https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81434
Wilco <wilco at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |wilco at gcc dot gnu.org --- Comment #4 from Wilco <wilco at gcc dot gnu.org> --- To more accurately schedule fusion pairs wouldn't we need to specify the scheduling behaviour of the group as well? From the dumps below it schedules the adrp/add in the same cycle if we're lucky, but it is modelled as using 2 ALUs rather than a new single fused instruction. Also is your change fixing the issue that the scheduler cannot schedule 2 instructions with a zero latency dependency between them in the same cycle? That's a very similar bug.