[Bug target/81348] New: PowerPC64: Code built with -mcpu=power9 hits SEGV in RTL split2

["anton at samba dot org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81348

            Bug ID: 81348
           Summary: PowerPC64: Code built with -mcpu=power9 hits SEGV in
                    RTL split2
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anton at samba dot org
                CC: meissner at gcc dot gnu.org, segher at gcc dot gnu.org,
                    wschmidt at gcc dot gnu.org
  Target Milestone: ---
            Target: powerpc64le-linux

I hit a SEGV with csmith, a cut down test case:

int a;
short b;
float ***c;

void d(void)
{
        int e = 3;

        if (a)
                e = b;

        ***c = e;
}

# gcc -Og -mcpu=power9 crash1b.c

during RTL pass: split2
crash1b.c: In function ‘d’:
crash1b.c:13:1: internal compiler error: Segmentation fault
 }
 ^
0x109452d3 crash_signal
        ../../gcc/gcc/toplev.c:338
0x10440568 df_install_refs
        ../../gcc/gcc/df-scan.c:2379
0x10440707 df_refs_add_to_chains
        ../../gcc/gcc/df-scan.c:2424
0x10448ed3 df_insn_rescan(rtx_insn*)
        ../../gcc/gcc/df-scan.c:1091
0x104d8387 emit_insn_after_1
        ../../gcc/gcc/emit-rtl.c:4492
0x104d8387 emit_pattern_after_noloc
        ../../gcc/gcc/emit-rtl.c:4541
0x104d8603 emit_pattern_after_setloc
        ../../gcc/gcc/emit-rtl.c:4694
0x104d9a77 emit_insn_after_setloc(rtx_def*, rtx_def*, int)
        ../../gcc/gcc/emit-rtl.c:4739
0x104d9a77 try_split(rtx_def*, rtx_insn*, int)
        ../../gcc/gcc/emit-rtl.c:3839
0x10871d97 split_insn
        ../../gcc/gcc/recog.c:2889
0x10878107 split_all_insns()
        ../../gcc/gcc/recog.c:2978
0x10878177 rest_of_handle_split_before_sched2
        ../../gcc/gcc/recog.c:4018
0x10878177 execute
        ../../gcc/gcc/recog.c:4057