On Thu, Jun 29, 2023 at 2:06 PM Krister Walfridsson <krister.walfrids...@gmail.com> wrote: > > On Thu, 29 Jun 2023, Richard Biener wrote: > > > The thing with signed bools is that the two relevant values are -1 (true) > > and 0 (false), those are used for vector bool components where we also > > need them to be of wider type (32bits in this case). > > My main confusion comes from seeing IR doing arithmetic such as > > <signed-boolean:32> _127; > <signed-boolean:32> _169; > ... > _169 = _127 + -1; > > or > > <signed-boolean:32> _127; > <signed-boolean:32> _169; > ... > _169 = -_127; > > and it was unclear to me what kind of arithmetic is allowed.
IIRC we have some simplification rules that turn bit operations into arithmetics. Arithmetic is allowed if it keeps the values inside [-1,0] for signed bools or [0, 1] for unsigned bools. > I have now verified that all cases seems to be just one operation of this > form (where _127 has the value 0 or 1), so it cannot construct values > such as 42. But the wide signed Boolean can have the three different > values 1, 0, and -1, which I still think is at least one too many. :) Yeah, I'd be interested in a testcase that shows this behavior. Richard. > I'll update my tool to complain if the value is outside the range [-1, 1]. > > /Krister
