On Tue, Feb 25, 2020 at 07:43:09PM -0600, Bill Schmidt wrote: > The reason that homogeneous aggregates matter (at least somewhat) is that > the ABI ^H^H^H^HAPI requires establishing a calling convention and a name- > mangling formula that includes the length of parameters and return values. > Since ELFv2 and ELFv1 do not have the same calling convention, and ELFv2 > has a superior one, we chose to use ELFv2's calling convention and make use > of homogeneous aggregates for return values in registers for the case of > vectorized sincos. > > Please look at the document to see the constraints we're under to fit into > the different OpenMP clauses and attributes. It seems to me that we can > only define this for both powerpc64 and powerpc64le by establishing two > different calling conventions, which provides two different vector length > calculations for the sincos return value, and therefore requires two > different function implementations with different mangled names. (Either > that, or we cripple vectorized sincos by requiring it to return values > through memory.)
I still don't see it. For all ABIs the length of the arguments and return value is the same, and homogeneous aggregates doesn't factor in at all; that is just a detail whether something is passed in registers or memory (as we have with many other ABIs as well, fwiw). So why make this part of the mangling rules? It is perfectly fine to design this with ELFv2 in mind, of course, but making a dependency on the (current!) (very complex!) ELFv2 rules for absolutely no reason at all is a mistake, in my opinion. Segher
