http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50294
--- Comment #6 from rguenther at suse dot de <rguenther at suse dot de> 2011-09-06 09:52:38 UTC --- On Tue, 6 Sep 2011, ebotcazou at gcc dot gnu.org wrote: > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50294 > > --- Comment #5 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2011-09-06 > 09:14:28 UTC --- > > My idea with fixing the Ada issue would be to conditionally use a signed > > or unsigned (sizetype) domain type. Not sure if all of the middle-end > > copes well with ssizetype domains (but well, we should fix it then). > > Yes, IIRC I tried something like that at some point. You also mentioned in an > earlier thread that you tried to make sizetype signed. What kind of problems > did you run into? This was the original setting of the Ada compiler, so the > middle-end was able to support it, at least until relatively recently. I run into various diagnostic issues in the C family frontends, so I quickly gave up. > > Of course that wouldn't fix use of an even larger domain type > > such as Unsigned_128_T is mod 2 ** 128 and appropriate large constants. > > But I see several special-cases in the Gigi code that tries to handle > > overflow situations. > > GNAT doesn't support integral types bigger than 64-bit anyway. And 32-bit for 32-bit targets? sizetype is 32bits there ... > > Thus, I think we ideally should allow any kind of integer type in > > TYPE_DOMAIN, not just sizetype variants. But that's of course an even > > bigger change. > > The signedness flip is already tricky... Yeah, I backed off when seeing the amount of code I'd need to change in GiGi ... esp. as I don't know the code well. > > Sidenote: my idea was to remove special-casings of TYPE_IS_SIZETYPE from > > folders but have a few special-cases explicit in size_binop so we know > > the definite context from which they are invoked (like from stor-layout). > > That's much better than to expose the special-casing from random > > optimization passes that happen to call into fold. > > OK, I see.
