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

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

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

--- Comment #8 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-27 11:32:34 UTC ---
Author: rguenth
Date: Wed Jun 27 11:32:30 2012
New Revision: 189013

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189013
Log:
2012-06-27  Richard Guenther  <rguenther@suse.de>

    PR middle-end/53676
    * tree-chrec.c (chrec_convert_1): Represent truncation to
    a type with undefined overflow as truncation to an unsigned
    type converted to the type with undefined overflow.
    * tree-scalar-evolution.c (interpret_rhs_expr): For computing
    the scalar evolution of a truncated widened operation avoid
    looking at the non-existing evolution of the widened operation
    result.

    * gcc.dg/tree-ssa/scev-6.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/scev-6.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-chrec.c
    trunk/gcc/tree-scalar-evolution.c