markus@x4 tsan % cat test.ii
struct {
  int trace[6];
} a;
void fn1() {
  for (int i; i; i++) {
    a.trace[i] = a.trace[-i];
    a.trace[-i] = 0;
  }
}

markus@x4 tsan % /var/tmp/gcc_build_dir/./gcc/xgcc -B/var/tmp/gcc_build_dir/./gcc -O3 test.ii
test.ii:3:3: warning: anonymous type with no linkage used to declare variable ‘<anonymous struct> a’ with linkage [enabled by default]
 } a;
   ^
test.ii: In function ‘void fn1()’:
test.ii:4:6: internal compiler error: tree check: expected integer_cst, have nop_expr in tree_int_cst_lt, at tree.c:7083
 void fn1() {
      ^
0xd1c3f4 tree_check_failed(tree_node const*, char const*, int, char const*, ...)
        ../../gcc/gcc/tree.c:9477
0xd1e354 tree_check
        ../../gcc/gcc/tree.h:2914
0xd1e354 tree_int_cst_lt(tree_node const*, tree_node const*)
        ../../gcc/gcc/tree.c:7083
0xd1e390 tree_int_cst_compare(tree_node const*, tree_node const*)
        ../../gcc/gcc/tree.c:7093
0x100228c comp_dr_addr_with_seg_len_pair
        ../../gcc/gcc/tree-vect-data-refs.c:2672
0x100af25 vec<dr_addr_with_seg_len_pair_t, va_heap, vl_embed>::qsort(int (*)(void const*, void const*))
        ../../gcc/gcc/vec.h:941
0x100af25 vec<dr_addr_with_seg_len_pair_t, va_heap, vl_ptr>::qsort(int (*)(void const*, void const*))
        ../../gcc/gcc/vec.h:1620
0x100af25 vect_prune_runtime_alias_test_list(_loop_vec_info*)
        ../../gcc/gcc/tree-vect-data-refs.c:2845
0xce76f2 vect_analyze_loop_2
        ../../gcc/gcc/tree-vect-loop.c:1716
0xce76f2 vect_analyze_loop(loop*)
        ../../gcc/gcc/tree-vect-loop.c:1807
0xcfdaff vectorize_loops()
        ../../gcc/gcc/tree-vectorizer.c:360
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.