[Bug rtl-optimization/81290] New: [8 Regression] ICE in update_br_prob_note

["asolokha at gmx dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81290

            Bug ID: 81290
           Summary: [8 Regression] ICE in update_br_prob_note
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

gcc-8.0.0-alpha20170702 snapshot ICEs when compiling the following snippet w/
-O2 -funroll-loops:

int vz;

void
ms (int sw, int cm)
{
  for (vz = 0; vz < 19; ++vz)
    {
 fx:
      sw *= 2;
    }

  for (;;)
    {
      if (sw != 0)
        for (;;)
          {
          }
      if (1 / 0 && cm != 0)
        goto fx;
    }
}

% gcc-8.0.0-alpha20170702 -O2 -funroll-loops -c -w vev3ezql.c                   
during RTL pass: loop2_unroll
vev3ezql.c: In function 'ms':
vev3ezql.c:21:1: internal compiler error: Segmentation fault
 }
 ^

(gdb) where
#0  0x000000000088fc37 in update_br_prob_note(basic_block_def*) ()
#1  0x0000000000bc2cb9 in force_edge_cold(edge_def*, bool) ()
#2  0x0000000000bc2c6e in force_edge_cold(edge_def*, bool) ()
#3  0x0000000000bc2c6e in force_edge_cold(edge_def*, bool) ()
#4  0x0000000000889800 in duplicate_loop_to_header_edge(loop*, edge_def*,
unsigned int, simple_bitmap_def*, edge_def*, vec<edge_def*, va_heap, vl_ptr>*,
int) ()
#5  0x0000000000b0a747 in unroll_loops(int) ()
#6  0x0000000000af92a0 in (anonymous
namespace)::pass_rtl_unroll_loops::execute(function*) ()
#7  0x0000000000bac04a in execute_one_pass(opt_pass*) ()
#8  0x0000000000bac8f4 in execute_pass_list_1(opt_pass*) ()
#9  0x0000000000bac915 in execute_pass_list_1(opt_pass*) ()
#10 0x0000000000bac915 in execute_pass_list_1(opt_pass*) ()
#11 0x0000000000bac939 in execute_pass_list(function*, opt_pass*) ()
#12 0x00000000008ac7c0 in cgraph_node::expand() ()
#13 0x00000000008adb91 in symbol_table::compile() [clone .part.54] ()
#14 0x00000000008afecd in symbol_table::finalize_compilation_unit() ()
#15 0x0000000000c87e88 in compile_file() ()
#16 0x000000000072f5c7 in toplev::main(int, char**) ()
#17 0x000000000073155b in main ()

Maybe related to the recent REG_BR_PROB fallout?