[Bug middle-end/53676] [4.7/4.8 regression] empty loop is not always removed now

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53676

--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-25 
13:39:29 UTC ---
In SCEV analysis we'd need to detect the pattern feeding the truncation

  tem_3 = (int) result_2;
  tem_4 = tem_3 + 2;
  result_5 = (signed char) tem_4;

in interpret_rhs_expr - otherwise we ask for the evolution of tem_4 which
we cannot express properly because tem_3's chrec wraps.  So we'd need to
handle result_5 = (signed char) ((int) result_2 + 2) as if it were done
without the intermediate tem_4.