On Thu, Feb 27, 2020 at 10:30:21AM +0100, Richard Biener wrote:
> Obviously I don't like the repetitive boiler-plate after
> the ranges_known_overlap_p checks so I wonder if we can at least
> factor those into a VN-local ranges_known_overlap_for_pd_p predicate.
I can do that.
> Wouldn't it be possible to simply constrain both sizes to half
> of the address space? Then the ranges_known_overlap_p should
> guarantee that we can represent the difference between the
> offsets in a signed HWI?
Well, it is already 1/8th of address space for 64-bit VA, so that would
be 1/16th then. Doing it in ranges_known_overlap_p might be too
restrictive, other places might handle those fine.
Perhaps we should also rule out the case when pd.offset would be minimum,
because we e.g. use -pd.offset, or when it or pd.size would be maximum
(as we e.g. use r->size + 1).
I'm also a little bit worried about possible overflows in
r->size = MAX (r->offset + r->size, newr.offset + newr.size) - r->offset;
or
r->size = MAX (r->offset + r->size,
rafter->offset + rafter->size) - r->offset;
While in ranges_known_overlap_for_pd_p we'd ensure that *->offset + *->size
doesn't overflow, the subtraction still could.
Jakub
