------- Comment #3 from rguenther at suse dot de 2006-11-06 12:04 -------
Subject: Re: Missed constant propagation into
loops
On Mon, 6 Nov 2006, rakdver at gcc dot gnu dot org wrote:
>
>
> ------- Comment #2 from rakdver at gcc dot gnu dot org 2006-11-06 11:51
> -------
> > Have you tried
> >
> > void foo (void);
> > void bar (void)
> > {
> > int i, j;
> > i = 0;
> > for (j = 0; j < 10000; j++)
> > if (i)
> > foo ();
> > }
>
> This would work, obviously.
>
> > For the original problem, why don't we propagate constants in
> >
> > # i_3 = V_MUST_DEF <i_2>;
> > i = 0;
> >
> > # NONLOCAL.6_19 = PHI <NONLOCAL.6_9(5), NONLOCAL.6_11(2)>;
> > # i_18 = PHI <i_7(5), i_3(2)>;
> >
> > i.e. replacing the use of i_3 with just the constant 0?
>
> Because i is a virtual operand, not real one.
But that doesn't help that i is loop-carried and so we don't
propagate it to the if () stmt - we use i_18 there. Or am I missing
something?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29738
