This makes predictDelay be based on an arbitrary belpin pair rather
than a arc of a net based on cell placement. This way 'what-if'
decisions can be evaluated without actually changing placement;
potentially useful for parallel placement.
A new helper predictArcDelay behaves like the old predictDelay to
minimise the impact on existing passes; only arches need be updated.
Signed-off-by: gatecat <gatecat@ds0.me>
This replaces RelPtrs and a separate length field with a Rust-style
slice containing both a pointer and a length; with bounds checking
always enforced.
Thus iterating over these structures is both cleaner and safer.
Signed-off-by: D. Shah <dave@ds0.me>
