[Bug c/88031] New: ice in vectorizable_reduction, at tree-vect-loop.c:6953

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88031

            Bug ID: 88031
           Summary: ice in vectorizable_reduction, at
                    tree-vect-loop.c:6953
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

For this C code:

int a[512];
int b;
void d() {
  unsigned char c;
  for (; b; b++) {
    c = 1;
    for (; c; c <<= 1) {
      a[b] <<= 8;
      if (b & c)
        a[b] = 1;
    }
  }
}

compiled with recent gcc trunk and compiler flag -O3, does this:

bug478.c:3:6: internal compiler error: in vectorizable_reduction, at
tree-vect-loop.c:6953
    3 | void d() {
      |      ^
0x2d4e1ee vectorizable_reduction(_stmt_vec_info*, gimple_stmt_iterator*,
_stmt_vec_info**, _slp_tree*, _slp_instance*, vec<stmt_info_for_cost, va_heap,
vl_ptr>*)
        ../../trunk/gcc/tree-vect-loop.c:6953

gcc was fine at revision 265907, but had gone wrong by 265980