[Bug tree-optimization/71144] New: [6/7 Regression] isl_aff.c:1001: position out of bounds

[ktkachov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71144

            Bug ID: 71144
           Summary: [6/7 Regression] isl_aff.c:1001: position out of
                    bounds
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ktkachov at gcc dot gnu.org
  Target Milestone: ---

The testcase:
int a, c, d, e, f;
int b[1];
short g;

void
fn1 ()
{
  for (; a; a++)
    if (f)
      for (; e; e--)
        {
          d = 0;
          for (; d <= 0; d++)
            if (c)
              break;
          (g = a) || (b[a] = 0);
        }
}


ICEs with -Ofast -floop-interchange:
../../gcc/isl/isl_aff.c:1001: position out of bounds
mycrash.c: In function ‘fn1’:
mycrash.c:6:1: internal compiler error: Aborted
 fn1 ()
 ^~~
0xbab71f crash_signal
        ../../gcc/gcc/toplev.c:333
0x13a4fe2 isl_handle_error
        ../../gcc/isl/isl_ctx.c:96
0x1365fa1 isl_aff_set_coefficient_si
        ../../gcc/isl/isl_aff.c:1000
0x12342da extract_affine_chrec
        ../../gcc/gcc/graphite-sese-to-poly.c:239
0x12342da extract_affine
        ../../gcc/gcc/graphite-sese-to-poly.c:381
0x123418e extract_affine
        ../../gcc/gcc/graphite-sese-to-poly.c:421
0x123523d add_condition_to_pbb
        ../../gcc/gcc/graphite-sese-to-poly.c:458
0x123523d add_conditions_to_domain
        ../../gcc/gcc/graphite-sese-to-poly.c:525
0x123523d build_iteration_domains
        ../../gcc/gcc/graphite-sese-to-poly.c:1017
0x1234fe5 build_iteration_domains
        ../../gcc/gcc/graphite-sese-to-poly.c:1040
0x123579f build_poly_scop(scop*)
        ../../gcc/gcc/graphite-sese-to-poly.c:1364
0x121fb9a graphite_transform_loops()
        ../../gcc/gcc/graphite.c:319
0x12201a0 graphite_transforms
        ../../gcc/gcc/graphite.c:356
0x12201a0 execute
        ../../gcc/gcc/graphite.c:433
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.

This is using ISL 0.15 as downloaded from contrib/download_prerequisites.
Don't know if this is an ISL bug or a bug in the way GCC communicates with it.