On Sat, 18 Feb 2023, Jeff Law wrote: > > Barring the fusion case, which indeed asks for a dedicated `divmod' > > pattern (and then I suppose a post-reload splitter or a peephole so that > > where one of the two results produced has eventually turned out unused, we > > have means to discard the unneeded machine instruction), isn't the generic > > transformation something for the middle end to do based on RTX costs? > I originally though the same way you did Maciej. > > The problem is you don't see it as a divmod in expand_divmod unless you expose > a divmod optab. See tree-ssa-mathopts.cc's divmod handling.
That's the kind of stuff I'd expect to happen at the tree level though, before expand. Maciej
