15.3.0  [.] isl_tab_var_from_row
0.69%  libgmp.so.10.3.2  [.] __gmpz_set
0.64%  libisl.so.15.3.0  [.] isl_tab_row_is_redundant
0.50%  libgmp.so.10.3.2  [.] 0x000000000005a3fd
0.42%  libgmp.so.10.3.2  [.] __gmpn_addmul_1
0.39%  libgmp.so.10.3.2  [.] 0x000000000005a3f0
0.38%  libgmp.so.10.3.2  [.] 0x000000000005a5e3
0.35%  libgmp.so.10.3.2  [.] __gmpn_divexact@plt
0.35%  libgmp.so.10.3.2  [.] __gmpn_rshift
0.32%  libgmp.so.10.3.2  [.] 0x000000000005a254
0.32%  libc-2.25.so      [.] _int_malloc
0.31%  libisl.so.15.3.0  [.] isl_seq_normalize
0.30%  libisl.so.15.3.0  [.] isl_seq_combine