On Wed, May 02, 2012 at 11:24:13AM +0200, Richard Guenther wrote: > > Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, > > ok for trunk/4.7? > > Ok.
Thanks.
> > BTW, tree-ssa-loop-prefetch.c seems to have the same problem, but no idea
> > how that should be handled in there...
>
> I think it handles it fine by treating the chrec_dont_know DDR
> properly? I suppose
> failing would be an option, too, by returning a bool from
> determine_loop_nest_reuse
> and adjusting its single caller.
IMHO it will just segfault (I don't have a testcase though).
compute_all_dependences (datarefs, &dependences, vloops, true);
FOR_EACH_VEC_ELT (ddr_p, dependences, i, dep)
{
if (DDR_ARE_DEPENDENT (dep) == chrec_known)
continue;
ref = (struct mem_ref *) DDR_A (dep)->aux;
refb = (struct mem_ref *) DDR_B (dep)->aux;
if (DDR_ARE_DEPENDENT (dep) == chrec_dont_know
|| DDR_NUM_DIST_VECTS (dep) == 0)
{
/* If the dependence cannot be analyzed, assume that there might
* be
a reuse. */
dist = 0;
ref->independent_p = false;
refb->independent_p = false;
}
If compute_all_dependences above fails (returns false), then dependences
vector will contain just single chrec_dont_know element, but with DDR_A
(dep) == DDR_B (dep) == NULL. So the above will try to dereference both and
ICE before checking chrec_dont_know (and even if it wouldn't, there is
nothing to mark independent_p = false - supposedly everything should be
no longer independent_p).
Jakub
