https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103641
--- Comment #24 from Richard Biener <rguenth at gcc dot gnu.org> --- Another note, a quick look at synth_mult shows that it should support vector modes just fine but we are passing it the scalar mode. We do know the vector type that's going to be used so we should better pass down its mode I think, given vector shifts might not even be supported (and thus they hopefully will have prohibitive costs).
