[Bug tree-optimization/80906] New: [7/8 Regression] ICE in copy_loop_close_phi_args, at graphite-isl-ast-to-gimple.c:2094

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80906

            Bug ID: 80906
           Summary: [7/8 Regression] ICE in copy_loop_close_phi_args, at
                    graphite-isl-ast-to-gimple.c:2094
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          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-alpha20170521 snapshot, as well as gcc 7.1, ICEs when compiling the
following snippet w/ -O2 (-O3, -Ofast) -floop-nest-optimize:

int qc;

int
ec (int lh[][2])
{
  const int jv = 3;
  int zf, hp, c5 = 0, m3 = 1;

  for (zf = 0; zf < jv; ++zf)
    for (hp = 0; hp < jv; ++hp)
      {
        short int bm = 0;

        for (qc = 0; qc < jv; ++qc)
          --bm;
        if (bm != 0)
          --c5;
        lh[0][0] = 0;
        m3 *= jv;
      }

  return c5 + m3;
}

% x86_64-unknown-linux-gnu-gcc-8.0.0-alpha20170521 -O2 -floop-nest-optimize -c
bnjajc7i.c
bnjajc7i.c: In function 'ec':
bnjajc7i.c:4:1: internal compiler error: in copy_loop_close_phi_args, at
graphite-isl-ast-to-gimple.c:2094
 ec (int lh[][2])
 ^~

Earlier I posted another testcase which I believe reproduces the same issue in
PR70390 comment 10. So, the current PR may well be a duplicate of PR70390,
though the testcase filed above compiles well by gcc 6.3.