fix gimplify_save_expr

[Jason Merrill]

On Sun, 22 Aug 2004 15:01:29 -0700, Richard Henderson <rth@redhat.com> wrote:

> As reported by Kenner,
>
>   http://gcc.gnu.org/ml/gcc/2004-08/msg00974.html
>
> I do think this method, with a bit on the save_expr itself, is
> the safest solution.  It doesn't matter whether the replacement
> is or isn't DECL_GIMPLE_FORMAL_TEMP_P, so long as we do the 
> substitution exactly once.

Why can't it just check for a non-volatile VAR_DECL?  I suggested that in
an earlier message about this stuff, but I guess that got lost.

Jason