optabs.c (emit_cmp_insn): Abort if asked to emit non-canonical RTL for a target with HAVE_cc0 defined.

        * optabs.c (emit_cmp_insn): Abort if asked to emit non-canonical RTL
        for a target with HAVE_cc0 defined.
        (emit_cmp_and_jump_insns): New function.
        * expr.h (emit_cmp_and_jump_insns): Prototype it.
        * loop.c (check_dbra_loop): Use it to replace calls
        to emit_cmp_insn and emit_jump_insn and to canonicalise
        the comparison if necessary.
        * unroll.c (unroll_loop): Likewise.

From-SVN: r24471