On Wed, 10 Oct 2012, Jakub Jelinek wrote:
> On Wed, Oct 10, 2012 at 10:21:59AM +0200, Richard Biener wrote:
> > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
> >
> > Err, why? Can't we negate a constant, too?
>
> Not all of them, say INT_MIN can't be negated.
> Though,
> int
> foo (int n)
> {
> int i, d;
> for (i = 0, d = 0; i < n; i++)
> d -= -__INT_MAX__ - 1;
> return d;
> }
> doesn't trigger it. And for constants I thought it would be better to
> just fold it immediately.
Yeah, I meant we can negate all constants by doing
tem = - CONSTANT;
right? Or wait ... even if we have
red = x - y;
if y is INT_MIN then the code we just created may have introduced
undefined overflow (of course you could argue that with x - y it
is very likely that undefined overflow already happened) ...
> > The ICE simply means
> > we should have used make_temp_ssa_name (TREE_TYPE (rhs), NULL, NULL)
> > instead of copy_ssa_name.
>
> Is make_temp_ssa_name (TREE_TYPE (rhs), NULL, NULL) preferrable over just
> make_ssa_name (TREE_TYPE (rhs), NULL); ?
Ah, no, make_ssa_name (TREE_TYPE (rhs), NULL) is even better. On
the 4.7 branch you need to create a new temp var ...
Richard.
