> The vsevl pass is LCM based. So it's not allowed to add a vsetvl on a > path that didn't have a vsetvl before. Consider this simple graph. > > 0 > / \ > 2-->3 > > If we have need for a vsetvl in bb2, but not bb0 or bb3, then the vsetvl > will land in bb4. bb0 is not a valid insertion point for the vsetvl > pass because the path 0->3 doesn't strictly need a vsetvl. That's > inherent in the LCM algorithm (anticipatable).
Yeah, I remember the same issue with the rounding-mode setter placement. Wouldn't that be fixable by requiring a dummy/wildcard/dontcare vsetvl in bb3 (or any other block that doesn't require one)? Such a dummy vsetvl would be fusible with every other vsetvl. If there are dummy vsetvls remaining after LCM just delete them? Just thinking out loud, the devil will be in the details. -- Regards Robin
