https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109587
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2023-04-24
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
The issue isn't unrolling but invariant motion. We unroll the innermost loop,
vectorizer the middle loop and then unroll that as well. That leaves us with
64 invariant loads from b[] in the outer loop which I think RTL opts never
"schedule back", even with -fsched-pressure.
Estimating register pressure on GIMPLE is hard and we heavily rely on
"optimistic" transforms with regard to things being optimized in followup
passes during the GIMPLE phase.
