https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51492
--- Comment #12 from Tamar Christina <tnfchris at gcc dot gnu.org> --- (In reply to JuzheZhong from comment #11) > Hi, Tamar. > > We are interested in supporting saturating and rounding. Awesome! > > We may need to support scalar first. > > Do you have any suggestions ? > > Or you are already working on it? No, atm we're not, it's on the backlog but haven't gotten to it so feel free to do so. The general conclusion of the thread is that we should introduce new internal functions in the mid-end for this (also see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112600 for some other scalar examples). So e.g. we'd have IFN_SAT_ADD etc and new optabs. recognizing this on scalar you'll then automatically get autovect. What I would do is create non-direct-optab IFNs. as in, have a default fallback for architectures that don't have the optab implemented, and those that do use the optab. I think we should be able to do better here in general even for scalar if we know the operation is supposed to saturate like https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112600 shows. This also simplifies optimizations because every target then has the same GIMPLE representation for these operations. The only outstanding thing is where to do this. We obviously have to do so before vectorization but some of the saturation idioms require phi-opts https://godbolt.org/z/9oWP5vqee but others can't be done in phi-opts, those probably fit in match.pd or forwardprop. Any suggestions of where to best add the detection richi? > > Thanks.
