[Bug rtl-optimization/71295] New: [7 Regression] internal compiler error: in subreg_get_info, at rtlanal.c:3673 on arm

[ktkachov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71295

            Bug ID: 71295
           Summary: [7 Regression] internal compiler error: in
                    subreg_get_info, at rtlanal.c:3673 on arm
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ktkachov at gcc dot gnu.org
  Target Milestone: ---
            Target: arm

extern void fn2 (long long);
int a;

void
fn1 ()
{
  long long b[3];
  a = 0;
  for (; a < 3; a++)
    b[a] = 1;
  fn2 (b[1]);
}

ICEs for me on arm with -O3 -march=armv8-a -mfpu=neon-fp-armv8 -mfloat-abi=hard

mycrash.c: In function 'fn1':
mycrash.c:12:1: internal compiler error: in subreg_get_info, at rtlanal.c:3673
 }
 ^
0xa7b284 subreg_get_info(unsigned int, machine_mode, unsigned int,
machine_mode, subreg_info*)
        $SRC/gcc/rtlanal.c:3673
0xa7b52c simplify_subreg_regno(unsigned int, machine_mode, unsigned int,
machine_mode)
        $SRC/gcc/rtlanal.c:3808
0xa500cc simplifiable_subregs(subreg_shape const&)
        $SRC/gcc/reginfo.c:1234
0xa501b8 record_subregs_of_mode
        $SRC/gcc/reginfo.c:1295
0xa50434 init_subregs_of_mode()
        $SRC/gcc/reginfo.c:1349
0x947656 init_costs
        $SRC/gcc/ira-costs.c:2187
0x94c0a8 ira_set_pseudo_classes(bool, _IO_FILE*)
        $SRC/gcc/ira-costs.c:2237
0x1121695 alloc_global_sched_pressure_data
        $SRC/gcc/haifa-sched.c:7244
0x1121695 sched_init()
        $SRC/gcc/haifa-sched.c:7394
0x1122a13 haifa_sched_init()
        $SRC/gcc/haifa-sched.c:7406
0xa878f1 schedule_insns()
        $SRC/gcc/sched-rgn.c:3504
0xa880a1 rest_of_handle_sched
        $SRC/gcc/sched-rgn.c:3717
0xa880a1 execute
        $SRC/gcc/sched-rgn.c:3825
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.


Bisection shows it started with r236582 but that's a SLP vectorisation patch so
I suspect it's exposing a latent issue